Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2012
Publication Date: 6/1/2012
Publication URL: http://handle.nal.usda.gov/10113/56514
Citation: Safayi, S., Korn, N., Bertram, A., Akers, M.R., Capuco, A.V., Pratt, S.L., Ellis, S. 2012. Myoepithelial cell differentiation markers in prepubertal bovine mammary gland: Effect of ovariectomy. Journal of Dairy Science. 95:2965-2976. Interpretive Summary: Ovariectomy alters prepubertal development of mammary myoepithelial cells (MC), but the mechanisms involved are not well understood. We therefore analyzed the expression of MC differentiation markers, a-smooth muscle actin (SMA) and the common acute lymphoblastic leukemia antigen (CD10), in intact and ovariectomized heifers at 55, 70, 85, 100, 130 and 160 d of age. Our results showed that ovariectomy affects MC expression of both SMA and CD10 as well the pattern of MC development. Given that MC are known to limit parenchymal growth in other species, our observations open new avenues for future studies on the regulation of prepubertal mammary development.
Technical Abstract: We have previously reported that ovariectomy alters prepubertal development of mammary myoepithelial cells (MC), but the mechanisms involved are not well understood. We therefore analyzed the expression of the myoepithelial differentiation markers a-smooth muscle actin (SMA) and the common acute lymphoblastic leukemia antigen (CD10) in mammary parenchymal samples from intact (INT) and ovariectomized (OVX) heifers. On d 40, Holstein heifers underwent either an ovariectomy (OVX; n = 16) or sham (INT; n = 21) operation. At d 55, 70, 85, 100, 130 and 160 of age, samples were collected and used for multispectral imaging to quantitatively assess immunofluorescent staining for myoepithelial cell (MC) markers. Fluorescent intensity (FI) of the markers was normalized against a control sample and then evaluated statistically using Mixed procedures in SAS. In the basal epithelial layer, CD10 FI was lower (P = 0.04) and SMA FI was higher (P = 0.05) in OVX than INT. The ratio of SMA to CD10 FI, as a proxy indicator for MC differentiation, increased in OVX compared with INT after d55 (P < 0.05), and remained approximately four times higher from d100 onwards (P < 0.01). The staining for SMA was characterized by a progressive concentration along the basal aspect of cells while CD10 expression became localized on the apical surface. In both INT and OVX, there were also basal CD10-/SMA- cells, some of which appeared to span the distance from basement membrane to the ductal lumen. Interestingly, we also observed CD10+ cells along the lumenal space, and lumenal CD10+ cells were more prevalent in OVX than INT heifers (P = 0.02). Our results show that ovariectomy affects MC expression of both SMA and CD10 as well the pattern of MC development. Given that MC are known to limit parenchymal growth in other species, our observations suggest new avenues for investigating the regulation of prepubertal bovine mammary development.