Negative feedback between PTH1R and IGF1 through the Hedgehog pathway in mediating craniofacial bone remodeling

Area of Science:

• Craniofacial biology
• Bone biology
• Molecular genetics

Background:

• Orofacial bone defect regeneration is a significant clinical challenge.
• Parathyroid hormone 1 receptor (PTH1R) signaling is crucial for bone remodeling.
• Regulatory mechanisms of PTH1R in oral bone, especially during inflammation, lack direct genetic evidence.

Purpose of the Study:

• To investigate the role of PTH1R signaling in Gli1+ progenitors within the orofacial bone.
• To elucidate the regulatory mechanisms of PTH1R in oral bone homeostasis and inflammation.
• To identify molecular players involved in PTH1R-mediated orofacial bone remodeling.

Main Methods:

• Genetic manipulation: Deletion of PTH1R in Gli1+ progenitors.
• Molecular analyses: Single-cell and bulk RNA-Seq.
• In vivo studies: Investigating bone remodeling phenotypes and gene interactions.
• Dual gene deletion: Assessing combined effects of IGF1 and PTH1R deficiency.

Main Results:

• PTH1R deletion in Gli1+ progenitors resulted in heightened osteogenesis and osteoclastogenesis.
• PTH1R was found to suppress the osteogenic potential of Gli1+ progenitors during inflammatory conditions.
• Upregulated Insulin-like Growth Factor 1 (IGF1) expression was observed upon PTH1R deletion.
• Dual deletion of IGF1 and PTH1R partially rescued the bone remodeling abnormalities.
• An inverse relationship between PTH1R and Hedgehog signaling was identified, linked to IGF1 upregulation.

Conclusions:

• A negative feedback mechanism exists between PTH1R and IGF1 in craniofacial bone turnover.
• PTH1R signaling negatively regulates the osteogenic capacity of Gli1+ progenitors during inflammation.
• These findings provide novel insights into the molecular mechanisms governing orofacial bone remodeling.