Skip to main content
NCBI home page
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2009 Oct 1.
Published in final edited form as: Curr Opin Biotechnol. 2008 Sep 8;19(5):534–540. doi: 10.1016/j.copbio.2008.07.010

Mimicking Stem Cell Niches to Increase Stem Cell Expansion

Shara M Dellatore 1,*, A Sofia Garcia 1,*, William M Miller 1,2,†
PMCID: PMC2585613  NIHMSID: NIHMS74769  PMID: 18725291

Summary

Niches regulate lineage-specific stem cell self-renewal vs. differentiation in vivo and are comprised of supportive cells and extracellular matrix components arranged in a 3-dimensional topography of controlled stiffness in the presence of oxygen and growth factor gradients. Mimicking stem cell niches in a defined manner will facilitate production of the large numbers of stem cells needed to realize the promise of regenerative medicine and gene therapy. Progress has been made in mimicking components of the niche. Immobilizing cell-associated Notch ligands increased the self-renewal of hematopoietic (blood) stem cells. Culture on a fibrous scaffold that mimics basement membrane texture increased the expansion of hematopoietic and embryonic stem cells. Finally, researchers have created intricate patterns of cell-binding domains and complex oxygen gradients.

Introduction

Stem cells have widespread potential for regenerative medicine and the treatment of genetic disorders and cancer [1]. Although stem cell therapies are moving steadily towards the clinic, it has proven very difficult to increase tissue-specific stem cell numbers ex vivo without loss of stem cell potential. This contrasts with extensive self-renewal in vivo for the lifetime of an individual. It is now generally accepted that adult stem cells reside in specialized niches that coordinate self-renewal vs. differentiation [2–4]. This has led to the hypothesis that mimicking the stem cell niche will facilitate stem cell self-renewal and controlled differentiation ex vivo.

The various tissue-specific stem cell niches share many similar features. Heterologous (hub or stromal) cells provide critical cell-cell contacts and paracrine signaling, and a number of signaling molecules have been highly conserved from invertebrates to humans [2,3]. The extracellular matrix (ECM) retains stem cells in the niche and also serves to initiate signal transduction events – either alone or in synergy with cytokines. Further adding to the complexity, glycoasaminoglycans (GAGs) locally concentrate and present soluble growth factors. The niche established by supportive cells and the ECM likely regulates stem cell fate via complementary mechanisms including the presentation of immobilized signaling molecules in a defined manner, the modulation of matrix stiffness, and the creation of cytokine gradients (Figure 1). The physiochemical environment, including oxygen tension (pO2) and pH, also contributes to the regulation of stem cell replication and differentiation. In contrast to tissue-specific stem cells, embryonic stem cells (ESCs) are present only transiently in the developing embryo and therefore do not have a stable niche in vivo. ESCs also differ from tissue-specific stem cells in that they can be readily expanded in culture over extensive time periods. However, the culture systems that have been successfully used for ESC expansion suggest that ESC self-renewal vs. differentiation is regulated in a similar manner via interactions with other cells, ECM components, soluble factors and the physicochemical environment [5].

Figure 1. Schematic diagram illustrating several factors to consider when mimicking stem cell niches.

Figure 1

Open in a new tab

Variations in the co-localization, clustering, surface concentration, and gradients of two immobilized ligands are represented by red spheres and blue pyramids. Matrix stiffness and topography are depicted by the rippled membrane surface. Image drawn by Mark Seniw.

The complexity of the stem cell niche is challenging to reproduce. However, a number of microscale technologies have been developed for tissue engineering [6] and a wide range of natural and synthetic materials have been successfully used for stem cell culture [7,8]. In this review we focus on recent efforts to mimic cell-cell and cell-matrix interactions representative of the stem cell niche – with an emphasis on systems that presented ligands in a defined manner and that modulated stem cell self-renewal or differentiation (Table 1).

Table 1.

Mimicking stem cell niches to alter the regulation of stem cell expansion and controlled differentiation

Niche Properties System Details Species Cell Type Observations References
Ligand Presentation Immobilized Delta1-Fc Human HSPC ↑ Maintenance of undifferentiated cells, NOG engraftment [*11]
Jagged1 immobilized on Sepharose beads Mouse HSPC ↑ Notch signaling, male BDF1 engraftment in female BDF1 mice, secondary engraftment [12]
Multifunctional chimeric proteins immobilized by Ni chelating with decahistidine tag Rat NSC Expansion and maintenance of undifferentiated cells; thrombin-treatment exposes secondary region and induces astrocyte differentiation [19]
Immobilized IKVAV peptide in lipid bilayer surfaces Rat AHP Expansion and maintenance of undifferentiated cells; formed networks of 3D colonies [23]
Array of 500 µm × 500 µm LN derived peptides Human ESC Peptides identified for undifferentiated cell proliferation [**24]
Heparin on PEG hydrogel Human MSC Osteogenic differentiation [27]
Ormosil-immobilized adhesion peptides Rat ESC Neuronal differentiation, ↑ neurite length [*30]
Immobilized LN, FN, or Col w/EGF, NGF, NT-3, or CNTF Rat NSC Identified combinations for maintenance of undifferentiated cells or neuronal vs. astroglial differentiation [**31]
BMP-2 islands on fibrin gel Mouse MDSC Cells on BMP-2 islands became osteogenic, while surrounding cells formed myotubes [47]
Matrix Stiffness RGD-modified alginate gels Human MSC Stiff gels ↑ proliferation of hMSCs and committed progenitor cell lines [34]
Collagen-coated polyacrylamide gels Human MSC Directed differentiation into neuron, myoblast, or osteoblast lineages based on gel elastic modulus [**35]
Topography FN-coated PET nanofiber mesh Human HSPC ↑ Expansion and maintenance of undifferentiated cells, NOD/SCID engraftment [20]
Polyamide nanofiber mesh Mouse ESC ↑ Expansion and maintenance of undifferentiated cells [36]
Aminated PES nanofiber mesh Human HSPC ↑ Expansion and maintenance of undifferentiated cells, NOD/SCID engraftment [**37]
Open in a new tab

