SARS-CoV-2 causes dysfunction in human iPSC-derived brain microvascular endothelial cells potentially by modulating the Wnt signaling pathway.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19), which is associated with various neurological symptoms, including nausea, dizziness, headache, encephalitis, and epileptic seizures. SARS-CoV-2 is considered to affect the central nervous system (CNS) by interacting with the blood-brain barrier (BBB), which is defined by tight junctions that seal paracellular gaps between brain microvascular endothelial cells (BMECs). Although SARS-CoV-2 infection of BMECs has been reported, the detailed mechanism has not been fully elucidated. METHODS: Using the original strain of SARS-CoV-2, the infection in BMECs was confirmed by a detection of intracellular RNA copy number and localization of viral particles. BMEC functions were evaluated by measuring transendothelial electrical resistance (TEER), which evaluates the integrity of tight junction dynamics, and expression levels of proinflammatory genes. BMEC signaling pathway was examined by comprehensive RNA-seq analysis. RESULTS: We observed that iPSC derived brain microvascular endothelial like cells (iPSC-BMELCs) were infected with SARS-CoV-2. SARS-CoV-2 infection resulted in decreased TEER. In addition, SARS-CoV-2 infection decreased expression levels of tight junction markers CLDN3 and CLDN11. SARS-CoV-2 infection also increased expression levels of proinflammatory genes, which are known to be elevated in patients with COVID-19. Furthermore, RNA-seq analysis revealed that SARS-CoV-2 dysregulated the canonical Wnt signaling pathway in iPSC-BMELCs. Modulation of the Wnt signaling by CHIR99021 partially inhibited the infection and the subsequent inflammatory responses. CONCLUSION: These findings suggest that SARS-CoV-2 infection causes BBB dysfunction via Wnt signaling. Thus, iPSC-BMELCs are a useful in vitro model for elucidating COVID-19 neuropathology and drug development.

Phagocytosis model of calcium oxalate monohydrate crystals generated using human induced pluripotent stem cell-derived macrophages.

Macrophages play a role in nephrolithiasis, offering the possibility of developing macrophage-mediated preventive therapies. To establish a system for screening drugs that could prevent the formation of kidney stones, we aimed to develop a model using human induced pluripotent stem cell (iPSC)-derived macrophages to study phagocytosis of calcium oxalate monohydrate (COM) crystals. Human iPSCs (201B7) were cultured. CD14+ monocytes were recovered using a stepwise process that involved the use of growth factors and cytokines. These cells were then allowed to differentiate into M1 and M2 macrophages. The macrophages were co-cultured with COM crystals and used in the phagocytosis experiments. Live cell imaging and polarized light observation via super-resolution microscopy were used to visualize phagocytosis. Localization of phagocytosed COM crystals was observed using transmission electron microscopy. Intracellular fluorescence intensity was measured using imaging cytometry to quantify phagocytosis. Human iPSCs successfully differentiated into M1 and M2 macrophages. M1 macrophages adhered to the culture plate and moved COM crystals from the periphery to cell center over time, whereas M2 macrophages did not adhere to the culture plate and actively phagocytosed the surrounding COM crystals. Fluorescence assessment over a 24-h period showed that M2 macrophages exhibited higher intracellular fluorescence intensity (5.65-times higher than that of M1 macrophages at 4.5 h) and maintained this advantage for 18 h. This study revealed that human iPSC-derived macrophages have the ability to phagocytose COM crystals, presenting a new approach for studying urinary stone formation and highlighting the potential of iPSC-derived macrophages as a tool to screen nephrolithiasis-related drugs.

Air-liquid interface culture and modified culture medium promote the differentiation of human induced pluripotent stem cells into intestinal epithelial cells.

