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The use of human tissue stem cell-derived organoids has advanced our knowledge of human physiological and pathophysiological processes that are unable to be studied using other model systems. Increased understanding of human epithelial tissues including intestine, stomach, liver, pancreas, lung, and brain have been achieved using organoids. However, it is not yet clear whether these cultures recapitulate in vivo organ-to-organ signaling or communication. In this work, we demonstrate that mature stem cell-derived intestinal and liver organoid cultures each express functional molecules that modulate bile acid uptake and recycling. These organoid cultures can be physically coupled in a Transwell system and display increased secretion of fibroblast growth factor 19 (FGF19) (intestine) and downregulation of P450 enzyme cholesterol 7 α-hydroxylase (CYP7A) (liver) in response to apical exposure of the intestine to bile acids. This work establishes that organoid cultures can be used to study and therapeutically modulate interorgan interactions and advance the development of personalized approaches to medical care. NEW & NOTEWORTHY Interorgan signaling is a critical feature of human biology and physiology, yet has remained difficult to study due to the lack of in vitro models. Here, we demonstrate that physical coupling of ex vivo human intestine and liver epithelial organoid cultures recapitulates in vivo interorgan bile acid signaling. These results suggest that coupling of multiple organoid systems provides new models to investigate interorgan communication and advances our knowledge of human physiological and pathophysiological processes.

We investigated the effects of PKC-stimulating 12-deoxyphorbol 13-phenylacetate 20-acetate (DOPPA) and phorbol 12-myristate 13-acetate (PMA) phorbol esters on cAMP-dependent, forskolin (FSK)-stimulated, short-circuit Cl−current ( ISC-cAMP) generation by colonocyte monolayers. These agonists elicited different actions depending on their dose and incubation time; PMA effects at the onset (SCgeneration. DOPPA failed to elicit similar responses. Whereas chronic (24 h) exposure to both agents inhibited FSK-stimulated transcellular and apical membrane ISC-cAMP, the effects of DOPPA were more complex: this conventional PKC-β-specific agonist also stimulated Ba2+-sensitive basolateral membrane-dependent facilitation of transcellular ISC-cAMP. PMA did not elicit a similar phenomenon. Prolonged exposure to high-dose PMA but not DOPPA led to apical membrane ISC-cAMP recovery. Changes in PKC α-, β1-, γ-, and ε-isoform membrane partitioning and expression correlated with these findings. PMA-induced transcellular ISCcorrelated with PKC-α membrane association, whereas low doses of both agents inhibited transcellular and apical membrane ISC-cAMP, increased PKC-β1, decreased PKC-β2membrane association, and caused reciprocal changes in isoform mass. During the apical membrane ISC-cAMP recovery after prolonged high-dose PMA exposure, an almost-complete depletion of cellular PKC-β1and a significant reduction in PKC-ε mass occurred. Thus activated PKC-β1and/or PKC-ε prevented, whereas activated PKC-α facilitated, apical membrane ISC-cAMP. PKC-β-dependent augmentation of transcellular ISC-cAMP at the level of the basolateral membrane demonstrated that transport events with geographically distinct subcellular membranes can be independently regulated by the PKC β-isoform.

We investigated the effects of chronically applied PKC-stimulating phorbol esters on subcellular CFTR expression and localization in polarized HT-29 Cl.19A monolayers. Modulation of PKC activity with the PKC-β-specific agonist 12-deoxyphorbol 13-phenylacetate 20-acetate (DOPPA) or nonisoform-selective PMA altered monolayer CFTR immunofluorescence. A decrease in the CFTR signal within the luminal cellular pole was noted with both phorbol esters. Volumetric analysis of the intracellular CFTR signal revealed that both compounds promoted CFTR accumulation into punctate vesicle-like structures found adjacent to the cellular tight junction [labeled with zona occludens (ZO)-1 antibody], extending basally (DOPPA) into the cell. Puncta were more frequent with DOPPA and larger in size with PMA. DOPPA also promoted ZO-1 accumulation at tricellular corners associated with enhanced CFTR puncta number. The observed loss of CFTR immunofluorescence signal induced by low-dose PMA was related to CFTR sequestration into fewer cytoplasmic puncta and correlated with larger increases in PKC substrate phosphorylation. Both phorbol esters downregulated steady-state cellular CFTR mRNA levels by 70%. However, the effects of DOPPA and PMA were largely independent of CFTR biosynthesis: expression levels were 80–85% of control, and the glycosylation status of immunoprecipitated protein remained largely unchanged. Thus changes in cellular CFTR localization correlated with our companion study showing that PMA-induced inhibition of transcellular cAMP-dependent short-circuit current ( ISC) was accompanied by cytoplasmic PKC-β2accumulation and modest activation of PKC-β1and PKC-ε. The inhibitory effect of DOPPA on ISCwas related solely to increased cytoplasmic PKC-β2levels. Thus PKC-β2is hypothesized to participate in the regulation of CFTR apical plasma membrane targeting within the constitutive cellular biosynthetic pathway.

A synthetic, channel-forming peptide, derived from the α-subunit of the glycine receptor (M2GlyR), has been synthesized and modified by adding four lysine residues to the NH2terminus (N-K4-M2GlyR). In Ussing chamber experiments, apical N-K4-M2GlyR (250 μM) increased transepithelial short-circuit current ( Isc) by 7.7 ± 1.7 and 10.6 ± 0.9 μA/cm2in Madin-Darby canine kidney and T84 cell monolayers, respectively; these values are significantly greater than those previously reported for the same peptide modified by adding the lysines at the COOH terminus (Wallace DP, Tomich JM, Iwamoto T, Henderson K, Grantham JJ, and Sullivan LP. Am J Physiol Cell Physiol 272: C1672–C1679, 1997). N-K4-M2GlyR caused a concentration-dependent increase in Isc( k[1/2]= 190 μM) that was potentiated two- to threefold by 1-ethyl-2-benzimidazolinone. N-K4-M2GlyR-mediated increases in Iscwere insensitive to changes in apical cation species. Pharmacological inhibitors of endogenous Cl−conductances [glibenclamide, diphenylamine-2-dicarboxylic acid, 5-nitro-2-(3-phenylpropylamino)benzoic acid, 4,4′-dinitrostilben-2,2′-disulfonic acid, indanyloxyacetic acid, and niflumic acid] had little effect on N-K4-M2GlyR-mediated Isc. Whole cell membrane patch voltage-clamp studies revealed an N-K4-M2GlyR-induced anion conductance that exhibited modest outward rectification and modest time- and voltage-dependent activation. Planar lipid bilayer studies yielded results indicating that N-K4-M2GlyR forms a 50-pS anion conductance with a k[1/2]for Cl−of 290 meq. These results indicate that N-K4-M2GlyR forms an anion-selective channel in epithelial monolayers and shows therapeutic potential for the treatment of hyposecretory disorders such as cystic fibrosis.