Role of Podocan and Wnt Pathway Regulatory Molecules in Coronary Artery Disease

Smooth muscle cells (SMC's) critically influence the clinical course of vascular disease . The close regulation of SMC migration and proliferation within the intimal space is critical in maintaining a delicate balance between insufficient and excessive atherosclerotic plaque repair . When SMC proliferation is too suppressed, the ensuing weakening of the fibrous cap can result in plaque vulnerability underlying Acute Coronary Syndrome and when SMC proliferation is excessive, intimal hyperplasia as hallmark of accelerated Coronary Artery Disease can follow such as in Restenosis post PCI. While stents have vastly improved upon the recoil and constrictive remodeling component of restenosis, the problem of accelerated intimal SMC growth has remained. The current approach of delivering stents releasing non-specific agents promoting cell death and/or inhibition of proliferation has been successful at lowering the need for recurrent vascular interventions . However, this success comes at the expense of delaying vascular healing, whose ultimate long-term clinical impact is still being evaluated. Short and long-term negative effects on the healing arterial wall such as delayed re-endothelialization, increased inflammation and enhanced thrombogenicity of drug-eluting stent (DES) are undisputed. These side effects of DES are being masked by prolonged and aggressive dual anti-platelet therapy, which is exposing patients - especially the elderly - to increased bleeding risks and complicates clinical decision-making. This problem also causes fear of too early treatment cessation, demands rigorous patient compliance and is costly. These issues are not trivial in daily clinical practice and the lack of reliable clinical predictors of restenosis precludes individualized and patient tailored stent selection.

Podocan is a protein within the Single Leucine Rich (SLR) protein family and is a previously unrecognized component of the sclerotic glomerular lesion that develops in the course of experimental HIV associated nephropathy . Its important role in regulating smooth muscle cell function via the Wnt-pathway has been recently described by the investigators of this study . It has been shown to modulate experimental arterial repair and a significantly different expression pattern has been found in coronary arterial lesions obtained by directional coronary atherectomy (DCA) from patients with restenosis compared to stable angina . These findings do suggest a possible clinical predictive role of Podocan, and the Wnt-pathway effectory molecules on the incidence of Instent Re-stenosis (ISR) and the need for Repeat Target Vessel Revascularization.

All patients who present to the cardiac cath lab for angiography for the evaluation of known or suspected CAD will be eligible for enrollment. It is expected that, based on angiographic results, participants will fall into one of four categories:

1. No CAD
2. Stable CAD, no intervention required
3. Obstructive CAD requiring intervention (angioplasty, stenting, CABG) (Not associated with acute event, such as MI)
4. Patients presenting with Acute Coronary Syndrome (ACS) In all elective/scheduled case, prior to catheterization, a peripheral blood sample will be obtained via an IV access line previously placed for the catheterization procedure. In emergent cases of ACS, blood samples will be obtained in the same manner described previously if possible. It is likely that in some cases, such as ST elevation myocardial infarction (STEMI), this will not be possible based on clinical care priorities. In these cases blood samples will be obtained within 24 hours after catheterization. These blood samples will need to be obtained via venipuncture and will be clearly labeled/recorded as being collected post-procedure. Blood samples will be frozen and stored in a -80°C freezer in the Research Institute. Samples will be batch sent to Baylor Medical Center to be tested for the presence of Wnt and Podocan molecules (Wnt-1, Wnt-3, Dkk-1, Sclerostin, WIF-1, sFRP-1, sFRP-3) by measuring circulating levels via ELISA Obstructive CAD (non-ACS) Group: It is expected that 900 stented patients will be enrolled over 18-20 months. Justification of patient numbers is derived by specific aim of attempting to establish prospective component of our study, which is the prediction of restenosis. Given a current average incidence of restenosis between 10 to 15 % (DES around 7% and BMS around 20% restenosis rate) this number should guarantee around 100 restenosis events out of 900 patients. This should give a realistic statistical chance to detect a possible clinical predictive value of our variables. Participants who are consented and sampled but who are found not to have obstructive CAD requiring stenting will be maintained separately in the study database as a control group for future analysis. The following information will be collected from the baseline angiogram:

• syntax score in order to determine the coronary atherosclerotic burden
• PCI performed during baseline angiogram? If yes - what type of stent, location Participant charts will be reviewed at 24 months post catheterization to collect covariates (like age, sex, race/ethnicity, high blood pressure, obesity, smoking and diabetes) and to monitor for the following events:
• Repeat cardiac catheterization --Re-stenosis of stent placed at baseline angiogram --Onset of new lesions
• Progression of lesions not treated at baseline angiogram
• New onset MI/ACS
• Recurrent MI/ACS
• Death due to known cardiovascular causation CS Group: The following information will be collected from the baseline angiogram:
• syntax score in order to determine the coronary atherosclerotic burden
• PCI performed during baseline angiogram? If yes - what type of stent, location Participant charts will be reviewed at 24 months post catheterization to monitor for the following events:
• Repeat cardiac catheterization --Re-stenosis of stent placed at baseline angiogram --Onset of new lesions --Progression of lesions not treated at baseline angiogram
• Recurrent MI/ACS
• Death due to known cardiovascular causation Non- Obstructive/Stable CAD Group: The following information will be collected from the baseline angiogram: -syntax score in order to determine the coronary atherosclerotic burden Participant charts will be reviewed at 24 months post catheterization to monitor for the following events:
• Repeat cardiac catheterization --Onset of new lesions --Progression of lesions not treated at baseline angiogram
• New onset MI/ACS
• Death due to known cardiovascular causation Normal Angiography (No CAD) Group: Participant charts will be reviewed at 24 months post catheterization to monitor for the following events:
• Repeat cardiac catheterization --Onset of new lesions
• Progression of lesions not treated at baseline angiogram
• New onset MI/ACS
• Death due to known cardiovascular causation Comparison with Historical Samples: The principal investigator owns a collection of historical tissue samples that have angiographically defined coronary target lesion biopsies from clinical patients with stable angina and restenosis. The technique of DCA (Directional Coronary Artherectomy), by which these samples were collected, is not clinically done anymore, preventing the investigators from collecting these samples from the current study participants. The current study participants will be grouped according to exact same clinical criteria as the historic patients and hence represent comparable clinical cohort. The expression of Podocan and Wnt effectory molecules (Wnt-1, Wnt-3, Dkk-1, Sclerostin, WIF-1, sFRP-1, sFRP-3) in coronary artery lesions obtained by Directional Coronary Artherectomy will be analyzed using immuno-histochemical staining and quantitative histo-morphometric analysis comparing restenosis with Primary Stable Coronary Artery Disease as published by the investigators (5). This comparison will allow the investigators to examine the relationship between the level of the Podocan and Wnt effectory molecules, coronary plaque physiology, and the study endpoint of disease progression as evidenced by restenosis.