Effect of cytokine-induced alterations in extracellular matrix composition on diabetic retinopathy-relevant endothelial cell behaviors.

Retinal vascular basement membrane (BM) thickening is an early structural abnormality of diabetic retinopathy (DR). Recent studies suggest that BM thickening contributes to the DR pathological cascade; however, much remains to be elucidated about the exact mechanisms by which BM thickening develops and subsequently drives other pathogenic events in DR. Therefore, we undertook a systematic analysis to understand how human retinal microvascular endothelial cells (hRMEC) and human retinal pericytes (hRP) change their expression of key extracellular matrix (ECM) constituents when treated with diabetes-relevant stimuli designed to model the three major insults of the diabetic environment: hyperglycemia, dyslipidemia, and inflammation. TNFα and IL-1ß caused the most potent and consistent changes in ECM expression in both hRMEC and hRP. We also demonstrate that conditioned media from IL-1ß-treated human Müller cells caused dose-dependent, significant increases in collagen IV and agrin expression in hRMEC. After narrowing our focus to inflammation-induced changes, we sought to understand how ECM deposited by hRMEC and hRP under inflammatory conditions affects the behavior of naïve hRMEC. Our data demonstrated that diabetes-relevant alterations in ECM composition alone cause both increased adhesion molecule expression by and increased peripheral blood mononuclear cell (PBMC) adhesion to naïve hRMEC. Taken together, these data demonstrate novel roles for inflammation and pericytes in driving BM pathology and suggest that inflammation-induced ECM alterations may advance other pathogenic behaviors in DR, including leukostasis.

Hypoxia inducible factor signaling in breast tumors controls spontaneous tumor dissemination in a site-specific manner.

Hypoxia is a common feature in tumors and induces signaling that promotes tumor cell survival, invasion, and metastasis, but the impact of hypoxia inducible factor (HIF) signaling in the primary tumor on dissemination to bone in particular remains unclear. To better understand the contributions of hypoxia inducible factor 1 alpha (HIF1α), HIF2α, and general HIF pathway activation in metastasis, we employ a PyMT-driven spontaneous murine mammary carcinoma model with mammary specific deletion of Hif1α, Hif2α, or von Hippel-Lindau factor (Vhl) using the Cre-lox system. Here we show that Hif1α or Hif2α deletion in the primary tumor decreases metastatic tumor burden in the bone marrow, while Vhl deletion increases bone tumor burden, as hypothesized. Unexpectedly, Hif1α deletion increases metastatic tumor burden in the lung, while deletion of Hif2α or Vhl does not affect pulmonary metastasis. Mice with Hif1α deleted tumors also exhibit reduced bone volume as measured by micro computed tomography, suggesting that disruption of the osteogenic niche may be involved in the preference for lung dissemination observed in this group. Thus, we reveal that HIF signaling in breast tumors controls tumor dissemination in a site-specific manner.