Mast cell activation and degranulation in acute artery injury: A target for post-operative therapy.

The increasing incidence of cardiovascular disease (CVD) has led to a significant ongoing need to address this surgically through coronary artery bypass grafting (CABG) and percutaneous coronary interventions (PCI). From this, there continues to be a substantial burden of mortality and morbidity due to complications arising from endothelial damage, resulting in restenosis. Whilst mast cells (MC) have been shown to have a causative role in atherosclerosis and other vascular diseases, including restenosis due to vein engraftment; here, we demonstrate their rapid response to arterial wire injury, recapitulating the endothelial damage seen in PCI procedures. Using wild-type mice, we demonstrate accumulation of MC in the femoral artery post-acute wire injury, with rapid activation and degranulation, resulting in neointimal hyperplasia, which was not observed in MC-deficient KitW-sh/W-sh mice. Furthermore, neutrophils, macrophages, and T cells were abundant in the wild-type mice area of injury but reduced in the KitW-sh/W-sh mice. Following bone-marrow-derived MC (BMMC) transplantation into KitW-sh/W-sh mice, not only was the neointimal hyperplasia induced, but the neutrophil, macrophage, and T-cell populations were also present in these transplanted mice. To demonstrate the utility of MC as a target for therapy, we administered the MC stabilizing drug, disodium cromoglycate (DSCG) immediately following arterial injury and were able to show a reduction in neointimal hyperplasia in wild-type mice. These studies suggest a critical role for MC in inducing the conditions and coordinating the detrimental inflammatory response seen post-endothelial injury in arteries undergoing revascularization procedures, and by targeting the rapid MC degranulation immediately post-surgery with DSCG, this restenosis may become a preventable clinical complication.

Impaired angiogenesis and extracellular matrix metabolism in autosomal-dominant hyper-IgE syndrome.

There are more than 7000 described rare diseases, most lacking specific treatment. Autosomal-dominant hyper-IgE syndrome (AD-HIES, also known as Job's syndrome) is caused by mutations in STAT3. These patients present with immunodeficiency accompanied by severe nonimmunological features, including skeletal, connective tissue, and vascular abnormalities, poor postinfection lung healing, and subsequent pulmonary failure. No specific therapies are available for these abnormalities. Here, we investigated underlying mechanisms in order to identify therapeutic targets. Histological analysis of skin wounds demonstrated delayed granulation tissue formation and vascularization during skin-wound healing in AD-HIES patients. Global gene expression analysis in AD-HIES patient skin fibroblasts identified deficiencies in a STAT3-controlled transcriptional network regulating extracellular matrix (ECM) remodeling and angiogenesis, with hypoxia-inducible factor 1α (HIF-1α) being a major contributor. Consistent with this, histological analysis of skin wounds and coronary arteries from AD-HIES patients showed decreased HIF-1α expression and revealed abnormal organization of the ECM and altered formation of the coronary vasa vasorum. Disease modeling using cell culture and mouse models of angiogenesis and wound healing confirmed these predicted deficiencies and demonstrated therapeutic benefit of HIF-1α-stabilizing drugs. The study provides mechanistic insights into AD-HIES pathophysiology and suggests potential treatment options for this rare disease.

Generation of human induced pluripotent stem cells (NIHTVBi004-A, NIHTVBi005-A, NIHTVBi006-A, NIHTVBi007-A, NIHTVBi008-A) from 5 CADASIL patients with NOTCH3 mutation.

We have successfully generated induced pluripotent stem cell (iPSC) lines derived from peripheral blood mononuclear cells of five patients with Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). These cells carry the genetic NOTCH3 mutation present in their parental cells. These iPSC cells exhibited normal karyotype and phenotype, which were sustained through propagation. Furthermore, these iPSCs displayed the capacity of differentiating toward the three germ layers in vitro.

Generation of human induced pluripotent stem cell lines (NIHTVBi011-A, NIHTVBi012-A, NIHTVBi013-A) from autosomal dominant Hyper IgE syndrome (AD-HIES) patients carrying STAT3 mutation.

Autosomal dominant Hyper IgE syndrome (AD-HIES), a rare immune deficiency affecting fewer than one per million people, is caused by heterozygous deleterious mutations in STAT3. STAT3 signaling plays crucial roles in basic cellular functions affecting broad aspects of cellular homeostasis. Accordingly, in addition to immunological deficits, patients experience severe multisystem non-immunological features. Human induced pluripotent stem cells (hiPSC) are well established as in vivo disease models for various human pathologies. We describe the generation of iPSC from three AD-HIES patients. These iPSCs express pluripotency markers, differentiate into three germ layers, have normal karyotype and similar genome identity to parental cells.

Generation of human induced pluripotent stem cells from individuals with a homozygous CCR5Δ32 mutation.

