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Artificial skin models have emerged as valuable tools for evaluating cosmetic ingredients and developing treatments for skin regeneration. Among them,3D skin equivalent models (SKEs) using human primary skin cells are widely utilized and supported by standardized testing guidelines. However,primary cells face limitations such as restricted donor availability and challenges in conducting genotype-specific studies. To overcome these issues,recent approaches have focused on differentiating skin cells from human-induced pluripotent stem cells (hiPSCs). In this study,we developed a protocol to differentiate high-purity skin cells,such as fibroblasts (hFIBROs) and keratinocytes (hKERAs),from hiPSCs. To construct the hiPSC-derived SKE (hiPSC-SKE),a dermis was first formed by culturing a collagen and hFIBROs mixture within an insert. Subsequently,hKERAs were seeded onto the dermis,and keratinization was induced under air-liquid culture conditions to establish an epidermis. Histological analysis with hematoxylin and eosin staining confirmed that the hiPSC-SKE recapitulated the layered architecture of native human skin and expressed appropriate epidermal and dermal markers. Moreover,exposure to Triton X-100,a known skin irritant,led to marked epidermal damage and significantly reduced cell viability,validating the model’s functional responsiveness. These findings indicate that the hiPSC-SKE model represents a promising alternative for various skin-related applications,including the replacement of animal testing. View Publication

Succinic Semialdehyde Dehydrogenase Deficiency (SSADHD) is an ultra-rare autosomal recessive neurometabolic disorder caused by ALDH5A1 mutations presenting with autism and epilepsy. Here,we report the generation and characterization of human induced pluripotent stem cells (hiPSCs) derived from fibroblasts of three unrelated SSADHD patients – one female and two males with the CRISPR-corrected isogenic controls. These individuals are clinically diagnosed and are being followed in a longitudinal clinical study. View Publication

Leigh syndrome French Canadian type (LSFC) is a recessive neurodegenerative disease characterized by tissue-specific deficiency in cytochrome c oxidase (COX),the fourth complex in the oxidative phosphorylation system. LSFC is caused by mutations in the leucine rich pentatricopeptide repeat containing gene ( LRPPRC ). Most LSFC patients in Quebec are homozygous for an A354V substitution that causes a decrease in the expression of the LRPPRC protein. While LRPPRC is ubiquitously expressed and is involved in multiple cellular functions,tissue-specific expression of LRPPRC and COX activity is correlated with clinical features. In this proof-of-principle study,we developed human induced pluripotent stem cell (hiPSC)-based models from fibroblasts taken from a patient with LSFC,homozygous for the LRPPRC *354V allele,and from a control,homozygous for the LRPPRC *A354 allele. Specifically,for both of these fibroblast lines we generated hiPSC,hiPSC-derived cardiomyocytes (hiPSC-CMs) and hepatocyte-like cell (hiPSC-HLCs) lines,as well as the three germ layers. We observed that LRPPRC protein expression is reduced in all cell lines/layers derived from LSFC patient compared to control cells,with a reduction ranging from ∼70% in hiPSC-CMs to undetectable levels in hiPSC-HLC,reflecting tissue heterogeneity observed in patient tissues. We next performed exploratory analyses of these cell lines and observed that COX protein expression was reduced in all cell lines derived from LSFC patient compared to control cells. We also observed that mutant LRPPRC was associated with altered expression of key markers of endoplasmic reticulum stress response in hiPSC-HLCs but not in other cell types that were tested. While this demonstrates feasibility of the approach to experimentally study genotype-based differences that have tissue-specific impacts,this study will need to be extended to a larger number of patients and controls to not only validate the current observations but also to delve more deeply in the pathogenic mechanisms of LSFC. View Publication

Alzheimer’s disease (AD) is characterized by the accumulation and spread of Tau intraneuronal inclusions throughout most of the telencephalon,leaving hindbrain regions like the cerebellum and spinal cord largely spared. These neuropathological observations,along with the identification of specific vulnerable sub-populations from AD brain-derived single nuclei transcriptomics,suggest that a subset of brain regions and neuronal subtypes possess a selective vulnerability to Tau pathology. Given the inability to culture neurons from patient brains,a disease-relevant in vitro model which recapitulates these features would serve as a critical tool to validate modulators of vulnerability and resilience. Using our recently established platform for inducing endogenous Tau aggregation in human induced pluripotent stem cell (hiPSC)-derived cortical excitatory neurons via application of AD brain-derived exogenous Tau aggregates,we explored whether Tau aggregates preferentially induce aggregation in specific neuronal subtypes. We compared Tau seeding in hiPSC-derived neuron subtypes representing regional identities across the forebrain,midbrain,and hindbrain. Higher susceptibility (i.e. more Tau aggregation) was consistently observed among cortical neuron subtypes,with CTIP2-positive,somatostatin (SST)-positive cortical inhibitory neurons showing the greatest aggregation levels across hiPSC lines from multiple donors. hiPSC-neurons also delineated between the disease-specific vulnerabilities of different protein aggregates,as α-synuclein preformed fibrils showed an increased propensity to induce aggregates in midbrain dopaminergic (mDA)-like neurons,mimicking Parkinson’s disease (PD)-specific susceptibility. Aggregate uptake and degradation rates were insufficient to explain differential susceptibility. The absence of a consistent transcriptional response following aggregate seeding further indicated that intrinsic neuronal subtype-specific properties could drive susceptibility. The present data provides evidence that hiPSC-neurons exhibit features of selective neuronal vulnerability which manifest in a cell autonomous manner,suggesting that mining intrinsic (or basal) transcriptomic signatures of more vulnerable compared to more resilient hiPSC-neurons could uncover the molecular underpinnings of differential susceptibility to protein aggregation found in a variety of neurodegenerative diseases. The online version contains supplementary material available at 10.1186/s40478-025-02000-4. View Publication

