Tumor necrosis factor-α stimulates proliferation of rat ovarian theca- interstitial cells

Abstract

Tumor necrosis factor-α (TNF-α) is a potent modulator of ovarian function, affecting steroidogenesis of both granulosa and theca-interstitial (T-I) cells. Women with polycystic ovary syndrome (PCOS) have increased levels of serum TNF-α. The present study evaluated the effects of TNF-α on T-I cell proliferation. Purified rat T-I cells were cultured for 48 h with or without TNFα (0.001-1 nM), insulin-like growth factor I (IGF-I; 10 nM), and/or insulin (10 nM). Proliferation was measured by [3H]thymidine incorporation assay and by counting the steroidogenically active (stained positive for 3β-hydroxysteroid dehydrogenase; 3βHSD) and inactive (3β-HSD negative) cells. TNFα stimulated thymidine incorporation in a dose-dependent fashion (up to 3.2-fold; P < 0.01). Insulin and IGF-I stimulated T-I proliferation (respectively, by up to 2.4- and 3.1-fold; P < 0.001). TNF-α potentiated effects of insulin and IGF-I in a dose-dependent and additive fashion (up to 6.7-fold; P < 0.001). TNF-α (1 nM) increased total cell count (by 80%, P < 0.05) and the proportion of 3β-HSD-positive cells (by 19%, P < 0.05). Flow cytometry DNA analysis revealed that TNF-α (1 nM) increased the proliferative index by up to 16% (P = 0.05). The present findings demonstrate that TNF-α stimulates mitotic activity of T-I cells by increasing the proportion of actively dividing cells and preferentially increasing the number of steroidogenically active cells. The effects of TNF-α appear to be independent of those induced by insulin and IGF-I. We postulate that TNF-α may play a pathophysiologic role in disorders of the T-I compartment, such as PCOS.