Loss of Notch signaling in skeletal stem cells enhances bone formation with aging

Area of Science:

• Cell Biology
• Skeletal Biology
• Aging Research

Background:

• Skeletal stem and progenitor cells (SSPCs) are crucial for bone maintenance and repair.
• Aging leads to a decline in osteoblastogenesis and an increase in adipogenesis within SSPCs, compromising skeletal integrity.
• The molecular drivers of age-related SSPC dysfunction are not fully understood.

Purpose of the Study:

• To investigate the role of Notch signaling in age-related SSPC fate determination.
• To explore the therapeutic potential of modulating Notch signaling to counteract skeletal aging.

Main Methods:

• Single-cell RNA sequencing to identify molecular changes in aging SSPCs.
• In vivo genetic manipulation using conditional knockout mice to delete Nicastrin, a Notch pathway component, in SSPCs.
• Assessment of bone mass, bone marrow adiposity, and bone repair capacity.

Main Results:

• Elevated Notch signaling was observed in SSPCs during aging.
• Deletion of Nicastrin in SSPCs of middle-aged mice resulted in increased osteo-lineage gene expression and enhanced trabecular bone mass.
• Reduced bone marrow adiposity and improved bone repair were observed in mice with modulated Notch activity.
• The transcription factor Ebf3 was identified as a downstream mediator of Notch signaling in SSPCs, dysregulated with aging.

Conclusions:

• Notch signaling critically regulates SSPC cell fate decisions.
• Moderating Notch signaling effectively ameliorates the skeletal aging phenotype, promoting increased bone mass and repair.
• Targeting Notch signaling, potentially via Ebf3, represents a promising therapeutic avenue for rejuvenating the aged skeleton.