Decellularized porcine peripheral nerve based injectable hydrogels as a Schwann cell carrier for injured spinal cord regeneration

Abstract

Objective. To develop a clinically relevant injectable hydrogel derived from decellularized porcine peripheral nerves and with mechanical properties comparable to native central nervous system (CNS) tissue to be used as a delivery vehicle for Schwann cell transplantation to treat spinal cord injury (SCI). Approach. Porcine peripheral nerves (sciatic and peroneal) were decellularized by chemical decellularization using a sodium deoxycholate and DNase (SDD) method previously developed by our group. The decellularized nerves were delipidated using dichloromethane and ethanol solvent and then digested using pepsin enzyme to form injectable hydrogel formulations. Genipin was used as a crosslinker to enhance mechanical properties. The injectability, mechanical properties, and gelation kinetics of the hydrogels were further analyzed using rheology. Schwann cells encapsulated within the injectable hydrogel formulations were passed through a 25-gauge needle and cell viability was assessed using live/dead staining. The ability of the hydrogel to maintain Schwann cell viability against an inflammatory milieu was assessed in vitro using inflamed astrocytes co-cultured with Schwann cells. Main results. The SDD method effectively removes cells and retains extracellular matrix in decellularized tissues. Using rheological studies, we found that delipidation of decellularized porcine peripheral nerves using dichloromethane and ethanol solvent improves gelation kinetics and mechanical strength of hydrogels. The delipidated and decellularized hydrogels crosslinked using genipin mimicked the mechanical strength of CNS tissue. The hydrogels were found to have shear thinning properties desirable for injectable formulations and they also maintained higher Schwann cell viability during injection compared to saline controls. Using in vitro co-culture experiments, we found that the genipin-crosslinked hydrogels also protected Schwann cells from astrocyte-mediated inflammation. Significance. Injectable hydrogels developed using delipidated and decellularized porcine peripheral nerves are a potential clinically relevant solution to deliver Schwann cells, and possibly other therapeutic cells, at the SCI site by maintaining higher cellular viability and increasing therapeutic efficacy for SCI treatment.