An in vitro system that evaluates pharmacokinetics in the small intestine is crucial for the development of oral drugs. We produced human induced pluripotent stem cell-derived small intestinal epithelial cells (hiSIECs) with high drug metabolizing enzyme and drug transporter activities. However, the gene expression of our hiSIECs partially differed from that of the human small intestine, with low drug metabolizing enzyme activities. Therefore, we used air-liquid interface (ALI) culture and 5-aza-2'-deoxycytidine (5AZA)-free medium to generate hiSIECs (novel hiSIECs). Novel hiSIECs showed enhanced gene expression of drug metabolizing enzymes, such as cytochrome P450 (CYP)3A4, CYP2C9, CYP2C19, and carboxylesterase 2 that are highly expressed in the small intestine. In addition, the expression of genes involved in nutrient absorption-one of the major functions of the small intestine-also increased. The novel hiSIECs expressed ZO-1 and E-cadherin. Moreover, the novel hiSIECs exhibited a barrier function that allowed low lucifer yellow permeation. The novel hiSIECs showed high activities of CYP3A4, CYP2C9, and CYP2C19, which are abundantly expressed in the small intestine. In conclusion, the novel hiSIECs have great potential as an in vitro system to evaluate pharmacokinetics in the small intestine.

New Maintenance Culture Method for Intestinal Stem Cells Derived from Human Induced Pluripotent Stem Cells.

Most orally administered drugs exert their effects after being absorbed in the small intestine. Therefore, new drugs must undergo nonclinical pharmacokinetic evaluations in the small intestine. Enterocytes derived from human induced pluripotent stem cells (hiPSCs) are expected to be used in the evaluation system, as they reflect human intestinal characteristics more accurately; moreover, several differentiation protocols are available for these cells. However, enterocytes derived from hiPSCs have drawbacks such as time, cost, and lot-to-lot differences. Hence, to address these issues, we attempted to maintain hiPSC-derived intestinal stem cells (ISCs) that can differentiate into various intestinal cells by regulating various pathways. Although our previous attempt was partly successful, the drawbacks of elevated cost and complicated handling remained, because more than 10 factors (A 83-01, CHIR99021, epidermal growth factor, basic fibroblast growth factor, SB202190, nicotinamide, N-acetylcysteine, valproic acid, Wnt3a, R-spondin 1, and noggin) are needed to maintain ISCs. Therefore, in this study, we successfully maintained ISCs using only five factors, including growth factors. Moreover, we generated not only enterocytes but also intestinal organoids from the maintained ISCs. Thus, our novel findings provided a time-saving and cost-effective culture method for enterocytes derived from hiPSCs.

Aß42 treatment of the brain side reduced the level of flotillin from endothelial cells on the blood side via FGF-2 signaling in a blood-brain barrier model.

Our previous study showed that the flotillin level is decreased in the blood of patients with Alzheimer's disease (AD) when compared to that of patients with non-AD and vascular dementia; however, the molecular mechanism remains to be determined. In this study, to elucidate whether Aß accumulation in the brain has an effect on the blood flotillin level, we used our previously established blood-brain barrier (BBB) culture model using microvascular endothelial cells obtained from human induced pluripotent stem cells (iBMECs) and astrocytes prepared from rat cortex. In this BBB model with iBMECs plated on the upper compartment (blood side) and astrocytes plated on the lower compartment (brain side), the trans-endothelial electrical resistance values are high (over 1500 Ωm2) and stable during experiments. We found that the addition of Aß42 (0.5 and 2 µM) to the brain side significantly reduced the level of flotillin secreted by iBMECs on the blood side. The level of basic fibroblast growth factor (FGF-2) in the brain side was significantly reduced by Aß42 treatment, and was accompanied by a reduction in the level of phosphorylation of the fibroblast growth factor receptor in iBMECs. The brain-side Aß42 treatment-induced reduction of flotillin secretion into the blood side was restored in a dose-dependent manner by the addition of FGF-2 into the brain side. These results indicated that Aß accumulation in the brain side reduced FGF-2 release from astrocytes, which attenuated FGF-2-mediated iBMECs signaling via the FGF-2 receptor, and thereby reduced flotillin secretion from iBMECs on the blood side. Our findings revealed a novel signaling pathway crossing the BBB from the brain side to the blood side, which is different from the classical intramural periarterial drainage or lymphatic-system-to-blood pathway.

