title: A Theoretical and Experimental Investigation of Mechanical Damage to Rodent Sperm Generated by Microscale Ice Formation.
abstract: BACKGROUND: Rodent sperm cryopreservation is of critical importance for the maintenance of lines or strains of genetically engineered mice and rats. However, rodent sperm are extremely mechanically sensitive due to their unusual morphology, and are severely damaged using current methods of cryopreservation. Those methods result in poor post thaw motility (PTM) for mouse.
  
  
  OBJECTIVE
  To investigate the mechanism of mechanical damage introduced to rodent sperm during freezing, a micro-mechanical model was established to analyze the sperm radial and axial thermal stresses generated by microscale extracellular ice formation.
  
  
  METHODS
  PTM of mouse sperm cryopreserved in capillaries of different radii (100, 200, 344, 526, 775µm) was measured using a standard computer-assisted sperm analysis system.
  
  
  RESULTS
  The model predicts that when one of the inner dimensions of the containers (the inner diameter of plastic straws or straw capillaries) is on the same order of magnitude of sperm length, axial stress is significantly increased. The experimental results showed that the value of PTM was decreased from 38 ± 8 % in the larger (775µm) capillaries to 0 ± 0 % in the smaller (100 µm) ones.
  
  
  CONCLUSIONS
  Theoretical analysis based on the established model were experimentally validated and can be used to guide the design of novel devices to improve the efficiency of rodent sperm cryopreservation.
authors.affiliation: Department of Mechanical and Aerospace Engineering; Comparative Medicine Center, University of Missouri, Columbia, MO, USA. hanx@missouri.edu.
authors.forename: X
authors.initials: X
authors.lastname: Han
authors.affiliation: Comparative Medicine Center, University of Missouri, Columbia, MO, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Critser
mesh_terms: D000818:Animals; D015925:Cryopreservation / Q000295:instrumentation / Q000379:methods*; D008297:Male; D051379:Mice; D051381:Rats; D012662:Semen Preservation / Q000379:methods*; D013314:Stress, Mechanical