Platelet gel supernatant as a potential tool to repopulate acellular heart valves

Objective : The aim of this study was to repopulate decellularized heart valve matrices with ovine mesenchymal stem cells (oMSCs) by the use of platelet gel (PG) supernatant, a storage vehicle for growth factors. Methods : oMSCs were exposed to different concentrations of PG-released supernatant and cell proliferation was evaluated using the MTS assay. oMSC motility and invasiveness were assayed using a Boyden chamber. A quantitative sandwich enzyme immunoassay was used to examine amounts of bFGF and TGF-beta 1 in the PG supernatant. Repopulation of acellular heart valve matrices was stimulated by seeding matrices with oMSCs supplemented with the PG supernatant. Results : The most significant increase in proliferation induced by PG supernatant appeared at 1x105plts/ml concentration. Higher concentrations evoked reduction of the stimulatory process. oMSC motility was most significantly stimulated at 1x106plts/ml. Stimulating invasiveness of oMSCs needed the much higher concentration of 2x106plts/ml. Immunoassays revealed that sheep PG supernatant contains 184.8pg/ml bFGF and 60.5ng/ml TGF-beta 1. Moreover, repopulation of acellular heart valve matrices was significantly enhanced by PG supernatant addition and resulted in upregulation of the myofibroblast marker alpha-smooth muscle actin. Conclusions : Growth factors released from platelets had the potential to induce cell repopulation in a heart valve tissue engineering procedure, through stimulation of mesenchymal stem-cell migration and invasion