Cartilage regeneration using arthroscopic flushing fluid-derived mesenchymal stem cells encapsulated in a one-step rapid cross-linked hydrogel.

Many attempts have been made to repair articular cartilage defects, including mesenchymal stem cell (MSC)-based tissue engineering strategies. Although this approach shows promise, optimizing MSC sources and their delivery is challenging. This study was designed to test the feasibility of using MSCs found in the human arthroscopic flushing fluid (AFF) for cartilage regeneration, by incorporating them into a newly developed one-step rapid cross-linking hyper-branched polyPEGDA/HA hydrogel. AFF-MSCs were isolated from the original intra-articular flushing fluid of 10 patients prior to arthroscopic procedures. The hydrogel was fabricated with hyper-branched polyPEGDA and thiolated hyaluronic acid (HA). In vitro assays demonstrated that AFF-MSCs possessed the typical MSC morphology and phenotype, and maintained chondrogenic differentiation properties when encapsulated within the hydrogel. The AFF-MSC/hydrogel composite could significantly repair full-thickness cartilage defects generated in a rat model after 8 weeks of implantation; smooth cartilage was formed with evidence of hyaline cartilage formation. These data suggest that human AFF-MSCs are a novel and abundant MSC source that have high therapeutic value for cartilage regeneration. STATEMENT OF SIGNIFICANCE: Many attempts have been made to repair the defects of articular cartilage, including mesenchymal stem cell (MSC)-based tissue engineering strategies. Optimizing MSC sources and their delivery approaches still remain clinically challenging. Recent studies determined that MSCs derived from synovium and synovial fluid exhibited superior chondrogenic potential. However, no feasible methods to harvest these human tissues and cells have been impeding them for clinical application. Hereby, we explored a simple and easy accessible approach to obtain a new stem cell source from arthroscopic flushing fluid (AFF-MSCs), which probably contains plenty of MSCs from synovium and synovial fluid. Further experiments demonstrated that encapsulation of these stem cells with one-step rapid cross-linked polyPEGDA/HA hydrogel held very encouraging potential for cartilage regeneration.