Pluripotent Stem Cells Research Articles

Emerging models of human and non-human primate placental development - Centre for Trophoblast Research 17th annual meeting 2024.

The 17th annual meeting of the Centre for Trophoblast Research (CTR) took place at the University of Cambridge, UK, on 1-2 July 2024. This year's meeting provided an opportunity to reflect on the significant advancements made recently in modelling the human placenta in vitro. The meeting featured 12 invited speakers and attracted 260 participants from 25 countries. Many of the speakers were leading figures who have developed methods to derive human trophoblast stem cells or organoids from first trimester and term placentas, and from pluripotent stem cells. Accompanying the invited presentations were flash talks selected from the abstract submissions and poster presentations. The meeting concluded with a stimulating panel discussion to evaluate the current human trophoblast models. This Meeting Review aims to capture the spirit of the event and highlight the key themes and take-home messages that emerged.

Reprogramming of iPSCs to NPCEC-like cells by biomimetic scaffolds for zonular fiber reconstruction

Ectopia lentis (EL), characterised by impaired zonular fibers originating from non-pigmented ciliary epithelial cells (NPCEC), presents formidable surgical complexities and potential risks of visual impairment. Cataract surgery is the only treatment method for EL, but it leads to the loss of accommodative power of the lens post-operatively. Furthermore, the challenge of repairing zonular ligaments in situ remains a significant global issue. Ocular tissue and aqueous humour samples from patients with EL were subjected to RNA sequencing and Olink high-throughput proteomic analysis, revealing the downregulation of pathogenic genes (FBN1, MFAP2) and upregulation of secretory proteins (IL-12, MMP-1). The high expression of FBN1 and MFAP2 in NPCECs suggests their potential as candidates for zonular fiber construction; however, the limited availability of donor sources restricts the feasibility of NPCEC transplantation therapy. The reprogramming and directional differentiation of induced pluripotent stem cells (iPSC) to NPCEC was successfully achieved using the developed biomimetic scaffolds that mimic the microstructures of natural radial zonular fibers. Excitingly, the single injection of induced NPCEC-like cells significantly contributed to restoring and enhancing mechanical properties in zonular fiber structures in a rabbit model with EL. This proposed in situ iPSC-based regeneration technique might serve as an innovative therapeutic strategy for clinical EL patients, reduce the cataract surgery rate, and retain the adjustment capacity of inherent lentis.

BRAFV600E induces key features of LCH in iPSCs with cell type-specific phenotypes and drug responses.

Langerhans cell histiocytosis (LCH) is a clonal hematopoietic disorder defined by tumorous lesions containing CD1a+/CD207+ cells. Two severe complications of LCH are systemic hyperinflammation and progressive neurodegeneration. The scarcity of primary samples and lack of appropriate models limit our mechanistic understanding of LCH pathogenesis and affect patient care. We generated a human in vitro model for LCH using induced pluripotent stem cells (iPSCs) harboring the BRAFV600E mutation, the most common genetic driver of LCH. We show that BRAFV600E/WT iPSCs display myelo-monocytic skewing during hematopoiesis and spontaneously differentiate into CD1a+/CD207+ cells that are similar to lesional LCH cells and are derived from a CD14+ progenitor. We show that BRAFV600E modulates the expression of key transcription factors regulating monocytic differentiation and leads to an upregulation of pro-inflammatory molecules and LCH marker genes early during myeloid differentiation. In vitro drug testing revealed that BRAFV600E-induced transcriptomic changes are reverted upon treatment with MAPK-pathway inhibitors (MAPKi). Importantly, MAPKi do not affect myeloid progenitors but reduces only the mature CD14+ cell population. Furthermore, iPSC-derived neurons (iNeurons) co-cultured with BRAFV600E/WT iPSC-derived microglia-like cells (iMGL), differentiated from iPSC-derived CD34+ progenitors, exhibit signs of neurodegeneration with neuronal damage and release of neurofilament light chain. In summary, the iPSC-based model described here provides a platform to investigate the effects of BRAFV600E in different hematopoietic cell types and provides a tool to compare and identify novel approaches for the treatment of BRAFV600E-driven diseases.

