The role of secretome from mesenchymal stromal cells in promoting nerve regeneration after neurotmesis

Abstract

Background: Neurotmesis, a severe form of peripheral nerve injury, remains a significant clinical challenge due to limited intrinsic regenerative capacity and suboptimal outcomes of current therapies. Mesenchymal stromal cells (MSCs) secretome has emerged as a promising cell-free alternative, providing neurotrophic and immunomodulatory factors to support nerve repair. This study aimed to evaluate the regenerative efficacy of primed adipose-derived MSC secretome in a rat model of sciatic nerve neurotmesis. Methods: Human and rat adipose-derived MSCs were cultured and primed under hypoxic and inflammatory conditions. Secretomes were characterized by nanoparticle tracking analysis, proteomics, and total protein quantification. Neurotmesis was induced in Wistar rats, followed by repair with biomaterial alone or combined with human or rat secretome. Functional recovery was assessed by neurophysiological measurements at 6 months. Molecular and morphological regeneration was evaluated. Results: Secretome priming enhanced the secretion of neurotrophic factors and immunomodulatory proteins, as confirmed by transcriptomic and proteomic analyses. In vivo, secretome-treated groups showed significantly improved neurophysiological recovery and increased NGF levels. qPCR revealed upregulation of myelination-associated genes in treated nerves. Histological and TEM analyses demonstrated robust axonal regeneration. Conclusions: Primed MSC secretome markedly enhances structural and functional recovery after sciatic nerve neurotmesis, supporting its potential as a safe, effective, and scalable cell-free therapy for peripheral nerve repair.

1. Introduction

Neurotmesis represents a severe form of peripheral nerve injury (PNI) that involves significant challenges for recovery due to the limited intrinsic repair mechanisms of the nervous system [1]. These injuries often result in severe functional deficits, impacting on the quality of life of affected individuals. The process of nerve regeneration involves a series of cellular and molecular events, including inflammation, axonal sprouting, and remyelination, which are crucial for restoring nerve function [2]. Schwann cells (SCs) play a pivotal role in the peripheral nervous system (PNS), facilitating nerve regeneration by producing neurotrophic factors and supporting axonal growth [3]. However, in cases of severe nerve damage, such as neurotmesis, the natural repair process is often insufficient, necessitating therapeutic interventions. Current treatments for PNI include surgical repair, physical therapy, and pharmacological interventions, but these methods have limitations in terms of efficacy and speed of recovery [4, 5].

Recent advancements in tissue engineering and regenerative medicine have highlighted the potential of mesenchymal stem/stromal cells (MSCs) in promoting nerve regeneration [6–9]. MSCs are an ideal cell source for tissue regeneration due to their outstanding properties. They are multipotent stromal cells capable of differentiating into various cell types, including adipocytes, osteoblasts, chondrocytes, myocytes, β-pancreatic islet cells, and potentially neuronal cells [10]. However, recent studies have shown that implanted cells have a limited survival time, and their clinical implementation faces challenges such as immunological incompatibility, tumour formation, and potential infection transmission [11]. New findings have highlighted the diverse range of bioactive factors produced by MSCs, which may play a crucial role in regulating various physiological processes.