Table 3.

Immunohistochemical outcomes in studies.

Author	Marker	Level of Expression/ Regulation	Description
Hou et al., 2021 [12]	GFAP MAP2 GAP43 MBP Iba-1 CD68 CD163	↓ ↑ ↑ ↑ ↓ ↓ ↑	GFAP decreased in treatment group suggesting treatment to inhibit reactive astrogliosis. MAP2 staining in the treatment group demonstrated a shorter distance between the neurons and the lesion centre compared to control indicating neuronal regrowth/survival. Increased GAP43-positive axons in the treatment group. GAP43 is involved with nerve regeneration. MBP increased in the lesion site of the treatment group suggesting remyelination. Iba-1 (microglia marker) decreased, CD163 (M2-associated marker) increased, CD68 (microglia activation marker) decreased in treatment group, thus treatment reduced microglia activation and promoted microglia polarization towards M2 phenotype.
Jin et al., 2021 [13]	NF-200 C-caspase-3	↑ ↓	NF-200 positive axons were increased in treatment group suggesting promotion of axon regrowth/regeneration. Decrease in C-caspase-3 suggested a decrease in apoptosis in the treatment group.
Wang et al., 2018 [14]	NF200 CD86 CD206	↑ ↓ ↑	NF-200 positive axons were increased in treatment group suggesting promotion of axon regrowth/regeneration. Decreased CD86+ cells. Increased CD206+ cells suggested an anti-inflammatory effect in the treatment group.
Ma et al., 2020 [15]	GFAP MBP NestinNeuN	↓ ↑ ↑ ↑	GFAP decreased in combined treatment group indicating that the treatment prevented NSC differentiating into astrocytes; astrocytes contribute to glial scar formation. MBP increased in combined treatment group suggesting treatment to promote NSC differentiation into oligodendrocytes. Nestin increased in combined treatment group suggesting more survival and proliferation of NSCs. NeuN increased in combined treatment group suggesting treatment promoted NSC differentiation into neurons.
Wang et al., 2017 [16]	GFAP 5-HT NF-200	↑ ↑ ↑	GFAP-positive cells increased in treatment group suggesting that the treatment promoted astrocyte activation. Increase in 5-HT positive neurons. Increase in NF200 suggested that the treatment promotes axonal regeneration.
Mountney et al., 2013 [17]	5-HT TH CGRP	- - ↑	Combined treatment had no difference in 5-HT expression from controls. 5-HT was used to identify descending axons from the brainstem. Combined treatment showed no difference in TH expression compared to controls. TH was used to identify catecholaminergic axons. Combined treatment showed an increase in expression of CGRP. This is a marker for a subtype of sensory axons.
Maqueda et al., 2019 [18]	GFAP Iba-1 Fibronectin and NF200 Reca1	↑ ↓ ↑ ↑	Treatment group had an increase in GFAP expression, however results showed that astroglial reactivity was limited compared to control group. Iba-1 expression was significantly higher in control groups compared to the treatment group suggesting a reduced microglial activity in the treatment group. Increase expression of fibronectin and NF200 in treatment group suggested an increase in the formation of matrix material and axonal sprouting. Increase in Reca1 suggested that the treatment promoted vascularisation.
Rong et al., 2019 [19]	NeuN NF200 GFAP	↑ ↑ ↓	Increased NeuN staining in treatment group suggesting an increased number of motor neurons. NF200 increased and GFAP decreased in treatment group compared to SCI injury control group suggesting treatment to promote axon regeneration and inhibit glial scar formation.
Grosso et al., 2014 [20]	ED-1	↓	Decreased ED-1 positive macrophages in the combined treatment group compared to control groups suggesting treatment to reduce macrophage accumulation and thus neuroinflammation.
Krityakiarana et al., 2016 [21]	HSP-70 HSP-32 Nestin NG2	↑ ↑ ↑ ↑	HSP-70 in grey matter (neuronal cell bodies) was increased in treatment compared to control groups. HSP-70 repairs/degrades polypeptides that have denatured due to cellular stress. HSP-32 expressing cells were increased in treatment group. HSP-32 is involved with controlling acute inflammation. Nestin expressing cells were increased in treatment group compared to control suggesting an increase in undifferentiated NSCs as Nestin is a NSC marker. NG2 marker was examined to determine effect of treatment on oligodendrocyte progenitor cells. NG2 was increased in treatment group suggesting potential remyelination.
