Annals of Biomedical Engineering

, Volume 33, Issue 8, pp 1078–1089

Quantification of Bladder Smooth Muscle Orientation in Normal and Spinal Cord Injured Rats

Authors

  • Jiro Nagatomi
    • Department of BioengineeringUniversity of Pittsburgh
  • K. Khashayar Toosi
    • Department of BioengineeringUniversity of Pittsburgh
    • Department of UrologyUniversity of Pittsburgh
  • Jonathan S. Grashow
    • Department of BioengineeringUniversity of Pittsburgh
  • Michael B. Chancellor
    • Department of UrologyUniversity of Pittsburgh
    • McGowan Institute for Regenerative MedicineUniversity of Pittsburgh
    • Department of BioengineeringUniversity of Pittsburgh
    • McGowan Institute for Regenerative MedicineUniversity of Pittsburgh
Article

DOI: 10.1007/s10439-005-5776-x

Cite this article as:
Nagatomi, J., Toosi, K.K., Grashow, J.S. et al. Ann Biomed Eng (2005) 33: 1078. doi:10.1007/s10439-005-5776-x

Abstract

Spinal cord injuries (SCI) often lead to severe bladder dysfunctions. Our previous studies have demonstrated that following SCI, rat bladder wall tissue became hypertrophied, significantly more compliant, and changed its mechanical behavior from orthotropic to isotropic. In order to elucidate the link between the tissue microstructure and mechanical properties of the wall, we have developed a novel semi-automated image analysis method to quantify smooth muscle bundle orientation and mass fraction in the bladder wall tissues from normal and 10 day-post-SCI rats. Results of the present study revealed that there were significant (p < 0.05) increases in smooth muscle area fractions as well as significantly (p < 0.001) fewer cell nuclei per muscle area in the SCI groups compared to the normal groups. Furthermore, while the normal rat bladders exhibited predominant smooth muscle orientation only in the longitudinal direction, the SCI rat bladders exhibited smooth muscles oriented in both the circumferential and longitudinal directions. These results provide first evidence that bladder smooth muscle cells exhibit hypertrophy rather than hyperplasia and developed a second, orthogonal orientation of smooth muscle bundles following SCI. The results of the present study corroborate our previous mechanical anisotropy data and provide the basis for development of structure-based constitutive models for urinary bladder wall tissue.

Keywords

Histomorphometery Image analysis Mechanical anisotropy Smooth muscle

Copyright information

© Biomedical Engineering Society 2005