A Monochrome Multiplex Real-Time Quantitative PCR Assay for the Measurement of Mitochondrial DNA Content

Extracellular Vesicle- and Mitochondria-Based Targeting of Non-Small Cell Lung Cancer Response to Radiation: Challenges and Perspectives

During the cell life cycle, extracellular vesicles (EVs) transport different cargos, including organelles, proteins, RNAs, DNAs, metabolites, etc., that influence cell proliferation and apoptosis in recipient cells. EVs from metastatic cancer cells remodel the extracellular matrix and cells of the tumor microenvironment (TME), promoting tumor invasion and metastatic niche preparation. Although the process is not fully understood, evidence suggests that EVs facilitate genetic material transfer between cells. In the context of NSCLC, EVs can mediate intercellular mitochondrial (Mt) transfer, delivering mitochondria organelle (MtO), mitochondrial DNA (mtDNA), and/or mtRNA/proteinaceous cargo signatures (MtS) through different mechanisms. On the other hand, certain populations of cancer cells can hijack the MtO from TME cells mainly by using tunneling nanotubes (TNTs). This transfer aids in restoring mitochondrial function, benefiting benign cells with impaired metabolism and enabling restoration of their metabolic activity. However, the impact of transferring mitochondria versus transplanting intact mitochondrial organelles in cancer remains uncertain and the subject of debate. Some studies suggest that EV-mediated mitochondria delivery to cancer cells can impact how cancer responds to radiation. It might make the cancer more resistant or more sensitive to radiation. In our review, we aimed to point out the current controversy surrounding experimental data and to highlight new paradigm-shifting modalities in radiation therapy that could potentially overcome cancer resistance mechanisms in NSCLC.

Simultaneous assessment of mitochondrial DNA copy number and nuclear epigenetic age towards predictive models of development and aging

OBJECTIVE

Mitochondrial dysfunction and nuclear epigenetic alterations, two hallmarks of aging, are associated with aberrant development and complex disease risk. Here, we report a method for the simultaneous assessment of mitochondrial DNA copy number (mtDNA-CN) and DNA methylation age (DNAm age) from the same DNA extraction using quantitative polymerase chain reaction (qPCR) and array data, respectively.

RESULT

We present methods for the concurrent estimation of mtDNA-CN and DNAm age from the same DNA samples. This includes qPCR to estimate mtDNA-CN, representing the number of circular mitochondrial genomes in a cell, and DNA methylation microarray data to estimate the epigenetic age of an individual. Further, we provide a method for the combination of these metrics into a shared metric termed 'mtEpiAge'. This approach provides a valuable tool for exploring the interplay between mitochondrial dysfunction and nuclear epigenetic alterations, and their associations with disease and aging.

Mitochondrial DNA Copy Number and Heteroplasmy in Monozygotic Twins Discordant for Schizophrenia

Schizophrenia (SZ) is a severe, complex, and common mental disorder with high heritability (80%), an adult age of onset, and high discordance (∼50%) in monozygotic twins (MZ). Extensive studies on familial and non-familial cases have implicated a number of segregating mutations and de novo changes in SZ that may include changes to the mitochondrial genome. Yet, no single universally causal variant has been identified, highlighting its extensive genetic heterogeneity. This report specifically focuses on the assessment of changes in the mitochondrial genome in a unique set of monozygotic twins discordant (MZD) for SZ using blood. Genomic DNA from six pairs of MZD twins and two sets of parents (N = 16) was hybridized to the Affymetrix Human SNP Array 6.0 to assess mitochondrial DNA copy number (mtDNA-CN). Whole genome sequencing (WGS) and quantitative polymerase chain reaction (qPCR) was performed for a subset of MZD pairs and their parents and was also used to derive mtDNA-CN estimates. The WGS data were further analyzed to generate heteroplasmy (HP) estimates. Our results show that mtDNA-CN estimates for within-pair and mother-child differences were smaller than comparisons involving unrelated individuals, as expected. MZD twins showed discordance in mtDNA-CN estimates and displayed concordance in directionality of differences for mtDNA-CN across all technologies. Further, qPCR performed better than Affymetrix in estimating mtDNA-CN based on relatedness. No reliable differences in HP were detected between MZD twins. The within-MZD differences in mtDNA-CN observed represent postzygotic somatic changes that may contribute to discordance of MZ twins for diseases, including SZ.

