Distribution, contribution and regulation of nestin⁺ cells

Graphical abstract

Highlights

• •This review summarized and discussed current studies on the distribution, contribution and regulation of nestin⁺ cells in different systems of the body.
• •This review highlighted the potential of nestin as a marker of multilineage stem/progenitor cells, and recommended nestin as a key factor in tissue development and tissue regeneration.
• •The article discussed the current findings, limitations, and potential clinical implications or applications of nestin⁺ cells. Additionally, it included the relationship of nestin⁺ cells to other cell populations.

Abstract

Background

Nestin is an intermediate filament first reported in neuroepithelial stem cells. Nestin expression could be found in a variety of tissues throughout all systems of the body, especially during tissue development and tissue regeneration processes.

Aim of Review

This review aimed to summarize and discuss current studies on the distribution, contribution and regulation of nestin⁺ cells in different systems of the body, to discuss the feasibility of using nestin as a marker of multilineage stem/progenitor cells, and better understand the potential roles of nestin⁺ cells in tissue development, regeneration and pathological processes.

Key Scientific Concepts of Review

This review highlights the potential of nestin as a marker of multilineage stem/progenitor cells, and as a key factor in tissue development and tissue regeneration. The article discussed the current findings, limitations, and potential clinical implications or applications of nestin⁺ cells. Additionally, it included the relationship of nestin⁺ cells to other cell populations. We propose potential future research directions to encourage further investigation in the field.

Overview of nestin

Nestin is a type VI intermediate filament (IF) that was initially thought to be specifically expressed in neuroepithelial stem cells according to a preliminary study in the late 20th century [1], [2]. In addition to the neural system, nestin expression can be found in migrating, proliferating and regenerating cells in various human body systems, including a variety of tissues including brain [3], spinal cord [4], bone marrow [5], muscle [6], tendon [7], heart [8], lung [9], gastrointestinal tract [10], kidney [11] and so on. The nestin gene contains three introns and four exons (Fig. 1A); the first intron regulates IF proteins in developing skeletal muscle, C2C12 myoblasts and endothelial cells containing a specific enhancer for myogenic precursors, and the second intron selectively directs nestin expression in the central nervous system (CNS) because it contains a CNS-specific enhancer [12], [13].

Fig. 1.

The structure of human nestin.

As is typical for IF proteins, nestin shares a common structure with other IF chains—the highly conserved central rod domain (Fig. 1B), and the central domain forms the central rod coiled domain together with another compatible chain [14]. Polymerized IF and end domains can be assembled onto the central rod coiled domain, and IFs have various binding and regulatory domains due to the variable sizes and chemistries of end domains [15]. The N-terminus of the nestin protein is short, and the C-terminus is unusually long. Because the N-terminus necessary for IF assembly is not long enough, nestin cannot self-assemble without the help of other IFs, such as vimentin [2]. The unique features of nestin remain unclear because the genetic structure and protein sequence of nestin are similar to those of type III and especially type IV Ifs [14]. However, because of the characteristic core domain, the presence of a third intron, the short head domain and the unconventionally long C-terminal end, nestin is regarded as a separate type VI IF [2].

Nestin was first discovered in 1985 by the monoclonal antibody Rat-401 in the embryonic rat CNS, but no nestin expression was found in adulthood [16]. In fact, nestin expression in cells is sometimes lifelong and sometimes only occurs during development or injury repair or in malignant tumours. Here, we collectively refer to nestin-expressing cells as nestin⁺ cells. Nestin⁺ cells have been reported to function in tissue development and injury repair in multiple systems of the body, as well as in cancer progression, being controlled by specific regulatory actions. Therefore, nestin may play a vital role in cell function and fate, and the following section of this review will elaborate on nestin⁺ cell function and regulation in each system in detail.

Nestin⁺ cells in the neural system

Nestin is a marker of neural stem/progenitor cells

Nestin has been widely used as a marker gene to identify neural stem/progenitor cells (NSPCs) [17], [18], [19], [20]. Neuroectodermal cells start to express nestin when neurulation begins, and during embryonic development, nestin expression can be found in CNS regions with proliferating cells, the rostral and caudal neural tubes, the developing cerebellum and the telencephalon at specific stages, whereas in adult tissues, nestin expression is mainly restricted to areas of regeneration [2], [15]. The expression of nestin gradually decreases as NSPCs differentiate into neurons, astrocytes, and oligodendrocytes [21]. Neurofilaments and glial fibrillary acidic proteins (GFAPs) located in neurons and glial cells, respectively, gradually replace nestin [21]. As shown in a single-cell RNA sequencing experiment, nestin mRNA persisted 24–48 h after division in some groups of new neurons [22].

Nestin maintains the biological activity of NSPCs

It has been proven that NSPC migration depends on nestin expression, as does astrocyte and astrocytoma cell migration [3], [23], [24]. In addition, nestin functions as a modulator of IF structure during mitosis, as it can induce the disassembly of vimentin IFs during mitosis [25], [26], [27]. However, because nestin is not necessary for formation of IFs such as vimentin and GFAP, nestin-deficient cell showed a well-developed IF network and unaffected proliferation but slower migration [3], [24]. Nestin expression is also associated with the apoptosis of NSPCs. The overexpression of nestin can effectively inhibit the apoptosis induced by cyclin-dependent kinase 5 (Cdk5) under the effect of oxidizers, indicating that nestin is one of the key survival determinants of NSPCs [28]. Moreover, the nestin-Cdk5-dynamin-related protein 1 (Drp1) axis negatively regulates mitochondrial oxidative phosphorylation in NSPCs, suggesting that nestin is indispensable for the maintenance of NSPC stemness [29].

During neural system development, the role of nestin remains unclear. The main characteristic of neural system development is the alternative expression of different IFs, such as vimentin, nestin, peripherin and α-internexin [15]. The difference in nestin expression between NSPCs and mature cells makes nestin a good marker for studying the behaviour of NSPCs and the development of the neural system. To better understand the role of nestin in cells, nestin knockout models are often used in related studies. In behavioural studies, nestin-deficient mice exhibited impaired long-term memory but normal associative learning; therefore, it is conceivable that nestin may regulate neural plasticity or function in some aspects [24]. According to Park et al., nestin knockout mice showed embryonic lethality and less NSPCs, thus nestin is important for the survival and self-renewal of NSPCs [30]; however, Mohseni et al. found that nestin deficiency did not cause embryonic lethality, therefore they concluded that nestin is not necessary for CNS development [31]. This contradictory result may have been caused by the use of different nestin knockout mice in different studies, so the proper use of in vivo models is of great importance [26].

