Long-Term Survival and Integration of Transplanted Engineered Nervous Tissue Constructs Promotes Peripheral Nerve Regeneration

Abstract

Although peripheral nerve injury is a common consequence of trauma or surgery, there are insufficient means for repair. In particular, there is a critical need for improved methods to facilitate regeneration of axons across major nerve lesions. Here, we engineered transplantable living nervous tissue constructs to provide a labeled pathway to guide host axonal regeneration. These constructs consisted of stretch-grown, longitudinally aligned living axonal tracts inserted into poly(glycolic acid) tubes. The constructs (allogenic) were transplanted to bridge an excised segment of sciatic nerve in the rat, and histological analyses were performed at 6 and 16 weeks posttransplantation to determine graft survival, integration, and host regeneration. At both time points, the transplanted constructs were found to have maintained their pretransplant geometry, with surviving clusters of graft neuronal somata at the extremities of the constructs spanned by tracts of axons. Throughout the transplanted region, there was an intertwining plexus of host and graft axons, suggesting that the transplanted axons mediated host axonal regeneration across the lesion. By 16 weeks posttransplant, extensive myelination of axons was observed throughout the transplant region. Further, graft neurons had extended axons beyond the margins of the transplanted region, penetrating into the host nerve. Notably, this survival and integration of the allogenic constructs occurred in the absence of immunosuppression therapy. These findings demonstrate the promise of living tissue-engineered axonal constructs to bridge major nerve lesions and promote host regeneration, potentially by providing axon-mediated axonal outgrowth and guidance.

Microtissue Engineered Constructs with Living Axons for Targeted Nervous System Reconstruction

“…Nonetheless, following transplantation the general repair strategy between these two technologies is similar by providing living axons that can bridge damaged regions of the nervous system. Survival and integration of the microconduit constructs following transplantation appears feasible since the stretch-grown constructs have been successfully used for repair of both peripheral nerve 34 and spinal cord injury 35 in rodents.…”

“…[34][35][36][37][38] While promising, the large size of these constructs is not ideal for transplantation into discrete regions of the nervous system.…”

Pluripotent Hair Follicle Neural Crest Stem-Cell-Derived Neurons and Schwann Cells Functionally Repair Sciatic Nerves in Rats

“…This nourishing environment for nerve regeneration is created by neurotrophic factors, including nerve growth factor, ciliary neurotrophic factor, and basic fibroblast growth factor, which are released by proliferating Schwann cells residing in peripheral nerves [28][29][30]. In injured sciatic nerves, dorsal root ganglia neurons can survive to 4 months after transplantation [31], indicating that such a nourishing environment can support neuron survival. Our study observed the survival of hair follicle NCSC-derived neurons in ANXs in vivo by 2, 4, and 52 weeks posttransplantation.…”

Fibrin glue as a stabilization strategy in peripheral nerve repair when using porous nerve guidance conduits

“…Reported benefits include decreased operative time [20], maintenance of correct fascicular orientation [23], improved gross surgical results [20], and minimal neural scarring with reduced fibrosis and inflammation [24]. It is also used widely experimentally, e.g., for stabilizing nerve repairs and for delivering neurotrophic factors [25–29]. In a recent in vivo mouse model study, FG sealant was found to reduce surgical repair time, enhance axonal regeneration and functional recovery [30].…”