Liposomal Nanocarriers Designed for Sub-Endothelial Matrix Targeting under Vascular Flow Conditions.

Vascular interventions result in the disruption of the tunica intima and the exposure of sub-endothelial matrix proteins. Nanoparticles designed to bind to these exposed matrices could provide targeted drug delivery systems aimed at inhibiting dysfunctional vascular remodeling and improving intervention outcomes. Here, we present the progress in the development of targeted liposomal nanocarriers designed for preferential collagen IV binding under simulated static vascular flow conditions. PEGylated liposomes (PLPs), previously established as effective delivery systems in vascular cells types, served as non-targeting controls. Collagen-targeting liposomes (CT-PLPs) were formed by conjugating established collagen-binding peptides to modified lipid heads via click chemistry (CTL), and inserting them at varying mol% either at the time of PLP assembly or via micellar transfer. All groups included fluorescently labeled lipid species for imaging and quantification. Liposomes were exposed to collagen IV matrices statically or via hemodynamic flow, and binding was measured via fluorometric analyses. CT-PLPs formed with 5 mol% CTL at the time of assembly demonstrated the highest binding affinity to collagen IV under static conditions, while maintaining a nanoparticle characterization profile of ~50 nm size and a homogeneity polydispersity index (PDI) of ~0.2 favorable for clinical translation. When liposomes were exposed to collagen matrices within a pressurized flow system, empirically defined CT-PLPs demonstrated significant binding at shear stresses mimetic of physiological through pathological conditions in both the venous and arterial architectures. Furthermore, when human saphenous vein explants were perfused with liposomes within a closed bioreactor system, CT-PLPs demonstrated significant ex vivo binding to diseased vascular tissue. Ongoing studies aim to further develop CT-PLPs for controlled targeting in a rodent model of vascular injury. The CT-PLP nanocarriers established here show promise as the framework for a spatially controlled delivery platform for future application in targeted vascular therapeutics.

Advances in the Formulation and Assembly of Non-Cationic Lipid Nanoparticles for the Medical Application of Gene Therapeutics.

Lipid nanoparticles have become increasingly popular delivery platforms in the field of gene therapy, but bench-to-bedside success has been limited. Many liposomal gene vectors are comprised of synthetic cationic lipids, which are associated with lipid-induced cytotoxicity and immunogenicity. Natural, non-cationic PEGylated liposomes (PLPs) demonstrate favorable biocompatibility profiles but are not considered viable gene delivery vehicles due to inefficient nucleic acid loading and reduced cellular uptake. PLPs can be modified with cell-penetrating peptides (CPPs) to enhance the intracellular delivery of liposomal cargo but encapsulate leakage upon CPP-PLP assembly is problematic. Here, we aimed to identify parameters that overcome these performance barriers by incorporating nucleic acid condensers during CPP-PLP assembly and screening variable ethanol injection parameters for optimization. CPP-PLPs were formed with R8-amphiphiles via pre-insertion, post-insertion and post-conjugation techniques and liposomes were characterized for size, surface charge, homogeneity, siRNA encapsulation efficiency and retention and cell associative properties. Herein we demonstrate that pre-insertion of stearylated R8 into PLPs is an efficient method to produce non-cationic CPP-PLPs and we provide additional assembly parameter specifications for a modified ethanol injection technique that is optimized for siRNA encapsulation/retention and enhanced cell association. This assembly technique could provide improved clinical translation of liposomal based gene therapy applications.

Dietary supplementation with Zyflamend poly-herbal extracts and fish oil inhibits intimal hyperplasia development following vascular intervention.

The polyherbal blend Zyflamend™ has been shown to have anti-inflammatory properties and attenuate inflammatory-modulated pathologies. Fish oils have also been shown to have cardioprotective properties. However, the beneficial effects of their combination have not been investigated. Intimal hyperplasia (IH), a pathological remodeling response of a vessel to injury, is heavily regulated by an immune-mediated reaction. The objective of this study was to determine if dietary supplementation with Zyflamend and/or Wholemega could affect inflammatory-dependent vascular remodeling mechanisms when provided at human equivalent doses. Based on their anti-inflammatory properties and protective benefits demonstrated in previous pre-clinical studies, we hypothesized administration of these supplements would prevent IH in an animal model of vascular injury. The diets of aged male rats were supplemented with human equivalent doses of Zyflamend (Zyf) and/or Wholemega (WMega) or placebo (Plac) for 1wk prior to balloon angioplasty (BA)-induced injury of the left carotid artery. At 28d post-injury morphometric analysis of carotid tissue revealed IH was decreased in Zyf + WMega animals compared to placebo, while Zyf or WMega independently had no significant effect. Serum cytokine screening indicated injury-induced interleukin family isoforms, interferon-γ, and macrophage inflammatory proteins were downregulated by Zyf + WMega. Immunohistochemical staining for monocyte/macrophage phenotypic markers revealed that while overall monocyte/macrophage vessel infiltration was not affected, Zyf + WMega limited the alternative differentiation of M2 macrophages and reduced the presence of myofibroblasts in the injured vessel wall. In summary, dietary supplementation with Zyf + WMega attenuated the acute inflammatory response following vascular injury and inhibited IH development in vivo.