Rabbit Heart Bioartificial Tissue: Perfusion Decellularization and Characterization.

Despite new approaches in the treatment of cardiovascular disease (CVD) such as percutaneous coronary intervention, coronary artery bypass graft, and left ventricular assist devices, which cannot fully compensate for the effectiveness of the original heart, heart transplantation still remains as the most effective solution. 
A growing body of literature recognizes the importance of developing a whole heart constructed from living tissues to provide an alternative option for patients suffering from diseases of the cardiovascular system. A potential solution that shows a promise is to generate cell-free, i.e., decellularized, scaffolds using native heart tissue to be later cellularized and transplanted. This study reports the decellularization process and efficiency in an effort to create a whole heart scaffold. The hearts harvested from rabbits were perfused and the final bioartificial scaffolds were characterized for the efficiency of decellularization in terms of DNA content, collagen, and glycosaminoglycan. The compressive biomechanical properties of decellularized and native hearts were also determined and compared. Findings revealed that the DNA content of decellularized hearts was significantly reduced while keeping collagen and GAG content unchanged. Biomechanical properties of the hearth became inferior upon removal of the nuclear material. Decellularized hearts have significant importance in treating CVD as they serve as bioartificial hearts, providing a more clinically relevant model for potential human use.
Future work will focus on the recellularization of the heart using induced pluripotent or embryonic stem cells to test its functionality.

Molecular Mechanisms of Fibrosis in Cholestatic Liver Diseases and Regenerative Medicine-Based Therapies

The aim of this review is to explore the potential of new regenerative medicine approaches in the treatment of cholestatic liver fibrosis. Cholestatic liver diseases, such as primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and biliary atresia (BA), due to the accumulation of bile, often progress to liver fibrosis, cirrhosis, and liver failure. When the disease becomes severe enough to require liver transplantation. Deeply understanding the disease’s progression and fibrosis formation is crucial for better diagnosis and treatment. Current liver fibrosis treatments mainly target the root causes and no direct treatment method in fibrosis itself. Recent advances in regenerative medicine offer a potential approach that may help find the ways to target fibrosis directly, offering hope for improved outcomes. We also summarize, analyze, and discuss the current state and benefits of regenerative medicine therapies such as mesenchymal stem cell (MSC) therapy, induced pluripotent stem cells (iPSCs), and organoid technology, which may help the treatment of cholestatic liver diseases. Focusing on the latest research may reveal new targets and enhance therapeutic efficacy, potentially leading to more effective management and even curative strategies for cholestatic liver diseases.

BMP-9 mediates fibroproliferation in fibrodysplasia ossificans progressiva through TGF-β signaling.

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder presenting with progressive heterotopic ossification (HO) in soft tissues. Early-stage FOP is characterized by recurrent episodes of painful tissue swelling (flare-ups), with numerous proliferation-activated mesenchymal stromal cells (MSCs) subsequently causing HO. However, the mechanisms underlying flare-up progression remain unclear. In this study, we evaluated the proliferation of MSCs obtained from FOP patient-derived induced pluripotent stem cells (FOP-iPSCs) to elucidate the mechanisms underlying flare-ups and found that bone morphogenetic protein (BMP)-9 mediated enhanced proliferation by abnormal activation of transforming growth factor (TGF)-β signaling pathway in MSCs from FOP-iPSCs. In FOP model mice, elevated BMP-9 levels correlated with elevated phosphorylation of SMAD2/3 and increased cellular proliferation in the affected tissues, while systemic BMP-9 neutralization and knockout mitigated flare-ups and HO. Thus, BMP-9 aberrantly transduces TGF-β signaling and induces fibroproliferation, initiating flare-ups. This study provides novel insights into the development of future FOP therapies.

Generation and long-term culture of human cerebellar organoids from pluripotent stem cells.

