Expanded Contraceptive Access Linked To Increase In College Completion Among Women In Colorado.

Public subsidies for contraception are often justified by assertions regarding their benefits for women's lives, yet there is limited contemporary evidence supporting these assertions. Beginning in 2009 the Colorado Family Planning Initiative abruptly expanded access to the full range of contraceptive methods through Colorado's Title X family planning clinics. Using eleven years of American Community Survey data linked to data from two decennial censuses, we assessed whether exposure to the program led to improvements in college completion among women. Exposure to the Colorado Family Planning Initiative at high school ages was associated with a population-level increase of 1.8-3.5 percentage points in women's on-time bachelor's degree attainment, which represents a 6-12 percent increase in women obtaining their degrees compared with earlier cohorts. Federal and state policies restricting or expanding access to the full range of contraceptive methods can affect women's attainment of higher education in addition to their reproductive health.

Multicenter experience with valve-in-valve transcatheter aortic valve replacement compared with primary, native valve transcatheter aortic valve replacement.

BACKGROUND: Valve-in-valve (ViV) transcatheter aortic valve replacement (TAVR) offers an alternative to reoperative surgical aortic valve replacement. The short- and intermediate-term outcomes after ViV TAVR in the real world are not entirely clear. PATIENTS AND METHODS: A multicenter, retrospective analysis of a consecutive series of 121 ViV TAVR patients and 2200 patients undergoing primary native valve TAVR from 2012 to 2017 at six medical centers. The main outcome measures were in-hospital mortality, 30-day mortality, stroke, myocardial infarction, acute kidney injury, and pacemaker implantation. RESULTS: ViV patients were more likely male, younger, prior coronary artery bypass graft, "hostile chest," and urgent. 30% of the patients had Society of Thoracic Surgeons risk score <4%, 36.3% were 4%-8% and 33.8% were >8%. In both groups many patients had concomitant coronary artery disease. Median time to prosthetic failure was 9.6 years (interquartile range: 5.5-13.5 years). 82% of failed surgical valves were size 21, 23, or 25 mm. Access was 91% femoral. After ViV, 87% had none or trivial aortic regurgitation. Mean gradients were <20 mmHg in 54.6%, 20-29 mmHg in 30.6%, 30-39 mmHg in 8.3% and ≥40 mmHg in 5.87%. Median length of stay was 4 days. In-hospital mortality was 0%. 30-day mortality was 0% in ViV and 3.7% in native TAVR. There was no difference in in-hospital mortality, postprocedure myocardial infarction, stroke, or acute kidney injury. CONCLUSION: Compared to native TAVR, ViV TAVR has similar peri-procedural morbidity with relatively high postprocedure mean gradients. A multidisciplinary approach will help ensure patients receive the ideal therapy in the setting of structural bioprosthetic valve degeneration.

Concordance of Guideline-Based Risk Stratification and Selection of Patients for Transcatheter Aortic Valve Implantation or Surgical Replacement.

The 2020 American Health Association/American College of Cardiology valve guidelines recommend surgical aortic valve replacement (SAVR) for symptomatic patients with aortic stenosis (AS) age <65 years and transcatheter aortic valve implantation (TAVI) for patients with AS age >80 years. We analyzed TAVI versus SAVR practice patterns using age-based recommendations. We compared 2016-to-2019 TAVI and isolated SAVR in northern New England at 5 centers according to guideline-recommended age groups. Multivariable logistic regression was performed to identify independent predictors of TAVI for the intermediate age group. The study was approved by each site's institutional review board in accordance with ongoing participation and quality improvement efforts in the Northern New England Cardiovascular Study Group. Among 4,161 patients with isolated severe AS, TAVI increased from 2016 to 2019: 55.8% versus 76.1%, p <0.01 for trend. SAVR for patients with AS age >80 years was uncommon and decreased over time: 13.1% versus 1.6%, p <0.01. TAVI utilization nearly doubled over time in young patients with AS age <65 years (14.3% vs 26.2%, p <0.01). Preference for SAVR decreased by 50% over time (p <0.01) in the intermediate age group (65 to 80 years). Independent predictors of TAVI among patients aged 65 to 80 years included older age, chronic obstructive pulmonary disease, previous stroke, and coronary artery bypass grafting, whereas vascular disease and clinical urgency favored SAVR. In conclusion, consistent with current American Health Association/American College of Cardiology guidelines, TAVI was the treatment of choice in >97% of severe patients with AS age >80 years by 2019. TAVI utilization in patients <65 years has doubled over time and thus may not reflect current guideline recommendations. TAVI is the preferred choice in those aged 65 to 80 years, especially among patients with previous stroke or coronary artery bypass grafting.

