Relationship between the concentration of bone morphogenetic protein-15 (BMP-15) and growth differentiation factor-9 (GDF-9) in pre-ovulatory follicles, ovarian cysts and serum in sows

The aim of the study was to compare and assess the relationship between peripheral and ovarian bone morphogenetic protein-15 (BMP-15) and growth differentiation factor-9 (GDF-9) concentration in cysts-bearing and non-cysts-bearing sows. The research involved multiparous sows (cysts-bearing sows, n = 20; non-cysts-bearing sows, n = 26). Serum, cystic follicular fluid or fluid from the ovulatory follicles was collected from each of the sows at the time of the slaughter. The collected serum and cystic/follicular fluid samples were tested for BMP-15 and GDF-9 concentrations. BMP-15 and GDF-9 concentrations in fluid from ovarian cysts were significantly higher than in the follicular fluid (P < 0.01). The concentration of BMP-15 and GDF-9 in the serum of sows with cysts was also higher than in ovulating sows (P < 0.05 and P < 0.01, respectively). The concentration of BMP-15 in serum was positively correlated with the concentration of said protein in pre-ovulatory follicles and cysts (r = 0.70; P < 0.01 and r = 0.50; P < 0.05, respectively). A positive correlation was also found between the concentration of serum GDF-9 and cyst GDF-9 (r = 0.55; P < 0.05). Moreover, another positive correlation was detected between the BMP-15 and GDF-9 concentrations, with the highest correlation coefficient recorded in the cyst fluid (r = 0.87; P < 0.01). This study for the first time demonstrates the presence of BMP-15 and GDF-9 in the cyst fluid in sows and determines a positive correlation between the concentration of the above factors in the follicular/cystic fluid and serum. Therefore, it is possible that the determination of BMP-15 and GDF-9 serum concentration may assist diagnosing ovarian cysts in sows. However, it is suggested that further studies involving a more in-depth analysis of the role of BMP-15 and GDF-9 in the pathogenesis of ovarian cysts in pigs are needed.