Kimimasa Tobita

Repopulation of decellularized mouse heart with human induced pluripotent stem cell-derived cardiovascular progenitor cells

Heart disease is the leading cause of death in the world. Heart tissue engineering holds a great promise for future heart disease therapy by building personalized heart tissues. Here we create heart constructs by repopulating decellularized mouse hearts with human induced pluripotent stem cell-derived multipotential cardiovascular progenitor cells. We show that the seeded multipotential cardiovascular progenitor cells migrate, proliferate and differentiate in situ into cardiomyocytes, smooth muscle cells and endothelial cells to reconstruct the decellularized hearts. After 20 days of perfusion, the engineered heart tissues exhibit spontaneous contractions, generate mechanical force and are responsive to drugs. In addition, we observe that heart extracellular matrix promoted cardiomyocyte proliferation, differentiation and myofilament formation from the repopulated human multipotential cardiovascular progenitor cells. Our novel strategy to engineer personalized heart constructs could benefit the study of early heart formation or may find application in preclinical testing.

Synthesis, characterization and therapeutic efficacy of a biodegradable, thermoresponsive hydrogel designed for application in chronic infarcted myocardium.

Injection of a bulking material into the ventricular wall has been proposed as a therapy to prevent progressive adverse remodeling due to high wall stresses that develop after myocardial infarction. Our objective was to design, synthesize and characterize a biodegradable, thermoresponsive hydrogel for this application based on copolymerization of N-isopropylacrylamide (NIPAAm), acrylic acid (AAc) and hydroxyethyl methacrylate-poly(trimethylene carbonate) (HEMAPTMC). By evaluating a range of monomer ratios, poly(NIPAAm-co-AAc-co-HEMAPTMC) at a feed ratio of 86/4/10 was shown to be ideal since it formed a hydrogel at 37 degrees C, and gradually became soluble over a 5 month period in vitro through hydrolytic cleavage of the PTMC residues. HEMAPTMC, copolymer and degradation product chemical structures were verified by NMR. No degradation product cytotoxicity was observed in vitro. In a rat chronic infarction model, the infarcted left ventricular (LV) wall was injected with the hydrogel or phosphate buffered saline (PBS). In the PBS group, LV cavity area increased and contractility decreased at 8 wk (p<0.05 versus pre-injection), while in the hydrogel group both parameters were preserved during this period. Tissue ingrowth was observed in the hydrogel injected area and a thicker LV wall and higher capillary density were found for the hydrogel versus PBS group. Smooth muscle cells with contractile phenotype were also identified in the hydrogel injected LV wall. The designed poly(NIPAAm-co-AAc-co-HEMAPTMC) hydrogel of this report may thus offer an attractive biomaterial-centered treatment option for ischemic cardiomyopathy.

Global genetic analysis in mice unveils central role for cilia in congenital heart disease

Congenital heart disease (CHD) is the most prevalent birth defect, affecting nearly 1% of live births; the incidence of CHD is up to tenfold higher in human fetuses. A genetic contribution is strongly suggested by the association of CHD with chromosome abnormalities and high recurrence risk. Here we report findings from a recessive forward genetic screen in fetal mice, showing that cilia and cilia-transduced cell signalling have important roles in the pathogenesis of CHD. The cilium is an evolutionarily conserved organelle projecting from the cell surface with essential roles in diverse cellular processes. Using echocardiography, we ultrasound scanned 87,355 chemically mutagenized C57BL/6J fetal mice and recovered 218 CHD mouse models. Whole-exome sequencing identified 91 recessive CHD mutations in 61 genes. This included 34 cilia-related genes, 16 genes involved in cilia-transduced cell signalling, and 10 genes regulating vesicular trafficking, a pathway important for ciliogenesis and cell signalling. Surprisingly, many CHD genes encoded interacting proteins, suggesting that an interactome protein network may provide a larger genomic context for CHD pathogenesis. These findings provide novel insights into the potential Mendelian genetic contribution to CHD in the fetal population, a segment of the human population not well studied. We note that the pathways identified show overlap with CHD candidate genes recovered in CHD patients, suggesting that they may have relevance to the more complex genetics of CHD overall. These CHD mouse models and >8,000 incidental mutations have been sperm archived, creating a rich public resource for human disease modelling.

