The regulation of porcine theca cell proliferation in vitro: synergistic actions of epidermal growth factor and platelet-derived growth factor.

Abstract

An important but poorly understood aspect of mammalian follicle development involves the regulation of theca cell proliferation. To investigate the premise that growth factors regulate theca cell proliferation, porcine theca cells were prepared by collagenase/DN'ase digestion of follicle linings after the removal of the granulosa cells and allowed to attach for 24 h. This method provided a monolayer of theca cells that had little if any granulosa cell contamination and which secreted high levels of androstenedione relative to granulosa cells during moderate-term culture (33-fold difference, P less than 0.01). In medium containing fetal calf serum (10%), theca cells were significantly more responsive to platelet-derived growth factor (PDGF) than epidermal growth factor (EGF) in terms of proliferation (13.4 +/- 0.2-vs. 7.0 +/- 0.1-fold increases relative to the initial cell count, P less than 0.05). This is in contrast to granulosa cells which were significantly more responsive to EGF than PDGF (7.1 +/- 0.1 vs. 4.0 +/- 0.2 fold-increases, P less than 0.05). Since serum has been shown to contain both EGF and PDGF, proliferation studies were performed using plasma-derived serum (PDS) which is growth factor restricted to examine more closely the direct effects of growth factors. In medium containing 0.25% PDS and within experiments, PDGF (1-25 ng/ml) stimulated theca cell proliferation in a dose-dependent manner (2.3-fold increase relative to controls, P less than 0.05) whereas EGF did not. EGF, however, markedly enhanced the proliferative action of PDGF (6.4-fold increase relative to controls, P less than 0.05). Insulin-like growth factor I and low density lipoprotein, factors which enhance markedly the proliferative effects of EGF and PDGF in terms of granulosa cell proliferation, exhibited only a modest synergistic effect with respect to EGF and PDGF upon theca cells (9.5-fold increase vs. a 6.4-fold increase above controls, P less than 0.05). Temporal studies in vitro indicate that theca cell proliferation is low during the first 3-day exposure to growth factors irrespective of treatment (a 2-fold increase over the seeding density). During the second 3-day exposure, however, theca cell proliferation increases 4- to 5-fold. The temporal pattern of theca cell proliferation stimulated by fetal calf serum supplemented with EGF or PDGF and PDS-containing medium supplemented with PDGF, EGF, insulin-like growth factor I, and low density lipoprotein is similar. These results suggest that PDGF is a major mitogen toward porcine theca cells and that EGF greatly enhances its activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Platelet-derived Growth Factor-stimulated Migration of Murine Fibroblasts Is Associated with Epidermal Growth Factor Receptor Expression and Tyrosine Phosphorylation

“…For example, a brief exposure of cells to PDGF induces BALB/c-3T3 cells to leave G 0 and enter the cell cycle, whereas EGF facilitates progression through G 0 /G 1 and entry into S phase (42). In addition, PDGF stimulates porcine theca cell proliferation in a dose-dependent manner, but although EGF alone is not mitogenic for these cells, it can markedly enhance the proliferative capacity of PDGF (43). Conversely, in granulosa cells, EGF-or transforming growth factor-␣-stimu- FIG.…”

“…Similar observations were made in three separate experiments. lated proliferation is enhanced by PDGF (42)(43)(44). Interestingly, a synergistic action between EGF and PDGF is not limited to mitogenesis, i.e.…”

Cell-Type Localization of Platelet-Derived Growth Factors and Receptors in the Postnatal Rat Ovary and Follicle1

“…Previous studies have elucidated a role for PDGF in inducing theca cell proliferation in theca cell cultures [30][31][32][33]. Thus, platelet-derived growth factors synthesized and released by theca cells may act in an autocrine or paracrine manner on theca cells expressing both receptors.…”

“…Platelet-derived growth factor (PDGF) has been demonstrated to stimulate in vitro proliferation of theca cells from antral follicles from both rat [30] and pig [31][32][33] while inhibiting thecal LH-induced steroid hormone synthesis [32]. Transcripts of the 4 Pdgf isoforms (Pdgfa, Pdgfb, Pdgfc, and Pdgfd) have been identified in the human ovary [34], but as yet there are insufficient data to indicate whether this is also true for the rodent ovary.…”

Platelet-Derived Growth Factors and Receptors in the Rat Corpus Luteum: Localization and Identification of an Effect on Luteogenesis1

“…Expression of all four isoforms of PDGFs and both PDGFRs have previously been characterized in the rat ovary [26]. PDGF has been demonstrated to stimulate in vitro proliferation of theca cells from antral follicles from both rat [27] and pig [28,29] while inhibiting thecal LH-induced steroid hormone synthesis [29]. In addition, the classic PDGF isoforms, PDGFA and PDGFB, were shown to contribute towards growth of preantral follicles [26].…”