Chemokine receptor 5 (CCR5) is the primary coreceptor for HIV entry into macrophages. Individuals with a homozygous deletion of 32 bp in the CCR5 gene (CCR5Δ32) are highly resistant to HIV infection (Samson et al., 1996). Allogeneic stem cell transplantation from a healthy donor with the homozygous CCR5Δ32 variant to an HIV positive individual has demonstrated efficient long-term control of HIV. We identified three individuals with this homozygous CCR5Δ32 variant, and successfully generated induced pluripotent stem cell (iPSC) lines from their dermal fibroblasts. The iPSCs lines carrying homozygous CCR5Δ32 variant displayed phenotypically normal and the potential to differentiation toward the three germ layers.

Efficient differentiation of cardiomyocytes and generation of calcium-sensor reporter lines from nonhuman primate iPSCs.

Nonhuman primate (NHP) models are more predictive than rodent models for developing induced pluripotent stem cell (iPSC)-based cell therapy, but robust and reproducible NHP iPSC-cardiomyocyte differentiation protocols are lacking for cardiomyopathies research. We developed a method to differentiate integration-free rhesus macaque iPSCs (RhiPSCs) into cardiomyocytes with >85% purity in 10 days, using fully chemically defined conditions. To enable visualization of intracellular calcium flux in beating cardiomyocytes, we used CRISPR/Cas9 to stably knock-in genetically encoded calcium indicators at the rhesus AAVS1 safe harbor locus. Rhesus cardiomyocytes derived by our stepwise differentiation method express signature cardiac markers and show normal electrochemical coupling. They are responsive to cardiorelevant drugs and can be successfully engrafted in a mouse myocardial infarction model. Our approach provides a powerful tool for generation of NHP iPSC-derived cardiomyocytes amenable to utilization in basic research and preclinical studies, including in vivo tissue regeneration models and drug screening.

Increased activity of TNAP compensates for reduced adenosine production and promotes ectopic calcification in the genetic disease ACDC.

ACDC (arterial calcification due to deficiency of CD73) is an autosomal recessive disease resulting from loss-of-function mutations in NT5E, which encodes CD73, a 5'-ectonucleotidase that converts extracellular adenosine monophosphate to adenosine. ACDC patients display progressive calcification of lower extremity arteries, causing limb ischemia. Tissue-nonspecific alkaline phosphatase (TNAP), which converts pyrophosphate (PPi) to inorganic phosphate (Pi), and extracellular purine metabolism play important roles in other inherited forms of vascular calcification. Compared to cells from healthy subjects, induced pluripotent stem cell-derived mesenchymal stromal cells (iMSCs) from ACDC patients displayed accelerated calcification and increased TNAP activity when cultured under conditions that promote osteogenesis. TNAP activity generated adenosine in iMSCs derived from ACDC patients but not in iMSCs from control subjects, which have CD73. In response to osteogenic stimulation, ACDC patient-derived iMSCs had decreased amounts of the TNAP substrate PPi, an inhibitor of extracellular matrix calcification, and exhibited increased activation of AKT, mechanistic target of rapamycin (mTOR), and the 70-kDa ribosomal protein S6 kinase (p70S6K), a pathway that promotes calcification. In vivo, teratomas derived from ACDC patient cells showed extensive calcification and increased TNAP activity. Treating mice bearing these teratomas with an A2b adenosine receptor agonist, the mTOR inhibitor rapamycin, or the bisphosphonate etidronate reduced calcification. These results show that an increase of TNAP activity in ACDC contributes to ectopic calcification by disrupting the extracellular balance of PPi and Pi and identify potential therapeutic targets for ACDC.

TGF-ß signaling mediates endothelial-to-mesenchymal transition (EndMT) during vein graft remodeling.

Veins grafted into an arterial environment undergo a complex vascular remodeling process. Pathologic vascular remodeling often results in stenosed or occluded conduit grafts. Understanding this complex process is important for improving the outcome of patients with coronary and peripheral artery disease undergoing surgical revascularization. Using in vivo murine cell lineage-tracing models, we show that endothelial-derived cells contribute to neointimal formation through endothelial-to-mesenchymal transition (EndMT), which is dependent on early activation of the Smad2/3-Slug signaling pathway. Antagonism of transforming growth factor-ß (TGF-ß) signaling by TGF-ß neutralizing antibody, short hairpin RNA-mediated Smad3 or Smad2 knockdown, Smad3 haploinsufficiency, or endothelial cell-specific Smad2 deletion resulted in decreased EndMT and less neointimal formation compared to controls. Histological examination of postmortem human vein graft tissue corroborated the changes observed in our mouse vein graft model, suggesting that EndMT is operative during human vein graft remodeling. These data establish that EndMT is an important mechanism underlying neointimal formation in interpositional vein grafts, and identifies the TGF-ß-Smad2/3-Slug signaling pathway as a potential therapeutic target to prevent clinical vein graft stenosis.