Anti-CCL9 monoclonal antibody, clone 73206

Spermatogonial stem cells are the only stem cells in the body that transmit genetic information to offspring. Although growth factors responsible for self-renewal of these cells are known, the factors and mechanisms that attract and physically maintain these cells within their microenvironment are poorly understood. Mice with targeted disruption of Ets variant gene 5 (Etv5) show total loss of stem/progenitor spermatogonia following the first wave of spermatogenesis, resulting in a Sertoli cell-only phenotype and aspermia. Microarray analysis of primary Sertoli cells from Etv5 knockout (Etv5(-/-)) versus wildtype (WT) mice revealed significant decreases in expression of several chemokines. Chemotaxis assays demonstrated that migration of stem/progenitor spermatogonia toward Etv5(-/-) Sertoli cells was significantly decreased compared to migration toward WT Sertoli cells. Interestingly, differentiating spermatogonia, spermatocytes, and round spermatids were not chemoattracted by WT Sertoli cells, whereas stem/progenitor spermatogonia showed a high and significant chemotactic index. Rescue assays using recombinant chemokines indicated that C-C-motif ligand 9 (CCL9) facilitates Sertoli cell chemoattraction of stem/progenitor spermatogonia, which express C-C-receptor type 1 (CCR1). In addition, there is protein-DNA interaction between ETV5 and Ccl9, suggesting that ETV5 might be a direct regulator of Ccl9 expression. Taken together, our data show for the first time that Sertoli cells are chemoattractive for stem/progenitor spermatogonia, and that production of specific chemokines is regulated by ETV5. Therefore, changes in chemokine production and consequent decreases in chemoattraction by Etv5(-/-) Sertoli cells helps to explain stem/progenitor spermatogonia loss in Etv5(-/-) mice. STEM CELLS 2010; 28: 1882-1892

Myeloid-derived suppressor cells (MDSCs) are the major negative regulators of immune responses and expand in numerous tumor models. They contribute to tumor progression and metastasis, and are involved in limiting the effects of cancer immunotherapy. To selectively target MDSCs, it is required to understand the molecular mechanisms that drive MDSC expansion. The mechanisms of their accumulation in tumor tissue have been extensively studied, while the mechanisms of their expansion in lymphoid organs have been rarely explored. The spleen is the largest lymphoid organ in the human body. A previous study by our group reported that a negative immune status in the spleen facilitated tumor growth, with MDSCs being the major immunosuppressive cells. In the present study, a murine H22 orthotopic hepatoma model was established and the mechanisms of splenic MDSC accumulation were studied, including MDSC proliferation, apoptosis and chemotaxis. The proliferation and apoptosis of splenic MDSCs did not differ between normal and tumor-bearing (TB) mice. Cytokine array and ELISA of splenic tissues indicated elevated chemokine (C-C motif) ligand 9 (CCL9) levels in TB mice. Furthermore, splenic macrophages were able to secrete CCL9. Flow cytometric analysis revealed that splenic MDSCs from TB mice also overexpressed C-C motif chemokine receptor 1 (CCR1), the receptor for CCL9. Taken together, the present results indicate that CCL9 secreted by splenic macrophages induces a CCR1-dependent accumulation of MDSCs in the spleen in a murine H22 hepatoma model.