Epidermal differentiation in normal and growth-retarded infants: studies in two animal models and in human babies.

The influence of prenatal growth retardation on epidermal growth and keratinization was studied in small-for-dates human babies, runt piglets and in rat fetuses subject to maternal protein deprivation. In the human babies and rat fetuses growth retardation was associated with reduced epidermal growth but normal patterns of differentiation were present. Thus, epidermal thickness was less and keratinizing zones narrower than seen in normal weight individuals. In the runt (small-for-dates) piglet, epidermal development differed from that seen in normal weight piglets of the same gestational age and from that seen in the human and rat. The epidermis was thicker with a negligible stratum granulosum and with the stratum corneum containing nucleated cells, a condition resembling 'parakeratosis'. This pattern was less often seen in normal weight piglets. Differences between the skins of the three speecies studied at a perinatal stage may be related to clear dissimilarities which exist in the tissues later. Parakeratosis as a transitory phase in the development of pig skin is probably related to a higher rate of epidermal keratinization in this species than occurs in either human babies or rat fetuses.