Systemic AAV9.LAMP2B injection reverses metabolic and physiologic multiorgan dysfunction in a murine model of Danon disease.

Danon disease (DD) is a rare X-linked autophagic vacuolar myopathy associated with multiorgan dysfunction, including the heart, skeletal muscle, and liver. There are no specific treatments, and most male patients die from advanced heart failure during the second or third decade of life. DD is caused by mutations in the lysosomal-associated membrane protein 2 (LAMP2) gene, a key mediator of autophagy. LAMP2 has three isoforms: LAMP2A, LAMP2B, and LAMP2C. LAMP2B is the predominant isoform expressed in cardiomyocytes. This study evaluates the efficacy of human LAMP2B gene transfer using a recombinant adeno-associated virus 9 carrying human LAMP2B (AAV9.LAMP2B) in a Lamp2 knockout (KO) mouse, a DD model. AAV9.LAMP2B was intravenously injected into 2- and 6-month-old Lamp2 KO male mice to assess efficacy in adolescent and adult phenotypes. Lamp2 KO mice receiving AAV9.LAMP2B demonstrated dose-dependent restoration of human LAMP2B protein in the heart, liver, and skeletal muscle tissue. Impaired autophagic flux, evidenced by increased LC3-II, was abrogated by LAMP2B gene transfer in all tissues in both cohorts. Cardiac function was also improved, and transaminases were reduced in AAV9.LAMP2B-treated KO mice, indicating favorable effects on the heart and liver. Survival was also higher in the older cohort receiving high vector doses. No anti-LAMP2 antibodies were detected in mice that received AAV9.LAMP2B. In summary, LAMP2B gene transfer improves metabolic and physiologic function in a DD murine model, suggesting that a similar therapeutic approach may be effective for treating patients with this highly morbid disease.

Bioprosthetic aortic valve leaflet disruption with high energy electrocautery to prevent coronary artery obstruction during valve-in-valve transcatheter aortic valve replacement.

Transcatheter aortic valve replacement (TAVR) is well-established for the treatment of bioprosthetic aortic valve stenosis (AS) in high surgical risk patients. Coronary artery obstruction from displacement of the bioprosthetic valve leaflets during valve-in-valve (VIV) TAVR is a rare, but potentially fatal, complication. Recently, the bioprosthetic aortic scallop intentional laceration to prevent iatrogenic coronary artery obstruction (BASILICA) procedure was developed as a method for disrupting bioprosthetic leaflets in patients undergoing VIV TAVR at high risk for coronary obstruction. This case describes a successful VIV TAVR utilizing a simplified concept of the BASILICA technique in a patient where the full procedure could not be completed.

Impaired mitophagy facilitates mitochondrial damage in Danon disease.

RATIONALE: Lysosomal associated membrane protein type-2 (LAMP-2) is a highly conserved, ubiquitous protein that is critical for autophagic flux. Loss of function mutations in the LAMP-2 gene cause Danon disease, a rare X-linked disorder characterized by developmental delay, skeletal muscle weakness, and severe cardiomyopathy. We previously found that human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from Danon patients exhibited significant mitochondrial oxidative stress and apoptosis. Understanding how loss of LAMP-2 expression leads to cardiomyocyte dysfunction and heart failure has important implications for the treatment of Danon disease as well as a variety of other cardiac disorders associated with impaired autophagy. OBJECTIVE: Elucidate the pathophysiology of cardiac dysfunction in Danon disease. METHODS AND RESULTS: We created hiPSCs from two patients with Danon disease and differentiated those cells into hiPSC-CMs using well-established protocols. Danon hiPSC-CMs demonstrated an accumulation of damaged mitochondria, disrupted mitophagic flux, depressed mitochondrial respiratory capacity, and abnormal gene expression of key mitochondrial pathways. Restoring the expression of LAMP-2B, the most abundant LAMP-2 isoform in the heart, rescued mitophagic flux as well as mitochondrial health and bioenergetics. To confirm our findings in vivo, we evaluated Lamp-2 knockout (KO) mice. Impaired autophagic flux was noted in the Lamp-2 KO mice compared to WT reporter mice, as well as an increased number of abnormal mitochondria, evidence of incomplete mitophagy, and impaired mitochondrial respiration. Physiologically, Lamp-2 KO mice demonstrated early features of contractile dysfunction without overt heart failure, indicating that the metabolic abnormalities associated with Danon disease precede the development of end-stage disease and are not merely part of the secondary changes associated with heart failure. CONCLUSIONS: Incomplete mitophagic flux and mitochondrial dysfunction are noted in both in vitro and in vivo models of Danon disease, and proceed overt cardiac contractile dysfunction. This suggests that impaired mitochondrial clearance may be central to the pathogenesis of disease and a potential target for therapeutic intervention.

iPSCORE: A Resource of 222 iPSC Lines Enabling Functional Characterization of Genetic Variation across a Variety of Cell Types.

