Activation of the 5-hydroxytryptamine 4 receptor ameliorates tight junction barrier dysfunction in the colon of type 1 diabetic mice

Hyperglycemia drives dysfunction of the intestinal barrier. 5-Hydroxytryptaine 4 receptor (5-HT 4R) agonists have been considered therapeutics for constipation in clnic. However, the roles of 5-HT 4R activation in mucosa should be fully realized. Here, we investigate the effects of 5-HT 4R activation on diabetes-induced disruption of the tight junction (TJ) barrier in the colon. Not surprisingly, the TJ barrier in diabetic mice with or without 5-HT 4R is tremendously destroyed, as indicated by increased serum fluorescein isothiocyanate (FITC)-dextran and decreased transepithelial electrical resistance (TER). Simultaneously, decreased expressions of TJ proteins are shown in both wild-type (WT) and 5-HT 4R knockout (KO) mice with diabetes. Notably, chronic treatment with intraperitoneal injection of a 5-HT 4R agonist in WT mice with diabetes repairs the TJ barrier and promotes TJ protein expressions, including occludin, claudin-1 and ZO-1, in the colon, whereas a 5-HT 4R agonist does not improve TJ barrier function or TJ protein expressions in 5-HT 4R KO mice with diabetes. Furthermore, stimulation of 5-HT 4R inhibits diabetes-induced upregulation of myosin light chain kinase (MLCK), Rho-associated coiled coil protein kinase 1 (ROCK1), and phosphorylated myosin light chain (p-MLC), which are key molecules that regulate TJ integrity, in the colonic mucosa of WT mice. However, such action induced by a 5-HT 4R agonist is not observed in 5-HT 4R KO mice with diabetes. These findings indicate that 5-HT 4R activation may restore TJ integrity by inhibiting the expressions of MLCK, ROCK1 and p-MLC, improving epithelial barrier function in diabetes.

Irreversible inhibitors of the proline racemase (PRAC) unveil innovative mechanism of action as antibacterial against Clostridioides difficile

Proline racemases (PRAC), catalyzing the L-proline and D-proline interconversion, are essential factors in eucaryotic pathogenes such as Trypanosoma cruzi, Trypanosoma vivax and Clostridioides difficile. If the discovery of irreversible inhibitors of Trypanosoma cruzi PRAC (TcPRAC) led to innovative therapy of the Chagas disease, no inhibitors of CdPRAC have been discovered to date. However, Clostridioides difficile, due to an increased incidence in recent years, is considered as a major cause of health threat. In this work, we have taken into account the similarity between TcPRAC and CdPRAC enzymes to design new inhibitors of CdPRAC. Starting from (E) 4-oxopent-2-enoic acid TcPRAC irreversible inhibitors, we synthesized 4-aryl substituted analogues and evaluated their CdPRAC enzymatic inhibition against eleven strains of Clostridioides difficile. This study resulted in promising candidates and allowed for identification of (E)-4-(3-bromothiophen-2-yl)-4-oxobut-2-enoic acid 20 that was chosen for complementary in vivo studies and did not reveal in vivo toxicity.

Towards Biohybrid Lung: Induced Pluripotent Stem Cell Derived Endothelial Cells as Clinically Relevant Cell Source for Biologization