Dolutegravir-containing HIV therapy reversibly alters mitochondrial health and morphology in cultured human fibroblasts and peripheral blood mononuclear cells

OBJECTIVES

Given the success of combination antiretroviral therapy (cART) in treating HIV viremia, drug toxicity remains an area of interest in HIV research. Despite newer integrase strand transfer inhibitors (InSTIs), such as dolutegravir (DTG) and raltegravir (RAL), having excellent clinical tolerance, there is emerging evidence of off-target effects and toxicities. Although limited in number, recent reports have highlighted the vulnerability of mitochondria to these toxicities. The aim of the present study is to quantify changes in cellular and mitochondrial health following exposure to current cART regimens at pharmacological concentrations. A secondary objective is to determine whether any cART-associated toxicities would be modulated by human telomerase reverse transcriptase (hTERT).

METHODS

We longitudinally evaluated markers of cellular (cell count, apoptosis), and mitochondrial health [mitochondrial reactive oxygen species (mtROS), membrane potential (MMP) and mass (mtMass)] by flow cytometry in WI-38 human fibroblast with differing hTERT expression/localization and peripheral blood mononuclear cells. This was done after 9 days of exposure to, and 6 days following the removal of, seven current cART regimens, including three that contained DTG. Mitochondrial morphology was assessed by florescence microscopy and quantified using a recently developed deep learning-based pipeline.

RESULTS

Exposure to DTG-containing regimens increased apoptosis, mtROS, mtMass, induced fragmented mitochondrial networks compared with non-DTG-containing regimens, including a RAL-based combination. These effects were unmodulated by telomerase expression. All effects were fully reversible following removal of drug pressure.

CONCLUSION

Taken together, our observations indicate that DTG-containing regimens negatively impact cellular and mitochondrial health and may be more toxic to mitochondria, even among the generally well tolerated InSTI-based cART.

Mitochondrial DNA copy number, metabolic syndrome, and insulin sensitivity: Insights from the Sugar, Hypertension, and Physical Exercise studies

Mitochondrial DNA copy number (mtDNA-CN) measured in blood has been associated with many aging-related diseases, with higher mtDNA-CN typically associated with lower disease risk. Exercise training is an excellent preventative tool against aging-related disorders and has been shown to increase mitochondrial function in muscle. Using the Sugar, Hypertension, and Physical Exercise cohorts (N = 105), we evaluated the effect of 6-months of exercise intervention on mtDNA-CN measured in blood. Although there was no significant relationship between exercise intervention and mtDNA-CN change (P = 0.29), there was a nominally significant association between mtDNA-CN and metabolic syndrome (P = 0.04), which has been seen in previous literature. We also identified a nominally significant association between higher mtDNA-CN and higher insulin sensitivity (P = 0.02).

Noninvasive Risk Score to Screen for Pulmonary Hypertension With Elevated Pulmonary Vascular Resistance in Diseases of Chronic Volume Overload

