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Normal Aging Involves Altered Expression of Growth Factors in the Rat Choroid

¹ Department of Ophthalmology, University of Tennessee Health Science Center, Memphis.
² Department of Physiology, Southern Illinois University School of Medicine, Carbondale.

Address correspondence to Jena J. Steinle, PhD, Assistant Professor, Department of Ophthalmology, University of Tennessee Health Science Center, 930 Madison Ave., Suite 722A, Memphis, TN 38163. E-mail: jjsteinle{at}utmem.edu

Normal aging of the choroid results in morphological and physiological changes. The growth factors that mediate these changes are unclear. Vascular endothelial growth factor (VEGF) binds its receptor 2, VEGFR2, to mediate vascular remodeling. Pigment epithelium-derived factor (PEDF) is an inhibitor of angiogenesis produced by retinal pigmented epithelial (RPE) cells. Angiopoietin1 (Ang-1) binds its receptor Tie-2 to recruit mural cells to stabilize vessels. To investigate age-related changes in growth factor activities in aged choroidal vasculature, real-time polymerase chain reaction and protein analysis of VEGF, VEGFR2, PEDF, Ang-1, and Tie-2 were completed on rat choroid/RPE complexes at 8, 22, and 32 months. VEGF messenger RNA (mRNA) peaked at 22 months, whereas protein levels were significantly decreased by 32 months. Both mRNA and protein levels of PEDF were significantly decreased with age. Ang-1 protein levels were not altered, whereas Tie-2 had increased protein levels with age. These results indicate that normal aging involves temporal changes in many of the growth factors common in age-related disease.

Key Words: Aging • Choroid • Growth factors