In order to provide an alternative treatment option to lung transplantation for patients with end-stage lung disease, we aim for the development of an implantable biohybrid lung (BHL), based on hollow fiber membrane (HFM) technology used in extracorporeal membrane oxygenators. Complete hemocompatibility of all blood contacting surfaces is crucial for long-lasting BHL durability and can be achieved by their endothelialization. Autologous endothelial cells (ECs) would be the ideal cell source, but their limited proliferation potential excludes them for this purpose. As induced pluripotent stem cell-derived ECs enable the generation of a large number of ECs, we assessed and compared their capacity to form a viable and confluent monolayer on HFM, while indicating physiologic EC-specific anti-thrombogenic and anti-inflammatory properties. ECs were generated from three different human iPSC lines, and seeded onto fibronectin-coated poly-4-methyl-1-pentene (PMP) HFM. Following phenotypical characterization, ECs were analyzed for their thrombogenic and inflammatory behavior with or without TNFα induction, using FACS and qRT-PCR. Complementary, leukocyte- and platelet adhesion assays were carried out. The capacity of the iPSC-ECs to reendothelialize cell-free monolayer areas was assessed in a scratch assay. ECs sourced from umbilical cord blood (hCBECs) were used as control. iPSC-derived ECs formed confluent monolayers on the HFM and showed the typical EC-phenotype by expression of VE-cadherin and collagen-IV. A low protein and gene expression level of E-selectin and tissue factor was detected for all iPSC-ECs and the hCBECs, while a strong upregulation of these markers was noted upon stimulation with TNFα. This was in line with the physiological and strong induction of leukocyte adhesion detected after treatment with TNFα, iPSC-EC and hCBEC monolayers were capable of reducing thrombocyte adhesion and repopulating scratched areas. iPSCs offer the possibility to provide patient-specific ECs in abundant numbers needed to cover all blood contacting surfaces of the BHL with a viable, non-thrombogenic and non-inflammatory monolayer. iPSC-EC clones can differ in terms of their reendothelialization rate, and pro-inflammatory response. However, a less profound inflammatory response may even be advantageous for BHL application. With the proven ability of the seeded iPSC-ECs to reduce thrombocyte adhesion, we expect that thrombotic events that could lead to BHL occlusion can be avoided, and thus, justifies further studies on enabling BHL long-term application.

Emerging targets in drug discovery against neurodegenerative diseases: Control of synapsis disfunction by the RhoA/ROCK pathway

Synaptic spine morphology is controlled by the activity of Rac1, Cdc42 and RhoA, which need to be finely balanced, and in particular RhoA/ROCK prevents the formation of new protrusions by stabilizing actin formation. These processes are crucial to the maturation process, slowing the de novo generation of new spines. The RhoA/ROCK also influences plasticity processes, and selective modulation by ROCK1 of MLC-dependent actin dynamics leads to neurite retraction, but not to spine retraction. ROCK1 is also responsible for the reduction of the readily releasable pool of synaptic vesicles. These and other evidences suggest that ROCK1 is the main isoform acting on the presynaptic neuron. On the other hand, ROCK2 seems to have broad effects on LIMK/cofilin-dependent plasticity processes such as cofilin-dependent PSD changes. The RhoA/ROCK pathway is an important factor in several different brain-related pathologies via both downstream and upstream pathways. In the aggregate, these evidences show that the RhoA/ROCK pathway has a central role in the etiopathogenesis of a large group of CNS diseases, which underscores the importance of the pharmacological modulation of RhoA/ROCK as an important pathway to drug discovery in the neurodegenerative disease area. This article aims at providing the first review of the role of compounds acting on the RhoA/ROCK pathway in the control of synaptic disfunction.

High density bioprocessing of human pluripotent stem cells by metabolic control and in silico modeling

To harness the full potential of human pluripotent stem cells (hPSCs) we combined instrumented stirred tank bioreactor (STBR) technology with the power of in silico process modeling to overcome substantial, hPSC‐specific hurdles toward their mass production. Perfused suspension culture (3D) of matrix‐free hPSC aggregates in STBRs was applied to identify and control process‐limiting parameters including pH, dissolved oxygen, glucose and lactate levels, and the obviation of osmolality peaks provoked by high density culture. Media supplements promoted single cell‐based process inoculation and hydrodynamic aggregate size control. Wet lab‐derived process characteristics enabled predictive in silico modeling as a new rational for hPSC cultivation. Consequently, hPSC line‐independent maintenance of exponential cell proliferation was achieved. The strategy yielded 70‐fold cell expansion in 7 days achieving an unmatched density of 35 × 10⁶ cells/mL equivalent to 5.25 billion hPSC in 150 mL scale while pluripotency, differentiation potential, and karyotype stability was maintained. In parallel, media requirements were reduced by 75% demonstrating the outstanding increase in efficiency. Minimal input to our in silico model accurately predicts all main process parameters; combined with calculation‐controlled hPSC aggregation kinetics, linear process upscaling is also enabled and demonstrated for up to 500 mL scale in an independent bioreactor system. Thus, by merging applied stem cell research with recent knowhow from industrial cell fermentation, a new level of hPSC bioprocessing is revealed fueling their automated production for industrial and therapeutic applications.