The Efficacy of Systemic Doxycycline Administration as an Inhibitor of Intimal Hyperplasia after Balloon Angioplasty Arterial Injury.

BACKGROUND: Intimal hyperplasia (IH) is the most common indicator for secondary intervention in peripheral vascular disease. Matrix metalloproteinases (MMPs) play a role in IH development due to their degradation of the extracellular matrix. Doxycycline (Doxy), a member of the tetracycline family of antibiotics, is a potent MMP inhibitor. We have previously shown that Doxy inhibits MMP activity and vascular smooth muscle cell migration in vitro. We hypothesized that Doxy would decrease MMP activity in vivo and inhibit the development of IH in a rodent model of vascular injury. METHODS AND RESULTS: Doxy (400 mg/pellet) was delivered by a slow-release pellet implanted 3 days prior to or at the time of balloon angioplasty (BA) of the common carotid artery in female rats. At 14 days post-BA, intima-to-media (I:M) ratios were 0.77 ± 0.21 and 1.04 ± 0.32 in the Doxy treated groups, respectively, compared to 1.25 ± 0.26 in the control group (P = not significant; n = 3). Additionally, the tested dose of Doxy in either group had no inhibitory effect on membrane type 1-MMP or MMP-2 tissue levels, as measured by immunohistochemistry, or on systemic levels of MMP, as measured by total MMP serum levels using enzyme-linked immunosorbent assay. At 14 days post-BA, VSMC proliferation in the injured artery was increased to Doxy treatment prior to and at the time of surgery (23.5 ± 3.4 and 27.2 ± 3.9%, respectively), compared to control (11.4 ± 0.4%; n = 3), as measured by proliferating cellular nuclear antigen immunostaining. CONCLUSIONS: In our in vivo model of vascular injury, systemic Doxy administration prior to or at the time of vascular injury does not significantly hinder the progression of IH development. Additional doses and routes of administration could be examined in order to correlate therapeutic serum levels of Doxy with effective MMP inhibition in serum and arterial tissue. However, alternative drug delivery systems are needed in order to optimize therapeutic administration of targeted MMP inhibitors for the prevention of IH development.

Diabetic Foot Ulcers: The Importance of Patient Comorbidity Recognition and Total Contact Casting in Successful Wound Care.

Diabetic foot ulcers (DFUs) are a major burden on the health-care system. The purpose of this study is to investigate factors affecting the healing rate of DFU in a university wound care center. Records of DFU patients treated between July 2013 and February 2015 were reviewed. Demographics, comorbidities, wound characteristics, and treatment modalities including offloading, hyperbaric oxygen treatment, total contact casting, and bioengineered skin were investigated. All patients underwent weekly debridement regardless of treatment modality. A total of 114 patients ages 18 to 98 comprised the study population. Total contact casting was the only treatment associated with increased healing (P = 0.02). Smoking (P = 0.004) and deep vein thrombosis history (P = 0.001) significantly decreased the likelihood of wound healing. Patients with past vascular event trended toward longer healing times (P = 0.07). Total contact casting in combination with weekly wound debridement showed benefit in DFU wound healing, whereas patients with a history of deep vein thrombosis and smoking were less likely to heal.

Comparative analysis of polymers for short interfering RNA delivery in vascular smooth muscle cells.

