Anti-Calcification Effects of Immortalized Human Adipose Tissue-Derived Mesenchymal Stem/Stromal Cell (HATMSC2) Secretome in an In Vitro Model of Vascular Calcification

Vascular calcification (VC) is a very common complication associated with aging, chronic kidney disease, diabetes, and atherosclerosis, predicting cardiovascular morbidity and mortality, but remains largely resistant to current therapies. This study investigated the anti-calcification properties of a secretome derived from a human adipose tissue-derived mesenchymal stem/stromal cell line (HATMSC2) using an in vitro model of vascular smooth muscle cell (VSMC) calcification. VSMCs were cultured in both inorganic and organic calcification media with or without HATMSC2 secretome supplementation (50 μg/mL). Calcium deposition was assessed with Alizarin Red S staining, while osteogenic markers (RUNX2, OPN, OSX, COL-1, OCN) and contractile marker α-SMA were evaluated with Western blot and RT-PCR. The HATMSC2 secretome significantly reduced calcium deposits and suppressed the upregulation of osteogenic markers in the organic calcification model, preventing osteogenic transdifferentiation. Furthermore, the secretome significantly decreased the adhesion of the THP-1 monocyte to VSMCs under calcification-promoting conditions, confirming its immunomodulatory effects. The detection of BMP antagonists, GREM1 and CHRDL1, MGP (anti-calcification factor), and the BMP signaling agonist BMP-7 in the HATMSC2-derived secretome indicates factors that may potentially contribute to its anti-calcification activity. These findings are consistent with the modulation of osteogenic signaling pathways; however, the precise molecular mechanisms and the individual contribution of the identified proteins require further functional validation.