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Ovarian thecal/interstitial cells produce an epidermal growth factor-like substance
M K Skinner1, D Lobb, J H Dorrington
1Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee.
Abstract:
An ovarian thecal/interstitial cell preparation was obtained by enzymatic digestion of immature rat ovaries depleted of granulosa cells. A component in thecal/interstitial cell-conditioned medium inhibited specific binding of [125I]iodo-epidermal growth factor ([125I]EGF) to its cell surface receptor, as determined with an EGF radioreceptor assay. Thecal/interstitial cell secreted proteins also stimulated growth of an EGF-dependent cell line. Granulosa cells isolated from the same ovaries did not produce detectable levels of an EGF-like substance, as determined by both EGF RRA and EGF growth assay. Fractionation of thecal/interstitial cell secreted proteins by size exclusion HPLC resulted in a 35K component being detected by both the EGF RRA and the growth assay. An EGF-like substance was also detected when thecal/interstitial cell secreted proteins were fractionated by reverse phase HPLC. Several biochemical properties of the EGF-like substance examined were different from those of authentic mouse EGF. However, the biological activities of the EGF-like substance and mouse EGF were similar in their ability to promote the growth of an EGF-dependent cell line. In addition to the production of an EGF-like substance, the thecal/interstitial cell preparation also produced an EGF inhibitory activity. This thecal/interstitial cell secreted product was fractionated from the EGF-like substance and inhibited the ability of EGF to stimulate cell growth. EGF receptors are present on granulosa cells, and EGF is known to influence both the growth and differentiation of these cells. Observations indicate that ovarian thecal/interstitial cells produce an EGF-like substance that may act as a paracrine factor to regulate granulosa cell growth and differentiation. In addition, an EGF inhibitory activity is produced that also may have a role in regulating follicular cell growth.
Insights
Ovarian thecal cells produce an epidermal growth factor (EGF)-like substance that influences granulosa cell growth and differentiation. These cells also secrete an EGF inhibitory activity, suggesting a role in regulating follicular cell proliferation.
Area of Science:
- Reproductive Biology
- Endocrinology
- Cell Biology
Background:
- Epidermal Growth Factor (EGF) plays a crucial role in regulating ovarian cell growth and differentiation.
- Granulosa cells possess EGF receptors, indicating their responsiveness to EGF signaling.
- The specific role of thecal/interstitial cells in producing EGF-like substances within the ovary remains to be fully elucidated.
Purpose of the Study:
- To investigate the production of EGF-like substances and their modulators by ovarian thecal/interstitial cells.
- To determine if these substances influence the growth and function of granulosa cells.
- To characterize the nature of the secreted EGF-like molecules and their biological activities.
Main Methods:
- Enzymatic digestion of immature rat ovaries to isolate thecal/interstitial cells, separating them from granulosa cells.
- Conditioned medium from thecal/interstitial cells was analyzed using EGF radioreceptor assay (EGF RRA) and an EGF-dependent cell line growth assay.
- Size exclusion and reverse-phase high-performance liquid chromatography (HPLC) were employed to fractionate and characterize secreted proteins.
Main Results:
- Thecal/interstitial cell-conditioned medium contained a component that inhibited [125I]EGF binding and stimulated the growth of an EGF-dependent cell line.
- Granulosa cells did not produce detectable levels of EGF-like substances.
- HPLC fractionation identified a 35K component with EGF-like activity and also revealed an EGF inhibitory activity distinct from the EGF-like substance.
Conclusions:
- Ovarian thecal/interstitial cells secrete an EGF-like substance that may function as a paracrine factor regulating granulosa cell growth and differentiation.
- These cells also produce an EGF inhibitory activity, potentially playing a role in controlling follicular cell proliferation.
- The biochemical properties of the thecal/interstitial cell-derived EGF-like substance differ from mouse EGF, but its biological activity is similar.