Effect of cigarette smoke and treatment with relaxin on guinea pig skin

Cigarette smoking causes microvascular dysfunction and skin aging. Relaxin, primarily but not exclusively involved in reproduction, has connective tissue among its targets. Within a project on the interference of relaxin with the effects of smoke on guinea pigs, we examined the skin response to those stimuli. Adult guinea pigs were exposed to cigarette smoke daily for 8 weeks, and some of them were treated also with relaxin, 1 or 10 µg/die. Controls were treated with relaxin vehicle alone. The skin was analyzed by light and electron microscopy and histochemistry for mast cells and the collagen specific chaperonin Hsp47. The epidermis appeared unaffected by any treatment. In the superficial dermis, smoke led to a decrease in mast cell number and intensity of astra blue staining, suggestive of granule discharge. Relaxin caused further significant reduction in mast cell number. In the superficial and deep dermis, the staining intensity of Hsp47 positive cells, assumed as active fibroblasts, increased upon smoke. The staining intensity decreased gradually in the superficial dermis upon relaxin, reaching significance after treatment with 10 µg/die relaxin, while in the deep dermis it decreased significantly upon treatment with 1 µg/die relaxin and underwent further, significant increase with 10 µg/die relaxin. The results suggest that relaxin can enhance skin mast cell secretory response, possibly antagonizing nicotine induced vasoconstriction and, depending on dose and localization of responding cells, can counteract the profibrotic stimulus of smoke on dermal fibroblasts.