Fibrinogen-Depleted Equine Platelet Lysate Affects the Characteristics and Functionality of Mesenchymal Stem Cells

Fetal bovine serum (FBS) is widely used to culture mesenchymal stem cells (MSCs) in the laboratory; however, FBS has been linked to adverse immune-mediated reactions prompting the search for alternative cell culture medium. Platelet lysate (PL) as an FBS substitute has been shown to promote MSCs growth without compromising their functionality. Fibrinogen contained in PL has been shown to negatively impact the immune modulating properties of MSCs; therefore, we sought to deplete fibrinogen from PL and compare proliferation, viability, and immunomodulatory capacities of MSCs in FBS or PL without fibrinogen. We depleted fibrinogen from equine platelet lysate (ePL) and measured platelet-derived growth factor-beta (PDGF-β), transforming growth factor-beta (TGF-β) and tumor necrosis factor-alpha (TNF-α) through ELISA. First, we determined the ability of 10% ePL or fibrinogen-depleted lysate (fdePL) compared with 10% FBS to suppress monocyte activation by measuring TNF-α from culture supernatants. We then evaluated proliferation, viability, and immunomodulatory characteristics of bone marrow-derived MSCs (BM-MSCs) cultured in FBS or ePL with or without fibrinogen. Growth factor concentrations decreased in ePL after fibrinogen depletion. Lipopolysaccharide (LPS)-stimulated monocytes exposed to ePL and fdePL produced less TNF-α than LPS-stimulated monocytes in 10% FBS. BM-MSCs cultured in fdePL exhibited lower proliferation rates, but similar viability compared with BM-MSCs in ePL. BM-MSCs in fdePL did not effectively suppress TNF-α expression from LPS-stimulated monocytes compared with BM-MSCs in FBS. Depleting fibrinogen results in a lysate that suppresses TNF-α expression from LPS-stimulated monocytes, but that does not support proliferation and immune-modulatory capacity of BM-MSCs as effectively as nondepleted lysate.