Bonilla et al., 2021 [22]	GFAP β-III-tubulin NeuN and synaptophysin Iba-1 and Arginase-1	↓ ↑ ↑ * ↑ *	Decreased staining of GFAP positive areas suggesting a significantly reduced glial scar in combined treatment group. Increased staining of β-III-tubulin positive areas in combined treatment group suggesting nerve fibre preservation in combined treatment group. Co-localisation of NeuN and synaptophysin was increased significantly in combined treatment group indicating preservation of functional synapses. Co-localisation of Iba-1 and Arginase-1 was increased in combined treatment group suggesting treatment to promote polarisation of microglia towards an anti-inflammatory phenotype.
Karalija et al., 2014 [23]	OX42 5-HT	↓ ↑	OX-42 immunoreactivity was decreased with both treatment groups suggesting the treatments to alter the microglial response and thus the neuroinflammatory response. 5-HT positive axons were increased in both treatment groups compared to control suggesting axonal sprouting.
Karalija et al., 2012 [24]	MAP2 and synaptophysin NF GFAP OX42	↑ ↑ - ↓	Both treatment groups increased immunoreactivity for MAP2 and synaptophysin compared to control suggesting improved preservation of dendritic branches and synaptic boutons. NF was increased in both treatment groups compared to control suggesting axonal sprouting. GFAP staining showed no difference in treatment compared to controls suggesting no effect on reactive astrocytes. OX42 was decreased in both treatment groups compared to controls suggesting a reduced microglial response.
Pallier et al., 2015 [25]	NeuN APC Iba-1 GFAP	↑ ↑ ↓ ↓	Increased NeuN staining in treatment compared to controls indicating a reduced loss of NeuN-positive cells suggesting neuronal protection/survival. Increased APC staining indicating a reduced loss of APC-immunoreactive oligodendrocytes in treatment group compared to controls. Decreased staining for Iba-1 in treatment compared to controls suggesting decreased microglia activation. Decreased GFAP staining in treatment group suggesting decreased reactive astrogliosis.
Zhang et al., 2016 [26]	GAP-43	↑	Significantly increased GAP-43 staining in combined treatment one week after SCI suggesting axon regeneration.
Wang et al., 2014 [27]	GFP NF200	↑ ↑	Increased number of GFP positive NSCs in the combined treatment group indicating increased NSC survival. Increased NF200 in combined treatment group suggesting promotion of nerve regeneration.
Salarinia et al., 2020 [28]	NF200	↑	Number of NF200 positive axons in combined treatment group was significantly increased compared to controls indicating axon regeneration.
Liu et al., 2013 [29]	GFAP Iba-1 Caspase-3	↓ ↓ ↓	Decreased levels of GFAP Decreased Iba-1 compared to controls suggesting treatment reduces astrogliosis and inflammation. Reduced caspase-3 staining in treatment group suggesting treatment reduces post-traumatic apoptosis.
Garcia-Álvarez et al., 2015 [30]	GFAP NF MBP	↓ ↑ ↑	Decreased GFAP-positive cells in treatment group suggesting inhibition of astroglial cells. Presence of NF-positive cells in treatment group which were not observed in controls suggesting the presence of cortical neurons after inhibition of astroglial cells (which prevented neural precursor cell proliferation). NF staining was also increased in dorsal root ganglion cultures indicating the treatment to induce axonal outgrowth. Increased MBP in treatment group suggesting increase in oligodendrocyte MBP expression.
Sakka et al., 2014 [31]	NF	↑	Increased NF staining in treatment group suggesting neurite regrowth.
Tsai et al., 2019 [32]	β-III-tubulin	↑	Increased β-III-tubulin staining in treatment group which suggested preserved nerve fibres (axons).
Zhou et al., 2017 [33]	Nrf2	↑	Increased expression of Nrf2 in the treatment group suggested the treatment to activate the Akt/Nrf2/ARE signalling pathway therefore inducing anti-inflammatory and antioxidant responses.
Liang et al., 2014 [34]	C-caspase-3 NeuN	↓ ↑	Decreased C-caspase-3 positive neurons compared to control suggesting treatment to inhibit neuronal apoptosis. Increased NeuN-positive cells in treatment group suggesting treatment to protect/prevent neuronal loss.
