Early morphological and gene/protein expression dynamics of human synovial mesenchymal stem cells during adhesion to...

Synovial mesenchymal stem cells (MSCs) are a potential therapeutic option for meniscal injuries; however, the early cellular events following MSC application remain obscure. This study aimed to characterize the morphological and molecular changes occurring during the first 24 h after application of human synovial MSCs onto a structurally disrupted meniscal surface. MSCs were seeded onto a frozen-thawed, mechanically abraded meniscal surface under non-inflammatory conditions, and MSC morphology and gene/protein expression were evaluated before adhesion and at 1 h and 24 h after seeding. Scanning electron microscopy revealed MSCs with a round morphology and pseudopodia at 1 h, but flattened cells and multilayer formation at 24 h. MSCs attaching to nonbiological substrates showed similar time-dependent morphological changes. Gene expression analysis demonstrated time-dependent changes in CD44, BMP2, PRG4, TIMP1, TSG6, and integrin-related genes, including increased ITGA2 expression and decreased ITGA11 and ITGA4 expression at 24 h. Immunofluorescence staining detected these proteins before and after adhesion. These findings indicate that synovial MSCs undergo rapid morphological and transcriptional changes during early adhesion. Although these changes may partly reflect general adhesion-related processes, the results provide a descriptive framework for understanding the early behavior of MSCs upon application to a structurally disrupted, devitalized meniscal matrix surface.