Volume overload promotes pulmonary hypertension (PH) through pulmonary venous hypertension. However, PH with elevated pulmonary vascular resistance (hereafter PH-PVR) may develop in patients with diseases of volume overload, such as heart failure or chronic kidney disease (CKD). In such cases, volume management alone may be insufficient to slow PH progression. An accurate, noninvasive method to screen for PH-PVR in these diseases would facilitate early targeted therapy. We integrated invasive hemodynamic and echocardiography data collected from a single-center clinical cohort and identified patients with CKD or heart failure at the time of assessment. We applied penalized regression to derive a risk score of clinical parameters and echocardiography data associated with PH-PVR and categorized patients into low- (≤5 points), intermediate- (6-10 points), or high-risk (>10 points) groups. Using an internal validation strategy, we evaluated the ability of this risk score to predict PH-PVR and determined the association of this risk classification with 3-year all-cause mortality. Of 2422 patients, 42.4% had PH-PVR. In adjusted analyses, tricuspid regurgitant velocity, right ventricular function, BMI, heart rate, and hemoglobin most strongly associated with PH-PVR. The risk score significantly associated with PH-PVR (age-adjusted odds ratio 11.69 for the highest-risk group, 95% confidence interval [CI] 6.54-20.92). The high-risk group also associated with a significantly higher risk of 3-year all-cause mortality in adjusted analyses (hazard ratio 1.85, 95% CI 1.50-2.27). In conclusion, a noninvasive risk score derived from echocardiography and clinical parameters significantly associated with PH-PVR and all-cause mortality in a cohort of patients with CKD and heart failure.

Emerging methods for and novel insights gained by absolute quantification of mitochondrial DNA copy number and its clinical applications

The past thirty years have seen a surge in interest in pathophysiological roles of mitochondria, and the accurate quantification of mitochondrial DNA copy number (mCN) in cells and tissue samples is a fundamental aspect of assessing changes in mitochondrial health and biogenesis. Quantification of mCN between studies is surprisingly variable due to a combination of physiological variability and diverse protocols being used to measure this endpoint. The advent of novel methods to quantify nucleic acids like digital polymerase chain reaction (dPCR) and high throughput sequencing offer the ability to measure absolute values of mCN. We conducted an in-depth survey of articles published between 1969 -- 2020 to create an overview of mCN values, to assess consensus values of tissue-specific mCN, and to evaluate consistency between methods of assessing mCN. We identify best practices for methods used to assess mCN, and we address the impact of using specific loci on the mitochondrial genome to determine mCN. Current data suggest that clinical measurement of mCN can provide diagnostic and prognostic value in a range of diseases and health conditions, with emphasis on cancer and cardiovascular disease, and the advent of means to measure absolute mCN should improve future clinical applications of mCN measurements.

British Columbia CARMA-CHIWOS Collaboration (BCC3): protocol for a community-collaborative cohort study examining healthy ageing with and for women living with HIV

INTRODUCTION

Women living with HIV (WLWH) experience accelerated ageing and an increased risk of age-associated diseases earlier in life, compared with women without HIV. This is likely due to a combination of viral factors, gender differences, hormonal imbalance and psychosocial and structural conditions. This interdisciplinary cohort study aims to understand how biological, clinical and sociostructural determinants of health interact to modulate healthy ageing in WLWH.

METHODS AND ANALYSIS

The British Columbia Children and Women: AntiRetroviral therapy and Markers of Aging-Canadian HIV Women's Sexual and Reproductive Health Cohort Study (CARMA-CHIWOS) Collaboration (BCC3) study will enrol WLWH (n=350) and sociodemographically matched HIV-negative women (n=350) living in British Columbia. A subset of BCC3 participants will be past participants of CARMA, n≥1000 women and children living with and without HIV, 2008-2018 and/or CHIWOS, n=1422 WLWH, 2013-2018. Over two study visits, we will collect biological specimens for virus serologies, hormones and biological markers as well as administer a survey capturing demographic and sociostructural-behavioural factors. Sociodemographics, comorbidities, number and type of chronic/latent viral infections and hormonal irregularities will be compared between the two groups. Their association with biological markers and psychostructural and sociostructural factors will be investigated through multivariable regression and structural equation modelling. Retrospective longitudinal analyses will be conducted on data from past CARMA/CHIWOS participants. As BCC3 aims to follow participants as they age, this protocol will focus on the first study visits.

