Philippe Hammel

Pulmonary dysfunction and impaired granulocyte homeostasis result in poor survival of Jam-C-deficient mice†

Jam‐C−/− mice exhibit growth retardation and multilobular pneumonia concomitant with poor survival of the mice under conventional housing conditions. The deficient mice present a mega‐oesophagus and have altered airway responsiveness. In addition, the number of circulating granulocytes is increased in Jam‐C−/− mice as compared to control animals. These phenotypes probably reflect the different functions of JAM‐C expressed by endothelial and mesenchymal cells. Indeed, the deregulation in the number of circulating granulocytes is caused by the lack of JAM‐C expression on endothelial cells since rescuing endothelial expression of the protein in the Jam‐C−/− mice is sufficient to restore homeostasis. More importantly, the rescue of vascular JAM‐C expression is accompanied by better survival of deficient mice, suggesting that endothelial expression of JAM‐C is mandatory for animal survival from opportunistic infections and fatal pneumonia. Copyright

Expression and function of junctional adhesion molecule-C in human and experimental arthritis

Junctional adhesion molecule-C (JAM-C) is an adhesion molecule involved in transendothelial migration of leukocytes. In this study, we examined JAM-C expression in the synovium and investigated the role of this molecule in two experimental mouse models of arthritis. JAM-C expression was investigated by reverse transcriptase-polymerase chain reaction and immunohistochemistry. The effects of a monoclonal anti-JAM-C antibody were assessed in antigen-induced arthritis (AIA) and K/BxN serum transfer-induced arthritis. JAM-C was expressed by synovial fibroblasts in the lining layer and associated with vessels in the sublining layer in human and mouse arthritic synovial tissue. In human tissue, JAM-C expression was increased in rheumatoid arthritis (RA) as compared to osteoarthritis synovial samples (12.7 ± 1.3 arbitrary units in RA versus 3.3 ± 1.1 in OA; p < 0.05). Treatment of mice with a monoclonal anti-JAM-C antibody decreased the severity of AIA. Neutrophil infiltration into inflamed joints was selectively reduced as compared to T-lymphocyte and macrophage infiltration (0.8 ± 0.3 arbitrary units in anti-JAM-C-treated versus 2.3 ± 0.6 in isotype-matched control antibody-treated mice; p < 0.05). Circulating levels of the acute-phase protein serum amyloid A as well as antigen-specific and concanavalin A-induced spleen T-cell responses were significantly decreased in anti-JAM-C antibody-treated mice. In the serum transfer-induced arthritis model, treatment with the anti-JAM-C antibody delayed the onset of arthritis. JAM-C is highly expressed by synovial fibroblasts in RA. Treatment of mice with an anti-JAM-C antibody significantly reduced the severity of AIA and delayed the onset of serum transfer-induced arthritis, suggesting a role for JAM-C in the pathogenesis of arthritis.

Sushi repeat protein X-linked 2, a novel mediator of angiogenesis

On appropriate stimuli, quiescent endothelial cells start to proliferate and form de novo blood vessels through angiogenesis. To further define molecular mechanisms accompanying the activation of endothelial cells during angiogenesis, we identified genes that were differentially regulated during this process using microarray analyses. In this work, we established a regulatory role for Sushi repeat protein X‐linked 2 (Srpx2) in endothelial cell remodeling during angiogenesis. In particular, silencing of Srpx2 using small interfering RNAs (siRNAs) specifically attenuated endothe‐lial cell migration and delayed angiogenic sprout formation. In vivo, Srpx2 expression was detected in de novo formation of blood vessels in angiogenic tissues by in situ mRNA hybridization and immunostaining. Pulldown experiments identified Srpx2 as a ligand for vascular uPAR, a key molecule involved in invasive migration of angiogenic endothelium. Immunostaining revealed coexpression of the Srpx2 and uPAR on vascular endothelium. These findings suggest that Srpx2 regulates endothelial cell migration and tube formation and provides a new target for modulating angiogenesis.—Miljkovic‐Licina, M., Hammel, P., Garrido‐Urbani, S., Bradfield, P. F., Szepetowski, P., Imhof, B. A. Sushi repeat protein X‐linked 2, a novel mediator, of angiogenesis. FASEBJ. 23, 4105‐4116 (2009). www.fasebj.org

Cooperative expression of junctional adhesion molecule-C and -B supports growth and invasion of glioma.