HSPC: Hematopoietic stem and progenitor cell, NSC: Neural stem cell; MSC: Mesenchymal stem cell; AHP: Adult hippocampal progenitor cell; ESC: Embryonic stem cell; MDSC: Muscle-derived stem cell; NOD/SCID: Non-obese diabetic severe combined immuno-deficient mice; NOG: NOD/SCID mice intercrossed with IL-2 receptor γ chain-knockout; BDF1: (C57B1/6 × DBA/2)F1; PEG: Polyethylene gycol; Ormosil: Organically modified silica; LN: Laminin; FN: Fibronectin; EGF: Epidermal growth factor; NGF: Nerve growth factor; NT-3: Neutrophin-3; CNTF: Ciliary neurotrophic factor; BMP-2: Bone morphogeneic protein-2; IKVAV: Laminin-derived peptide; RGD: Fibronectin-derived peptide; PET: Polyethylene terephthalate; PES: Polyethersulfone

Cell-cell interactions

Direct interactions between stem cells and supporting cells modulate stem cell retention and regulation. The essential role of cadherins in stem cell retention is illustrated by the observation that differentiation-defective germline stem cells displaced normal stem cells from their niche in the Drosophila ovary by upregulating E-cadherin expression [9]. Nagaoka et al. immobilized mouse E-cadherin as a fusion protein with the Fc domain of mouse IgG1 (E-cad-Fc) and showed that undifferentiated embryonic carcinoma cell lines, which form compact colonies on collagen or fibronectin, scatter on E-cad-Fc and display a spindle-shaped morphology with E-cadherin-rich protrusions [*10]. In contrast, mammary and kidney epithelial cell lines and primary hepatocytes formed tight colonies on E-cad-Fc, which suggests that the mechanisms of E-cadherin-mediated adhesion and migration vary with the state of cell differentiation [*10].

Juxtacrine activation of Notch signaling via cell-presented ligands has been implicated in many different stem cell niches [3,4]. Two recent studies suggest that inclusion of immobilized Notch ligand selectively increases the self-renewal of hematopoietic stem cells (HSCs) in cultures with cytokine cocktails optimized for primitive cell expansion. Suzuki et al. showed that coating plates with a fusion protein of Delta1 and the Fc domain of human IgG1 (Delta1-Fc) did not increase the overall expansion of human cord blood (CB) CD133+ cells or the production of CD133+CD34+CD38− cells during 3-week cultures, but approximately doubled the production of multi-potent progenitor cells (CFU-Mix) [*11]. Culture on Delta1-Fc doubled the number of cells able to reconstitute multi-lineage human hematopoiesis in immunodeficient mice, and bone marrow cells collected from primary recipients supported engraftment of human cells in two of three secondary transplant recipients [*11]. In a similar manner, Jagged1 immobilized on Sepharose beads had little effect on the ex vivo expansion of lineage negative (Lin−) mouse bone marrow cells during two weeks in culture, but greatly increased the production of male Lin− cells able to generate hematopoietic cell chimerism in secondary female transplant recipients [12]. In the presence of epithelial differentiation-inducing growth factors, immobilized rat Jagged1-Fc (via adsorbed protein G or bound anti-Fc antibody), but not soluble Jagged1, greatly enhanced Notch/CBF-1 signaling and differentiation of rat primary esophageal epithelial stem cells [13].

Immobilized growth factors

Many cytokines, including stem cell factor (SCF) and leukemia inhibitory factor (LIF), are presented in a membrane-bound form by supportive cells in the stem cell niche. Further, a large number of growth factors may be sequestered by ECM components including proteoglycans. Diffusible growth factors can also be immobilized in an active conformation. Covalent linkage of LIF to polyester fiber mesh or surfaces coated with poly(octadecene-alt-maleic anhydride) was shown to support expansion of murine ESCs with retention of ESC markers [14,15]. Covalent binding of fibroblast growth factor (FGF)-2 to polyamide nanofibrillar surfaces inhibited the rapid degradation of FGF-2 in solution and supported expansion and colony formation of human ESCs [16]. Strong noncovalent interactions can also be used to immobilize cytokines in an active form, as illustrated by the attachment of biotinylated SCF to biotinylated polyethylene glycol (PEG) chains via a NeutrAvidin linker [17] and attachment of a fusion protein of vascular endothelial growth factor (VEGF)121 and the collagen-binding domain of fibronectin to surfaces coated with gelatin or collagen [18]. Iwata and colleagues developed a multi-domain chimeric protein that contains epidermal growth factor (EGF), ciliary neurotrophic factor (CNTF), a globular capping domain that blocks CNTF activity (linked via a thrombin cleavage sequence), and a decahistidine linker that binds to surface-immobilized Ni(II) ions [19]. Rat neural stem cells (NSCs) cultured on surfaces containing the full chimeric protein expanded in number and maintained 85% undifferentiated cells. However, ca. 70% of the cells differentiated into astrocytes on surfaces treated with thrombin to expose the CNTF domain [19].