Nestin affects cell–cell communication, migration and injury react of astrocytes

In the adult brain, astrocytes act as NSPCs within specific niches. Astrocytes are activated in various neurological diseases, and the activation of astrocytes upregulates various IF proteins, such as nestin, vimentin, GFAPs and synemin [32]. Besides, nestin is expressed by radial glial cells, which are important for new neurons migration support [33]. When radial glial processes were impaired, nestin expression was reduced, suggesting that nestin may serve as an indicator of glial cells evaluation [33]. In astrocytes, nestin has multiple effects on glial cells. For example, nestin can affect vesicle interactions, trafficking, vesicle fusion pore geometry and kinetics, hence, nestin may affect cell communication between astrocytes and other cell types[34]. In collective astrocyte migration, nestin assembles with other IFs in the cytoplasm to limit traction forces and sustain cell–cell contacts[35]. During ischaemic injury, nestin is associated with the transformation of reactive astrocytes into neurons[36], multilineage cell generation in the subventricular zone and neurogenesis[37], [38], which indicates that nestin may be a noteworthy marker of ischaemic injury in the neural system.

Nestin⁺ cells contribute to spinal cord injury repair

In spinal cord, long radial nestin⁺ cells and subpopulations of ependymal nestin⁺ cells have been observed in the dorsal and ventral regions. Recently, nestin⁺ NSPCs outside but not inside the central canal were identified as a subgroup that could be activated after SCI by single-cell RNA sequencing, deepening the understanding of nestin⁺ NSPC distribution [36], [39]. Spinal cord NSPCs are pivotal to spinal cord injury (SCI) repair, and nestin is commonly used as an indicator of NSPC stemness and nerve regeneration during SCI repair [39], [40], [41], [42]. Besides, nestin has also been used in stem cell therapy and organotypic neurosphere evaluation, further supporting nestin as an important marker in spinal cord repair and development [43], [44]. After SCI, nestin⁺ cells are activated and aggregate at the injury site, and they are positively correlated with locomotor recovery [4], [45]. These nestin⁺ cells have the ability to differentiate into multiple neural lineage cells ex vivo, such as neurons, astrocytes, and oligodendrocytes, indicating that they function as NSPCs [46]. Furthermore, nestin expression is increased in both cerebral and spinal cord ischaemic injury, and nestin⁺ cells are associated with the vascular system and may contribute to the structural remodelling of perivascular cells [47], [48]. Nerve cells and immune cells are believed to have a vital influence on the inflammatory microenvironment after SCI; for example, microglia/macrophages can interact with nestin⁺ NSPCs and affect neurogenesis, suggesting endogenous nestin⁺ NSPC neurogenesis depends on the suitability of their microenvironment, which may provide a promising strategy for nestin regulation [4], [49].

In addition, the ependyma of the central canal is thought to contain a pool of endogenous stem cells for repair strategies [45]. After traumatic CNS injury, the number of nestin⁺ ependymal cells significantly increased, and their percentage was positively correlated with postinjury survival time [50]. However, lineage tracing revealed that the nestin⁺ cells in the lesion core and edge area after complete transected SCI had various derivation and seldom from ependymal cells; therefore, the role of nestin⁺ ependymal cells requires further exploration [51]. Apart from the injury site, nestin expression can be found in all levels of the spinal cord; therefore, the reactivity of nestin is not restricted [50], [52]. In general, nestin may be an important marker of endogenous NSPCs during spinal cord repair. Future studies may focus on the mechanism by which nestin⁺ cells become activated and participate in repair to increase the understanding of nestin⁺ NSPC regulation.

Regulation of nestin⁺ cells in the neural system

During neurogenesis, neuronal differentiation and survival are regulated by nestin through Notch signalling in mice [24]. In addition, Cdk5 may be closely associated with the function of nestin in the nervous system. The cellular basis of neural connectivity is synapses, and research has shown that in acetylcholine (ACh)-induced dispersion of ACh receptor clusters, nestin negatively regulates postsynaptic differentiation through a Cdk5-mediated mechanism. Therefore, nestin may contribute to synapse formation [53]. Nestin plays a vital role in oxidant-induced Cdk5-dependent apoptosis because nestin acts as a scaffold for Cdk5, and it can influence Cdk5/p35 signalling complex assembly, stability, and activity [28]. Furthermore, in developing neurons, nestin regulates growth cone morphology via Cdk5/p35 signalling, suggesting that regulation of the intracellular kinase signalling environment by nestin can change the behaviour of growth cones [54]. During NSPC migration, nestin may increase cell motility by increasing myosin light chain kinase (MLCK) activity through direct binding to control the cell contractility, indicating that nestin exhibits a close relationship with NSPC contraction, migration and motility [3] In addition, nestin⁺ cells play a pivotal role in neural system injury repair. For example, after fish cerebellar injury, nestin is re-expressed by NSPCs in the neurogenic niche and adjacent areas and has neurotrophic and neurogenic effects [55]. To better summarize the contribution and regulartory mechanisms of nestin⁺ cells in nerve development and injury repair, we concluded relevant studies in Table 1.

Table 1.

The contributions and regulations of nestin⁺ cells in neural system.

Event	Nestin expression	Contribution	Regulation	Reference
Neurogenesis	Nestin-deficient mice	Nestin regulated neurogenesis from astrocytes to NSPCs	Notch signaling pathway	[24]
Synapse formation	E18.5 hind limb muscle, C2C12 myotubes	Nestin participated in dispersion of AChR clusters induced by Ach	Cdk5-mediated mechanism	[53]
Remyelination	Neural stem cells (NSCs)	Nestin+ NSCs-derived oligodendrocytes and parenchymal oligodendrocyte progenitor cells competed to repair demyelinating lesions.	Sonic hedgehog (Shh) signaling	[188]
Oxidant-induced cell death	Neuronal precursor cells	Nestin served as a scaffold for Cdk5 and displayed a distinct cytoprotective effect	Cdk5/p35 signaling	[28]
Neuron development	Cortical neurons	Nestin contributed to regulation of growth cone morphology and Semaphorin 3A(Sema3a) sensitivity		[54]
Neural stem cells’ migration	Neural stem cells	Nestin regulated cell migration by cell contractility control	Nestin interacts with myosin light chain kinase (MLCK)	[3]
Cerebellum traumatic injury	Neural stem cells	Nestin+ cells exhibited neurotrophic and proneurogenic effects	–	[55]
Spinal cord injury	Neural progenitors	The proliferation, migration, and neurogenesis of nestin+ cells increased after traumatic compression	–	[189]
Focal cerebral ischemia	Reactive astrocytes, vasculature-associated cells	Nestin facilitated cellular structural remodeling	–	[47]
	Neuroblasts, oligodendrocyte progenitors, astrocytes, postmitotic neurons	Nestin+ NSPCs mount a multilineage response to stroke	–	[37]
Spinal cord ischemic injury	Ependyma cell, reactive astrocytes, vessels	Nestin+ cells were beneficial for ischemic tolerance	–	[48]
Transient focal ischemic brain injury	Glial fibrillary acidic protein(GFAP) positive cells, reactive astrocytes, neural stem cells	Nestin was involved in the transdifferentiation of astrocytes into neurons	Neurogenic effect of VEGF	[36]
Acute ischemic stroke	NSPCs	Nestin expression was related to the amelioration of astrogliosis and microgliosis, augmentation of neural progenitor cell proliferation	The aryl hydrocarbon receptor (AHR) activation	[38]
Medulloblastoma	Medulloblastoma cells, cerebellar granule neuron precursor cells	Nestin binded Gli3 to mediate the development of medulloblastomas	Hedgehog signaling pathway	[190]
	Astrocytes	Astrocytes induced nestin expression to promote Medulloblastoma progression		[191]
	Cancer stem cells	Nestin+ cells exhibited radioresistance	The activation of the AKT/PI3K and p53 signaling pathways	[56]
		Proliferation of nestin+ cells was improved	AKT signaling pathway
	Progenitor cells	Nestin+ cells formed tumors	The loss of PTEN gene and Sonic hedgehog overexpression
Glioma	Glioblastoma cells	Nestin regulated stemness, cell growth, and invasion in glioblastoma cells	The alteration of post-translational modification of heat shock protein HSPA8/HSC71	[192]
		Nestin promoted cell-cycle progress and spindle assembly of tumor cells	Interaction with βII-tubulin	[193]
		Blockade of a laminin411-notch axis inhibited nestin expression	Laminin411-Notch Axis	[194]
	Glioma-initiating cells	Nestin expression enhanced cell sensitivity to Ca2+	Ca2+ signaling pathway	[56]
	Progenitor cells, glioma cells	Notch activated nestin expression in progenitor cells or glioma cells	Notch signaling pathway	[195]

