Abstract
Abstract: :
Purpose: To test the regenerative ability of monkey retinal ganglion cell (RGC) axons in organ cultures. Methods: Fresh retinas were obtained from marmoset monkeys between the first postnatal day (P1) and 12 years of age. Organotypic cultures were prepared with the ganglion cell layer facing a substrate of poly-D-lysin (PDL) and laminin-1. Controls were explanted on laminin-2, PDL alone, matrigel or collagen IV. The numbers of axons growing out between 1 and 4 days were determined by microscopy. Expression of the integrins a5b1 and a6b1 was monitored with RT-PCR, immunohistochemistry, immunoblotting and 2-d-electrophoresis (IEF) followed by MALDI-MS-sequencing. The RGC types contributing to regeneration were labelled with DiI. Results: Massive axonal regeneration of more than 40.000 axons per retina was observed in laminin-1-coated dishes, but not on laminin-2 or PDL, or matrigel, or collagen IV. There was an age-dependent decrease in the number of axons, but adult marmoset retina showed a reproducibly high rate of axonal growth. b1-integrin and GAP-43 was expressed in all control retinas and in all explants. a5 integrin was expressed in blood capillaries a6 integrin was not expressed in controls but was selectively upregulated in explants facing laminin-1. Retrograde staining of the RGCs revealed that only RGCs, but not other retinal neurons contributed to regeneration. On the other hand, all types of RGCs contributed to regrowth of axons and retained their characteristic dendritic shapes. Conclusions: Primate neurons retain the ability to regenerate their axons in vitro. The principal requirements for growth are contact to laminin-1, expression of a6-integrin and sustained expression of GAP-43.
Keywords: ganglion cells • regeneration • animal model