Simple, Fast, and Efficient Method for Derivation of Dermal Fibroblasts From Skin Biopsies.

Primary fibroblasts are a precious resource in the field of translational regenerative medicine. Dermal fibroblasts derived from human subject biopsies are being used as donor tissues for the derivation of patient-specific iPSC lines, which in turn are used for disease modeling, drug screening, tissue engineering, and cell transplantation. We developed a fast and simple protocol to grow dermal fibroblasts from skin biopsies. Using this protocol, we simply and firmly fix the biopsy piece on the surface of a tissue culture-treated plate and allow the fibroblasts to grow. This novel method eliminates any need for enzymatic digestion or mechanical dissociation of the biopsy piece. By using this newly developed protocol, we have successfully established around 100 fibroblast lines characterized by the expression of specific markers [Serpin H1 (Hsp-47), F-actin, and Vimentin]. Finally, we have used many of these fibroblast lines as donor tissues to successfully derive iPSC lines. We have developed a method that is simple, fast, convenient, efficient, and gentle on the cells to derive dermal fibroblasts from human skin biopsies. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Skin biopsy collection and fibroblast derivation Support Protocol 1: Culturing, freezing, and thawing dermal fibroblasts derived from a skin biopsy Support Protocol 2: Characterization of dermal fibroblasts by immunocytochemistry.

Sigma non-opioid receptor 1 is a potential therapeutic target for long QT syndrome.

Some missense gain-of-function mutations in CACNA1C gene, encoding calcium channel CaV1.2, cause a life-threatening form of long QT syndrome named Timothy syndrome, with currently no clinically-effective therapeutics. Here we report that pharmacological targeting of sigma non-opioid intracellular receptor 1 (SIGMAR1) can restore electrophysiological function in iPSC-derived cardiomyocytes generated from patients with Timothy syndrome and two common forms of long QT syndrome, type 1 (LQTS1) and 2 (LQTS2), caused by missense trafficking mutations in potassium channels. Electrophysiological recordings demonstrate that an FDA-approved cough suppressant, dextromethorphan, can be used as an agonist of SIGMAR1, to shorten the prolonged action potential in Timothy syndrome cardiomyocytes and human cellular models of LQTS1 and LQTS2. When tested in vivo, dextromethorphan also normalized the prolonged QT intervals in Timothy syndrome model mice. Overall, our study demonstrates that SIGMAR1 is a potential therapeutic target for Timothy syndrome and possibly other inherited arrhythmias such as LQTS1 and LQTS2.

Efficient Cas9-based Genome Editing Using CRISPR Analysis Webtools in Severe Early-onset-obesity Patient-derived iPSCs.

The CRISPR system is an adaptive defense mechanism used by bacteria and archaea against viruses and plasmids. The discovery of the CRISPR-associated protein Cas9 and its RNA-guided cleavage mechanism marked the beginning of a new era in genomic engineering by enabling the editing of a target region in the genome. Gene-edited cells or mice can be used as models for understanding human diseases. Given its high impact in functional genomic experiments on different model systems, several CRISPR/Cas9 protocols have been generated in the past years. The technique uses a straightforward "cut and stitch" mechanism, but requires an accurate step-by-step design. One of the key points is the use of an efficient programmable guide RNA to increase the rate of success in obtaining gene-specific edited clones. Here, we describe an efficient editing protocol using a ribonucleotide protein (RNP) complex for homology-directed repair (HDR)-based correction of a point mutation in an induced pluripotent stem cell (iPSC) line generated from a 14-year-old patient with severe early-onset obesity carrying a de novo variant of ARNT2. The resulting isogenic iPSC line, named CUIMCi003-A-1, has a normal karyotype, expresses stemness markers, and can be differentiated into progenies from all three germ layers. We provide a detailed workflow for designing a single guide RNA and donor DNA, and for isolating clonal human iPSCs edited with the desired modification. This article also focuses on parameters to consider when selecting reagents for CRISPR/Cas9 gene editing after testing their efficiency with in silico tools. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Design of sgRNAs and PCR primers Basic Protocol 2: Testing the efficiency of sgRNAs Basic Protocol 3: Design of template or donor DNA Basic Protocol 4: Targeted gene editing Basic Protocol 5: Selection of positive clones Basic Protocol 6: Freezing, thawing, and expansion of cells Basic Protocol 7: Characterization of edited cell lines.