Cell-ECM interactions

Fibronectin effects on stem cells have been extensively studied. Covalently linking fibronectin to aminated polyethylene terephthalate (PET) film supported 10-fold greater expansion of CB CD34+ cells than tissue culture polystyrene (TCPS) or unmodified PET [20]. Fibronectin has multiple cell-binding domains that may be differentially displayed when fibronectin is adsorbed. Fibronectin fragments and peptide mimics, such as those containing RGD (ligand for α5β1 and other integrins) and LDV (α4β1 integrin), have been used to study the effects of individual domains. CB CD34+ cells cultured in serum-free medium (SFM) for 10 days on LDV linked to a PET film contained twice as many cells able to initiate long-term hematopoiesis in vitro (LTCICs) as those cultured on PET controls and supported low levels of engraftment in 3 of 4 lethally irradiated immunodeficient mice [21]. Surfaces modified with RGD or control peptides did not support engraftment in mice, but produced only 20% fewer LTC-ICs than those with LDV [21].

Several laminin cell-binding domain peptide mimics have been evaluated in stem cell cultures. Human adipose stem cells adhered and spread more extensively on poly(caprolactone) (PCL)-based scaffolds covalently linked to IKVAV, as compared to the laminin-derived peptides RGD or YIGSR [22]. Rat adult hippocampal progenitor (AHP) cells cultured for 8 days on IKVAV peptides covalently linked to a supported phospholipid bilayer showed similar expansion and retention of undifferentiated state as AHP cells cultured on polyornithine/laminin adsorbed to SiO2 [23]. However, cells on IKVAV-presenting surfaces formed a network of interconnecting colonies, while cells were evenly distributed on laminin [23]. Derda et al. evaluated a wide variety of laminin peptides presented in self-assembled monolayers on gold for their ability to support human ESC adhesion and proliferation [**24]. The IKVAV and RGD peptides showed variable results. However, four different peptides from the laminin γ chain and one peptide from the β chain supported ESC expansion and expression of the primitive markers Oct4, alkaline phosphatase, and SSEA4 to a similar extent as Matrigel in 6-day cultures [**24].

Covalently linked GAGs support stem and progenitor cells. Partially thiolated hyalauronic acid (HA) conjugated to polydopamine-functionalized polystyrene supported adhesion and proliferation of the megakaryoblastic M07e cell line [25]. PCL and polylactide surfaces conjugated with heparin supported high-affinity adsorption of BMP-2, as well as adhesion and proliferation of the C3H10T1/2 murine mesenchymal stem cell (MSC) line [26]. PEG hydrogels functionalized with heparin sustained human MSC viability and induced osteogenic differentiation [27].

Presentation of multiple ligands enhances surface functionality and more closely mimics the niche. Immobilization of fibronectin peptide mimics RGD and LDV additively increased M07e cell adhesion [17], while presenting both HA and tropocollagen I synergistically increased adhesion of CD133+ cells from mobilized peripheral blood [28]. A multi-domain peptide containing two IKVAV sequences, a heparin-binding sequence from laminin, and a hydrophobic sequence for stable adsorption to polystyrene supported greater adhesion of C2C12 pluripotent murine myoblasts than IKVAV alone and also supported the BMP-2-induced osteogenic differentiation of MC3T3-E1 murine osteoprogenitors [29]. Sol-gel-derived thin films incorporating RGD from fibronectin and YIGSR from laminin – with or without NID – supported the retinoic acid-induced differentiation of P19 embryonic carcinoma stem cells to neurons and astrocytes [*30]. Cultures on RGD/YIGSR/(NID) produced more astrocytes and fewer neurons, but longer neurite extensions, than those on collagen [*30]. Nakajima et al. used microlithography and derivatized alkanethiols on gold to evaluate combinations of covalently linked ECM components and growth factors on fetal rat NSC differentiation [**31]. Although the growth factor effects predominated (e.g., EGF-induced maintenance of NSCs and NGF-induced neural differentiation), the ECM also played a role, as illustrated by much less extensive NT-3-induced neural and CNTF-induced astroglial differentiation on laminin vs. fibronectin [**31]. Maruyama et al. immobilized extracellular domains from membrane-bound signaling molecules and evaluated their effects on the outgrowth of thalamocortical axons [*32]. Axon growth was promoted or inhibited depending on the combination, concentrations, and spatial distribution of the signaling molecules and the presence of proteins from the upper (laminin) or deep (N-cadherin) layers of the developing cortex [*32].

