J. soc. cos. CHEM. 15, 509-518 (1964) MEASURING THE EFFECTS OF TOPICAL PREPARATIONS UPON THE HEALING OF SKIN WOUNDS By SID•½•-¾ Govr, PH.D., and IRVIN( LEVENSTEIN, PH.D.* Presented September 2¾-25, I963, Seminar, Boston, Mass. ABSTRACT Topically applied substances often come in contact with skin wounds. The effects of a number of such preparations on the healing of a standardized, surgically inflicted skin wound were studied. Using the mouse as the experimental animal, a direct relationship was found between lapsed time of repair and wound strength, as measured tensiometrically. The wound tensile strength of control (untreated) mice was compared with that of •roups of animals treated with prep- arations which had been reported to have an effect on healing. Results are given on the effects of treatment with ointments containing fat soluble vitamins, Aloe vera extract, a fluorinated corticosteroid, the same cortlcosteroid in a cream base, an allantoin-coal tar mixture, a pantothenylol cream, and the steam distillate from Artemisia tri- denrata. The determination of the tensile strength of segments of healing skin wounds appears to be a valuable tool in the study of the effects of topical agents. Cosmetic and drug preparations are frequently applied to skin area which have been cut or otherwise injured. This may be done intentionally for the purpose of the treatment, or it may be coincidental to the primary use of the preparation. Regardless of the reason, it is important to have some knowledge of the effects of these substances upon the healing of wounds. An investigation was undertaken in our laboratory to determine whether the effects of topically applied preparations on the healing of skin wounds could be measured quantitatively. Research in skin physiology has made clearer many of the biochemical, physiological and histological changes that take place as injured tissue is * Leberco Laboratories, Roselie Park, N..[. 509

510 JOURNAL Oh' THE SOCIETY OF COSMETIC CHEMISTS restored to its normal state. There are shifts in the mucopolysaccharides, glycoproteins, amino acids and RNA concentrations (1-7). Cellular migrations and multiplications occur to replace lost tissue (8), and complex biophysicochemical reactions result in the formation of collagen fibers which help to restore tissue strength (3, 5, 9). The effects of a wide variety of substances, administered both system- ically and topically, on the reparative processes have also been studied. Nutrients, hormones, antimicrobial agents, botanicals and an array of pharmacologically active compounds have been evaluated. Among these, cortisone derivatives, Acr['H, thyroxine, hyaluronidase, reserpine and 5- hydroxytryptamine have been reported to retard the healing of wounds (10-19). Promotion of healing has been ascribed to glycosides of Centella asiafica, extracts of,4/oe vera, a]lantoin, protein hydrolysates, nitrofurans, pantothenates and hyaluronic acid (20-30). Gross and histological observations, changes in the concentration of various tissue constituents, and the strength of the healing wound are the criteria most often used to determine healing rates and the effects of treat- ment upon them. As has been mentioned, many biological and biochemical mechanisms come into play during healing and may be considered as forces directed toward returning traumatized tissue to a normal condition. The strength of the healing wound is a general measure of the progress toward normalcy and may be thought of as the biological resultant of the various forces acting in and on the affected area. It is a comparatively simple measurement and represents a direct approach to the problem (9, 19,31,32). Two general methods of skin wound tensiometry have been described and used. Prudden and co-workers (33-41), by measuring the pressure, applied from within, required to disrupt abdominal incisions in the rat, have reported that the application of ground, acid-pepsin digested, bovine tracheal cartilage stimulated healing. The other technique consists of determining the force (usually as measured by weight) required to cause the separation of the edges of a standard segment of healing skin wound. This wound-strip method was used in the studies reported here. Standardization of the method of injury has also been approached in a variety of ways. Burns, blows and cuts have all been used in the reports cited. A surgical incision of closely controlled length and depth was used in our work, since it could be reproduced with acceptable precision. MATERIAlrS AND METHODS Test Atnimals CF-1 male mice, 30-40 days old, and weighing 18 to 25 g. were used in all the experiments.