The Effect of Tretinoin Intradermal Injection on Dermal Thickening in Rabbit

ABSTRACT

Tretinoin(all-trans retinoic acid) is a metabolite of vitamin A and it is useful in the treatment of photoaging skin. Photoaging skin is characterized by wrinkles, mottled pigmentation, dry and rough skin, and loss of skin tone. Current use of topical tretinoin mainly acts on the epidermis, requires a long period to obtain the desired results and may cause skin hyperpigmentation. A combination of topical and injectable tretinoin has been used to reduce the treatment period as a result of its potentialized effect on the dermis when compared to graditional topical cream use. in this study, we observed histologic alterations in 5 white rabbits after using 0.05% topical tretinoin cream and 0.1% injectable tretinoin. Tretinoin was treated on the rabbits ears-group 1 and 2 on the right ear for study 1, and group A and B on the left ear for study 2. Study 1 was done to differentiate whether the dermal thickening is due to the simple physical stretching of dermis by intradermal injection, or whether it is duer to the histologic change by tretinoin. In group 1, saline was injected intradermally and in group 2, tretinoin was injected intradermally. Study 2 was done to compare the dermal thickening between the topical tretinoin cream treatment group (group A) and the combined topical and injectable tretinoin group (group B). Injection was done once a week immediately followed by 340nm blue light skin exposure. These treatment were done for 12 weeks. We harvested skin stripe from all group, group 1 and 2, and group A and B respectively, after 2, 6, and 12 weeks after treatment. Histologic differences were observed and measured. Dermal thickening was observed in group 2 and in group B(p<0.05). The results showed that intradermal injection of tretinoin mainly acts on the dermis and potentialtes the effect on photo-aging skin and fine wrinkles.