Adynamic Bone Decreases Bone Toughness During Aging by Affecting Mineral and Matrix

Area of Science:

• Bone biology
• Gerontology
• Nephrology

Background:

• Adynamic bone is the most frequent bone lesion in chronic kidney disease (CKD) patients.
• Long-term antiresorptive therapy can also induce adynamic bone.
• Adynamic bone is characterized by low bone turnover, leading to diminished bone quality and increased fracture risk.

Purpose of the Study:

• To investigate age-related changes in bone quality in a mouse model of adynamic bone.
• To evaluate how adynamic bone affects bone structure, material properties, and mechanical function across different ages.

Main Methods:

• Utilized a mouse model (Col2.3Δtk mice treated with ganciclovir and pamidronate) to induce adynamic bone.
• Assessed bone quality using histomorphometry, microcomputed tomography, backscattered electron imaging, and biomechanical testing.
• Examined mineral and matrix properties via X-ray diffraction and Raman spectroscopy.

Main Results:

• Aging controls showed natural bone loss and deterioration in trabecular structure.
• Adynamic bone mice exhibited severely blunted bone turnover, preserving trabecular bone mass with aging.
• Despite preserved bone mass, old adynamic mice showed decreased mechanical properties, including reduced cortical bone toughness, linked to collagen maturation and crystal growth.

Conclusions:

• Preservation of bone mass in adynamic bone does not prevent age-related decline in mechanical properties.
• Material-level changes, including collagen and crystal properties, contribute to reduced bone toughness in adynamic bone.
• This mouse model is valuable for studying fractures in elderly patients with low bone turnover due to metabolic bone disease or antiresorptive therapy.