Wang et al., 2014 [35]	GFAP and Nestin Iba-1 NF200	↓ ↓ ↑	Decreased GFAP and Nestin positive areas in treatment group compared to control suggesting a reduced amount of reactive astrogliosis with treatment application. Decreased amount of Iba-1 positive cells in treatment group suggesting inhibition of macrophage/microglia activation and thus inflammation in the lesion site. Increase in NF200 stained areas within the lesion site in treatment group suggesting increased number of neurons/axons and therefore neuron and axon protection.
Sun et al., 2013 [36]	NeuN and NF200	↑	Increased NeuN and NF staining in treatment group compared to controls suggesting neuron preservation and axon regeneration.
Machova-Urdzikova et al., 2017 [37]	GAP43	↑	Increased number of GAP43 positive fibres in treatment group compared to control suggesting axonal sprouting and thus axon regeneration.
Sahu et al., 2018 [38]	GFAP Iba-1 5-HT and NF200	↓ ↓ ↑	Decreased GFAP staining in treatment group suggesting reduced astrogliosis.Decreased Iba-1 immunoreactivity in treatment group suggesting treatment to attenuate microglia/macrophage activation and thus inflammation. Increased 5-HT and NF200 staining in treatment group indicating 5-HT nerve reinnervation and axonal regrowth.
Ahmed et al., 2014 [39]	GAP43 GFAP	↑ ↓	Increased number of GAP43 positive axons in treatment group suggesting axonal regrowth. Decreased GFAP staining in treatment group suggesting treatment to inhibit reactive astrocytes.
Yin et al., 2013 [40]	GFAP	↓ *	Decreased GFAP staining with combined treatment suggesting treatment to impair astrogliosis.
Yuan et al., 2012 [41]	GFAP CPSG Iba-1	↓ ↓ ↓	Decreased GFAP positive cells in peri-lesion areas compared to controls suggesting inhibition of reactive astrogliosis. Decreased size of CPSG immunoreactive area in treatment group suggesting reduction in glial scar size. Decreased Iba-1 immunoreactive cells in peri-lesion area in treatment group suggesting inhibition of microglial activation thus inflammation.
Pan et al., 2014 [42]	GFAP NeuN 5-HT and TH	↓ ↑ ↑	Decreased GFAP immunoreactivity in treatment group suggesting reduced astrogliosis. Increased NeuN positive neurons in treatment group compared to control suggesting neuronal survival. Increased 5-HT and TH axonal staining rostral to lesion in treatment group suggesting prevention of dieback or regrowth of serotonergic neurons.
Lee et al., 2012 [43]	Iba-1	↓	Decreased Iba-1 positive cells in treatment group suggesting inhibition of infiltration of microglia and macrophages.
Aleksić et al., 2014 [44]	TH NeuN GFAP Iba-1	↑ - - ↓	Increased numbers of TH positive nerve fibres in treatment group compared to control indicating catecholaminergic axon regrowth/resprouting. No difference in NeuN positive neuron numbers in treatment or control group suggesting no effect on survival of neurons. No significant difference in GFAP scar staining suggesting no influence on glial scar. Decreased Iba-1 expression in treatment group but not statistically significant compared to control suggesting potential influence on microglia/macrophage response.
Wang et al., 2020 [45]	Acetylated tubulin and Tyrosinated tubulin NeuN and GAP43 HO-1 and NQO1	↑ ↑ ↑	Increased acetylated and tyrosinated tubulin ratios in neurons in the treatment group suggesting treatment to influence microtubule stabilisation and thus induce axon regeneration. Increased NeuN and GAP43 expression suggesting treatment to promote axon regeneration.Increased HO-1 and NQO1 in treatment group suggesting treatment to increase expression of antioxidants through activating the Nrf2/ARE pathway and therefore reduce oxidative stress.
Wang et al., 2017 [46]	5-HT	↑	Increased amount of 5-HT positive nerve terminals in treatment group suggesting treatment to promote neuronal repair.
Zhao et al., 2016 [47]	NF200	↑	Increased NF200 staining in combined treatment group suggesting axon regeneration due to increased number of axons and nerve fibres.
