Cellular changes in diabetic and idiopathic gastroparesis

Abstract

Background & aims: Cellular changes associated with diabetic and idiopathic gastroparesis are not well described. The aim of this study was to describe histologic abnormalities in gastroparesis and compare findings in idiopathic versus diabetic gastroparesis.

Methods: Full-thickness gastric body biopsy specimens were obtained from 40 patients with gastroparesis (20 diabetic) and matched controls. Sections were stained for H&E and trichrome and immunolabeled with antibodies against protein gene product (PGP) 9.5, neuronal nitric oxide synthase (nNOS), vasoactive intestinal peptide, substance P, and tyrosine hydroxylase to quantify nerves, S100β for glia, Kit for interstitial cells of Cajal (ICC), CD45 and CD68 for immune cells, and smoothelin for smooth muscle cells. Tissue was also examined by transmission electron microscopy.

Results: Histologic abnormalities were found in 83% of patients. The most common defects were loss of ICC with remaining ICC showing injury, an abnormal immune infiltrate containing macrophages, and decreased nerve fibers. On light microscopy, no significant differences were found between diabetic and idiopathic gastroparesis with the exception of nNOS expression, which was decreased in more patients with idiopathic gastroparesis (40%) compared with diabetic patients (20%) by visual grading. On electron microscopy, a markedly increased connective tissue stroma was present in both disorders.

Conclusions: This study suggests that on full-thickness biopsy specimens, cellular abnormalities are found in the majority of patients with gastroparesis. The most common findings were loss of Kit expression, suggesting loss of ICC, and an increase in CD45 and CD68 immunoreactivity. These findings suggest that examination of tissue can lead to valuable insights into the pathophysiology of these disorders and offer hope that new therapeutic targets can be found.

Figure 1

Representative images for PGP9.5 immunoreactivity (PGP9.5-IR) used as a general neuronal marker, nNOS immunoreactivity (nNOS-IR) and VIP immunoreactivity (VIP-IR). Panel A: PGP9.5-IR. Left image is control and right image is from a patient with idiopathic gastroparesis with <25% decrease of PGP 9.5-IR in the circular muscle (CM) and longitudinal muscle (LM) and myenteric plexus (MP) region. Panel B: nNOS-IR. Left image is control, middle image and right image are from patients with diabetic gastroparesis and idiopathic gastroparesis respectively showing decreased nNOS-IR in the CM and LM and MP regions. Panel C: VIP-IR. Left image is control; middle image and right image are from patients with diabetic gastroparesis and idiopathic gastroparesis respectively showing decreased VIP-IR in the CM and LM and MP regions. Scale bar = 100μm.

Figure 2

Representative images for Kit immunoreactivity as a marker for interstitial cells of Cajal (ICC). Panel A: Control. Panel B: Diabetic gastroparesis with decreased ICC. Panel C: Idiopathic gastroparesis with decreased ICC. CM: circular muscle layer; LM: longitudinal muscle layer; MP: myenteric plexus region. Scale bar = 100μm.

Figure 3

Representative images for smoothelin immunoreactivity as a marker for smooth muscle cells and trichrome stained sections as a marker for fibrosis. Panels A and D: Controls. Panel B: Diabetic gastroparesis with decreased smoothelin immunoreactivity. Panel C: Idiopathic gastroparesis with decreased smoothelin immunoreactivity. Red signal represents smoothelin IR, blue signal is DAPI counterstain. Panel E: Diabetic gastroparesis with fibrosis. Panel F: Idiopathic gastroparesis with fibrosis CM: circular muscle layer; LM: longitudinal muscle layer; MP: myenteric plexus region. Scale bar = 100μm.

Figure 4

Images of CD45 and CD68 immunoreactivity. Panel A: CD45 immunoreactivity in a control. Panel B: CD68 immunoreactivity from the same section as panel A. Panel C: CD45 and CD68 merged. Panel D: CD45 immunoreactivity from diabetic gastroparesis with increased number of CD45 positive cells. Panel E: CD68 immunoreactivity from the same section as panel D. Panel F: CD45 and CD68 immunoreactivity. Arrow heads point to CD45 positive, CD68 negative IR. Arrows point to co-localized immunoreactivity. CM: circular muscle layer; LM: longitudinal muscle layer; MP: myenteric plexus region. Scale bar = 100μm.

Figure 5

Diabetic gastroparesis and idiopathic gastroparesis. Panels A–C are from diabetic gastroparesis and D–E from idiopathic gastroparesis. Panel A: An interstitial cell of Cajal (ICC) with large vacuoles in the cytoplasm and a discontinuous, thick basal lamina (asterisks). SMC: smooth muscle cell. Panel B: Smooth muscle cells immersed in a fibrotic stroma and separated, except for small junctional areas, most of which are gap junctions (asterisks). Panel C: Nerve bundle surrounded by a very thick basal lamina and numerous collagen fibers. The nerve endings are empty. Panel D: A presumptive ICC with swollen mitochondria and intracytoplasmatic lamellar bodies (asterisk) near a small nerve bundle (N). SMC: smooth muscle cell. Panel E: Nerve bundle endowed in a fibrotic capsule. The nerve endings (n) are filled with filaments and do not contain synaptic vesicles. SMC immersed in a fibrotic stroma and far away to each other. Sch: Schwann (glial) cell with a clear cytoplasm and several lipofuscinic bodies. Bar: A, B, D, E =1 μm, C=0.8 μm. Please refer to the supplementary figure 10 for EM controls.