Abstract
Purpose
Scaffold materials that better support neurogenesis are still needed to improve cell therapy outcomes for neural tissue damage. We have used a modularly tunable, highly compliant, degradable hydrogel to explore the impacts of hydrogel compliance stiffness on neural differentiation. Here we implemented competitive matrix crosslinking mechanics to finely tune synthetic hydrogel moduli within soft tissue stiffnesses, a range much softer than typically achievable in synthetic crosslinked hydrogels, providing a modularly controlled and ultrasoft 3D culture model which supports and enhances neurogenic cell behavior.
Methods
Soluble competitive allyl monomers were mixed with proteolytically-degradable poly(ethylene glycol) diacrylate derivatives and crosslinked to form a matrix, and resultant hydrogel stiffness and diffusive properties were evaluated. Neural PC12 cells or primary rat fetal neural stem cells (NSCs) were encapsulated within the hydrogels, and cell morphology and phenotype were investigated to understand cell-matrix interactions and the effects of environmental stiffness on neural cell behavior within this model.
Results
Addition of allyl monomers caused a concentration-dependent decrease in hydrogel compressive modulus from 4.40 kPa to 0.26 kPa (natural neural tissue stiffness) without influencing soluble protein diffusion kinetics through the gel matrix. PC12 cells encapsulated in the softest hydrogels showed significantly enhanced neurite extension in comparison to PC12s in all other hydrogel stiffnesses tested. Encapsulated neural stem cells demonstrated significantly greater spreading and elongation in 0.26 kPa alloc hydrogels than in 4.4 kPa hydrogels. When soluble growth factor deprivation (for promotion of neural differentiation) was evaluated within the neural stiffness gels (0.26 kPa), NSCs showed increased neuronal marker expression, indicating early enhancement of neurogenic differentiation.
Conclusions
Implementing allyl-acrylate crosslinking competition reduced synthetic hydrogel stiffness to provide a supportive environment for 3D neural tissue culture, resulting in enhanced neurogenic behavior of encapsulated cells. These results indicate the potential suitability of this ultrasoft hydrogel system as a model platform for further investigating environmental factors on neural cell behavior.
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Data availability
The data that support this published work are available upon request from the corresponding author, RC.
References
Demetri, G. D., et al. Soft tissue sarcoma. J. Natl. Compr. Cancer Netw. 8(6):630–674, 2010.
Gilbert, N. F., et al. Soft-tissue sarcoma. J. Am. Acad. Orthop. Surg. 17(1):40–47, 2009.
Khellaf, A., D. Z. Khan, and A. Helmy. Recent advances in traumatic brain injury. J. Neurol. 266(11):2878–2889, 2019.
Boese, A. C., M. H. Hamblin, and J. P. Lee. Neural stem cell therapy for neurovascular injury in Alzheimer’s disease. Exp. Neurol. 324:113112, 2020.
Alexander, B. M., and T. F. Cloughesy. Adult glioblastoma. J. Clin. Oncol. 35(21):2402–2409, 2017.
Prevention, C.f.D.C.a. Stroke Facts. 2017.
Stroke, N.N.I.o.N.D.a. Stroke Information Page. 2016.
Armour, B. S., et al. Prevalence and causes of paralysis-United States, 2013. Am. J. Public Health. 106(10):1855–1857, 2016.
Hunt, C., et al. Prevalence of chronic pain after spinal cord injury: a systematic review and meta-analysis. Reg. Anesth. Pain Med. 46(4):328–336, 2021.
Burke, D., O. Lennon, and B. M. Fullen. Quality of life after spinal cord injury: the impact of pain. Eur. J. Pain. 22(9):1662–1672, 2018.
Burke, D., et al. Neuropathic pain prevalence following spinal cord injury: A systematic review and meta-analysis. Eur J Pain. 21(1):29–44, 2017.
Chau, M., et al. Transplantation of iPS cell-derived neural progenitors overexpressing SDF-1alpha increases regeneration and functional recovery after ischemic stroke. Oncotarget. 8(57):97537–97553, 2017.
Ahuja, C. S., et al. Traumatic spinal cord injury-repair and regeneration. Neurosurgery. 80(3S):S9–S22, 2017.
