Introduction
Gastroparesis (GP) is a chronic disorder characterized by delayed gastric emptying without any mechanical obstruction of the gastric outlet. Patients with GP often present with postprandial nausea and vomiting, bloating, abdominal pain, and, in severe cases, significant weight loss [1]. The prevalence is rising at an alarming rate, with an estimated 9.6 men and 37.8 women per 100,000 persons affected [2, 3]. Despite such a significant disease burden, curative therapy remains unavailable and the pathophysiology of GP remains poorly understood.
Interstitial cells of Cajal (ICC) were initially identified by Cajal [4] and are involved in the transmission of neuronal signaling to the smooth muscles of the gastrointestinal tract, thereby acting as a pacemaker. ICC have been previously implicated in the pathogenesis of gastrointestinal motility disorders including GP. However, information on the number of ICC in patients and normal individuals is sparse due to biopsy during routine endoscopy being insufficient to quantify and study ICC, which are mostly located in the gastric muscle. Gastric per-oral endoscopic myotomy (G-POEM) is a newer technique offered to treat refractory GP. This novel endoscopic procedure establishes a submucosal tunnel and exposes the muscular layer, allowing direct biopsy [5]. This study attempts to compare the quantity of ICC in gastric muscle samples obtained via G-POEM and autopsy in individuals with and without GP. The study will provide important data for further pathophysiology research.
Methods
The gastroparesis group comprised patients with a confirmed diagnosis of GP via a gastric emptying study who underwent a planned G-POEM from October 2022 to November 2022. Procedure methods were described in detail in our previous study [6]. Briefly here, a mucosal entry site ∼5 cm proximal to the pylorus was created at the posterior gastric antrum. A 2-cm mucosal incision was made using a hybrid knife (ERBE USA Incorporated, Marietta, GA, USA). A submucosal tunnel was then created from the mucosal entry site to the pylorus. A selective myotomy of the pyloric circular muscle was subsequently performed, starting from the pylorus and extending ∼1–2 cm proximally into the antrum. After myotomy, biopsy of the muscle at the antrum was performed by using routine cold biopsy forceps. The mucosal entry site was closed using hemostatic clips after biopsy (Supplementary Figure 1).
The control group comprised autopsy-obtained gastric specimens of a healthy adult population from September 2022 to November 2022. Samples were obtained in the same anatomical area as those of the gastroparesis group.
Following formalin fixation and routine tissue processing, the paraffin-embedded tissue was sectioned for routine hematoxylin and eosin (H&E) staining as well as for immunohistochemical staining for DOG-1 (Leica ready to use, clone K9). The H&E and DOG-1-stained slides were then reviewed by a gastrointestinal pathologist and DOG-1+ ICC were counted in 4-mm2 areas (Supplementary Figure 2). A two-sample t-test was used to determine statistical significance between ICC in patients with or without GP. Demographic information such as age, gender, etc. was also documented.
Results
Six patients with GP who underwent the G-POEM procedure were enrolled and compared with six control specimens. Table 1 highlights the data for the two groups. The mean ages of patients in the gastroparesis group and the control group were 60.5 ± 12.4 and 40.8 ± 15.8 years, respectively (P < 0.05). The average body mass index (BMI) of patients in the gastroparesis group was 35.8 ± 5.4 kg/m2 and in the control group was 26.6 ± 7.1 kg/m2 (P < 0.05). The average number of ICC in the gastroparesis group was significantly lower than that in the control group (397 ± 222 vs 1,422 ± 256 cells per 4 mm2 area, P < 0.0001). Three patients were diabetics (50%). Supplementary Figure 2 shows the DOG-1 immunohistochemical stain highlighting ICC in the gastric samples.
Table 1.