Decade Long Temporal Trends in Revascularization for Patients With Diabetes Mellitus (From the Northern New England Cardiovascular Disease Study Group).

The FREEDOM trial demonstrated superiority of coronary artery bypass grafting (CABG) for patients with diabetes mellitus (DM) and multivessel coronary artery disease (MV CAD) as compared to percutaneous coronary intervention (PCI) with drug eluting stent (PCI-DES). We sought to study the impact of the FREEDOM trial on clinical practice. We studied trends in the use of CABG vs. PCI and factors associated with revascularization strategy among 6,985 patients with concomitant CAD and MV CAD at 7 centers pre- and post-trial (2008-2012 vs. 2013-2017) as well as hospital outcomes. Multivariable mixed effects logistic regression was performed to identify risk factors associated with choice of revascularization strategy among the patients with 3-vessel CAD (3V CAD). 41% of patients had 3V CAD and 18% were ≥75 years of age. While PCI-DES was the preferred strategy in 2-vessel CAD (2V CAD), 72% of patients with 3V CAD underwent CABG. For patients with 3V CAD, the ratio of CABG to PCI-DES procedures was 2.47 over the decade and did not differ pre- and post-trial (adjusted odds ratio (OR) for CABG (vs. PCI) 1.01, 95% confidence interval (CI) 0.84-1.20). Independent risk factors of CABG among patients with DM and 3V CAD included peripheral arterial disease and absence of prior myocardial infarction and prior PCI. The risk factors for PCI were female sex (OR 0.60, 95% CI 0.50-0.73, p<0.001) and age ≥75 (OR 0.50, 95% CI 0.35-0.72, p<0.001). Center based variability was observed for CABG vs. PCI (center effect, rho=14%, p<0.001). In conclusion, PCI-DES is the preferred strategy for DM patients with MV CAD. Yet, among those with 3V CAD, CABG was chosen in ¾ of patients with no change in clinical practice related to the publication of the FREEDOM trial.

Acute Kidney Recovery in Patients Who Underwent Transcatheter Versus Surgical Aortic Valve Replacement (from the Northern New England Cardiovascular Disease Study Group).

Acute kidney recovery (AKR) is a recently described phenomenon observed after transcatheter aortic valve replacement (TAVR) and is more frequent than acute kidney injury (AKI). To determine the incidence and predictors of AKR between surgical aortic valve replacement (SAVR) and TAVR, we examined patients with chronic kidney disease and severe aortic stenosis who underwent SAVR or TAVR procedure between 2007 and 2017; excluding age <65 or >90, dialysis, endocarditis, non-aortic valve stenosis, or patients died within 48-hours postprocedure. AKR was defined as an increase of estimated glomerular filtration rate (eGFR) >25% and AKI as decrease in eGFR >25% at discharge. Stroke, mortality, major bleeding, transfusion, and length of stay were examined. Multivariate logistic regression analysis was used to examine predictors of AKR. There were 750 transcatheter and 1,062 surgical patients and 319 pairs after propensity matching. AKR was observed in 26% TAVR versus 23.2% SAVR, p = 0.062. Highest recovery was in patients with eGFR <30 for both TAVR (33.7%) and SAVR (34.5%) patients. Independent predictors of AKR were ejection fraction <50% (odds ratio [OR] 1.66, 95% confidence interval [CI] 1.02 to 2.71, p = 0.042), female gender (OR 1.66, 95% CI 1.1 to 2.5, p = 0.015), and obesity (OR 1.5, 95% CI 1.04-2.3, p = 0.032). Diabetes was a negative predictor of AKR (OR 0.55, 95% CI 0.36 to 0.84, p = 0.005). AKR was associated with improved secondary clinical outcomes compared with AKI. In conclusion, AKR is a generalizable phenomenon occurring frequently and similarly among transcatheter or surgical aortic valve patients. Diabetes is a negative predictor of AKR, possibly indicative of less reversible kidney disease.

