Comparative aspects of the inner root sheath in adult and developing hairs of mammals in relation to the evolution of hairs
Comparative aspects of the inner root sheath in adult and developing hairs of mammals in relation to the evolution of hairs
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DOI：
10.1111/j.0021-8782.2004.00324.x
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发表时间：
2004-09-01
影响因子：
2.4
通讯作者：
Alibardi, L
中科院分区：
文献类型：
--
作者：
Alibardi, L
内根鞘(IRS)允许毛发穿过表皮表面。单孔类和有袋类IRS和毛状藻的精细结构尚不清楚。用电子显微镜和免疫细胞化学方法，研究了毛滴虫和有袋动物毛发中毛滴虫蛋白和谷氨酰胺转氨酶的定位，并与胎盘毛发中的毛滴虫蛋白进行了比较。在这里研究的所有哺乳动物中的鞭毛菌素都是由一种针对绵羊鞭毛菌素的多克隆抗体识别的。这种普遍的免疫反应性表明，哺乳动物中存在着毛滴虫蛋白的共同表位。在分化IRS细胞时，不同大小的Trichohyalin颗粒由免疫标记的无定形基质和10-12 nm厚的角蛋白细丝网络组成。谷氨酰胺转氨酶标记存在于角蛋白束和Trichohyalin颗粒之间，以及内根鞘终末分化细胞的凝集核中。单孔毛细胞的红外光谱是多层的，但缺乏可区分的Henle层。IRS的角化决定了纤维角质层的雕刻，然后从毛囊中脱落，使毛发纤维在表皮表面退出。假设Henle、Huxley和IRS角质层中的IRS的分层来自于更简单的组织，就像在单孔动物的IRS中出现的那样。IRS被认为是毛发在不损伤表皮的情况下退出毛发所需的局部脱落层。哺乳动物表皮进化过程中IRS的形成使皮肤内部产生的毛发在生理上得以退出。毛发在可能的原始皮肤中的特殊形态发生，例如单孔动物(具有某些爬行动物特征的哺乳动物)或一些啮齿动物的尾巴(鳞片皮肤)，可能解释毛发的进化。在单孔动物和啮齿动物的尾部皮肤中，真皮乳头仍位于发夹的近侧，形成两侧对称的毛发胎座。乳头逐渐被向下生长的发夹包围，直到形成具有放射状对称的真皮乳头。据推测，爬行动物鳞片的扩展毛乳头逐渐缩小为治疗性爬行动物的细小而深的乳头，哺乳动物产生了毛发。
The inner root sheath (IRS) allows the exit of hairs through the epidermal surface. The fine structure of monotreme and marsupial IRS and trichohyalin is not known. Using electron microscopy and immunocytochemistry, the localization of trichohyalin and transglutaminase have been studied in monotreme and marsupial hairs, and compared with trichohyalin localization in placental hairs. Trichohyalin in all mammalian species studied here is recognized by a polyclonal antibody against sheep trichohyalin. This generalized immunoreactivity suggests that common epitopes are present in trichohyalin across mammals. In differentiating IRS cells, trichohyalin granules of variable dimensions are composed of an immunolabelled amorphous matrix associated with a network of 10-12-nm-thick keratin filaments. Transglutaminase labelling is present among keratin bundles and trichohyalin granules, and in condensed nuclei of terminally differentiating cells of the inner root sheath. The IRS in monotreme hairs is multistratified but lacks a distinguishable Henle layer. Cornification of IRS determines the sculpturing of the fibre cuticle and later shedding from the follicle for the exit of the hair fibre on the epidermal surface. It is hypothesized that the stratification of IRS in Henle, Huxley and IRS cuticle layers is derived from a simpler organization, like that present in the IRS of monotremes. The IRS is regarded as a localized shedding/sloughing layer needed for the exit of hairs without injury to the epidermis. The formation of the IRS during the evolution of mammalian epidermis allowed the physiological exit of hairs produced inside the skin. The peculiar morphogenesis of hairs in possible primitive skins, such as those of the monotremes (mammals with some reptilian characteristics) or the tails of some rodents (a scaled skin), may elucidate the evolution of hairs. In monotreme and rodent tail skin, the dermal papilla remains localized on the proximal side of the hair peg and forms a hair placode with bilateral symmetry. The papilla is progressively surrounded by the down-growing hair peg until a dermal papilla with radial symmetry is formed. It is speculated that the progressive reduction of the extended dermal papilla of reptilian scales into small and deep papillae of therapsid reptiles produced hairs in mammals.