Nestin serves as a tumor marker in the neural system

Nestin has been widely reported as a CNS tumour marker. Nestin expression has been identified in multiple tumours of neuroectodermal neuroepithelial origin, including astrocytic, oligodendroglial, oligoastrocytic, ependymal, embryonic, neuronal, and mixed neuronal-glial origin tumours [56], [57]. For example, during medulloblastoma (MB), sonic hedgehog signalling augmented by nestin⁺ tumour cells contributes to MB tumorigenesis, suggesting that nestin expression contributes to MB formation [58]. In addition, nestin may be associated with glioma clinicopathological factors and prognosis [59]. The relevant studies exploring different cells in MB and glioma which express nestin have been summarized (Table 1). According to this studies, nestin may be an indicator of tumour progression and prognosis in these high-incidence malignant tumours.

Nestin⁺ cells in the musculoskeletal system

Nestin⁺ cells contribute to stem cell niche maintenance in bone marrow

In the musculoskeletal system, nestin expression can be found in bone, bone marrow and skeletal muscle. Bone marrow is another major organ in which nestin⁺ cells reside. Nestin⁺ cells are important for stabilizing the niche of haematopoietic stem cells (HSCs). Abundant and specific nestin expression was identified in mesenchymal stem cells (MSCs), and nestin⁺ MSCs are closely related to HSC quiescence and maintenance in bone marrow [5], [60]. In the perivascular area, two types of HSC niche cells expressing nestin were found in mice (Nes-GFP^bright cells near arterioles and Nes-GFP^dim cells around sinusoids), both of which showed MSC activity [61]. These nestin⁺ vasculature-associated cells belong to a heterogeneous cell population containing endothelial and osteogenic progenitor cells. In bone marrow, nestin-labelled lineage cells were found to differentiate into osteoblasts, chondrocytes, and endothelial cells, which are essential for bone remodelling and injury repair [62], [63]. By secreting key molecules associated with HSC maintenance, such as the cytokines chemokine ligand 12 (CXCL12), stem cell factor (SCF) and kit ligand (Kitl), nestin⁺ cells can help to build the HSC niche in postnatal bone marrow [64], [65], [66], [67] (Fig. 2A).

Fig. 2.

Nestin expression in musculoskeletal system and circulatory system.

In bone marrow, the function and behaviour of nestin⁺ cells are related to neural, vascular and immune regulation and malignant tumorigenesis processes. The HSC niche built by nestin⁺ cells is regulated by sympathetic nerve fibres and via β3-adrenergic receptors in nestin⁺ cells, suggesting that the nestin⁺ cell niche is regulated by remote signals from the brain [67]. In addition, nestin⁺ cells may be a resource for endothelial cells, pericytes and stromal cells, and nestin expression can be found within the endosteal capillary network of bone marrow, indicating that nestin may correlate with vascular maintenance [64], [68]. The apoptosis of nestin⁺ cells may cause alteration of CXCL12 expression in bone marrow immune thrombocytopenia, causing impaired megakaryocyte maturation [69]. In addition, the nestin⁺ cell niche can be affected by diseases; for instance, during acute myelogenous leukaemia development, the quiescence of nestin⁺ niche cells is disrupted [70]. In turn, nestin⁺ cells influence pathological disease processes. In vivo, depleting nestin⁺ cells or CXCL12 produced by nestin⁺ cells leads to mutant HSC expansion and accelerated myeloproliferative neoplasm progression [67]. In breast cancer, it has been reported that nestin⁺ cells can instruct disseminated tumour cells to enter dormancy in the bone marrow microenvironment by producing TGFβ2 and BMP7 [71]. Moreover, nestin⁺ cells can differentiate into osteoblasts, osteocytes, and chondrocytes, which are osteoblast lineages that contribute to bone formation during embryonic endochondral ossification [64]. Based on the above evidence, nestin⁺ cells in bone marrow represent a group of multipotential stem cells that are essential for HSC homeostasis, and the stability of the nestin⁺ niche is associated with the regulation of the microenvironment.

Nestin⁺ cells contribute to musculoskeletal development and regeneration

The nestin protein is transiently expressed during skeletal muscle development, and nestin is coexpressed with desmin and vimentin in undifferentiated myoblasts. After differentiation into multinuclear myotubes, these proteins together form indistinguishable cytoplasmic filament networks [72]. Nestin expression was found in the early limb bud during muscle development and persisted until birth [73]. Furthermore, nestin expression was found to be upregulated upon initiation of tenogenesis and at specific stages of differentiation, and nestin expression can be found in myotendinous junctions and perivascular cells within tendons [7], [74]. Nestin is crucial for fate decisions and phenotype maintenance in tendon stem cells, and nestin was upregulated in tendon stem cells isolated from human Achilles when compared to mature tenocytes [7], [75]. Nestin expression has also been identified in skeletal muscle neuromuscular junctions, as well as in various cell types, such as pericytes, satellite cells, myoblasts and muscle interstitial progenitor cells, and these nestin⁺ cells have myogenic potency and may possess mesenchymal plasticity [6], [76] (Fig. 2B).

