Abstract
Background:
Cingulin (CGN) is a tight junction cytoplasmic plaque that regulates gene expression and signal transduction. CD34 is a stem cell that has the potential to achieve self-renewal, continuously producing functional cells to maintain the homeostasis of the epidermis.

Aim:
This study aimed to understand the distribution, expression, and composition of CGN and CD34 in the epidermal layer compartments of the skin of healthy stray dogs of various ages and to illustrate the relationships between CD34 and CGN.

Methods:
Twenty male and twenty female dogs were allocated into four groups. Group 1, aged between 6 months and 1 year. Group 2, dogs aged between 1 and 2 years; Group 3, dogs aged between 2 and 4 years; and Group 4, dogs aged between 4 and 6 years. Skin biopsy samples from healthy dogs were obtained from the face, back, and leg regions. Histomorphometric assessment, molecular analysis for detection and quantification, and immunohistochemistry to study CD34 and CGN expression were performed.

Results:
In male dogs, Groups 3 and 1 had the highest levels of apoptosis in the back region (p < 0.05) versus Groups 1 and 4 displayed peak apoptotic counts in the facial region, while the female group exhibited a significant peak in all regions. In Group 4, the mitotic count showed significant differences (p < 0.05) between all regions in both sexes. Peak epidermal thickness is considerably represented in all parts of the females in groups 2 and 4 (p < 0.05). Group 4 showed a significant increase in the back area of male dogs compared to other groups and regions (p < 0.05). The expression of both genes was negatively correlated in most male and female dogs within the same epidermal skin region. Regarding the immunostaining expression of CD34 stem cells and CGN, in groups one-three was highest in the leg, followed by the back and face. In both sexes, the aged group showed moderately less expression of CD34 and CGN in the leg than in the back and face.

Conclusion:
These findings propose a region-specific regenerative capacity, lowest in the facial skin, which could explain an increased risk for dermatitis on the face compared with other body locations.

Key words: Apoptotic body; CD34; Cingulin; Epidermis thickness; Stray dog.