Control of Bone Resorption by Semaphorin 4D Is Dependent on Ovarian Function

Osteoporosis is one of the most common bone pathologies, which are characterized by a decrease in bone mass. It is well established that bone mass, which results from a balanced bone formation and bone resorption, is regulated by many hormonal, environmental and genetic factors. Here we report that the immune semaphorin 4D (Sema4D) is a novel factor controlling bone resorption. Sema4D-deficient primary osteoclasts showed impaired spreading, adhesion, migration and resorption due to altered ß3 integrin sub-unit downstream signaling. In apparent accordance with these in vitro results, Sema4D deletion in sexually mature female mice led to a high bone mass phenotype due to defective bone resorption by osteoclasts. Mutant males, however, displayed normal bone mass and the female osteopetrotic phenotype was only detected at the onset of sexual maturity, indicating that, in vivo, this intrinsic osteoclast defect might be overcome in these mice. Using bone marrow cross transplantation, we confirmed that Sema4D controls bone resorption through an indirect mechanism. In addition, we show that Sema4D −/− mice were less fertile than their WT littermates. A decrease in Gnrh1 hypothalamic expression and a reduced number of ovarian follicles can explain this attenuated fertility. Interestingly, ovariectomy abrogated the bone resorption phenotype in Sema4D −/− mice, providing the evidence that the observed high bone mass phenotype is strictly dependent on ovarian function. Altogether, this study reveals that, in vivo, Sema4D is an indirect regulator of bone resorption, which acts via its effect on reproductive function

Tumor angiogenesis and progression are enhanced by Sema4D produced by tumor-associated macrophages

Increased evidence suggests that cancer-associated inflammation supports tumor growth and progression. We have previously shown that semaphorin 4D (Sema4D), a ligand produced by different cell types, is a proangiogenic molecule that acts by binding to its receptor, plexin B1, expressed on endothelial cells (Conrotto, P., D. Valdembri, S. Corso, G. Serini, L. Tamagnone, P.M. Comoglio, F. Bussolino, and S. Giordano. 2005. Blood. 105:4321–4329). The present work highlights the role of Sema4D produced by the tumor microenvironment on neoplastic angiogenesis. We show that in an environment lacking Sema4D, the ability of cancer cells to generate tumor masses and metastases is severely impaired. This condition can be explained by a defective vascularization inside the tumor. We demonstrate that tumor-associated macrophages (TAMs) are the main cells producing Sema4D within the tumor stroma and that their ability to produce Sema4D is critical for tumor angiogenesis and vessel maturation. This study helps to explain the protumoral role of inflammatory cells of the tumor stroma and leads to the identification of an angiogenic molecule that might be a novel therapeutic target

The CD100 Receptor Interacts with Its Plexin B2 Ligand to Regulate Epidermal γδ T Cell Function

Summaryγδ T cells respond rapidly to keratinocyte damage, providing essential contributions to the skin wound healing process. The molecular interactions regulating their response are unknown. Here, we identify a role for interaction of plexin B2 with the CD100 receptor in epithelial repair. In vitro blocking of plexin B2 or CD100 inhibited γδ T cell activation. Furthermore, CD100 deficiency in vivo resulted in delayed repair of cutaneous wounds due to a disrupted γδ T cell response to keratinocyte damage. Ligation of CD100 in γδ T cells induced cellular rounding via signals through ERK kinase and cofilin. Defects in this rounding process were evident in the absence of CD100-mediated signals, thereby providing a mechanistic explanation for the defective wound healing in CD100-deficient animals. The discovery of immune functions for plexin B2 and CD100 provides insight into the complex cell-cell interactions between epithelial resident γδ T cells and the neighboring cells they support

Prevention of Adoptively Transferred Diabetes in Nonobese Diabetic Mice with IL-10–Transduced Islet-specific Th1 Lymphocytes A Gene Therapy Model for Autoimmune Diabetes