Matrix stiffness

Organs and tissues have been adapted for their function and vary in stiffness due to differences in ECM composition, crosslink density, and mineralization. Cell membrane mechanical properties also differ with cell type and differentiation stage. For example, human MSC membranes are twice as stiff as those of osteoblasts, but MSCs extend much longer tethers than osteoblasts [33]. While substrate compliance is known to influence mature cell function, stem cell responses have not been studied extensively. Hsiong et al. showed that the stiffness of alginate hydrogels functionalized with RGD had little effect on the growth of the clonally derived D1 murine MSC line, but that more mature MC3T3-E1 cells and D1 cells induced to differentiate down the osteogenic pathway exhibited greater growth rates on alginate disks with greater stiffness [34]. Heterogeneous human MSCs also showed higher growth rates on stiffer gels [34]. Engler et al. used collagen-coated polyacrylamide gels with elastic moduli similar to brain (1 kPa), muscle (10 kPa), and collagen (100 kPa) to show that substrate stiffness alters human MSC differentiation even in the absence of soluble inducers [**35]. The MSCs exhibited a neuron-like phenotype on soft gels, myoblast-like morphology on substrates of intermediate stiffness, and an osteoblast-like phenotype on the stiffest gels. Soluble inducing factors synergized with matrix stiffness to increase lineage-specific gene expression [**35].

Topography

Cells in vivo are exposed to diverse topographies including fibrous ECM and rough mineralized bone. Murine ESCs cultured on electrospun polyamide nanofibers that mimic basement membrane texture yielded 2-fold greater cell expansion than on coverslips, while retaining Nanog expression and differentiation potential [36]. Binding fibronectin to PET fiber scaffolds increased CB CD34+ cell expansion 5-fold compared to that on PET films and produced cells that reconstituted hematopoiesis in immunodeficient mice [20]. CB CD34+ cells cultured in SFM for 10 days on polyethersulfone (PES) nanofibers functionalized with C2- or C4-tethered amino groups supported similar total cell expansion as did cultures on TCPS, but the PES nanofibers yielded 4-fold greater CD34+ cell expansion and 50% greater LTC-IC production [**37]. After transplantation into lethally irradiated immunodeficient mice, cells cultured on the nanofibers resulted in 5-fold greater human cell content than fresh cells or cells cultured on TCPS [**37]. Diblock co-polymers of polystyrene and poly-2-vinylpyrindine or poly-4- vinylpyrindine formed dot-like (6 nm) or worm-like (3 nm) surface nanotopography, respectively, via controlled microphase separation [38]. The worm-like surfaces supported greater human MSC proliferation, more elongated cells, and thicker ECM deposits [38]. Charest et al. used hot embossing to create patterns in polycarbonate surfaces coated with fibronectin; surfaces with parallel 5–75 µm grooves resulted in preferential alignment of C2C12 and primary myoblasts, but did not affect cell expansion or differentiation compared to smooth surfaces or those arrayed with 5–75 µm holes [39]. When nanogrooves were superimposed perpendicular to the microgrooves, MC3T3-E1 cell bodies aligned with the microgrooves, but many cell processes aligned with the nanogrooves [40].

Oxygen gradients

Stem cell niches are often located in regions of low oxygen tension and low pO2 typically decreases the rate of stem cell differentiation and enhances stem cell proliferative potential (reviewed in [41]). Murine fetal cortical neural progenitor cells expanded in culture at 2–5% O2, but declined at 20% O2 [42]. Oligodendrocyte progenitors, but not committed neuronal progenitors, exhibited more extensive apoptosis at 20% O2 [42]. It has recently been proposed that oxidative stress suppresses N-cadherin-mediated HSC adhesion to osteoblasts and induces HSCs to exit the niche [43]. CD34+ cells in CB are normally exposed to higher pO2 values than those in bone marrow. Exposure of CB CD34+ cells to 2% O2 significantly decreased their survival compared to that at 20% O2, but cell death was substantially decreased by engagement of the α4β1 integrin [44].

It is difficult to control pO2 at low levels. Park et al. have developed a microfabrication-based approach to pattern a wide variety of oxidative microgradients by using titanium/platinum microelectrodes arranged along intricate geometries to generate O2 via electrolysis [*45]. Rat C2C12 myoblasts, which undergo apoptosis and differentiation under high pO2, were used to confirm the predicted gradients [*45].

Patterning cells and ligands

The stem cell niche exhibits a distribution of different cell types and ligands. Lee et al. used photolithography and inkjet printing to control homogeneous and heterogeneous cell-cell interactions; the number of hepatic (HepG2) cells in a cluster was controlled by varying the size of collagen islands from 30 (1 cell) to 100 µm (ca. 20 cells) and the intervening space was filled with 3T3 fibroblasts [46]. Patterning has also been used to induce several differentiation fates in a single culture. Phillipi et al. created islands of immobilized BMP-2 on a fibrin matrix and showed that muscle-derived stem cells cultured in a myogenic medium differentiated into osteogenic cells within the BMP-2 islands, while those in the surrounding area formed multinucleated myotubes [47].

