Role Of Platelet-derived Growth Factor Research Articles

Effect of platelet-derived growth factor and bone marrow-conditioned medium on the proliferation of human bone marrow-derived fibroblastoid colony-forming cells.

The effects of various human sera, platelet lysates and platelet-derived growth factor (PDGF) on the proliferation of human bone marrow-derived fibroblastoid colony-forming cells (CFU-F) were examined. We obtained nearly identical growth curves of fibroblastoid colonies with sera, platelet lysates and PDGF as stimulants and concluded that PDGF was a main growth factor for CFU-F in human serum. In contrast to colony size, CFU-F number was irrelevant to the concentration of PDGF. Removal of culture medium containing hemopoietic cells after short-term incubation of bone marrow cells reduced both colony number and size in CFU-F cultures. When each of bone marrow-conditioned medium (BMCM), peripheral blood mononuclear cells (MNC) and phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM) was added to the cultures, CFU-F number and colony size recovered. The role of PDGF and the factors present in BMCM, MNC and PHA-LCM in the growth of CFU-F and their precursor cells were discussed.

The role of platelet-derived growth factor on human pluripotent progenitor (CFU-GEMM) growth in vitro

The effect of serum on the proliferation of human bone marrow pluripotent progenitor cells (CFU-GEMM), was compared to that of fresh frozen plasma (FFP). Serum significantly increased the number of mixed erythroid-granulocytic-megakaryocytic colonies (CFU-GEMM) and erythrocytic bursts (BFU-E) in this assay system ( p < 0.01 and 0.02, respectively). Two possible explantations for this finding were considered: first the presence of citrate-phosphate-dextrose (CPD) in plasma but not in serum, and second the presence of platelet-derived growth factor (PDGF) in serum but not in plasma. CPD was indeed found to have an inhibitory effect on growth of colonies of all types when added to serum-stimulated cultures. Nevertheless, when heparinized plasma was compared to serum from the same donors, growth of CFU-GEMM and BFU-E was higher in the serum-stimulated cultures ( p<0.001 and p<0.05, respectively). PDGF at concentrations of 120–240 pM was found to enhance the formation of CFU-GEMM and BFU-E by three-and four-fold respectively when added to cultures containing FFP but not when added to cultures containing serum derived from whole blood (WBS). Purified PDGF added at the same concentrations, to cultures containing platelet-poor derived serum (PDS), promoted similar increases in growth of CFU-GEMM and BFU-E but not of granulocytic-macrophage or megakaryocytic colonies. Whether PDGF has a direct action on CFU-GEMM or its growth promoting activity is via an interacting cell population is currently being studied.

Phenotype modulation in primary cultures of arterial smooth muscle cells: On the role of platelet-derived growth factor

Smooth muscle cells were isolated from adult rat aorta by collagenase digestion, grown in primary culture in the presence of 10% whole blood serum (WBS), and studied by quantitative electron microscopy and thymidine autoradiography in order to correlate cellular fine structure and proliferation. On day 2–4, the cells passed through a structural transition from contractile to synthetic state. In the former they were characterized by predominance of cytoplasmic microfilament bundles and in the latter by an extensive rough endoplasmic reticulum (RER) and a large Golgi complex. The disappearance of the microfilament bundles was accompanied by a transient increase in lysosomal volume density but no signs of bulk autophagy. This suggests that microfilaments were disassembled into subunit proteins and that lysosomes were engaged in adjusting the pool of free subunits into a new equilibrium. RER. cisternae grew out from the nuclear envelope and successively spread throughout the cytoplasm. Stacks of Golgi cisternae were organized in a circumscribed juxtanuclear region. The structural modulation occurred also in medium containing 10% plasma-derived serum (PDS). Its onset was delayed by addition of antibodies (50 μg/ml) against platelet-derived growth factor (PDGF) to 10% WBS-medium and speeded up by addition of purified PDGF (25 ng/ml) to 10% PDS-medium. Otherwise, the kinetics of the structural modulation was the same in all experimental groups. The observations could not be explained by overgrowth of contaminating fibroblasts since (1) successive steps in the process were clearly evident, (2) the cells surrounded themselves by an incomplete basement membrane, a characteristic feature of smooth muscle, and (3) mitomycin C blocked cell growth but not conversion from contractile to synthetic state. After 3–4 days of culture in 10% WBS-medium, active DNA synthesis and cellular proliferation were initiated as determined autoradiographically and by cell counting. Electron microscopic autoradiography showed that all cells were morphologically in the synthetic state at the time of entrance into S-phase. Initially, the cells grew at a lower rate in the presence of PDGF antibodies but after 5–6 days of culture attained a rate similar to that in the controls. No distinct proliferation was obtained in 10% PDS-medium unless purified PDGF (10 ng/ml) was added during the first days of culture. The results suggest that the structural modulation of the smooth muscle is an absolute but not sufficient prerequisite for cellular proliferation. PDGF and/or other serum factors are required to initiate DNA synthesis and mitosis. After a limited number of divisions, the cells enter a state of rapid growth characterized by reduced need of growth factors. Proliferation of the cells ceases first when multiple overlapping layers have been formed.

An evidence for “response to injury” hypothesis

Role of platelet-derived growth factor (PDGF) in myointimal thickening described in “response to injury” hypothesis was investigated with artery of rats in culture and with air-injured artery of rats. PDGF promoted cell growth in ring preparation of carotid artery in culture denuded with citrate. It did not promote any cell growth in preparations without denudation. Trapidil, a PDGF antagonist, inhibited the cell growth promoted by PDGF in the denuded arterial ring. Systemic injection of PDGF was performed for 8 days to rats with thrombocytopenia induced by injections of anti-platelet serum. This treatment caused myointimal thickening of carotid artery 10 days after denudation by means of air injury. Trapidil at oral intake levels of 1, 3 and 30 mg/kg/day inhibited this change observed in denuded site of artery. Trapidil at oral intake of 6 mg/kg/day also inhibited myointimal thickening observed 15 days after denudation of carotid artery by air injury in normotensive and spontaneous hypertensive rats both with normal platelet counts. These results evidenced the role of PDGF in myointimal thickening described in “response to injury” hypothesis and clinical use of trapidil may be a new approach to the treatment of atherosclerosis.

PLATELET-DERIVED GROWTH FACTOR ENHANCES GRANULOSA CELL LUTEINIZING HORMONE RECEPTOR INDUCTION BY FOLLICLE-STIMULATING HORMONE AND SERUM

Platelet-derived growth factor potentiated FSH-dependent LH receptor induction in serum-free and serum-containing cultures of rat granulosa cells. Levels of LH receptor binding comparable to pre-ovulatory levels could be achieved in vitro using a combination of FSH, platelet-derived growth factor, and serum. Receptor sites induced under these conditions were capable of mediating an hCG-stimulated increase in progestin secretion. Our results in vitro suggest a possible role for platelet-derived growth factor or related compounds in granulosa cell differentiation in vivo.