# Neural Markers Predict Tendon Healing Outcomes in an Ovine Achilles Tendon Injury Model: Spontaneous Repair Versus Amniotic Epithelial Cell-Induced Regeneration

## TL;DR

Neural markers like NGF, CGRP, and GAL predict successful tendon healing in sheep, especially when amniotic cells are used.

## Contribution

Identifies NGF, CGRP, and GAL as predictive biomarkers for tendon regeneration outcomes in an ovine model.

## Key findings

- AEC-treated tendons showed enhanced ECM remodeling and better collagen maturation.
- NGF, CGRP, and GAL correlated positively with improved tissue organization in AEC-treated tendons.
- Lower levels of NGF, CGRP, and GAL predicted better healing outcomes in AEC-treated tissues.

## Abstract

Tendon injuries pose a clinical challenge due to tendons’ limited recovery. Emerging evidence points to the nervous system’s critical role in tendon healing, with neural markers NGF, NF-200, NPY, CGRP, and GAL modulating inflammation, cell proliferation, and extracellular matrix (ECM) remodeling. This study investigates the predictive role of selected neural markers in a validated ovine Achilles tendon injury model, comparing spatio-temporal expression patterns in regenerating tendons transplanted with amniotic epithelial stem cells (AECs) versus spontaneous healing (CTR) 14 and 28 days post-injury (p.i.). AEC-treated tissues showed a spatio-temporal modulation of NF-200, NGF, NPY, CGRP, GAL, and enhanced ECM remodeling, with greater cell alignment, lower angle deviation, and accelerated collagen maturation, with a favorable Collagen type 1 (COL1) to Collagen type 3 (COL3) ratio. Pearson’s matrix analysis revealed significant positive correlations between NGF, CGRP, and GAL expression, along a positive correlation between the three neural markers and cell alignment and angle deviation. As opposed to CTR, in AEC-treated tendons, lower levels of NGF, CGRP, and GAL correlated positively with improved tissue organization, suggesting these markers may predict successful tendon regeneration. The findings highlight the neuro-mediated activity of AECs in tendon regeneration, with NGF, CGRP, and GAL emerging as key predictive biomarkers for tendon healing.