Zahra Chinipardaz
| Zahra Chinipardaz |
Chinipardaz, Zahra1, Graves, Dana2, Yang, Shuying3
1University of Pennsylvania School of Dental Medicine, Department of Basic and Translational Sciences; Department of Periodontics
2University of Pennsylvania School of Dental Medicine, Department of Periodontics
3University of Pennsylvania School of Dental Medicine, Department of Basic and Translational Sciences
FOXO1 upregulation is linked to diabetes defective fracture healing. We previously showed that diabetes disrupts ciliogenesis and subsequently impairs fracture healing. Here, we tested whether diabetes-enhanced FOXO1 expression causes disruption of ciliogenesis resulting in impaired fracture healing.
MethodsClosed femur fracture was induced in mice with FOXO1 deletion in osteoblasts (OSXcretTAFOXO1f/f) and OSXcretTA mice as control. Diabetic model was induced by multiple streptozotocin injections while normoglycemic group received vehicle alone. Fracture callus were harvested on D21 to assess osteoblasts’ ciliogenesis by immunostaining and bone formation using MicroCT and histological analysis. In-vitro studies explored the effect of FOXO1 deletion on ciliogenesis and osteogenesis of primary osteoblasts (POBs) exposed to advanced glycation end products (AGEs) or BSA (as control). Statistically significant was determined by ANOVA at P<0.05.
ResultsNormoglycemic OSXcretTAFOXO1f/f and diabetic OSXcretTA mice exhibited significant reduction in bone formation compared to control mice (P<0.05), which was reversed in diabetic OSXcretTAFOXO1f/f mice showing no significant difference compared to control mice (P<0.05). Consistently, the expression of bone markers was dramatically downregulated in normoglycemic OSXcretTAFOXO1f/f and diabetic OSXcretTA mice, but significantly restored in diabetic mice with FOXO1 deletion. Only 14% of osteoblasts had cilia in the diabetic mice which was significantly increased in diabetic FOXO1 knockout mice to 45% (P<0.05). In-vitro, mineralization and the expression level of osteogenic markers were reduced in POBs with FOXO1 deletion and POBs exposed to AGEs compared to control and it was reversed to 85% in POBs exposed to AGEs upon FOXO1 deletion compared to control (P>0.05). Cilia formation was dramatically reduced in AGEs group compared to control (32% vs 72%) (P<0.05), which was rescued to 70% by FOXO1 ablation in AGEs treated POBs.
ConclusionDiabetes-enhanced FOXO1 reduced ciliogenesis in osteoblasts resulting in defective fracture healing. Ablation of FOXO1 rescued diabetes impaired fracture healing through restoring ciliogenesis.