Generation of Brain Microvascular Endothelial-like Cells from Human iPS Cell-Derived Endothelial Progenitor Cells Using TGF-ß Receptor Inhibitor, Laminin 511 Fragment, and Neuronal Cell Culture Supplements.

Brain microvascular endothelial cells (BMECs) constitute the blood-brain barrier (BBB), which prevents the transfer of substances into the brain. Recently, in vitro BBB models using human-induced pluripotent stem (iPS) cell-derived brain microvascular endothelial-like cells (iBMELCs) have been created. However, it is suggested that iBMELCs differentiated by the existing methods are different from the BMECs that occur in vivo. This study aimed to establish iBMELCs generated via human iPS cell-derived endothelial progenitor cells (iEPCs) (E-iBMELCs). Expanded and cryopreserved iEPCs were thawed and differentiated into mature endothelial cells under various conditions. Intercellular barriers were significantly enhanced in E-iBMELCs using a B-27 supplement, transforming growth factor-ß receptor inhibitor, and laminin 511 fragment. Expression of the endothelial cell markers was higher in the E-iBMELCs generated in this study compared with conventional methods. In addition, E-iBMELCs expressed P-glycoprotein. E-iBMELCs developed in this study will significantly contribute to drug discovery for neurodegenerative diseases and might elucidate the pathogenesis of neurodegenerative diseases associated with BBB disruption.

Ivermectin Inhibits HBV Entry into the Nucleus by Suppressing KPNA2.

Hepatitis B virus (HBV) specifically infects human hepatocytes and increases the risks of cirrhosis and liver cancer. Currently, nucleic acid analogs are the main therapeutics for chronic hepatitis caused by HBV infection. Although nucleic acid analogs can eliminate HBV DNA by inhibiting HBV reverse transcriptase, they cannot lead to negative conversion of covalently closed circular DNA (cccDNA) and hepatitis B surface antigen (HBsAg). In this study, we revealed that the antifilarial drug ivermectin suppresses HBV production by a different mechanism from the nucleic acid analog entecavir or Na+ taurocholate co-transporting polypeptide-mediated entry inhibitor cyclosporin A. Ivermectin reduced the levels of several HBV markers, including HBsAg, in HBV-infected human hepatocellular carcinoma cells (HepG2-hNTCP-C4 cells) and humanized mouse hepatocytes (PXB hepatocytes). In addition, ivermectin significantly decreased the expression of HBV core protein and the nuclear transporter karyopherin α2 (KPNA2) in the nuclei of HepG2-hNTCP-C4 cells. Furthermore, depletion of KPNA1-6 suppressed the production of cccDNA. These results suggest that KPNA1-6 is involved in the nuclear import of HBV and that ivermectin suppresses the nuclear import of HBV by inhibiting KPNA2. This study demonstrates the potential of ivermectin as a novel treatment for hepatitis B.

Effects of human induced pluripotent stem cell-derived intestinal organoids on colitis-model mice.

