Purpose:
To identify the types and distribution of structural proteins, neurofilaments, and astrocytic elements within the tree shrew lamina cribrosa and retro-laminar optic nerve.
Methods:
8 non-diseased eyes were obtained from 4 tree shrews, cut to 12 µm sections and slide mounted. Within the lamina cribrosa, single and double labeling studies using primary antibodies against collagen types I, III, IV, elastin and laminin were used to assess the distribution of structural proteins. Gomori Trichrome stain was used to provide an overview of the architecture of the lamina cribrosa region. To assess the distribution of neuronal and non-neuronal protein elements in the retro-laminar region, single and double labeling studies were made using primary antibodies against neurofilament 200, neurofilament M (125kD), GLAST, GFAP, myelin and endothelin receptor types A and B.
Results:
Transverse sections of the lamina cribrosa showed centrally radiating laminar beams inserting into the scleral canal. Similar to Albon, et al. (2004), collagens I and III, and elastin were found within the laminar beams, with collagen IV and laminin localized to the margins of the beams. In the retro-laminar NF-200 and NF-M labeled axons within the retro-laminar optic nerve. ED-A and ED-B were co-localized with GLAST, suggesting astrocytic expression.
Conclusions:
The tree shrew shows a well-developed lamina cribrosa composed of a similar arrangement of structural proteins, neurofilaments, and astrocytic elements to that found in higher primates. Thus, the tree shrew lamina may provide a model to study the pathologic changes within a connective tissue lamina in response to elevation of intraocular pressure that is less costly than current primate models.Reference: 1.) Alban J et al. IOVS 2005;46: ARVO E-Abstract 3514.Fig 1: Strong Collagen type IV labeling along the margins of the laminar beams in a transverse section through the tree shrew laminar region at the level of the sclera.
Keywords: lamina cribrosa • optic nerve • immunohistochemistry