Fibroblast growth factor homologous factors serve as a molecular rheostat in tuning arrhythmogenic cardiac late sodium current.

Voltage-gated sodium (Nav1.5) channels support the genesis and brisk spatial propagation of action potentials in the heart. Disruption of NaV1.5 inactivation results in a small persistent Na influx known as late Na current (I Na,L), which has emerged as a common pathogenic mechanism in both congenital and acquired cardiac arrhythmogenic syndromes. Here, using low-noise multi-channel recordings in heterologous systems, LQTS3 patient-derived iPSCs cardiomyocytes, and mouse ventricular myocytes, we demonstrate that the intracellular fibroblast growth factor homologous factors (FHF1-4) tune pathogenic I Na,L in an isoform-specific manner. This scheme suggests a complex orchestration of I Na,L in cardiomyocytes that may contribute to variable disease expressivity of NaV1.5 channelopathies. We further leverage these observations to engineer a peptide-inhibitor of I Na,L with a higher efficacy as compared to a well-established small-molecule inhibitor. Overall, these findings lend insights into molecular mechanisms underlying FHF regulation of I Na,L in pathophysiology and outline potential therapeutic avenues.

Derivation and characterization of the induced pluripotent stem cell line CUIMCi004-A from a patient with a novel frameshift variant in exon 18a of OCRL.

OCRL encodes for an inositol polyphosphate 5-phosphatase, located in the trans-Golgi network, endosomes, endocytic clathrin-coated pits, primary cilia. Mutations in OCRL causes Lowe syndrome (LS), a rare and complex disorder characterized by congenital cataracts, renal tubular dysfunction, and mental retardation. Here we generated an induced pluripotent stem cell (iPSC) line from Peripheral Blood Mononuclear Cell (PBMCs) of a 5-year-old boy with severe obesity carrying a novel pathogenic variant in the brain-expressed isoform of OCRL. The Sendai virus approach was used for reprogramming. The iPSC line CUIMCi004-A may serve as a useful resource to further investigate the tissue-specific function of OCRL.

Mesoangioblasts at 20: From the embryonic aorta to the patient bed.

In 2002 we published an article describing a population of vessel-associated progenitors that we termed mesoangioblasts (MABs). During the past decade evidence had accumulated that during muscle development and regeneration things may be more complex than a simple sequence of binary choices (e.g., dorsal vs. ventral somite). LacZ expressing fibroblasts could fuse with unlabelled myoblasts but not among themselves or with other cell types. Bone marrow derived, circulating progenitors were able to participate in muscle regeneration, though in very small percentage. Searching for the embryonic origin of these progenitors, we identified them as originating at least in part from the embryonic aorta and, at later stages, from the microvasculature of skeletal muscle. While continuing to investigate origin and fate of MABs, the fact that they could be expanded in vitro (also from human muscle) and cross the vessel wall, suggested a protocol for the cell therapy of muscular dystrophies. We tested this protocol in mice and dogs before proceeding to the first clinical trial on Duchenne Muscular Dystrophy patients that showed safety but minimal efficacy. In the last years, we have worked to overcome the problem of low engraftment and tried to understand their role as auxiliary myogenic progenitors during development and regeneration.

Generation of the iPSC line CUIMCi003-A derived from a patient with severe early onset obesity.

Aryl hydrocarbon receptor nuclear translocator 2 (ARNT2) is a basic helix-loop-helix (bHLH/PAS) transcription factor involved in the development of paraventricular nucleus of the hypothalamus (PVH) through the heterodimerization with Single-minded 1 (SIM1) (Michaud et al., 2000). Using a Sendai virus-based approach, the four reprogramming factors OCT3/4, SOX2, KLF4 and C-MYC were delivered into Peripheral Blood Mononuclear Cell (PBMCs) from a 14-year-old girl with early onset obesity carrying a de novo variant (p.P130A) in ARNT2. The resulting iPSC line CUIMCi003-A had a normal karyotype, showed pluripotency and three germ layer differentiation capacity in vitro and was heterozygous for the de novo ARNT2 variant.

