Traumatic
spinal cord injury (SCI) permanently alters bladder function in humans.
Hematuria and
cystitis occur in both human SCI as well as in rodent models of SCI. Others have reported early SCI-dependent disruption to bladder uroepithelial integrity that results in increased permeability to urine and urine-borne substances. This can result in
cystitis, or
inflammation of the bladder, an ongoing pathological condition present throughout the chronic phase of SCI in humans. The goals of our study were twofold: (1) to begin to examine the inflammatory and molecular changes that occur within the bladder uroepithelium using a clinically-relevant spinal
contusion model of injury, and (2) to assess whether these alterations continue into the chronic phase of SCI. Rats received either moderate SCI or
sham surgery. Urine was collected from SCI and
sham subjects over 7 days or at 7 months to assess levels of excreted
proteins.
Inflammation in the bladder wall was assessed via biochemical and immunohistochemical methods. Bladder
tight junction proteins, mediators of uroepithelial integrity, were also measured in both the acute and chronic phases of SCI. Urine
protein and
hemoglobin levels rapidly increase following SCI. An SCI-dependent elevation in numbers of neutrophils within the bladder wall peaked at 48 h. Bladder
tight junction proteins demonstrate a rapid but transient decrease as early
as 2 h post-SCI. Surprisingly, elevated levels of urine
proteins and significant deficits in bladder
tight junction proteins could be detected in chronic SCI, suggesting that early pathological changes to the bladder may continue throughout the chronic phase of injury.