Understanding the role of long non-coding RNA (LncRNA) in vascular pathology

[摘要] Coronary heart disease is a major cause of morbidity and mortality in the Western society. In the case of severe atherosclerosis, percutaneous intervention and coronary bypass grafting remain the preferred form of surgical treatment. However, the patency of both these treatments is limited and several bypass grafts and stents fail due to neointimal formation and in stent restenosis attributable to the proliferation of VSMCs. The resultant luminal renarrowing may manifest clinically with the return of symptoms such as chest pain or shortness of breath and ultimately requires further surgical intervention. Unfortunately, current antiproliferative therapies to inhibit VSMC proliferation have off target effects and can inhibit vessel re-endothelialisation resulting in thrombus formation. As such, novel therapies that specifically target VSMC proliferation but do not affect endothelial growth are urgently required. Long non-coding RNA (lncRNA) are transcripts >200 nucleotides that have been shown to bind DNA, RNA and proteins in order to exert their function. To date a few lncRNAs have been identified that control key aspects of VSMC phenotype, including contraction, proliferation, migration and apoptosis, however, very little is known as to the role of lncRNA in the proliferative and inflammatory phenotype associated with this phenotypic switching. It was therefore hypothesised that lncRNA may be dysregulated in the setting of inflammatory and proliferative vascular pathology and may provide novel therapies to counteract VSMC proliferation and hence vascular disease. The project sought to identify lncRNA expression in quiescent, non-proliferating human saphenous vein (HSV) SMCs, and HSVSMCs that had been treated with the IL1α cytokine and PDGF growth factor. This cytokine and growth factor pair have been implicated in the synergistic activation of the NF-κB transcription factor and in the control of vascular diseases including in stent restenosis, neo intimal formation and atherosclerosis. Using RNA-sequencing, >300 lncRNAs were identified whose expression was altered in HSVSMCs following stimulation with IL1α and PDGF. These lncRNA exhibited distinct expression patterns in a tissue cohort and all showed enrichment in vascular SMCs from either an arterial or venous lineages. Experiments focused on a novel lncRNA (Ensembl: RP11-94A24.1) which showed specific expression in HSVSMCs following treatment but no expression in endothelial cells. This lncRNA was termed smooth muscle induced lncRNA enhances replication (SMILR). Following stimulation, SMILR expression was increased in both the nucleus and cytoplasm, and was detected in conditioned media from dual stimulated HSVSMCs. Furthermore, knockdown of SMILR markedly reduced cell proliferation. Mechanistically, it was noted that expression of genes proximal to SMILR were also altered by IL1α/PDGF treatment possibly indicating that these two genes are under the same promoter control, and HAS2 expression was reduced by SMILR knockdown. Additionally the proliferation of HSVSMCs was increased in a dose dependent manner following administration of a lentivirus containing the full SMILR transcript, confirming the knockdown data. In human samples, increased expression of SMILR was detected in plaque compared to adjacent non-plaque sections by qRT-PCR and following on from the detection of SMILR in conditioned media, SMILR was also detected in plasma samples from patients with inflammatory CVD. Interestingly, the levels of SMILR correlated with plasma C-reactive protein, a current biomarker capable of detecting atherosclerosis progression in patients. These results identify SMILR as a driver of VSMC proliferation and suggest that modulation of SMILR may be a novel therapeutic strategy to reduce vascular pathologies. Additionally the detection of SMILR in plasma highlights the possibility that this lncRNA may have the potential as a biomarker of vascular disease. However, further large cohort studies are required to identify this potential clinical role.

[发布机构] University:University of Glasgow;Department:Institute of Cardiovascular and Medical Sciences

[关键词] Long non-coding RNA, cardiovascular, vascular disease, atherosclerosis, smooth muscle cell.