Receptors are not uniformly distributed on stem cells. It has been shown that lipid rafts help to regulate HSC cycling and that blocking receptor clustering interferes with cytokine signaling [48]. Therefore, it will be important to modulate ligand patterns within a single-cell scale. Doh and Irvine immobilized biotinylated anti-CD3 antibody and ICAM-1 to polymer thin films in patterns that resemble the immunological synapse [*49]. When randomly migrating T-cells encountered a patterned synapse, they changed from polarized to rounded morphology and became activated [*49]. Presentation on fluid lipid surfaces allows for cell-directed reorganization of ligands. Thid et al. covalently linked IKVAV peptide to palmitoyl-oleyl-phosphocholine (POPC) and presented this within a fluid supported POPC bilayer [50]. AHP cell attachment to IKVAV-POPC was sigmoidal with a threshold of 3 pmol/cm2 and maximal binding at 8 pmol/cm2, and was essentially the same as attachment to IKVAV covalently linked to tethered PEG chains [50]. Nam et al. showed that MCF-10a mammary epithelial cells cultured on a fluid supported lipid bilayer reorganized lipid-linked EGF into large clusters over a period of several hours [51].

Toward the future

While progress has been made to increase the frequency of adult stem cell renewal, we are still far from reaching the goal of selective and sustained expansion of tissue-specific stem cells. Many different factors must be presented in the correct arrangement and orientation within a well-defined 3-dimensional construct of defined stiffness and topography in the presence of pO2 and growth factor gradients in order to mimic the complexity of the stem cell niche. While it will probably not be necessary to mimic all aspects of the niche to greatly increase stem cell self-renewal, it will almost certainly be necessary to simultaneously mimic multiple components of the niche. The advances discussed above provide a foundation for evaluating a wide range of combinations of different immobilized factors on materials with varying compliance and texture. A recent discovery has enabled the covalent modification of virtually any material using the biocompatible adhesive coating polydopamine [25]. This coating is prepared from aqueous solution and is amenable for patterning and conjugation with molecules containing free amines or thiol groups. Another recent study has demonstrated the patterning of fluid lipid domains within a background of covalently linked fibronectin [52]. This will allow for the simultaneous presentation of immobilized and mobile ligands. The approaches and technologies described in this review provide ideas and tools for multi-parameter design of improved stem cell culture systems.

Acknowledgements

This work was supported in part by NIH grant HL-074151. We thank Mark Seniw for creating Figure 1.

Footnotes

Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Contributor Information

Shara M. Dellatore, Email: sdellatore@u.northwestern.edu.

A. Sofia Garcia, Email: asgarcia@u.northwestern.edu.

William M. Miller, Email: wmmiller@northwestern.edu.