The Regulation of Intestinal Mucosal Barrier by Myosin Light Chain Kinase/Rho Kinases

The intestinal epithelial apical junctional complex, which includes tight and adherens junctions, contributes to the intestinal barrier function via their role in regulating paracellular permeability. Myosin light chain II (MLC-2), has been shown to be a critical regulatory protein in altering paracellular permeability during gastrointestinal disorders. Previous studies have demonstrated that phosphorylation of MLC-2 is a biochemical marker for perijunctional actomyosin ring contraction, which increases paracellular permeability by regulating the apical junctional complex. The phosphorylation of MLC-2 is dominantly regulated by myosin light chain kinase- (MLCK-) and Rho-associated coiled-coil containing protein kinase- (ROCK-) mediated pathways. In this review, we aim to summarize the current state of knowledge regarding the role of MLCK- and ROCK-mediated pathways in the regulation of the intestinal barrier during normal homeostasis and digestive diseases. Additionally, we will also suggest potential therapeutic targeting of MLCK- and ROCK-associated pathways in gastrointestinal disorders that compromise the intestinal barrier.

The Rho-associated kinase inhibitor fasudil can replace Y-27632 for use in human pluripotent stem cell research

Poor survival of human pluripotent stem cells (hPSCs) following freezing, thawing, or passaging hinders the maintenance and differentiation of stem cells. Rho-associated kinases (ROCKs) play a crucial role in hPSC survival. To date, a typical ROCK inhibitor, Y-27632, has been the primary agent used in hPSC research. Here, we report that another ROCK inhibitor, fasudil, can be used as an alternative and is cheaper than Y-27632. It increased hPSC growth following thawing and passaging, like Y-27632, and did not affect pluripotency, differentiation ability, and chromosome integrity. Furthermore, fasudil promoted retinal pigment epithelium (RPE) differentiation and the survival of neural crest cells (NCCs) during differentiation. It was also useful for single-cell passaging of hPSCs and during aggregation. These findings suggest that fasudil can replace Y-27632 for use in stem research.

Continuous WNT Control Enables Advanced hPSC Cardiac Processing and Prognostic Surface Marker Identification in Chemically Defined Suspension Culture

Aiming at clinical translation, robust directed differentiation of human pluripotent stem cells (hPSCs), preferentially in chemically defined conditions, is a key requirement. Here, feasibility of suspension culture based hPSC-cardiomyocyte (hPSC-CM) production in low-cost, xeno-free media compatible with good manufacturing practice standards is shown. Applying stirred tank bioreactor systems at increasing dimensions, our advanced protocol enables routine production of about 1 million hPSC-CMs/mL, yielding ∼1.3 × 10⁸ CM in 150 mL and ∼4.0 × 10⁸ CMs in 350–500 mL process scale at >90% lineage purity. Process robustness and efficiency is ensured by uninterrupted chemical WNT pathway control at early stages of differentiation and results in the formation of almost exclusively ventricular-like CMs. Modulated WNT pathway regulation also revealed the previously unappreciated role of ROR1/CD13 as superior surrogate markers for predicting cardiac differentiation efficiency as soon as 72 h of differentiation. This monitoring strategy facilitates process upscaling and controlled mass production of hPSC derivatives.

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Chemically defined hPSC cardiac differentiation applicable to stirred tank reactors

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Protocol generates >90% purity of ventricular-like cardiomyocytes

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Uninterrupted WNT pathway control enables superior cardiac mesoderm formation

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Novel ROR1/CD13 combination as superior, predictive marker of cardiomyogenesis

Sensitivity of human pluripotent stem cells to insulin precipitation induced by peristaltic pump-based medium circulation: considerations on process development