Introduction: Ulcerative colitis (UC) is an inflammatory bowel disease characterized by repeated remissions and relapses. Immunosuppressive drugs have facilitated the induction and maintenance of remission in many patients with UC. However, immunosuppressive drugs cannot directly repair impaired intestinal mucosa and are insufficient for preventing relapse. Therefore, new treatment approaches to repair the damaged epithelium in UC have been attempted through the transplantation of intestinal organoids, which can be differentiated into mucosa by embedding in Matrigel, generated from patient-derived intestinal stem cells. The method, however, poses the challenge of yielding sufficient cells for UC therapy, and patient-derived cells might already have acquired pathological changes. In contrast, human induced pluripotent stem (iPS) cells generated from healthy individuals are infinitely proliferated and can be differentiated into target cells. Recently developed human iPS cell-derived intestinal organoids (HIOs) aim to generate organoids that closely resemble the adult intestine. However, no study till date has reported HIOs injected into in vivo inflammatory models, and it remains unclear whether HIOs with cells that closely resemble the adult intestine or with intestinal stem cells retain the better ability to repair tissue in colitis. Methods: We generated two types of HIOs via suspension culture with and without small-molecule compounds: HIOs that include predominantly more intestinal stem cells [HIO (A)] and those that include predominantly more intestinal epithelial and secretory cells [HIO (B)]. We examined whether the generated HIOs engrafted in vivo and compared their ability to accelerate recovery of the damaged tissue. Results: Findings showed that the HIOs expressed intestinal-specific markers such as caudal-type homeobox 2 (CDX2) and villin, and HIOs engrafted under the kidney capsules of mice. We then injected HIOs into colitis-model mice and found that the weight and clinical score of the mice injected with HIO (A) recovered earlier than that of the mice in the sham group. Further, the production of mucus and the expression of cell proliferation markers and tight junction proteins in the colon tissues of the HIO (A) group were restored to levels similar to those observed in healthy mice. However, neither HIO (A) nor HIO (B) could be engrafted into the colon. Conclusions: Effective cell therapy should directly repair tissue by engraftment at the site of injury. However, the difference in organoid property impacting the rate of tissue repair in transplantation without engraftment observed in the current study should be considered a critical consideration in the development of regenerative medicine using iPS-derived organoids.

An Efficient Method for the Differentiation of Human iPSC-Derived Endoderm toward Enterocytes and Hepatocytes.

The endoderm, differentiated from human induced pluripotent stem cells (iPSCs), can differentiate into the small intestine and liver, which are vital for drug absorption and metabolism. The development of human iPSC-derived enterocytes (HiEnts) and hepatocytes (HiHeps) has been reported. However, pharmacokinetic function-deficiency of these cells remains to be elucidated. Here, we aimed to develop an efficient differentiation method to induce endoderm formation from human iPSCs. Cells treated with activin A for 168 h expressed higher levels of endodermal genes than those treated for 72 h. Using activin A (days 0-7), CHIR99021 and PI-103 (days 0-2), and FGF2 (days 3-7), the hiPSC-derived endoderm (HiEnd) showed 97.97% CD-117 and CD-184 double-positive cells. Moreover, HiEnts derived from the human iPSC line Windy had similar or higher expression of small intestine-specific genes than adult human small intestine. Activities of the drug transporter P-glycoprotein and drug-metabolizing enzyme cytochrome P450 (CYP) 3A4/5 were confirmed. Additionally, Windy-derived HiHeps expressed higher levels of hepatocyte- and pharmacokinetics-related genes and proteins and showed higher CYP3A4/5 activity than those derived through the conventional differentiation method. Thus, using this novel method, the differentiated HiEnts and HiHeps with pharmacokinetic functions could be used for drug development.

Generation of Budding-Like Intestinal Organoids from Human Induced Pluripotent Stem Cells.

Human induced pluripotent stem (iPS) cell-derived intestinal organoids have low invasiveness; however, the current differentiation method does not reflect the crypt-villus-like structure due to structural immaturity. Here, we generated budding-like organoids that formed epithelial tissue-like structures and had the characteristics of the mature small intestine from human iPS cells. They showed a high expression of drug transporters and induced the expression of cytochrome P450 3A4 and P-glycoprotein. When treated with tumor necrosis factor-α and/or transforming growth factor-ß, the budding-like organoids replicated the pathogenesis of mucosal damage or intestinal fibrosis. Upon dissociation and seeding on cell culture inserts, the organoids retained intestinal characteristics, forming polarized intestinal folds with approximately 400 Ω × cm2 transepithelial electrical resistance. This novel method has great potential for disease modeling and drug screening applications.

Gellan Gum Promotes the Differentiation of Enterocytes from Human Induced Pluripotent Stem Cells.

