Characterizing the Biomechanical and Biochemical Properties of Mouse Uterine Tissue

For a successful pregnancy, the uterus and the cervix work together as a biomechanical structure to protect the fetus until term. During gestation, typically 37 weeks, the uterus undergoes a growth transformation to accommodate the growing fetus and to prepare for labor. This uterine growth is characterized by an increase of its wet weight, elastin content, and collagen content. Then at parturition, the uterus must contract while the cervix ripens and dilates to allow the passage of the fetus. The transformation mentioned above is believed to be responsible for the contractions, and any deviations from the expected biochemical transformation put both the mother and baby in danger. The goals of this study are to quantify and compare the biochemical and biomechanical properties of uterine tissue from normal and abnormal mouse models of pregnancy. This study utilizes Anthrax toxin receptor 2 knock-out mice (Antxr2 -/-), which exhibit an accumulation of collagen in the cervix and uterus as a result of a defect in the maintenance of their extracellular matrix (ECM). Uterine tissues from nonpregnant Antxr2 -/- and non-pregnant wild type mice (Antxr2 +/+) were tested. Tissue samples were tested for collagen content, collagen crosslink strength (i.e. collagen extractability) and were subjected to tensile mechanical testing. Results from the biochemical assays revealed that the Antxr2 -/- uterine samples had significantly higher levels of collagen. It was also revealed that collagen extractability was region-dependent. Lastly, mechanical testing proved that Antxr2 -/- uterine tissue is mechanically stronger than Antxr2 +/+ (peak stress 0.078 MPa and 0.04 MPa). This study presents one of the first attempts to correlate the biochemical makeup of the uterus to its biomechanical properties.