CD47 is Required for Mesenchymal Progenitor Proliferation and Fracture Repair

Area of Science:

• Biomedical Science
• Regenerative Medicine
• Orthopedics

Background:

• CD47 is a cell-surface receptor involved in tissue repair.
• Its role in bone fracture healing remains uninvestigated.
• Disrupting CD47 generally enhances injury repair across various tissues.

Approach:

• Utilized a murine closed-fracture model to study CD47's role in bone healing.
• Assessed fracture callus characteristics using microcomputed tomography and histology.
• Investigated cellular mechanisms by analyzing mesenchymal progenitor cells (MSCs) and endothelial cells in vitro and in vivo.
• Employed a CD47 morpholino in wild-type (WT) mice to confirm findings.

Key Points:

• CD47-null mice exhibited reduced callus bone volume, mineral content, and increased fibrous tissue post-fracture.
• CD47-null MSCs showed diminished colony formation and proliferation, with no change in osteoblast differentiation.
• CD47-null endothelial cells displayed increased proliferation and blood vessel density in vivo.
• CD47 inhibition via morpholino replicated the impaired healing phenotype.

Conclusions:

• CD47 inhibition impairs both non-ischemic and ischemic fracture healing.
• This impairment is partly due to reduced mesenchymal progenitor cell proliferation.
• Enhanced endothelial cell proliferation and vascularization do not compensate for MSC dysfunction in CD47-disrupted bone healing.