Figure 5.

 Schematic diagram with proposal pathways of intraocular bone formation. Inflammatory cells synthesise interleukin (IL-1), tumour necrosis factor (TNF-α), and transforming growth factor beta-1 (TGF β1). IL-1 and TNF-α stimulate retinal pigment epithelium (RPE) to produce TGF β1 and bone morphogenic protein-7 (BMP-7). Both TGF β1 released from RPE and inflammatory cells trigger epithelial-mesenchymal transformation (from RPE cells to RPE metaplastic cells). BMP-7 balances these effects by inhibiting this process. On the other hand, increased BMP-7, if excessive, can cause transdifferentiation from RPE metaplasia to osteoblasts.