Differences in bone structure and unloading-induced bone loss between C57BL/6N and C57BL/6J mice.

Area of Science:

• Biomedical Research
• Animal Models
• Skeletal Biology

Background:

• The C57BL/6 mouse is a widely used model in biomedical research.
• Substrains like C57BL/6J (B6J) and C57BL/6N (B6N) have genomic variations.
• Phenotypic differences between B6J and B6N mice, particularly in bone, are not well-characterized.

Purpose of the Study:

• To investigate the bone phenotype of adolescent C57BL/6N mice.
• To compare the response of B6N and B6J mice to hindlimb unloading (HLU).
• To determine if B6N and B6J substrains are interchangeable for research.

Main Methods:

• Comparison of bone morphology and cellular activity in normally ambulating 9- and 11-week-old B6N and B6J mice.
• Assessment of bone response to HLU in 11-week-old mice.
• Analysis of trabecular and cortical bone parameters.

Main Results:

• At 9 weeks, B6N mice showed lower trabecular bone volume but higher bone formation rates than B6J mice.
• Cortical bone was largely similar, but unloaded B6N mice had smaller cortices than B6J mice.
• B6N mice exhibited greater deterioration in trabecular and endocortical variables under HLU compared to B6J mice.

Conclusions:

• Significant developmental differences exist in bone formation and morphology between B6N and B6J mice.
• These substrains display differential responses to mechanical unloading, potentially influenced by specific genes.
• B6N and B6J mice should not be considered interchangeable for research requiring consistent phenotypic responses.