Effect of type 2 diabetes mellitus on mandibular bone regeneration and the expression of T helper cell 17/regulat-ory T cell-related factors in mice.

Objectives: To observe the effect of type 2 diabetes mellitus (T2DM) on mandibular bone regeneration and the expression of factors related to T helper cell 17 (Th17 cell) and regulatory T cell (Treg cell) in mice.

Methods: Thirty-six 6-week-old C57BL/6J male mice were randomly divided into normal control (NC) and T2DM groups. Fasting blood glucose levels were detected 0 d, 7 d, 14 d, and 28 d after surgery for mandibular defects. Hematoxylin-eosin (HE) staining was used in observing the bone after 7 d, 14 d, and 28 d of the healing process. Immunohistochemical staining was used in observing the expression of alkaline phosphatase (ALP), Runt-related transcription factor 2 (RUNX2), forkhead box protein P3 (Foxp3), retinoic acid related orphan receptor gamma T (RORγt), and protein tyrosine phosphatase non-receptor type 2 (PTPN2) after 7 d, 14 d, and 28 d of healing.

Results: HE staining showed that the area with new bones in the T2DM group was significantly smaller than that in the NC group. Immunohistochemical staining showed that the expression of osteogenesis related proteins ALP and RUNX2 were significantly reduced in the T2DM group. In addition, the number of RORγt positive cells increased, whereas the number of Foxp3 positive cells and the expression PTPN2 decreased significantly in the mandibular bone defect in mice with T2DM.

Conclusions: T2DM significantly inhibit mandibular bone regeneration in mice. Decline in PTPN2 expression and the transition of Treg and Th17 may be the underlying molecular mechanisms.