References

  • 1.Mimeault M, Hauke R, Batra SK. Stem cells: A revolution in therapeutics - Recent advances in stem cell biology and their therapeutic applications in regenerative medicine and cancer therapies. Clinical Pharmacology & Therapeutics. 2007;82:252–264. doi: 10.1038/sj.clpt.6100301. [DOI] [PubMed] [Google Scholar]
  • 2.Fuchs E, Tumbar T, Guasch G. Socializing with the neighbors: Stem cells and their niche. Cell. 2004;116:769–778. doi: 10.1016/s0092-8674(04)00255-7. [DOI] [PubMed] [Google Scholar]
  • 3.Morrison SJ, Spradling AC. Stem cells and niches: Mechanisms that promote stem cell maintenance throughout life. Cell. 2008;132:598–611. doi: 10.1016/j.cell.2008.01.038. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Hines M, Nielsen L, Cooper-White J. The hematopoietic stem cell niche: what are we trying to replicate? Journal of Chemical Technology and Biotechnology. 2008;83:421–443. [Google Scholar]
  • 5.McDevitt T, Palecek S. Innovation in the Culture Practices of Pluripotent Human Stem Cells for Therapeutic Applications. Current Opinion in Biotechnology. 2008 doi: 10.1016/j.copbio.2008.08.005. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 6.Khademhosseini A, Langer R, Borenstein J, Vacanti JP. Microscale technologies for tissue engineering and biology. Proceedings of the National Academy of Sciences of the United States of America. 2006;103:2480–2487. doi: 10.1073/pnas.0507681102. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7.Dawson E, Mapili G, Erickson K, Taqvi S, Roy K. Biomaterials for stem cell differentiation. Advanced Drug Delivery Reviews. 2008;60:215–228. doi: 10.1016/j.addr.2007.08.037. [DOI] [PubMed] [Google Scholar]
  • 8.Chai C, Leong KW. Biomaterials approach to expand and direct differentiation of stem cells. Molecular Therapy. 2007;15:467–480. doi: 10.1038/sj.mt.6300084. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9.Jin ZG, Kirilly D, Weng CJ, Kawase E, Song XQ, Smith S, Schwartz J, Xie T. Differentiation-defective stem cells outcompete normal stem cells for niche occupancy in the Drosophila ovary. Cell Stem Cell. 2008;2:39–49. doi: 10.1016/j.stem.2007.10.021. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • *10. Nagaoka M, Ise H, Harada I, Koshimizu U, Maruyama A, Akaike T. Embryonic undifferentiated cells show scattering activity on a surface coated with immobilized E-cadherin. Journal of Cellular Biochemistry. 2008;103:296–310. doi: 10.1002/jcb.21406. Undifferentiated embryonic carcinoma cells form compact aggregates mediated by E-cadherin interactions on non-adhesive surfaces and the aggregates remained intact when plated on collagen or fibronectin. However, when aggregates were plated on surfaces coated with a fusion protein of E-cadherin and the Fc domain of IgG1, cell-cell adhesion was disrupted and the cells migrated to form a scattered array of individual cells with E-cadherin-rich protrusions.
  • *11. Suzuki T, Yokoyama Y, Kumano K, Takanashi M, Kozuma S, Takato T, Nakahata T, Nishikawa M, Sakano S, Kurokawa M, et al. Highly efficient ex vivo expansion of human hematopoietic stem cells using Delta1-Fc chimeric protein. Stem Cells. 2006;24:2456–2465. doi: 10.1634/stemcells.2006-0258. Immobilizing a fusion protein of Delta1 and the Fc domain of IgG1 synergized with adsorbed fibronectin and soluble cytokines to double the production of mixed-lineage colonies in cultures of cord blood CD133+ cells. Culture with Delta1-Fc under optimal conditions expanded cells able to reconstitute irradiated mice by 5-fold; the bone marrow of transplant recipients contained 50% human cells including 1% CD34+CD133+ cells.
  • 12.Kertesz Z, Vas V, Kiss J, Urban VS, Pozsonyi E, Kozma A, Paloczi K, Uher F. In vitro expansion of long-term repopulating hernatopoietic stem cells in the presence of immobilized Jagged-1 and early acting cytokines. Cell Biology International. 2006;30:401–405. doi: 10.1016/j.cellbi.2005.11.011. [DOI] [PubMed] [Google Scholar]
  • 13.Beckstead BL, Santosa DM, Giachelli CM. Mimicking cell-cell interactions at the biomaterial-cell interface for control of stem cell differentiation. Journal of Biomedical Materials Research Part A. 2006;79A:94–103. doi: 10.1002/jbm.a.30760. [DOI] [PubMed] [Google Scholar]
  • 14.Cetinkaya G, Turkoglu H, Arat S, Odaman H, Onur MA, Gumusderelioglu M, Tumer A. LIF-immobilized nonwoven polyester fabrics for cultivation of murine embryonic stem cells. Journal of Biomedical Materials Research Part A. 2007;81A:911–919. doi: 10.1002/jbm.a.31107. [DOI] [PubMed] [Google Scholar]
  • 15.Alberti K, Davey RE, Onishi K, George S, Salchert K, Seib FP, Bornhäuser M, Pompe T, Nagy A, Werner C, et al. Functional immobilization of signaling proteins enables control of stem cell fate. Nature Methods. 2008;5:645–650. doi: 10.1038/nmeth.1222. [DOI] [PubMed] [Google Scholar]
  • 16.Nur-E-Kamal A, Ahmed I, Kamal J, Babu AN, Schindler M, Meiners S. Covalently attached FGF-2 to three-dimensional polyamide nanofibrillar surfaces demonstrates enhanced biological stability and activity. Molecular and Cellular Biochemistry. 2008;309:157–166. doi: 10.1007/s11010-007-9654-8. [DOI] [PubMed] [Google Scholar]
  • 17.Gunawan RC, King JA, Lee BP, Messersmith PB, Miller WM. Surface presentation of bioactive Ligands in a nonadhesive background using DOPA-Tethered biotinylated poly(ethylene glycol) Langmuir. 2007;23:10635–10643. doi: 10.1021/la701415z. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Ishikawa T, Eguchi M, Wada M, Iwami Y, Tono K, Iwaguro H, Masuda H, Tamaki T, Asahara T. Establishment of a functionally active collagen-binding vascular endothelial growth factor fusion protein in situ. Arteriosclerosis Thrombosis and Vascular Biology. 2006;26:1998–2004. doi: 10.1161/01.ATV.0000233359.74484.77. [DOI] [PubMed] [Google Scholar]