Four pancreatic islet-specific CD4+ helper T (Th) 1 (Th1) clones and two Th1 clones transduced with an SRα promoter-linked murine IL-10 (mIL-10) cDNA of 2.0–6.0×10[6] cells were adoptively transferred to nonobese diabetic (NOD) mice at age 8 d. Cyclophosphamide (CY) was administered at age 37 d (plus CY), and the incidence of diabetes and the histological grade of insulitis were examined at age 47 d. After the adoptive transfer of IL-10–transduced Th1 cells, polymerase chain reaction (PCR) and reversetranscription (RT)-PCR detected the neo gene and the retrovirus vector-mediated IL-10 mRNA in situ in recipient islets, respectively. RT-PCR detected the decrease of IFN-γ mRNA relative to IL-10 mRNA in IL-10–transduced Th1 clones in vitro and also in recipient islets. All four wild type Th1 clones plus CY induced the insulitis grade of 2.75 and diabetes in 66% of recipient NOD mice. IL-10–transduced two Th1 clones plus CY induced periinsulitis with the grade of 1.43 and diabetes in 8.0%. The 1:1 mixture of wild type Th1 cells and IL-10–transduced Th1 cells plus CY induced periinsulitis with the grade of 1.85 and diabetes in 20%. The suppression of diabetes through decreasing IFN-γ mRNA by the tissue-specific delivery of IL-10 to pancreatic islets with IL-10–transduced Th1 cells affords us the starting basis to develop the gene therapy for autoimmune diabetes

Abrogation of Autoimmune Diabetes in Nonobese Diabetic Mice and Protection against Effector Lymphocytes by Transgenic Paracrine TGF-β1

Paracrine effect of transforming growth factor-β1 (TGF-β1) on autoimmune insulitis and diabetes was studied by transgenic production of the active form of porcine TGF-β1 (pTGF-β1) in pancreatic islet (islet) α cells in nonobese diabetic (NOD) mice under the control of rat glucagon promoter (RGP) (NOD-RGP-TGF-β1). None of 27 NOD-RGP-TGF-β1 mice developed diabetes by 45 wk of age, in contrast to 40 and 71% in male and female nontransgenic mice, respectively. None of the NOD-RGP-TGF-β1 mice developed diabetes after cyclophosphamide (CY) administration. Adoptive transfer of splenocytes of NOD-RGP-TGF-β1 mice to neonatal NOD mice did not transfer diabetes after CY administration. Adoptive transfer of three types of diabetogenic lymphocytes to NOD-RGP-TGF-β1 and nontransgenic mice after CY administration led to the lower incidence of diabetes in NOD-RGP-TGF-β1 mice versus that in nontransgenic mice: 29 vs. 77% for diabetogenic splenocytes, 25 vs. 75% for islet β cell–specific Th1 clone cells, and 0 vs. 50% for islet β cell–specific CD8+ clone cells, respectively. Based on these, it is concluded that autoimmune diabetes in NOD mice is not a systemic disease and it can be completely prevented by the paracrine TGF-β1 in the islet compartment through protection against CD4+ and CD8+ effector lymphocytes

Accelerated tumor growth in mice deficient in DNAM-1 receptor

Since the identification of ligands for human and mouse DNAM-1, emerging evidence has suggested that DNAM-1 plays an important role in the T cell– and natural killer (NK) cell–mediated recognition and lysis of tumor cells. However, it remains undetermined whether DNAM-1 is involved in tumor immune surveillance in vivo. We addressed this question by using DNAM-1–deficient mice. DNAM-1–deficient cytotoxic T lymphocyte (CTL) and NK cells showed significantly less cytotoxic activity against DNAM-1 ligand-expressing tumors in vitro than wild-type (WT) cells. The methylcholanthrene (MCA)-induced fibrosarcoma cell line Meth A expressed the DNAM-1 ligand CD155, and DNAM-1–deficient mice showed increased tumor development and mortality after transplantation of Meth A cells. Moreover, the DNAM-1–deficient mice developed significantly more DNAM-1 ligand-expressing fibrosarcoma and papilloma cells in response to the chemical carcinogens MCA and 7,12-dimethylbenz[a]anthracene (DMBA), respectively, than did WT mice. These results indicate that DNAM-1 plays an important role in immune surveillance of tumor development

The immunoreceptor adapter protein DAP12 suppresses B lymphocyte–driven adaptive immune responses

Human and mouse B cells lacking functional DAP12 are hyperresponsive, and DAP12 works with MAIR-II (CD300d) to negatively regulate B cell activity