Time-course Changes in the Mechanical Properties of the Rat Urinary Bladder following Spinal Cord Injury

INTRODUCTION The urinary bladder is a smooth muscle organ whose main functions are to store urine and to void when necessary. Since the most important aspect of the storage function of the bladder is to maintain low intravesical pressure in order to protect the upper urinary tract from backflow of urine, the compliance of the bladder wall is one of the key functional parameters to assess the health of this organ. Previously, using planar biaxial testing, we demonstrated that the mechanical compliance of bladder wall tissue in spinal cord injury (SCI) rats at 10 days post-injury was significantly greater compared to that of normal bladders under biaxial stretch [1]. These results contrasted typical, non-compliant bladder conditions found in chronic SCI patients [2]. In order to determine longterm alterations in the urinary bladder mechanical behavior due to SCI, the present study examined the biaxial mechanical properties of bladder wall tissues at various time points postSCI. In addition, biochemical assays were used to quantify collagen and elastin contents of SCI bladders to correlate with tissue-level findings of biomechanical properties.