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Designer, injectable gels to prevent transplanted Schwann cell loss during spinal cord injury therapy.

ABSTRACT: Transplantation of patient-derived Schwann cells is a promising regenerative medicine therapy for spinal cord injuries; however, therapeutic efficacy is compromised by inefficient cell delivery. We present a materials-based strategy that addresses three common causes of transplanted cell death: (i) membrane damage during injection, (ii) cell leakage from the injection site, and (iii) apoptosis due to loss of endogenous matrix. Using protein engineering and peptide-based assembly, we designed injectable hydrogels with modular cell-adhesive and mechanical properties. In a cervical contusion model, our hydrogel matrix resulted in a greater than 700% improvement in successful Schwann cell transplantation. The combination therapy of cells and gel significantly improved the spatial distribution of transplanted cells within the endogenous tissue. A reduction in cystic cavitation and neuronal loss were also observed with substantial increases in forelimb strength and coordination. Using an injectable hydrogel matrix, therefore, can markedly improve the outcomes of cellular transplantation therapies.

SUBMITTER: Marquardt LM

PROVIDER: S-EPMC7112763 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Designer, injectable gels to prevent transplanted Schwann cell loss during spinal cord injury therapy.

Marquardt Laura M LM Doulames Vanessa M VM Wang Alice T AT Dubbin Karen K Suhar Riley A RA Kratochvil Michael J MJ Medress Zachary A ZA Plant Giles W GW Heilshorn Sarah C SC

Science advances 20200401 14

Transplantation of patient-derived Schwann cells is a promising regenerative medicine therapy for spinal cord injuries; however, therapeutic efficacy is compromised by inefficient cell delivery. We present a materials-based strategy that addresses three common causes of transplanted cell death: (i) membrane damage during injection, (ii) cell leakage from the injection site, and (iii) apoptosis due to loss of endogenous matrix. Using protein engineering and peptide-based assembly, we designed inj ...[more]

PMID: 32270042

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Project description:Immediately following spinal cord injury, further injury can occur through several secondary injury cascades. As a consequence of cell lysis, an increase in extracellular Ca(2+) results in additional neuronal loss by inducing apoptosis. Thus, hydrogels that reduce extracellular Ca(2+) concentration may reduce secondary injury severity. The goal of this study was to develop composite hydrogels consisting of alginate, chitosan, and genipin that interact with extracellular Ca(2+) to enable in situ gelation while maintaining an elastic modulus similar to native spinal cord (∼1000 Pa). It was hypothesized that incorporation of genipin and chitosan would regulate hydrogel electrostatic characteristics and influence hydrogel porosity, degradation, and astrocyte behavior. Hydrogel composition was varied to create hydrogels with statistically similar mechanical properties (∼1000 Pa) that demonstrated tunable charge characteristics (6-fold range in free amine concentration) and degradation rate (complete degradation between 7 and 28 days; some blends persist after 28 days). Hydrogels demonstrate high sensitivity to Ca(2+) concentration, as a 1 mM change during fabrication induced a significant change in elastic modulus. Additionally, hydrogels incubated in a Ca(2+)-containing solution exhibited an increased linear viscoelastic limit (LVE) and an increased elastic modulus above the LVE limit in a time dependent manner. An extension of the LVE limit implies a change in hydrogel cross-linking structure. Attachment assays demonstrated that addition of chitosan/genipin to alginate hydrogels induced up to a 4-fold increase in the number of attached astrocytes and facilitated astrocyte clustering on the hydrogel surface in a composition dependent manner. Furthermore, Western blots demonstrated tunable glial fibrillary acid protein (GFAP) expression in astrocytes cultured on hydrogel blends, with some hydrogel compositions demonstrating no significant increase in GFAP expression compared to astrocytes cultured on glass. Thus, alginate/chitosan/genipin hydrogel composites show promise as scaffolds that regulate astrocyte behavior and for the prevention of Ca(2+)-related secondary neuron damage during acute SCI.

Project description:The transplantation of Schwann cells (SCs) has been shown to provide tissue preservation and support axon growth and remyelination as well as improve functional recovery across a diverse range of experimental spinal cord injury (SCI) paradigms. The autologous use of SCs has progressed to Phase 1 SCI clinical trials in humans where their use has been shown to be both feasible and safe. The contribution of immune modulation to the protective and reparative actions of SCs within the injured spinal cord remains largely unknown. In the current investigation, the ability of SC transplants to alter the innate immune response after contusive SCI in the rat was examined. SCs were intraspinally transplanted into the lesion site at 1 week following a thoracic (T8) contusive SCI. Multicolor flow cytometry and immunohistochemical analysis of specific phenotypic markers of pro- and anti-inflammatory microglia and macrophages as well as cytokines at 1 week after SC transplantation was employed. The introduction of SCs significantly attenuated the numbers of cluster of differentiation molecule 11B (CD11b)?, cluster of differentiation molecule 68 (CD68)?, and ionized calcium-binding adapter molecule 1 (Iba1)? immune cells within the lesion implant site, particularly those immunoreactive for the pro-inflammatory marker, inducible nitric oxide synthase (iNOS). Whereas numbers of anti-inflammatory CD68? Arginase-1 (Arg1?) iNOS- cells were not altered by SC transplantation, CD68? cells of an intermediate, Arg1? iNOS? phenotype were increased by the introduction of SCs into the injured spinal cord. The morphology of Iba1? immune cells was also markedly altered in the SC implant, being elongated and in alignment with SCs and in-growing axons versus their amoeboid form after SCI alone. Examination of pro-inflammatory cytokines, tumor necrosis factor-? (TNF-?) and interleukin-1? (IL-1?), and anti-inflammatory cytokines, interleukin-4 (IL-4) and interleukin-10 (IL-10), by multicolor flow cytometry analysis showed that their production in CD11b? cells was unaltered by SC transplantation at 1 week post-transplantation. The ability of SCs to subdue the pro-inflammatory iNOS? microglia and macrophage phenotype after intraspinal transplantation may provide an important contribution to the neuroprotective effects of SCs within the sub-acute SCI setting.

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Designer, injectable gels to prevent transplanted Schwann cell loss during spinal cord injury therapy.

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Designer, injectable gels to prevent transplanted Schwann cell loss during spinal cord injury therapy.

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