Baker, E. W., et al. Induced pluripotent stem cell-derived neural stem cell therapy enhances recovery in an ischemic stroke pig model. Sci. Rep. 7(1):10075, 2017.
Ryu, S., et al. Human neural stem cells promote proliferation of endogenous neural stem cells and enhance angiogenesis in ischemic rat brain. Neural Regen. Res. 11(2):298–304, 2016.
Mine, Y., et al. Grafted human neural stem cells enhance several steps of endogenous neurogenesis and improve behavioral recovery after middle cerebral artery occlusion in rats. Neurobiol. Dis. 52:191–203, 2013.
Stroemer, P., et al. The neural stem cell line CTX0E03 promotes behavioral recovery and endogenous neurogenesis after experimental stroke in a dose-dependent fashion. Neurorehabil. Neural Repair. 23(9):895–909, 2009.
Lam, J., et al. Delivery of iPS-NPCs to the stroke cavity within a hyaluronic acid matrix promotes the differentiation of transplanted cells. Adv. Funct. Mater. 24(44):7053–7062, 2014.
Kelly, S., et al. Transplanted human fetal neural stem cells survive, migrate, and differentiate in ischemic rat cerebral cortex. Proc. Natl. Acad. Sci. U.S.A. 101(32):11839–11844, 2004.
Jeong, S. W., et al. Human neural stem cell transplantation promotes functional recovery in rats with experimental intracerebral hemorrhage. Stroke. 34(9):2258–2263, 2003.
McBride, J. L., et al. Human neural stem cell transplants improve motor function in a rat model of Huntington’s disease. J. Comput. Neurol. 475(2):211–219, 2004.
Lee, I. S., et al. Human neural stem cells alleviate Alzheimer-like pathology in a mouse model. Mol. Neurodegener. 10:38, 2015.
Cui, G. H., et al. Designer self-assemble peptides maximize the therapeutic benefits of neural stem cell transplantation for Alzheimer’s disease via enhancing neuron differentiation and paracrine action. Mol. Neurobiol. 53(2):1108–1123, 2016.
Park, K. I., Y. D. Teng, and E. Y. Snyder. The injured brain interacts reciprocally with neural stem cells supported by scaffolds to reconstitute lost tissue. Nat. Biotechnol. 20(11):1111–1117, 2002.
Zhong, J., et al. Hydrogel matrix to support stem cell survival after brain transplantation in stroke. Neurorehabil. Neural Repair. 24(7):636–644, 2010.
Maclean, F. L., et al. Integrating biomaterials and stem cells for neural regeneration. Stem Cells Dev. 25(3):214–226, 2016.
Lindvall, O., and Z. Kokaia. Recovery and rehabilitation in stroke: stem cells. Stroke. 35(11 Suppl 1):2691–2694, 2004.
Teixeira, A. I., J. K. Duckworth, and O. Hermanson. Getting the right stuff: controlling neural stem cell state and fate in vivo and in vitro with biomaterials. Cell Res. 17(1):56–61, 2007.
Vieira, M. S., et al. Neural stem cell differentiation into mature neurons: mechanisms of regulation and biotechnological applications. Biotechnol. Adv. 36(7):1946–1970, 2018.
Doetsch, F. A niche for adult neural stem cells. Curr. Opin. Genet. Dev. 13(5):543–550, 2003.
Conover, J. C., and R. Q. Notti. The neural stem cell niche. Cell Tissue Res. 331(1):211–224, 2008.
Andreotti, J. P., et al. Neural stem cell niche heterogeneity. Semin. Cell Dev. Biol. 95:42–53, 2019.
Keung, A. J., et al. Rho GTPases mediate the mechanosensitive lineage commitment of neural stem cells. Stem Cells. 29(11):1886–1897, 2011.
Kang, P. H., D. V. Schaffer, and S. Kumar. Angiomotin links ROCK and YAP signaling in mechanosensitive differentiation of neural stem cells. Mol. Biol. Cell. 31(5):386–396, 2020.
Rammensee, S., et al. Dynamics of mechanosensitive neural stem cell differentiation. Stem Cells. 35(2):497–506, 2017.
Baek, J., et al. Egr1 is a 3D matrix-specific mediator of mechanosensitive stem cell lineage commitment. Sci Adv. 8(15):eabm4646, 2022.