  • 19.Nakaji-Hirabayashi T, Kato K, Arima Y, Iwata H. Multifunctional chimeric proteins for the sequential regulation of neural stem cell differentiation. Bioconjugate Chemistry. 2008;19:516–524. doi: 10.1021/bc700355t. [DOI] [PubMed] [Google Scholar]
  • 20.Feng Q, Chai C, Jiang XS, Leong KW, Mao HQ. Expansion of engrafting human hematopoietic stem/progenitor cells in three-dimensional scaffolds with surface-immobilized fibronectin. Journal of Biomedical Materials Research Part A. 2006;78A:781–791. doi: 10.1002/jbm.a.30829. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21.Jiang XS, Chai C, Zhang Y, Zhuo RX, Mao HQ, Leong KW. Surface-immobilization of adhesion peptides on substrate for ex vivo expansion of cryopreserved umbilical cord blood CD34(+) cells. Biomaterials. 2006;27:2723–2732. doi: 10.1016/j.biomaterials.2005.12.001. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 22.Santiago LY, Nowak RW, Rubin JP, Marra KG. Peptide-surface modification of poly(caprolactone) with laminin-derived sequences for adipose-derived stem cell applications. Biomaterials. 2006;27:2962–2969. doi: 10.1016/j.biomaterials.2006.01.011. [DOI] [PubMed] [Google Scholar]
  • 23.Thid D, Holm K, Eriksson PS, Ekeroth J, Kasemo B, Gold J. Supported phospholipid bilayers as a platform for neural progenitor cell culture. Journal of Biomedical Materials Research Part A. 2008;84A:940–953. doi: 10.1002/jbm.a.31358. [DOI] [PubMed] [Google Scholar]
  • **24. Derda R, Li LY, Orner BP, Lewis RL, Thomson JA, Kiessling LL. Defined substrates for human embryonic stem cell growth identified from surface arrays. Acs Chemical Biology. 2007;2:347–355. doi: 10.1021/cb700032u. Surface array containing peptide-alkane thiols was used to screen for laminin-derived peptides that support formation of confluent and undifferentiated ESC colonies, as assessed by staining for alkaline phosphatase and Oct4. Peptide amphiphile fiber scaffolds displaying the identified peptides supported proliferation of Oct4+ ESCs.
  • 25.Lee H, Dellatore SM, Miller WM, Messersmith PB. Mussel-inspired surface chemistry for multifunctional coatings. Science. 2007;318:426–430. doi: 10.1126/science.1147241. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Edlund U, Danmark S, Albertsson AC. A strategy for the covalent functionalization of resorbable polymers with heparin and osteoinductive growth factor. Biomacromolecules. 2008;9:901–905. doi: 10.1021/bm701267u. [DOI] [PubMed] [Google Scholar]
  • 27.Benoit DSW, Durney AR, Anseth KS. The effect of heparin-functionalized PEG hydrogels on three-dimensional human mesenchymal stem cell osteogenic differentiation. Biomaterials. 2007;28:66–77. doi: 10.1016/j.biomaterials.2006.08.033. [DOI] [PubMed] [Google Scholar]
  • 28.Franke K, Pompe T, Bornhauser M, Werner C. Engineered matrix coatings to modulate the adhesion of CD133+ human hematopoietic progenitor cells. Biomaterials. 2007;28:836–843. doi: 10.1016/j.biomaterials.2006.09.031. [DOI] [PubMed] [Google Scholar]
  • 29.Lin X, Takahashi K, Liu Y, Zamora PO. Enhancement of cell attachment and tissue integration by a IKVAV containing multi-domain peptide. Biochimica Et Biophysica Acta-General Subjects. 2006;1760:1403–1410. doi: 10.1016/j.bbagen.2006.05.010. [DOI] [PubMed] [Google Scholar]
  • *30. Jedlicka SS, Little KM, Nivens DE, Zemlyanov D, Rickus JL. Peptide ormosils as cellular substrates. Journal of Materials Chemistry. 2007;17:5058–5067. Peptide silanes were incorporated using sol-gel reaction chemistry to form organically modified silica surfaces or ormosils. Because peptide silanes are added in a tetramethoxysilane solution before dip coating the substrate, different combinations and concentrations of peptides can be covalently attached to the sol-gel matrix.
  • **31. Nakajima M, Ishimuro T, Kato K, Ko IK, Hirata I, Arima Y, Iwata H. Combinatorial protein display for the cell-based screening of biomaterials that direct neural stem cell differentiation. Biomaterials. 2007;28:1048–1060. doi: 10.1016/j.biomaterials.2006.10.004. Different combinations of covalently immobilized extracellular matrix components and growth factors were evaluated for neural stem cell (NSC) self-renewal and differentiation using cell-based arrays. After two days, cells were assayed for proliferation and markers for NSCs and neural or astroglial differentiation.
  • *32. Maruyama T, Matsuura M, Suzuki K, Yamamoto N. Cooperative activity of multiple upper layer proteins for thalamocortical axon growth. Developmental Neurobiology. 2008;68:317–331. doi: 10.1002/dneu.20592. Rat thalamic explants were cultured on surfaces that displayed periodic 200-µm wide bands (spaced 2 mm apart) containing different combinations of fusion proteins of the human IgG Fc domain and the extracellular domain of selected membrane-associated signaling molecules within a background of proteins found in the upper (laminin) or deep (N-cadherin) layer of the developing cortex.
  • 33.Titushkin I, Cho M. Modulation of cellular mechanics during osteogenic differentiation of human mesenchymal stem cells. Biophysical Journal. 2007;93:3693–3702. doi: 10.1529/biophysj.107.107797. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 34.Hsiong SX, Carampin P, Kong HJ, Lee KY, Mooney DJ. Differentiation stage alters matrix control of stem cells. Journal of Biomedical Materials Research Part A. 2008;85A:145–156. doi: 10.1002/jbm.a.31521. [DOI] [PubMed] [Google Scholar]
