Are interstitial cells of Cajal involved in mechanical stress-induced gene expression and impairment of smooth muscle contractility in bowel obstruction?

BACKGROUND AND

aimsThe network of interstitial cells of Cajal (ICC) is altered in obstructive bowel disorders (OBD). However, whether alteration in ICC network is a cause or consequence of OBD remains unknown. This study tested the hypothesis that mechanical dilation in obstruction disrupts the ICC network and that ICC do not mediate mechanotranscription of COX-2 and impairment of smooth muscle contractility in obstruction.

methodsMedical-grade silicon bands were wrapped around the distal colon to induce partial obstruction in wild-type and ICC deficient (W/W(v)) mice.

resultsIn wild-type mice, colon obstruction led to time-dependent alterations of the ICC network in the proximal colon segment. Although unaffected on days 1 and 3, the ICC density decreased markedly and the network was disrupted on day 7 of obstruction. COX-2 expression increased, and circular muscle contractility decreased significantly in the segment proximal to obstruction. In W/W(v) control mice, COX-2 mRNA level was 4.0 (±1.1)-fold higher (n=4) and circular muscle contractility was lower than in wild-type control mice. Obstruction further increased COX-2 mRNA level in W/W(v) mice to 7.2 (±1.0)-fold vs. W/W(v) controls [28.8 (±4.1)-fold vs. wild-type controls] on day 3. Obstruction further suppressed smooth muscle contractility in W/W(v) mice. However, daily administration of COX-2 inhibitor NS-398 significantly improved muscle contractility in both W/W(v) sham and obstruction mice.

conclusionsLumen dilation disrupts the ICC network. ICC deficiency has limited effect on stretch-induced expression of COX-2 and suppression of smooth muscle contractility in obstruction. Rather, stretch-induced COX-2 plays a critical role in motility dysfunction in partial colon obstruction.