Lower extremity Peripheral Vascular Disease (PAD) affects ~8-12 million adults in the US, and is a major cause of morbidity and mortality, with risk of cardiovascular mortality equivalent to that of coronary artery disease. Despite this, there are no specific medical treatments to improve blood flow to the limbs, and no diagnostic test for early detection or risk stratification of PAD. The tissue adaptive response to ischemia involves changes in gene expression in multiple pathways. Micro- RNAs (miRS) have been identified to be powerful regulators of gene expression, specifically in the context of tissue injury/ischemia. MiRs have great potential as therapeutic agents due to their ease of synthesis, stability, and ability of single miR to regulate several genes within a pathway. In addition, miRs are also found in the serum/plasma and are remarkably protected from RNAse degradation. As such, they have great potential for diagnostic and/or prognostic markers. The overall goal of this proposed research plan is to identify miRs with potential for use as biomarkers or therapeutic targets/agents in PAD, and to understand their mechanism(s) of actions(s). This proposal is designed to accomplish this goal using three complementary hypotheses-driven aims built on collaborations with established investigators.
The first aim i s designed to test the hypothesis tha cell-free miRs serve as paracrine factors in PAD. Using cell culture models, we will sequentially determine whether release of miRs from endothelial and muscle cells is a regulated, non-random process under different severities and durations of hypoxia. We will then test if this process is altered by established factors that modulate the extent of injury to ischemia, such as hyperglycemia. Lastly, we will test for paracrine effects of these cell free miRs on cellular function.
The second aim i s designed to test the hypothesis that circulating miRs in serum/plasma can be used as diagnostic/prognostic markers for PAD. This will be tested using existing serum samples from patients with varying severities of PAD, and selected miRs identified as clinically relevant will be checked for associations with the existing clinical outcomes database. Lastly, based on preliminary data, the third aim is designed to test the hypothesis that concomitant downregulation of antiangiogenic miR-222 and upregulation of pro-angiogenic miR-221 will improve limb perfusion and recovery from hind-limb ischemia in a mouse model of PAD. Together, the results from the proposed aims will help identify micro-RNAs that can be used as potential therapeutic tools or targets for patients with PAD. In addition, this will help identify circulating micro-RNAs that may have diagnostic/prognostic potential for patients with PAD.
Lower extremity peripheral vascular disease (PAD) affects ~8-10 million Americans. The major problem in PAD is lack of blood supply to the legs, which results in leg pain during walking or leg pain at rest with or without ulcers. Patients with rest pin have a 25-40% risk of major amputation in six months, and an annual mortality risk as high as 20%. Despite a prevalence and mortality similar to that of coronary artery disease, the field of PAD has been understudied. There is no definite treatment to improve blood flow to the diseased legs, and no bio-marker to aid in early diagnosis or risk stratification for patients with PAD. This study will seek to better understand the modulators of PAD, and to investigate for potential bio-markers and/or prognostic markers for PAD. The first aim will investigate: 'How do cells regulate micro-RNAs, key modulators of gene expression in the context of peripheral arterial disease (PAD)'? We will use cell culture models to simulate elements of PAD to address this. The second aim will investigate: 'Are there any micro-RNAs that are differentially expressed in the blood of patients with PAD versus controls, or in patients with varying severity of PAD?' This will enable us to identify bio-markers(s) for early diagnosis of, and/or risk stratification in PAD. In addition, this may give us new targets/tools to modulate outcomes in PAD. The final aim will investigate the therapeutic potential of a pair of micro-RNAs that has shown to regulate blood vessel formation in preliminary studies in our lab.
| Hazarika, Surovi; Annex, Brian H (2017) Circulating micro-RNAs as biomarkers of coronary artery disease: is it ready for primetime or still a work in progress? Ann Transl Med 5:10 |
| Hazarika, Surovi; Annex, Brian H (2017) Biomarkers and Genetics in Peripheral Artery Disease. Clin Chem 63:236-244 |
