Abstract
Purpose: :
Retinoblastoma is the most common intraocular tumor of childhood. Postlaminar optic nerve invasion is associated with extraocular relapse and an increased risk for metastases to the central nervous system. A unique feature of invading retinoblastoma cells is that they contact non-myelinated axons within the retina and optic nerve head to then encounter myelinated axons in the postlaminar region of the optic nerve. We have previously shown that chick embryo retinas grow myelinated axons in vitro and can be cocultured with glioma cells. In this study, we have tested a new model for retinoblastoma optic nerve invasion by coculturing WERI retinoblastoma cells with myelinated optic nerve axons in vitro with or without the Rho-kinase (ROCK) inhibitor Y27632.
Methods: :
Retinas from E7 chick embryos were cultivated for two days in petridishes precoated with laminin-1 until an adequate axonal layer was seen on the substrate. WERI retinoblastoma cells were then placed close to and onto the axons under microscopic visualization. In certain experiments, the Rho-kinase inhibitor Y27632 was added to the cultures at a concentration of 100 µM. To monitor cellular behavior, timelapse microscopy videos were captured for 24 h. The videos were then examined for cell proliferation, cell motility and cell-axon interactions
Results: :
In coculture with retinal axons, WERI retinoblastoma cells interacted with the axons, showed a motile phenotype and proliferated. Interestingly, the retinoblastoma cells were able to create niches within the axonal layer by actively moving axons sideways. Cells treated with Y27632 showed a higher degree of cell-matrix adhesion and more cell extensions. Y27632 resulted also in less motility and proliferation of the WERI cells.
Conclusions: :
Coculturing optic nerve axons obtained from chick embryos with retinoblastoma cells may serve as a useful model to study mechanisms of retinoblastoma optic nerve invasion beyond the lamina cribrosa. Inhibition of Rho-kinase in WERI retinoblastoma cells resulted in a more differentiated phenotype with less motility and proliferation.
Keywords: retinoblastoma • optic nerve • retinal culture