The evaluation of drug pharmacokinetics in the small intestine is critical for developing orally administered drugs. Caucasian colon adenocarcinoma (Caco-2) cells are employed to evaluate drug absorption in preclinical trials of drug development. However, the pharmacokinetic characteristics of Caco-2 cells are different from those of the normal human small intestine. Besides this, it is almost impossible to obtain primary human intestinal epithelial cells of the same batch. Therefore, human iPS cell-derived enterocytes (hiPSEs) with pharmacokinetic functions similar to human intestinal epithelial cells are expected to be useful for the evaluation of drug absorption. Previous studies have been limited to the use of cytokines and small molecules to generate hiPSEs. Dietary fibers play a critical role in maintaining intestinal physiology. We used gellan gum (GG), a soluble dietary fiber, to optimize hiPSE differentiation. hiPSEs cocultured with GG had significantly higher expression of small intestine- and pharmacokinetics-related genes and proteins. The activities of drug-metabolizing enzymes, such as cytochrome P450 2C19, and peptide transporter 1 were significantly increased in the GG treatment group compared to the control group. At the end point of differentiation, the percentage of senescent cells increased. Therefore, GG could improve the differentiation efficiency of human iPS cells to enterocytes and increase intestinal maturation by extending the life span of hiPSEs.

Application of Human Induced Pluripotent Stem Cell-Derived Intestinal Organoids as a Model of Epithelial Damage and Fibrosis in Inflammatory Bowel Disease.

Inflammatory bowel disease, which typically manifests as Crohn's disease and ulcerative colitis, is caused by the abnormal production of cytokines such as tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-ß. These cytokines damage intestinal epithelial cells and trigger fibrosis, respectively, for which the current in vitro models have many limitations. Therefore, we tested whether human induced pluripotent stem cell-derived intestinal organoids (HiOs) can mimic inflammatory bowel disease (IBD), and whether such a model is suitable for drug screening. HiOs were treated with TNF-α and TGF-ß to construct mucosal damage and fibrosis models. TNF-α diminished the mRNA expression of intestinal epithelial cell and goblet cell markers in HiOs. TNF-α also induced epithelial cell damage and degradation of tight junctions but not in the presence of infliximab, an antibody used in the clinic to deplete TNF-α. Furthermore, permeation of the non-absorbable marker FD-4 was observed in HiOs treated with TNF-α or ethylene glycol tetraacetic acid (EGTA), but not in the presence of infliximab. In contrast, TNF-α and TGF-ß induced mRNA expression of mesenchymal and fibrosis markers, as well as epithelial-mesenchymal transition. SB431542, a TGF-ß inhibitor, significantly reversed these events. The data indicate that HiOs mimic mucosal damage and fibrosis due to IBD and are thus suitable models for drug screening.

Inhibition of transforming growth factor beta signaling pathway promotes differentiation of human induced pluripotent stem cell-derived brain microvascular endothelial-like cells.

BACKGROUND: The blood-brain barrier (BBB) plays an important role as a biological barrier by regulating molecular transport between circulating blood and the brain parenchyma. In drug development, the accurate evaluation of BBB permeability is essential to predict not only the efficacy but also the safety of drugs. Recently, brain microvascular endothelial-like cells derived from human induced pluripotent stem cells (iPSCs) have attracted much attention. However, the differentiation protocol has not been optimized, and the enhancement of iPSC-derived brain microvascular endothelial-like cells (iBMELCs) function is required to develop highly functional BBB models for pharmaceutical research. Thus, we attempted to improve the functions of differentiated iBMELCs and develop a versatile BBB model by modulating TGF-ß signaling pathway without implementing complex techniques such as co-culture systems. METHODS: iPSCs were differentiated into iBMELCs, and TGF-ß inhibitor was used in the late stage of differentiation. To investigate the effect of TGF-ß on freezing-thawing, iBMELCs were frozen for 60-90 min or 1 month. The barrier integrity of iBMELCs was evaluated by transendothelial electrical resistance (TEER) values and permeability of Lucifer yellow. Characterization of iBMELCs was conducted by RT-qPCR, immunofluorescence analysis, vascular tube formation assay, and acetylated LDL uptake assay. Functions of efflux transporters were defined by intracellular accumulation of the substrates. RESULTS: When we added a TGF-ß inhibitor during iBMELCs differentiation, expression of the vascular endothelial cell marker was increased and blood vessel-like structure formation was enhanced. Furthermore, TEER values were remarkably increased in three iPSC lines. Additionally, it was revealed that TGF-ß pathway inhibition suppressed the damage caused by the freezing-thawing of iBMELCs. CONCLUSION: We succeeded in significantly enhancing the function and endothelial characteristics of iBMELCs by adding a small molecular compound, a TGF-ß inhibitor. Moreover, the iBMELCs could maintain high barrier function even after freezing-thawing. Taken together, these results suggest that TGF-ß pathway inhibition may be useful for developing iPSC-derived in vitro BBB models for further pharmaceutical research.