In terms of cartilage regeneration, following cartilage injury, nestin-GFP^bright perivascular cells can recruit specific MSCs to repair cartilage [77]. During muscle healing, nestin is highly expressed by myoblasts and newly formed myotubes, and knockout of nestin leads to delayed muscle regeneration [73]. Furthermore, it is assumed that a Cdk5-dependent mechanism is involved in nestin⁺ myoblast differentiation, and the balance between protein kinase C-ζ and Cdk5 is important for nestin reorganization and proper myogenic differentiation [15], [78]. After tendon injury, the number of nestin⁺ stem cells increases significantly during the reparative/proliferation stage, and these cells participate in endogenous injury repair, which is essential for tendon regeneration [7]. Therefore, nestin plays a pivotal role in the regeneration of the musculoskeletal system, and nestin⁺ cells may represent a group of endogenous stem cells that respond to musculoskeletal injury at specific phases.

Nestin⁺ cells in the circulatory system

Nestin⁺ cells contribute to cardiovascular development and regeneration

Resident cardiac nestin⁺ stem cells come from the embryonic neural crest in the heart, and these nestin⁺ stem cells can differentiate into neural crest-derived cells and diverse cardiac cell types, including cardiomyocytes, during postnatal development and ischaemic damage [8], [79], [80]. Expression of nestin is part of the cardiac embryonic phenotype, and nestin is responsible for cardiomyocyte cell cycle re-entry [13], [81]. During ischaemic injury, nestin⁺ cells migrate to the infarction area to help with blood vessel remodelling and neural fibre synthesis [82], [83], [84], [85] (Fig. 2C). It is believed that the p38 MAPK pathway is correlated with de novo nestin synthesis and the activation of pre-existing nestin⁺ cells [81], [86]. In addition to cardiac resident nestin⁺ cells, nestin expression can be found in new vascular endothelial cells and smooth muscle cells, and these cells contribute to angiogenesis [84]. In peri-infarct/infarct regions, nestin⁺ cells can acquire neuronal-like characteristics to promote neurofilament-M remodelling, and nestin is expressed by reactive astrocytes isolated from the infarct region [82], [87]. In addition, nestin⁺ myofibroblasts can be found during myocardial infarction repair even though ventricular fibroblasts lose nestin expression after birth [88]. Myofibroblasts usually lead to fibrosis, therefore nestin is considered to be involved in scar formation during repair [89], [90]. Lately, Hertig et al. further identified that nestin represented a marker of embryonic Tcf21/WT1((+))-fibroblast progenitor cells, which was a subpopulation of ventricular myofibroblasts [91]. Thus, nestin may preferentially promote ventricular fibroblast migration during physiological/pathological remodeling [91]. Moreover, nestin⁺ stem cells can differentiate into endothelial cells, smooth muscle cells and cardiomyocytes in dystrophic hearts, showing the ability to prevent the onset of dilated cardiomyopathy [92]. In conclusion, nestin⁺ cells participate in cardiovascular development and remodelling by participating in cell formation, angiogenesis and neurogenesis.

Nestin⁺ cells in the respiratory system

Nestin⁺ stem cells contribute to lung formation and remodelling

Nestin is involved in embryonic lung development. The expression of nestin has been discovered in fetal lung-derived fibroblasts, the respiratory cavity, the microvascular walls, and interstitial areas [9] (Fig. 3A). Furthermore, nestin is involved in alveolar septation and is cooperatively regulated by neuropilin-1 and platelet-derived growth factor receptors [93]. In adults, nestin⁺ cells show MSC characteristics, and nestin⁺ cells can generate various types of lung tissue, indicating that nestin may be related to lung renewal and maintenance of homeostasis [9]. Besides, nestin was proved to be important for smooth muscle contractility, as it could regulate actin cytoskeletal signaling via Plk1 in airway smooth muscle [94].

Fig. 3.

Nestin expression in respiratory system and digestive system.

In respiratory diseases, nestin is regarded as a marker of lung remodelling, and it is expressed in lung fibroblasts during reactive and reparative fibrosis [95], [96]. Specifically, during idiopathic pulmonary fibrosis, nestin facilitates the recycling of transcriptional growth factor (TGF)-β receptor I to regulate the vesicular trafficking system and thus promotes fibrosis progression [97]. Therefore, targeting nestin may be a promising therapeutic strategy for pulmonary fibrosis [97]. In asthmatic disease, nestin was discovered to be invloved in airway smooth muscle cell hyperplasia and airway wall thickening, which may lead to airway hyperresponsiveness and narrowing [98]. Morever, nestin⁺ MSCs have dual potential to differentiate into fibroblasts that generate fibrosis and into epithelial cells involved in remodelling. And Ras homologue family member A (RhoA)/Rho-associated protein kinase 1 (ROCK) signalling is believed to play a vital role in nestin⁺ MSC lineage fate determination [99]. In addition, during pulmonary vascular remodelling in pulmonary hypertension, nestin facilitates the transformation, proliferation and migration of related cells by increasing Wnt/β-catenin signalling pathway activity [96] (Table 2).

Table 2.

The contributions and regulations of nestin⁺ cells in respiratory system.

Event	Nestin+ cells	Contribution	Regulation	Reference
Alveolar septation	Mesenchymal cells (MSCs)	Nestin was involved in mesenchymal cell migration	Regulated by Neuropilin-1 and PDGF receptors	[93]
Remodeling of the airway	MSCs	MSCs differentiaed into airway epithelial cells	RhoA/ROCK signaling	[99]
Pulmonary vascular remodeling	Pulmonary artery smooth muscle cells	Nestin promoted the cell transformation, cell proliferation and cell migration	Wnt/β-catenin signaling pathway	[96]
Nasopharyngeal carcinoma (NPC)	NPC cells	Nestin can promote proliferation, survival and tumorigenesis	DNA damage response	[100]
Small cell lung cancer (SCLC)	SCLC cells	Hedgehog(Hh) signalling maintained nestin phenotype in SCLC cells	Hh signalling	[101]
		Nestin expression influenced chemotherapy resistance and clinical outcomes	–	[102]
		Nestin+ cells had neuroendocrine features and participate in malignant phenotypes	–	[103]
Non-small cell lung cancer (NSCLC)	NSCLC cell lines	Nestin contributed to cellular redox homeostasis regulation in NSCLC	Keap1-Nrf2 feedback loop	[104]
	Cancer stem-like cell populations	NF-κB and MYC signaling inhibition affected cell survival	NF-κB and MYC signaling pathway	[105]
Lung adenocarcinoma (AD)	AD cells	Nestin downregulation declined proliferation, migration and invasion of AD cells	Akt/SRY-box containing protein 2 (Sox2) signaling pathway	[106]

The function of nestin⁺ stem cells in respiratory cancer

Nestin expression is generally related to tumour cell differentiation, proliferation, invasion and angiogenesis in lung cancer [9]. In nasopharyngeal carcinoma (NPC), nestin can promote the proliferation, survival and tumorigenesis of NPC cells by participating in the DNA damage response [100]. In small cell lung cancer (SCLC), nestin is correlated with neuroendocrine characteristics and malignant phenotypes of tumours and is associated with prognosis of patients; therefore, nestin has the potential to be a new treatment target for SCLC [101], [102], [103]. In non-small cell lung cancer (NSCLC), oxidative damage of cells can be prevented by nestin, and nestin expression was identified in cancer stem cell-like cells; hence, nestin may influence tumour growth and invasion [104], [105]. In addition, in lung adenocarcinoma (AD), nestin is associated with AD cell proliferation, migration and invasion [106]. Overall, in respiratory cancer, targeting nestin may be a promising approach to inhibit tumour development, and the related regulatory mechanisms of nestin⁺ cells are summarized below (Table 2).

