Ontogeny of Steroidogenic Enzyme Gene Expression in Ovarian Theca-Interstitial Cells in the Rat: Regulation by a Paracrine Theca-Differentiating Factor Prior to Achieving Luteinizing Hormone Responsiveness1

Abstract

The theca cells (TC) first become identifiable in preantral follicles after the granulosa cells (GC) begin to divide. It remains unknown when the TC first respond to LH and acquire the capacity to produce androgens. The signal initiating TC differentiation is also unknown since pre-theca cells do not contain LH receptors. Since the first wave of follicle development in the rat occurs postnatally, we correlated the function of dispersed ovarian cells from 4-, 5-, 6-, 7-, and 10-day-old rats with the morphological differentiation of TC. The largest follicles in ovaries from 4-day-old rats were primary follicles without associated TC. These cells were unable to produce cAMP or steroids in vitro in response to hCG. At 5 days, the first theca were associated with follicles containing 2-3 layers of GC. These cells were responsive to hCG, producing cAMP, progesterone, androstenedione, and androsterone. Responses to hCG increased progressively through 10 days of age. Cholesterol side-chain cleavage (P450scc), 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), and 17 alpha-hydroxylase/C17-20 lyase (P450(17 alpha)) enzymes were localized exclusively to the theca interna. Messenger RNAs for LH receptor, P450scc, 3 beta-HSD, and P450(17 alpha) were expressed prior to the time the TC become responsive to LH or morphologically differentiated. To determine the source of the signal regulating TC differentiation, dispersed cells from 4-day-old rat ovaries that were unresponsive to LH were treated with preantral follicle-conditioned medium containing thecal differentiating factor (TDF) activity. The TDF activity stimulated androgen production and expression of LH receptor, P450scc, 3 beta-HSD, and P450(17 alpha) mRNAs. These data demonstrate that a paracrine signal from the preantral follicle can initiate TC differentiation prior to expression of LH receptors. TC become responsive to LH and capable of producing androgens coincident with morphological differentiation.

Isolation, characterization, andin vitroandin vivodifferentiation of putative thecal stem cells

“…All these cytological features are indicative of steroidogenic ability (17), a conclusion supported by the detection of androstenedione at a high concentration in the supernatant. These differentiation patterns of theca cells are consistent with previous findings showing that their proliferation and differentiation are independent of LH receptors in the early stages, but become LH receptordependent at a later stage (18), and that IGF1 synergistically augments the LH stimulation of androstenedione production (19). The stepwise emergence of several theca cell markers is also consistent with a previous in situ hybridization study that suggested that granulosa-derived factors, Ihh and Dhh, are candidate initiators of early thecal differentiation (13).…”

Vascular supply as a discriminating factor for pig preantral follicle selection

“…It is known that under physiological conditions, preantral follicle growth occurs within a rich milieu of endocrine, paracrine and autocrine factors (Kotsuji & Tominaga 1994, Gelety & Magoffin 1997. As a consequence, it may be hypothesised that the availability of an adequate vascular supply providing adequate levels of endocrine and paracrine signals may play a key role in follicle selection Vasculature during preantral follicle development during preantral follicle growth (Danforth 1995, Hull et al 2003, Roberts et al 2007).…”

Changes of Cyclic AMP Levels and Phosphodiesterase Activities in the Rat Ovary

“…Four rat models, the postnatal, immature, adult and acyclic aged persistent estrous (PE) rat models, are widely used in the literature [9][10][11][12][13][14][15][16][17][18][19][20][21]. Since follicular development in the rat occurs postnatally [11][12][13], we examined the postnatal rat model to determine the relationships between ovarian cAMP l e v e l , c A M P -P D E a c t i v i t y a n d f o l l i c u l a r development.…”

“…Since follicular development in the rat occurs postnatally [11][12][13], we examined the postnatal rat model to determine the relationships between ovarian cAMP l e v e l , c A M P -P D E a c t i v i t y a n d f o l l i c u l a r development. The immature rats primed with gonadotropin model offers the synchronous nature o f f o l l i c u l a r d e v e l o p m e n t , o v u l a t i o n a n d luteinization [14][15][16].…”