Schmiegelow P, Nüssgen A, Grasedyck K, Lindner J
Z Gerontol. 1986 May-Jun;19(3):179-89.
The clinically relevant morphological changes of the skin during aging can be summarized by the term "senile atrophy". The changes are a diminished thickness of epidermis with a reduced mitosis rate of epidermal basal cells, shortened and attenuated rete ridges, reduction of epidermal appendages, and a decreased number of fibroblasts and capillaries in the dermis. Corresponding to these morphological findings regarding the cell number in the senile skin (cutis) we found a slight decrease in the DNA concentration of human and rat cutis. The specific DNA activity (3H-thymidine incorporation rate related to DNA concentration) decreased in presenile versus adult animals. The mesenchymal changes in the dermis have been morphologically described by the term "senile elastosis" or "elastoid collagen degeneration", but in fact they correspond to a progressive collagen denaturation with aging. The total collagen concentration, here determined as the hydroxyproline concentration in the human cutis, shows almost constant values from the 3rd until the 9th decade of life in both sexes. This is also true for the skin of two different rat strains. The insoluble collagen fraction shows a relative increase to the disadvantage of the soluble collagen fractions, which can be interpreted as an indicator of a decelerated collagen turnover. In spite of the decelerated turnover, i.e. a prolonged half-life of the collagen metabolism in the skin, the indicators of the collagen neosynthesis (14C-proline incorporation rate, specific hydroxyproline activity, prolyl-hydroxylase activity) are significantly elevated in the cutis of presenile versus adult rats. Any connection of these findings with a possible change in the distribution of collagen types in the senile skin (e.g. pericapillar fibrosis with increase of collagen type I as well as changes in the distribution of type I, III, IV and V) can only be discussed at present. The glycosaminoglycans in the cutis show a minimal increase of the total content of hexosamines and uronic acids with a significant shift in the ratio of the glycosaminoglycan components in favour of dermatan sulfate and keratan sulfate and to the disadvantage of hyaluronic acid and partly also of chondroitin-4-sulfate and -6-sulfate. The neosynthesis of sulfated glycosaminoglycans (indicator method: 35S-sulfate incorporation rate) is only slightly increased whereas the enzyme activities being specific for the glycosaminoglycan catabolism (beta-glucuronidase, beta-N-acetyl-glucosaminidase) are significantly decreased with aging of the skin.(ABSTRACT TRUNCATED AT 400 WORDS)
衰老过程中皮肤临床上相关的形态学变化可用“老年性萎缩”一词概括。这些变化包括表皮厚度变薄，表皮基底细胞有丝分裂率降低， rete 嵴缩短变细，表皮附属器减少，真皮中成纤维细胞和毛细血管数量减少。与老年皮肤（真皮）中细胞数量的这些形态学发现相对应，我们发现人和大鼠真皮中 DNA 浓度略有下降。与成年动物相比，老年前期动物的比 DNA 活性（与 DNA 浓度相关的 3H - 胸腺嘧啶掺入率）降低。真皮中的间充质变化在形态学上被描述为“老年性弹性组织变性”或“类弹性胶原变性”，但实际上它们对应于随着年龄增长而发生的渐进性胶原变性。此处将人真皮中的总胶原浓度测定为羟脯氨酸浓度，在两性中从生命的第 3 个十年到第 9 个十年几乎保持恒定值。两种不同大鼠品系的皮肤也是如此。不溶性胶原部分相对增加，而可溶性胶原部分减少，这可解释为胶原周转减慢的一个指标。尽管周转减慢，即皮肤中胶原代谢的半衰期延长，但与成年大鼠相比，老年前期大鼠真皮中胶原新合成的指标（14C - 脯氨酸掺入率、比羟脯氨酸活性、脯氨酰羟化酶活性）显著升高。目前只能讨论这些发现与老年皮肤中胶原类型分布可能变化（例如毛细血管周围纤维化伴 I 型胶原增加以及 I、III、IV 和 V 型分布变化）之间的任何联系。真皮中的糖胺聚糖显示己糖胺和糖醛酸的总含量略有增加，糖胺聚糖成分的比例发生显著变化，有利于硫酸皮肤素和硫酸角质素，而不利于透明质酸，部分也不利于硫酸软骨素 - 4 - 硫酸盐和 - 6 - 硫酸盐。硫酸化糖胺聚糖的新合成（指标方法：35S - 硫酸盐掺入率）仅略有增加，而糖胺聚糖分解代谢特有的酶活性（β - 葡萄糖醛酸酶、β - N - 乙酰 - 葡糖胺酶）随着皮肤衰老而显著降低。（摘要截于 400 字）
