The aim of this study was to identify human colonic resident cells able to initiate an inflammatory response in postischemic injury. Postischemic colonic injury, a condition relevant to various clinical settings, involves an inflammatory cascade in intestinal tissues through the recruitment of circulating inflammatory cells. However, there is no information on the nature of resident cells of the different intestinal layers able to initiate a postischemic inflammatory response. It is however an important issue in the context of a pharmacological approach of the early phase of intestinal
ischemia. We reasoned that maintaining the different colonic layers as explant cultures in an oxygenated medium immediately after colonic resection, that is, after an ischemic period, would allow one to identify the resident cells able to initiate an inflammatory cascade, without interference of recruited inflammatory/immune cells. To this end, we designed an explant culture system that operationally defines three compartments in surgical specimens of the human colon, based on the microdissected layers, that is, mucosa, submucosa (containing muscularis mucosae) and muscularis propria. To validate the results obtained in explant cultures in the clinical setting of
ischemic colitis, eight cases of sigmoid
volvulus were examined. Only the myocytes-containing explants produced
tumor necrosis factor alpha (
TNFalpha), via an ADAM17 (a
disintegrin and
metalloproteinase-17)-dependent pathway, as shown by the abrogation of
TNFalpha production by the inhibitor
Tapi-2. Immunofluorescence studies identified nonvascular and vascular myocytes as resident cells coexpressing
TNFalpha and ADAM17, both in our postischemic explant system and in surgical specimens from
ischemic colitis patients. Finally, time-course experiments on explanted tissues showed that
TNFalpha production by myocytes was an early event triggered by a postischemic oxidative stress involving
nuclear factor kappa B (
NF-kappaB). In conclusion, this study identifies human intestinal myocytes as resident cells able to initiate an inflammatory reaction through
TNFalpha production in postischemic conditions, and delineates two points of control in
TNFalpha production,
NF-kappaB and ADAM17, which can be targeted by pharmacological manipulation.