Sheffield L G
Dairy Science Department, University of Wisconsin, Madison 53706.
J Dairy Sci. 1988 Oct;71(10):2855-74. doi: 10.3168/jds.S0022-0302(88)79881-1.
Mammary gland development consists of a series of very highly ordered events involving interactions among a number of distinct cell types. An important aspect of mammary gland development is that the mammary gland consists of a fat pad of mesodermal origin into which epithelial cells of ectodermal origin proliferate. This proliferation of epithelial cells into the mammary fat pad is the subject of this review. The nature of the stroma into which epithelial cells proliferate is of considerable importance in determining the structure of the resulting gland. In mice, white adipose tissue appears to be required for normal mammary development. Transplantation of mammary epithelia to other types of stroma does not support epithelial growth or result in abnormal growth. To date, a synthetic substratum capable of mimicking white adipose tissue has not been developed. Although collagen gel cultures are generally considered superior to glass or plastic substratum in supporting near normal epithelial growth, the technique has not advanced to the point that the in vivo growth pattern is duplicated. Recent research on the generation of chimeric mammary tissue (by transplanting mammary epithelia from rats, cows, and women to the mammary fat pads of athymic nude mice) suggests that there are important species differences in the stromal requirements for mammary gland development. In particular, extensive and expansive growth of rat mammary tissue is observed in mouse mammary fat pads. However, the mouse mammary fat pad appears incapable of supporting expansive growth of bovine or human mammary epithelia. The reason for this difference is not clear. However, human and bovine mammary epithelia may require the presence of more fibrous (collagenous) tissue than rodent mammary epithelia for normal proliferation.
乳腺发育由一系列高度有序的事件组成，涉及多种不同细胞类型之间的相互作用。乳腺发育的一个重要方面是，乳腺由中胚层来源的脂肪垫组成，外胚层来源的上皮细胞在其中增殖。上皮细胞向乳腺脂肪垫的这种增殖是本综述的主题。上皮细胞增殖所进入的基质的性质在决定最终腺体的结构方面相当重要。在小鼠中，白色脂肪组织似乎是正常乳腺发育所必需的。将乳腺上皮移植到其他类型的基质中不能支持上皮生长或导致异常生长。迄今为止，尚未开发出能够模拟白色脂肪组织的合成基质。尽管胶原凝胶培养在支持近乎正常的上皮生长方面通常被认为优于玻璃或塑料基质，但该技术尚未发展到能够复制体内生长模式的程度。最近关于嵌合乳腺组织生成的研究（通过将大鼠、牛和人的乳腺上皮移植到无胸腺裸鼠的乳腺脂肪垫中）表明，在乳腺发育的基质需求方面存在重要的物种差异。特别是，在小鼠乳腺脂肪垫中观察到大鼠乳腺组织的广泛和扩展性生长。然而，小鼠乳腺脂肪垫似乎无法支持牛或人乳腺上皮的扩展性生长。这种差异的原因尚不清楚。然而，与啮齿动物乳腺上皮相比，人和牛的乳腺上皮正常增殖可能需要存在更多的纤维（胶原）组织。