UNLABELLED: The use of short interfering RNA (siRNA) to degrade messenger RNA in the cell cytoplasm and transiently attenuate intracellular proteins shows promise in the inhibition of vascular pathogenesis. However, a critical obstacle for therapeutic application is a safe and effective delivery system. Biodegradable polymers are promising alternative molecular carriers for genetic material. Here, we aim to perform a comparative analysis of poly(B-amino ester) (PBAE) and polyethylenimine (PEI) polymers in their efficacy for vascular smooth muscle cell transfection using siRNA against the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) housekeeping gene as our test target. METHODS: Human aortic smooth muscle cells (HASMC) were transfected in vitro with polymers conjugated to GAPDH or negative control (NC) siRNAs. Increasing siRNA:polymer ratios were tested for optimal transfection efficiency. DharmaFECT2 chemical transfection complexes were used for comparative analysis. Live/dead dual stain was used to measure cell viability, and GAPDH gene silencing was measured by quantitative polymerase chain reaction normalized to 18S. RESULTS: The highest rate of PEI-mediated silencing was achieved with a 9µL polymer:220 pmol/mL siRNA conjugate (16 ± 2% expression versus NC; n = 6). Comparable PBAE-mediated silencing could be achieved with a 1.95µL polymer:100 pmol/mL siRNA conjugate (10 ± 1% expression versus NC; n = 5). Transfection using PEIs resulted in silencing equivalent to other methods but with less efficiency and increased cell toxicity at 24h polymer exposure. Decreasing PEI exposure time to 4 h resulted in similar silencing efficacy (21 ± 9% expression versus NC, n = 6) with an improved toxicity profile. CONCLUSIONS: Polymeric bioconjugates transfected HASMCs in a manner similar to chemical complexes, with comparable cell toxicity and silencing efficiency. PEI bioconjugates demonstrated silencing equivalent to PBAE bioconjugates, although less efficient in terms of required polymer concentrations. Given the cost-to-benefit difference between the assayed polymers, and PEI's ability to transfect HASMCs within a short duration of exposure with an improved toxicity profile, this study shows that PEI bioconjugates are a potential transfection agent for vascular tissue. Future studies will expand on this method of gene therapy to validate delivery of gene-specific inhibitors aimed at attenuating smooth muscle cell proliferation, adhesion, and migration. These studies will lay the framework for our future experimental plans to expand on this method of gene therapy for in vivo transfection in animal models of vascular disease.

Androgens regulate MMPs and the cellular processes of intimal hyperplasia.

BACKGROUND: Testosterone deficiency has been associated with an increased risk of vascular disease. Matrix metalloproteinases (MMPs) have been implicated in vascular remodeling. Our group has demonstrated an association between female hormones and MMP-modulated intimal hyperplasia. In the present study, we investigated testosterone in the modulation of MMPs and the cellular processes of intimal hyperplasia. MATERIALS AND METHODS: Male vascular smooth muscle cells (VSMCs) were treated with a range of testosterone or dihydrotestosterone (DHT) concentrations (0.3-3000 nM). MMPs were assayed using quantitative polymerase chain reaction, Western blot analysis, and zymography. VSMC migration and proliferation were assayed using Boyden chamber and MTT assays. RESULTS: MT1-MMP gene expression was not affected by low DHT exposure but was downregulated at high levels (3000 nM = 85% ± 3%). TIMP-2 gene expression was downregulated at low DHT exposure (0.3 nM = 82% ± 4%, 3.0 nM = 82% ± 1%) but was not affected at high levels. MMP-2 enzymatic activity was increased at low DHT exposure (3.0 nM = 110% ± 4%) and decreased below basal levels at high doses (300 nM = 91% ± 7%, 3000 nM = 77% ± 8%). High concentrations of DHT decreased VSMC migration (3.0 nM = 72% ± 9%, 30 nM = 50% ± 6%, 300 nM = 47% ± 5%, 3000 nM = 53% ± 6%). Testosterone also decreased migration but had less effect. The highest tested concentration of DHT and testosterone decreased the basal VSMC proliferation (3000 nM = 87% ± 3% and 87% ± 4% respectively). CONCLUSIONS: The DHT levels differentially affected the expression of regulatory isoforms responsible for the activation and inhibition of MMP-2, leading to an inverse relationship among the DHT levels, MMP-2 activity, and VSMC migration. In vivo studies will be used to examine testosterone deficiency and supplementation in MMP-modulated intimal hyperplasia in animal models of vascular disease. These studies are needed as a prerequisite to determining whether testosterone replacement in testosterone-deficient men should be evaluated for attenuation of atherosclerosis.

Smooth muscle cell polymeric transfection is an efficient alternative to traditional methods of experimental gene therapy.

