Tissue’s Response to Mechanical Stimuli By: Christopher Gambino Mentors: Engin Ozcivici,Shiyun Xu, Engin Ozcivici,Shiyun Xu, Russell Garman, Dr. Stefan Judex

Introduction  Tissue loss is an increasing problem in today’s society.  It will effect almost everyone from astronauts in space to sick and injured people that require bed rest.  Many methods to prevent this loss have been tried from exercise to medication.  During this research it was noticed that some strains of mice lose tissue faster than others.

Methods  Resistant and susceptible strains of mice were crossbred to create an inbred F2 population.  These mice were then scanned at the age of 17 weeks.  They then had their hind-limbs immobilized to simulate spaceflight or bed rest.  After 3 weeks of this they are scanned again for a second time.  The hind-limbs were then re-mobilized and the mice were allowed to use them for an additional 3 weeks before being scanned 3 rd and final time.

Results  During the 1-3 week period bone volume decreased an average of 1%.  During the 3-6 week period bone volume increased an average of 4%  During weeks 1-3 the muscle volume decreased and average of 10%  During Weeks 4-6 muscle mass volume increased 7%

Discussion  The bone seemed to be more responsive to mechanical loading (walking) than unloading (immobilized).  The reverse of this is true for the muscle.  The distribution of loss/gain rather than being grouped around one value suggests that there is a controlling factor that was spread through the genetically heterogeneous population.

Future Research  Data on different sections of bone is needed and is currently being worked on.  Further research into the genetics of the individual mouse is needed to isolate any controlling factor.