Laminin 221 fragment is suitable for the differentiation of human induced pluripotent stem cells into brain microvascular endothelial-like cells with robust barrier integrity.

BACKGROUND: In vitro blood-brain barrier (BBB) models using human induced pluripotent stem (iPS) cell-derived brain microvascular endothelial-like cells (iBMELCs) have been developed to predict the BBB permeability of drug candidates. For the differentiation of iBMELCs, Matrigel, which is a gelatinous protein mixture, is often used as a coating substrate. However, the components of Matrigel can vary among lots, as it is obtained from mouse sarcoma cells with the use of special technics and also contains various basement membranes. Therefore, fully defined substrates as substitutes for Matrigel are needed for a stable supply of iBMELCs with less variation among lots. METHODS: iBMELCs were differentiated from human iPS cells on several matrices. The barrier integrity of iBMELCs was evaluated based on transendothelial electrical resistance (TEER) values and permeability of fluorescein isothiocyanate-dextran 4 kDa (FD4) and Lucifer yellow (LY). Characterization of iBMELCs was conducted by RT-qPCR and immunofluorescence analysis. Functions of efflux transporters were defined by intracellular accumulation of the substrates in the wells of multiwell plates. RESULTS: iBMELCs differentiated on laminin 221 fragment (LN221F-iBMELCs) had higher TEER values and lower permeability of LY and FD4 as compared with iBMELCs differentiated on Matrigel (Matrigel-iBMELCs). Besides, the gene and protein expression levels of brain microvascular endothelial cells (BMEC)-related markers were similar between LN221F-iBMELCs and Matrigel-iBMELCs. Moreover, both Matrigel- and LN221F-iBMELCs had functions of P-glycoprotein and breast cancer resistance protein, which are essential efflux transporters for barrier functions of the BBB. CONCLUSION: The fully defined substrate LN221F presents as an optimal coating matrix for differentiation of iBMELCs. The LN221F-iBMELCs had more robust barrier function for a longer period than Matrigel-iBMELCs with characteristics of BMECs. This finding will contribute the establishment of an iBMELC supply system for pharmacokinetic and pathological models of the BBB.

Efficient differentiation and purification of human induced pluripotent stem cell-derived endothelial progenitor cells and expansion with the use of inhibitors of ROCK, TGF-ß, and GSK3ß.

