Distribution and proportion of M1/M2 macrophages in periodontal tissues in rats with and without periodontitis

To investigate the distribution and proportion of M1/M2 macrophages in the periodontal tissues of rats with and without periodontitis.

Twelve Sprague-Dawley rats were randomly divided into a chronic periodontitis group (CP, n = 6) and a periodontal health group (PH, n = 6). The periodontitis model was induced at the first mandibular molar using a stainless steel ligature and was confirmed by histological analysis. M1 macrophages were labeled with inducible nitric oxide synthase (iNOS), and M2 macrophages were labeled with CD163. The distributions of M1 and M2 macrophages in the two groups were determined via immunohistochemistry and immunofluorescence, and the M1/M2 ratios were compared between the two groups.

The M1 type macrophage count in the PH group was 12.17 ± 1.40, and the M1 macrophage count in the CP group was 40.00 ± 3.20; there was a statistically significant difference between the two groups (t = 7.96, P < 0.0001). The M2 macrophage count in the PH group was 4.50 ± 1.09, and the M2 type macrophage count in the CP group was 5.33 ± 0.67. There was no statistically significant difference between the two groups (t = 0.65, P = 0.53). The M1/M2 ratio in the CP group was 3.72 ± 1.08, and the M1/M2 ratio in the PH group was 8.31 ± 1.37; there was a statistically significant difference between the two groups (t = 2.63, P =0.025).

During periodontitis, M1 macrophages increased significantly and were widely distributed; they may be involved in the progression of periodontitis and may be closely related to the destruction of the cementum.