Increasing injection frequency enhances the survival of injected bone marrow derived mesenchymal stem cells in a critical limb ischemia animal model

Critical limb ischemia (CLI) is one of the most severe forms of peripheral artery diseases, but current treatment strategies do not guarantee complete recovery of vascular blood flow or reduce the risk of mortality. Recently, human bone marrow derived mesenchymal stem cells (MSCs) have been reported to have a paracrine influence on angiogenesis in several ischemic diseases. However, little evidence is available regarding optimal cell doses and injection frequencies. Thus, the authors undertook this study to investigate the effects of cell dose and injection frequency on cell survival and paracrine effects. MSCs were injected at 10⁶ or 10⁵ per injection (high and low doses) either once (single injection) or once in two consecutive weeks (double injection) into ischemic legs. Mice were sacrificed 4 weeks after first injection. Angiogenic effects were confirmed in vitro and in vivo, and M2 macrophage infiltration into ischemic tissues and rates of limb salvage were documented. MSCs were found to induce angiogenesis through a paracrine effect in vitro, and were found to survive in ischemic muscle for up to 4 weeks dependent on cell dose and injection frequency. In addition, double high dose and low dose of MSC injections increased vessel formation, and decreased fibrosis volumes and apoptotic cell numbers, whereas a single high dose did not. Our results showed MSCs protect against ischemic injury in a paracrine manner, and suggest that increasing injection frequency is more important than MSC dosage for the treatment CLI.     

Parallel imaging improves the image quality and duct visibility of breathhold two‐dimensional thick‐slab MR cholangiopancreatography

MRI has become a reliable tool in medical imaging for assessing morphological and functional details of the human body in a noninvasive manner. Perfusion is an important parameter to assess status and functionality of tissue and organs. This review summarizes the different approaches to measure perfusion based on MRI. Some basics of the theoretical background are provided as well as measurement techniques with and without contrast media are described. J. Magn. Reson. Imaging 2014;40:269–279 . © 2013 Wiley Periodicals, Inc .