Intrinsic aging vs. photoaging: a comparative histopathological, immunohistochemical, and ultrastructural study of skin

Abstract

Cutaneous aging is a complex biological phenomenon affecting the different constituents of the skin. To compare the effects of intrinsic and extrinsic aging processes, a total of 83 biopsies were collected from sun-exposed and protected skin of healthy volunteers representing decades from the 1st to the 9th (6-84 years of age). Routine histopathology coupled with computer-assisted image analysis was used to assess epidermal changes. Immunoperoxidase techniques with antibodies against type I and type III collagens and elastin were used to quantitatively evaluate changes in collagen and elastic fibers and their ultrastructure was examined by transmission electron microscopy. Epidermal thickness was found to be constant in different decades in both sun-exposed and protected skin; however, it was significantly greater in sun-exposed skin (P = 0.0001). In protected skin, type I and III collagen staining was altered only after the 8th decade, while in sun-exposed skin the relative staining intensity significantly decreased from 82.5% and 80.4% in the 1st decade to 53.2% and 44.1% in the 9th decade, respectively (P = 0.0004 and 0.0008). In facial skin the collagen fiber architecture appeared disorganized after the 4th decade. The staining intensity of elastin in protected skin significantly decreased from 49.2% in the 1st decade to 30.4% in the 9th decade (P = 0.05), whereas in sun-exposed skin the intensity gradually increased from 56.5% in the 1st decade to 75.2% in the 9th decade (P = 0.001). The accumulated elastin in facial skin was morphologically abnormal and appeared to occupy the areas of lost collagen. Collectively, the aging processes, whether intrinsic or extrinsic, have both quantitative and qualitative effects on collagen and elastic fibers in the skin.

Survey on skin aging status and related influential factors in Southeast China

“…The symptoms of skin aging process include wrinkling, hyperpigmentation, telangiectasia, enlarged pores and actinic keratoses, and wrinkling and skin elasticity are thought to be the most evident features (El-Domyati et al, 2002;McCullough and Kelly, 2006). Meanwhile, a series of photo-damages caused by chronic UV radiation including texture abnormalities, irregular pigmentation (such as solar keratosis, solar lentigo, and seborrheic keratosis) and even skin tumors, intertwine with the inherent influences and contribute to skin aging in the long run (Rabe et al, 2006;Fisher, 2005;Stern, 2004).…”

Tissue elasticity and the ageing elastic fibre

“…The ageing process has a profound effect on the structure and function of this elastic fibre system but, as with the ageing lung, human skin accumulates damage due to both the action of normal metabolic processes and also as a result of interactions with environmental factors. In areas exposed to ultraviolet light, acute or "extrinsic" ageing processes are superimposed on underlying chronic or "intrinsic" ageing mechanisms (El-Domyati et al 2002). These two processes have distinct cosmetic and structural consequences for ageing skin.…”

Skin ageing and its treatment

“…There is general agreement, however, that the thickness of the stratum corneum does not change with age. In a study comparing the effects of intrinsic and extrinsic ageing, histopathological examination of 83 biopsies from sun-exposed and protrected skin in healthy volunteers aged 6-84 years revealed epidermal thickness to be constant across the decades in both sun-exposed and -protected skin, with the thickness found to be greater in sun-exposed skin [34]. In a different study, the spinous layer of a wrinkle was shown to be thinner at the base than at the flanks [35]; in addition, according to this study, fewer keratohyaline granules are present in the wrinkle base as compared to the flanks.…”