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Penn Laboratory for Ocular Angiogenesis

The Penn lab has a long-standing interest is in the molecular basis of ocular angiogenesis. The over-reaching goal of our research is to characterize the process of retinal angiogenesis, and to begin to develop preventive strategies based on understanding gained from in vitro and in vivo studies. During the past decade, we have continued to refine and characterize our experimental models, and we find them particularly well suited for investigations of the cellular and molecular aspects of angiogenesis in blinding diseases. We now propose to utilize these tools (e.g., retinal microvascular endothelial cells, Muller cells and retinal astrocytes in culture, and rodent models of retinopathy of prematurity and laser-induced choroidal neovascularization) to address two basic aims:

  • The first aim is to investigate the mechanism by which non-steroidal anti-inflammatory drugs (NSAID) inhibit angiogenesis. The angiostatic activity of NSAID has long been recognized in several tumor types. However, their potency and the role of their target enzyme, cyclo-oxygenase, in ocular angiogenesis is largely undefined, although it is clear that important differences exist between the effects of NSAID on angiogenesis in tumors and in the retina. We seek to define the precise role of cyclo-oxygenase products, prostanoids, and their receptors in retinal and choroidal angiogenesis.
  • The second aim is to investigate the angiostatic effect of penetrating ocular injury. Recently, we have discovered that dry needle penetration of the eye globe inhibits abnormal retinal and preretinal neovascularization. We call this phenomenon “ocupuncture”. The pattern of the inhibitory influence implies that an antiangiogenic factor is released from the wound site and diffuses throughout the eye, exerting a stronger effect in the injured quadrant and a weaker effect in the opposite quadrant. Vitreous protein harvested from injured eyes shows potent angiostatic activity, both in VEGF-treated retinal microvascular endothelial cells and when administered to rats induced to display ROP-like pathology. This suggests that the ultimate answer to limiting retinal angiogenesis may lie within the retina's natural battery of inducible factors. We have begun the search for candidates using 2-D gel electrophoresis and gene microarray analysis to identify the responsible factors. We plan to characterize this phenomenon, using several genomics and proteomics methods to determine which one or more of these factors may play a role in the injury effect. Identification of endogenous retinal angiostatic factors will allow for the development of novel therapies for retinal neovascular pathologies. Therapeutic strategies that seek to regulate the synthesis and release of candidate endogenous factors provide distinct advantages over administration of exogenous agents.

Nearly half of the Penn lab's research support derives from contracts to the pharmaceutical industry (two angiostatic agents currently in clinical trials are the product of drug discovery efforts by our lab), while the other half is from long-standing NIH grants.

Selected Publications:

Werdich, X.Q. and Penn, J.S. (2005) Differentiation of the roles of Src, Fyn and Yes kinases in VEGF-mediated endothelial cell events by RNA interference. Angiogenesis 8(4):315-326.

Barnett, J.M., McCollum, G.W., Fowler, J.A., Duan, J.J-W., Kay, J.D., Liu, R-Q., Bingaman, D.P. and Penn, J.S. (2007) Pharmacologic and genetic manipulation of MMP-2 and -9 affects retinal neovascularization in rodent models of OIR. Invest Ophthalmol Vis Sci. 48(2):907-15.

Penn, J.S., Madan, A., Caldwell, R.B., Bartoli, M., Caldwell, R.W. and M.E. Hartnett. (2008) Vascular Endothelial Growth Factor in Eye Disease. Prog. Ret. Res., 27:331-371.

Barnett, J.M., McCollum, G.M. and Penn, J.S. (2009) The Role of Cytosolic Phospholipase A2 in Retinal Neovascularization. Invest Ophthalmol Vis Sci. Aug 6. [Epub ahead of print] PMID: 19661235

Yanni, S.E., Barnett, J.M., Clark, M.L. and Penn, J.S. (2009) PGE2 receptor EP4 is a potential therapeutic target for the treatment of pathological ocular angiogenesis. Invest Ophthalmol Vis Sci. Jun 3. [Epub ahead of print] PMID: 19494202

The Penn lab currently includes two visiting professors, a postdoctoral fellow, three graduate students, an M.D., Ph.D. student, three research staff members, a medical student and a group of undergraduates.

The lab uses several primary cell cultures to examine stimulation of retinal growth factor production by hypoxia (e.g., Müller cells, retinal astrocytes, retinal pigmented epithelial cells) and angiogenic response to growth factor stimulation (e.g., retinal microvascular endothelial cells).

 

Retinal ischemia leads to hypoxia, which stimulates angiogenic growth factor production by Müller cells and other retinal cell types. Prominent among these factors is VEGF, a potent endothelial cell-selective mitogen. VEGF binds to receptor tyrosine kinases on the surface of nearby capillaries, stimulating cell proliferation, migration and tube formation.

The Penn lab developed a widely used and well-validated rat model of retinopathy of prematurity. This image shows one of the ways, isolectin B4 staining, by which the retinal vasculature of newborn rats is examined and evaluated in the Penn lab.

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