Koser, D. E., et al. Mechanosensing is critical for axon growth in the developing brain. Nat. Neurosci. 19(12):1592–1598, 2016.
Song, Y., et al. The mechanosensitive ion channel piezo inhibits axon regeneration. Neuron. 102(2):373–389, 2019.
Gunn, J., S. Turner, and B. Mann. Adhesive and mechanical properties of hydrogels influence neurite extension. J. Biomed. Mater. Res. Part A. 72A(1):9, 2005.
Flanagan, L. A., et al. Neurite branching on deformable substrates. Neuroreport. 13(18):2411–2415, 2002.
Balgude, A. P., et al. Agarose gel stiffness determines rate of DRG neurite extension in 3D cultures. Biomaterials. 22(10):1077–1084, 2001.
Saha, K., et al. Substrate modulus directs neural stem cell behavior. Biophys. J. 95(9):4426–4438, 2008.
Leipzig, N. D., and M. S. Shoichet. The effect of substrate stiffness on adult neural stem cell behavior. Biomaterials. 30(36):6867–6878, 2009.
Banerjee, A., et al. The influence of hydrogel modulus on the proliferation and differentiation of encapsulated neural stem cells. Biomaterials. 30(27):4695–4699, 2009.
Sun, Y., et al. Hippo/YAP-mediated rigidity-dependent motor neuron differentiation of human pluripotent stem cells. Nat. Mater. 13(6):599–604, 2014.
Musah, S., et al. Substratum-induced differentiation of human pluripotent stem cells reveals the coactivator YAP is a potent regulator of neuronal specification. Proc. Natl. Acad. Sci. U.S.A. 111(38):13805–13810, 2014.
Engler, A. J., et al. Matrix elasticity directs stem cell lineage specification. Cell. 126(4):677–689, 2006.
Lam, J., et al. Hydrogel design of experiments methodology to optimize hydrogel for iPSC-NPC culture. Adv. Healthc. Mater. 4(4):534–539, 2015.
Gefen, A., and S. S. Margulies. Are in vivo and in situ brain tissues mechanically similar? J. Biomech. 37(9):1339–1352, 2004.
Taylor, Z., and K. Miller. Reassessment of brain elasticity for analysis of biomechanisms of hydrocephalus. J. Biomech. 37(8):1263–1269, 2004.
Comley, K., and N. A. Fleck. A micromechanical model for the Young’s modulus of adipose tissue. Int. J. Solids Struct. 47(21):2982–2990, 2010.
Young, D. A., et al. Stimulation of adipogenesis of adult adipose-derived stem cells using substrates that mimic the stiffness of adipose tissue. Biomaterials. 34(34):8581–8588, 2013.
Theocharis, A. D., et al. Extracellular matrix structure. Adv. Drug Deliv. Rev. 97:4–27, 2016.
Caliari, S. R., and J. A. Burdick. A practical guide to hydrogels for cell culture. Nat. Methods. 13(5):405–414, 2016.
DeForest, C. A., and K. S. Anseth. Advances in bioactive hydrogels to probe and direct cell fate. Annu. Rev. Chem. Biomol. Eng. 3:421–444, 2012.
Li, X. Engineering neural stem cell fates with hydrogel design for central nervous system regeneration. Prog. Polym. Sci. 37(8):1105–1129, 2012.
Wang, T. W., and M. Spector. Development of hyaluronic acid-based scaffolds for brain tissue engineering. Acta Biomater. 5(7):2371–2384, 2009.
Ma, W., et al. CNS stem and progenitor cell differentiation into functional neuronal circuits in three-dimensional collagen gels. Exp. Neurol. 190(2):276–288, 2004.
Addington, C. P., et al. Enhancing neural stem cell response to SDF-1alpha gradients through hyaluronic acid-laminin hydrogels. Biomaterials. 72:11–19, 2015.
Arulmoli, J., et al. Combination scaffolds of salmon fibrin, hyaluronic acid, and laminin for human neural stem cell and vascular tissue engineering. Acta Biomater. 43:122–138, 2016.
Barros, D., I. F. Amaral, and A. P. Pego. Laminin-inspired cell-instructive microenvironments for neural stem cells. Biomacromolecules. 21(2):276–293, 2020.