Controlled large-scale production of human pluripotent stem cells (hPSCs) is indispensable for their envisioned clinical translation. Aiming at advanced process development in suspension culture, the sensitivity of hPSC media to continuous peristaltic pump-based circulation, a well-established technology extensively used in hydraulically-driven bioreactors, was investigated. Unexpectedly, conditioning of low protein media (i.e. E8 and TeSR-E8) in a peristaltic pump circuit induced severe viability loss of hPSCs cultured as aggregates in suspension. Optical, biochemical, and cytological analyses of the media revealed that the applied circulation mode resulted in the reduction of the growth hormone insulin by precipitation of micro-sized particles. Notably, in contrast to insulin depletion, individual withdrawal of other medium protein components (i.e. bFGF, TGFβ1 or transferrin) provoked minor reduction of hPSC viability, if any. Supplementation of the surfactant glycerol or the use of the insulin analogue Aspart did not overcome the issue of insulin precipitation. In contrast, the presence of bovine or human serum albumin (BSA or HSA, respectively) stabilized insulin rescuing its content, possibly by acting as molecular chaperone-like protein, ultimately supporting hPSC maintenance. This study highlights the potential and the requirement of media optimization for automated hPSC processing and has broad implications on media development and bioreactor-based technologies.

EBIO Does Not Induce Cardiomyogenesis in Human Pluripotent Stem Cells but Modulates Cardiac Subtype Enrichment by Lineage-Selective Survival

Subtype-specific human cardiomyocytes (CMs) are valuable for basic and applied research. Induction of cardiomyogenesis and enrichment of nodal-like CMs was described for mouse pluripotent stem cells (mPSCs) in response to 1-ethyl-2-benzimidazolinone (EBIO), a chemical modulator of small-/intermediate-conductance Ca²⁺-activated potassium channels (SKs 1-4). Investigating EBIO in human pluripotent stem cells (PSCs), we have applied three independent differentiation protocols of low to high cardiomyogenic efficiency. Equivalent to mPSCs, timed EBIO supplementation during hPSC differentiation resulted in dose-dependent enrichment of up to 80% CMs, including an increase in nodal- and atrial-like phenotypes. However, our study revealed extensive EBIO-triggered cell loss favoring cardiac progenitor preservation and, subsequently, CMs with shortened action potentials. Proliferative cells were generally more sensitive to EBIO, presumably via an SK-independent mechanism. Together, EBIO did not promote cardiogenic differentiation of PSCs, opposing previous findings, but triggered lineage-selective survival at a cardiac progenitor stage, which we propose as a pharmacological strategy to modulate CM subtype composition.

Bulk cell density and Wnt/TGFbeta signalling regulate mesendodermal patterning of human pluripotent stem cells

In vitro differentiation of human pluripotent stem cells (hPSCs) recapitulates early aspects of human embryogenesis, but the underlying processes are poorly understood and controlled. Here we show that modulating the bulk cell density (BCD: cell number per culture volume) deterministically alters anteroposterior patterning of primitive streak (PS)-like priming. The BCD in conjunction with the chemical WNT pathway activator CHIR99021 results in distinct paracrine microenvironments codifying hPSCs towards definitive endoderm, precardiac or presomitic mesoderm within the first 24 h of differentiation, respectively. Global gene expression and secretome analysis reveals that TGFß superfamily members, antagonist of Nodal signalling LEFTY1 and CER1, are paracrine determinants restricting PS progression. These data result in a tangible model disclosing how hPSC-released factors deflect CHIR99021-induced lineage commitment over time. By demonstrating a decisive, functional role of the BCD, we show its utility as a method to control lineage-specific differentiation. Furthermore, these findings have profound consequences for inter-experimental comparability, reproducibility, bioprocess optimization and scale-up.

Impact of Feeding Strategies on the Scalable Expansion of Human Pluripotent Stem Cells in Single-Use Stirred Tank Bioreactors

: The routine application of human pluripotent stem cells (hPSCs) and their derivatives in biomedicine and drug discovery will require the constant supply of high-quality cells by defined processes. Culturing hPSCs as cell-only aggregates in (three-dimensional [3D]) suspension has the potential to overcome numerous limitations of conventional surface-adherent (two-dimensional [2D]) cultivation. Utilizing single-use instrumented stirred-tank bioreactors, we showed that perfusion resulted in a more homogeneous culture environment and enabled superior cell densities of 2.85 × 10⁶ cells per milliliter and 47% higher cell yields compared with conventional repeated batch cultures. Flow cytometry, quantitative reverse-transcriptase polymerase chain reaction, and global gene expression analysis revealed a high similarity across 3D suspension and 2D precultures, underscoring that matrix-free hPSC culture efficiently supports maintenance of pluripotency. Interestingly, physiological data and gene expression assessment indicated distinct changes of the cells' energy metabolism, suggesting a culture-induced switch from glycolysis to oxidative phosphorylation in the absence of hPSC differentiation. Our data highlight the plasticity of hPSCs' energy metabolism and provide clear physiological and molecular targets for process monitoring and further development. This study paves the way toward more efficient GMP-compliant cell production and underscores the enormous process development potential of hPSCs in suspension culture.