The advancement of research on human cerebellar development and diseases has been hindered by the lack of a cell-based system that mirrors the cellular diversity and functional characteristics of the human cerebellum. Here, we describe our protocol for a human pluripotent stem cell-derived human cerebellar organoid (hCerO) model, which successfully replicates the cellular diversity of the fetal cerebellum along with some of its distinct cytoarchitectural features. Our approach involves the patterning of human pluripotent stem cells, resulting in the generation of both cerebellar excitatory and inhibitory progenitor populations-specifically, the rhombic lip and ventricular zone progenitors, respectively. This patterning strategy leads to the reproducible differentiation of the major neurons of the cerebellum such as granule cells and Purkinje cells within just one month of culture. hCerOs serve as platforms for molecular, cellular and functional assays, including single-cell transcriptomics, immunohistochemistry and investigations into calcium dynamics and electrophysiological properties. Remarkably, the cultivation of hCerOs for up to 8 months enables the healthy survival and maturation of Purkinje cells, which exhibit molecular and electrophysiological features akin to their in vivo counterparts. Overall, our protocol generates and allows for the long-term culture of all major cell types within the cerebellum. Consequently, this significant advancement provides the developmental neurobiology field with a robust platform for exploring both cerebellar development and diseases within an all-human system. This protocol can be easily implemented by a technician with cell culture experience and takes 1-2 months to complete with an option for extended maturation over the course of several months.

Chitosan-Alginate Hydrogel Enriched with Hypericum perforatum Callus Extract for Improved Wound Healing and Scar Inhibition.

Hypericum perforatum callus contains pluripotent stem cells, and its extract (HPCE) is a natural compound that includes various biologically active components, such as phenolic acids, flavonoids, and naphthodiantrons like hypericin and hyperforin. These components give HPCE significant antibacterial and antioxidant properties, making it a valuable option for wound healing. Unlike traditional wound dressings that may leave a residue or necessitate invasive procedures like phototherapy, HPCE is a promising alternative. This study presents a hydrogel wound dressing made from a chitosan/alginate scaffold loaded with HPCE (CA/HPCE). This system displayed remarkable mechanical properties coupled with a high swelling capacity. Moreover, it demonstrated potent antibacterial, antioxidant, and anti-inflammatory activities, promoting a favorable environment for wound healing. In vitro studies confirmed that our wound dressings effectively inhibited Escherichia coli (E. coli) and drug-resistant bacteria like Klebsiella pneumoniae (K. pneumoniae), methicillin-resistant Staphylococcus aureus (MRSA), and methicillin-resistant coagulase-negative Staphylococcus (MR-CoNS). Additionally, CA/HPCE had the potential to significantly augment fibroblast migration. Moreover, in vivo investigations confirmed that this system accelerated re-epithelialization, neovascularization, and collagen deposition while reducing inflammation. Immunohistochemistry (IHC) analysis of α-smooth muscle actin (α-SMA) indicated the absence of hypertrophic scar formation postdressing. These findings suggest that CA/HPCE is a highly effective and innovative solution for advanced wound care.

Integration and Differentiation of Transplanted Human iPSC-Derived Retinal Ganglion Cell Precursors in Murine Retinas

Optic neuropathy such as glaucoma, stemming from retinal ganglion cell (RGC) degeneration, is a leading cause of visual impairment. Given the substantial loss of RGCs preceding clinical detection of visual impairment, cell replacement therapy emerges as a compelling treatment strategy. Human-induced pluripotent stem cells (hiPSCs) serve as invaluable tools for exploring the developmental processes and pathological mechanisms associated with human RGCs. Utilizing a 3D stepwise differentiation protocol for retinal organoids, we successfully differentiated RGC precursors from hiPSCs harboring a BRN3B-GFP RGC reporter, verified by GFP expression. Intravitreal transplantation of enriched RGC precursors into healthy or N-methyl-D-aspartate (NMDA)-injured mice demonstrated their survival, migration, and integration into the proper retinal layer, the ganglion cell layer, after 3 weeks. Notably, these transplanted cells differentiated into marker-positive RGCs and extended neurites. Moreover, enhanced cell survival was observed with immunosuppressive and anti-inflammatory treatments of the host prior to transplantation. These data underscore the potential of transplanted RGC precursors as a promising therapeutic avenue for treating degenerative retinal diseases resulting from RGC dysfunction.

Unveiling the potential: implications of successful somatic cell-to-ganglion organoid reprogramming.