ETHICS AND DISSEMINATION

This study has been approved by the University of British Columbia Children's and Women's Research Ethics Board (H19-00896). Results will be shared in peer-reviewed journals, conferences and at community events as well as at www.hivhearme.ca and @HIV_HEAR_me. WLWH are involved in study design, survey creation, participant recruitment, data collection and knowledge translation. A Community Advisory Board will advise the research team throughout the study.

Daily Oral Supplementation with 60 mg of Elemental Iron for 12 Weeks Alters Blood Mitochondrial DNA Content, but Not Leukocyte Telomere Length in Cambodian Women

There is limited evidence regarding the potential risk of untargeted iron supplementation, especially among individuals who are iron-replete or have genetic hemoglobinopathies. Excess iron exposure can increase the production of reactive oxygen species, which can lead to cellular damage. We evaluated the effect of daily oral supplementation on relative leukocyte telomere length (rLTL) and blood mitochondrial DNA (mtDNA) content in non-pregnant Cambodian women (18-45 years) who received 60 mg of elemental iron as ferrous sulfate (n = 190) or a placebo (n = 186) for 12 weeks. Buffy coat rLTL and mtDNA content were quantified by monochrome multiplex quantitative polymerase chain reaction. Generalized linear mixed-effects models were used to predict the absolute and percent change in rLTL and mtDNA content after 12 weeks. Iron supplementation was not associated with an absolute or percent change in rLTL after 12 weeks compared with placebo (ß-coefficient: -0.04 [95% CI: -0.16, 0.08]; p = 0.50 and ß-coefficient: -0.96 [95% CI: -2.69, 0.77]; p = 0.28, respectively). However, iron supplementation was associated with a smaller absolute and percent increase in mtDNA content after 12 weeks compared with placebo (ß-coefficient: -11 [95% CI: -20, -2]; p = 0.02 and ß-coefficient: -11 [95% CI: -20, -1]; p= 0.02, respectively). Thus, daily oral iron supplementation for 12 weeks was associated with altered mitochondrial homeostasis in our study sample. More research is needed to understand the risk of iron exposure and the biological consequences of altered mitochondrial homeostasis in order to inform the safety of the current global supplementation policy.

Relationship of Telomere Length to Fat Redistribution in HIV

Persons with HIV demonstrate increased risk for aging-associated complications and have reduced telomere length (TL) compared with age-matched persons without HIV. Our data show that greater visceral fat is related to reduced TL in HIV, independent of age and smoking. Fat redistribution may be a relevant mediator of TL attrition in HIV.

Inverse relationship between leukocyte telomere length attrition and blood mitochondrial DNA content loss over time

Leukocyte telomere length (LTL) and whole blood mitochondrial DNA (WB mtDNA) content are aging markers impacted by chronic diseases such as human immunodeficiency virus (HIV) infection. We characterized the relationship between these two markers in 312 women ≥12 years of age living with HIV and 300 HIV-negative controls. We found no relationship between the two markers cross-sectionally. In multivariable models, age, ethnicity, HIV, and tobacco smoking were independently associated with shorter LTL, and the former three with lower WB mtDNA. Longitudinally, among a subgroup of 228 HIV participants and 68 HIV-negative controls with ≥2 biospecimens ≥1 year apart, an inverted pattern was observed between the rates of change in LTL and WB mtDNA content per year, whereby faster decline of one was associated with the preservation of the other. Furthermore, if HIV viral control was not maintained between visits, increased rates of both LTL attrition and WB mtDNA loss were observed. We describe a novel relationship between two established aging markers, whereby rates of change in LTL and WB mtDNA are inversely related. Our findings highlight the importance of maintaining HIV viral control, the complementary longitudinal relationship between the two markers, and the need to consider both in aging studies.

Elevated Blood Mitochondrial DNA in Early Life Among Uninfected Children Exposed to Human Immunodeficiency Virus and Combination Antiretroviral Therapy in utero

BACKGROUND

Combination antiretroviral therapy (cART) during pregnancy prevents vertical transmission, but many antiretrovirals cross the placenta and several can affect mitochondria. Exposure to maternal human immunodeficiency virus (HIV) and/or cART could have long-term effects on children who are HIV exposed and uninfected (CHEU). Our objective was to compare blood mitochondrial DNA (mtDNA) content in CHEU and children who are HIV unexposed and uninfected (CHUU), at birth and in early life.