Nestin⁺ cells in the digestive system

High expression of nestin in the gastrointestinal tract

It has been reported that enteric neural precursor cells, neuronal cells and glial cells in the enteric nervous system express nestin, and stem/progenitor cells expressing nestin can differentiate into glial cells and neurons ex vivo, but whether nestin is a stem cell marker in the enteric nervous system remains unclear [10], [107], [108]. Nestin⁺ cell proliferation and neuronal differentiation are regulated by intestinal microbes via the intestinal serotonin network, and differentiation of nestin⁺ enteric neural precursor cells is induced by intestinal microbes via Toll-like receptor 2 (TLR2) [107], [108]. This evidence indicates that intestinal microbes are essential for the fate regulation of nestin⁺ cells in the enteric nervous system. In addition, nestin was found in intestinal cells of Cajal (ICCs) and in gastrointestinal stromal tumours derived from ICCs [109], [110]. Nestin⁺ ICCs can be found in the antrum, small intestine and annular musculature of the colon, and nestin is also expressed by some CD34⁺ fibroblast-like cells and other cell types in the mucosa and serosa [109]. Therefore, nestin expression is prevalent in the gastrointestinal tract, but its regulation requires further exploration (Fig. 3B).

Nestin may serve as a biomarker of stem/progenitor cells in the pancreas

In the pancreas, nestin⁺ stem/progenitor cells have MSC characteristics. They exhibit high proliferative potential and have the capacity to differentiate into insulin-producing cells in vitro [111], [112]. Melatonin may improve the self-renewal ability of pancreatic nestin⁺ stem cells through extracellular signal-regulated kinase (ERK) signaling [113]. Additionally, nestin expression was identified in pancreatic fibroblasts, pancreatic epithelial cells, pericytes, vascular endothelial cells and acinar cells [114]. In islets, nestin⁺ cells show an apparent vascular nature and are closely related to endocrine cells, indicating that they are essential to islet growth and maintenance [115]. Moreover, nestin⁺ stem cells obtained from pancreatic islets could differentiate into cells with pancreatic endocrine, exocrine and hepatic phenotypes, suggesting that nestin⁺ progenitor cells from islets are multipotent [116] (Fig. 3B).

Nestin⁺ cells are vital to liver development and repair

Nestin-GFP⁺ cells have been found in the fetal liver with MSC lineage marker expression, and they exhibited trilineage and mesenchymal lineage differentiation capacity ex vivo [117]. In addition, these nestin⁺ cells were mainly pericytes and could associate with portal vessels to regulate the HSC niche in the fetal liver, as well as produce factors to maintain HSCs in culture [117]. These characteristics of liver nestin⁺ cells are similar to those of nestin⁺ cells in bone marrow, revealing the close relationship between nestin⁺ cells and HSCs. In the adult liver, nestin is barely expressed under normal healthy conditions but is re-expressed when acute or chronic liver injuries occur, suggesting a potential role of nestin in liver repair [118]. It has been demonstrated that nestin can be expressed by hepatic stellate cells under TGF-β stimulation, and nestin expression is associated with the degree of hepatic fibrosis positively and thus may be a novel target for liver fibrosis treatment [118]. Furthermore, nestin has been widely studied in the liver under malignant conditions, indicating that nestin has the potential to be a biomarker for diagnosing specific liver tumours [119], [120], [121], [122]. Apart from its role in liver cancer, the role of nestin in other hepatic diseases is poorly understood; therefore, the role of hepatic nestin⁺ cells needs to be further explored.

Nestin⁺ cells contribute to tumour pathologic progression

Nestin⁺ cells are involved in the migration, invasion and metastasis of cancer cells in the digestive system. To date, the expression of nestin has been identified in gastrointestinal stromal tumours, gastric adenocarcinoma, colorectal cancer, gastrointestinal schwannomas, granular cell tumours in the gastrointestinal tract, ductal adenocarcinoma, acinar cell carcinoma, pancreatoblastoma, solid-pseudopapillary neoplasms, and serous cystadenoma in the pancreas [110]. Tumour cell behaviour can be regulated by nestin, for example, in gastrointestinal stromal tumours, by affecting mitochondrial recruitment of Dynamin-related protein1 and mitochondrial elongation, nestin can influence mitochondrial dynamics and reactive oxygen species (ROS) levels to regulate tumour cell proliferative and invasive abilities [123]. And the nestin-Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) axis plays an important role in the proliferation, migration, and invasion of gastric cancer cells [124]. Similarly, the expression of nestin is related to pancreatic cancer cell migration, invasion and metastasis. For example, nestin can increase cell motility and tumour metastasis in pancreatic ductal adenocarcinoma via regulation of epithelial-mesenchymal transition by TGF-β1, and nestin phosphorylation at threonine 315 and threonine 1299 was found to be associated with cancer cell proliferation and metastasis [109], [125]. In addition, in colorectal cancer, nestin is regarded as a promising angiogenesis marker [126]. Therefore, nestin plays an essential role in cancer development, and it has great potential to become a diagnostic factor for digestive system tumours (Table 3).

Table 3.

The contributions and regulations of nestin⁺ cells in digestive system.

Distribution	Nestin+ cells	Contribution	Regulation	Reference
Enteric nervous system	Enteric neural precursor cells, intestinal neurons, and glial cells	Nestin was expressed by proliferating cells, and nestin was related to neurons renewal	Intestinal microbes, intestinal serotonin network	[108]
			Intestinal microbes	[107]
Intestinal stromal	ICCs, gastrointestinal stromal tumors(GISTs)	Nestin could serve as a desirable marker for GISTs diagnosis	Nestin has concomitant expression with KIT and CD34 in some ICCs and GISTs	[110]
Antrum, small intestine and annular musculature in the colon	ICCs	Not mentioned		[109]
Pancreas	Pancreatic stem cells(PSCs), pancreatic fibroblasts, pancreatic epithelial cells, pancreatic endocrine precursor cells, vascular endothelial cells and acinar cells	Nestin expression was associated with pancreatic stroma development; nestin+ fetal pancreatic epithelial cells differentiated into insulin-secreting beta-cells	Melatonin, ERK pathway	[113], [114]
Islet	PSCs	Nestin+ PSCs could differentiate into pancreatic endocrine, exocrine and hepatic phenotypes; nestin+ cells were essential for the growth and maintenance of islets	Environmental growth factors induce nestin+ PSCs differentiation	[115], [116]
Gastrointestinal stromal tumors	Gastrointestinal stromal tumor cells	Nestin affacts tumor cells’ proliferation and invasion	Nestin regulate mitochondrial dynamics and alter intracellular ROS levels	[123]
Gastric cancer	Gastric cancer cells	Nestin affected the proliferation, migration, and invasion of gastric cancer cells	Nestin-Keap1-Nrf2 axis	[124]
Pancreatic ductal adenocarcinoma	Pancreatic ductal adenocarcinoma cells	Nestin increased cell motility and tumor metastasis	The regulation of TGF-β1-induced epithelial-mesenchymal transition	[109]
Pancreatic cancer	Pancreatic cancer cells	Nestin correlated with cancer proliferation and metastasis	Nestin phosphorylation at threonines 315 and 1299	[125]
Colorectal cancer	Proliferating endothelial cells	Nestin was linked to angiogenesis of small blood vessels	–	[126]