Recovery of Kidney Dysfunction After Transcatheter Aortic Valve Implantation (from the Northern New England Cardiovascular Disease Study Group).

Acute Kidney Recovery (AKR) is a potential benefit of transcatheter aortic valve implantation (TAVI). We determined the incidence and predictors of AKR in a multicenter prospective registry of TAVI. After excluding patients on dialysis or who died within 48 hours postprocedure, we reviewed 1,502 consecutive patients underwent TAVI in Northern New England from 2012 to 2017. Patients were categorized into 3 groups based on the change in postprocedure estimated glomerular filtration rate (eGFR): Acute Kidney Injury (AKI, decrease in eGFR >25%), AKR (increase in eGFR >25%) or no change in kidney function on discharge creatinine following TAVI. We then focused in patients with baseline chronic kidney disease (CKD defined as eGFR ≤60 ml/min; n = 755) and developed multivariate predictor models to determine the clinical and procedural variables associated with AKR. For the TAVI cohort (n = 1,502), the overall incidence of AKR was 17.8%. AKR was threefold higher in patients with eGFR ≤60 ml/min as compared to those with eGFR >60 ml/min (26.6% vs 8.9%, p < 0.001). In the CKD population, hospital complications were similar among patients with no change in renal function and AKR; patients with AKI had a higher rate of hospital mortality, pacemaker implantation, length of hospitalization, and transfusions. Using multivariable logistic regression, moderate to severe lung disease, eGFR < 50 ml/min and previous aortic valve surgery were found to be independent predictors of AKR. Patients with diabetes mellitus, baseline anemia, and Society of thoracic surgeons score >6.1 were less likely to develop AKR. In conclusion, AKR occurred in 1 of 4 of all TAVI patients with baseline CKD and was a more frequent phenomena than AKI. Patients with decreased lung function, previous aortic valve surgery and worse baseline renal function were more likely to demonstrate AKR, whereas patients with diabetes mellitus, baseline anemia, and higher Society of thoracic risk scores were less likely to see improvements in renal function after TAVI.

Analysis of individual cells identifies cell-to-cell variability following induction of cellular senescence.

Senescent cells play important roles in both physiological and pathological processes, including cancer and aging. In all cases, however, senescent cells comprise only a small fraction of tissues. Senescent phenotypes have been studied largely in relatively homogeneous populations of cultured cells. In vivo, senescent cells are generally identified by a small number of markers, but whether and how these markers vary among individual cells is unknown. We therefore utilized a combination of single-cell isolation and a nanofluidic PCR platform to determine the contributions of individual cells to the overall gene expression profile of senescent human fibroblast populations. Individual senescent cells were surprisingly heterogeneous in their gene expression signatures. This cell-to-cell variability resulted in a loss of correlation among the expression of several senescence-associated genes. Many genes encoding senescence-associated secretory phenotype (SASP) factors, a major contributor to the effects of senescent cells in vivo, showed marked variability with a subset of highly induced genes accounting for the increases observed at the population level. Inflammatory genes in clustered genomic loci showed a greater correlation with senescence compared to nonclustered loci, suggesting that these genes are coregulated by genomic location. Together, these data offer new insights into how genes are regulated in senescent cells and suggest that single markers are inadequate to identify senescent cells in vivo.

Long-term calorie restriction in humans is not associated with indices of delayed immunologic aging: A descriptive study.

