Morphology of Mouse Anterior Cruciate Ligament-Complex Changes Following Resistance Running Through Adolescence

There is little known about how the anterior cruciate ligament (ACL) develops throughout growth and responds to an increase in mechanical forces placed upon it over time. To improve our understanding, 8-week old female A/J and C57BL/6J inbred mice were voluntary run through pubescence on a standard cage wheel with increased resistance. After 4-weeks of running, various morphological, histological, and mechanical analyses were performed to compare the ACL, the entheses (i.e., insertion sites) and surrounding bony knee architecture of the runners to that of normal cage-activity mice. My contribution to this research was on the histological analyses, particularly in quantifying muscle fiber size differences between the quadriceps, hamstrings and gastrocnemius mm. of runners and non-runners. Preliminary findings suggest that after accounting for mouse body weight there is no significant difference in muscle fiber size between runners and non-runners. However, there is a significant difference in whole muscle weight (grams) for all muscle bodies between runners and non-runners. This discrepancy may reflect differences in body composition between mouse strains and treatment groups, that reflect a muscle mass difference but not necessarily a strength difference.

Supervisor: Stephen Schlecht
Department: Orthopedic Surgery