The Mechanism of In-Stent Restenosis in Radius Stent-An Experimental Porcine Study-

Intravascular ultrasound analysis of small vessel lesions treated with the Sparrow coronary stent system: results of the CARE II trial

OBJECTIVES

The aim of this study was to evaluate the Sparrow sirolimus-eluting stent (Sparrow-SES) against the Sparrow bare-metal stent (Sparrow-BMS) and conventional balloon-expandable bare-metal stent (BMS: Driver/Micro-Driver stent, Medtronic Vascular, Santa Rosa, CA).

BACKGROUND

The Sparrow stent (Biosensors International, Singapore) consists of a guide wire-based, self-expandable, ultra-thin nitinol stent. The performance of this device with sirolimus in a fully biodegradable polymer has not been determined.

METHODS

A total of 74 patients were included in this intravascular ultrasound (IVUS) sub-study of the CARE II trial, which was a prospective, randomized, multicenter trial in the treatment of single de novo native coronary artery lesions in vessels ranging from 2.0 mm to 2.75 mm in diameter (Sparrow-SES: n = 31, Sparrow-BMS: n = 22, BMS: n = 21).

RESULTS

Stent volume index (VI) was significantly increased 8-month later in Sparrow-SES and Sparrow-BMS, but not in BMS (4.0 ± 1.0 to 4.6 ± 1.0 mm(3) /mm, p<0.0001, 4.0 ± 0.6 to 4.4 ± 0.8 mm(3) /mm, p<0.05, and 5.2 ± 1.0 to 5.1 ± 0.9 mm(3) /mm, p=0.421, respectively). % neointimal obstruction in Sparrow-SES was significantly smaller than those in Sparrow-BMS and BMS at follow-up (17.6 ± 9.4 vs. 36.2 ± 13.8 and 39.9 ± 11.1%, p<0.001). Sparrow-SES showed a mean 15% stent expansion and good suppression of neointimal proliferation, resulting in a significantly lower percentage of change in lumen VI during follow-up period (Sparrow-SES: -6.2 ± 16.2%, Sparrow-BMS: -30.4 ± 11.6%, BMS: -40.4 ± 10.0%, p<0.001).

CONCLUSIONS

The self-expanding Sparrow-SES demonstrated chronic stent expansion, good suppression of neointimal proliferation and resulted in a more preserved lumen in stented small vessels compared with the Sparrow-BMS and conventional balloon expandable BMS.

Tenascin C promiscuously binds growth factors via its fifth fibronectin type III-like domain

Tenascin C (TNC) is an extracellular matrix protein that is upregulated during development as well as tissue remodeling. TNC is comprised of multiple independent folding domains, including 15 fibronectin type III-like (TNCIII) domains. The fifth TNCIII domain (TNCIII5) has previously been shown to bind heparin. Our group has shown that the heparin-binding fibronectin type III domains of fibronectin (FNIII), specifically FNIII12–14, possess affinity towards a large number of growth factors. Here, we show that TNCIII5 binds growth factors promiscuously and with high affinity. We produced recombinant fragments of TNC representing the first five TNCIII repeats (TNCIII1–5), as well as subdomains, including TNCIII5, to study interactions with various growth factors. Multiple growth factors of the platelet-derived growth factor (PDGF) family, the fibroblast growth factor (FGF) family, the transforming growth factor beta (TGF-β) superfamily, the insulin-like growth factor binding proteins (IGF-BPs), and neurotrophins were found to bind with high affinity to this region of TNC, specifically to TNCIII5. Surface plasmon resonance was performed to analyze the kinetics of binding of TNCIII1–5 with TGF-β1, PDGF-BB, NT-3, and FGF-2. The promiscuous yet high affinity of TNC for a wide array of growth factors, mediated mainly by TNCIII5, may play a role in multiple physiological and pathological processes involving TNC.

The role of tenascin C in cardiovascular disease

The extracellular matrix protein tenascin C (TnC) is expressed in a variety of embryonic tissues, but its expression in adult arteries is co-incident with sites of vascular disease. TnC expression has been linked to the development and complications of intimal hyperplasia, pulmonary artery hypertension, atherosclerosis, myocardial infarction, and heart failure. This review identifies the growing collection of evidence linking TnC with cardiovascular disease development. The transient upregulation of this extracellular matrix protein at sites of vascular disease could provide a means to target TnC in the development of diagnostics and new therapies. Studies in TnC-deficient mice have implicated this protein in the development of intimal hyperplasia. Further animal and human studies are required to thoroughly assess the role of TnC in some of the other pathologies it has been linked with, such as atherosclerosis and pulmonary hypertension. Large population studies are also warranted to clarify the diagnostic value of this extracellular matrix protein in cardiovascular disease, for example by targeting its expression using radiolabelled antibodies or measuring circulating concentrations of TnC.