Imaging Long-Term Fate of Intramyocardially Implanted Mesenchymal Stem Cells in a Porcine Myocardial Infarction Model

The long-term fate of stem cells after intramyocardial delivery is unknown. We used noninvasive, repetitive PET/CT imaging with [18F]FEAU to monitor the long-term (up to 5 months) spatial-temporal dynamics of MSCs retrovirally transduced with the sr39HSV1-tk gene (sr39HSV1-tk-MSC) and implanted intramyocardially in pigs with induced acute myocardial infarction. Repetitive [18F]FEAU PET/CT revealed a biphasic pattern of sr39HSV1-tk-MSC dynamics; cell proliferation peaked at 33–35 days after injection, in periinfarct regions and the major cardiac lymphatic vessels and lymph nodes. The sr39HSV1-tk-MSC–associated [18F]FEAU signals gradually decreased thereafter. Cardiac lymphography studies using PG-Gd-NIRF813 contrast for MRI and near-infrared fluorescence imaging showed rapid clearance of the contrast from the site of intramyocardial injection through the subepicardial lymphatic network into the lymphatic vessels and periaortic lymph nodes. Immunohistochemical analysis of cardiac tissue obtained at 35 and 150 days demonstrated several types of sr39HSV1-tk expressing cells, including fibro-myoblasts, lymphovascular cells, and microvascular and arterial endothelium. In summary, this study demonstrated the feasibility and sensitivity of [18F]FEAU PET/CT imaging for long-term, in-vivo monitoring (up to 5 months) of the fate of intramyocardially injected sr39HSV1-tk-MSC cells. Intramyocardially transplanted MSCs appear to integrate into the lymphatic endothelium and may help improve myocardial lymphatic system function after MI

Toxicology of chemically modified graphene-based materials for medical application.

This review article aims to provide an overview of chemically modified graphene, and graphene oxide (GO), and their impact on toxicology when present in biological systems. Graphene is one of the most promising nanomaterials due to unique physicochemical properties including enhanced optical, thermal, and electrically conductive behavior in addition to mechanical strength and high surface-to-volume ratio. Graphene-based nanomaterials have received much attention over the last 5 years in the biomedical field ranging from their use as polymeric conduits for nerve regeneration, carriers for targeted drug delivery and in the treatment of cancer via photo-thermal therapy. Both in vitro and in vivo biological studies of graphene-based nanomaterials help understand their relative toxicity and biocompatibility when used for biomedical applications. Several studies investigating important material properties such as surface charge, concentration, shape, size, structural defects, and chemical functional groups relate to their safety profile and influence cyto- and geno-toxicology. In this review, we highlight the most recent studies of graphene-based nanomaterials and outline their unique properties, which determine their interactions under a range of environmental conditions. The advent of graphene technology has led to many promising new opportunities for future applications in the field of electronics, biotechnology, and nanomedicine to aid in the diagnosis and treatment of a variety of debilitating diseases

MDM2

The aim of the present study was to investigate the possible use of mouse double-minute 2 ( MDM2 ) molecular imaging to predict chemotherapeutic sensitivity in breast cancer xenografts (BCXs). MCF-7 cells were transfected with MDM2 antisense oligonucleotides (ASONs), and MDM2 expression levels were determined by Western blotting. Cell viability was assessed by 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in MCF-7 cells transfected with ASONs and treated with paclitaxel. BCXs were established in nude mice by injection of ASONs, and tumor volumes were measured after paclitaxel treatment. MDM2 ASONs were labeled with 99m Tc to generate an MDM2 molecular probe, and MDM2 expression levels were evaluated by imaging and Western blotting. MDM2 ASONs downregulated MDM2 expression in a dose-dependent manner and increased the rate of paclitaxel-induced cell growth inhibition. Imaging of tumors revealed significant differences in the tumor to skeletal muscle (T/M) ratio between groups. Tumor MDM2 protein expression was correlated with T/M ratios at 4 hours ( R = .880) and 10 hours ( R = .886). The effect of paclitaxel varied among nude mice bearing BCXs with different concentrations of ASONs, as shown by differences in tumor growth. MDM2 molecular imaging could be a promising method for predicting the sensitivity of BCXs to chemotherapy