BACKGROUND: Delayed immunologic aging is purported to be a major mechanism through which calorie restriction (CR) exerts its anti-aging effects in non-human species. However, in non-obese humans, the effect of CR on the immune system has been understudied relative to its effects on the cardiometabolic system. OBJECTIVE: To examine whether CR is associated with delayed immunologic aging in non-obese humans. METHODS: We tested whether long-term CR practitioners (average 10.03 years of CR) evidenced decreased expression of T cell immunosenescence markers and longer immune cell telomeres compared to gender-, race/ethnicity-, age-, and education-matched "healthy" Body Mass Index (BMI) and "overweight"/"obese" BMI groups. RESULTS: Long-term human CR practitioners had lower BMI (p <  0.001) and fasting glucose (p <  0.001), as expected. They showed similar frequencies of pre-senescent cells (CD8+CD28- T cells and CD57 and PD-1 expressing T cells) to the comparison groups. Even after adjusting for covariates, including cytomegalovirus status, we observed shorter peripheral blood mononuclear cell telomeres in the CR group (p = 0.012) and no difference in granulocyte telomeres between groups (p = 0.42). CONCLUSIONS: We observed no clear evidence that CR as it is currently practiced in humans delays immune aging related to telomere length or T cell immunosenescent markers.

Adrenergic Receptors in Individual Ventricular Myocytes: The Beta-1 and Alpha-1B Are in All Cells, the Alpha-1A Is in a Subpopulation, and the Beta-2 and Beta-3 Are Mostly Absent.

RATIONALE: It is unknown whether every ventricular myocyte expresses all 5 of the cardiac adrenergic receptors (ARs), ß1, ß2, ß3, α1A, and α1B. The ß1 and ß2 are thought to be the dominant myocyte ARs. OBJECTIVE: Quantify the 5 cardiac ARs in individual ventricular myocytes. METHODS AND RESULTS: We studied ventricular myocytes from wild-type mice, mice with α1A and α1B knockin reporters, and ß1 and ß2 knockout mice. Using individual isolated cells, we measured knockin reporters, mRNAs, signaling (phosphorylation of extracellular signal-regulated kinase and phospholamban), and contraction. We found that the ß1 and α1B were present in all myocytes. The α1A was present in 60%, with high levels in 20%. The ß2 and ß3 were detected in only ≈5% of myocytes, mostly in different cells. In intact heart, 30% of total ß-ARs were ß2 and 20% were ß3, both mainly in nonmyocytes. CONCLUSION: The dominant ventricular myocyte ARs present in all cells are the ß1 and α1B. The ß2 and ß3 are mostly absent in myocytes but are abundant in nonmyocytes. The α1A is in just over half of cells, but only 20% have high levels. Four distinct myocyte AR phenotypes are defined: 30% of cells with ß1 and α1B only; 60% that also have the α1A; and 5% each that also have the ß2 or ß3. The results raise cautions in experimental design, such as receptor overexpression in myocytes that do not express the AR normally. The data suggest new paradigms in cardiac adrenergic signaling mechanisms.

Exercise-induced mitochondrial p53 repairs mtDNA mutations in mutator mice.

BACKGROUND: Human genetic disorders and transgenic mouse models have shown that mitochondrial DNA (mtDNA) mutations and telomere dysfunction instigate the aging process. Epidemiologically, exercise is associated with greater life expectancy and reduced risk of chronic diseases. While the beneficial effects of exercise are well established, the molecular mechanisms instigating these observations remain unclear. RESULTS: Endurance exercise reduces mtDNA mutation burden, alleviates multisystem pathology, and increases lifespan of the mutator mice, with proofreading deficient mitochondrial polymerase gamma (POLG1). We report evidence for a POLG1-independent mtDNA repair pathway mediated by exercise, a surprising notion as POLG1 is canonically considered to be the sole mtDNA repair enzyme. Here, we show that the tumor suppressor protein p53 translocates to mitochondria and facilitates mtDNA mutation repair and mitochondrial biogenesis in response to endurance exercise. Indeed, in mutator mice with muscle-specific deletion of p53, exercise failed to prevent mtDNA mutations, induce mitochondrial biogenesis, preserve mitochondrial morphology, reverse sarcopenia, or mitigate premature mortality. CONCLUSIONS: Our data establish a new role for p53 in exercise-mediated maintenance of the mtDNA genome and present mitochondrially targeted p53 as a novel therapeutic modality for diseases of mitochondrial etiology.

