Regeneration Of Intestinal Mucosa Research Articles

Stat3 is indispensable for damage-induced crypt regeneration but not for Wnt-driven intestinal tumorigenesis.

Signal transducer and activator of transcription 3 (Stat3) has been shown to play a role in intestinal regeneration and colitis-associated colon carcinogenesis. However, the role of Stat3 in the Wnt-driven sporadic intestinal tumorigenesis remains poorly understood. We examined the roles of Stat3 in intestinal regeneration and tumorigenesis by organoid culture experiments using Stat3∆IEC mouse–derived intestinal epithelial cells in which Stat3 was disrupted. The regeneration of intestinal mucosa and organoid formation were significantly suppressed by Stat3 disruption, which was compensated by Wnt activation. Furthermore, once organoids were recovered, Stat3 was no longer required for organoid growth. These results indicate that Stat3 and Wnt signaling cooperatively protect epithelial cells at the early phase of intestinal regeneration. In contrast, intestinal tumorigenesis was not suppressed by Stat3 disruption in adenomatous polyposis coli (Apc)Δ716 and Apc∆716 Tgfbr2∆IEC mice, thus indicating that Stat3 is not required for Wnt activation–driven intestinal tumorigenesis. Mechanistically, Itga5 and Itga6 were down-regulated by Stat3 disruption, and focal adhesion kinase (FAK) activation was also suppressed. Notably, FAK inhibitor suppressed the organoid formation of wild-type epithelial cells. These results indicate that Stat3 is indispensable for the survival of epithelial cells through the activation of integrin signaling and the downstream FAK pathway; however, it is not required for the Wnt signaling-activated normal or tumor epithelial cells.—Oshima, H., Kok, S.-Y., Nakayama, M., Murakami, K., Voon, D. C.-C., Kimura, T., Oshima, M. Stat3 is indispensable for damage-induced crypt regeneration but not for Wnt-driven intestinal tumorigenesis.

Enhanced therapeutic effect of LK-423 in treating experimentally induced colitis in rats when administered in colon delivery microcapsules

LK-423 is a phthalimido-desmuramyl-dipeptide derivative with immunomodulating activity. In the present study the therapeutic efficacy of a colon-specific drug delivery system–LK-423 microcapsules–was examined in the 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced ulcerative colitis model in rats. The colon-specific delivery of the drug using microcapsules relies on the combination of pH (outer gastroresistant coating), time (inner retard coating of Eudragit® RS and RL) and enzyme (pectin core) controlled drug release mechanisms. The optimal in vitro dissolution profile for LK-423 delivery to the colon of rats was obtained after coating newly developed LK-423 loaded pectin cores with 20% w/w of retard coating with a Eudragit® RS/RL ratio of 8.5/1.5 and 30% w/w of enteric coating. Orally administered LK-423 microcapsules were therapeutically more beneficial in treating TNBS-induced ulcerative colitis in rats than orally or rectally administered LK-423 in the form of suspension. Clinical activity scores and colon weight to length ratio were insignificantly lower and the macroscopically estimated degree of healing was significantly greater. On the histological level, the administration of LK-423 microcapsules resulted in most physiological regeneration of intestinal mucosa, indicated by regular architecture of all mucosal tissue components, what is probably related to local drug delivery near the site of inflammation achieved using microcapsules. These results demonstrate that LK-23 colon delivery microcapsules enhance the therapeutic efficacy of the drug and therefore appear to be a useful approach for treating various inflammatory diseases in the large intestine.

Reduced survival of rectal cancer patients with increased tumor epidermal growth factor receptor levels.

