An injectable, self-healing, electroconductive hydrogel loaded with neural stem cells and donepezil for enhancing local therapy effect of spinal cord injury

Abstract

Background Spinal 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 have positive effects in promoting neurological recovery, such as drug intervention and stem cell transplantation. Although those treatments are effective for nerve regeneration, many drawbacks have limited their development, such as low stem cell survival rates and side effects caused by systemic medication. 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, which can overcome the defects existing in traditional drugs and stem cell therapy. Method In this study, a novel injectable electroactive hydrogel (NGP) based on sodium hyaluronate oxide (SAO) and polyaniline-grafted gelatin (NH2-Gel-PANI) was developed to load neural stem cells (NSCs) and donepezil (DPL) to facilitate nerve regeneration post-SCI. To evaluate the potential of the prepared NGP hydrogel in SCI repair application, the surface morphology, self-repairing properties, electrical conductivity and cytocompatibility of the resulting hydrogel were analyzed. Meanwhile, we evaluated the neural repair ability of NGP hydrogels loaded with DPL and NSCs using a rat model of spinal cord injury. Result The NGP hydrogel has a suitable pore size, good biocompatibility, excellent conductivity, injectable and self-repairing properties, and its degradation rate matches the repair cycle of spinal cord injury. At the same time, DPL could be released continuously and slowly in the NGP hydrogel; thus, the NGP hydrogel could be used as an excellent carrier of drugs and cells. The results of in vitro cell experiments showed that the NGP hydrogel had good cytocompatibility and could significantly promote neuronal differentiation and axon growth of NSCs, and the hydrogel loaded with DPL could significantly enhance this effect. More importantly, the NGP hydrogel loaded with DPL showed a significant inhibitory effect on astrocyte differentiation of NSCs in vitro. Animal experiments show that the combination of NGP hydrogel + DPL + NSCs group showed the best therapeutic effect on the recovery of motor function and nerve conduction function in rats. NGP hydrogel-loaded 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. Conclusions The DPL and NSCs-laden electroactive hydrogel developed in this study is an ideal biomaterial for the treatment of traumatic spinal cord injury.