SIGNIFICANCE

Human pluripotent stem cells (hPSCs) are a unique source for the, in principle, unlimited production of functional human cell types in vitro, which are of high value for therapeutic and industrial applications. This study applied single-use, clinically compliant bioreactor technology to develop advanced, matrix-free, and more efficient culture conditions for the mass production of hPSCs in scalable suspension culture. Using extensive analytical tools to compare established conditions with this novel culture strategy, unexpected physiological features of hPSCs were discovered. These data allow a more rational process development, providing significant progress in the field of translational stem cell research and medicine.

Fast and efficient multitransgenic modification of human pluripotent stem cells

Human pluripotent stem cells (hPSCs) represent a prime cell source for pharmacological research and regenerative therapies because of their extensive expansion potential and their ability to differentiate into essentially all somatic lineages in vitro. Improved methods to stably introduce multiple transgenes into hPSCs will promote, for example, their preclinical testing by facilitating lineage differentiation and purification in vitro and the subsequent in vivo monitoring of respective progenies after their transplantation into relevant animal models. To date, the establishment of stable transgenic hPSC lines is still laborious and time-consuming. Current limitations include the low transfection efficiency of hPSCs via nonviral methods, the inefficient recovery of genetically engineered clones, and the silencing of transgene expression. Here we describe a fast, electroporation-based method for the generation of multitransgenic hPSC lines by overcoming the need for any preadaptation of conventional hPSC cultures to feeder-free conditions before genetic manipulation. We further show that the selection for a single antibiotic resistance marker encoded on one plasmid allowed for the stable genomic (co-)integration of up to two additional, independent expression plasmids. The method thereby enables the straightforward, nonviral generation of valuable multitransgenic hPSC lines in a single step. Practical applicability of the method is demonstrated for antibiotic-based lineage enrichment in vitro and for sodium iodide symporter transgene-based in situ cell imaging after intramyocardial cell infusion into explanted pig hearts.

Induction of pluripotent stem cells from a cynomolgus monkey using a polycistronic simian immunodeficiency virus-based vector, differentiation toward functional cardiomyocytes, and generation of stably expressing reporter lines

Induced pluripotent stem cells (iPSCs) represent a novel cell source for regenerative therapies. Many emerging iPSC-based therapeutic concepts will require preclinical evaluation in suitable large animal models. Among the large animal species frequently used in preclinical efficacy and safety studies, macaques show the highest similarities to humans at physiological, cellular, and molecular levels. We have generated iPSCs from cynomolgus monkeys (Macaca fascicularis) as a segue to regenerative therapy model development in this species. Because typical human immunodeficiency virus type 1 (HIV-1)-based lentiviral vectors show poor transduction of simian cells, a simian immunodeficiency virus (SIV)-based vector was chosen for efficient transduction of cynomolgus skin fibroblasts. A corresponding polycistronic vector with codon-optimized reprogramming factors was constructed for reprogramming. Growth characteristics as well as cell and colony morphology of the resulting cynomolgus iPSCs (cyiPSCs) were demonstrated to be almost identical to cynomolgus embryonic stem cells (cyESCs), and cyiPSCs expressed typical pluripotency markers including OCT4, SOX2, and NANOG. Furthermore, differentiation in vivo and in vitro into derivatives of all three germ layers, as well as generation of functional cardiomyocytes, could be demonstrated. Finally, a highly efficient technique for generation of transgenic cyiPSC clones with stable reporter expression in undifferentiated cells as well as differentiated transgenic cyiPSC progeny was developed to enable cell tracking in recipient animals. In conclusion, our data indicate that cyiPSCs represent a valuable cell source for establishment of macaque-based allogeneic and autologous preclinical cell transplantation models for various fields of regenerative medicine.