Genome-wide DNA methylation changes with age in disease-free human skeletal muscle.

A decline in skeletal muscle mass and function with aging is well recognized, but remains poorly characterized at the molecular level. Here, we report for the first time a genome-wide study of DNA methylation dynamics in skeletal muscle of healthy male individuals during normal human aging. We predominantly observed hypermethylation throughout the genome within the aged group as compared to the young subjects. Differentially methylated CpG (dmCpG) nucleotides tend to arise intragenically and are underrepresented in promoters and are overrepresented in the middle and 3' end of genes. The intragenic methylation changes are overrepresented in genes that guide the formation of the junction of the motor neuron and myofibers. We report a low level of correlation of gene expression from previous studies of aged muscle with our current analysis of DNA methylation status. For those genes that had both changes in methylation and gene expression with age, we observed a reverse correlation, with the exception of intragenic hypermethylated genes that were correlated with an increased gene expression. We suggest that a minimal number of dmCpG sites or select sites are required to be altered in order to correlate with gene expression changes. Finally, we identified 500 dmCpG sites that perform well in discriminating young from old samples. Our findings highlight epigenetic links between aging postmitotic skeletal muscle and DNA methylation.

SOD2 in mitochondrial dysfunction and neurodegeneration.

The brain is a highly metabolically active tissue that critically relies on oxidative phosphorylation as a means for maintaining energy. One result of this process is the production of potentially damaging radicals such as the superoxide anion (O2(-)). Superoxide has the capacity to damage components of the electron transport chain and other cellular constituents. Eukaryotic systems have evolved defenses against such damaging moieties, the chief member of which is superoxide dismutase (SOD2), an enzyme that efficiently converts superoxide to the less reactive hydrogen peroxide (H2O2), which can freely diffuse across the mitochondrial membrane. Loss of SOD2 activity can result in numerous pathological phenotypes in metabolically active tissues, particularly within the central nervous system. We review SOD2's potential involvement in the progression of neurodegenerative diseases such as stroke and Alzheimer and Parkinson diseases, as well as its potential role in "normal" age-related cognitive decline. We also examine in vivo models of endogenous oxidative damage based upon the loss of SOD2 and associated neurological phenotypes in relation to human neurodegenerative disorders.

Late-life rapamycin treatment reverses age-related heart dysfunction.

Rapamycin has been shown to extend lifespan in numerous model organisms including mice, with the most dramatic longevity effects reported in females. However, little is known about the functional ramifications of this longevity-enhancing paradigm in mammalian tissues. We treated 24-month-old female C57BL/6J mice with rapamycin for 3 months and determined health outcomes via a variety of noninvasive measures of cardiovascular, skeletal, and metabolic health for individual mice. We determined that while rapamycin has mild transient metabolic effects, there are significant benefits to late-life cardiovascular function with a reversal or attenuation of age-related changes in the heart. RNA-seq analysis of cardiac tissue after treatment indicated inflammatory, metabolic, and antihypertrophic expression changes in cardiac tissue as potential mechanisms mediating the functional improvement. Rapamycin treatment also resulted in beneficial behavioral, skeletal, and motor changes in these mice compared with those fed a control diet. From these findings, we propose that late-life rapamycin therapy not only extends the lifespan of mammals, but also confers functional benefits to a number of tissues and mechanistically implicates an improvement in contractile function and antihypertrophic signaling in the aged heart with a reduction in age-related inflammation.

Single cell gene expression profiling of cortical osteoblast lineage cells.

