A Three-Dimensional Biomimetic In Vitro Model to Simulate Schwann Cell-Mediated Peripheral Nerve Repair

Peripheral nerve injuries represent significant clinical challenges, often resulting in lifelong motor function loss and disability. Evidence suggests regenerating axons cannot cross nerve gaps without Schwann Cell (SC) assistance. However, FDA-approved biomaterial conduits for peripheral nerve repair lack bioactivity and structural complexity needed to facilitate SC migration. To address this, we developed a three-dimensional biomimetic in vitro model to simulate complex cellular interactions within the nerve bridge. The model features lyophilized hydrogel bioscaffolds with longitudinal channels to recapitulate the nerve microenvironment. To encourage directional SC dispersion, the top ~30% of the bioscaffold was conjugated with macrophage inflammatory protein-1α (MIP-1α). Rat SCs were seeded within no-MIP-1α- and MIP-1α-conjugated bioscaffold channels as spheroids and cultured for nine days. Histology demonstrated MIP-1α conjugation retained more SC spheroids during culture with greater cellular distributions. SC spheroid culture in MIP-1α-conjugated bioscaffold resulted in enhanced paracrine signaling characterized by increases in VEGF, ICAM-1, IL-6, and CINC-1 production, alongside downregulation of IL-1β, IL-10, and IL-13. The SC-derived pro-inflammatory and pro-angiogenic mediators did not inhibit NSC-34 motor neurite extension compared to controls. This study establishes an in vitro model that serves as both a screening platform and mechanistic tool, advancing our understanding of peripheral nerve repair.