Submitted to: Experimental Biology and Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2009
Publication Date: 4/1/2009
Citation: Capuco, A.V., Evock-Clover, C.M., Minuti, A., Wood, D.L. 2009. In vivo expansion of the mammary stem cell population by xanthosine infusion. Experimental Biology and Medicine. 234:475-482.
Interpretive Summary: Mammary stem cells provide for growth and maintenance of the mammary gland and are therefore likely targets for means to improve the productivity and efficiency of dairy animals. Xanthosine, a naturally occurring metabolite important for DNA synthesis, was infused through the teat into two mammary glands of Holstein calves, while the other two glands served as controls. Using a previously described method to identify mammary stem cells based upon their ability to retain bromodeoxyuridine for an extended period of time, we determined that xanthosine infusion increased the number of mammary stem cells. This was supported by an increase in telomerase activity in the treated mammary glands. Telomerase is an enzyme that is present in immortal stem cells but not normal mammary cells. This research indicates that in vivo treatment with xanthosine can be used to increase the number of mammary stem cells. This is the first demonstration of an in vivo treatment to increase the endogenous population of mammary stem cells. The treatment has utility for dairy management and for biomedical research.
Technical Abstract: Mammary stem cells provide for growth and maintenance of the mammary gland and are therefore likely targets for means to improve the productivity and efficiency of dairy animals. Xanthosine treatment was previously shown to promote expansion of hepatic stem cells in vitro. The objective of this study was to determine if in vivo treatment with xanthosine can increase the mammary stem cell population. Xanthosine was infused into the right mammary glands of four Holstein calves (3 months old) for 5 consecutive days. Immediately after each xanthosine treatment, calves were injected intravenously with 5-bromo-2-deoxyuridine (BrdU). Forty days after the final treatment, calves were euthanized and mammary tissue harvested. BrdU-label retaining epithelial cells (LREC) were detected immunohistochemically and quantified. Retention of BrdU was used as a marker for putative bovine mammary stem cells. Infusion of xanthosine into the bovine mammary gland significantly increased the number of LREC in treated glands compared to contralateral control glands (P < 0.05). LREC averaged 0.4% of epithelial cells in control glands and 0.8%in xanthosine-treated glands. The increase in LREC in xanthosine-treated glands was supported by a concomitant increase in telomerase activity (P < 0.01) and a correlation between LREC and telomerase (P < 0.05; r2 = 0.7). Data indicate that in vivo treatment with xanthosine can be used to increase the number of mammary stem cells. This is the first demonstration of an in vivo treatment to increase the endogenous population of mammary stem cells, with utility for biomedical research and dairy management.