Chen et al., 2021 [49]	NeuN NF200, GAP43 and bungarotoxin	↑ -	Increased NeuN positive neurons indicating treatment to promote neuronal and axonal regeneration/survival. No difference in NF200, GAP43 and bungarotoxin staining of reinnervation of motor end plates between uninjured control and treatment group suggesting treatment to prevent denervation of neuromuscular junctions.
Zhou et al., 2022 [50]	GFAP and NeuN	↓ ↑	Decreased GFAP Increased NeuN staining in treatment group Suggests treatment allows for neuroplasticity and neuroregeneration.
Sperling et al., 2019 [51]	NF-M and β-III-tubulin GFAP	↑ -	Increased NF-M and slightly increased β-III-tubulin expression in treatment group suggesting axon regeneration/preservation. No difference in GFAP staining between control and treatment group suggesting no difference in glial scar formation, but there was increased GFAP staining in sham group compared to treatment which indicated glial scar formation in sham group and possible reduced glial scar formation in treatment group.
Ishii et al., 2012 [52]	5-HT GFAP	↑ -	Increased 5-HT positive fibres in treatment group indicating regeneration of serotonergic nerve fibres. No difference in GFAP staining between treatment and control groups therefore no difference in glial scar formation.
Bimbova et al., 2018 [53]	ED-1 Caspase-3 GFAP Iba-1 GAP43NF	↓ ↓ ↓ ↓ ↑ ↑	Decreased ED-1 positive macrophages in treatment group at 24 h suggesting a reduced amount of infiltrating activated macrophages. Decreased Caspase-3 staining at 24 h in treatment group suggested decreased apoptosis of oligodendrocytes, astrocytes, and neurons. Decreased GFAP in treatment group compared to controls suggesting reduced astrogliosis. Decreased Iba-1 in treatment group compared to controls seen at 24 h suggesting decreased activation of microglial cells. However, no clear difference in Iba-1 staining in treatment and controls after six weeks. Increased GAP43 staining in treatment group indicating axonal growth. Increased NF staining of axons observed in treatment group suggesting regeneration.
Huang et al., 2016 [54]	PTEN and PDCD4	↓	Decreased PTEN and PDCD4 staining at day 3 in treatment group. PTEN inhibition has been shown to have regenerative effects and inhibition of PDCD4 has been shown to protect against hypoxia induced apoptosis.

Notes: ↑ indicates increased staining/expression, ↓ indicates decreased staining/expression, - indicates no difference in staining/expression, assumed results from images are indicated by the symbol *. For the study by Pallier et al. [25] only the results from Study 2 are included in this table. Two studies by Caglar et al. [11] and Li et al. [48] did not report performing immunohistochemistry, thus were not included in this table. GFAP, glial acidic fibrillary protein; MAP2, microtubule-associated protein 2; GAP43, growth-associated protein 43; MBP, myelin basic protein; Iba-1, ionized calcium adaptor molecule 1; CD68, cluster of differentiation 68 (a microglial activation marker); CD163, cluster of differentiation 163 (a macrophage M2-associated marker); NF-200, neurofilament 200; C-caspase-3, cleaved caspase-3; CD86, cluster of differentiation 86 (an activated macrophage M1 marker); CD206, cluster of differentiation 206 (an activated macrophage M2 marker); Nestin, a marker of progenitor cells/stem cells; NeuN, neuronal nuclear protein (marker for neurons); NSC, neural stem cell; 5-HT, 5-hydroxytryptamine (serotonin); TH, tyrosine hydroxylase; CGRP, calcitonin gene related peptide; Reca1, marker for endothelial cells; SCI, spinal cord injury; ED-1, marker for macrophages (CD68); HSP-70, heat shock protein 70; HSP-32, heat shock protein 32; NG2, neuron-glial antigen-2; OX42, microglial marker; NF, neurofilament; APC, adenomatous polyposis coli tumour suppressor protein; GFP, green fluorescent protein; Nrf2, nuclear erythroid 2-related factor 2; CSPG, chondroitin sulphate proteoglycans; HO-1, heme oxygenase-1; NQO1, NADH dehydrogenase quinone 1; NF-M, neurofilament M; PTEN, Phosphatase and TENsin homolog; PDCD4, programmed cell death protein.and therefore an increase in staining suggests the treatment to promote axonal regeneration and/or survival of neurons [49].