Bernard, C

AbstractBackgroundAnimal studies have increasingly highlighted the role of macrophages in the development of delayed gastric emptying. However, their role in the pathophysiology of human gastroparesis is unclear. Our aim was to determine changes in macrophages and other cell types in the gastric antrum muscularis propria of patients with diabetic and idiopathic gastroparesis.MethodsFull thickness gastric antrum biopsies were obtained from patients enrolled in the Gastroparesis Clinical Research Consortium (11 diabetic, 6 idiopathic) and 5 controls. Immunolabeling and quantitative assessment was done for interstitial cells of Cajal (ICC) (Kit), enteric nerves protein gene product 9.5, neuronal nitric oxide synthase, vasoactive intestinal peptide, substance P, tyrosine hydroxylase), overall immune cells (CD45) and anti‐inflammatory macrophages (CD206). Gastric emptying was assessed using nuclear medicine scintigraphy and symptom severity using the Gastroparesis Cardinal Symptom Index.ResultsBoth diabetic and idiopathic gastroparesis patients showed loss of ICC as compared to controls (Mean [standard error of mean]/hpf: diabetic, 2.28 [0.16]; idiopathic, 2.53 [0.47]; controls, 6.05 [0.62]; P=.004). Overall immune cell population (CD45) was unchanged but there was a loss of anti‐inflammatory macrophages (CD206) in circular muscle (diabetic, 3.87 [0.32]; idiopathic, 4.16 [0.52]; controls, 6.59 [1.09]; P=.04) and myenteric plexus (diabetic, 3.83 [0.27]; idiopathic, 3.59 [0.68]; controls, 7.46 [0.51]; P=.004). There was correlation between the number of ICC and CD206‐positive cells (r=.55, P=.008). Enteric nerves (PGP9.5) were unchanged: diabetic, 33.64 (3.45); idiopathic, 41.26 (6.40); controls, 46.80 (6.04).ConclusionLoss of antral CD206‐positive anti‐inflammatory macrophages is a key feature in human gastroparesis and it is associates with ICC loss.

AbstractBackgroundThe SCN5A‐encoded voltage‐gated sodium channel NaV1.5 is expressed in human jejunum and colon. Mutations in NaV1.5 are associated with gastrointestinal motility disorders. The rat gastrointestinal tract expresses voltage‐gated sodium channels, but their molecular identity and role in rat gastrointestinal electrophysiology are unknown.MethodsThe presence and distribution of Scn5a‐encoded NaV1.5 was examined by PCR, Western blotting and immunohistochemistry in rat jejunum. Freshly dissociated smooth muscle cells were examined by whole cell electrophysiology. Zinc finger nuclease was used to target Scn5a in rats. Lentiviral‐mediated transduction with shRNA was used to target Scn5a in rat jejunum smooth muscle organotypic cultures. Organotypic cultures were examined by sharp electrode electrophysiology and RT‐PCR.Key ResultsWe found NaV1.5 in rat jejunum and colon smooth muscle by Western blot. Immunohistochemistry using two other antibodies of different portions of NaV1.5 revealed the presence of the ion channel in rat jejunum. Whole cell voltage‐clamp in dissociated smooth muscle cells from rat jejunum showed fast activating and inactivating voltage‐dependent inward current that was eliminated by Na+ replacement by NMDG+. Constitutive rat Scn5a knockout resulted in death in utero. NaV1.5 shRNA delivered by lentivirus into rat jejunum smooth muscle organotypic culture resulted in 57% loss of Scn5a mRNA and several significant changes in slow waves, namely 40% decrease in peak amplitude, 30% decrease in half‐width, and 7 mV hyperpolarization of the membrane potential at peak amplitude.Conclusions & InferencesScn5a‐encoded NaV1.5 is expressed in rat gastrointestinal smooth muscle and it contributes to smooth muscle electrophysiology.

Abstract Background There is increasing evidence for specific cellular changes in the stomach of patients with diabetic ( DG ) and idiopathic ( IG ) gastroparesis. The most significant findings are loss of interstitial cells of Cajal ( ICC ), neuronal abnormalities, and an immune cellular infiltrate. Studies done in diabetic mice have shown a cytoprotective effect of CD 206+ M2 macrophages. To quantify overall immune cellular infiltrate, identify macrophage populations, and quantify CD 206+ and i NOS + cells. To investigate associations between cellular phenotypes and ICC . Methods Full thickness gastric body biopsies were obtained from non‐diabetic controls (C), diabetic controls ( DC ), DG , and IG patients. Sections were labeled for CD 45, CD 206, Kit, i NOS , and putative human macrophage markers ( HAM 56, CD 68, and EMR 1). Immunoreactive cells were quantified from the circular muscle layer. Key Results Significantly fewer ICC were detected in DG and IG tissues, but there were no differences in the numbers of cells immunoreactive for other markers between patient groups. There was a significant correlation between the number of CD 206+ cells and ICC in DG and DC patients, but not in C and IG and a significant correlation between i NOS + cells and ICC in the DC group, but not the other groups. CD 68 and HAM 56 reliably labeled the same cell populations, but EMR 1 labeled other cell types. Conclusions & Inferences Depletion of ICC and correlation with changes in CD 206+ cell numbers in DC and DG patients suggests that in humans, like mice, CD 206+ macrophages may play a cytoprotective role in diabetes. These findings may lead to novel therapeutic options, targeting alternatively activated macrophages.