Establishment and characterization of two iPSC lines derived from healthy controls.

We have generated two iPSC lines from skin biopsies of two healthy individuals. Skin fibroblasts were derived and reprogrammed using a Sendai virus-based approach. The resulting iPSC lines have normal karyotype, express stemness markers and can generate endoderm, mesoderm and ectoderm in vitro. These iPSC lines can be used as healthy controls in differentiation paradigms as well as backbone for gene editing experiments.

Author Correction: Advanced maturation of human cardiac tissue grown from pluripotent stem cells.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

Cardiomyocytes Derived from Human CardiopoieticAmniotic Fluids.

Human amniotic fluid (hAF) cells share characteristics of both embryonic and adult stem cells. They proliferate rapidly and can differentiate into cells of all embryonic germ layers but do not form teratomas. Embryoid-bodies obtained from hAF have cardiac differentiation potential, but terminal differentiation to cardiomyocytes (CMs) has not yet been described. Our purpose was to promote cardiac differentiation in hAFcells. Cells were exposed to inducing factors for up to 15 days. Only the subset of hAF cells expressing the multipotency markers SSEA4, OCT4 and CD90 (CardiopoieticAF cells) responded to the differentiation process by increasing the expression of the cardiac transcription factors Nkx2.5 and GATA4, sarcomeric proteins (cTnT, α-MHC, α-SA), Connexin43 and atrial and ventricular markers. Furthermore, differentiated cells were positive for the calcium pumps CACNA1C and SERCA2a, with approximately 30% of CardiopoieticAF-derived CM-like cells responding to caffeine or adrenergic stimulation. Some spontaneous rare beating foci were also observed. In conclusion, we demonstrated that CardiopoieticAF cells might differentiate toward the cardiac lineage giving rise to CM-like cells characterized by several cardiac-specific molecular, structural, and functional properties.

Advanced maturation of human cardiac tissue grown from pluripotent stem cells.

Cardiac tissues generated from human induced pluripotent stem cells (iPSCs) can serve as platforms for patient-specific studies of physiology and disease1-6. However, the predictive power of these models is presently limited by the immature state of the cells1, 2, 5, 6. Here we show that this fundamental limitation can be overcome if cardiac tissues are formed from early-stage iPSC-derived cardiomyocytes soon after the initiation of spontaneous contractions and are subjected to physical conditioning with increasing intensity over time. After only four weeks of culture, for all iPSC lines studied, such tissues displayed adult-like gene expression profiles, remarkably organized ultrastructure, physiological sarcomere length (2.2 µm) and density of mitochondria (30%), the presence of transverse tubules, oxidative metabolism, a positive force-frequency relationship and functional calcium handling. Electromechanical properties developed more slowly and did not achieve the stage of maturity seen in adult human myocardium. Tissue maturity was necessary for achieving physiological responses to isoproterenol and recapitulating pathological hypertrophy, supporting the utility of this tissue model for studies of cardiac development and disease.

"The state of the heart": Recent advances in engineering human cardiac tissue from pluripotent stem cells.

The pressing need for effective cell therapy for the heart has led to the investigation of suitable cell sources for tissue replacement. In recent years, human pluripotent stem cell research expanded tremendously, in particular since the derivation of human-induced pluripotent stem cells. In parallel, bioengineering technologies have led to novel approaches for in vitro cell culture. The combination of these two fields holds potential for in vitro generation of high-fidelity heart tissue, both for basic research and for therapeutic applications. However, this new multidisciplinary science is still at an early stage. Many questions need to be answered and improvements need to be made before clinical applications become a reality. Here we discuss the current status of human stem cell differentiation into cardiomyocytes and the combined use of bioengineering approaches for cardiac tissue formation and maturation in developmental studies, disease modeling, drug testing, and regenerative medicine.

