Molecular Pathways and Animal Models of Arrhythmias.

Arrhythmias account for over 300,000 annual deaths in the United States, and approximately half of all deaths are associated with heart disease. Mechanisms underlying arrhythmia risk are complex; however, work in humans and animal models over the past 25 years has identified a host of molecular pathways linked with both arrhythmia substrates and triggers. This chapter will focus on select arrhythmia pathways solved by linking human clinical and genetic data with animal models.

Creating a 'Molecular Band-Aid'; Blocking an Exposed Protease Target Site in Desmoplakin.

Desmoplakin (DSP) is a large (~260 kDa) protein found in the desmosome, a subcellular complex that links the cytoskeleton of one cell to its neighbor. A mutation 'hot-spot' within the NH2-terminal third of the DSP protein (specifically, residues 299-515) is associated with both cardiomyopathies and skin defects. In select DSP variants, disease is linked specifically to the uncovering of a previously-occluded calpain target site (residues 447-451). Here, we partially stabilize these calpain-sensitive DSP clinical variants through the addition of a secondary single point mutation-tyrosine for leucine at amino acid position 518 (L518Y). Molecular dynamic (MD) simulations and enzymatic assays reveal that this stabilizing mutation partially blocks access to the calpain target site, resulting in restored DSP protein levels. This 'molecular band-aid' provides a novel way to maintain DSP protein levels, which may lead to new strategies for treating this subset of DSP-related disorders.

Extracellular Vesicles Derived from a Human Brain Endothelial Cell Line Increase Cellular ATP Levels.

Engineered cell-derived extracellular vesicles (EVs) such as exosomes and microvesicles hold immense potential as safe and efficient drug carriers due to their lower immunogenicity and inherent homing capabilities to target cells. In addition to innate vesicular cargo such as lipids, proteins, and nucleic acids, EVs are also known to contain functional mitochondria/mitochondrial DNA that can be transferred to recipient cells to increase cellular bioenergetics. In this proof-of-concept study, we isolated naïve EVs and engineered EVs loaded with an exogenous plasmid DNA encoding for brain-derived neurotrophic factor (BDNF-EVs) from hCMEC/D3, a human brain endothelial cell line, and RAW 264.7 macrophages. We tested whether mitochondrial components in naïve or engineered EVs can increase ATP levels in the recipient brain endothelial cells. EVs (e.g., exosomes and microvesicles; EXOs and MVs) were isolated from the conditioned medium of either untreated (naïve) or pDNA-transfected (Luc-DNA or BDNF-DNA) cells using a differential centrifugation method. RAW 264.7 cell line-derived EVs showed a significantly higher DNA loading and increased luciferase expression in the recipient hCMEC/D3 cells at 72 h compared with hCMEC/D3 cell line-derived EVs. Naïve EVs from hCMEC/D3 cells and BDNF-EVs from RAW 264.7 cells showed a small, but a significantly greater increase in the ATP levels of recipient hCMEC/D3 cells at 24 and 48 h post-exposure. In summary, we have demonstrated (1) differences in exogenous pDNA loading into EVs as a function of cell type using brain endothelial and macrophage cell lines and (2) EV-mediated increases in the intracellular ATP levels in the recipient hCMEC/D3 monolayers.

Improving access in a VA primary care clinic using an innovative Panel Retention Tool: a quality improvement report.

BACKGROUND: Loss to follow-up is an under-recognised problem in primary care. Continuity with a primary care provider improves morbidity and mortality in the Veterans Health Administration. We sought to reduce the percentage of patients lost to follow-up at the Northeast Ohio Veterans Affairs Healthcare System from October 2017 to March 2019. METHODS: The Panel Retention Tool (PRT) was developed and tested with primary care teams using multiple Plan, Do, Study and Act cycles to identify and schedule lost to follow-up patients. Baseline data on loss to follow-up, defined as the percentage of panelled patients not seen in primary care in the past year, was collected over 6 months during tool development. Outcomes were tracked from implementation through spread and sustainment (12 months) across 14 primary care clinics. RESULTS: Of the 96 170 panelled patients at the beginning of the study period, 2715 (2.8%) were found to be inactive and removed from provider panels, improving panel reliability. Among the remaining, 1856 (1.9%) patients without scheduled follow-up were scheduled for future care, and 1239 (1.3%) without recent prior care completed encounters during the study period. The percentage of patients lost to follow-up decreased from 10.1% (lower control limit (LCL) 9.8%-upper control limit (UCL) 10.4%) at baseline to 6.4% (LCL 6.2%-UCL 6.7%) postintervention and patients without planned future care decreased from 21.7% (LCL 21.3%-UCL 22.1%) to 17.1% (LCL 16.7%-UCL 17.5%). CONCLUSIONS: The PRT allowed primary care teams in an integrated health system to identify and schedule lost to follow-up patients. Ease of use, adaptability and encouraging outcomes facilitated spread. This has the potential to contribute to more appropriate utilisation of healthcare resources and improved access to primary care.