ADAM10 regulates Notch function in intestinal stem cells of mice

BACKGROUND & AIMS

A disintegrin and metalloproteinase domain-containing protein 10 (ADAM10) is a cell surface sheddase that regulates physiologic processes, including Notch signaling. ADAM10 is expressed in all intestinal epithelial cell types, but the requirement for ADAM10 signaling in crypt homeostasis is not well defined.

METHODS

We analyzed intestinal tissues from mice with constitutive (Vil-Cre;Adam10(f/f) mice) and conditional (Vil-CreER;Adam10(f/f) and Leucine-rich repeat-containing GPCR5 [Lgr5]-CreER;Adam10(f/f) mice) deletion of ADAM10. We performed cell lineage-tracing experiments in mice that expressed a gain-of-function allele of Notch in the intestine (Rosa26(NICD)), or mice with intestine-specific disruption of Notch (Rosa26(DN-MAML)), to examine the effects of ADAM10 deletion on cell fate specification and intestinal stem cell maintenance.

RESULTS

Loss of ADAM10 from developing and adult intestine caused lethality associated with altered intestinal morphology, reduced progenitor cell proliferation, and increased secretory cell differentiation. ADAM10 deletion led to the replacement of intestinal cell progenitors with 2 distinct, post-mitotic, secretory cell lineages: intermediate-like (Paneth/goblet) and enteroendocrine cells. Based on analysis of Rosa26(NICD) and Rosa26(DN-MAML) mice, we determined that ADAM10 controls these cell fate decisions by regulating Notch signaling. Cell lineage-tracing experiments showed that ADAM10 is required for survival of Lgr5(+) crypt-based columnar cells. Our findings indicate that Notch-activated stem cells have a competitive advantage for occupation of the stem cell niche.

CONCLUSIONS

ADAM10 acts in a cell autonomous manner within the intestinal crypt compartment to regulate Notch signaling. This process is required for progenitor cell lineage specification and crypt-based columnar cell maintenance.

Intrathoracic anastomosis after oesophageal resection for cancer

Cervical anastomosis has been advocated to avoid the pulmonary complications and life-threatening anastomotic disruptions following intrathoracic oesophagogastric anastomosis. This is a retrospective review of 111 oesophageal resections followed by an intrathoracic anastomosis. These resections were performed between September 1993 and August 1994 within a residency training program. The left thoracoabdominal approach was used for distal tumours and the Ivor Lewis technique for more proximal tumours. Squamous cell carcinoma accounted for 72% patients (n = 80), adenocarcinoma for 25% (n = 28), and others for 2.7% patients (n = 3). Of the patients, 69% had pathologic Stage III tumours. Operative mortality rate was 1.8% (two patients). Perioperative complications occurred in 39 patients, including anastomotic leak in 10 patients and myocardial infarction in 2 patients. In the absence of a leak, there were no major pulmonary complications requiring intensive care or ventilatory support. Of those patients with anastomotic disruption, 80% were salvaged by early clinical diagnosis and appropriate treatment. We conclude that transthoracic oesophagectomy with an intrathoracic anastomosis is a safe procedure that can be performed with low mortality and acceptable morbidity.

Chemotherapy for carcinoma of the esophagus: a comparison of evidence from meta-analyses of randomized trials and of historical control studies

BACKGROUND

Chemotherapy (CT) has been used as an adjunct to local treatment (surgery or radiotherapy) in esophageal carcinoma. A meta-analysis of all published randomized clinical trials and historical control studies which have used cisplatinum-based combination CT was carried out to asses the effect of chemotherapy on survival for esophageal cancer.

MATERIALS AND METHODS

A computer-based literature search was performed for the period from January 1988 to March 1995 using the index terms "Esophageal neoplasms' and "Chemotherapy'. The frame of reference was further narrowed to include only cisplatinum-based combination chemotherapy. Twelve randomized clinical trials (RCT) and eight historical control (HC) studies were included in the meta-analysis.

RESULTS

In the overview of HC studies a highly significant reduction in odds of death with CT was observed (68% +/- 8% OR = 0.32, 95% CI 0.24-0.42). On the other hand, the overview of RCTs showed a relative reduction in odds of death for the CT group of 4.2% +/- 23.7% (OR = 0.96, 95% CI 0.75-1.22).

CONCLUSIONS

There was a gross overestimation of treatment effect in the studies using HC as compared to RCTs, despite the use of cisplatinum-based chemotherapy in both groups. The meta-analysis of RCTs reveal no significant survival benefit from cisplatinum-based adjuvant/neoadjuvant chemotherapy in esophageal cancer.

Osteosynthesis of mandibular fractures with N-butyl cyanoacrylate: a pilot study

Osteosynthesis with n-butyl cyanoacrylate was attempted in 10 cases. Maxillomandibular fixation was maintained for only 48-72 hours. No mobility of the fractured segments was found when tested by moderate manual force. Union took place uneventfully in all but one case. Cases were followed from one to six months with appropriate radiographs at regular intervals. Blood, urine, and serum analyses revealed no significant changes when compared pre- and postoperatively. Chromosomal study revealed no rise in the frequency of SCEs postoperatively.