CircSOD2: A Novel Regulator for Smooth Muscle Proliferation and Neointima Formation

OBJECTIVE

Vascular smooth muscle cell (SMC) proliferation contributes to neointima formation following vascular injury. Circular RNA-a novel type of noncoding RNA with closed-loop structure-exhibits cell- and tissue-specific expression patterns. However, the role of circular RNA in SMC proliferation and neointima formation is largely unknown. The objective of this study is to investigate the role and mechanism of circSOD2 in SMC proliferation and neointima formation. Approach and Results: Circular RNA profiling of human aortic SMCs revealed that PDGF (platelet-derived growth factor)-BB up- and downregulated numerous circular RNAs. Among them, circSOD2, derived from back-splicing event of SOD2 (superoxide dismutase 2), was significantly enriched. Knockdown of circSOD2 by short hairpin RNA blocked PDGF-BB-induced SMC proliferation. Inversely, circSOD2 ectopic expression promoted SMC proliferation. Mechanistically, circSOD2 acted as a sponge for miR-206, leading to upregulation of NOTCH3 (notch receptor 3) and NOTCH3 signaling, which regulates cyclin D1 and CDK (cyclin-dependent kinase) 4/6. In vivo studies showed that circSOD2 was induced in neointima SMCs in balloon-injured rat carotid arteries. Importantly, knockdown of circSOD2 attenuated injury-induced neointima formation along with decreased neointimal SMC proliferation.

CONCLUSIONS

CircSOD2 is a novel regulator mediating SMC proliferation and neointima formation following vascular injury. Therefore, circSOD2 could be a potential therapeutic target for inhibiting the development of proliferative vascular diseases.

Use of Becaplermin for nondiabetic ulcers: pyoderma gangrenosum and calciphylaxis

Large difficult to heal ulcers of various etiologies carry a high morbidity and mortality rate. Becaplermin is a recombinant platelet-derived growth factor approved for treatment of diabetic ulcers. In this two-case series, we report the use of becaplermin in the treatment of ulcers due to (i) calciphylaxis, an often fatal condition resulting from systemic calcification and thrombosis of vessels and (ii) pyoderma gangrenosum (PG), a neutrophilic dermatosis. We also report that topical collagenase worsened PG ulcers, consistent with pathergy. Becaplermin can be used to help treat ulcers resulting from calciphylaxis and PG. These encouraging results lend support for the utilization of becaplermin in the treatment of nondiabetic chronic ulcers of various etiologies.

A review of becaplermin gel in the treatment of diabetic neuropathic foot ulcers

Diabetic neuropathic foot ulcers represent a serious health care burden to patients and to society. While the management of chronic diabetic foot ulcers has improved in recent years, it remains a frustrating problem for a variety of clinicians. This review examines the scientific underpinnings supporting the use of becaplermin (Regranex((R)); Ortho-McNeil Pharmaceutical, Raritan, NJ), or recombinant human platelet-derived growth factor (rhPDGF-BB), in diabetic forefoot wounds. An emphasis is placed upon proper medical and surgical care of diabetic foot wounds, as multiple studies have demonstrated that the success of this growth factor in accelerating healing is ultimately dependent on proper ulcer care. A focus on the cost-effectiveness of this form of therapy in the treatment of diabetic foot ulcers is also outlined.

Becaplermin gel in the treatment of diabetic neuropathic foot ulcers

Diabetic foot ulcers remain a major cause of morbidity. Significant progress has been accomplished in ulcer healing by improved management of both ischemia and neuropathy in the diabetic foot. Nevertheless, there is a vital need for further improvement. Becaplermin gel represents an important therapeutic advance for diabetic neuropathic foot ulcers with adequate blood supply. Randomized controlled trials have shown that it is effective in increasing healing rates. However, this efficacy has not translated to positive clinical experience, and the drug is not widely used. Moreover, becaplermin is an expensive medication. Even though it has repeatedly been estimated as cost-effective, its high cost may be prohibitive for some clinicians, especially in developing countries. Clearly, further work is needed to clarify whether use of becaplermin is justified in everyday clinical practice. Future research also needs to assess the potential room for improvement with becaplermin, for instance by combination with other growth factors or by exploring alternative modes of drug delivery.