Directing cardiomyogenic differentiation of human pluripotent stem cells by plasmid-based transient overexpression of cardiac transcription factors

Cardiomyocytes (CMs) derived from human pluripotent stem cells (hPSCs) possess a high potential for regenerative medicine. Previous publications suggested that viral transduction of a defined set of transcription factors (TFs) known to play pivotal roles in heart development also increases cardiomyogenesis in vitro upon overexpression in mouse or human ES cells. To circumvent issues associated with viral approaches such as insertional mutagenesis, we have established a transient transfection system for straightforward testing of TF combinations. Applying this method, the transfection efficiency and the temporal pattern of transgene expression were extensively assessed in hPSCs by quantitative real time-polymerase chain reaction (qRT-PCR), TF-specific immunofluorescence analysis, and flow cytometry. Testing TF combinations in our approach revealed that BAF60C, GATA4, and MESP1 (BGM) were most effective for cardiac forward programming in human induced pluripotent stem cell lines and human ES cells as well. Removal of BAF60C slightly diminished formation of CM-like cells, whereas depletion of GATA4 or MESP1 abolished cardiomyogenesis. Each of these TFs alone had no inductive effect. In addition, we have noted sensitivity of CM formation to cell density effects, which highlights the necessity for cautious analysis when interpreting TF-directed lineage induction. In summary, this is the first report on TF-induced cardiomyogenesis of hPSCs applying a transient, nonintegrating method of cell transfection.

The use of agarose microwells for scalable embryoid body formation and cardiac differentiation of human and murine pluripotent stem cells

In most pluripotent stem cell differentiation protocols the formation of embryoid bodies (EBs) is an important step. Here we describe a rapid, straightforward soft lithography approach for the preparation of hydrophilic silicon masters from different templates and the subsequent production of patterned agarose-DMEM microwell surfaces for scalable well standardized stem cell aggregation and EB formation. The non-adhesive agarose microwell plates represent an accurate replication of the templates' topography and were used for aggregation of murine induced pluripotent stem cells (iPSCs) and human embryonic stem cells (ESCs). Direct microscopic assessment by time-lapse analysis demonstrated rapid formation of uniformly shaped EBs from murine iPSCs with similar or even more consistent results concerning size distribution and harvesting efficiency compared to the commonly used but time-consuming hanging drop technique. For human ESCs, homogenous aggregates were obtained after single cell inoculation on agarose microwells with efficient differentiation into the cardiac lineage using state-of-the-art protocols for directed differentiation via small molecules. With this soft lithography-based strategy, sufficient and reproducible numbers of stem cell-derived cardiomyocytes necessary for tissue engineering purposes can be realized in a highly controllable manner. Moreover, it might be useful for different cell types in any application that requires scalable and highly standardized aggregation.

Suspension culture of human pluripotent stem cells in controlled, stirred bioreactors

Therapeutic and industrial applications of pluripotent stem cells and their derivatives require large cell quantities generated in defined conditions. To this end, we have translated single cell-inoculated suspension cultures of human pluripotent stem cells (hPSCs; including human induced pluripotent stem cells [hiPS] and human embryonic stem cells [hESC]) to stirred tank bioreactors. These systems that are widely used in biopharmaceutical industry allow straightforward scale up and detailed online monitoring of key process parameters. To ensure minimum medium consumption, but in parallel functional integration of all probes mandatory for process monitoring, that is, for pO₂ and pH, experiments were performed in 100 mL culture volume in a "mini reactor platform" consisting of four independently controlled vessels. By establishing defined parameters for tightly controlled cell inoculation and aggregate formation up to 2×10⁸ hiPSCs/100 mL were generated in a single process run in 7 days. Expression of pluripotency markers and ability of cells to differentiate into derivates of all three germ layers in vitro was maintained, underlining practical utility of this new process. The presented data provide key steps toward scalable mass expansion of human iPS and ES cells thereby enabling translation of stem cell research to (pre)clinical application in relevant large animal models and valuable in vitro assays for drug development and validation as well.