A randomized double-blinded sham-controlled cross-over trial of tined-lead sacral nerve stimulation testing for chronic constipation.

OBJECTIVES: Sacral nerve stimulation (SNS) may provide long-term symptom relief to patients suffering from chronic constipation. Patients are currently selected for SNS using a 2-week peripheral nerve evaluation (PNE) comprising stimulation by temporary leads. However, only 40% of test responders receive long-term benefit from treatment meaning that healthcare costs per successfully treated patient are too high. The primary objective was to assess tined-lead testing to predict benefit from SNS for chronic constipation. PATIENTS AND METHODS: A randomized double-blind sham-controlled cross-over design evaluated enhanced PNE (ePNE) using tined quadripolar electrode leads over 6 weeks. The design differentiated between patients with discriminate and indiscriminate responses to testing. A score improvement of 25% or more was considered to be a positive response within a stimulation period. The primary outcome was the proportion of patients showing a reduction of at least 0.5 in constipation symptom score at 6 months. RESULTS: A total of 45 patients were randomized, of whom 29 (64.4%) were test-phase responders. Of these, 27 were implanted providing permanent SNS. During ePNE, seven (18%) were discriminate responders, 22 (56%) were indiscriminate responders and 10 (26%) were nonresponders. Six patients were withdrawn during the test phase because of infection or noncompliance. At 6 months, there was no significant difference in primary outcome between discriminate and indiscriminate responders (60 vs. 57%, P=0.76). The study was terminated prematurely because of a persistent infection rate of 10 (22%) during ePNE of which nine (20%) were severe. CONCLUSION: ePNE is a poor predictor of treatment response at 6 months. This suggests a strong and persistent placebo response during both SNS PNE and treatment. An extended 6-week PNE poses a high risk of infection.

Defects in multiple complexes of the respiratory chain are present in ageing human colonic crypts.

Mitochondrial DNA (mtDNA) mutations accumulate in a number of ageing tissues and are proposed to play a role in the ageing process. We have previously shown that colonic crypt stem cells accumulate somatic mtDNA point mutations during ageing. These mtDNA mutations result in the loss of the activity of complex IV (cytochrome c oxidase (COX)) of the respiratory chain in the stem cells and their progeny, producing colonic crypts which are entirely COX deficient. However it is not known whether the other complexes of the respiratory chain are similarly affected during ageing. Here we have used antibodies to individual subunits of complexes I-IV to investigate their expression in the colonic epithelium from human subjects aged 18-84. We show that in approximately 50% of crypts with any form of respiratory chain deficiency, decreased expression of subunits of multiple complexes is observed. Furthermore we have sequenced the entire mitochondrial genome of a number of cells with multiple complex defects and have found a wide variety of point mutations in these cells affecting a number of different protein encoding and RNA encoding genes. Finally we discuss the possible mechanisms by which multiple respiratory chain complex defects may occur in these cells.

Mitochondrial DNA mutations in human colonic crypt stem cells.

The mitochondrial genome encodes 13 essential subunits of the respiratory chain and has remarkable genetics based on uniparental inheritance. Within human populations, the mitochondrial genome has a high rate of sequence divergence with multiple polymorphic variants and thus has played a major role in examining the evolutionary history of our species. In recent years it has also become apparent that pathogenic mitochondrial DNA (mtDNA) mutations play an important role in neurological and other diseases. Patients harbor many different mtDNA mutations, some of which are mtDNA mutations, some of which are inherited, but others that seem to be sporadic. It has also been suggested that mtDNA mutations play a role in aging and cancer, but the evidence for a causative role in these conditions is less clear. The accumulated data would suggest, however, that mtDNA mutations occur on a frequent basis. In this article we describe a new phenomenon: the accumulation of mtDNA mutations in human colonic crypt stem cells that result in a significant biochemical defect in their progeny. These studies have important consequences not only for understanding of the finding of mtDNA mutations in aging tissues and tumors, but also for determining the frequency of mtDNA mutations within a cell.