In mammals, growing follicles develop from a reserve of primordial follicles (PMFs) constituted early in life. From this pre-established reserve, a second ovarian reserve is formed consisting of gonadotropin-responsive growing follicles that in the adult are cyclically selected for ovulation [1]. PMFs reserve progressively diminishes due to follicle atresia as well as recruitment, maturation, and ovulation. The role of LH in the natural menstrual cycle is undisputed. While the crucial participation of LH in both steroidogenesis and ovulation is well established, other possible functions in follicle dynamics are debated. We demonstrated the presence of LH receptor in early postnatal mice ovaries and that LH treatment can promote PMF survival [2]. Therefore, our aim is to investigate LH potential role in activating signaling pathways associated with follicle activation in the ovarian reserve. We performed in vitro cultures on ovarian fragments from 4 days post-partum (dpp) female mice and treated them with different concentration of LH (LH 0.2 0.5 and 1 IU) every day for 5 days. The results showed that in the fragments cultured in the presence of 1 IU LH, both the total number of oocytes and the % of those with diameter >40 ?m were significantly higher in comparison to CTRL. LH effects were also investigated in vivo by treating 4dpp mice with intra-peritoneal injection once a day for 8 consecutive days, with physiological solution or with LH 1IU. On day 9, ovaries were collected for histological analysis. Follicle count in control ovaries showed a higher pool of PMF (68,22%) than the other follicles, which have as expected undergone activation (growing [GR] 14,18%, and primary [PF] 7,2% follicles). Interestingly, in LH treated mice ovaries, we observed a higher percentage of PMF (78,29%) and a lower percentage of GR (8,56%) an PF (4,05%) than control. Although the percentage of secondary follicles (SEC) was similar in both groups (CTRL 7,6% vs LH 7,35%), in the LH-treated mice SECs showed a thicker layer of granulosa cells (> three layers CTRL 42,8% vs LH 54,6%). Finally, we observed decreased atresia in LH-treated group (CTRL 2,64% vs LH 1,72%). In conclusion, our results extended our previous data about the responsiveness of prepuberal ovaries to LH. At this stage, LH seems to favor the maintenance of PMF reserve and to sustain the follicle growth toward the secondary stage upon PMF activation.
Unconventional actions of LH on prepuberal ovary
Gina La Sala;
2023
Abstract
In mammals, growing follicles develop from a reserve of primordial follicles (PMFs) constituted early in life. From this pre-established reserve, a second ovarian reserve is formed consisting of gonadotropin-responsive growing follicles that in the adult are cyclically selected for ovulation [1]. PMFs reserve progressively diminishes due to follicle atresia as well as recruitment, maturation, and ovulation. The role of LH in the natural menstrual cycle is undisputed. While the crucial participation of LH in both steroidogenesis and ovulation is well established, other possible functions in follicle dynamics are debated. We demonstrated the presence of LH receptor in early postnatal mice ovaries and that LH treatment can promote PMF survival [2]. Therefore, our aim is to investigate LH potential role in activating signaling pathways associated with follicle activation in the ovarian reserve. We performed in vitro cultures on ovarian fragments from 4 days post-partum (dpp) female mice and treated them with different concentration of LH (LH 0.2 0.5 and 1 IU) every day for 5 days. The results showed that in the fragments cultured in the presence of 1 IU LH, both the total number of oocytes and the % of those with diameter >40 ?m were significantly higher in comparison to CTRL. LH effects were also investigated in vivo by treating 4dpp mice with intra-peritoneal injection once a day for 8 consecutive days, with physiological solution or with LH 1IU. On day 9, ovaries were collected for histological analysis. Follicle count in control ovaries showed a higher pool of PMF (68,22%) than the other follicles, which have as expected undergone activation (growing [GR] 14,18%, and primary [PF] 7,2% follicles). Interestingly, in LH treated mice ovaries, we observed a higher percentage of PMF (78,29%) and a lower percentage of GR (8,56%) an PF (4,05%) than control. Although the percentage of secondary follicles (SEC) was similar in both groups (CTRL 7,6% vs LH 7,35%), in the LH-treated mice SECs showed a thicker layer of granulosa cells (> three layers CTRL 42,8% vs LH 54,6%). Finally, we observed decreased atresia in LH-treated group (CTRL 2,64% vs LH 1,72%). In conclusion, our results extended our previous data about the responsiveness of prepuberal ovaries to LH. At this stage, LH seems to favor the maintenance of PMF reserve and to sustain the follicle growth toward the secondary stage upon PMF activation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
