Effect of Platelet Lysate on the Functional and Molecular Characteristics of Mesenchymal Stem Cells Isolated from Adipose Tissue

Background: Mesenchymal stem cells (MSCs) are non-hematopoietic, adult, fibroblast-like, multipotent cells that are plastic adherent in standard culture conditions. They can be isolated from several tissues, but it is always necessary to expand them for clinical practice. Aim: We investigated the effect of human platelet lysate (hPL) on the expansion of human MSCs isolated from adipose tissue (AT), comparing it with fetal bovine serum (FBS) and human platelet-poor plasma (hPPP). Materials and Methods: Human AT-MSCs, hPL and hPPP were obtained from 7 healthy subjects. AT-MSCs were seeded at 1500 cells/cm(2) and cultured in Dulbecco's modified Eagle's medium supplemented with 10% FBS, 10% hPPP or 10% hPL. Cells were harvested, counted and analyzed by flow cytometry every 7 days for 5 passages (P). The differentiation assays, RNA isolation and co-culture with allogeneic lymphocytes were performed at the end of P2. Results: AT-MSCs achieved a better proliferation rate when cultured with hPL than with hPPP or FBS (20 +/- 2 versus 8 +/- 3 and 6 +/- 3, respectively, at the end of P5 [p<0.01]). hPL preserved the differentiation capacity and typical expression of surface antigens, avoiding the risks associated with the use of animal derivatives. AT-MSCs demonstrated a stronger inhibitory effect on lymphocyte proliferation with hPL than with other culture conditions, even at a AT-MSCs: T cells ratio of 1:10. The transcriptional level of matrix metalloproteinase 2, used to evaluate stemness, was very high in all conditions tested. Conclusions: hPL represents an effective and safe supplement for MSC expansion to be used in the clinical setting.