Chen, Haolin, Pu, Ling, Tian, Chengcheng, Qi, Xingcai, Song, Juanjuan, Liao, Yan, Mo, Bentian, and Li, Taotao
Simple Summary: Platelet-derived growth factor B (PDGFB) serves as an important cytokine for cell growth and development. Tibetan sheep (Ovis aries), a unique local breed in the Qinghai–Tibet Plateau, have poor reproductive physiological characteristics, including long developmental cycles, late sexual maturity, and low fecundity, yet the mechanisms behind remain elusive. Spermatogenesis and sperm maturation are highly dynamic and multifactorial developmental processes occur in the male testis and epididymis, respectively, and thus are crucial for maintaining male reproductive function and species continuity. Despite the importance of PDGFB, its role in maintaining the development and function of the testes and epididymides in sheep remains obscure. Herein, we report, for the first time, the cloning and molecular characterization of Tibetan sheep PDGFB. Meanwhile, we investigated the gene expression pattern and subcellular localization of PDGFB in developmental testes and epididymides in Tibetan sheep. The results revealed that the Tibetan sheep PDGFB gene has a high degree of evolutionary conservation and suggested that it participates in the development and function of testicular and epididymal red blood cells, Leydig cells as well as epididymal principal cells and ciliated epithelial cells, thus contributing to the spermatogenesis and sperm maturation of Tibetan sheep. Platelet-derived growth factor B (PDGFB), as an important cellular growth factor, is widely involved in the regulation of cellular events such as cell growth, proliferation, and differentiation. Although important, the expression characteristics and biological functions in the mammalian reproductive system remain poorly understood. In this study, the PDGFB gene of Tibetan sheep was cloned by RT-PCR, and its molecular characteristics were analyzed. Subsequently, the expression of the PDGFB gene in the testes and epididymides (caput, corpus, and cauda) of Tibetan sheep at different developmental stages (3 months, 1 year, and 3 years) was examined by qRT-PCR and immunofluorescence staining. A bioinformatic analysis of the cloned sequences revealed that the CDS region of the Tibetan sheep PDGFB gene is 726 bp in length and encodes 241 amino acids with high homology to other mammals, particularly goats and antelopes. With the increase in age, PDGFB expression showed an overall trend of first decreasing and then increasing in the testis and epididymis tissues of Tibetan sheep, and the PDGFB mRNA expression at 3 months of age was extremely significantly higher than that at 1 and 3 years of age (p < 0.05). The PDGFB protein is mainly distributed in testicular red blood cells and Leydig cells in Tibetan sheep at all stages of development, as well as red blood cells in the blood vessel, principal cells, and the pseudostratified columnar ciliated epithelial cells of each epididymal duct epithelium. In addition, PDGFB protein expression was also detected in the spermatocytes of the 3-month-old group, spermatids of the 1-year-old group, spermatozoa and interstitial cells of the 3-year-old group, and loose connective tissue in the epididymal duct space in each developmental period. The above results suggest that the PDGFB gene, as an evolutionarily conserved gene, may play multiple roles in the development and functional maintenance of testicular cells (such as red blood cells, Leydig cells, and germ cells) and epididymal cells (such as red blood cells, principal cells, and ciliated epithelial cells) during testicular and epididymal development, which lays a foundation for the further exploration of the mechanisms by which the PDGFB gene influences spermatogenesis in Tibetan sheep. [ABSTRACT FROM AUTHOR]