Elevated adipogenesis of marrow mesenchymal stem cells during early steroid-associated osteonecrosis development

<p>Abstract</p> <p>Background</p> <p>Increased bone marrow lipid deposition in steroid-associated osteonecrosis (ON) implies that abnormalities in fat metabolism play an important role in ON development. The increase in lipid deposition might be explained by elevated adipogenesis of marrow mesenchymal stem cells (MSCs). However, it remains unclear whether there is a close association between elevated adipogenesis and steroid-associated ON development.</p> <p>Objective</p> <p>The present study was designed to test the hypothesis that there might be a close association between elevated adipogenesis and steroid-associated ON development.</p> <p>Methods</p> <p>ON rabbit model was induced based on our established protocol. Dynamic-MRI was employed for local intra-osseous perfusion evaluation in bilateral femora. Two weeks after induction, bone marrow was harvested for evaluating the ability of adipogenic differentiation of marrow MSCs at both cellular and mRNA level involving adipogenesis-related gene peroxisome proliferator-activated receptor gamma2 (PPARγ2). The bilateral femora were dissected for examining marrow lipid deposition by quantifying fat cell number, fat cell size, lipid deposition area and ON lesions. For investigating association among adipogenesis, lipid deposition and perfusion function with regard to ON occurrence, the rabbits were divided into ON⁺(with at least one ON lesion) group and ON^-(without ON lesion) group. For investigating association among adipogenesis, lipid deposition and perfusion function with regard to ON extension, the ON⁺rabbits were further divided into sub-single-lesion group (SON group: with one ON lesion) and sub-multiple-lesion group (MON group: with more than one ON lesion).</p> <p>Results</p> <p>Local intra-osseous perfusion index was found lower in either ON⁺or MON group when compared to either ON^-or SON group, whereas the marrow fat cells number and area were much larger in either ON⁺or MON group as compared with ON^-and SON group. The adipogenic differentiation ability of MSCs and PPARγ2 expression in either ON⁺or MON group were elevated significantly as compared with either ON^-or SON group.</p> <p>Conclusion</p> <p>These findings support our hypothesis that there is a close association between elevated adipogenesis and steroid-associated osteonecrosis development.</p

Blood perfusion assessed by dynamic MRI for Maximum Enhancement and Time-Signal Intensity

<p><b>Copyright information:</b></p><p>Taken from "Elevated adipogenesis of marrow mesenchymal stem cells during early steroid-associated osteonecrosis development"</p><p>http://www.josr-online.com/content/2/1/15</p><p>Journal of Orthopaedic Surgery and Research 2007;2():15-15.</p><p>Published online 15 Oct 2007</p><p>PMCID:PMC2146995.</p><p></p> (A) Maximum Enhancement at the examined sites (both proximal femora and distal femora, the similar pattern was found, data not shown here for distal femora) showed a significant decrease from baseline in ONrabbits at week 2 after steroid induction. There were significant decrease in Maximum Enhancement between ONand ONgroup, MON and SON group at week 2 (p < 0.05). (B) Representative Time-Signal Intensity curves from contrast-enhanced dynamic MRI on proximal femur. The Time-Signal Intensity curve showed a significant decrease in enhancement slope in ONgroup as compared with ONgroup at week 2

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field