J. Soc. Cosmet. Chem., 32, 15-26 (January/February 1981) Use of nonintrusive tests to monitor age-associated changes in human skin GARY L. GROVE, PH.D., ROBERT M. LAVKER, PH.D., ERHARD HOELZLE, M.D., and ALBERT M. KLIGMAN, M.D., PH.D., Simon Greenberg Foundation, Skin Study Center, 3901 Market Street, Philadelphia, PA 19104. Received July 24, 1980. Presented at the Society of Cosmetic Chemists' Annual Scientific Seminar, San Francisco, CA, May 15-16, 1980. Synopsis Nonintrusive tests can be used to objectively characterize and quantitatively evaluate in vivo those changes in the physiological properties of skin due to aging. Such a testing procedure presents no untowards risks and has proven to be quite palatable to normal healthy volunteers. A number of age-associated changes in skin structure and function can be monitored in this manner. These include changes in SKIN SURFACE ANATOMY such as loss of DERMATOGLYPHICS and altered patterns of CORNEOCYTE DESQUAMATION. Physiological decrements such as diminished eccrine sweating, epidermal CELL RENEWAL and HEALING of superficial skin wounds can also be evaluated. Moreover, by using a variety of excitants which when placed on the skin induce specific reactions, viz. erythema, wheals, stinging, etc., an age associated loss to express these reactions has been demonstrated. INTRODUCTION It seems likely that changes which occur in human skin with advancing age may be of some value in monitoring the senescent process not only for that organ but perhaps for the entire individual as well (1). Such an ability to measure aging biologically on the basis of structural and functional alterations in skin rather than just chronologically on the basis of birth certificate information would be of great benefit to the investigative gerontologist. Unfortunately, most testing procedures which are used to study skin structure and function require biopsies or some other surgical manipulation to be performed. There is no doubt that most human subjects, especially those with no dermatological problems, find these invasive testing procedures objectionable. What is really needed is a testing strategy that is palatable to human volunteers. Such procedures should be conveniently administered, cause little or no discomfort, present no untoward risks and leave no permanent scars or pigmentary changes. The object of this paper is to summarize some preliminary results of a pilot study of aging human skin designed primarily to test the feasibility of this nonintrusive approach. This is a cross-sectional investigation and involves a comparison of two 15

16 .JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS age-cohorts: young adults 20-35 years of age and older adults 60-75 years of age. Both groups are comprised of normal healthy white volunteers (6 males and 6 femalesin each) who had given informed consent. To avoid differences environmental conditions or protocols, both cohorts were tested concurrentinallandchangetodue assessments were made independently by three graders. REPLICAS AND SKIN SURFACE BIOPSIES The skin surface is organized into complex patterns of ridges and furrows which presumably enable the stratum corneum to undergo deformation in a varietyof directions without subsequent loss of integrity (2). With the exception of palma surfaces ("finger prints") information on the dermatoglyphics of the remainin body areas is minimal, especially regarding age changes. With this in mind a special technique has been developed which for the studying dermatoglyphics, is superior to the usual replicas using si purposeofwaxdental impressions. •icone or This entails applying a thin layer of polyvinylidine chloride emulsio (Duran, Merck) which is actually a liquid form of Saran Warp©. When dry, a thin sheet can be peeled off which is an exact negative replica of the underlying skin surface. This translucent specimen serves as a permanent record of the dermatoglyphthatof subject. Recent studies indicate that the dermatoglyphics of older irregular and lack the orderly arrangement of geometric patterns typical the youn (3). Exposed areas seem to exhibit the greatest alteration in dermatoglypwithofhighlyareadults patterns in some areas of the dorsal hand being almost totally obliterated (Figure 1). g . • ,.--, • • -,• • ..•'..' •:" . Figure 1. a) Dermatoglyphic pattern of the dotsurn of the hand of the young. Major (ML) and (SL) l•es traverse to form a highly ordered pattern of triangles. WithM the triangles the corneocytofarehandsecondatheof arranged in a honeycomb fashion (arrow) (x 15). b) Dermatoglyphic pattern of the dotsurn the old. Note the lack of an ordered geometric pa•ern due to absence of secondary IMes. Remnants of the honeycombed corneocytes are occasionally obse•ed (arrow) (x 15).