INKILN is a Novel Long Noncoding RNA Promoting Vascular Smooth Muscle Inflammation via Scaffolding MKL1 and USP10

Zhang et al., Circulation, 2023 asked what turns a vascular smooth muscle cell inflammatory, and found a long non-coding RNA that exists only in humans. Bulk RNA sequencing of differentiated human vascular smooth muscle cells produced a transcript the authors named INKILN, for inflammatory MKL1 interacting long noncoding RNA. It is low in contractile cells and raised in human atherosclerosis and abdominal aortic aneurysm. Mechanistically it binds and stabilises MKL1, the transcription factor that drives smooth muscle inflammation through the p65 pathway, by keeping it away from ubiquitin-dependent degradation via the deubiquitinase USP10.

Most of the loss-of-function work used small interfering RNA, and the authors wanted a second method that works by a different route before believing it. That is where the antisense oligonucleotide comes in. An AUMlnc antisense oligonucleotide against INKILN was used in growing human aortic and human coronary artery smooth muscle cells, against a control oligonucleotide, with three biological replicates in each cell type. It lowered the same proinflammatory transcripts, INKILN itself along with IL6, IL8, CXCL1 and CXCL5.

The authors state the limit of that result themselves: the effect was smaller than with the small interfering RNA, which they attribute to lower knockdown efficiency. The oligonucleotide was transfected, at 100 nM with a lipid reagent, and was not added to the medium on its own, so nothing here is evidence of self-delivery. The supplier is named, in the supplemental Expanded Methods rather than in the article itself. The rest of the paper went on to a humanized bacterial artificial chromosome transgenic mouse, in which INKILN worsened neointimal formation after carotid artery ligation, with no oligonucleotide used in that arm.