Jozef Murar

Nitric oxide and nanotechnology: A novel approach to inhibit neointimal hyperplasia

OBJECTIVE Nitric oxide (NO) has been shown to inhibit neointimal hyperplasia after arterial interventions in several animal models. To date, however, NO-based therapies have not been used in the clinical arena. Our objective was to combine nanofiber delivery vehicles with NO chemistry to create a novel, more potent NO-releasing therapy that can be used clinically. Thus, the aim of this study was to evaluate the perivascular application of spontaneously self-assembling NO-releasing nanofiber gels. Our hypothesis was that this application would prevent neointimal hyperplasia. METHODS Gels consisted of a peptide amphiphile, heparin, and a diazeniumdiolate NO donor (1-[N-(3-Aminopropyl)-N-(3-ammoniopropyl)]diazen-1-ium-1,2-diolate [DPTA/NO] or disodium 1-[(2-Carboxylato)pyrrolidin-1-yl]diazen-1-ium-1,2-diolate [PROLI/NO]). Nitric oxide release from the gels was evaluated by the Griess reaction, and scanning electron microscopy confirmed nanofiber formation. Vascular smooth muscle cell (VSMC) proliferation and cell death were assessed in vitro by (3)H-thymidine incorporation and Personal Cell Analysis (PCA) system (Guava Technologies, Hayward, Calif). For the in vivo work, gels were modified by reducing the free-water content. Neointimal hyperplasia after periadventitial gel application was evaluated using the rat carotid artery injury model at 14 days (n = 6 per group). Inflammation and proliferation were examined in vivo with immunofluorescent staining against CD45, ED1, and Ki67 at 3 days (n = 2 per group), and graded by blinded observers. Endothelialization was assessed by Evans blue injection at 7 days (n = 3 per group). RESULTS Both DPTA/NO and PROLI/NO, combined with the peptide amphiphile and heparin, formed nanofiber gels and released NO for 4 days. In vitro, DPTA/NO inhibited VSMC proliferation and induced cell death to a greater extent than PROLI/NO. However, the DPTA/NO nanofiber gel only reduced neointimal hyperplasia by 45% (intima/media [I/M] area ratio, 0.45 +/- 0.07), whereas the PROLI/NO nanofiber gel reduced neointimal hyperplasia by 77% (I/M area ratio, 0.19 +/- 0.03, P < .05) vs control (injury alone I/M area ratio, 0.83 +/- 0.07; P < .05). Both DPTA/NO and PROLI/NO nanofiber gels significantly inhibited proliferation in vivo (1.06 +/- 0.30 and 0.19 +/- 0.11 vs injury alone, 2.02 +/- 0.20, P < .05), yet had minimal effect on apoptosis. Only the PROLI/NO nanofiber gel inhibited inflammation (monocytes and leukocytes). Both NO-releasing nanofiber gels stimulated re-endothelialization. CONCLUSIONS Perivascular application of NO-releasing self-assembling nanofiber gels is an effective and simple therapy to prevent neointimal hyperplasia after arterial injury. Our study demonstrates that the PROLI/NO nanofiber gel most effectively prevented neointimal hyperplasia and resulted in less inflammation than the DPTA/NO nanofiber gel. This therapy has great clinical potential to prevent neointimal hyperplasia after open vascular interventions in patients.

Isopropylamine NONOate (IPA/NO) moderates neointimal hyperplasia following vascular injury.

OBJECTIVE Isopropylamine NONOate (IPA/NO) is a nitroxyl (HNO) donor at physiologic pH. HNO is a positive inotrope and vasodilator, but little is known about its effect on neointimal hyperplasia. The aims of this study are to determine the effect of IPA/NO on endothelial and vascular smooth muscle cells (VSMC) in vitro and to determine if IPA/NO inhibits neointimal hyperplasia in vivo. METHODS VSMC were harvested from the abdominal aortas of male Sprague Dawley rats, and human umbilical vein endothelial cells were purchased from ATCC. In vitro, cellular proliferation was assessed by (3)H-thymidine incorporation, cell migration was assessed using the scrape assay, and cell death was assessed using Guava personal cell analysis (PCA). Cell cycle analysis was performed using propidium iodide staining and flow cytometry analysis. Protein expression was assessed using Western blot analysis. Phosphorylated proteins were assessed using immunoprecipitation and Western blot analysis. In vivo, the carotid artery injury model was performed on male Sprague Dawley rats treated with (n = 12) or without (n = 6) periadventitial IPA/NO (10 mg). Arteries harvested at 2 weeks were assessed for morphometrics using ImageJ. Inflammation was assessed using immunohistochemistry. Endothelialization was assessed by Evans blue staining of carotid arteries harvested 7 days after balloon injury from rats treated with (n = 6) or without (n = 3) periadventitial IPA/NO (10 mg). RESULTS In vitro, 1000 micromol/L IPA/NO inhibited both VSMC (38.7 +/- 4.5% inhibition vs control, P = .003) and endothelial cell proliferation (54.0 +/- 2.9% inhibition vs control, P < or = 0.001) without inducing cell death or inhibiting migration. In VSMC, this inhibition was associated with an S-phase cell cycle arrest and increased expression of cyclin A, cyclin D1, and the cyclin-dependent kinase inhibitor p21. No change was noted in the phosphorylation status of cdk2, cdk4, or cdk6 by IPA/NO. In rodents subjected to the carotid artery balloon injury model, IPA/NO caused significant reductions in neointimal area (298 +/- 20 vs 422 +/- 30, P < or = .001) and medial area (311 +/- 14 vs 449 +/- 16, P < or = .001) compared with injury alone, and reduced macrophage infiltration to 1.7 +/- 0.8 from 16.1 +/- 3.5 cells per high power field (P < or = .001). IPA/NO also prevented re-endothelialization compared with injury alone (55.9 +/- 0.5% nonendothelialized vs 21 +/- 4.4%, respectively, P = .001). Lastly, a 50% mortality rate was observed in the IPA/NO-treated groups. CONCLUSIONS In summary, while IPA/NO modestly inhibited neointimal hyperplasia by inhibiting VSMC proliferation and macrophage infiltration, it also inhibited endothelial cell proliferation and induced significant mortality in our animal model. Since HNO is being investigated as a treatment for congestive heart failure, our results raise some concerns about the use of IPA/NO in the vasculature and suggest that further studies be conducted on the safety of HNO donors in the cardiovascular system.

