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An injectable heparin-Laponite hydrogel bridge FGF4 for spinal cord injury by stabilizing microtubule and improving mitochondrial function.

ABSTRACT: Rationale: Spinal cord injury (SCI) remains a critical clinical challenge. The controlled release of FGF4, a novel neuroprotective factor, from a versatile Laponite hydrogel to the injured site was a promising strategy to promote axon regeneration and motor functional recovery after SCI. Methods: Characterization of Laponite, Laponite/Heparin (Lap/Hep) and Laponite/Heparin loaded with FGF4 (Lap/Hep@FGF4) hydrogels were measured by rheometer. Multiple comprehensive evaluations were used to detect motor functional recovery and the axonal rehabilitation after Lap/Hep@FGF4 treatment in vivo (SCI rat model). Moreover, microtubule dynamic and energy transportation, which regulated axonal regeneration was evaluated by Lap/Hep@FGF4 gel in vitro (primary neuron). Results: FGF4 released from Lap/Hep gel locally achieves strong protection and regeneration after SCI. The Lap/Hep@FGF4 group revealed remarkable motor functional recovery and axonal regrowth after SCI through suppressing inflammatory reaction, increasing remyelination and reducing glial/fibrotic scars. Furthermore, the underlying mechanism of axonal rehabilitation were demonstrated via enhancing microtubule stability and regulating mitochondrial localization after Lap/Hep@FGF4 treatment. Conclusion: This promising sustained release system provides a synergistic effective approach to enhance recovery after SCI underlying a novel mechanism of axonal rehabilitation, and shows a translational prospect for the clinical treatment of SCI.

SUBMITTER: Wang C

PROVIDER: S-EPMC6815951 | biostudies-literature |

REPOSITORIES: biostudies-literature

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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:BackgroundSpinal cord injury (SCI) is a serious injury with high mortality and disability rates, and there is no effective treatment at present. It has been reported that some treatments, such as drug intervention and stem cell transplantation have positive effects in promoting neurological recovery. Although those treatments are effective for nerve regeneration, many drawbacks, such as low stem cell survival rates and side effects caused by systemic medication, have limited their development. In recent years, injectable hydrogel materials have been widely used in tissue engineering due to their good biocompatibility, biodegradability, controllable properties, and low invasiveness. The treatment strategy of injectable hydrogels combined with stem cells or drugs has made some progress in SCI repair, showing the potential to overcome the drawbacks of traditional drugs and stem cell therapy.MethodsIn this study, a novel injectable electroactive hydrogel (NGP) based on sodium hyaluronate oxide (SAO) and polyaniline-grafted gelatine (NH2-Gel-PANI) was developed as a material in which to load neural stem cells (NSCs) and donepezil (DPL) to facilitate nerve regeneration after SCI. To evaluate the potential of the prepared NGP hydrogel in SCI repair applications, the surface morphology, self-repairing properties, electrical conductivity and cytocompatibility of the resulting hydrogel were analysed. Meanwhile, we evaluated the neural repair ability of NGP hydrogels loaded with DPL and NSCs using a rat model of spinal cord injury.ResultsThe NGP hydrogel has a suitable pore size, good biocompatibility, excellent conductivity, and injectable and self-repairing properties, and its degradation rate matches the repair cycle of spinal cord injury. In addition, DPL could be released continuously and slowly from the NGP hydrogel; thus, the NGP hydrogel could serve as an excellent carrier for drugs and cells. The results of in vitro cell experiments showed that the NGP hydrogel had good cytocompatibility and could significantly promote the neuronal differentiation and axon growth of NSCs, and loading the hydrogel with DPL could significantly enhance this effect. More importantly, the NGP hydrogel loaded with DPL showed a significant inhibitory effect on astrocytic differentiation of NSCs in vitro. Animal experiments showed that the combination of NGP hydrogel, DPL, and NSCs had the best therapeutic effect on the recovery of motor function and nerve conduction function in rats. NGP hydrogel loaded with NSCs and DPL not only significantly increased the myelin sheath area, number of new neurons and axon area but also minimized the area of the cystic cavity and glial scar and promoted neural circuit reconstruction.ConclusionsThe DPL- and NSC-laden electroactive hydrogel developed in this study is an ideal biomaterial for the treatment of traumatic spinal cord injury.

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An injectable heparin-Laponite hydrogel bridge FGF4 for spinal cord injury by stabilizing microtubule and improving mitochondrial function.

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