Ratio of Periurethral Tissue Collagen Type III/Type I Content in Intact and Spayed Female Dogs
Collagen types I (CI) and III (CIII) are responsible for tensile strength of tissue. It has been postulated in humans that a change in the ratio of CIII/CI in periurethral tissues may play a role in the development of stress urinary incontinence in post-menopausal women; however it is not known whether the observed changes are more strongly influenced by age or hormonal status. Evaluation of the CIII/CI ratio in intact and spayed female dogs may help to answer this question and further describe those factors involved in canine urethral sphincter incompetence.
Frozen sections of periurethral tissues from 14 intact and 6 spayed female dogs were evaluated. All dogs were > 15 kg and between 1 and 7 years old. One of the spayed females had urinary incontinence. Immunofluorescence was performed using anti-collagen I-FITC and anti-collagen III-Texas Red conjugated monoclonal antibodies. 3-6 regions of tissue sections from each dog were imaged using a Leica TCS SP2 confocal microscope. Images were converted to binary and analyzed using Image J software (v1.37, NIH, USA) for pixel total area and area fraction. The CIII/CI ratio was calculated for each image and averaged within each dog. Comparisons were made between intact and spayed female dogs with a Welch's t test for unequal variances with and without the incontinent female included. No significant difference in CIII/CI total area or area fraction was found based on reproductive status. The incontinent dog was an outlier with a higher total area and area fraction CIII/CI ratio than all continent dogs. These results suggest that estrogen may not significantly influence the periurethral CIII/CI ratio in female dogs. Collagen content in urinary incontinent female dogs should be further evaluated to determine if incontinence is related to a higher CIII/CI ratio.