Seidlits, S. K., et al. The effects of hyaluronic acid hydrogels with tunable mechanical properties on neural progenitor cell differentiation. Biomaterials. 31(14):3930–3940, 2010.
O’Connor, S. M., et al. Primary neural precursor cell expansion, differentiation and cytosolic Ca(2+) response in three-dimensional collagen gel. J. Neurosci. Methods. 102(2):187–195, 2000.
Nisbet, D.R., et al., Neural Tissue Engineering of the CNS Using Hydrogels - A review (vol 5, pg 293, 2003). Journal of Biomedical Materials Research Part B-Applied Biomaterials, 2009. 88b(1): p. 304-304.
Ju, Y. E., et al. Enhanced neurite growth from mammalian neurons in three-dimensional salmon fibrin gels. Biomaterials. 28(12):2097–2108, 2007.
Mahoney, M. J., et al. Impact of cell type and density on nerve growth factor distribution and bioactivity in 3-dimensional collagen gel cultures. Tissue Eng. 12(7):1915–1927, 2006.
Schweller, R. M., and J. L. West. Encoding hydrogel mechanics via network cross-linking structure. ACS Biomater. Sci. Eng. 1(5):335–344, 2015.
Unal, A. Z., and J. L. West. Synthetic ECM: bioactive synthetic hydrogels for 3D tissue engineering. Bioconjug. Chem. 31(10):2253–2271, 2020.
Zhu, J., and R. E. Marchant. Design properties of hydrogel tissue-engineering scaffolds. Expert Rev. Med. Devices. 8(5):607–626, 2011.
Moore, E. M., G. Ying, and J. L. West. Macrophages influence vessel formation in 3D bioactive hydrogels. Adv. Biosyst. 1(3):16000021, 2017.
Roudsari, L. C., et al. A 3D poly(ethylene glycol)-based tumor angiogenesis model to study the influence of vascular cells on lung tumor cell behavior. Sci. Rep. 6:32726, 2016.
Ali, S., et al. Immobilization of cell-adhesive laminin peptides in degradable PEGDA hydrogels influences endothelial cell tubulogenesis. Biores. Open Access. 2(4):241–249, 2013.
Potter, W., R. E. Kalil, and W. J. Kao. Biomimetic material systems for neural progenitor cell-based therapy. Front. Biosci. 13:806–821, 2008.
Mahoney, M. J., and K. S. Anseth. Three-dimensional growth and function of neural tissue in degradable polyethylene glycol hydrogels. Biomaterials. 27(10):2265–2274, 2006.
Lu, X., et al. Polyethylene glycol in spinal cord injury repair: a critical review. J. Exp. Pharmacol. 10:37–49, 2018.
Mosley, M. C., et al. Neurite extension and neuronal differentiation of human induced pluripotent stem cell derived neural stem cells on polyethylene glycol hydrogels containing a continuous Young’s Modulus gradient. J. Biomed. Mater. Res. A. 105(3):824–833, 2017.
Li, X., et al. Short laminin peptide for improved neural stem cell growth. Stem Cells Transl. Med. 3(5):662–670, 2014.
Hynes, S. R., et al. A library of tunable poly(ethylene glycol)/poly(L-lysine) hydrogels to investigate the material cues that influence neural stem cell differentiation. J. Biomed. Mater. Res. A. 89(2):499–509, 2009.
Naghdi, P., et al. Survival, proliferation and differentiation enhancement of neural stem cells cultured in three-dimensional polyethylene glycol-RGD hydrogel with tenascin. J. Tissue Eng. Regen. Med. 10(3):199–208, 2016.
Barros, D., et al. Engineering hydrogels with affinity-bound laminin as 3D neural stem cell culture systems. Biomater. Sci. 7(12):5338–5349, 2019.
Katz, R. R., and J. L. West. Tunable PEG hydrogels for discerning differential tumor cell response to biomechanical cues. Adv. Biol. (Weinh). 6(12):e2200084, 2022.
Wiley, K. L., et al. Rational design of hydrogel networks with dynamic mechanical properties to mimic matrix remodeling. Adv. Healthc. Mater. 11(7):e2101947, 2022.
Zustiak, S. P., and J. B. Leach. Hydrolytically degradable poly(ethylene glycol) hydrogel scaffolds with tunable degradation and mechanical properties. Biomacromolecules. 11(5):1348–1357, 2010.
