A standardized and characterized clinical grade human platelet lysate for efficient expansion of human bone marrow mesenchymal stem cells

Human platelet lysate (hPL) is rich in growth factors (GF) and nutritive elements and represents a powerful xeno-free alternative to fetal bovine serum (FBS) notably for mesenchymal stem cell (hMSC) proliferation. However, there is a large variability in hPL sources and production protocols, resulting in discrepancies in product quality, low management of product safety and poor batch-to-batch standardization. We describe here the development and the characterization of a standardized hPL prepared from outdated transfusional grade screened normal human donor platelet concentrates (PCs), manufactured on an industrial scale (batch sizes of 10 L; 250 donors) and following a highly qualified process (clean room, trained operators, validated aseptic filtration). PCs were frozen at −80°C and thawed at +4°C to lyse platelets. Cell debris were removed by centrifugation and the supernatant (hPL) was recovered. Clinical grade 10L batches of aseptic filtered hPL were characterized. First, we showed that hPL prepared from a limited number of donors displayed a variability in terms of GF contents. On the contrary, we observed a robust standardization between 10L-industrial batches of hPL in terms of GF contents (bFGF, EGF, VEGF, PDGF-AB, TGF-beta1 and IGF-1), biochemical analyses (total proteins, albumin, fibrinogen and iron) and efficacy on bone marrow (BM)-hMSC proliferation. Secondly, we compared expansion and functional characteristics of BM-hMSCs grown in clinical grade hPL versus MSC-screened FBS batch. We showed a reproducible increase in cell growth kinetics using hPL, a maintenance of BM-hMSC clonogenic potential and membrane marker expression (with however a strong overexpression of CD90). We observed a similar adipogenic and osteogenic differentiation potential and finally that immunosuppressive properties of BM-hMSCs (inhibition of T-cell proliferation) cultivated in parallel in both conditions remained also identical. Finally, we documented the stability over time of hPL stored at −80°C and −20°C. In conclusion, we demonstrated the feasibility to use a standardized, efficient and clinical grade hPL for research and cell therapy applications.