Human platelet suspension stimulates porcine retinal glial proliferation and migration in vitro

PURPOSE. TO characterize the cellular and molecular mechanisms underlying t he efficacy of autologous platelet suspension adjuvant therapy in the treat ment of macular hole. METHODS. Platelet suspensions were prepared from whole blood samples obtain ed from informed volunteers. For proliferation assays, platelet suspensions or purified growth factors were added to semi-confluent cultures of porcin e retinal glial cells for 24 hours, followed by [H-3]thymidine for 15 hours , after which time cells were washed, solubilized, and counted for uptake o f radioactive tracer. For cell migration assays, confluent glial cultures w ere scrape wounded and maintained in the presence or absence of platelet su spension or identified platelet constituents. Cell migration into the denud ed area was scored as a function of time. In certain cases, specific pharma cologic inhibitors of growth factor action were added at the same time as p latelet adjuvant or growth factors. RESULTS. Platelet suspension adjuvant induced strong mitogenic and chemotac tic responses in cultured glia, in a dose-dependent manner. Maximal incorpo ration of thymidine was two- to threefold that of control levels, with an E D50 similar to 5 x 10(6) platelets/ml, and migration was enhanced up to 80- fold after 48 hours. Platelet suspension-induced proliferation was complete ly blocked by addition of 25 mu M genistein, a tyrosine kinase receptor inh ibitor. However, the same concentration only partially blocked the cell mig ration response. Addition of any single growth factor or protein identified from ELISA analysis, or a combination of all factors, did not significantl y stimulate proliferation or cell migration. CONCLUSIONS. Human platelet suspensions exert both proliferative and chemot actic influences on retinal glial cells in vitro, suggesting that the same responses may occur in platelet-induced macular hole repair in humans. Grow th factors or proteins that have been identified within the suspensions do not mimic these responses in vitro, implying that additional currently unid entified trophic activities are also present.