The epidermal growth factor receptor and its various ligands (epidermal growth factor, transforming growth factor-alpha, amphiregulin, heparin-binding epidermal growth factor, heregulin, and betacellulin) have been implicated in growth and regeneration of intestinal mucosa and might be related to the development and progression of gastrointestinal tumors. Although some studies have investigated levels of epidermal growth factor receptor by radioligand binding studies, none of them have further analyzed these levels in patients with rectal cancer and investigated their prognostic value. We quantitatively determined tumor epidermal growth factor receptor levels in 38 patients with colorectal cancer compared with adjacent normal mucosa by iodine-125-labeled epidermal growth factor binding studies and Scatchard analysis. Patients were followed up for 49.5 +/- 32.2 (range, 2-120) months. Epidermal growth factor receptor capacity was increased in invasive colorectal carcinomas according to T classification (P < 0.001), tumors with lymph node infiltration (P = 0.038), and advanced International Union Against Cancer stage (P < 0.001). Survival of colorectal cancer was reduced in patients with advanced International Union Against Cancer stage (P < 0.001), tumors with positive lymph nodes (P < 0.001), and tumors with elevated epidermal growth factor receptor levels (P = 0.024). In rectal cancer patients, poor prognosis was associated with advanced International Union Against Cancer stage (P = 0.029), tumors with lymph node infiltration (P = 0.040), and increased epidermal growth factor receptor levels (P = 0.002). Multivariate Cox regression analysis indicated that elevated levels of epidermal growth factor receptor were an independent predictor of reduced survival in patients with rectal cancer (P = 0.005). The epidermal growth factor receptor/ligand system appears to be involved in tumor development and tumor progression of colorectal carcinomas, with prognostic implication especially in patients with invasive rectal carcinomas. These patients might take advantage of therapies that specifically block epidermal growth factor receptor-mediated signal transduction.

Death from early colorectal cancer is predicted by the presence of transcripts of the REG gene family.

An intrinsic component of colorectal carcinogenesis may be the capacity to activate regenerative responses simultaneously with inhibition of apoptosis. Since apoptosis is known to be inhibited in colorectal cancer, this study sought evidence for the activation of the REG family of genes which are considered to be activated during regeneration of intestinal mucosa. Transcripts for the REG gene were found in 53% of colorectal cancers and for the PAP gene in 60% of colorectal cancers, by RT-PCR. Using in situ hybridization, the REG transcripts were found to be present in the tumour cells themselves rather than inflammatory or stromal cells. There were no significant correlations between the expression of these two genes and tumour stage, age or sex of the patient population or tumour site. However, in patients with non-metastatic disease who underwent ostensibly curative surgery, the expression of REG alone and co-expression of REG with PAP had a highly significantly adverse effect on survival. These data provide support for the concept that, in some tumours, carcinogenesis involves a regenerative process which co-exists with apoptotic inhibition and may provide a valuable selective indicator of the need for adjuvant therapy in those patients with early-stage colorectal cancer whose disease is destined to recur after curative surgery. © 2000 Cancer Research Campaign

Upregulation of HGF activator inhibitor type 1 but not type 2 along with regeneration of intestinal mucosa.

Hepatocyte growth factor (HGF) activator inhibitor type 1 (HAI-1) and type 2 (HAI-2) are new Kunitz-type serine protease inhibitors that were recently purified and cloned from the human stomach cancer cell line MKN45 as specific inhibitors against HGF activator. Both proteins contain two Kunitz inhibitor domains and are expressed abundantly throughout the gastrointestinal tract, in addition to the placenta, pancreas, and kidney. In this study, to assess the possible roles of HAI-1 and HAI-2 in the intestinal mucosa, we examined the expression of HAI-1 and HAI-2 during regeneration of the intestinal mucosa. Immunohistochemical studies revealed that HAI-1 but not HAI-2 was detected more strongly in regenerative epithelium than in normal epithelium, although both proteins were detected throughout the human gastrointestinal tract. During the course of acetic acid-induced experimental colitis in an in vivo mouse model, HAI-1 but not HAI-2 was upregulated in the recovery phase, suggesting that HAI-1 but not HAI-2 is associated with the regeneration of damaged colonic mucosa. Upregulation of HAI-1 may serve to downregulate the proliferative response after initial activation of MET receptor by HGF/scatter factor after an injury.

Regeneration of intestinal mucosa after irradiation.

Radiobiological techniques may be used for determining the size of a population of cells capable of indefinite proliferation (clonogenic cells). In normal “steady-state” proliferative tissues, such as intestinal mucosa, clonogenic cell numbers remain constant through the continuous loss of cells. In order for a depleted clonogenic population to regrow to normal, cell loss must be reduced temporarily. The time-sequence for the switching off and on of cell loss from the intestinal mucosa is reported here and could form a temporal framework for more detailed studies of the mechanisms that control cell loss, and therefore growth.