Nestin⁺ cells in the urinary system

Nestin⁺ cells contribute to kidney injury repair and regeneration

During kidney development, nestin⁺ glomerular endothelial progenitor cells can be found in immature glomeruli, and transient expression of nestin has been found in immature proximal tubule epithelial cells in the newborn kidney [127] (Fig. 4A). In the adult kidney, nestin is persistently expressed by podocytes, and its expression is restricted to differentiated podocytes; therefore, nestin may be essential for the maintenance of podocyte structural integrity [11]. In addition, nestin⁺ stem/progenitor cells can be found in glomeruli and interstitial and renal papilla, and they may be related to kidney regeneration [128], [129]. For example, nestin⁺CD133⁺ progenitor cells found in human renal papilla are capable of differentiating into neural- and epithelial-like cells, and they retain the ability to generate tubules [128].

Fig. 4.

Nestin expression in urinary system and reproductive system.

During tubulointerstitial and ischaemic injury, nestin re-expression has been identified in renal tubule cells and glomerular, endothelial and perivascular cells, and the nestin⁺ cells migrated from the medulla to the cortex in postischemia kidneys [127], [130], [131]. In addition, nestin⁺ kidney-resident MSCs in glomeruli and interstitial tissues were found to reduce damaged cell apoptosis and prevent ischaemic acute renal failure via VEGF secretion, indicating that nestin may contribute to injury repair [129]. Furthermore, the increase in nestin expression during kidney injury is vital to the protection and regeneration of mesangial cells and podocytes [132]. For instance, nestin expression prevented the damage from mitophagy and oxidative stress, therefore protecting podocytes and stopping proteinuria during lupus nephritis [11]. When compared with normal kidney, podocyte nestin expression was reduced in patients with diabetic nephropathy, membranous nephropathy(MN), focal stage glomerulosclerosis(FSGS) and IgA nephropathy with proteinuria and podocyte foot process effacement[11]. The reduction of nestin expression could impair podocytes cytoskeleton, and this may prevent podocyte from establishing selective permeability of the glomerular filtration barrier and lead to proteinuria [133], [134]. Given the crucial role nestin plays in podocyte-dependent proteinuria, nestin is expected to be a potential target for proteinuria therapy [11].

Nestin⁺ cells in the reproductive system

Nestin⁺ cells correlate with epithelial cell self-renewal and cancer progression in the prostate

In the adult prostate, self-renewal of luminal and basal epithelial cells occurs during regeneration, and epithelial-primed nestin⁺ MSCs exist in the basement membrane and demonstrate prostate stem cell characteristics in adults, suggesting that nestin may contribute to the epithelial lineage during development and regeneration in the prostate [135] (Fig. 4B). Nestin is regarded as a prognostic factor for aggressive prostate diseases because it is related to prostate cancer cell migration and metastasis [136], [137]. In addition, nestin likely operates exclusively in androgen-deprived tumours and may be related to Notch and Hedgehog signaling [137], [138]. Furthermore, nestin correlates with angiogenesis and can regulate cancer cell invasion by affecting focal adhesion kinase (FAK) and integrins in prostate cancer, indicating that nestin is important for cell motility and may have an influence on malignant transformation in prostate cancer [139], [140].

Nestin serves as a cell marker of testicular Leydig precursor cells

Testicular Leydig cells are postmitotic cells expressing neuroendocrine markers. Nestin is located in the perinuclear cytoplasm, and its expression is upregulated in Reinke crystalloids when Leydig cells age [141]. Adult Leydig cells have four phasic developmental processes: stem Leydig cells (SLCs), progenitor Leydig cells, immature Leydig cells, and adult Leydig cells [142]. Nestin has been proven to be a marker of SLCs, which contribute to adult Leydig cell development and maintenance, and CD51 might be used to identify nestin⁺ SLCs [142], [143], [144], [145]. Androgen in mammalian testes is mainly from Leydig cells; therefore, using nestin as an SLC marker may provide novel insights into testosterone deficiency [144]. Furthermore, nestin⁺ SLCs in the fetal testis can differentiate into pericytes and smooth muscle cells in addition to Leydig cells, suggesting that they are a multipotent progenitor population [146]. In addition, nestin expression has also been found in some vascular endothelial cells, a subset of peritubular spindle-shaped cells in normal testes, and hyperplastic Leydig cells, Sertoli cells, and mesenchymal and neuroepithelial cells associated with testicular malignancies, supporting that nestin⁺ progenitor cells are abundant in adult testes [141], [147] (Fig. 4C).

Nestin is related to uterine cancer

Nestin expression has been found in cervical intraepithelial neoplasia and cervical cancer specimens, and upregulated nestin expression can stimulate the formation of colonies and spheres in vitro [148]. Although the contribution and regulatory mechanism of nestin⁺ cells in the uterus are poorly understood, nestin is believed to be essential for cervical tumour formation, and nestin may contribute to uterine cancer stem cell regulation [110], [148].

Nestin is a marker of and prognostic factor in breast cancer

Nestin expression can be found within basal/myoepithelial cells of the mammary gland (Fig. 4D), the regenerative compartment of the normal human mammary gland, and the mammary gland of pregnant mice, with nestin⁺ cells displaying features of mammary progenitors [149]. In addition, nestin is an alternative marker for basal epithelial breast tumours. Furthermore, nestin is closely related to breast cancer-specific survival and has been regarded as an independent prognostic factor [74], [150]. In addition, nestin expression leads to positive regulation of breast cancer cell proliferation, survival and invasiveness via enhancement of Wnt/β-catenin activation [151]. Nestin may be correlated with melatonin (MT1)-mediated signalling pathways, since coexpression of nestin and MT1 has been found in more advanced tumours [152] (Table 4).

Table 4.

The contributions and regulations of nestin⁺ cells in reproductive system.