Data for gastroparesis and control groups
| Object | Gender | Age, years | BMI, kg/m2 | Medical history | Cause of gastroparesis | Nuclear medicine gastric emptying results | Number of interstitial cells of Cajal per 4 mm2 |
|---|---|---|---|---|---|---|---|
| Patient 1 | F | 44 | 41.6 | Hypertension, osteoarthritis, obesity | Idiopathic | Delayed | 700 |
| Patient 2 | F | 49 | 32.0 | DM, obesity | DM | Delayed | 265 |
| Patient 3 | F | 63 | 31.0 | Hypertension, hyperlipidemia, obesity | Post-surgical | Delayed | 181 |
| Patient 4 | M | 70 | 31.0 | Hypertension, DM, obesity | DM | Delayed | 520 |
| Patient 5 | F | 60 | 43.5 | DM, obesity, gastroesophageal reflux disease | DM | Delayed | 166 |
| Patient 6 | M | 77 | 34.8 | Achalasia, obesity | Post-surgical | Delayed | 550 |
| Control 1 | M | 60 | 25.1 | Hypertension | – | – | 1,539 |
| Control 2 | F | 35 | 19.8 | Seizure | – | – | 1,703 |
| Control 3 | M | 20 | 18.7 | None | – | – | 1,271 |
| Control 4 | M | 32 | 29.2 | None | – | – | 1,657 |
| Control 5 | M | 59 | 28.6 | Hypertension | – | – | 1,330 |
| Control 6 | M | 39 | 38.1 | Obesity | – | – | 1,035 |
F, female; M, male; BMI, body mass index; DM, diabetes mellitus.
Discussion
This pilot study provides reliable data that the quantity of ICC is significantly lower in patients with GP compared with healthy controls. To our knowledge, this is the first such study examining at a cellular level the gastric muscle layer obtained via the novel method (G-POEM and autopsy) in patients affected with and without GP.
A major challenge in evaluating the role of ICC in the pathophysiology of GP is obtaining reliable biopsies of the gastric muscle. Endoscopic full-thickness biopsy and endoscopic ultrasound guided fine-needle aspiration to evaluate for ICC are reported, although these methods are either invasive or indirect and it is difficult to obtain a sufficient sample for reliable pathological examination [7–9]. G-POEM provides a direct biopsy of the gastric muscle for quantification of ICC [5]. This study confirms the safety and efficacy of direct muscular-layer biopsy during G-POEM.
Animal models have demonstrated a variety of dysmotility manifestations related to the abundance or depletion of ICC. ICC depletion is consistently associated with delayed gastric emptying in mice with type I diabetes. Other studies suggest that mice with type 2 diabetes have either accelerated or decreased gastric emptying, depending on whether their ICC levels are elevated or decreased. Interestingly, ICC loss and abnormal morphology may be reversed by treatment in animals [9, 10].
We found a significantly lower number of ICC in GP patients when directly compared with a healthy adult population. However, there are limitations in this study. First, the control sample is from autopsy, and also the BMI and ages are significantly different between the two groups. But it would be impossible to subject normal individuals to a G-POEM procedure for the purposes of study. Other controls, such as patients undergoing gastric surgery, could be considered in the future. Second, we did not differentiate the type of ICC; each type of ICC may have a different function. Third, the number of subjects was relatively small.
This method of obtaining ICC from the gastric antrum muscular layer during the G-POEM procedure and at autopsy is reliable, effective, and safe, and will enhance future investigations into the human ICC. Further areas of research should include studies with a larger number of patients to confirm the results as well as analysing the morphology, function, and subtypes of ICC at a cellular level.
Supplementary Material
Contributor Information
Shazia Rashid, Division of Gastroenterology and Hepatology, Louisiana State University, Health Sciences Center Shreveport, Shreveport, LA, 71103, USA.
Michelle Neice, Division of Gastroenterology and Hepatology, Louisiana State University, Health Sciences Center Shreveport, Shreveport, LA, 71103, USA.
Hailey Canezaro, Division of Gastroenterology and Hepatology, Louisiana State University, Health Sciences Center Shreveport, Shreveport, LA, 71103, USA.
Victoria Andrus, Division of Gastroenterology and Hepatology, Louisiana State University, Health Sciences Center Shreveport, Shreveport, LA, 71103, USA.
Maryam Mubashir, Division of Gastroenterology and Hepatology, Louisiana State University, Health Sciences Center Shreveport, Shreveport, LA, 71103, USA.
Syed Musa Raza, Division of Gastroenterology and Hepatology, Louisiana State University, Health Sciences Center Shreveport, Shreveport, LA, 71103, USA.
James Traylor, Department of Pathology, Louisiana State University Health Sciences Center Shreveport, Shreveport, LA 71103, USA.
Hidehiro Takei, Department of Pathology, Louisiana State University Health Sciences Center Shreveport, Shreveport, LA 71103, USA.
Qiang Cai, Division of Gastroenterology and Hepatology, Louisiana State University, Health Sciences Center Shreveport, Shreveport, LA, 71103, USA.
Supplementary Data
Supplementary data is available at Gastroenterology Report online.
Conflicts of Interest
None declared.
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