Endogenous TNFalpha suppression of neovascularization in corneal stroma in mice.

PURPOSE: To examine the role of tumor necrosis factor alpha (TNFalpha) in stromal neovascularization in injured cornea in vivo and in cytokine-enhanced vessel-like endothelial cell tube formation in vitro. METHODS: An in vitro model of angiogenesis was used to examine the roles of TNFalpha on tube formation by human umbilical vein endothelial cells (HUVECs) cocultured with fibroblasts on induction by transforming growth factor beta1 (TGFbeta1) and vascular endothelial growth factor (VEGF). Central cauterization was used to induce stromal neovascularization in corneas of wild-type (WT) and TNFalpha-null (Tnfalpha(-/-)) mice. At 7, 14, or 21 days of injury, experimental mice were killed, and the eyes were enucleated and subjected to histologic and immunohistochemical examination and real-time reverse transcription-polymerase chain reaction. RESULTS: HUVECs formed a vessel-like tube structure on the fibroblast feeder layer. Adding TGFbeta1, VEGF, or both augmented vessel-like tube formation by HUVECs cocultured with fibroblasts. Adding TNFalpha (5 ng/mL) completely abolished the formation of tube-like structures despite the presence or absence of TGFbeta1 or VEGF in coculture. In vivo, cauterization of the central cornea induced the formation of CD31(+) new vessels surrounding the limbus in WT mice. More prominent central stromal neovascularization accompanied by increased expression of TGFbeta1 and VEGF was found in Tnfalpha(-/-) mice compared with WT mice. CONCLUSIONS: In addition to inhibiting TGFbeta1 and VEGF expression by fibroblasts, endogenous TNFalpha may counter the induction effects of TGFbeta1 and VEGF on vascular endothelial cells and may block neovascularization.

Loss of osteopontin perturbs the epithelial-mesenchymal transition in an injured mouse lens epithelium.

We previously reported that osteopontin (OPN), a matrix structural glycophosphoprotein, is upregulated in the injured mouse lens prior to the epithelial-mesenchymal transition (EMT). Here, we investigated the role of this protein in EMT of the lens epithelium during wound healing. The crystalline lens was injured by needle puncture in OPN-null (KO, n=40) and wild-type (WT, n=40) mice. The animals were killed at day 1, 2, 5, and 10 postinjury. Immunohistochemistry was employed to detect alpha-smooth muscle action (alphaSMA), a marker of EMT, collagen type I, transforming growth factor beta1 (TGFbeta1), TGFbeta2, and phospho-Smad2/3. Cell proliferation was assayed by examining uptake of bromodeoxyuridine (BrdU). The results showed that injury-induced EMT of mouse lens epithelium, as evaluated by histology, expression pattern of alphaSMA and collagen I, was altered in the absence of OPN with reduced phospho-Smad2/3 signaling. Upregulation of TGFbeta1 and TGFbeta2 in the epithelium was also inhibited. Cell proliferation was more active in KO mice as compared with WT mice at day 1 and 2, but not at day 5 and 10. An in vitro experiment shows OPN facilitates cell adhesion of lens epithelial cell line. OPN is required for activation of Smad2/3 signal in an injured lens epithelium and lens cell EMT.

Excess biglycan causes eyelid malformation by perturbing muscle development and TGF-alpha signaling.

Tissue morphogenesis during development is regulated by growth factors and cytokines, and is characterized by constant remodeling of extracellular matrix (ECM) in response to signaling molecules, for example, growth factors, cytokines, and so forth. Proteoglycans that bind growth factors are potential regulators of tissue morphogenesis during embryonic development. In this study, we showed that transgenic mice overexpressing biglycan under the keratocan promoter exhibited exposure keratitis and premature eye opening from noninfectious eyelid ulceration due to perturbation of eyelid muscle formation and the failure of meibomian gland formation. In addition, in vitro analysis revealed that biglycan binds to TGF-alpha, thus interrupting EGFR signaling pathways essential for mesenchymal cell migration induced by eyelid epithelium. The defects of TGF-alpha signaling by excess biglycan were further augmented by the interruption of the autocrine or paracrine loop of the EGFR signaling pathway of HB-EGF expression elicited by TGF-alpha. These results are consistent with the notion that under physiological conditions, biglycan secreted by mesenchymal cells serves as a regulatory molecule for the formation of a TGF-alpha gradient serving as a morphogen of eyelid morphogenesis.

Fibroblast growth factor 2: roles of regulation of lens cell proliferation and epithelial-mesenchymal transition in response to injury.

PURPOSE: To examine the role of fibroblast growth factor 2 (FGF2) in regulating lens cell proliferation and epithelial-mesenchymal transition (EMT) in response to injury. METHODS: The amount of FGF2 protein was determined in healing, injured rat lenses by enzyme immunoassay. The effects of FGF2 and transforming growth factor beta2 (TGFbeta2) on cell proliferation of alphaTN4 cells (a mouse lens epithelial cell line) were determined. FGF2-knockout mice were used to further examine the role of endogenous FGF2 on injury-induced epithelial cell proliferation and EMT. The anterior lens capsule was injured by a hypodermic needle under both general and topical anesthesia in one eye of 34 fgf2+/+ mice and 42 fgf2-/- mice. At days 2, 5, and 10 post-injury the mice were sacrificed following a 2 h labeling period with bromo-deoxyuridine (BrdU). The number of BrdU-positive cells in each specimen was determined. RESULTS: A capsular break caused a 10 fold increase of FGF2 protein accumulated in rat lens 14 days after injury. Addition of 3.43 ng/ml FGF2 enhanced proliferation of alphaTN4 cells. This occurred in the presence or absence of exogenous TGFbeta2, that has an inhibitory effect on alphaTN4 cell proliferation. Significantly fewer BrdU-labeled cells were found in fgf2-/- mice than in fgf2+/+ mice during healing post-injury. However, lacking FGF2 did not alter the expression patterns of alpha-smooth muscle actin and collagen type I, markers of EMT in lens cells. CONCLUSIONS: Endogenous FGF2 is required for increased cell proliferation but not essential for EMT during the lens response to injury.