Society: AGA

Background
Electrogastrography (EGG) non-invasively evaluates gastric motility but is widely viewed as lacking clinical utility. Gastric Alimetry® is a new diagnostic test that combines high-resolution body surface gastric mapping (BSGM) with validated symptom profiling, with the goal of overcoming numerous technical limitations of the EGG. This study directly compared EGG and BSGM to define performance differences in spectral analysis.

Methods
Comparisons between Gastric Alimetry BSGM and EGG were conducted by protocolized evaluation of 178 subjects (110 controls; 68 nausea and vomiting (NVS) and/or type 1 diabetes (T1D)). Data collection was identical. Comparisons followed standard methodologies for each test, with statistical evaluations for group-level differences, symptom correlations, and patient-level classifications. Four spectral metrics were computed for BSGM tests (Gastric Alimetry Rhythm IndexTM (GA-RI), Principal Gastric Frequency (PGF), BMI-Adjusted Amplitude, and Fed:Fasted Amplitude Ratio)¹ and EGG tests (% time normal frequency, dominant frequency, amplitude, and amplitude ratio)². Patient-level classifications were determined by a blinded consensus panel reference standard³ and automatedly, using published reference values as cutoffs for EGG and BSGM metrics^2,4.

Results
Group-level: BSGM showed tighter frequency ranges vs EGG in controls (median 3.04 cpm (IQR 2.90-3.18) vs 2.88 (1.50-3.12); p<0.0001). Both tests detected rhythm instability in NVS (p<0.001) and T1D (p<0.05), but EGG showed opposite frequency effects in T1D (2.50 vs controls 2.88; p=0.28) to BSGM (3.15 vs 3.04; p=0.0004). Symptom correlations: GA-RI correlated with nausea, pain, bloating, and total symptom burden; PGF deviation with excessive fullness, pain, bloating; % time in normal frequency correlated with bloating (p<0.05). Patient-level: EGG sensitivity was 1.0, specificity 0.38; BSGM sensitivity 1.0, specificity 0.96 (Figure 1).

Conclusions and Inferences
EGG detected group-level differences in patients, but lacked symptom correlations and showed poor accuracy at patient-level classification, explaining EGG’s weak clinical utility. BSGM demonstrated substantial performance improvements over EGG across all domains.

References
1. Schamberg G et al.. Neurogastroenterol Motil. Published online November 21, 2022:e14491.
2. Yin J, Chen JDZ. Journal of Neurogastroenterology and Motility. 2013;19(1):5-17.
3. Gharibans AA et al. Sci Transl Med. 2022;14(663):eabq3544.
4. Varghese C et al. Am J Gastroenterol; In Press [doi:10.1101/2022.07.25.22278036]

Figure 1: Individual classifications using rhythmic stability metrics and reference labels. (A) Confusion matrix for GA-RI ≥ 0.25. (B) Confusion matrix for % time normal frequency ≥ 70%. (C) ROC curves with the location on the curve associated (published thresholds indicated by a dot). (D) Quantitative evaluation.

<b>Individual classifications using rhythmic stability metrics and reference labels. (A) Confusion matrix for GA-RI ≥ 0.25. (B) Confusion matrix for % time normal frequency ≥ 70%. (C) ROC curves with the location on the curve associated (published thresholds indicated by a dot). (D) Quantitative evaluation.</b>

Individual classifications using rhythmic stability metrics and reference labels. (A) Confusion matrix for GA-RI ≥ 0.25. (B) Confusion matrix for % time normal frequency ≥ 70%. (C) ROC curves with the location on the curve associated (published thresholds indicated by a dot). (D) Quantitative evaluation.

Purpose: Enteric neuropathies result from abnormalities of the enteric nervous system (ENS). The goal of this study was to determine the feasibility of isolating, expanding, and transplanting autologous enteric neural stem cells (ENSCs) to improve colonic function in a non-lethal mouse model of colonic aganglionosis.
Methods: Wnt1::Cre;R26iDTR (Wnt1-iDTR) mice at 2-3 months of age were used. ENSCs were isolated from a short segment of small intestine resected from Wnt1-iDTR mice in which focal colonic aganglionosis was created by injection of diphtheria toxin (DT) into the wall of the mid-colon. Autologous ENSCs were expanded in culture to form neurospheres, transduced with lentiviral GFP or channelrhodopsin-2 (ChR2) vector, and transplanted into the aganglionic segment 2 weeks following the first surgery (n=12). Immunohistochemistry, organ bath studies, and optogenetics were used to determine outcomes 1 to 8 weeks following cell transplantation. Results were compared to two groups: R26iDTR mice with DT injection (Control, n=8) and DT-induced aganglionosis (DT-AG, n=8) without cell transplantation using multiple t-test analysis.
Results: ENSCs, as neurospheres, were successfully obtained from mouse small intestine (mean 477 ± 123 neurospheres per cm of small intestine, n=12). Transplanted ENSCs were identified within the aganglionic colon based on GFP fluorescence. Immunohistochemical evaluation demonstrated extensive cell migration, nerve fiber projections, and differentiation into neurons and glial cells. Organ bath studies demonstrated that the lack of contraction of DT-induced aganglionic smooth muscle was rescued by ENSC transplantation (0.10 ± 0.09 gm in DT-AG vs 1.45 ± 0.23 gm in DT-AG + Cells, n = 4, p<0.001) 3 weeks following cell transplant. Interestingly, restoration of muscle contractility progressed over time. Contractile activity of colonic smooth muscle in mice with DT-induced aganglionosis was normalized by ENSC transplantation 8 weeks after surgery (3.11 ± 0.13 gm in Control vs 2.95 ± 0.39 gm in DT-AG + Cells, n = 4, p>0.05). Optogenetic analysis in mice receiving ENSCs expressing ChR2 confirmed functional neuromuscular signalling between transplanted autologous ENSC-derived neurons and the colonic smooth muscle.
Conclusions: Autologously derived ENSCs successfully engrafted within aganglionic gut in vivo, where neuroglial differentiation and functional integration with colonic smooth muscle occurred. By 8 weeks after cell transplant, normalization of colonic smooth muscle contractility was observed. This study, using a novel and non-lethal mouse model of colonic aganglionosis, demonstrates the potential of autologous ENSCs to improve functional outcomes in neurointestinal disease and lays the groundwork for clinical application of this regenerative cell-based strategy.

Allan Goldstein

Massachusetts General Hospital

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