Age-Dependent Differential Expression of Apoptotic Markers in Rat Oral Mucosa

Abstract

Objective: This study tests the hypothesis that gingival tissue produces age-dependent activation of apoptotic markers. Methods: To address the hypothesis, a prospective experimental study was conducted on 20 adult male albino rats, which were divided into two groups. Group 1 comprised rats aged six months (weighing 150–200 g), and group 2 included old rats aged one year (weighing 250–300 g). Gingival tissue and buccal mucosa biopsy samples were obtained from both groups. Histological and immunohistochemical (Bax apoptotic protein marker) sections were analyzed for both groups. Results: Our data showed a significant decrease in the proliferative activity of oral mucosa (gingiva and buccal mucosa) in old rats and an increase in the immunoreactivity of Bax apoptotic proteins related to increased susceptibility of cells to apoptosis. The mucosal structures (epithelium and lamina propria) were significantly different between the two groups. Furthermore, immunoreactivity for Bax was different between young and old rats. Conclusions: Aging is associated with changes that lead to progressive, irreversible deterioration of the functional capacities of several tissues and organs. Our study demonstrated the effect of age on the histological and apoptotic behavior of oral mucosa (gingiva and buccal mucosa) cells.

Keywords: Apoptosis; Bax; Bcl-2; gingival tissue.

Figure 1

Representative Micrograph (Hematoxylin and eosin [H&E] Staining, Magnification ×100) of Group I Rat Gingiva Showing the Keratinized Stratified Squamous Epithelium, Epithelial Ridges and Lamina Propria (A) as Well as the Basal Cell Layer (a), Suprabasal Cells (b), Prickle cells (c), Granular cells (d), and Keratin Layer (e) (H&E Staining, Magnification ×200) (B).

Figure 2

Representative Micrograph (Hematoxylin and eosin [H&E] Staining, Magnification × 100) of Group II Rat Gingiva Showing Irregular Branches of Epithelium Ridges, Cornified Thick Keratin, and Coarse Collagen Bundles (H&E staining, magnification ×100) (A) as Well as a Thick Keratin Layer, Thick Granular Layer, Increased amount of Keratohyaline Granules and Suprabasal Wide Cells with Vesicular Nuclei Papillary Layer of Lamina Propria (a) and Blood Vessels in the Reticular layer (b) (H&E Staining, Magnification ×200) (B).

Figure 3

Representative Micrograph (Hematoxylin and eosin [H&E] Staining, Magnification ×100) of Group II Gingiva Showing the Different Layers of Keratinized Stratified Epithelium, Epithelial Ridges (a) and Thick Keratin Layer (b), Lamina Propria(c) (A) as Well as the Keratin (a) and Different Epithelial Cell Layers (b, c, d) and Papillary Layer of the Lamina Propria (H&E Staining, Magnification ×200) (B).

Figure 4

Representative Micrograph (Hematoxylin and eosin [H&E] Staining, Magnification ×100) of Group II Rat Buccal Mucosa Showing Reduced Thickness of the Epithelium and Narrow Epithelial Ridges, Thin Lamina Propria and Dense Submucosa, (A) as Well as Shrunken Basal Cells (a), Faintly Stained Suprabasal Cells (b), Large Spinous Cells with Faint and Vesicular Nuclei (c), Diminished Granular Cell Layer (d), Thin Cornified Layer (c), Reduced Lamina Propria (f), and Wide Submucosa (g), with Irregular Arrangement of Fibrous Bundles and Muscle Fibers (H&E Staining Magnification ×200) (B).

Figure 5

Representative Micrograph of Gingiva of Rats Aged Six Months Showing Mild Immunoreactivity for Bax of the Basal and Parabasal Layers (a), Mild Reaction in Localized Areas of Spinous (b), Granular (c), and Cornified Layers (d) (A). Gingiva of rats aged one year showing marked increase in immunoreactivity for Bax in the basal and parabasal layers (a), mild reaction in localized areas of the spinous (b) and granular layers (c), as well as negative reaction of the cornified layer (d). The strong reactivity is associated with the nuclei in connective tissue cells (e) (B).

Figure 6

Buccal Mucosa of Rats Aged Six Months Showing Mild Cytosolic Reaction for Bax of Basal (a) and Parabasal Cell Layers (b), Mild Perinuclear Reaction of Few Basal Cells, Few Spinous Cells with Nuclear Reactivity (c), Mild to Moderate Reaction of the Cornified Layer (d), and Strong Perinuclear Reactivity in Few Cells of the Lamina Propria (e) (A). Buccal mucosa of rats aged one year showing increased Bax immunoreactivity in the basal and parabasal cell layers (a) and cornified layers (b) (B).