Dysphagia after anterior cervical spine surgery: a systematic review of potential preventative measures

BACKGROUND CONTEXT Anterior cervical spine surgery is one of the most common spinal procedures performed around the world, but dysphagia is a frequent postoperative complication. Many factors have been associated with an increased risk of swallowing difficulties, including multilevel surgery, revision surgery, and female gender. PURPOSE The objective of this study was to review and define potential preventative measures that can decrease the incidence of dysphagia after anterior cervical spine surgery. STUDY DESIGN This was a systematic literature review. METHODS A systematic review in the Medline database was performed. Articles related to dysphagia after anterior cervical spine surgery and potential preventative measures were included. RESULTS Twenty articles met all inclusion and exclusion criteria. These articles reported several potential preventative measures to avoid postoperative dysphagia. Preoperative measures include performing tracheal exercises before the surgical procedure. Intraoperative measures can be summarized as avoiding a prolonged operative time and the use of recombinant human bone morphogenetic protein in routine anterior cervical spine surgery, using small and smoother cervical plates, using anchored spacers instead of plates, application of steroid before wound closure, performing arthroplasty instead of anterior cervical fusion for one-level disease, decreasing tracheal cuff pressure during medial retraction, using specific retractors, and changing the dissection plan. CONCLUSIONS Current literature supports several preventative measures that may decrease the incidence of postoperative dysphagia. Although the evidence is limited and weak, most of these measures did not appear to increase other complications and can be easily incorporated into a surgical practice, especially in patients who are at high risk for postoperative dysphagia.

Poly(diol‐co‐citrate)s as Novel Elastomeric Perivascular Wraps for the Reduction of Neointimal Hyperplasia

The synthesis of poly(diol-co-citrate) elastomers that are biocompatible with vascular cells and can modulate the kinetics of the NO release based on the diol of selection is reported. NO-mediated cytostatic or cytotoxic effects can be controlled depending on the NO dose and the exposure time. When implanted in vivo in a rat carotid artery injury model, these materials demonstrate a significant reduction of neointimal hyperplasia. This is the first report of a NO-releasing polymer fabricated in the form of an elastomeric perivascular wrap for the treatment of neointimal hyperplasia. These elastomers also show promise for other cardiovascular pathologies where NO-based therapies could be beneficial.

Surgical Management of Kyphosis in Meningomyelocele

Spinal deformities, particularly scoliosis and kyphosis, are frequently encountered in patients with myelomeningocele. Rigid lumbar and thoracolumbar kyphosis presents serious functional impediments with regard to sitting balance, and the use of upper extremities other than for balance can lead to chronic skin breakdown over the gibbus deformity. Many patients are unable to lie supine because of the severe deformity, and bracing has not been shown to change the natural history of the kyphosis. Surgery is the only proven method to improve the sagittal spine alignment leading to improvements in posture, sitting balance, as well as ability of the caretaker to provide care for the patient. Several types of kyphectomies have been shown to have excellent results with regard to the sagittal plane correction. Vertebral column resections with multiple different options for instrumentation have been studied extensively. Decancellation vertebrectomies, also known as pedicle subtraction osteotomies or eggshell procedures, have also been demonstrated to achieve adequate kyphosis correction and are a viable option as well. Although these procedures are effective in achieving preoperative goals, it must be noted that there is a high incidence of perioperative complications that the surgeon and family must also be aware of. This chapter will discuss the background of the deformity, the perioperative issues revolving around the treatment, the surgical details including different strategies, a result reviews from the past, as well as the most common complications seen during kyphectomy in myelomeningocele patients.