METHODS

Whole-blood mtDNA content at birth and in early life (age 0-3 years) was compared cross-sectionally between CHEU and CHUU. Longitudinal changes in mtDNA content among CHEU was also evaluated.

RESULTS

At birth, CHEU status and younger gestational age were associated with higher mtDNA content. These remained independently associated with mtDNA content in multivariable analyses, whether considering all infants, or only those born at term. Longitudinally, CHEU mtDNA levels remained unchanged during the first 6 months of life, and gradually declined thereafter. A separate age- and sex-matched cross-sectional analysis (in 214 CHEU and 214 CHUU) illustrates that the difference in mtDNA between the groups remains detectable throughout the first 3 years of life.

CONCLUSION

The persistently elevated blood mtDNA content observed among CHEU represents a long-term effect, possibly resulting from in utero stresses related to maternal HIV and/or cART. The clinical impact of altered mtDNA levels is unclear.

Rate of dyslipidemia higher among women living with HIV: A comparison of metabolic and cardiovascular health in a cohort to study aging in HIV

OBJECTIVES

Combination antiretroviral therapy has largely restored the lifespan of persons living with HIV. Data suggest early comorbidities of aging in this population. Past studies focused on men; limited data exist regarding the prevalence of dyslipidaemia in women living with HIV (WLWH). We investigated the prevalence of cardiometabolic abnormalities among WLWH and HIV-negative women in the Children and Women: Antiretrovirals and Markers of Aging (CARMA) cohort, and their relationships to cellular aging markers.

METHODS

We conducted a cross-sectional analysis of nonpregnant female patients (156 WLWH and 133 HIV-negative controls, aged 12-69 years) enrolled in CARMA between 2013 and 2017. The Framingham risk score (FRS) and the prevalences of hypertension, diabetes, metabolic syndrome and dyslipideamia were determined using self-report, anthropometrics, chart review and laboratory data. Cellular aging was determined by assessing leukocyte telomere length and blood mitochondrial DNA content. Diagnoses were based on current Canadian guidelines and definitions.

RESULTS

HIV-infected status was associated with dyslipidaemia [odds ratio (OR) 2.89; 95% confidence interval (CI) 1.69-5.01], but not diabetes, higher FRS, hypertension or metabolic syndrome. The median age was 43.5 [interquartile range (IQR) 36.8-50.9] years in WLWH and 46.2 (IQR 30.3-54.9) years in HIV-negative controls. WLWH were less likely to be menopausal or use alcohol, and more often had hepatitis C virus infection or a current or past smoking history. Lower mitochondrial DNA content was associated with metabolic syndrome; no other associations were noted between cardiometabolic abnormalities and markers of cellular aging.

CONCLUSIONS

Despite their relatively young age, almost two-thirds of WLWH had dyslipidaemia, a significantly greater proportion than in controls. Strategies to address dyslipidaemia and decrease smoking rates may improve long-term outcomes among WLWH.

Platelet mtDNA content and leukocyte count influence whole blood mtDNA content

Changes in whole blood (WB) mitochondrial DNA (mtDNA) content are associated with health and disease. Platelet-derived mtDNA can confound WB mtDNA content measurements. From a sample of 44 volunteers, we show that platelet mtDNA content and platelet:leukocyte ratio are both dependent predictors of WB mtDNA content, but that platelet count itself is not. Furthermore, when platelet:leukocyte ratio increased by <2-fold ex vivo, the effect on WB mtDNA content was minimal. Altogether, this study clarifies the contribution of platelet mtDNA content rather than platelet count on WB mtDNA content measurements, and identifies defined parameters for future research on WB mtDNA content.