Ditribution	Nestin+ cells	Contribution	Regulation	Reference
Testis	Stem Leydig cells (SLCs)	Nestin+ cells were associated with the development and maintenance of adult Leydig cells	–	[142]
		Nestin correlated with cell division activity	Nestin expression decreased with the increase of adult Leydig cells	[143]
		Nestin+ SLCs could differentiate into testosterone- producing Leydig cells, had multilineage differentiation capacity in vitro, and promoted meiotic and post-meiotic germ cell recovery	–	[144]
	Perivascular cells	Nestin+ cells would differentiate into Leydig cells, pericytes and smooth muscle cells	Notch signaling	[146]
	Some vascular endothelial cells, a subset of peritubular spindle-shaped cells	Nestin formed heteropolymers with vimentin	–	[141]
Testicular malignancies	Hyperplastic Leydig cells, Sertoli cells, mesenchymal and neuroepithelial cells	Nestin was associated with nodules of hyperplastic Leydig cells	–
Uterus	Cervical cancer cell lines	Nestin could regulate cancer stem cells functions and stimulate colony and sphere formation in vitro	–	[148]
Mammary gland	Basal/ myoepithelial cells	Nestin is a promising marker of basal epithelial breast tumors	The expression of nestin and DeltaN-p63 were regualted coordinately	[149]
Triple- negative breast cancer	Breast cancer cells	Nestin positively regulated the proliferation, survival and invasion of breast cancer cells	Wnt/β-catenin signaling pathway	[151]
Primary, invasive breast carcinoma		The coexpression of nestin with melatonin (MT1) was linked to specific tumor stage	MT1-mediated signaling pathways	[152]

Nestin⁺ cells in the endocrine system

Multipotent adrenal progenitor cells express nestin

Progenitor cells expressing nestin have been found in both the cortex and medulla of the adrenal gland, showing multipotency [153], [154], [155] (Fig. 5A). Nestin⁺ adrenocortical progenitors are distributed throughout the cortex; they can differentiate into mineralocorticoid- and glucocorticoid-producing cells under hormone regulation, and lineage tracing has revealed their slow centripetal migration [153]. In the adrenal medulla, nestin⁺ progenitors overlap with CD133⁺ cells and are able to produce globules called chromospheres in vitro, and the progeny of nestin⁺ cells include cells with glial, neuronal, and chromaffin identity [154], [156], [157]. Because nestin⁺ cells share common properties with NSPCs, adrenal progenitor cells have the potential to treat neurodegenerative diseases [68]. Moreover, nestin⁺ cells are related to adrenal tumours. Pheochromocytoma and paraganglioma are rare neuroendocrine tumours, and nestin expression has been reported in vasculoneural paraganglioma and a few cases of pheochromocytoma. Furthermore, adrenal nestin⁺ cells may give rise to vasculogenesis and paraganglioma formation. Therefore, nestin can possibly serve as a predictor of tumour malignancy [158], [159].

Fig. 5.

Nestin expression in endocrine system and immune system.

Nestin⁺ multipotent stem cells in the pituitary

Stem cells expressing nestin exist in the anterior pituitary, and lineage tracing shows that nestin⁺ stem cells from the anterior pituitary can differentiate ex vivo into six terminally differentiated pituitary endocrine cell types (melanotrophs, corticotrophs, gonadotrophs, somatotrophs, lactotrophs, and thyrotrophs), indicating that nestin⁺ stem cells in the pituitary are multipotent [160]. Furthermore, nestin⁺ cells colocalize with Sox2 in the marginal cell layer but not in the anterior lobe or submarginal zone [161]. In pituitary adenoma, nestin expression was found in gonadotrophic pituitary adenoma stem cells [162]. Nestin⁺ cells mainly display a mesenchymal-like morphology, participating in the establishment of stem/progenitor cell niches in the anterior pituitary [161]. In addition, because these nestin⁺ stem cells do not exhibit expression of embryonic pituitary precursor markers and are barely found in the newborn pituitary, they may be stem cells for adult instead of embryonic tissues [160], [163].

Two types of pituitary cells express nestin, one close to the lumen and the other close to blood vessels, suggesting that nestin may be involved in vascular development [164] (Fig. 5B). Nestin expression was identified in endothelial cells and pituitary adenomas and in newly formed capillaries during pituitary infarction/apoplexy, indicating that nestin may be linked to endothelial cell maintenance and pituitary adenoma vascularization [153], [165], [166], [167], [168]. Moreover, the proliferation and differentiation of nestin⁺ progenitor cells in the pituitary and adrenal cortex were enhanced by insulin and were associated with the hypothalamus, revealing the vital role of nestin⁺ progenitors in the hypothalamic–pituitary–adrenal metabolic axis [155].

Nestin⁺ cells in the immune system

Nestin⁺ cells influence lymph node development and the immune microenvironment

During embryonic and postnatal development of lymph nodes, various nestin⁺ cell types can be found, and nestin⁺ precursor cells contribute to mesenchymal and endothelial stromal cell pools [169] (Fig. 5C). Retinoic acid receptor (RAR) γ in these nestin⁺ cells plays a critical role in regulating B and T lymphopoiesis within bone marrow and the thymus, respectively, and the deletion of RARγ results in smaller thyme [170]. Nestin is strongly expressed in lymph nodes in melanoma, indicating that nestin may serve as a diagnostic marker for melanoma staging, but the underlying mechanisms remain to be explored [171]. In addition, nestin⁺ MSCs isolated from lung explants were able to support B-cell growth though they downregulated T-cell and natural killer (NK) cell proliferation, supporting that nestin⁺ cells may influence the immune microenvironment [9].

Summary and prospects

Nestin as a multilineage stem/progenitor cell marker

During body development, nestin⁺ cells have been reported in a multitude of systems, mostly characterized by staged expression. These nestin⁺ cells show characteristics of progenitor cells, such as multipotency and tissue regeneration ability, and some of them exhibit MSC activity. In addition to the nestin⁺ cells summarized in this review, nestin⁺ stem/progenitor cells also exist in fat [172], [173], skin [174], hair follicles [175], and retina [176]. The above evidence indicates that nestin has great potential to be a multilineage stem cell marker [2]. In adulthood, nestin⁺ resident stem cells are found in some systems, such as the circulatory system and urinary system, and they can be activated to take part in tissue repair after injury. Aside from stem cells, other cell types expressing nestin are also beneficial for tissue niche maintenance and tissue regeneration; therefore, nestin may be an essential component regulating tissue regeneration.

In general, in nestin⁺ stem cells and adult cells that re-express nestin after injury, nestin often directly affects cell biological behaviours such as proliferation, apoptosis and migration regulation in response to different tissue injuries. Furthermore, nestin⁺ cells can be recruited to the injured area for tissue repair, for example, nestin⁺ cells during myocardial infarction and renal ischaemic injury [84], [130]. In particular, nestin⁺ cells can also recruit other cells to participate in tissue repair: for example, Gdf5-lineage cells are recruited by nestin⁺ cells during cartilage repair [77]. In addition, nestin⁺ cells can also affect the disease process by secreting factors such as CXCL12, TGFβ, and BMP7, suggesting that nestin⁺ cells may have an influence on the tissue microenvironment. To date, although nestin⁺ cells have powerful functions, most of their functional regulatory mechanisms have not been clarified. Therefore, future research may focus on the precise regulation and intervention of nestin⁺ cells to exploit their benefits to tissue repair and regeneration under specific physiological and pathological conditions.

