C. Ferraris et al., ADULT EPIDERMAL-KERATINOCYTES ARE ENDOWED WITH PILOSEBACEOUS FORMING ABILITIES, The International journal of developmental biology, 41(3), 1997, pp. 491-498
Pluristratified epithelia of adult vertebrate skin continuously regene
rate from stem cells, and the question still arises as to whether thos
e cells are committed to the production of only one cell lineage, or i
n contrast they conserve their embryonic pluripotentiality. In order t
o investigate the abilities of adult cultured as well as wound healing
epidermis, heterospecific fibroblast-keratinocyte recombinations were
performed, which allow unquestionable identification of the cells imp
licated in the structures that differentiate. Adult human cultured bre
ast epidermal cells and full-thickness wound healing from human facial
skin and foreskin were associated with either rabbit embryonic tricho
genic dermis or cultured dermal papilla cells of adult rat, before gra
fting onto nude mice for two weeks to one month. In situ hybridization
with a human specific sequence Alu probe labeled the human cells, whe
reas implanted rabbit or rat and host mouse cells were distinguished b
y the Hoechst staining of their nuclei. The results show that human ad
ult cultured breast epidermal cells are able to form hair buds and to
participate in hair follicle formation, while adult healing epidermis
from a sparsely hairy skin as the human face or the dorsal skin of nud
e mouse, or even from a glabrous epidermis as the human foreskin, are
able to differentiate pilosebaceous units. Although a follicular origi
n of the involved keratinocytes cannot be excluded in the three first
cases, the formation of hair and sebaceous glands by foreskin keratino
cytes of children 2 to 10 years-old establishes the cutaneous appendag
e ability of the interfollicular epidermal stem cells. The formation o
f interspecies mosaic follicles also highlights the fact that there mu
st be a significant level of commonality in the interactive signaling
molecules used by epithelial cells from different species.