Gastric organoids: Progress and remaining challenges

The stomach is a complex and physiologically necessary organ, yet large differences in physiology between mouse and human stomachs have impeded translation of physiological discoveries and drug screens performed using murine gastric tissues. Gastric cancer (GC) is a global health threat, with a high mortality rate and limited treatment options. The heterogeneous nature of GC makes it poorly suited for current one size fits all standard treatments. In this review, we discuss the rapidly evolving field of gastric organoids, with a focus on studies expanding cultures from primary human tissues and describing the benefits of mouse organoid models. We introduce the differing methods for culturing healthy gastric tissue from adult tissues or pluripotent stem cells, discuss the promise these systems have for preclinical drug screens, and highlight applications of organoids for precision medicine. Finally, we discuss the limitations of these models and look to the future to present potential ways gastric organoids will advance treatment options for patients with GC

Host gastric corpus microenvironment facilitates Ascaris suum larval hatching and infection in a murine model.

Ascariasis (roundworm) is the most common parasitic helminth infection globally and can lead to significant morbidity in children including chronic lung disease. Children become infected with Ascaris spp. via oral ingestion of eggs. It has long been assumed that Ascaris egg hatching and larval translocation across the gastrointestinal mucosa to initiate infection occurs in the small intestine. Here, we show that A. suum larvae hatched in the host stomach in a murine model. Larvae utilize acidic mammalian chitinase (AMCase; acid chitinase; Chia) from chief cells and acid pumped by parietal cells to emerge from eggs on the surface of gastric epithelium. Furthermore, antagonizing AMCase and gastric acid in the stomach decreases parasitic burden in the liver and lungs and attenuates lung disease. Given Ascaris eggs are chitin-coated, the gastric corpus would logically be the most likely organ for egg hatching, though this is the first study directly evincing the essential role of the host gastric corpus microenvironment. These findings point towards potential novel mechanisms for therapeutic targets to prevent ascariasis and identify a new biomedical significance of AMCase in mammals

Pepsin does not induce Ascaris larva hatching.

Ascaris eggs are treated with 4 or 8 μg/ml of pepsin in pH = 2 overnight. Larvae hatched from the eggs were counted and hatch rate was calculated. (PDF)</p

Tamoxifen reduces AMCase and acid production in stomach which limits <i>Ascaris</i> larval migration.

(A) BALB/c mice were pretreated with tamoxifen intraperitoneally before challenged by oral gavage with 2,500 eggs of Ascaris, in PBS or vehicle containing recombinant AMCase at pH 2. Reduction of (B) AMCase and (C) H+-K+ ATPase was confirmed by qPCR. (D) Larval isolated from the liver 4 days post infection were quantified. (n≥4, mean±S.E.M, *pB, C) or one-way ANOVA followed by Bonferroni’s test for multiple comparison (D). Data are shown as representative of two independent experiments. Illustration generated by Biorender.com).</p

Intestine of mice post <i>Ascaris</i> larva infection.

Wildtype mice were oral gavaged with 2,500 Ascaris eggs and euthanized at 12 hours, 24 hours or 4 days post infection. H&E staining were carried out on sections of different intestine tissues. (PDF)</p

Fig 2 -

AMCase in acidic conditions promotes Ascaris larval hatching: (A)Ascaris eggs were treated with recombinant AMCase under acidic and neutral pH in vitro. Larval hatch rate was quantified post treatment. (B-C) BALB/c mice were challenged by oral gavage with 2,500 eggs of Ascaris and stomach tissue was harvested 1 hour or 1 day post infection to extract total RNA. Chia1 (B) and Atp4a (C) expression level were quantified by qPCR. (D) BALB/c mice were pretreated with AMCase inhibitor, omeprazole, 10% NaHCO3 or vehicle control before challenged by oral gavage with 2,500 eggs of Ascaris. (E-F) Larva isolated from the liver 4 days post infection under different conditions was quantified. (n≥4, mean±S.E.M, *pA), two-tailed Student’s t-test (B, C, E) or one-way ANOVA followed by Tukey’s test for multiple comparison (F). Data are shown as representative of two independent experiments. Illustration generated by Biorender.com).</p

<i>Ascaris suum</i> larva hatch in and migrate through the stomach: BALB/c mice were challenged by oral gavage with 2,500 eggs of <i>Ascaris</i> once.

(A-B) Evan’s blue dye (EBD) was introduced intravenously to mice 1 day post infection. Recovery of EBD from (A) the intestine segments and (B) the stomach were quantified. (C) H&E and (D) PAS staining were performed on stomach sections 30 minutes post infection. Brown triangles indicate foveolar cells and black arrows indicate larval penetration across gastric mucosa. (n≥4, mean±S.E.M, *p<0.05 using two-tailed Student’s t-test. Magnification: 200×. Scale bar: 150μm. Data are shown as representative of three independent experiments).</p

Fig 4 -

Omeprazole and AMCase inhibitor reduce airway hyperresponsiveness induced by Ascaris larval migration through the lungs (A) BALB/c mice were pretreated with omeprazole plus AMCase inhibitor or vehicle control before challenge by oral gavage with 2,500 eggs of Ascaris. (B) Larval burden was quantified from the lungs 8 days post infection. (C) Respiratory system resistance (RRS) was assessed after intravenous injection of increasing doses of acetylcholine (Ach) at 12 days post infection. (D) Body weight loss in mice was measured at 12 days post infection. (E) Type-2 cytokines were quantitated by ELISA from deaggregated lung supernatants. (n = 4, mean±S.E.M, *pB) or one-way ANOVA followed by Tukey’s test for multiple comparison (C-E). Data are shown as representative of two independent experiments. Illustration generated by Biorender.com).</p

<i>Ascaris</i> larva does not hatch in intestinal conditions.

Ascaris eggs were treated in pH = 2 for 30 minutes and then in different intestinal conditions overnight. Larval hatch rate was then calculated. (PDF)</p