Decreased expression of TRAAK channels in Hirschsprung's disease: a possible cause of postoperative dysmotility

Utility of colonic manometry in children with Hirschsprung disease

OBJECTIVES

Abnormal motility of the residual colon has been reported in post-pull-through Hirschsprung disease (PT-HSCR) patients with persistent defecation problems. We reviewed the role of colonic manometry (CM) in the management of defecation disorders in these patients.

METHODS

We retrospectively reviewed the medical record of PT-HSCR children who underwent CM for persistent symptoms of abnormal defecation. We reviewed their clinical course and its relation to CM findings.

RESULTS

Thirty PT-HSCR patients underwent CM, of which five were diagnosed with transition zone pull-through and were excluded. Of the remaining 25 patients, 16 had colonic dysmotility, 8 had normal CM, and one had colonic hypermotility. In patients with dysmotility, five responded to ongoing medical management, three required surgical intervention (ileostomy), three remained symptomatic with medical management but not yet received surgical intervention, and five were lost to follow-up. In patients with normal CM, four responded to ongoing medical therapy, two required additional surgery (antegrade enema procedure), and two were lost to follow-up. The patient with hypermotility improved with adding loperamide.

CONCLUSIONS

Colonic dysmotility can occur in PT-HSCR patients with persistent defecation problems. CM was helpful in delineating the degree of colonic neuromuscular dysfunction. CM results were used in conjunction with other clinical data to determine optimal management. Our findings support that medical management should first be optimized before consideration of colonic manometry and surgical interventions.

Translational research in Hirschprung's disease at the National Children's Research Centre in Dublin

Hirschsprung's disease (HD) is a congenital condition characterised by aganglionosis in the distal bowel. Over the years, at the National Children's Research Centre (NCRC), HD has been one of the most prominent and successful research areas for Prof. Prem Puri's research team. Research fellows from around the world came to the NCRC to work on both animal and human studies of HD and, cumulatively, made important discoveries in this field, publishing a total of 144 HD articles in peer-reviewed journals. Through their published work, the NCRC has been recognised as the leading international centre for the investigation of HD and its allied disorders. In this review, I will summarise the main findings from this work.

Persistent bowel dysfunction after surgery for Hirschsprung’s disease: A neuropathological perspective

Hirschsprung’s disease (HD) is a congenital disorder, characterized by aganglionosis in the distal part of the gastrointestinal tract. Despite complete surgical resection of the aganglionic segment, both constipation and fecal incontinence persist in a considerable number of patients with limited treatment options. There is growing evidence for structural abnormalities in the ganglionic bowel proximal to the aganglionosis in both humans and animals with HD, which may play a role in persistent bowel dysfunction. These abnormalities include: (1) Histopathological abnormalities of enteric neural cells; (2) Imbalanced expression of neurotransmitters and neuroproteins; (3) Abnormal expression of enteric pacemaker cells; (4) Abnormalities of smooth muscle cells; and (5) Abnormalities within the extracellular matrix. Hence, a better understanding of these previously unrecognized neuropathological abnormalities may improve follow-up and treatment in patients with HD suffering from persistent bowel dysfunction following surgical correction. In the long term, further combination of clinical and neuropathological data will hopefully enable a translational step towards more individual treatment for HD.

Negative Influence by the Force: Mechanically Induced Hyperpolarization via K2P Background Potassium Channels

The two-pore domain K_2P subunits form background (leak) potassium channels, which are characterized by constitutive, although not necessarily constant activity, at all membrane potential values. Among the fifteen pore-forming K_2P subunits encoded by the KCNK genes, the three members of the TREK subfamily, TREK-1, TREK-2, and TRAAK are mechanosensitive ion channels. Mechanically induced opening of these channels generally results in outward K⁺ current under physiological conditions, with consequent hyperpolarization and inhibition of membrane potential-dependent cellular functions. In the past decade, great advances have been made in the investigation of the molecular determinants of mechanosensation, and members of the TREK subfamily have emerged among the best-understood examples of mammalian ion channels directly influenced by the tension of the phospholipid bilayer. In parallel, the crucial contribution of mechano-gated TREK channels to the regulation of membrane potential in several cell types has been reported. In this review, we summarize the general principles underlying the mechanical activation of K_2P channels, and focus on the physiological roles of mechanically induced hyperpolarization.