Abstract
Purpose: :
To assess expression of TLR4 in mouse retina as a function of age, and to examine whether the expression is associated with the decline in neurogenesis. In addition, to examine the functional relevance of TLR4 to retinal neurogenesis, by comparing retinal neurogenesis in TLR4-deficient mice relative to wild-type control mice.
Methods: :
At different postnatal stages, mice were injected with the proliferating marker 5-Bromo-2'-deoxyuridine (BrdU) and tested by immunohistochemistry for proliferation and neuronal differentiation of the newly form cells. Level of retinal TLR4 was also assessed.
Results: :
Deficiency in TLR4 resulted in increased proliferation and neuronal differentiation of the ciliary epithelium stem cells in the mouse postnatal retina. The inhibitory effect of TLR4 on the retinal stem-cell proliferation mediated through the adaptor MyD88. Differences in progenitor cell proliferation and differentiation in ciliary epithelium between wild type and TLR4 deficient mice were evident only as far as six-days postnatal, and were correlated with the lower levels of TLR4 relative to adult.
Conclusions: :
These observations introduce the TLR4, and perhaps other members of Toll-like receptors family, as new player in the complex process of retinogenesis.
Keywords: development • ciliary body • microglia