The ε4 isoform of apolipoprotein E (ApoE) is the most significant genetic risk factor for Alzheimer’s disease. Glial cells are the main source of ApoE in the brain,and in microglia,the ε4 isoform of ApoE has been shown to impair mitochondrial metabolism and the uptake of lipids and Aβ42. However,whether the ε4 isoform alters autophagy or lysosomal activity in microglia in basal and inflammatory conditions is unknown. Altogether,microglia-like cells (iMGs) from eight APOE 3/3 and six APOE 4/4 human induced pluripotent stem cell (iPSC) lines were used in this study. The responses of iMGs to Aβ42,LPS and IFNγ were studied by metabolomics,proteomics,and functional assays. Here,we demonstrate that iMGs with the APOE 4/4 genotype exhibit reduced basal pinocytosis levels compared to APOE 3/3 iMGs. Inflammatory stimulation with a combination of LPS and IFNγ or Aβ42 induced PI3K/AKT/mTORC signaling pathway,increased pinocytosis,and blocked autophagic flux,leading to the accumulation of sequestosome 1 (p62) in both APOE 4/4 and APOE 3/3 iMGs. Exposure to Aβ42 furthermore caused lysosomal membrane permeabilization,which was significantly stronger in APOE 4/4 iMGs and positively correlated with the secretion of the proinflammatory chemokine IL-8. Metabolomics analysis indicated a dysregulation in amino acid metabolism,primarily L-glutamine,in APOE 4/4 iMGs. Overall,our results suggest that inflammation-induced metabolic reprogramming places lysosomes under substantial stress. Lysosomal stress is more detrimental in APOE 4/4 microglia,which exhibit endo-lysosomal defects. The online version contains supplementary material available at 10.1186/s12974-025-03470-y. View Publication

We used high-resolution optical mapping (~50 µm) to investigate potential arrhythmia mechanisms following transplantation of engineered cardiac tissue. We induced myocardial infarction in 6 immunosuppressed pigs and implanted cardiac spheroids into the border zone. One week later,600-µm-thick cardiac slices containing implanted spheroids were harvested and electrical propagation was imaged. Histology showed low connexin-43 expression,scar,and misaligned muscle fibers at the graft-host interface. We observed propagation from host-to-graft in 10 slices from 3 pigs. Host-graft electrical bridges were spaced by millimeters. Propagation was ~4-fold slower in the graft than host. One graft beat spontaneously,but activation did not propagate from graft-to-host in this,or any other slice. We did not observe reentry,but slow in-graft conduction and sparse electrical bridges provided opportunity for reentry induction. These data reveal potential for reentrant or focal arrhythmias 1 week post-implant,which may resolve with maturation of the graft and the graft-host interface. View Publication

Neuronal differentiation requires extensive metabolic remodeling to support increased energetic and biosynthetic demands. Here,we present an integrated multi-omics and functional characterization of metabolic transitions during early differentiation of human induced pluripotent stem cells (iPSCs) into excitatory cortical neurons using doxycycline-inducible overexpression of neurogenin-2 (NGN2). We analyzed parental iPSCs and induced neurons (iNs) at days 7 and 14 of differentiation,integrating gene expression profiling,label-free quantitative proteomics,high-resolution respirometry,fluorescence lifetime imaging microscopy (FLIM),and 13C₆-glucose metabolic flux analysis. Our data reveal progressive metabolic remodeling associated with neuronal maturation,including enhanced oxidative phosphorylation,increased mitochondrial content,and respiratory capacity. Proteomic analyses showed upregulation of mitochondrial and antioxidant pathways,while FLIM indicated a progressive increase in enzyme-bound NAD(P)H,consistent with a shift toward oxidative metabolism. Notably,13C₆-glucose tracing revealed delayed labeling of the intracellular pool of fully labeled glucose and tricarboxylic acid cycle metabolites,together with enhanced labeling of pentose phosphate pathway intermediates and glutathione in iNs,indicating a shift toward biosynthetic and antioxidant glucose utilization during differentiation. Despite this enhancement in mitochondrial function,differentiated neurons maintained glycolytic activity,suggesting metabolic flexibility. Our results define the first week of differentiation as a critical window of metabolic specialization and establish NGN2-iPSC-derived cortical neurons as a versatile and well-characterized model system for investigating bioenergetic remodeling during early human neurodevelopment. It provides a robust foundation for mechanistic insights and high-throughput evaluation of metabolic pathways relevant to human disease. View Publication