Large-scale collections of induced pluripotent stem cells (iPSCs) could serve as powerful model systems for examining how genetic variation affects biology and disease. Here we describe the iPSCORE resource: a collection of systematically derived and characterized iPSC lines from 222 ethnically diverse individuals that allows for both familial and association-based genetic studies. iPSCORE lines are pluripotent with high genomic integrity (no or low numbers of somatic copy-number variants) as determined using high-throughput RNA-sequencing and genotyping arrays, respectively. Using iPSCs from a family of individuals, we show that iPSC-derived cardiomyocytes demonstrate gene expression patterns that cluster by genetic background, and can be used to examine variants associated with physiological and disease phenotypes. The iPSCORE collection contains representative individuals for risk and non-risk alleles for 95% of SNPs associated with human phenotypes through genome-wide association studies. Our study demonstrates the utility of iPSCORE for examining how genetic variants influence molecular and physiological traits in iPSCs and derived cell lines.

Human-Induced Pluripotent Stem Cell-Based Modeling of Cardiac Storage Disorders.

PURPOSE OF REVIEW: The aim of this study is to review the published human-induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) models of cardiac storage disorders and to evaluate the limitations and future applications of this technology. RECENT FINDINGS: Several cardiac storage disorders (CSDs) have been modeled using patient-specific hiPSC-CMs, including Anderson-Fabry disease, Danon disease, and Pompe disease. These models have shown that patient-specific hiPSC-CMs faithfully recapitulate key phenotypic features of CSDs and respond predictably to pharmacologic manipulation. hiPSC-CMs generated from patients with CSDs are representative models of the patient disease state and can be used as an in vitro system for the study of human cardiomyocytes. While these models suffer from several limitations, they are likely to play an important role in future mechanistic studies of cardiac storage disorders and the development of targeted therapeutics for these diseases.

Induced pluripotent stem cells for the study of cardiovascular disease.

Groundbreaking advances in stem cell research have led to techniques for the creation of human cardiomyocytes from cells procured from a variety of sources, including a simple skin biopsy. Since the advent of this technology, most research has focused on utilizing these cells for therapeutic purposes. However, recent studies have demonstrated that stem cell-derived cardiomyocytes generated from patients with inherited cardiovascular disorders recapitulate key phenotypic features of disease in vitro. Furthermore, these cells can be maintained in culture for prolonged periods of time and used for extensive biochemical and physiological analysis. By serving as models of inherited cardiac disorders, these systems have the potential to fundamentally change the manner in which cardiovascular disease is studied and new therapies are developed.

AIDS-associated Kaposi sarcoma: outcomes after initiation of antiretroviral therapy at a university-affiliated hospital in urban Zimbabwe.

OBJECTIVE: To retrospectively investigate the outcomes of patients with AIDS-associated Kaposi sarcoma (AIDS-KS) after initiation of antiretroviral therapy (ART), under routine practice conditions, at a university-affiliated hospital in urban Zimbabwe. BACKGROUND: While studies from developed nations have demonstrated excellent outcomes for AIDS-KS patients treated with ART, few studies have examined the outcomes of African AIDS-KS patients after starting therapy. METHODS: A retrospective cohort of 124 AIDS patients initiating ART under routine practice conditions was studied. Thirty-one patients with AIDS-KS were matched 1:3 to 93 AIDS patients without KS (non-KS). The primary outcome was loss-to-care after initiation of therapy. Multivariate analysis was performed to identify significant predictors of loss-to-care. The percent change in weight at 6 months after starting ART was a secondary outcome. A sub-group analysis evaluated differences in pre-treatment variables between AIDS-KS patients retained-in-care compared to those lost-to-care. RESULTS: AIDS-KS patients had significantly greater 2-year proportional loss-to-care than matched non-KS AIDS patients (26.4% vs. 9.5%; p = 0.01) after initiation of ART. In multivariate analysis, the presence of KS (p = 0.02) was the only significant predictor of loss-to-care. AIDS-KS patients had significantly less weight gain after starting ART than non-KS AIDS patients (+3.4% vs. +6.4%; p = 0.03). AIDS-KS patients retained-in-care had significantly higher pre-treatment CD4+ lymphocyte counts than AIDS-KS patients lost-to-care (223 vs. 110 cells/mm(3); p = 0.04). CONCLUSIONS: In this retrospective study, AIDS-KS patients experienced significantly worse outcomes than matched non-KS AIDS patients after initiation of ART. AIDS-KS patients with higher pre-treatment CD4+ lymphocyte counts were more likely to be retained in care.