Expression of apoptosis- and cell cycle-related proteins in epidermis of venous leg and diabetic foot ulcers.

BACKGROUND

Epithelialization of cutaneous ulcers is a long-lasting process. To study the pathomechanism of impaired epithelialization, we evaluated the role of cell cycle- and apoptosis-related proteins in the regenerating epidermis. We characterized immunohistochemically the expression of cell cycle regulators p63, CD29, PCNA, p53, pro- and antiapoptotic proteins bcl2, bax, caspase 3 and DNA breaks, as well as keratin 10, 16 and 17.

METHODS

Studies were carried out in 12 patients with diabetic foot, and 10 patients with varicose ulcers of the calf. Skin biopsy specimens were obtained from the border area of ulcers and the topographically corresponding sites of normal skin of patients undergoing orthopedic surgery. Biopsy specimens were stained by use of specific primary antibodies, a kit based on biotin-avidin-peroxidase complex technique, and DAB substrate. Results were expressed as a mean staining intensity.

RESULTS

At the edge of both types of ulcers, keratinocytes were p63+, CD29+, PCNA+ and p53-. The mean intensity of p63 and CD29 staining was slightly higher than in controls. The intensity of bcl2 staining was higher at the edge of diabetic ulcers compared with venous ulcers, whereas the intensity of bax staining was similar. The expression of caspase 3 was lower at the edge of venous ulcers and higher in diabetic ulcers and the intensity of TUNEL staining was lower at the edge of both types of ulcers compared with controls. Keratinocytes at the edge and distally to both types of ulcers expressed cytokeratin 16 and 17. There was no expression of cytokeratin 10 at the edge of ulcers. Together, there was a slight tendency for higher expression of cell cycle-related proteins in venous and of apoptosis-related proteins in diabetic ulcers epidermis; however, the differences were minor.

CONCLUSIONS

The impaired epithelialization of chronic leg ulcers is not caused by an inadequate epidermal stem cell proliferation, differentiation, or apoptosis. It may rather reflect the distorted organization of wound bed, caused by infection and impaired nutrition supply, altering keratinocyte migration. To accelerate healing of an ulcer, modeling of the granulation tissue by regulatory cytokines but not stimulation of keratinocyte growth seems to be indicated.