Discoveries of Anti-Müllerian hormone, its receptor, and a role to stimulates synthesis of collagen-specific chaperone HSP47 in bovine oviducts and endometria

ウシ子宮・卵管におけるアンチミューラーホルモンと受容体、ならびに、コラーゲン特異的シャペロンHSP47の合成促進作用の発見

Discoveries of Anti-Müllerian hormone, its receptor, and a role to stimulates synthesis of collagen-specific chaperone HSP47 in bovine oviducts and endometria

Degree Grantors Yamaguchi University

Fertility decreases during aging in human and bovine females, but the exact pathophysiological mechanisms in the oviducts and uteri are not clarified yet. Anti- Müllerian hormone (AMH) is a glycoprotein that belongs to the transforming growth factor -β superfamily. Plasma AMH concentration can predict the fertility of adult female goats, ewes, cows, and women via unknown physiological mechanisms. This thesis study attempted to clarify whether AMH, and the main receptor for AMH, AMH receptor type 2 (AMHR2) have important roles for the age-related infertility.
In first, I investigated whether the primary receptor for AMH, AMHR2, is expressed in bovine oviducts and endometria. Reverse transcription polymerase chain reaction (RTPCR) detected expression of AMHR2 mRNA in oviductal and endometrial specimens. Western blotting and immunohistochemistry were performed to analyse AMHR2 protein expression using anti-bovine AMHR2 antibody. Immunohistochemistry revealed robust AMHR2 expression in the tunica mucosa of the ampulla and isthmus, as well as in the glandular and luminal epithelium of the endometrium. The number of AMHR2-positive fibroblasts increased, suggesting the presence of fibrosis in the oviducts and uteri of old cows. AMHR2 mRNA (measured RT-qPCR) and AMHR2 protein expression in these layers did not significantly differ among oestrous phases in adult Japanese Black (JB) cows (P>0.1). In addition, AMHR2 mRNA and protein expression in these layers did not differ Among old Holsteins (mean (±SEM age 91.9±6.4 months ) and young (26.6±0.8 months) and old (98.8±10.2 months) JB cows. Therefore, AMHR2 is expressed in bovine oviducts and endometria.
Other important hormones for endocrinological regulation have paracrine and autocrine roles. Therefore, in the next study, I investigated whether bovine oviducts and endometria produce AMH. RT-PCR and western blotting detected AMH expression in oviductal and endometrial specimens. Immunohistochemistry revealed robust AMH expression in the ampulla and isthmus epithelia, and the glandular and luminal endometrial epithelia (caruncular endometria). The number of AMH-positive fibroblasts increased, suggesting the presence of fibrosis in the oviducts and uteri of old cows. AMH mRNA and protein expression in these layers did not significantly differ among estrous phases in adult JB heifers (p > .1). Furthermore, the expression in these layers also did not differ among Holstein cows (93.8 ± 5.8 months old), JB heifers (25.5 ± 0.4 months old), and JB cows (97.9 ± 7.9 months old). We also compared AMH concentrations in the oviduct and uterine horn fluids among the three groups (measured by immunoassays). Interestingly, the AMH concentration in the oviduct fluid, but not in the uterine horn fluid, of Holstein cows was lower than those in JB heifers and cows (p < .05). Therefore, bovine oviducts and endometria express AMH and likely secrete it into the oviduct and uterine fluids.
Collagen, the most abundant extra-cellular matrix in oviducts and uteri, performs critical roles in pregnancies. I hypothesised that the locations and amounts of both denatured collagen and the collagen-specific molecular chaperone 47-kDa heat shock protein (HSP47) in the oviducts and uteri of old cows are different compared with those of young heifers because of repeated pregnancies. Since detecting damaged collagen in tissues is challenging, we developed a new method that uses a denatured collagen detection reagent. Then, we compared damaged collagen in the oviducts and uteri between postpubertal growing nulliparous heifers (22.1 ± 1.0 months old) and old multiparous cows (143.1 ± 15.6 months old). Further, I evaluated the relationship between denatured collagen and HSP47 by combining this method with fluorescence immunohistochemistry. Picro sirius red staining showed collagen in almost all parts of the oviducts and uteri. Expectedly, damaged collagen was increased in the oviducts and uteri of old cows. However, damaged collagen and HSP47 were not located in the same area in old cows. The number of HSP47- positive fibroblasts increased, suggesting the presence of fibrosis in the oviducts and uteri of old cows. These organs of old cows showed higher HSP47 protein amounts than those of heifers. However, the uteri, but not oviducts, of old cows had lower HSP47 mRNA amounts than those of heifers. These findings revealed the specific location and amounts of denatured collagen and HSP47 in the oviducts and uteri of old cows compared with those of heifers.
Therefore, I discovered the AMH, AMHR2 expression in several important layers of oviducts and uteri, and I discovered the increased AMH, AMHR2, and HSP47 in the fibroblasts after aging. However, still role of AMH, AMHR2 in oviducts and uteri were not clarified yet. Therefore, in the next study, I hypothesized that AMH stimulate HSP47 expression in fibroblast and epithelium. I cultured uterine fibroblasts and epithelial cells obtained from heifers. Then, I treated the cells with recombinant with increasing concentrations (0, 1, 10, or 100 ng mL-1) of AMH. HSP47 expression was measured by western blotting. AMH stimulated (P<0.05) HSP47 expression in epithelial cells but not in fibroblasts. Therefore, these findings suggested the role of AMH to cause the abnormal high HSP47 expression in the oviducts and uteri of old cows.
In conclusion, this thesis discovered the AMH and AMHR2 in bovine oviducts and uteri, which have important roles for collagen synthesis via HSP47.

Creators Ferdousy Raihana Nasrin