The organization of human epidermis: Functional epidermal units and phi proportionality

[摘要] The concept that mammalian epidermis is structurally organized into functional epidermal units has been proposed on the basis of stratum corneum (SC) architecture, proliferation kinetics, melanocyte:keratinocyte ratios (1:36), and, more recently, Langerhans cell: epidermal cell ratios (1:53). This article examines the concept of functional epidermal units in human skin in which the maintenance of phi (1.618034) proportionality provides a central organizing principle. The following empirical measurements were used: 75,346 nucleated epidermal cells per mm(2), 1394 Langerhans cells per mm(2), 1999 melanocytes per mm(2), 16 (SC) layers, 900-mum(2) corneocyte surface area, 17,778 corneocytes per mm(2), 14-d (SC) turnover time, and 93,124 per mm(2) total epidermal cells. Given these empirical data: (1) the number of corneocytes is a mean proportional between the sum of the Langerhans cell + melanocyte populations and the number of epidermal cells, 3393/17,778-17,778/93,124; (2) the ratio of nucleated epidermal cells over corneocytes is phi proportional, 75,346/17,778similar tophi(3); (3) assuming similar 14-d turnover times for the (SC) and Malpighian epidermis, the number of corneocytes results from subtraction of a cellular fraction equal to similar to2/phi(2)xthe number of living cells, 75,436 - (2/phi(2)x75,346) similar to17,778; and (4) if total epidermal turnover time equals (SC) turnover timexthe ratio of living/dead cells, then compartmental turnover times are unequal (14 d for (SC) to 45.3 d for nucleated epidermis similar to1/2phi) and cellular replacement rates are 52.9 corneocytes/69.3 keratinocytes per mm(2) per h similar to2/phi(2). These empirically derived equivalences provide logicomathematical support for the presence of functional epidermal units in human skin. Validation of a phi proportional unit architecture in human epidermis will be important for tissue engineering of skin and the design of instruments for skin measurement.

[发布日期] 2003-12-01

[关键词] epidermal kinetics;cell kinetics;melanocyte;Langerhans cell;stratum corneum