Adult human mesenchymal stem cells (MSCs) hold promise for an increasing list of therapeutic uses due to their ease of isolation, expansion, and multilineage differentiation potential. To maximize the clinical potential of MSCs, the underlying mechanisms by which MSC functionality is controlled must be understood. We have taken a deconstructive approach to understand the individual components in vitro, namely the role of candidate "stemness" genes. Our recent microarray gene expression profiling data suggest that interleukin-6 (IL-6) may contribute to the maintenance of MSCs in their undifferentiated state. In this study, we showed that IL-6 gene expression is significantly higher in undifferentiated MSCs as compared to their chondrogenic, osteogenic, and adipogenic derivatives. Moreover, we found that MSCs secrete copious amounts of IL-6 protein, which decreases dramatically during osteogenic differentiation. We further evaluated the role of IL-6 for maintenance of MSC "stemness", using a series of functional assays. The data showed that IL-6 is both necessary and sufficient for enhanced MSC proliferation, protects MSCs from apoptosis, inhibits adipogenic and chondrogenic differentiation of MSCs, and increases the rate of in vitro wound healing of MSCs. We further identified ERK1/2 activation as the key pathway through which IL-6 regulates both MSC proliferation and inhibition of differentiation. Taken together, these findings show for the first time that IL-6 maintains the proliferative and undifferentiated state of bone marrowderived MSCs, an important parameter for the optimization of both in vitro and in vivo manipulation of MSCs. KeywordsMesenchymal stem cells; Differentiation; Stemness; Interleukin-6 Three components are required for successful tissue engineering and regeneration: cells with regenerative potential, a biocompatible scaffold or matrix, and environmental and endogenous influences to drive these cells towards desired functional tissue neo-genesis. Adult human mesenchymal stem cells (MSCs) are a promising source of cells that can largely satisfy the first of our three necessary criteria. MSCs are tissue-resident stem cells [Pereira et al., 1995;Prockop, 1997]. They are commonly isolated from the bone marrow but can also be found in the perivascular regions of most tissues, such as adipose, skeletal muscle, and umbilical cord [Sarugaser et al., 2005;Zuk et al., 2002]. MSCs are capable of differentiation into several cell lineages, including osteoblasts, chondrocytes, adipocytes, and myoblasts [Jiang et al., 2002;Pittenger et al., 1999]. Owing to their ease of isolation, expansion, and multi-lineage differentiation capability, MSCs are a promising cell source for both tissue engineering and in vivo stimulation of other tissue-resident stem cells. In addition, MSCs possess immunosuppressive activities and have been successfully used to treat Graft vs. Host Disease [Le Blanc et al., 2004] and as a source for gene therapy (Osteogenesis Imperfecta) [Le Blanc et al., 2005].Although there is ...

Our data establish PDCD10 as the gene responsible for CCM in families linking to the CCM3 locus. The discovery of the third gene involved in inherited forms of CCM, after KRIT1 and Malcavernin, is an important step toward dissecting the molecular pathophysiology of this disease.

Whole brain radiation therapy (WBRT) alone versus WBRT and radiosurgery for the treatment of brain metastases.

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The expression pattern of CCM3/PDCD10 in multiple organ systems displays similarities to CCM1 and CCM2. PDCD10/CCM3 is highly expressed in the neurovascular unit and in the arterial endothelium of structures within multiple organ systems, including the brain. These data provide additional information about CCM3 expression and its role in lesion development and pathogenesis.

Background and Purpose-Mutations in CCM2 (MGC4607 or malcavernin) cause familial cerebral cavernous malformation (CCM), an autosomal dominant neurovascular disease. Both the function of this molecule and the pathogenesis of the disease remain elusive. Methods-We analyzed the mRNA expression of Ccm1 and Ccm2 in the embryonic and postnatal mouse brain by in situ hybridization. Subsequently, we generated CCM2-specific polyclonal antibodies and tested their specificity using transient transfection experiments in various cell lines. We then investigated CCM2 protein expression in cerebral and extracerebral tissues by Western blot analysis as well as immunohistochemistry and compared these results with CCM1 (KRIT1) protein expression. Results-In situ analysis shows similar temporal and spatial expression patterns for Ccm1 and Ccm2, although Ccm1 expression appears more widespread. Immunohistochemical analysis shows that CCM2 is expressed in various human organs, most noticeably in the arterial vascular endothelium. As is the case with CCM1, CCM2 is not expressed in other vascular wall elements such as smooth muscle cells or the venous circulation. Within cerebral tissue, it is also expressed in pyramidal neurons, astrocytes, and their foot processes. In extracerebral tissues, CCM2 is present in various epithelial cells necessary for blood-organ barrier formation. Conclusions-CCM1 and CCM2 have similar expression patterns during development and postnatally thereafter. Given the fact that the disease phenotypes caused by mutations in either gene are clinically and pathologically indistinguishable, the significant overlap in expression pattern supports the hypothesis that both molecules are involved in the same pathway important for central nervous system vascular development. (Stroke. 2006;37:518-523.)

S100A4/Mts-overexpressing mice have thick elastic laminae and mild pulmonary arterial hypertension (PAH), and the occasional older mouse develops occlusive neointimal lesions and perivascular inflammation. We hypothesized that a vasculotropic virus could induce neointimal lesions in the S100A4/Mts1 mouse by facilitating breakdown of elastin and migration and proliferation of smooth muscle cells. To test this hypothesis, we infected S100A4/Mts1 mice with gammaherpesvirus 68 (gammaHV68). We observed, 6 mo after gammaHV68 [4 x 10(3) plaque-forming units (PFU)], perivascular inflammation in 10/15 S100A4/Mts1 mice and occlusive neointimal formation in 3/10 mice, accompanied by striking degradation of elastin. We then compared the early response after high-dose gammaHV68 (4 x 10(6) PFU) in C57Bl/6 and S100A4/Mts1 mice. In S100A4/Mts1 mice only, significant PAH, muscularization of distal vessels, and elastase activity were observed 6 wk after gammaHV68. These features resolved by 3 mo without neointimal formation. We therefore infected mice with the M1-gammaHV68 strain that reactivates from latency with higher efficiency and observed neointimal lesions at 3 mo in 2/5 C57Bl/6 (5-9% of vessels) and in 5/5 S100A4/Mts1 mice (13-40% of vessels) accompanied by mild PAH, heightened lung elastase activity, and intravascular viral expression. This suggested that enhanced generation of elastin peptides in S100A4/Mts1 mice may promote increased viral entry in the vessel wall. Using S100A4/Mts1 PA organ culture, we showed, in response to elastase activity, heightened production of elastin peptides associated with invasion of inflammatory cells and intravascular viral antigen. We therefore propose that early viral access to the vessel wall may be a critical determinant of the extent of vascular pathology following reactivation.

Whole brain radiation therapy (WBRT) alone versus WBRT and radiosurgery for the treatment of brain metastases.