  • **35. Engler AJ, Sen S, Sweeney HL, Discher DE. Matrix elasticity directs stem cell lineage specification. Cell. 2006;126:677–689. doi: 10.1016/j.cell.2006.06.044. Mesenchymal stem cells (MSCs) were cultured on collagen-coated gels of varying stiffness. MRNA expression profiles, cytoskeletal markers, and transcription factor expression patterns suggest that lineage-specific differentiation of MSCs is induced by matrix stiffness that matches the respective tissue – soft matrices are neurogenic, rigid matrices are osteogenic and intermediate matrices are myogenic.
  • 36.Nur-E-Kamal A, Ahmed I, Kamal J, Schindler M, Meiners S. Three-dimensional nanofibrillar surfaces promote self-renewal in mouse embryonic stem cells. Stem Cells. 2006;24:426–433. doi: 10.1634/stemcells.2005-0170. [DOI] [PubMed] [Google Scholar]
  • **37. Chua KN, Chai C, Lee PC, Ramakrishna S, Leong KW, Mao HQ. Functional nanofiber scaffolds with different spacers modulate adhesion and expansion of cryopreserved umbilical cord blood hematopoietic stem/progenitor cells. Experimental Hematology. 2007;35:771–781. doi: 10.1016/j.exphem.2007.02.002. Demonstrated the promise of aminated nanofiber mesh topography for increased CD34+ cell expansion and engraftment potential of the cultured cells. Adhesion of individual nearly spherical cells to the nanofibers (via numerous uropodia) was much greater than that to tissue culture polystyrene.
  • 38.Khor HL, Kuan Y, Kukula H, Tamada K, Knoll W, Moeller M, Hutmacher DW. Response of cells on surface-induced nanopatterns: Fibroblasts and mesenchymal progenitor cells. Biomacromolecules. 2007;8:1530–1540. doi: 10.1021/bm0611533. [DOI] [PubMed] [Google Scholar]
  • 39.Charest JL, Garcia AJ, King WP. Myoblast alignment and differentiation on cell culture substrates with microscale topography and model chemistries. Biomaterials. 2007;28:2202–2210. doi: 10.1016/j.biomaterials.2007.01.020. [DOI] [PubMed] [Google Scholar]
  • 40.Eliason MT, Charest JL, Simmons BA, Garcia AJ, King WP. Nanoimprint fabrication of polymer cell substrates with combined microscale and nanoscale topography. Journal of Vacuum Science & Technology B. 2007;25:L31–L34. [Google Scholar]
  • 41.King JA, Miller WM. Bioreactor development for stem cell expansion and controlled differentiation. Current Opinion in Chemical Biology. 2007;11:394–398. doi: 10.1016/j.cbpa.2007.05.034. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 42.Chen HL, Pistollato F, Hoeppner DJ, Ni HT, Mckay RDG, Panchision DM. Oxygen tension regulates survival and fate of mouse central nervous system precursors at multiple levels. Stem Cells. 2007;25:2291–2301. doi: 10.1634/stemcells.2006-0609. [DOI] [PubMed] [Google Scholar]
  • 43.Hosokawa K, Arai F, Yoshihara H, Nakamura Y, Gomei Y, Iwasaki H, Miyamoto K, Shima H, Ito K, Suda T. Function of oxidative stress in the regulation of hematopoietic stem cell-niche interaction. Biochemical and Biophysical Research Communications. 2007;363:578–583. doi: 10.1016/j.bbrc.2007.09.014. [DOI] [PubMed] [Google Scholar]
  • 44.Dao MA, Creer MH, Nolta JA, Verfaillie CM. Biology of umbilical cord blood progenitors in bone marrow niches. Blood. 2007;110:74–81. doi: 10.1182/blood-2006-08-034447. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • *45. Park J, Bansal T, Pinelis M, Maharbiz MM. A microsystem for sensing and patterning oxidative microgradients during cell culture. Lab on a Chip. 2006;6:611–622. doi: 10.1039/b516483d. Microfabricated electrodes embedded in gas-permeable microchannels were used to generate precise doses of oxygen via electrolysis. Microgradients generated by different microelectrodes in an array were superimposed to pattern a diverse range of oxygen profiles in 1 mm × 1 mm culture chambers.
  • 46.Lee JY, Shah SS, Zimmer CC, Liu GY, Revzin A. Use of photolithography to encode cell adhesive domains into protein microarrays. Langmuir. 2008;24:2232–2239. doi: 10.1021/la702883d. [DOI] [PubMed] [Google Scholar]
  • 47.Phillippi JA, Miller E, Weiss L, Huard J, Waggoner A, Campbell P. Microenvironments engineered by inkjet bioprinting spatially direct adult stem cells toward muscle- and bone-like subpopulations. Stem Cells. 2008;26:127–134. doi: 10.1634/stemcells.2007-0520. [DOI] [PubMed] [Google Scholar]
  • 48.Yamazaki S, Iwama A, Takayanagi SI, Morita Y, Eto K, Ema H, Nakauchi H. Cytokine signals modulated via lipid rafts mimic niche signals and induce hibernation in hematopoietic stem cells. Embo Journal. 2006;25:3515–3523. doi: 10.1038/sj.emboj.7601236. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • *49. Doh J, Irvine DJ. Immunological synapse arrays: Patterned protein surfaces that modulate immunological synapse structure formation in T cells. Proceedings of the National Academy of Sciences of the United States of America. 2006;103:5700–5705. doi: 10.1073/pnas.0509404103. Mimics of the immunological synapse were created using photolithography to immobilize islands of activating anti-CD3 antibody (T-cell receptor ligand) within a sea of immobilized ICAM-1. Various island structures were evaluated including a circle, an annulus, and an array of four small circles.
  • 50.Thid D, Bally M, Holm K, Chessari S, Tosatti S, Textor M, Gold J. Issues of ligand accessibility and mobility in initial cell attachment. Langmuir. 2007;23:11693–11704. doi: 10.1021/la701159u. [DOI] [PubMed] [Google Scholar]
  • 51.Nam JM, Nair PM, Neve RM, Gray JW, Groves JT. A fluid membrane-based soluble ligand-display system for live-cell assays. Chembiochem. 2006;7:436–440. doi: 10.1002/cbic.200500479. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 52.Jackson BL, Groves JT. Hybrid protein-lipid patterns from aluminum templates. Langmuir. 2007;23:2052–2057. doi: 10.1021/la062667q. [DOI] [PubMed] [Google Scholar]

RESOURCES