Expression of relaxin-3 and its receptors in the hypothalamic-pituitary-ovary axis in layers and broiler breeders

Authors: BOUKHERROUB, KAHNIA - University Of Minnesota; KOSONSIRILUK, SUNANTHA - University Of Minnesota; SANTATIVONGCHAI, PITCHAYA - University Of Minnesota; CHELIKANDAM, JASNA - University Of Minnesota; EHRESMANN, LILLIAN - University Of Minnesota; Diehl, Kristen

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2025
Publication Date: 3/15/2025
Citation: Boukherroub, K., Kosonsiriluk, S., Santativongchai, P., Chelikandam, J., Ehresmann, L., Diehl, K.M. 2025. Expression of relaxin-3 and its receptors in the hypothalamic-pituitary-ovary axis in layers and broiler breeders. Poultry Science. 104(5). Article e105048. https://doi.org/10.1016/j.psj.2025.105048.
DOI: https://doi.org/10.1016/j.psj.2025.105048

Interpretive Summary: Laying hens can regulate their feed intake and maintain proper ovarian function while broiler breeder hens are prone to overeating, leading to ovarian disfunction. Relaxin-3 is a hormone involved in metabolism, energy balance, and reproduction and has been detected in the tissues of the reproductive axis in chickens. This study aimed to explore expression differences of relaxin-3 and its associated receptors in ovarian follicles, the pituitary gland, and the hypothalamus between layers hens and broiler breeder hens. Overall, RLN3 and its receptors were differentially expressed across the reproductive axis and between laying hens and broiler breeder hens, suggesting a potential role in nutrition and ovarian dysregulation. Localization of relaxin-3 and its receptors suggests action is likely mediated through autocrine and paracrine effects. Modulating relaxin-3 could lead to novel strategies of regulating feed intake in broiler breeders.

Technical Abstract: Layers can regulate their feed intake and maintain well-organized ovaries while broiler breeders are prone to overeating, leading to disorganized ovaries. Relaxin-3 (RLN3) is a neuropeptide hormone involved in metabolism, energy balance, and reproduction in mammals. In chickens, RLN3 was identified in the ovary, pituitary gland, and hypothalamus. This study aimed to explore the potential role of RLN3 in feeding behavior and reproduction by examining differences in the expression of RLN3 and relaxin family peptide receptors (RXFP1 and 3), in ovarian follicles, the pituitary gland, and the hypothalamus between layers (L) and broiler breeders (BB). Gene expression analysis revealed RLN3 was highest in the granulosa cells (GC) of 9-12 mm follicles compared with other follicles, with BB had the highest overall expression. In the pituitary, RLN3 was higher in L compared with BB and minimally expressed in follicle theca tissue (TH), cortex, and hypothalamus. Expression of RXFP1 was highest in TH of all follicles without a significant difference between L and BB. The expression of RXFP3 was highest in the cortex without a significant difference between L and BB. The hypothalamus had the highest expression of RXFP3 across all tissues in both L and BB. Immunofluorescence staining for RLN3, RXFP1, and RXFP3 revealed their presence in the GC, TH interna and externa of 3-12 mm follicles in both L and BB. Interestingly, RLN3 was localized in small vesicles in the ooplasm of 3-12 mm follicles. Within the cortex, RXFP1 was localized in the GC and TH of cortical follicles while RXFP3 was exclusively localized in the stromal and muscle cells. Surprisingly, RXFP3 was also localized in the nucleus. Overall, RLN3 and its receptors were differentially expressed across the hypothalamic-pituitary-ovarian axis and between layers and broiler breeders suggesting a potential role in nutrition and ovarian dysregulation. Further, RLN3 action is likely mediated through autocrine and paracrine effects. Modulating RLN3 could lead to novel strategies of regulating feed intake in broiler breeders.