Chapla, R., M. Alhaj Abed, and J. West. Modulating functionalized poly(ethylene glycol) diacrylate hydrogel mechanical properties through competitive crosslinking mechanics for soft tissue applications. Polymers (Basel). 12(12):3000, 2020.
Baker, B. M., and C. S. Chen. Deconstructing the third dimension: how 3D culture microenvironments alter cellular cues. J. Cell Sci. 125(Pt 13):3015–3024, 2012.
Magin, C. M., D. L. Alge, and K. S. Anseth. Bio-inspired 3D microenvironments: a new dimension in tissue engineering. Biomed Mater. 11(2):022001, 2016.
Huebsch, N., et al. Harnessing traction-mediated manipulation of the cell/matrix interface to control stem-cell fate. Nat. Mater. 9(6):518–526, 2010.
Tam, R. Y., L. J. Smith, and M. S. Shoichet. engineering cellular microenvironments with photo- and enzymatically responsive hydrogels: toward biomimetic 3D cell culture models. Acc. Chem. Res. 50(4):703–713, 2017.
Blatchley, M. R., and S. Gerecht. Acellular implantable and injectable hydrogels for vascular regeneration. Biomed. Mater. 10(3):034001, 2015.
Reinhard, S. M., K. Razak, and I. M. Ethell. A delicate balance: role of MMP-9 in brain development and pathophysiology of neurodevelopmental disorders. Front. Cell Neurosci. 9:280, 2015.
Matsumoto, A., et al. Reassessment of free-radical polymerization mechanism of allyl acetate based on end-group determination of resulting oligomers by MALDI-TOF-MS spectrometry. Polym. J. 41(1):26–33, 2009.
Deb, P. C. Non-ideal polymerization - treatment of non-ideality due to primary radical termination and degradative chain transfer. Eur. Polym. J. 11(1):31–36, 1975.
Zubov, V. P., et al. Reactivity of allyl monomers in radical polymerization. J. Macromol. Sci. A13(1):111–131, 1979.
Longair, M. H., D. A. Baker, and J. D. Armstrong. Simple Neurite Tracer: open source software for reconstruction, visualization and analysis of neuronal processes. Bioinformatics. 27(17):2453–2454, 2011.
Fan, L., et al. Directing induced pluripotent stem cell derived neural stem cell fate with a three-dimensional biomimetic hydrogel for spinal cord injury repair. ACS Appl. Mater. Interfaces. 10(21):17742–17755, 2018.
Huang, F., Q. Shen, and J. Zhao. Growth and differentiation of neural stem cells in a three-dimensional collagen gel scaffold. Neural Regen. Res. 8(4):313–319, 2013.
Sun, W., et al. Viability and neuronal differentiation of neural stem cells encapsulated in silk fibroin hydrogel functionalized with an IKVAV peptide. J. Tissue Eng. Regen. Med. 11(5):1532–1541, 2017.
Seidlits, S. K., et al. Peptide-modified, hyaluronic acid-based hydrogels as a 3D culture platform for neural stem/progenitor cell engineering. J. Biomed. Mater. Res. A. 107(4):704–718, 2019.
Madl, C. M., et al. Maintenance of neural progenitor cell stemness in 3D hydrogels requires matrix remodelling. Nat. Mater. 16(12):1233–1242, 2017.
Hsieh, F. Y., H. H. Lin, and S. H. Hsu. 3D bioprinting of neural stem cell-laden thermoresponsive biodegradable polyurethane hydrogel and potential in central nervous system repair. Biomaterials. 71:48–57, 2015.
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We acknowledge the National Science Foundation Graduate Research Fellowship Program (NSF GRFP DGE 1644868) and the Duke University Department of Biomedical Engineering for funding this research.
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Chapla, R., Katz, R.R. & West, J.L. Neurogenic Cell Behavior in 3D Culture Enhanced Within a Highly Compliant Synthetic Hydrogel Platform Formed via Competitive Crosslinking. Cel. Mol. Bioeng. 17, 35–48 (2024). https://doi.org/10.1007/s12195-024-00794-2
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DOI: https://doi.org/10.1007/s12195-024-00794-2