Enzyme-Targeted Nanoparticles for Delivery to Ischemic Skeletal Muscle

The targeted delivery of enzyme-responsive nanoparticles to specific tissues can be a valuable, minimally invasive approach for imaging or drug delivery applications. In this study, we show for the first time enzyme-directed assembly of intravenously (IV) delivered nanoparticles in ischemic skeletal muscle, which has applications for drug delivery to damaged muscle of the type prevalent in peripheral artery disease (PAD). Specifically, micellar nanoparticles are cleavable by matrix metalloproteinases (MMPs), causing them to undergo a morphological switch and thus aggregate in tissues where these enzymes are upregulated, like ischemic muscle. Here, we demonstrated noninvasive in vivo imaging of these IV-injected nanoparticles through near-infrared dye labeling and in vivo imaging (IVIS) particle tracking in a rat hindlimb ischemia model. Polymer peptide amphiphilic nanoparticles were synthesized and optimized for both MMP cleavage efficiency and near-IR fluorescence. Nanoparticles were injected 4 days after unilateral hindlimb ischemia and were monitored over 28 days using IVIS imaging. Nanoparticles targeted to ischemic muscle over healthy muscle, and ex vivo biodistribution analysis at 7 and 28 days post-injection confirmed targeting to the ischemic muscle as well as off target accumulation in the liver and spleen. Ex vivo histology confirmed particle localization in ischemic but not healthy muscle. Altering the surface charge of the nanoparticles through addition of zwitterionic dye species resulted in improved targeting to the ischemic muscle. To our knowledge, this is the first study to demonstrate the targeted delivery and long term retention of nanoparticles using an enzyme-directed morphology switch. This has implications for noninvasive drug delivery vehicles for treating ischemic muscle, as no minimally invasive, non-surgical options currently exist.

Micro- and Nanoparticles for Treating Cardiovascular Disease

Cardiovascular disease, including myocardial infarction (MI) and peripheral artery disease (PAD), afflicts millions of people in Unites States. Current therapies are insufficient to restore blood flow and repair the injured heart or skeletal muscle, respectively, which is subjected to ischemic damage following vessel occlusion. Micro- and nano-particles are being designed as delivery vehicles for growth factors, enzymes and/or small molecules to provide a sustained therapeutic stimulus at the injured tissue. Depending on the formulation, the particles can be injected directly into the heart or skeletal muscle, or accumulate at the site of injury following an intravenous injection. In this article we review existing particle based therapies for treating MI and PAD.

Fabrication and characterization of injectable hydrogels derived from decellularized skeletal and cardiac muscle

Biomaterials, which can contain appropriate biomechanical and/or biochemical cues, are increasingly being investigated as potential scaffolds for tissue regeneration and/or repair for treating myocardial infarction, heart failure, and peripheral artery disease. Specifically, injectable hydrogels are touted for their minimally invasive delivery, ability to self-assemble in situ, and capacity to encourage host tissue regeneration. Here we present detailed methods for fabricating and characterizing decellularized injectable cardiac and skeletal muscle extracellular matrix (ECM) hydrogels. The ECM derived hydrogels have low cellular and DNA content, retain sulfated glycosaminoglycans and other extracellular matrix proteins such as collagen, gel at physiologic temperature and pH, and assume a nanofibrous architecture. These injectable hydrogels are amenable to minimally invasive, tissue specific biomaterial therapies for treating myocardial infarction and peripheral artery disease.

Injectable skeletal muscle matrix hydrogel promotes neovascularization and muscle cell infiltration in a hindlimb ischemia model

Peripheral artery disease (PAD) currently affects approximately 27 million patients in Europe and North America, and if untreated, may progress to the stage of critical limb ischemia (CLI), which has implications for amputation and potential mortality. Unfortunately, few therapies exist for treating the ischemic skeletal muscle in these conditions. Biomaterials have been used to increase cell transplant survival as well as deliver growth factors to treat limb ischemia; however, existing materials do not mimic the native skeletal muscle microenvironment they are intended to treat. Furthermore, no therapies involving biomaterials alone have been examined. The goal of this study was to develop a clinically relevant injectable hydrogel derived from decellularized skeletal muscle extracellular matrix and examine its potential for treating PAD as a stand-alone therapy by studying the material in a rat hindlimb ischemia model. We tested the mitogenic activity of the scaffold's degradation products using an in vitro assay and measured increased proliferation rates of smooth muscle cells and skeletal myoblasts compared to collagen. In a rat hindlimb ischemia model, the femoral artery was ligated and resected, followed by injection of 150 µL of skeletal muscle matrix or collagen 1 week post-injury. We demonstrate that the skeletal muscle matrix increased arteriole and capillary density, as well as recruited more desmin-positive and MyoD-positive cells compared to collagen. Our results indicate that this tissue-specific injectable hydrogel may be a potential therapy for treating ischemia related to PAD, as well as have potential beneficial effects on restoring muscle mass that is typically lost in CLI.

Injectable biomaterials for adipose tissue engineering

Adipose tissue engineering has recently gained significant attention from materials scientists as a result of the exponential growth of soft tissue filler procedures being performed within the clinic. While several injectable materials are currently being marketed for filling subcutaneous voids, they often face limited longevity due to rapid resorption. Their inability to encourage natural adipose formation or ingrowth necessitates repeated injections for a prolonged effect and thus classifies them as temporary fillers. As a result, a significant need for injectable materials that not only act as fillers but also promote in vivo adipogenesis is beginning to be realized. This paper will discuss the advantages and disadvantages of commercially available soft tissue fillers. It will then summarize the current state of research using injectable synthetic materials, biopolymers and extracellular matrix-derived materials for adipose tissue engineering. Furthermore, the successful attributes observed across each of these materials will be outlined along with a discussion of the current difficulties and future directions for adipose tissue engineering.