Organoids have a wide range of potential applications in areas such as organ development, precision medicine, regenerative medicine, drug screening, disease modeling, and gene editing. Currently, most organoids are generated through three-dimensional (3D) in vitro culture of adult stem cells or pluripotent stem cells. However, this method of generating organoids still has several limitations and challenges, including complex manipulations, costly culturing materials, extended time requirements, and certain heterogeneity. Recently, we have found that fibroblasts, when overexpressing several key regulatory transcription factors, are able to directly and rapidly generate two types of ganglion organoids: sensory ganglion (SG) and autonomic ganglion (AG) organoids. They have structures and electrophysiological properties similar to those of endogenous organs in the body. Here, we provide a brief overview of organoid development, focusing on direct reprogramming of SG and AG organoids and their transplantation and regeneration. Finally, the advantages and prospects of direct reprogramming of organoids are discussed.

Molecular characterization and sub-retinal transplantation of hypoimmunogenic human retinal sheets in a minipig model of severe photoreceptor degeneration.

Retinal degenerative diseases affect millions of people worldwide, and legal blindness is generally associated with the loss of cone photoreceptors located in the central region of the retina called the macula. Currently, there is no treatment to replace the macula. Addressing this unmet need, we employed control isogenic and hypoimmunogenic induced pluripotent stem cell lines to generate spontaneously polarized retinal sheets (RSs). RSs were enriched in retinal progenitor and cone precursor cells, which could differentiate into mature S- and M/L-cones in long-term cultures. Single-cell RNA-seq analysis showed that RSs recapitulate the ontogeny of the developing human retina. Isolation of neural rosettes for sub-retinal transplantation effectively eliminated unwanted cells such as RPE cells. In a porcine model of chemically induced retinal degeneration, grafts integrated the host retina and formed a new, yet immature, photoreceptor layer. In one transplanted animal, functional and immunohistochemical assays suggest that grafts exhibited responsiveness to light stimuli and established putative synaptic connections with host bipolar neurons. This study underscores the potential and challenges of RSs for clinical applications.

Patient-derived induced pluripotent stem cells to study non-canonical splicing variants associated with Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most prevalent inherited cardiomyopathy and a leading cause of sudden death. Genetic testing and familial cascade screening play a pivotal role in the clinical management of HCM patients. However, conventional genetic tests primarily focus on the detection of exonic and canonical splice site variation. Oversighting intronic non-canonical splicing variants potentially contributes to a proportion of HCM patients remaining genetically undiagnosed. Here, using a non-integrative reprogramming strategy, we generated induced pluripotent stem cell (iPSC) lines from four individuals carrying one of two variants within intronic regions of MYBPC3: c.1224-52G > A and c.1898-23A > G. Upon differentiation to iPSC-derived cardiomyocytes (iPSC-CMs), mis-spliced mRNAs were identified in cells harbouring these variants. Both abnormal mRNAs contained a premature termination codon (PTC), fitting the criteria for activation of nonsense mediated decay (NMD). However, the c.1898-23A > G transcripts escaped this mRNA quality control mechanism, while the c.1224-52G > A transcripts were degraded. The newly generated iPSC lines represent valuable tools for studying the functional consequences of intronic variation and for translational research aimed at reversing splicing abnormalities to prevent disease progression.

Generation of a human induced pluripotent stem cell line ZZUNEUi030-A from a female patient carrying a heterozygous CALM2 (c.395 A > T) mutation

Calmodulin mutations can cause life-threatening long QT syndrome involving CALM1, CALM2, and CALM3. In this study, human induced pluripotent stem cells ZZUNEUi030-A were derived from a female patient with heterozygous CALM2 gene c. 395A → T by Sendai virus non-integrated reprogramming technology. The cell line showed a normal female karyotype (46, XX), expressed pluripotency markers, and had the ability to differentiate into three germ layers in vitro. ZZUNEUi030-A can be used as a cell disease model to study the pathogenesis of LQT caused by calmodulin mutations.