Endothelial cells (ECs) and endothelial progenitor cells (EPCs) play crucial roles in maintaining vascular health and homeostasis. Both cell types have been used in regenerative therapy as well as in various in vitro models; however, the properties of primary human ECs and EPCs are dissimilar owing to differences in genetic backgrounds and sampling techniques. Human induced pluripotent stem cells (hiPSCs) are an alternative cell source of ECs and EPCs. However, owing to the low purity of differentiated cells from hiPSCs, purification via an antigen-antibody reaction, which damages the cells, is indispensable. Besides, owing to limited expandability, it is difficult to produce these cells in large numbers. Here we report the development of relatively simple differentiation and purification methods for hiPSC-derived EPCs (iEPCs). Furthermore, we discovered that a combination of three small molecules, that is, Y-27632 (a selective inhibitor of Rho-associated, coiled-coil containing protein kinase [ROCK]), A 83-01 (a receptor-like kinase inhibitor of transforming growth factor beta [TGF-ß]), and CHIR-99021 (a selective inhibitor of glycogen synthase kinase-3ß [GSK3ß] that also activates Wnt), dramatically stimulated protein synthesis-related pathways and enhanced the proliferative capacity of iEPCs. These findings will help to establish a supply system of EPCs at an industrial scale.

Establishment of a novel culture method for maintaining intestinal stem cells derived from human induced pluripotent stem cells.

The small intestine plays an important role in the pharmacokinetics of orally administered drugs due to the presence of drug transporters and drug-metabolizing enzymes. However, few appropriate methods exist to investigate intestinal pharmacokinetics. Induced pluripotent stem (iPS) cells can form various types of cells and represent a potentially useful tool for drug discovery. We previously reported that differentiated enterocytes from human iPS cells are useful for pharmacokinetic studies; however, the process is time and resource intensive. Here, we established a new two-dimensional culture method for maintaining human iPS-cell-derived intestinal stem cells (ISCs) with differentiation potency and evaluated their ability to differentiate into enterocytes exhibiting appropriate pharmacokinetic function. The culture method used several factors to activate signalling pathways required for maintaining stemness, followed by differentiation into enterocytes. Functional evaluation was carried out to verify epithelial-marker expression and inducibility and activity of metabolic enzymes and transporters. Our results confirmed the establishment of an ISC culture method for maintaining stemness and verified that the differentiated enterocytes from the maintained ISCs demonstrated proper pharmacokinetic function. Thus, our findings describe a time- and cost-effective approach that can be used as a general evaluation tool for evaluating intestinal pharmacokinetics.

Active Phagocytosis and Diachronic Processing of Calcium Oxalate Monohydrate Crystals in an in vitro Macrophage Model.

BACKGROUND: We previously discovered that renal macrophages (Mφs) phagocytose renal calcium oxalate monohydrate (COM) crystals. This study investigated the processing of engulfed crystals using in vitro models. METHODS: J774.1 mouse Mφs were exposed to COM crystals and observed for 24 h using polarized light microscopy with/without cytochalasin B (CB), an inhibitor of phagocytosis, to confirm active crystal phagocytosis. LysoTracker and immunohistochemical staining using transmission electron microscopy for lysosomal-associated membrane protein 1 were used to confirm engulfed COM crystal uptake into lysosomes. Diachronic tracking of specific Mφs was performed to capture the entire course of engulfed COM crystal processing using polarized light microscopy. Follow-up studies of fluorescent COM (f-COM) crystals using imaging cytometry were performed in the presence and absence of nigericin to dissipate the pH gradient in acidic organelles. RESULTS: Phagocytosis rates increased with COM density and were significantly lower in cells treated with CB (p < 0.01). We observed that engulfed crystals colocalized within lysosomes of the Mφs; moreover, diachronic observation indicated that the engulfed COM crystals were subdivided during Mφ division and eliminated by the 7th day of culture. Additionally, imaging cytometry showed that the fluorescence level of f-COM crystals in the nigericin (-) group after 48 h was significantly lower than that in the nigericin (+) group. CONCLUSIONS: This study confirmed active phagocytosis and lysosomal processing of engulfed COM crystals by Mφs. This discovery is expected to contribute to the development of future drugs that enhance the COM crystal phagocytic ability of Mφs.

Isolation of induced pluripotent stem cell-derived endothelial progenitor cells from sac-like structures.