In tissues with complex architectures such as bone, it is often difficult to purify and characterize specific cell types via molecular profiling. Single cell gene expression profiling is an emerging technology useful for characterizing transcriptional profiles of individual cells isolated from heterogeneous populations. In this study we describe a novel procedure for the isolation and characterization of gene expression profiles of single osteoblast lineage cells derived from cortical bone. Mixed populations of different cell types were isolated from adult long bones of C57BL/6J mice by enzymatic digestion, and subsequently subjected to FACS to purify and characterize osteoblast lineage cells via a selection strategy using antibodies against CD31, CD45, and alkaline phosphatase (AP), specific for mature osteoblasts. The purified individual osteoblast lineage cells were then profiled at the single cell level via nanofluidic PCR. This method permits robust gene expression profiling on single osteoblast lineage cells derived from mature bone, potentially from anatomically distinct sites. In conjunction with this technique, we have also shown that it is possible to carry out single cell profiling on cells purified from fixed and frozen bone samples without compromising the gene expression signal. The latter finding means the technique can be extended to biopsies of bone from diseased individuals. Our approach for single cell expression profiling provides a new dimension to the transcriptional profile of the primary osteoblast lineage population in vivo, and has the capacity to greatly expand our understanding of how these cells may function in vivo under normal and diseased states.

No consistent bioenergetic defects in presynaptic nerve terminals isolated from mouse models of Alzheimer's disease.

Depressed cortical energy supply and impaired synaptic function are predominant associations of Alzheimer's disease (AD). To test the hypothesis that presynaptic bioenergetic deficits are associated with the progression of AD pathogenesis, we compared bioenergetic variables of cortical and hippocampal presynaptic nerve terminals (synaptosomes) from commonly used mouse models with AD-like phenotypes (J20 age 6 months, Tg2576 age 16 months, and APP/PS age 9 and 14 months) to age-matched controls. No consistent bioenergetic deficiencies were detected in synaptosomes from the three models; only APP/PS cortical synaptosomes from 14-month-old mice showed an increase in respiration associated with proton leak. J20 mice were chosen for a highly stringent investigation of mitochondrial function and content. There were no significant differences in the quality of the synaptosomal preparations or the mitochondrial volume fraction. Furthermore, respiratory variables, calcium handling, and membrane potentials of synaptosomes from symptomatic J20 mice under calcium-imposed stress were not consistently impaired. The recovery of marker proteins during synaptosome preparation was the same, ruling out the possibility that the lack of functional bioenergetic defects in synaptosomes from J20 mice was due to the selective loss of damaged synaptosomes during sample preparation. Our results support the conclusion that the intrinsic bioenergetic capacities of presynaptic nerve terminals are maintained in these symptomatic AD mouse models.

Proteogenomics of synaptosomal mitochondrial oxidative stress.

Oxidative stress is frequently implicated in the pathology of neurodegenerative disease. The chief source of this stress is mitochondrial respiration, via the passage of reducing equivalents through the respiratory chain resulting in a small but potentially pathological production of superoxide. The superoxide that is produced during normal respiration is primarily detoxified within the mitochondria by superoxide dismutase 2 (Sod2), a key protein for maintaining mitochondrial function. Mitochondria are distributed throughout the soma of neurons, as well as along neuronal processes and at the synaptic terminus. This distribution of potentially independent mitochondria throughout the neuron, at distinct subcellular locations, allows for the possibility of regional subcellular deficits in mitochondrial function. There has been increasing interest in the quantification and characterization of messages and proteins at the synapse, because of its importance in neurodegenerative disease, most notably Alzheimer disease. Here, we report the transcriptomic and proteomic changes that occur in synaptosomes from frontal cortices of Sod2 null mice. Constitutively Sod2 null mice were differentially dosed with the synthetic catalytic antioxidant EUK-189, which can extend the life span of these mice, as well as uncovering or preventing neurodegeneration due to endogenous oxidative stress. This approach facilitated insight into the quantification of trafficked messages and proteins to the synaptosome. We used two complementary methods to investigate the nature of the synaptosome under oxidative stress: either whole-genome gene expression microarrays or mass spectrometry-based proteomics using isobaric tagging for relative and absolute quantitation of proteins. We characterized the relative enrichment of gene ontologies at both gene and protein expression levels that occurs from mitochondrial oxidative stress in the synaptosome, which may lead to new avenues of investigation in understanding the regulation of synaptic function in normal and diseased states. As a result of using these approaches, we report for the first time an activation of the mTOR pathway in synaptosomes isolated from Sod2 null mice, confirmed by an upregulation of the phosphorylation of 4E-BP1.