Human Pericytes for Ischemic Heart Repair

Human microvascular pericytes (CD146+/34−/45−/56−) contain multipotent precursors and repair/regenerate defective tissues, notably skeletal muscle. However, their ability to repair the ischemic heart remains unknown. We investigated the therapeutic potential of human pericytes, purified from skeletal muscle, for treating ischemic heart disease and mediating associated repair mechanisms in mice. Echocardiography revealed that pericyte transplantation attenuated left ventricular dilatation and significantly improved cardiac contractility, superior to CD56+ myogenic progenitor transplantation, in acutely infarcted mouse hearts. Pericyte treatment substantially reduced myocardial fibrosis and significantly diminished infiltration of host inflammatory cells at the infarct site. Hypoxic pericyte‐conditioned medium suppressed murine fibroblast proliferation and inhibited macrophage proliferation in vitro. High expression by pericytes of immunoregulatory molecules, including interleukin‐6, leukemia inhibitory factor, cyclooxygenase‐2, and heme oxygenase‐1, was sustained under hypoxia, except for monocyte chemotactic protein‐1. Host angiogenesis was significantly increased. Pericytes supported microvascular structures in vivo and formed capillary‐like networks with/without endothelial cells in three‐dimensional cocultures. Under hypoxia, pericytes dramatically increased expression of vascular endothelial growth factor‐A, platelet‐derived growth factor‐β, transforming growth factor‐β1 and corresponding receptors while expression of basic fibroblast growth factor, hepatocyte growth factor, epidermal growth factor, and angiopoietin‐1 was repressed. The capacity of pericytes to differentiate into and/or fuse with cardiac cells was revealed by green fluorescence protein labeling, although to a minor extent. In conclusion, intramyocardial transplantation of purified human pericytes promotes functional and structural recovery, attributable to multiple mechanisms involving paracrine effects and cellular interactions. STEM CELLS2013;31:305–316

DYX1C1 is required for axonemal dynein assembly and ciliary motility

DYX1C1 has been associated with dyslexia and neuronal migration in the developing neocortex. Unexpectedly, we found that deleting exons 2–4 of Dyx1c1 in mice caused a phenotype resembling primary ciliary dyskinesia (PCD), a disorder characterized by chronic airway disease, laterality defects and male infertility. This phenotype was confirmed independently in mice with a Dyx1c1 c.T2A start-codon mutation recovered from an N-ethyl-N-nitrosourea (ENU) mutagenesis screen. Morpholinos targeting dyx1c1 in zebrafish also caused laterality and ciliary motility defects. In humans, we identified recessive loss-of-function DYX1C1 mutations in 12 individuals with PCD. Ultrastructural and immunofluorescence analyses of DYX1C1-mutant motile cilia in mice and humans showed disruptions of outer and inner dynein arms (ODAs and IDAs, respectively). DYX1C1 localizes to the cytoplasm of respiratory epithelial cells, its interactome is enriched for molecular chaperones, and it interacts with the cytoplasmic ODA and IDA assembly factor DNAAF2 (KTU). Thus, we propose that DYX1C1 is a newly identified dynein axonemal assembly factor (DNAAF4).

IFT25 links the signal-dependent movement of Hedgehog components to intraflagellar transport.

The intraflagellar transport (IFT) system is required for building primary cilia, sensory organelles that cells use to respond to their environment. IFT particles are composed of about 20 proteins, and these proteins are highly conserved across ciliated species. IFT25, however, is absent from some ciliated organisms, suggesting that it may have a unique role distinct from ciliogenesis. Here, we generate an Ift25 null mouse and show that IFT25 is not required for ciliary assembly but is required for proper Hedgehog signaling, which in mammals occurs within cilia. Mutant mice die at birth with multiple phenotypes, indicative of Hedgehog signaling dysfunction. Cilia lacking IFT25 have defects in the signal-dependent transport of multiple Hedgehog components including Patched-1, Smoothened, and Gli2, and fail to activate the pathway upon stimulation. Thus, IFT function is not restricted to building cilia where signaling occurs, but also plays a separable role in signal transduction events.

Generating Elastic, Biodegradable Polyurethane/Poly(lactide-co-glycolide) Fibrous Sheets with Controlled Antibiotic Release via Two-Stream Electrospinning

Damage control laparotomy is commonly applied to prevent compartment syndrome following trauma but is associated with new risks to the tissue, including infection. To address the need for biomaterials to improve abdominal laparotomy management, we fabricated an elastic, fibrous composite sheet with two distinct submicrometer fiber populations: biodegradable poly(ester urethane) urea (PEUU) and poly(lactide-co-glycolide) (PLGA), where the PLGA was loaded with the antibiotic tetracycline hydrochloride (PLGA-tet). A two-stream electrospinning setup was developed to create a uniform blend of PEUU and PLGA-tet fibers. Composite sheets were flexible with breaking strains exceeding 200%, tensile strengths of 5-7 MPa, and high suture retention capacity. The blending of PEUU fibers markedly reduced the shrinkage ratio observed for PLGA-tet sheets in buffer from 50% to 15%, while imparting elastomeric properties to the composites. Antibacterial activity was maintained for composite sheets following incubation in buffer for 7 days at 37 degrees C. In vivo studies demonstrated prevention of abscess formation in a contaminated rat abdominal wall model with the implanted material. These results demonstrate the benefits derivable from a two-stream electrospinning approach wherein mechanical and controlled-release properties are contributed by independent fiber populations and the applicability of this composite material to abdominal wall closure.

