Stromal DNA synthesis is stimulated by young, but not serially aged, mouse mammary epithelium

Berger, Joseph J.; Daniel, Charles W.

doi:10.1016/0047-6374(83)90028-3

Cited by 23 publications

(11 citation statements)

References 6 publications

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“…DNA synthesis in stromal cells surrounding the epithelial end buds was also increased (Fig. 4A), resembling that associated with vigorously growing nor- mal glands (25). With both DNA synthesis and cAMP, a systemic effect was noted in that their levels were elevated in the contralateral control glands (Table 1).…”

mentioning

confidence: 72%

In vivo, cAMP stimulates growth and morphogenesis of mouse mammary ducts.

Silberstein¹,

Strickland²,

Trumpbour³

et al. 1984

Proc. Natl. Acad. Sci. U.S.A.

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In culture, cAMP is known to be mitogenic for mammary cells and several other epithelia, but evidence for a similar role in vivo has been only correlative. We have used plastic implants to cause slow release of cholera toxin and other cAMP-active agents to local areas of mammary glands in ovariectomized mice. Elevated levels of intracellular cAMP around the implants promoted vigorous growth and normal ductal morphogenesis, while distant sites were unaffected. Local effects of cAMP included restoration of normal ductal caliber, formation of new end buds, and reinitiation of DNA synthesis in both epithelium and surrounding stroma. Thus, cAMP is both a mitogenic and a morphogenetic factor in this tissue.Numerous in vitro studies have shown cAMP to be growth promoting for mouse, rat, and human mammary epithelia (1-4) and for a variety of other epithelial cell types (5-8). In situ, cAMP levels increase as the mammary gland grows during pregnancy (9, 10), and they are elevated in several breast carcinomas (11,12). To obtain more direct evidence as to whether cAMP may function as an intracellular mediator of hormone or growth factor action in the mammary gland, we investigated the effects of raising cAMP levels in small regions of the mouse mammary gland by using slow-release plastic implants.End buds, the primary sites of mammary epithelial proliferation in subadult virgin mice, are complex highly mitotic structures comprised of the stem cell progenitors of myoepithelial and ductal cells (13). As the growth points for the ductal tree, end buds are the focus of mammary growth regulatory influences during this stage in development of the gland (14). We here present evidence that, in situ, local elevation of cAMP stimulated formation of new end buds in regressed ducts, apparently replacing the normal hormonal requirements for this type of development. CT Dosage. Commercial CT contains 4.8% by weight of toxin protein, the bulk of the preparation being NaCl and Tris HCl (55% and 37.6%, respectively). The most commonly used implant was prepared with 1 mg of the commercial preparation dissolved in 0.25 ml of Elvax. The dried Elvax pellet weighed -40 mg and contained 48 ,ug of toxin protein or 1.2 ,ug in an implant-sized piece weighing 1 mg. The useful dose range for this implant type is 0.1-1.2 ,ug of toxin. MATERIALS AND METHODSRelease of CT from Elvax. The release kinetics of CT was studied in vitro. Pellets prepared with either 1 mg or 10 mg of the toxin were cut into implant-sized pieces, weighed, and sealed in nylon bags (Nitex), which were then placed in 1.5 ml of normal saline at 37°C on a rotator (1 rpm). At 24-hr intervals, the bags were removed and the saline was assayed for protein against a CT standard using the Bradford method (16). Bags were then rinsed and replaced in fresh saline. An adequate amount of Elvax with toxin was available for three trials, one of which is shown here (Fig. 5); the release profile was the same for all three trials. Surgical Implantation. The abdominal skin of Nembutalanesthet...

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mentioning

confidence: 72%

In vivo, cAMP stimulates growth and morphogenesis of mouse mammary ducts.

Silberstein¹,

Strickland²,

Trumpbour³

et al. 1984

Proc. Natl. Acad. Sci. U.S.A.

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“…The lung model also predicts that epithelium-generated signals should alter gene expression in nearby connective tissue and there is good evidence that this occurs in the mammary gland. As ducts extend, numerous DNA-synthetic cells were detected up to 250 m in front of end buds, a phenomena not seen near growthstatic ducts or in empty stroma (Berger and Daniel, 1983). In addition, large numbers of neutrophils and other white blood cells aggregate around end buds, indicating that chemoattractants are generated in the vicinity (unpublished data).…”

Section: Ductal Extension and Reshaping Thementioning

confidence: 92%

Postnatal mammary gland morphogenesis

Silberstein

2001

Microsc. Res. Tech.

160

100

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“…subject of LREC in the rodent mammary gland (Welm et al, 2002;Zeps et al, 1996). However, in 1983, a paper was published (Berger and Daniel, 1983) describing the stimulation of DNA synthesis in the proximate mammary stroma associated with actively growing terminal end buds. Here, we also observed DNA synthesis in the mammary stroma surrounding the growing end buds and subsequently the appearance of label-retaining stromal cells following the 5-6 week chase of the 3 HTDr.…”

Section: Discussionmentioning

confidence: 99%

Label-retaining epithelial cells in mouse mammary gland divide asymmetrically and retain their template DNA strands

2005

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It has been postulated that the stem cells of somatic tissues protect themselves from mutation and cancer risk by selective segregation of their template DNA strands. Self-renewing mammary epithelial stem cells that were originated during allometric growth of the mammary ducts in pubertal females were labeled using [3H]-thymidine (3HTdR). After a prolonged chase during which much of the branching duct morphogenesis was completed, 3HTdR-label retaining epithelial cells (LREC) were detected among the epithelium of the maturing glands. Labeling newly synthesized DNA in these glands with a different marker, 5-bromodeoxyuridine(5BrdU), resulted in the appearance of doubly labeled nuclei in a large percentage of the LREC. By contrast, label-retaining cells within the stroma did not incorporate 5BrdU during the pulse, indicating that they were not traversing the cell cycle. Upon chase, the second label (5BrdU) was distributed from the double-labeled LREC to unlabeled mammary cells while 3HTdR was retained. These results demonstrate that mammary LREC selectively retain their 3HTdR-labeled template DNA strands and pass newly synthesized 5BrdU-labeled DNA to their progeny during asymmetric divisions. Similar results were obtained in mammary transplants containing self-renewing, lacZ-positive epithelial cells suggesting that cells capable of expansive self-renewal may repopulate new mammary stem cell niches during the allometric growth of new mammary ducts.

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Stromal DNA synthesis is stimulated by young, but not serially aged, mouse mammary epithelium

Cited by 23 publications

References 6 publications

In vivo, cAMP stimulates growth and morphogenesis of mouse mammary ducts.

In vivo, cAMP stimulates growth and morphogenesis of mouse mammary ducts.

Postnatal mammary gland morphogenesis

Label-retaining epithelial cells in mouse mammary gland divide asymmetrically and retain their template DNA strands

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