Generation of a human induced pluripotent stem cell (iPSC) line from a patient with a CDKL5 gene mutation

CDKL5(Cyclin-dependent kinase-like 5) encodes a kinase that may influence components of molecular pathways associated with MeCP2 and regulates axon outgrowth, dendritic morphogenesis, and synapse formation early in life. Here, we report an induced pluripotent stem cell (iPSC) line generated from an epilepsy patient harboring the CDKL5 c.2684C > T (p.P895L) variant. Peripheral blood mononuclear cells from the patient were successfully reprogrammed into iPSCs that expressed pluripotency markers, a normal karyotype, and the capacity to differentiate into the three germ layers in vivo. This iPSC line is a potential resource for studying the pathogenic mechanisms of epilepsy.

The Role of Induced Pluripotent Stem Cells in the Treatment of Stroke.

Stroke is a neurological disorder with high disability and mortality rates. Almost 80% of stroke cases are ischemic stroke, and the remaining are hemorrhagic stroke. The only approved treatment for ischemic stroke is thrombolysis and/or thrombectomy. However, these treatments cannot sufficiently relieve the disease outcome, and many patients remain disabled even after effective thrombolysis. Therefore, rehabilitative therapies are necessary to induce remodeling in the brain. Currently, stem cell transplantation, especially via the use of induced pluripotent stem cells (iPSCs), is considered a promising alternative therapy for stimulating neurogenesis and brain remodeling. iPSCs are generated from somatic cells by specific transcription factors. The biological functions of iPSCs are similar to those of embryonic stem cells (ESCs), including immunomodulation, reduced cerebral blood flow, cerebral edema, and autophagy. Although iPSC therapy plays a promising role in both hemorrhagic and ischemic stroke, its application is associated with certain limitations. Tumor formation, immune rejection, stem cell survival, and migration are some concerns associated with stem cell therapy. Therefore, cell-free therapy as an alternative method can overcome these limitations. This study reviews the therapeutic application of iPSCs in stroke models and the underlying mechanisms and constraints of these cells. Moreover, cell-free therapy using exosomes, apoptotic bodies, and microvesicles as alternative treatments is discussed.

Development of MAPT S305 mutation human iPSC lines exhibiting elevated 4R tau expression and functional alterations in neurons and astrocytes

Due to the importance of 4R tau (with four microtubule-binding-repeat domains) in the pathogenicity of primary tauopathies, it has been challenging to model these diseases in induced pluripotent stem cell (iPSC)-derived neurons, which express very low levels of 4R tau. To address this, we have developed a panel of isogenic iPSC lines carrying MAPT splice-site mutations, S305S, S305I, or S305N, derived from four different donors. All mutations significantly increase 4R tau expression in iPSC neurons and astrocytes. Functional analyses of S305 mutant neurons reveal shared disruption in synaptic signaling and maturity but divergent effects on mitochondrial bioenergetics. In iPSC astrocytes, S305 mutations promote internalization of exogenous tau that may be a precursor to glial pathology. These lines recapitulate previously characterized tauopathy-relevant phenotypes and highlight functional differences between the wild-type 4R and the mutant 4R proteins in both neurons and astrocytes. As such, these lines enable a more complete understanding of pathogenic mechanisms underlying 4R tauopathies across different cell types.

Generation of induced pluripotent stem cell line, NIMHi013-A, from PBMCs of a female child with epilepsy carrying a novel SCN1A variant

The iPSC line NIMHi013-A was generated from peripheral blood mononuclear cells of a paediatric patient with drug resistant epilepsy. The proband was found to have a likely pathogenic missense variant in the SCN1A gene in heterozygous state, which segregated in the affected in dominant fashion. The variant is in the Nav1.1 subunit of the voltage gated sodium ion channel. The iPSCs were generated using Sendai virus-based reprogramming. These iPSCs express pluripotent markers, present a normal karyotype and could differentiate into three germ layers. The iPSC line NIMHi013-A can be used to investigate epileptogenesis in vitro

Modeling metabolic-associated steatohepatitis with human pluripotent stem cell-derived liver organoids.

