Equine platelet lysate as an alternative to fetal bovine serum in equine mesenchymal stromal cell culture – too much of a good thing?

Summary Reasons for performing study Multipotent mesenchymal stromal cells ( MSC ) are often culture‐expanded in vitro . Presently, expansion medium ( EM ) for MSC is supplemented with fetal bovine serum ( FBS ). However, increasing cost, variable composition and potential risks associated with bovine antigens call for alternatives. Platelet lysate ( PL ) has shown promise as an alternative supplement. Objectives To determine how equine umbilical cord blood ( CB ) MSC proliferate in EM enriched with PL or FBS at various concentrations. Study design Randomised dose escalation study. Methods Platelet concentrate was generated from 5 equine whole blood samples through a double centrifugation method and standardised to 1 × 10 12 platelets/l prior to a freeze/thaw cycle to produce PL . Pooled PL or pooled FBS was added to EM at concentrations of 5% to 60%. Proliferation of 4 equine CB ‐ MSC cultures was determined after 4 days using a resazurin semiquantitative assay. Results Cord blood‐ MSC proliferated with a dose‐dependent response with no significant difference found between PL and FBS up to a 30% concentration. Beyond 30%, proliferation fell in the PL ‐cultured cells, while continued dose‐dependent proliferation was noted in the FBS ‐cultured cells. Despite reduced cell numbers in high PL concentrations, live/dead staining revealed that adherent cells remained viable. Conclusions Expansion medium enriched with PL can support short‐term equine CB ‐ MSC proliferation at conventional culture concentrations. Based on the unexpected suppression of CB ‐ MSC at higher PL concentrations, an in vivo dose study is indicated to investigate if combinational therapies of CB ‐ MSC and platelet‐rich plasma are associated with synergistic or antagonistic effect on CB ‐ MSC function.