However, this murine study did not delineate which luteal cells were affected.

Theca lutein cells are also known as small luteal cells.

Small luteal cells (12-22 μm diameter) were defined as spindle-shaped with dark-staining cytoplasm.

There is a strong association with abnormal menstruation - amenorrhoea, anovulatory cycles or luteal cell defects.

Progesterone is synthesized from cholesterol by both the large and small luteal cells upon luteal maturation.

Luteal cells possess the necessary enzymes to convert cholesterol to pregnenolone (P5), which is subsequently converted into P4.

Large luteal cells produce more progesterone due to uninhibited/basal levels of PKA activity within the cell.

Cholesterol-LDL complexes bind to receptors on the plasma membrane of luteal cells and are internalized.

Small luteal cells have LH receptors that regulate PKA activity within the cell.

They directly innervate the ovarian theca and secondary interstitial cells and exert an indirect action on the luteal cells.

Mature CL showed strong surface LHR immunoreactivity of luteal cells (Fig.

Background The adult mammalian ovary is a complex tissue composed of four fundamental cell types: the oocytes, granulosa, interstitial, and corpora luteal cells.

However, in the CL of pregnancy, nuclei of luteal cells show abundant p27 expression (arrow, panel B), accompanied by moderate cytoplasmic staining.

Knockout studies in mice suggest that the interaction of PGF2-alpha with this receptor in ovarian luteal cells initiates luteolysis and thus induces parturition.

Luteal cells in the old CL (late luteal period) showed marked diminution of LHR expression (Fig.

When compared to p27, the cyclin D1 is expressed in some nuclei of luteal cells only (arrow, panel C) and absent from the stromal cells in the CL of pregnancy.

CL from early human pregnancies showed various intensities of LHR expression (from weak to intense) on the surface and in the cytoplasmic regions of luteal cells [ 24 ] .

Yet, cell surface staining was observed only on classic LH/CG targets, granulosa and theca cells of preovulatory follicles and mature luteal cells, but also in the vaginal epithelium.

It is primarily present in steroid-producing cells, including theca cells and luteal cells in the ovary, Leydig cells in the testis and cell types in the adrenal cortex.

In human ovaries, LHR expression was also detected in granulosa and theca cells of preovulatory follicles, but mature CL showed strong expression in luteal cells, which disappeared during luteal regression.

The LHCGR is present on granulosa cells, theca cells, luteal cells, and interstitial cells The LCGR is restimulated by increasing levels of chorionic gonadotropins in case a pregnancy is developing.

Expression of p21 (panel E) is similar to that of cyclin E. The pRb (panel F) shows nuclear expression similar to that of p27, including stromal cells, but no cytoplasmic staining of luteal cells.

The follicular theca cells luteinize into small luteal cells, (thecal-lutein cells) and follicular granulosa cells (granulosal-lutein cells), luteinize into large luteal cells forming the corpus luteum.

Osteonectin is expressed by a wide variety of cells including chondrocytes, fibroblasts, platelets, endothelial cells, epithelial cells, Leydig cells, Sertoli cells, luteal cells, adrenal cortical cells and numerous neoplastic cell lines (such as SaOS-2 cells from human osteosarcoma).