Sources for skeletal muscle repair: from satellite cells to reprogramming.

Skeletal muscle regeneration is the process that ensures tissue repair after damage by injury or in degenerative diseases such as muscular dystrophy. Satellite cells, the adult skeletal muscle progenitor cells, are commonly considered to be the main cell type involved in skeletal muscle regeneration. Their mechanism of action in this process is extensively characterized. However, evidence accumulated in the last decade suggests that other cell types may participate in skeletal muscle regeneration. Although their actual contribution to muscle formation and regeneration is still not clear; if properly manipulated, these cells may become new suitable and powerful sources for cell therapy of skeletal muscle degenerative diseases. Mesoangioblasts, vessel associated stem/progenitor cells with high proliferative, migratory and myogenic potential, are very good candidates for clinical applications and are already in clinical experimentation. In addition, pluripotent stem cells are very promising sources for regeneration of most tissues, including skeletal muscle. Conditions such as muscle cachexia or aging that severely alter homeostasis may be counteracted by transplantation of donor and/or recruitment and activation of resident muscle stem/progenitor cells. Advantages and limitations of different cell therapy approaches will be discussed.

Microfluidic bioreactor for dynamic regulation of early mesodermal commitment in human pluripotent stem cells.

During development and regeneration, tissues emerge from coordinated sequences of stem cell renewal, specialization and assembly that are orchestrated by cascades of regulatory signals. The complex and dynamic in vivo milieu cannot be replicated using standard in vitro techniques. Microscale technologies now offer potential for conducting highly controllable and sophisticated experiments at biologically relevant scales, with real-time insights into cellular responses. We developed a microbioreactor providing time sequences of space-resolved gradients of multiple molecular factors in three-dimensional (3D) cell culture settings, along with a versatile, high-throughput operation and imaging compatibility. A single microbioreactor yields up to 120 data points, corresponding to 15 replicates of a gradient with 8 concentration levels. Embryoid bodies (EBs) obtained from human embryonic and induced pluripotent stem cells (hESC, hiPSC) were exposed to concentration gradients of Wnt3a, Activin A, BMP4 and their inhibitors, to get new insights into the early-stage fate specification and mesodermal lineage commitment. We were able to evaluate the initiation of mesodermal induction by measuring and correlating the gene expression profiles to the concentration gradients of mesoderm-inducing morphogens. We propose that the microbioreactor systems combining spatial and temporal gradients of molecular and physical factors to hESC and hiPSC cultures can form a basis for predictable in vitro models of development and disease.

Regulation of myotube formation by the actin-binding factor drebrin.

BACKGROUND: Myogenic differentiation involves cell-cycle arrest, activation of the muscle-specific transcriptome, and elongation, alignment and fusion of myoblasts into multinucleated myotubes. This process is controlled by promyogenic transcription factors and regulated by signaling pathways in response to extracellular cues. The p38 mitogen-activated protein kinase (p38 MAPK) pathway promotes the activity of several such transcription factors, including MyoD and MEF2, thereby controlling the muscle-specific transcription program. However, few p38-regulated genes that play a role in the regulation of myogenesis have been identified. METHODS: RNA interference (RNAi), chemical inhibition and immunofluorescence approaches were used to assess the role of drebrin in differentiation of primary mouse myoblasts and C2C12 cells. RESULTS: In a search for p38-regulated genes that promote myogenic differentiation, we identified Dbn1, which encodes the actin-binding protein drebrin. Drebrin is an F-actin side-binding protein that remodels actin to facilitate the change of filopodia into dendritic spines during synaptogenesis in developing neurons. Dbn1 mRNA and protein are induced during differentiation of primary mouse and C2C12 myoblasts, and induction is substantially reduced by the p38 MAPK inhibitor SB203580. Primary myoblasts and C2C12 cells depleted of drebrin by RNAi display reduced levels of myogenin and myosin heavy chain and form multinucleated myotubes very inefficiently. Treatment of myoblasts with BTP2, a small-molecule inhibitor of drebrin, produces a phenotype similar to that produced by knockdown of drebrin, and the inhibitory effects of BTP2 are rescued by expression of a mutant form of drebrin that is unable to bind BTP2. Drebrin in myoblasts is enriched in cellular projections and cell cortices and at regions of cell-cell contact, all sites where F-actin, too, was concentrated. CONCLUSIONS: Our findings reveal that Dbn1 expression is a target of p38 MAPK signaling during myogenesis and that drebrin promotes myoblast differentiation.

