In order to obtain more information on the development of bovine and ovine fetal mammary
glands, a series of mammary glands from fetuses of different ages were analyzed. A total
of 16 bovine fetuses with curved crown rump lengths ranging from 12 cm (80 days) to 75 cm
(240 days) and 15 ovine fetuses ranging from 55 days to 131 days were examined. We used
hematoxylin and eosin stain and Oil-Red-O stain to analyze the developmental and
morphogenetic processes of mammary glands. In addition, we used immunohistochemical
staining to determine the pattern of expression of cytokeratin 18 (CK18) during luminal
epithelial differentiation, α-smooth-muscle actin (α-SMA) for myoepithelial
differentiation, Ki-67 for cell proliferation, and estrogen receptor α (ERα). Our analyzes
showed: (a) The primary mammary duct begin to proliferate in a lengthwise within the teat
at 90 days in bovine fetuses and 63 days in ovine fetus; (b) luminal epithelial cells and
myoepithelial cells appeared from 90 days in bovine fetuses and 63 days in ovine fetus;
(c) proliferation of epithelial cells appeared to coincide with the development of the
primary and secondary ducts; and (d) ERα was not found in the fetal mammary gland, but
adipocytes showed the presence of ERα. Overall, these results indicate that the sequence
of events in the prenatal development of the mammary gland of sheep is similar to that of
cattle.
Summary
The efficiency of in vitro embryo production technologies would be improved by the development of suitable non-invasive biomarkers that allow the selection of good quality cumulus–oocyte complexes (COCs). The present study used whole, single oocyte culture to investigate whether the expression levels of follicle-stimulating hormone receptor (FSHR), insulin-like factor 1 receptor (IGF1R) and three steroidogenesis-related enzymes (CYP11al, CYP19al and HSD3β) in cumulus cells reflected the developmental competence of COCs. Cumulus cells were collected from single COCs before maturation culture and relative mRNA levels were assessed using real-time PCR. The analysis indicated that mRNAs for FSHR, IGF1R, CYP11al and HSD3β were present at higher levels in cumulus cells from COCs that failed to form blastocysts compared with cumulus cells from COCs that formed blastocysts. Moreover, FSHR and IGF1R mRNA levels were positively correlated with those of genes for steroidogenesis-related enzymes. In conclusion, poor developmental competence of COCs was related to higher expression of FSHR, IGF1R, CYP11al and HSD3β in cumulus cells, which may indicate the advanced differentiation of cumulus cells into granulosa cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.