| The arterial characteristics and expressions levels of angiogenesis genes in ovaries have important influences on the production performance of sheep.To understand the relationship between fertility and ovarian vascular characteristics and expressions of Vascular endothelial growth factor(VEGF),Angiopoietin-1(Ang-1),Angiopoietin-2(Ang-2),Tyrosine kinase receptors-2(Tie-2).The vascular casts of the arteries were yield on ovarian specimens by the corrosion casting technique,and the expressions of angiogenic genes were detected by qRT-PCR.Morphological features,arterial diameters and gene expression levels were compared and analyzed among Small-Tailed Han sheep,Hu sheep,Tibetan sheep.The main findings are as follows:1.All breeds(Small-Tailed Han sheep,Hu sheep and Tibetan sheep)of ovarian artery trunk originate from the abdominal aorta and shows straight course,contain the ovarian branch,uterus branch and oviduct branch.Especially,ovarian branch presents a typical spiral structure,After the spirals of ovarian branch is tapering before entering the ovarian hilum,and sends out several branches that wrap around each other and form a tight fist-shaped coiling structure located the medulla of ovarian hilum,which accounts for approximately one-half of the ovary volume.During the course of uterine and oviduct branches to mesentery,there are multiple secondary and tertiary tortuous branches were found to supply blood to the uterus and fallopian.2.Comparative studies revealed the morphological differences of ovarian arteries among different breeds,especially focused on the number of spiral coils and forms of tangles.For example,most of the ovarian branches of Small-Tailed Han sheep and Hu sheep were consist of two paratactic arteries and extend to the ovaries,however,ovarian branches in the most of Tibetan sheep were consist of single arteries,and especially it showed cone-shaped in Tibetan sheep.Additionally,there were different number of spiral coils in the ovarian arteries among breeds.There were about 35-40 spiral coils in Small-Tailed Han sheep and Hu sheep while there were about 25-30 spiral coils in Tibetan sheep.Moreover,folding of the ovarian spiral arteries showed different levels.The ovarian spiral artery in Small-Tailed Han sheep was more developed,and represented more complex zigzag while there showed relatively less coils and simpler folding in Tibetan sheep.Lastly,the second and third branches giving off from uterine and oviductal branches were more and developed in Small-Tailed Han sheep and Hu sheep while they were less and underdeveloped in the Tibetan sheep.3.Measuring results of vascular diameters at seven parts located ovarian artery and its branches in three sheep breeds revealed that the diameters of the ovarian artery and its branches showed significant differences among breeds.It was found that the diameter of the ovarian artery trunk,uterus branch and oviduct branch,near part of spiral artery,and far part of spiral artery,near ovarian hilum artery of the Small-Tailed Han sheep and Hu sheep in the fecundity group were higher than the low prolific breeds such as Tibetan sheep.By comparison of diameters,it showed that the trunk of ovarian artery,oviduct branch in the Small-Tailed Han sheep and Hu sheep was significantly larger than that of Tibetan sheep(P<0.05).Besides,diameters of near part of spiral artery,and far part of spiral artery,near ovarian hilum artery in Hu sheep were significantly larger than those in Small-Tailed Han and Tibetan sheep(P<0.05).4.The results showed that there were differences of expression levels of VEGF,Ang-1,Ang-2 and Tie-2 among ovaries of different breeds.The expression levels of VEGF,Ang-1,and Tie-2 in ovaries of Small-Tailed Han sheep and Hu sheep were higher compared to that of Tibetan sheep.Additionally,there were significant differences of the expression levels of VEGF among three breeds(P<0.05).The expression of Ang-1 in the ovary of Small-Tailed Han sheep was significantly higher than that of Tibetan sheep(P<0.05).The expression of Tie-2 was more abundant in Small-Tailed Han sheep’s ovaries,and there were significant differences compared to that of Hu sheep,and Tibetan sheep(P<0.05).However,the expression level of Ang-2 was opposite and their expression levels sequences from high to low as follows: Tibetan sheep,Hu sheep and Small-Tailed Han sheep.There were significant differences between Small-Tailed Han sheep and Tibetan sheep(P<0.05).Collectively,the results indicated that fecundity sheep have more developed arterial system.More importantly,higher fecundity breeds have a larger diameter of the ovarian artery and its branches than those of the low prolific breeds,similarly the expressions of VEGF,Ang-1,and Tie-2 were higher in the ovaries of fecundity breeds.which could provide more blood to vessel of ovary and improve the lambing rate of sheep. |
