# Evaluation of an AD-MSC Supernatant-Loaded Thermosensitive Hydrogel for Cartilage Protection in Osteoarthritis

## TL;DR

A new injectable hydrogel loaded with stem cell supernatant helps protect cartilage and reduce inflammation in knee osteoarthritis.

## Contribution

A cell-free, thermosensitive hydrogel for sustained delivery of AD-MSC supernatant to treat osteoarthritis is developed and tested.

## Key findings

- The hydrogel transitioned from a solution to a gel at body temperature without crosslinkers.
- The treatment reduced inflammation and cartilage degeneration in a rat model of KOA.
- Proinflammatory cytokines and cartilage degradation markers were significantly decreased.

## Abstract

Knee osteoarthritis (KOA) is a degenerative joint disorder characterized by chronic inflammation and progressive cartilage degradation. Mesenchymal stem cell (MSC)-based therapies have demonstrated therapeutic potential; however, increasing evidence suggests that their efficacy primarily arises from paracrine factors, highlighting the potential of cell free approaches. In this study, we developed an injectable, thermosensitive composite hydrogel incorporating adipose-derived MSC (AD-MSC) supernatant within a Pluronic F-127 (PF-127)/sodium hyaluronate (HA) matrix. The hydrogel exhibited a solution state at a low temperature and rapidly transitioned into a stable gel at a physiological temperature without chemical crosslinkers. Microstructural analysis revealed a porous, interconnected three-dimensional network favorable for the sustained release of bioactive factors. In a rat model of KOA, intra-articular administration of the AD-MSC supernatant-loaded hydrogel significantly improved joint architecture and locomotor performance, alleviated synovial inflammation, and preserved cartilage integrity. Radiographic and histological assessments demonstrated reduced cartilage degeneration and subchondral bone alterations. Moreover, the treatment markedly decreased intra-articular levels of proinflammatory cytokines (IL-1β and TNF-α) and the cartilage degradation marker CTX-II in a time-dependent manner. These findings indicated that the sustained local delivery of AD-MSC-derived supernatant effectively modulated joint inflammation and attenuated cartilage degeneration, with the hydrogel serving primarily as a delivery vehicle for these bioactive factors. This cell-free injectable biomaterial platform could offer a promising therapeutic strategy for the treatment of knee osteoarthritis.