Biological effects of antibodies to gonadotropins

Modulation of Gonadotropins Activity by Antibodies

Gonadotropins are essential for reproduction control in humans as well as in animals. They are widely used all over the world for ovarian stimulation in women, spermatogenesis stimulation in men, and ovulation induction and superovulation in animals. Despite the availability of many different preparations, all are made of the native hormones. Having different ligands with a wide activity range for a given receptor helps better understand its molecular and cellular signaling mechanisms as well as its physiological functions, and thus helps the development of more specific and adapted medicines. One way to control the gonadotropins' activity could be the use of modulating antibodies. Antibodies are powerful tools that were largely used to decipher gonadotropins' actions and they have shown their utility as therapeutics in several other indications such as cancer. In this review, we summarize the inhibitory and potentiating antibodies to gonadotropins, and their potential therapeutic applications.

Kit-ligand/stem cell factor induces primordial follicle development and initiates folliculogenesis

Initiation of folliculogenesis through the induction of primordial follicle development in the ovary has an important role in determining the fertility and reproductive fitness of most mammalian species. The factors that control this critical process are largely unknown. The hypothesis tested in the current study was that kit-ligand/stem cell factor (KL) promotes the initiation and progression of primordial follicle development in the ovary. Ovaries from 4-day-old rats were maintained in organ culture for 5 and 14 days and treated with no factor (control), recombinant kit-ligand (KL), or gonadotropins (FSH and hCG). Follicles in ovarian sections were counted and histologically classified as primordial (stage 0), early primary (stage 1), primary (stage 2), transitional (stage 3), or preantral (stage 4). Fresh ovaries from 4-day-old rats contained 68% primordial follicles (stage 0) and 32% developing follicles (stages 1-4) per section. After 5 and 14 days in culture, section from control ovaries contained approximately 41% and 55%, respectively, developing follicles (stage 1-4) per section due to spontaneous development of primordial follicles. Spontaneous primordial follicle development was completely blocked by ACK-2, a c-kit antibody that blocks KL actions. This observation suggests that endogenous KL is necessary for primordial follicle development in vitro. After 14 days of KL treatment, sections from ovaries contained 17% primordial follicles (stage 0) and 83% developing follicles (stage 1-4) per section demonstrating a dramatic induction of primordial follicle development by KL. Gonadotropins (FSH and hCG) did not induce primordial follicle development but did increase the percentage of preantral follicles (stage 4) per section. This small increase in preantral follicles in response to gonadotropins was blocked by ACK-2 suggesting that KL may in part mediate gonadotropin actions after the initiation of primordial follicle development. Ovaries contained an average of 309+/-10 follicles per section. The total number of follicles per section did not significantly vary between treatments suggesting that the effects of KL were not due to an alteration in follicle number (i.e. survival). KL appears to be one of the first factors identified to be involved in the promotion of primordial follicle development. Results suggest that KL is necessary and sufficient to induce primordial follicle development and initiate folliculogenesis.

Effect of antigonadotropic sera on in vitro testicular metabolism of 3H-testosterone in immature rats

Male rats were daily injected from the 5th day to the 21st day of life with purified rabbit anti-FSH serum, or anti-LH serum. After the last injection, they were killed and the testes incubated in vitro with 3H-testosterone. The radioactive metabolites were separated and identified by a double isotope dilution method. In rats treated with antigonadotropic sera, the total amount of 5 alpha-reduced metabolites was significantly decreased. The profile of the 5 alpha-reduced metabolites obtained in the anti-FSH treated group was different from those obtained in control and anti-LH treated groups. Antigonadotropic sera modify the in vitro metabolism of testosterone by the testicular tissue.

Effect of anti-luteinizing hormone antibodies on the gonadotropic cells of the pituitary in immature male rats: an electron microscopic study

Treatment of immature rats with antigonadotropic serum results in atrophy of gonads and castration-like changes of gonadotroph cells in the pituitary gland. Newborn male albino Wistar rats were daily and subcutaneously inoculated with 0.1 to 0.8 ml of anti-luteinizing hormone (LH) sera from the first 24 hours of age, through the first 5 weeks. For controls, a similar schedule with normal rabbit serum was used. Rats were killed at weekly intervals and pituitaries were fixed for electron microscopy. The anti-LH titer, determined by microhemagglutination, was between 1:2, 560 and 1:10,240; the greatest contaminant was follicle-stimulating hormone, with the antiserum ranging from 1:160 to 1:320. Absorbed antisera, checked by double agar diffusion against unabsorbed antisera, showed no precipitin lines, indicating no antigen excess. There was no significant cytologic difference between control and experimental pituitaries during the 1st week of treatment. At the end of the 2nd week, gonadotroph cells contained a highly developed Golgi complex; by the 3rd week these cells contained pronounced, dilated, saclike ergastoplasmic cisternae, with few secretory granules in the cytoplasm of one type; by the 4th week, ergastoplasmic cisternae had broken down to form the first large vacuoles of "castration" LH gonadotrophs, some of which contained typical granules. Numerous mitotic and chromophobe cells were also observed. At the end of the 5th week castration LH cells persisted, in addition to mitotic cells, chromophobes, and numerous follicle-stimulating hormone gonadotrophs with degenerated features. The effect of anti-LH antisera on pituitary gonadotrophs could be explained as a neutralization of endogenous LH, probably not only inhibiting the long feedback mechanism, but also the short feedback loop at the level of the same pituitary cells.