Murine Progeria Model Exhibits Delayed Fracture Healing with Dysregulated Local Immune Response

Area of Science:

• Biomedical Research
• Animal Models
• Skeletal Biology

Background:

• Bone fractures are globally prevalent, with delayed healing affecting up to 15% of cases.
• Current small animal models inadequately recapitulate clinical aspects of delayed fracture healing.
• The Zmpste24 knockout (Z24-/-) mouse, a model for Hutchinson-Gilford progeria syndrome, exhibits genomic instability and fragility, suggesting potential for delayed healing.

Purpose of the Study:

• To investigate if the Zmpste24 knockout (Z24-/-) mouse model displays delayed fracture healing.
• To evaluate the Z24-/- mouse as a preclinical model for studying fracture repair.
• To identify underlying mechanisms contributing to delayed healing in this model.

Main Methods:

• Intramedullary tibia fractures were surgically induced in Z24-/- and wild-type (WT) mice.
• Fracture healing was assessed over time using histomorphometry, micro-computed tomography (μCT), and mechanical testing.
• Tissue microenvironments (fracture callus, bone marrow, lymph nodes, blood) were analyzed for cellular senescence, immune cell populations, and cytokine profiles.

Main Results:

• Z24-/- mice showed significantly delayed fracture healing with smaller calluses, reduced bone content, and increased cartilage proportion compared to WT mice.
• Elevated cellular senescence and pro-inflammatory cytokines were observed in Z24-/- mice pre- and post-fracture.
• Z24-/- mice exhibited immune dysregulation, including altered lymphopoiesis/myelopoiesis and aberrant T cell and myeloid cell activation.

Conclusions:

• The Z24-/- progeria mouse model demonstrates delayed fracture healing characterized by impaired bone formation, increased senescence, and immune dysregulation.
• This model recapitulates key features of delayed healing, offering a valuable tool for preclinical therapeutic screening.
• The findings support the utility of the Z24-/- mouse for developing novel treatments for aberrant fracture healing.