IFT27 Links the BBSome to IFT for Maintenance of the Ciliary Signaling Compartment

Vertebrate hedgehog signaling is coordinated by the differential localization of the receptors patched-1 and Smoothened in the primary cilium. Cilia assembly is mediated by intraflagellar transport (IFT), and cilia defects disrupt hedgehog signaling, causing many structural birth defects. We generated Ift25 and Ift27 knockout mice and show that they have structural birth defects indicative of hedgehog signaling dysfunction. Surprisingly, ciliary assembly is not affected, but abnormal hedgehog signaling is observed in conjunction with ciliary accumulation of patched-1 and Smoothened. Similarly, Smoothened accumulates in cilia on cells mutated for BBSome components or the BBS binding protein/regulator Lztfl1. Interestingly, the BBSome and Lztfl1 accumulate to high levels in Ift27 mutant cilia. Because Lztfl1 mutant cells accumulate BBSome but not IFT27, it is likely that Lztfl1 functions downstream of IFT27 to couple the BBSome to the IFT particle for coordinated removal of patched-1 and Smoothened from cilia during hedgehog signaling.

Antioxidant levels represent a major determinant in the regenerative capacity of muscle stem cells.

Stem cells are classically defined by their multipotent, long-term proliferation, and self-renewal capabilities. Here, we show that increased antioxidant capacity represents an additional functional characteristic of muscle-derived stem cells (MDSCs). Seeking to understand the superior regenerative capacity of MDSCs compared with myoblasts in cardiac and skeletal muscle transplantation, our group hypothesized that survival of the oxidative and inflammatory stress inherent to transplantation may play an important role. Evidence of increased enzymatic and nonenzymatic antioxidant capacity of MDSCs were observed in terms of higher levels of superoxide dismutase and glutathione, which appears to confer a differentiation and survival advantage. Further when glutathione levels of the MDSCs are lowered to that of myoblasts, the transplantation advantage of MDSCs over myoblasts is lost when transplanted into both skeletal and cardiac muscles. These findings elucidate an important cause for the superior regenerative capacity of MDSCs, and provide functional evidence for the emerging role of antioxidant capacity as a critical property for MDSC survival post-transplantation.

Amelioration of rat cardiac cold ischemia/reperfusion injury with inhaled hydrogen or carbon monoxide, or both

BACKGROUND Recent advances in novel medical gases, including hydrogen and carbon monoxide (CO), have demonstrated significant opportunities for therapeutic use. This study was designed to evaluate the effects of inhaled hydrogen or CO, or both, on cold ischemia/reperfusion (I/R) injury of the myocardium. METHODS Syngeneic heterotopic heart transplantation was performed in rats after 6 or 18 hours of cold ischemia in Celsior solution. Survival, morphology, apoptosis and marker gene expression were assessed in the grafts after in vivo inhalation of hydrogen (1% to 3%), CO (50 to 250 ppm), both or neither. Both donors and recipients were treated for 1 hour before and 1 hour after reperfusion. RESULTS After 6-hour cold ischemia, inhalation of hydrogen (>2%) or CO (250 ppm) alone attenuated myocardial injury. Prolonged cold ischemia for 18 hours resulted in severe myocardial injury, and treatment with hydrogen or CO alone failed to demonstrate significant protection. Dual treatment with hydrogen and CO significantly attenuated I/R graft injury, reducing the infarcted area and decreasing in serum troponin I and creatine phosphokinase (CPK). Hydrogen treatment alone significantly reduced malondialdehyde levels and serum high-mobility group box 1 protein levels as compared with air-treated controls. In contrast, CO only marginally prevented lipid peroxidation, but it suppressed I/R-induced mRNA upregulation for several pro-inflammatory mediators and reduced graft apoptosis. CONCLUSIONS Combined therapy with hydrogen and CO demonstrated enhanced therapeutic efficacy via both anti-oxidant and anti-inflammatory mechanisms, and may be a clinically feasible approach for preventing cold I/R injury of the myocardium.