Purification of platelet-derived endothelial cell growth inhibitor and its characterization as transforming growth factor-beta type 1.

In 1986, Brown and Clemmons (Proc. natl Acad. Sci. USA 83 (1986) 3321) showed that platelets contain a substance, platelet-derived growth inhibitor (PDGI), that inhibits in vitro endothelial cell replication. Although platelets are rich in transforming growth factor beta (TGF-beta), PDGI was considered not to be related to TGF-beta, on the basis of its reported properties (extraction from platelets at neutral pH, binding to heparin-Sepharose). However, we purified PDGI to near homogeneity and showed that on the basis of HPLC retention behavior, in vitro growth inhibitory activities with several cell types, receptor binding, and immunoneutralization of growth inhibitory activity with specific anti-TGF-beta type 1 antibodies, PDGI is most probably identical with TGF-beta type 1.