Influence of Stress-Induced Senescence on the Secretome of Primary Mesenchymal Stromal Cells.

Mesenchymal stromal cells (MSCs) are promising therapeutic agents, largely due to their capacity for self-renewal, differentiation, and immunomodulation. Importantly, these beneficial effects are frequently mediated by the MSC secretome, which contains factors with anti-inflammatory, anti-apoptotic, and pro-regenerative properties. However, cellular senescence can impair these critical functions. To identify senescence-associated changes in the MSC secretome that may regulate aging and intercellular communication, we performed a mass spectrometry-based proteomic analysis of the conditioned medium from MSCs undergoing stress-induced senescence. Our analysis confirmed the upregulation of established aging markers, such as IL-6, PAI-1, and IGFBP7. Furthermore, we identified a significant increase in lesser-known senescence-associated secretory phenotype (SASP) components, including INHBA-a known inhibitor of proliferation-and DKK3, which blocks stromal cell pluripotency. Pathway analysis revealed that stress-induced senescence broadly affected proteins involved in glycolysis, immune response, hemostasis, and the regulation of cell death and the cell cycle. These alterations are likely to negatively impact the MSC microenvironment. Interestingly, the cellular response to senescence was dualistic. Alongside detrimental SASP factors, we observed an increase in protective proteins such as annexins (ANXA1, ANXA2), antioxidants (TXN, PRDX1, PRDX6), and the heat shock protein HSPB1, which collectively defend neighboring cells from inflammation and oxidative stress. These findings underscore the complex etiology of cellular senescence and the paradoxical nature of the SASP. The obtained data also emphasize the necessity of comprehensive proteomic profiling of the MSC secretome across different aging models to harness the full therapeutic potential of MSCs and their secretomes for regenerative medicine.