Transplanted endothelial progenitor cells (EPCs) repair blood vessels and exert regenerative effects on disorders such as lower limb ischemia. EPCs serve as a model for pathophysiological and pharmacokinetic studies, which is important for drug discovery. However, primary human EPCs are phenotypically unstable, which limits their clinical utility. Therefore, we employed human induced pluripotent stem (iPS) cells to circumvent this problem. Here we focused on human iPS cell-derived sac-like structures (iPS-sacs), which contain endothelial lineage cells and hematopoietic lineage cells. Previous studies isolated only hematopoietic lineage cells from iPS-sacs. Therefore, here we attempted to isolate EPCs. However, iPS-sacs generated by a published protocol did not contain sufficient EPCs. Therefore, to generate iPS-sacs highly enriched in EPCs, we added the glycogen synthase kinase 3 beta (GSK3ß) inhibitor CHIR-99021 to the culture medium early during differentiation. The cells rapidly differentiated into mesoderm to yield abundant EPCs, and CHIR-99021 increased the proportion of EPCs contained in iPS-sacs. EPCs, which were purified using anti-platelet endothelial cell adhesion molecule (PECAM1) antibody-conjugated beads, expressed markers of immature endothelial cells. Purified EPCs formed tube-like structures and incorporated acetylated low density lipoprotein (Ac-LDL), reflecting endothelial phenotypes. The simple method described here will likely improve regenerative medicine and facilitate basic studies on the endothelial lineage.

Contribution of rat embryonic stem cells to xenogeneic chimeras in blastocyst or 8-cell embryo injection and aggregation.

The ultimate goal of regenerative medicine is the transplantation of a target organ generated by the patient's own cells. Recently, a method of organ generation using pluripotent stem cells (PSCs) and blastocyst complementation was reported. This approach is based on chimeric animal generation using an early embryo and PSCs, and the contribution of PSCs to the target organ is key to the method's success. However, the contribution rate of PSCs in target organs generated by different chimeric animal generation methods remains unknown. In this study, we used 8-cell embryo aggregation, 8-cell embryo injection, and blastocyst injection to generate interspecies chimeric mice using rat embryonic stem (ES) cells and then investigated the differences in the contribution rate of the rat ES cells. The rate of chimeric mouse generation was the highest using blastocyst injection, followed in order by 8-cell embryo injection and 8-cell embryo aggregation. However, the contribution rate of rat ES cells was the highest in chimeric neonates generated by 8-cell embryo injection, and the difference was statistically significant in the liver. Live functionality was confirmed by analyzing the expression of rat hepatocyte-derived drug-metabolizing enzyme. Collectively, these findings indicate that the 8-cell embryo injection method is the most suitable for generation of PSC-derived organs via chimeric animal generation, particularly for the liver.

Using human iPS cell-derived enterocytes as novel in vitro model for the evaluation of human intestinal mucosal damage.

OBJECTIVE AND DESIGN: The primary component in gut mucus is mucin 2 (MUC2) secreted by goblet cells. Fluctuations in MUC2 expression are considered a useful indicator for evaluating mucosal damage and protective effect of various agents using animal studies. However, there are few in vitro studies evaluating mucosal damage using MUC2 as the indicator. Hence, we attempted to establish a novel in vitro model with MUC2 as the indicator for evaluating drug-induced mucosal damage and protective effect using enterocytes derived from human iPS cells. METHODS: Compounds were added into enterocytes derived from human iPS cells, and MUC2 mRNA and protein expression levels were evaluated. Further, the effect of compounds on membrane permeability was investigated. RESULTS: Nonsteroidal anti-inflammatory drugs were found to decrease MUC2 mRNA expression in enterocytes, whereas mucosal protective agents increased mRNA levels. Changes in MUC2 protein expression were consistent with those of mRNA. Additionally, our results indicated that indomethacin caused mucosal damage, affecting membrane permeability of the drug. Moreover, we observed protective effect of rebamipide against the indomethacin-induced permeability increase. CONCLUSIONS: The developed model could facilitate evaluating drug-induced mucosal damage and protective effects of various agents and could impact drug development studies regarding pharmacological efficacy and safety.