Among the many extraordinary features of nervous system development, one of the most fascinating is the ability to grow [[axon]]s to navigate through a complex cellular embryonic terrain to find appropriate synaptic partners that may be millimeters or even centimeters away.
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Functional [[restoration]] following major [[peripheral nerve injury]] (PNI) is challenging, given slow [[axon growth]] rates and eventual [[regenerative]] [[pathway]] [[degradation]] in the absence of [[axon]]s. Smith et al. from the Center for Brain Injury and Repair, Department of Neurosurgery, [[Perelman School of Medicine]], [[Axonova Medical]] are developing [[tissue-engineered nerve graft]]s (TENGs) to simultaneously "bridge" missing [[nerve]] [[segment]]s and "babysit" regenerative capacity by providing living [[axon]]s to guide host axons and maintain the distal pathway. TENGs were biofabricated using [[porcine]] [[neuron]]s and "stretch-grown" axon [[tract]]s. TENG neurons survived and elicited axon-facilitated axon [[regeneration]] to accelerate regrowth across both short (1 cm) and long (5 cm) segmental nerve defects in [[pig]]s. TENG axons also closely interacted with host [[Schwann cell]]s to maintain pro-regenerative capacity. TENGs drove regeneration across 5-cm defects in both [[motor]] and mixed motor-sensory nerves, resulting in dense [[axon regeneration]] and electrophysiological recovery at levels similar to [[autograft]] repairs. This approach of accelerating [[axon regeneration]] while maintaining the pathway for long-distance regeneration may achieve recovery after currently unrepairable PNIs
((Smith DH, Burrell JC, Browne KD, Katiyar KS, Ezra MI, Dutton JL, Morand JP, Struzyna LA, Laimo FA, Chen HI, Wolf JA, Kaplan HM, Rosen JM, Ledebur HC, Zager EL, Ali ZS, Cullen DK. [[Tissue]]-engineered [[graft]]s exploit [[axon]]-facilitated [[axon regeneration]] and [[pathway]] protection to enable recovery after 5-cm nerve defects in [[pig]]s. Sci Adv. 2022 Nov 4;8(44):eabm3291. doi: 10.1126/sciadv.abm3291. Epub 2022 Nov 4. PMID: 36332027.)).