Value of nestin⁺ cells in future therapeutic strategies

Nowadays, there have been a few studies using nestin⁺ cells for disease treatment. For example, in inflammatory bowel disease (IBD) researchers found that nestin⁺ cells derived from Peyer's patch exhibited MSC-like biological characteristics [177]. Then they delivered these nestin⁺ MSCs to mice by intravenous injection, and found that nestin⁺ MSCs could enhance healing of IBD through IL-22-mediated intestinal epithelial repair [177]. In addition to the direct use of nestin⁺ cells for disease treatment, nestin has also been used as an indicator of disease prognosis. In multiple myeloma [178], retinal degeneration [179] and ischemic stroke [180], [181], nestin expression was viewed as an indicator of stem cell recovery and nerve regeneration. Besides, nestin has the potential for an evaluation index for drug screening. To increase adipose-derived stem cells (ASCs) neurotrophic properties for better nerve injury repair, Brambilla et al. compared different ASCs culture strategy [182]. The results showed that nestin served as an effective indicator for cell comparison, as ASCs with higher nestin expression exhibited better nerve regeneration abilities [182]. In testing potential drugs for Alzheimer's disease, neurodevelopmental and neuropsychiatric disorders, nestin expression was included in drug efficacy evaluation [183], [184]. Considering nestin⁺ cells are widely distributed in all body system, nestin⁺ cells may serve for other organs and tissues in disease prognosis, drug testing and even disease prevention in the future. Therefore, understanding nestin⁺ cells in tissue development, regeneration, or pathological processes is of great importance.

The controversy of nestin

At present, most studies explore the function of the nestin gene by knockout or overexpression. However, there are some unavoidable limitations to current research, such as in studies using different nestin knockout mice mentioned in the previous chapter, there is a controversy about whether nestin⁺ neural stem cells are necessary for neural development [30], [31]. Such inconsistencies exist in nestin⁺ cells labeling as well. For example, in developing bone marrow cre recombinase driven by nestin enhancer (Nes-creER) were predominantly endothelial cells, but nestin-GFP⁺ cells included endothelial and osteogenic cells [64]. Therefore, the nestin transgenic mouse models should be carefully chosen in order to label the wanted cells [5].

The correlations between nestin⁺ cells and other cell populations

It is also important to clarify the interaction between nestin⁺ cells and other cell populations. The close correlation between nestin⁺ cells and HSCs in bone marrow has been confirmed, and selective depletion of nestin⁺ cells results in decreased HSC activity [63]. In addition, in the fetal liver, nestin⁺ cells regulate the niche of HSCs, further implying that nestin⁺ cells are vital for the maintenance of HSCs [117]. Following cartilage injury, perivesicular nestin⁺ cells recruit Gdf5-lineage cells to help with cartilage repair [77]. In bone marrow, a relationship between nestin⁺ microvasculature cells and CD271⁺ MSCs has been reported. Nestin⁺ cells are in close contact with CD271⁺ MSCs, but the physiological function of their interaction requires further exploration [185]. In spinal cord injury (SCI), Wang et al. found that CD8⁺ T cells could promote the differentiation of nestin⁺ NSCs into astrocytes which contribute to SCI repair treatment, and they continued identifyting INF-γ as a crucial mediator of CD8⁺ T-cell-NSC cross talk and a potential therapeutic for SCI [186]. This study is an example of finding new therapeutic targets by exploring the interactions between nestin⁺ cells and other cells. In the case of enteric nerve injury, Fan et al. found that bone marrow-derived mesenchymal stem cells transplantation could promote nestin⁺ enteric neural precursor cells to differentiate into enteric neurons and glial cells and led to better recovery, suggesting using other stem/progenitor cells to regulate nestin⁺ cells activity may be beneficial for the development of new therapies [187]. Hence, the relationship between nestin⁺ cells and other cell populations, especially stem/progenitor cells, is worth investigating and will be helpful for understanding the regulatory mechanisms of nestin⁺ cells within the tissue microenvironment.

In conclusion, the expression of nestin in all body systems, including multiple tissues and organs has been identified. However, most studies have only investigated the existence of nestin⁺ cells and their relevance to tissue function maintenance, injury regeneration or disease, without further elucidating the mechanism of nestin⁺ cells and how they are regulated. Due to the limited research on the mechanism of nestin⁺ cells, our summary of the regulatory mechanism may not be perfect. Thus we suggest that future studies should further focus on the mechanism of nestin⁺ cells to expand the understanding of nestin⁺ cells. And it should be noted that the choice of nestin transgenic mice needs carefully consideration, because the constructs in different transgenic reporter lines are unlike [5]. We hope that this review can help others realize the importance of nestin as a marker of stem/progenitor cells in tissue homeostasis maintenance, injury repair and regeneration, as well as the application potential of nestin⁺ cells for disease treatment.

Search strategy

A systematic literature search of the electronic databases PubMed, Web of Science up to August 2023 was performed, without any limitation of origin and languages. The studies were identified by a random combination of the following terms: “nestin”, “stem cells OR progenitor cells”, “tissue regeneration”, “tissue development”. In addition, the reference lists of the retrieved studies and review articles were manually searched for potentially relevant studies. Studies were eligible if they met the following criteria: (a) studies were published as original articles with full text available; (b) the correlation of nestin expression with biological events was analyzed. Studies were excluded from the analyses based on the following criteria: (a) articles were published as abstracts, case reports, letters or comments; (b) studies were not associated with the topic of the interest; (c) data for estimating the relationship between nestin expression and biological events were insufficient.

Compliance with ethics requirement

This article is based on previously conducted studies and does not contain any studies with human participants or animals performed by any of the authors.

CRediT authorship contribution statement

Ziyang Tong: Writing – original draft, Visualization. Zi Yin: Writing – review & editing, Supervision.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Biographies

Zi Yin is a professor of Stem Cell and Regenerative Medicine at School of Medicine in Zhejiang University, she designed and reviewed the manuscript. Professor Zi Yin is the first person in the world who discovered and resolved the subsets of human tendon tissue cells using single cell technology, and she identified a new subset of nestin⁺ tendon stem cells with strong teno-lineage differentiation potential. Professor Zi Yin focus on the discovery of new subsets of tendon stem cells and their interaction with microenvironment, and have published over 60 international peer-reviewed journals in the field of tendon research.

Ziyang Tong is a PhD candidate at Stem Cell and Regenerative Medicine School of Medicine in Zhejiang University, she wrote and revised the manuscript. Her currently research interests include the identification and regulation of tendon stem cells.