Metabolic-associated steatohepatitis (MASH) is one of the most prevalent liver diseases worldwide, with a global prevalence estimated between 3% and 5%, posing a significant health burden. Human liver organoids (HLOs) have previously been generated to model steatohepatitis, offering a potential cellular disease model for studying MASH. However, the current HLO model lacks detailed molecular characterizations and requires further improvement. HLOs derived from human pluripotent stem cells were treated with oleic acid and TGFβ to mimic the MASH progression. Treated HLOs were then analyzed using both bulk and single-cell RNA sequencing. Functional characterization was performed through staining with BODIPY, TMRM, CellROX, and Collagen I, as well as terminal deoxynucleotidyl transferase dUTP nick end labeling and ELISA assays. In addition, a test using the MASH HLO model to validate the hepatoprotective effects of several herb extracts was also conducted. Both RNA-seq and single-cell RNA sequencing demonstrated a close resemblance of multiple molecular signatures and key intercellular communications in and between hepatocyte-like cells and stellate-like cells in the MASH HLO model, compared to human MASH. Furthermore, functional characterizations revealed progressive features of human MASH in the MASH HLO model, including severe steatosis, oxidative stress, mitochondrial dysfunction, inflammation, and fibrosis. In addition, the Schisandra extracts have been demonstrated to have significant antioxidative, anti-inflammatory, and antifibrotic properties in the context of MASH. This study offers an improved HLO disease model of human MASH, which can be potentially applied to facilitate the understanding of the MASH pathogenesis and the discovery of effective treatments.

Accumulation of ether phospholipids in induced pluripotent stem cells and oligodendrocyte-lineage cells established from patients with Sjögren-Larsson syndrome.

Sjögren-Larsson syndrome (SLS) is an autosomal recessive leukodystrophy characterized by ichthyosis, intellectual disability, and progressive spastic paralysis caused by biallelic pathogenic variants in the ALDH3A2 gene that encodes the fatty aldehyde dehydrogenase, fatty aldehyde dehydrogenase (FALDH); FALDH catalyzes several metabolic reactions involved in fatty aldehyde oxidation. Only a few studies have been performed to determine the lipid profile of patients with SLS. In a previous postmortem study of the brain of a 65-year-old patient with SLS, lipidomic analysis revealed an accumulation of long-chain unsaturated ether lipid species in the white matter and gray matter. In the present study, we established a disease model using patient-derived neuronal and oligodendrocyte lineage cells to analyze the lipid metabolism and gene expression profiles in SLS. To achieve this, we generated induced pluripotent stem cells (iPSCs) from two patients with the SLS phenotype carrying previously known ALDH3A2 pathogenic variants: One was a compound heterozygote (c.1339A>G:p.(Lys447Glu) and c.57_132dup:p.(Ile45Serfs*34)) and the other was a homozygote (c.1339A>G: p.(Lys447Glu)). The FALDH activity was almost zero in the SLS-iPSC lines established from both patients. Phospholipid analysis of neurospheres, and oligospheres (spheres enriched with oligodendrocyte-lineage cells) derived from the iPSCs by liquid chromatography-mass spectrometry showed accumulation of ether phospholipids in the Sjögren-Larsson patient-derived neurospheres and oligospheres. The results are consistent with the previously reported accumulation of ether lipids in the postmortem brain tissue of an SLS patient. Therefore, iPSCs and iPSC-derived neurospheres and oligospheres established from SLS patients can be useful tools for future pathological analysis of the central nervous system pathophysiology in SLS.

Generation of an iPSC cell line (VANYHHi001-A) from a patient with cardiac arrythmias carrying CACNA1D, SCN5A, and DSP variants

Progressive cardiac conduction defect often associated with variants in sodium voltage-gated channel SCN5A gene and variants in the L-type calcium voltage-gated channel CACNA1D gene are implicated in sinoatrial node dysfunction. We generated an induced pluripotent stem cell line (iPSC) from a 13-year-old patient with history of conduction system disease and ventricular tachycardia, carrying variants in SCN5A (c.2618C > G), CACNA1D (c.3786G > T), and DSP (c.1582C > G). The generated iPSC line exhibited pluripotency markers, differentiated into the three embryonic germ layers, and maintained a normal karyotype. This iPSC line offers insights into the pathophysiological mechanisms of cardiac arrhythmias and personalized therapies development.