Synovial mesenchymal stem cells secrete more lubricin than adipose mesenchymal stem cells after injection into rat osteoarthritis knees.

Intra-articular injection of mesenchymal stem cells (MSCs) is envisioned as a solution for knee osteoarthritis (OA). Although synovial MSCs (SyMSCs) are promising for cartilage regeneration, the clinical choice is usually adipose MSCs (AdMSCs). However, the similarities/differences in the mode of action between SyMSCs and AdMSCs remain unclear. Here, we compared factors secreted by human SyMSCs and AdMSCs after injection into OA knees. Human SyMSCs or AdMSCs were injected into the knees of rat partial meniscectomy models. The next day, the knee joints were collected to analyze the distribution of injected MSCs and transcriptome changes in the human MSCs and rat synovium. Non-injected MSCs were mixed with rat synovium as a control. After injection, no difference was apparent in intra-articular distribution of the SyMSCs or AdMSCs. RNA sequencing demonstrated an enrichment of cytokine-cytokine receptor interaction-related genes in both human SyMSCs and AdMSCs after injection. Differentially expressed genes (DEGs) specific to SyMSCs were associated with cartilage matrix synthesis and homeostasis. PCR analysis of the matrisome-related DEGs showed significantly higher expression of PRG4 in SyMSCs than in AdMSCs after injection. Immunostaining also confirmed a significantly greater expression of lubricin by SyMSCs than by AdMSCs. These findings indicate that SyMSCs will be a more promising treatment for OA.

Synovial mesenchymal stem cells promote meniscus regeneration augmented by an autologous Achilles tendon graft in a rat partial meniscus defect model.

Although meniscus defects and degeneration are strongly correlated with the later development of osteoarthritis, the promise of regenerative medicine strategies is to prevent and/or delay the disease's progression. Meniscal reconstruction has been shown in animal models with tendon grafting and transplantation of mesenchymal stem cells (MSCs); however, these procedures have not shown the same efficacy in clinical studies. Here, our aim was to investigate the ability of tendon grafts pretreated with exogenous synovial-derived MSCs to prevent cartilage degeneration in a rat partial meniscus defect model. We removed the anterior half of the medial meniscus and grafted autologous Achilles tendons with or without a 10-minute pretreatment of the tendon with synovial MSCs. The meniscus and surrounding cartilage were evaluated at 2, 4, and 8 weeks (n = 5). Tendon grafts increased meniscus size irrespective of synovial MSCs. Histological scores for regenerated menisci were better in the tendon + MSC group than in the other two groups at 4 and 8 weeks. Both macroscopic and histological scores for articular cartilage were significantly better in the tendon + MSC group at 8 weeks. Implanted synovial MSCs survived around the grafted tendon and native meniscus integration site by cell tracking assays with luciferase+, LacZ+, DiI+, and/or GFP+ synovial MSCs and/or GFP+ tendons. Flow cytometric analysis showed that transplanted synovial MSCs retained their MSC properties at 7 days and host synovial tissue also contained cells with MSC characteristics. Synovial MSCs promoted meniscus regeneration augmented by autologous Achilles tendon grafts and prevented cartilage degeneration in rats.

Comparison of the yields and properties of dedifferentiated fat cells and mesenchymal stem cells derived from infrapatellar fat pads.

Introduction: Infrapatellar fat pad (IFP)-derived mesenchymal stem cells (MSCs) have high chondrogenic potential and are attractive cell sources for cartilage regeneration. During ceiling culture to acquire the characteristics of MSCs, mature adipocytes from fat tissue are known to undergo dedifferentiation, generating dedifferentiated fat (DFAT) cells. The purpose of the present study was to compare the yields and biological properties of IFP-derived MSCs and IFP-derived DFAT cells. Methods: IFPs were harvested from the knees of 8 osteoarthritis (OA) patients. DFAT cells were obtained using a ceiling culture of adipocytes isolated from the floating top layer of IFP digestion. MSCs were obtained by culturing precipitated stromal vascular fraction cells. We compared the P0 cell yields, surface antigen profile, colony formation ability, and multipotency of DFAT cells and MSCs. Results: The P0 cell yields per flask and the estimated total cell yields from 1 g of IFP were much greater for MSCs than for DFAT cells. Both MSCs and DFAT cells were positive for MSC markers. No obvious difference was observed in colony formation ability. In differentiation assays, DFAT cells produced greater amounts of lipid droplets, calcified tissue, and glycosaminoglycan than MSCs did. Adipogenic and chondrogenic gene expressions were upregulated in DFAT cells. Conclusions: IFP-derived DFAT cells showed higher adipogenic and chondrogenic potentials than IFP-derived MSCs, but they had a poor cell yield.