Vitronectin gene expression in the adult human retina

PURPOSE. TO determine whether vitronectin (Vn), a plasma protein and extrac ellular matrix molecule that is also a prominent constituent of drusen, is synthesized by cells in the adult human retina. METHODS. The distribution of Vn in the normal adult human retina was examin ed using antibodies to circulating plasma Vn and to the multimeric, heparin -binding form that is most prevalent in extravascular tissues. Evidence of Vn transcription by retinal cells was analyzed by in situ hybridization and also by reverse transcription of total RNA derived from dissociated human or mouse photoreceptors followed by amplification using polymerase chain re action (RT-PCR). RESULTS. Cytoplasmic immunoreactivity for plasma Vn or multimeric Vn was de tected in photoreceptors, in a subpopulation of neurons situated in the inn er retina, and in vitreous hyalocytes. Extracellular labeling was limited p rimarily to Bruch's membrane and the retinal vasculature. At the transcript ional level, Vn mRNA was localized to both photoreceptors and ganglion cell s by in situ hybridization. The in situ findings were corroborated by RT-PC R using total RNA from dissociated mouse or human photoreceptor cells. CONCLUSIONS. The results constitute the first evidence for Vn gene expressi on by adult neurons in the mammalian central nervous system. The identifica tion of the photoreceptors as a cellular source of Vn suggests that these c ells have the potential to make a biosynthetic contribution to the Vn that is found in drusen.