Scanning electron microscopy analysis of synovial and adipose mesenchymal stem cells adhering to cartilage.

Introduction: Mesenchymal stem cells (MSCs) are increasingly used for intra-articular injections in the treatment of knee osteoarthritis. The aim of this study was to use scanning electron microscopy (SEM) to compare the morphological characteristics of synovial and adipose MSCs.

Methods: Synovium and adipose tissues were concurrently harvested from eight patients with knee osteoarthritis. Suspensions of both synovial and adipose MSCs were examined to identify the presence of microspikes. In addition to this study, the MSC suspensions in four patients were applied to abraded porcine cartilage discs and observed 10 s, 10 min, and 1 h later.

Results: The median percentage of cells exhibiting microspikes was 14% for synovial MSC suspensions and 13% for adipose MSC suspensions; this difference was not statistically significant (n = 8). No notable differences were detected in the number of adherent cells or in the proportion of cells displaying microspikes or pseudopodia. Strong correlations were found between the proportion of cells with pseudopodia and the number of attached cells for both synovial (r = 0.92, n = 12) and adipose (r = 0.86, n = 12) MSCs, with no significant difference in the correlation coefficients between the two groups.

Conclusion: SEM analysis revealed no obvious differences in morphological characteristics during MSC adhesion to cartilage for either synovial or adipose MSCs.