Proteomic analysis of the secretome of adipose tissue-derived murine mesenchymal cells overexpressing telomerase and myocardin

Rationale: Understanding mechanisms of the therapeutic effects of stem/progenitor cells, among which adipose tissue-derived mesenchymal stromal cells (AT-MSCs), has important implications for clinical use. Since the majority of such cells die within days or weeks after transplantation and do not persist in the transplanted organ or tissue, their effects appear to be largely mediated by paracrine signaling pathways, and are enhanced by overexpression of the antisenescent protein telomerase reverse transcriptase (TERT), and the anti-apoptotic transcription factor myocardin (MYOCD). Aim: By a proteomic approach combining two-dimensional gel electrophoresis (2DE)with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF/TOF)mass spectrometry, we aimed at analyzing how soluble and vesicular secretomes of aged murine AT-MSCs and their angiogenic function are modulated by the overexpression of TERT and MYOCD. Methods: We cultured murine mock-transduced AT-MSCs and “rejuvenated” AT-MSCs overexpressing TERT and MYOCD (rTMAT-MSCs)harvested from 1-year-old male C57BL/6 mice. We established proteomes from 3 mock-transduced AT-MSCs and rTMAT-MSCs cultures in serum-free conditions, as well as their corresponding conditioned medium (CM)and exosome-enriched fractions (Exo+). Results and conclusions: Proteomic analysis revealed a 2-fold increase of matrix metalloproteinase-2 (MMP-2)and its inhibitor metalloproteinase inhibitor 2 (TIMP2)in the CM - but not in the Exo + − of rTMAT-MSCs as compared to mock-transduced AT-MSCs. At the functional level, rTMAT-MSCs-CM, and – to a lesser extent – its Exo + fraction, increased tube formation of human vein endothelial cells (HUVECs), which could be blocked by anti-MMP2 and enhanced by anti-TIMP2 antibodies, respectively. Altogether, our results identify MMP2 and its inhibitor TIMP2 as novel candidates by which rTMAT-MSCs can support angiogenesis. Our strategy also illustrates the usefulness of comparative targeted proteomic approach to decipher molecular pathways underlying rTMAT-MSCs properties