Effects of resveratrol on the autophosphorylation of phorbol ester-responsive protein kinases: inhibition of protein kinase D but not protein kinase C isozyme autophosphorylation

The natural product resveratrol is a potent antagonist of phorbol ester-mediated tumor promotion and in vitro cellular responses to phorbol-ester tumor promoters, but it is only weakly inhibitory against the phosphorylation of conventional exogenous substrates by phorbol ester-responsive protein kinase C (PKC) isozymes. In this report, we compare the effects of resveratrol against the autophosphorylation reactions of PKC isozymes versus the novel phorbol ester-responsive kinase, protein kinase D (PKD). We found that resveratrol inhibits PKD autophosphorylation in a concentration-dependent manner, but has only negligible effects against the autophosphorylation reactions of representative members of each PKC isozyme subfamily (cPKC-alpha, -beta(1), and -gamma, nPKC-delta and -epsilon, and aPKC-zeta). Resveratrol was comparably effective against PKD autophosphorylation (IC(50) = 52 microM) and PKD phosphorylation of the exogenous substrate syntide-2 (IC(50) = 36 microM). The inhibitory potency of resveratrol against PKD is in line with the potency of resveratrol observed in cellular systems and with its potency against other purified enzymes and binding proteins that are implicated in the cancer chemopreventive activity of the polyphenol. Thus, PKD inhibition may contribute to the cancer chemopreventive action of resveratrol.

Edatrexate in patients with soft tissue sarcoma. Activity in malignant fibrous histiocytoma

BACKGROUND

Chemotherapy has had little impact on the natural history of soft tissue sarcoma, and often is associated with serious toxicity. Edatrexate, an investigational antifolate, is active in patients with lung cancer, and has cytotoxic activity in human sarcoma cell lines.

METHODS

Edatrexate was administered to 36 patients with measurable, advanced soft tissue sarcoma who had not previously received chemotherapy. The drug was given weekly for 5 weeks, then every other week. The initial dose, 80 mg/m2, was escalated by 10 mg/m2 every 2 weeks in the absence of toxicity. Eleven patients had leiomyosarcoma, 7 had malignant fibrous histiocytoma (MFH), and 5 had liposarcoma; the remainder of cell types included hemangiopericytoma (4), angiosarcoma (3), synovial (2), spindle cell (2), extraosseous chondrosarcoma (1), and fibrosarcoma (1).

RESULTS

Thirty-five patients are evaluable. Partial response (PR) was seen in five of the seven patients with MFH; no other major responses occurred. Overall, the response frequency was 14% (two-sided 95% confidence interval, 3% to 26%). Median duration of PR was 6 months (range, 4-18 months). One patient had a minor tumor regression, and six had stable disease. Myelosuppression was generally mild; only three patients had grade 3 hematologic toxicity. Modification of dose or schedule was required in 50% of patients for mucositis. Fatigue was a common toxicity, seen in 66% of patients, but was tolerable in the majority. A rash was seen in 46% of patients; one patient had hepatic toxicity.

CONCLUSIONS

Overall, the activity of edatrexate in this study, dominated by patients with either visceral or vascular sarcoma, was poor. However, the responses observed in patients with metastatic MFH suggests that further evaluation of edatrexate in patients with soft tissue sarcoma is warranted.

Quantitation of S-adenosylmethionine decarboxylase protein

A method for the specific labeling of the active site of S-adenosylmethionine decarboxylase was developed. The method consisted of incubating cell extracts with 3H-decarboxylated S-adenosylmethionine and sodium cyanoborohydride in the presence of a spermidine synthase inhibitor. Under these conditions, S-adenosylmethionine decarboxylase was labeled specifically and stoichiometrically. This procedure was used (a) to establish that the subunit molecular weight of S-adenosylmethionine decarboxylase from rat liver, prostate, and psoas and from mouse SV-3T3 cells was 32 000, (b) to titrate the number of active molecules of S-adenosylmethionine decarboxylase in various cell extracts, and (c) to provide a high specific activity labeled preparation of S-adenosylmethionine decarboxylase for use in radioimmunoassay of this enzyme. Competitive radioimmunoassays using this labeled antigen had a sensitivity such that 3 fmol (0.1 ng) of enzyme protein could be quantitated. The rapid loss of S-adenosylmethionine decarboxylase which occurred when SV-3T3 cells were exposed to exogenous polyamines was shown to be due to a rapid decline in the amount of enzyme protein measured both by titration of the active site and by radioimmunoassay.

Adolescent suicide and the classroom teacher

Adolescent suicide is a phenomenon of epidemic proportions, constituting the third leading cause of death in this age group. Various theories of suicide are reviewed and the attention to family variables discussed. These theoretical models indicate the multidisciplinary nature of the problem - that is, that adolescent suicide requires a medical, psychological, social and educational approach to the problem. Since school plays a major role in the lives of adolescents, it offers an avenue of approach to adolescent suicide. A list of behavioral changes indicative of emotional distress is provided for teachers for use in identification and referral. Teachers should also serve an educational function. Discussion of suicide dispels myths and modifies the likelihood of an attempt. Several suggestions concerning how school personnel may intervene are provided.