BACKGROUND: Gene therapy shows promise in the treatment of vascular disease. However, traditional transfection methods commonly used in the laboratory are poorly translatable to in vivo conditions, primarily due to the immune response to viral vectors, the cellular toxicity of chemical transfection, and the technical impracticality of electroporation. Biodegradable polymers have shown promise as a safe, predictable, and nontoxic alternative, relying on endocytosis of synthetic polymeric carriers, which are bioconjugated to the targeted genetic material of choice. However, to date most of the feasibility studies have been exclusively performed in stem cells. Differentiated cell types would be prime targets for therapeutic gene modulation in the prevention of various disease processes. We aim to establish polymeric transfection as a method for gene therapy in cells of vascular origin. Here we compared the efficiency of polymeric transfection with chemical transfection agents routinely used in a laboratory setting in vascular smooth muscle cells. METHODS: Human aortic smooth muscle cells (HASMC) were transfected with fluorescently labeled GAPDH siRNA or negative control (NC) siRNA. Transfection methods included poly(B-amino ester) polymer (StemFECT) bioconjugates, DharmaFECT2 complexes, and Santa Cruz complexes. Conjugate endocytosis was confirmed by fluorescent microscopy, and GAPDH gene silencing was assayed by qPCR normalized to 18S. RESULTS: Santa Cruz reagent complexes were the least efficient, with the maximum achievable gene silencing using a 9 µL reagent : 70 pmol siRNA/mL complex (59% ± 6%; n = 3). Maximum GADPH gene silencing using DharmaFECT2 was achieved with a 1.5 µL reagent : 100 pmol siRNA/mL complex (19% ± 1% expression versus NC; n = 4). Equivalent silencing was achieved using a comparable StemFECT bioconjugate of 1.3 µL polymer : 100 pmol siRNA/mL (25% ± 3% expression versus NC; n = 4; P = NS versus DharmaFECT2). By increasing the StemFECT bioconjugate to 1.95 µL polymer : 100 pmol siRNA/mL, gene silencing was significantly increased (10% ± 1% expression versus NC; n = 6; P < 0.05 versus DharmaFECT2 and StemFECT 1.3:100). CONCLUSION: HASMCs were efficiently transfected using polymeric bioconjugates in a manner comparable to and exceeding other transfection agents routinely used in vitro. This proof of concept establishes polymeric transfection as a viable method for in vitro investigation of differentiated vascular cells. Future studies will expand on this method of gene therapy for ex vivo transfection of whole vessel segments and in vivo transfection in animal models of vascular disease. Our long-term goal is to deliver molecular inhibitors of genes thought to play a role in intimal hyperplasia, restenosis, and vessel graft failure.

Gold Medal Forum Winner. Unfractionated heparin three times a day versus enoxaparin in the prevention of deep vein thrombosis in trauma patients.

Venous thromboembolic disease is a significant source of morbidity and mortality in hospitalized trauma patients. Multiple drugs and dosing regimens have been suggested for pharmacoprophylaxis. In this study, we compared efficacy, complications, and cost of unfractionated heparin administered subcutaneously three times a day with standard-dosed enoxaparin for prophylaxis of deep venous thrombosis (DVT) in adult trauma patients over 1 year. Patients admitted for greater than 72 hours who received pharmacoprophylaxis as part of a comprehensive DVT protocol were included. A change was made in the protocol from enoxaparin (30 mg twice a day or 40 mg per day) to heparin (5000 U three times a day) at midyear. Surveillance lower extremity venous ultrasound was performed according to established institutional guidelines. Data, including demographics, associated injuries, complications, and cost, were collected and analyzed. Four hundred seventy-six patients met inclusion criteria. Two hundred thirty-seven (49.8%) patients received enoxaparin and 239 (50.2%) received heparin. Proximal lower extremity DVTs were detected in 16 (6.75%) patients in the enoxaparin group and 17 (7.11%) in the heparin group (P = 0.999). Risk factors for DVT in these patients included spinal cord injury (P = 0.001) and closed head injury (P = 0.031). There was no difference between the incidence of pulmonary emboli and bleeding. There was an estimated yearly pharmacy cost savings of $135,606. In trauma patients, subcutaneous heparin dosed three times a day may be as effective as standard-dosed enoxaparin for prophylaxis of venous thromboembolism without increased complications. Heparin three times a day for venous thromboembolism prophylaxis was associated with significant pharmaceutical cost savings.

Education of the rural surgeon: experience from Tennessee.

The rural surgery rotation that is contained within the general surgery residency program at The University of Tennessee College of Medicine-Chattanooga is described in this article. The advantages of this experience, including the extensive endoscopy experience and the close exposure to practicing general surgeons, are also outlined. The rotation receives uniformly positive evaluations from residents at completion, and it has become the primary gastrointestinal endoscopy educational experience in this program. The description serves as a model that can be used by other programs to construct a rural surgery rotation.