Background: The extracellular matrix protein 1 (ECM1) is expressed in human skin and plays an important role in its normal structure and function. In the rare genetic skin disease lipoid proteinosis, which is characterized by a loss-of-function mutation in the ECM1 gene, skin areas habitually exposed to the sun may show a more severely scarred and photoaged appearance. However, no data are available on the possible involvement of ECM1 expression in intrinsic and extrinsic skin ageing.
Objectives: We hypothesized that ECM1 expression in human skin is regulated by age- and ultraviolet (UV)-dependent mechanisms.
Methods: Skin biopsies from 12 patients with histologically confirmed solar elastosis, from non-UV-exposed sites of 12 age-matched controls and 12 young subjects were analysed. To evaluate the influence of acute UV exposure, buttock skin of 10 healthy subjects was irradiated repetitively on 10 days with a solar simulator and compared intraindividually with non-UV-treated contralateral sites. The expression of ECM1 was investigated by immunohistochemistry using an ECM1 antibody detecting ECM1a and ECM1c isoforms. Semiquantitative analysis of staining intensity was carried out by densitometric image analysis.
Results: In normal human skin ECM1a and ECM1c are expressed mainly in the basal cell layers of epidermal keratinocytes and in dermal vessels. For the first time, an expression in the outer root sheath of hair follicles, in sebaceous lobules and epithelium of sweat glands is described. Intrinsically (UV-protected) aged skin shows a significantly reduced expression in basal and upper epidermal cell layers compared with young skin. In photoaged skin, expression is significantly increased within the lower and upper epidermis compared with age-matched UV-protected sites. Importantly, after acute UV exposure in young healthy subjects expression of ECM1 is markedly increased in both lower and upper epidermal cell layers.
Conclusions: This is the first study to demonstrate a regulation of ECM1 expression in human skin by age and UV exposure. These data suggest that ECM1 expression may represent a cutaneous stress response to acute and chronic UV irradiation.