Brain invasion is a biological hallmark of glioma that contributes to its aggressiveness and limits the potential of surgery and irradiation. Deregulated expression of adhesion molecules on glioma cells is thought to contribute to this process. Junctional adhesion molecules (JAMs) include several IgSF members involved in leukocyte trafficking, angiogenesis, and cell polarity. They are expressed mainly by endothelial cells, white blood cells, and platelets. Here, we report JAM‐C expression by human gliomas, but not by their normal cellular counterpart. This expression correlates with the expression of genes involved in cytoskeleton remodeling and cell migration. These genes, identified by a transcriptomic approach, include poliovirus receptor and cystein‐rich 61, both known to promote glioma invasion, as well as actin filament associated protein, a c‐Src binding partner. Gliomas also aberrantly express JAM‐B, a high affinity JAM‐C ligand. Their interaction activates the c‐Src proto‐oncogene, a central upstream molecule in the pathways regulating cell migration and invasion. In the tumor microenvironment, this co‐expression may thus promote glioma invasion through paracrine stimuli from both tumor cells and endothelial cells. Accordingly, JAM‐C/B blocking antibodies impair in vivo glioma growth and invasion, highlighting the potential of JAM‐C and JAM‐B as new targets for the treatment of human gliomas.

Targeting Olfactomedin-like 3 Inhibits Tumor Growth by Impairing Angiogenesis and Pericyte Coverage

Antiangiogenic drugs have been used as anticancer agents to target tumor endothelial cells or pericytes. Because of limited efficacy of the current monotherapies, there is a strong demand for the dual targeting of endothelial cells and pericytes. Here, we identify Olfactomedin-like 3 (Olfml3) as a novel proangiogenic cue within the tumor microenvironment. Tumor-derived Olfml3 is produced by both tumor endothelial cells and accompanying pericytes and deposited in the perivascular compartment. Blockade of Olfml3 by anti-Olfml3 antibodies is highly effective in reducing tumor vascularization, pericyte coverage, and tumor growth. In vitro, Olfml3 targeting is sufficient to inhibit endothelioma cell migration and sprouting. Olfml3 alone or through binding to BMP4 enhances the canonical SMAD1/5/8 signaling pathway required for BMP4-induced angiogenesis. Therefore, Olfml3 blockade provides a novel strategy to control tumor growth by targeting two distinct cell types within the tumor microenvironment using a single molecule. Mol Cancer Ther; 11(12); 2588–99. ©2012 AACR.

Junctional adhesion molecule B interferes with angiogenic VEGF/VEGFR2 signaling

De novo formation of blood vessels is a pivotal mechanism during cancer development. During the past few years, antiangiogenic drugs have been developed to target tumor vasculature. However, because of limitations and adverse effects observed with current therapies, there is a strong need for alternative antiangiogenic strategies. Using specific anti‐junctional adhesion molecule (JAM)‐B antibodies and Jam‐b‐deficient mice, we studied the role in antiangiogenesis of JAM‐B. We found that antibodies against murine JAM‐B, an endothelium‐specific adhesion molecule, inhibited microvessel outgrowth from ex vivo aortic rings and in vitro endothelial network formation. In addition, anti‐JAM‐B antibodies blocked VEGF signaling, an essential pathway for angiogenesis. Moreover, increased aortic ring branching was observed in aortas isolated from Jam‐b‐deficient animals, suggesting that JAM‐B negatively regulates proangiogenic pathways. In mice, JAM‐B expression was detected in de novo‐formed blood vessels of tumors, but anti‐JAM‐B antibodies unexpectedly did not reduce tumor growth. Accordingly, JAM‐B deficiency in vivo had no impact on blood vessel formation, suggesting that targeting JAM‐B in vivo may be offset by other proangiogenic mechanisms. In conclusion, despite the promising effects observed in vitro, targeting JAM‐B during tumor progression seems to be inefficient as a stand‐alone antiangiogenesis therapy.—Meguenani, M., Miljkovic‐Licina, M., Fagiani, E., Ropraz, P., Hammel, P., Aurrand‐Lions, M., Adams, R. H., Christofori, G., Imhof, B. A., Garrido‐Urbani, S. Junctional adhesion molecule B interferes with angiogenic VEGF/VEGFR2 signaling. FASEB J. 29, 3411‐3425 (2015). www.fasebj.org

Biodegradable and plasma-treated electrospun scaffolds coated with recombinant Olfactomedin-like 3 for accelerating wound healing and tissue regeneration.

Three‐dimensional biomimetic scaffolds resembling the native extracellular matrix (ECM) are widely used in tissue engineering, however they often lack optimal bioactive cues needed for acceleration of cell proliferation, neovascularization, and tissue regeneration. In this study, the use of the ECM‐related protein Olfactomedin‐like 3 (Olfml3) demonstrates the importance and feasibility of fabricating efficient bioactive scaffolds without in vitro cell seeding prior to in vivo implantation. First, in vivo proangiogenic properties of Olfml3 were shown in a murine wound healing model by accelerated wound closure and a 1.4‐fold increase in wound vascularity. Second, subcutaneous implantation of tubular scaffolds coated with recombinant Olfml3 resulted in enhanced cell in‐growth and neovascularization compared with control scaffolds. Together, our data indicates the potential of Olfml3 to accelerate neovascularization during tissue regeneration by promoting endothelial cell proliferation and migration. This study provides a promising concept for the reconstruction of damaged tissue using affordable and effective bioactive scaffolds.