Mitochondrial oxidative stress caused by Sod2 deficiency promotes cellular senescence and aging phenotypes in the skin.

Cellular senescence arrests the proliferation of mammalian cells at risk for neoplastic transformation, and is also associated with aging. However, the factors that cause cellular senescence during aging are unclear. Excessive reactive oxygen species (ROS) have been shown to cause cellular senescence in culture, and accumulated molecular damage due to mitochondrial ROS has long been thought to drive aging phenotypesin vivo. Here, we test the hypothesis that mitochondrial oxidative stress can promote cellular senescence in vivo and contribute to aging phenotypes in vivo, specifically in the skin. We show that the number of senescent cells, as well as impaired mitochondrial (complex II) activity increase in naturally aged mouse skin. Using a mouse model of genetic Sod2 deficiency, we show that failure to express this important mitochondrial anti-oxidant enzyme also impairs mitochondrial complex II activity, causes nuclear DNA damage, and induces cellular senescence but not apoptosis in the epidermis. Sod2 deficiency also reduced the number of cells and thickness of the epidermis, while increasing terminal differentiation. Our results support the idea that mitochondrial oxidative stress and cellular senescence contribute to aging skin phenotypes in vivo.

Impaired spare respiratory capacity in cortical synaptosomes from Sod2 null mice.

Presynaptic nerve terminals require high levels of ATP for the maintenance of synaptic function. Failure of synaptic mitochondria to generate adequate ATP has been implicated as a causative event preceding the loss of synaptic networks in neurodegenerative disease. Endogenous oxidative stress has often been postulated as an etiological basis for this pathology, but has been difficult to test in vivo. Inactivation of the superoxide dismutase gene (Sod2) encoding the chief defense enzyme against mitochondrial superoxide radicals results in neonatal lethality. However, intervention with an SOD mimetic extends the life span of this model and uncovers a neurodegenerative phenotype providing a unique model for the examination of in vivo oxidative stress. We present here studies on synaptic termini isolated from the frontal cortex of Sod2 null mice demonstrating impaired bioenergetic function as a result of mitochondrial oxidative stress. Cortical synaptosomes from Sod2 null mice demonstrate a severe decline in mitochondrial spare respiratory capacity in response to physiological demand induced by mitochondrial respiratory chain uncoupling with FCCP or by plasma membrane depolarization induced by 4-aminopyridine treatment. However, Sod2 null animals compensate for impaired oxidative metabolism in part by the Pasteur effect allowing for normal neurotransmitter release at the synapse, setting up a potentially detrimental energetic paradigm. The results of this study demonstrate that high-throughput respirometry is a facile method for analyzing specific regions of the brain in transgenic models and can uncover bioenergetic deficits in subcellular regions due to endogenous oxidative stress.

Single cell transcriptional profiling of adult mouse cardiomyocytes.

While numerous studies have examined gene expression changes from homogenates of heart tissue, this prevents studying the inherent stochastic variation between cells within a tissue. Isolation of pure cardiomyocyte populations through a collagenase perfusion of mouse hearts facilitates the generation of single cell microarrays for whole transcriptome gene expression, or qPCR of specific targets using nanofluidic arrays. We describe here a procedure to examine single cell gene expression profiles of cardiomyocytes isolated from the heart. This paradigm allows for the evaluation of metrics of interest which are not reliant on the mean (for example variance between cells within a tissue) which is not possible when using conventional whole tissue workflows for the evaluation of gene expression (Figure 1). We have achieved robust amplification of the single cell transcriptome yielding micrograms of double stranded cDNA that facilitates the use of microarrays on individual cells. In the procedure we describe the use of NimbleGen arrays which were selected for their ease of use and ability to customize their design. Alternatively, a reverse transcriptase - specific target amplification (RT-STA) reaction, allows for qPCR of hundreds of targets by nanofluidic PCR. Using either of these approaches, it is possible to examine the variability of expression between cells, as well as examining expression profiles of rare cell types from within a tissue. Overall, the single cell gene expression approach allows for the generation of data that can potentially identify idiosyncratic expression profiles that are typically averaged out when examining expression of millions of cells from typical homogenates generated from whole tissues.