Arthroscopic repair of full-thickness cartilage defects in horses with autologous nasal chondrocytes seeded in an injectable hydrogel: from preclinical development to clinical cases

Abstract

This study aimed at evaluating the ability of autologous equine nasal chondrocytes (EqNCs) embedded in a silanised hydroxypropyl methylcellulose (Si-HPMC) hydrogel to repair cartilage defects in horses. Autologous EqNCs from the nasal septum were cultured in vitro and mixed with Si-HPMC. This hybrid construct was injected arthroscopically to experimental full-thickness critical-sized cartilage defects in a pilot horse. After this preliminary test, it was implanted in 6 experimental horses and compared with microfracture (positive control) and with debridement only (negative control) using experimental defects created bilaterally on radial carpal bones and medial femoral condyles. Cartilage tissue repair was subsequently investigated arthroscopically, macroscopically and histologically 18 months after the surgical procedure. Two client-owned horses presenting with cartilage damage were also treated using hybrid EqNCs/Si-HPMC constructs. We developed an injection technique for a 3D hybrid construct of EqNC and Si-HPMC under gas arthroscopy. The in situ reticulation and adhesion properties of the construct ensured its stability after injection. The hybrid construct was well tolerated and Si-HPMC was estimated as a safe scaffold for horses. We found a better cartilage healing with our hybrid construct compared to microfracture or defect left empty characterized by an increased type II collagen content in the defects filled with the hybrid construct. In the 2 clinical cases, hybrid construct injection led to the formation of repair tissue exhibiting the gross appearance of articular cartilage and both returned to intended use. This study revealed that EqNCs/Si-HPMC constructs can support the formation of a healing tissue with hyaline cartilage features.