Wnt-inhibitory factor 1 dysregulation of the bone marrow niche exhausts hematopoietic stem cells.

The role of Wnt signaling in hematopoietic stem cell fate decisions remains controversial. We elected to dysregulate Wnt signaling from the perspective of the stem cell niche by expressing the pan Wnt inhibitor, Wnt inhibitory factor 1 (Wif1), specifically in osteoblasts. Here we report that osteoblastic Wif1 overexpression disrupts stem cell quiescence, leading to a loss of self-renewal potential. Primitive stem and progenitor populations were more proliferative and elevated in bone marrow and spleen, manifesting an impaired ability to maintain a self-renewing stem cell pool. Exhaustion of the stem cell pool was apparent only in the context of systemic stress by chemotherapy or transplantation of wild-type stem cells into irradiated Wif1 hosts. Paradoxically this is mediated, at least in part, by an autocrine induction of canonical Wnt signaling in stem cells on sequestration of Wnts in the environment. Additional signaling pathways are dysregulated in this model, primarily activated Sonic Hedgehog signaling in stem cells as a result of Wif1-induced osteoblastic expression of Sonic Hedgehog. We find that dysregulation of the stem cell niche by overexpression of an individual component impacts other unanticipated regulatory pathways in a combinatorial manner, ultimately disrupting niche mediated stem cell fate decisions.

Skeletal muscle differentiation of embryonic mesoangioblasts requires pax3 activity.

Mesoangioblasts have been characterized as a population of vessel-associated stem cells able to differentiate into several mesodermal cell types, including skeletal muscle. Here, we report that the paired box transcription factor Pax3 plays a crucial role in directing mouse mesoangioblasts toward skeletal myogenesis in vitro and in vivo. Mesoangioblasts isolated from the aorta of Pax3 null embryos are severely impaired in skeletal muscle differentiation, whereas most other differentiation programs are not affected by the absence of Pax3. Moreover, Pax3(-/-) null mesoangioblasts failed to rescue the myopathic phenotype of the alpha-sarcoglycan mutant mouse. In contrast, mesoangioblasts from Pax3 gain of function, Pax3(PAX3-FKHR/+), mice display enhanced myogenesis in vitro and are more efficient in regenerating new muscle fibers in this model of muscular dystrophy. These data demonstrate that Pax3 is required for the differentiation of mesoangioblast stem cells into skeletal muscle, in keeping with its role in orchestrating entry into the myogenic program.

A highly conserved molecular switch binds MSY-3 to regulate myogenin repression in postnatal muscle.

Myogenin is the dominant transcriptional regulator of embryonic and fetal muscle differentiation and during maturation is profoundly down-regulated. We show that a highly conserved 17-bp DNA cis-acting sequence element located upstream of the myogenin promoter (myogHCE) is essential for postnatal repression of myogenin in transgenic animals. We present multiple lines of evidence supporting the idea that repression is mediated by the Y-box protein MSY-3. Electroporation in vivo shows that myogHCE and MSY-3 are required for postnatal repression. We further show that, in the C2C12 cell culture system, ectopic MSY-3 can repress differentiation, while reduced MSY-3 promotes premature differentiation. MSY-3 binds myogHCE simultaneously with the homeodomain protein Pbx in postnatal innervated muscle. We therefore propose a model in which the myogHCE motif operates as a switch by specifying opposing functions; one that was shown previously is regulated by MyoD and Pbx and it specifies a chromatin opening, gene-activating function at the time myoblasts begin to differentiate; the other includes MYS-3 and Pbx, and it specifies a repression function that operates during and after postnatal muscle maturation in vivo and in myoblasts before they begin to differentiate.