Sciatic conditioned medium increases survival, proliferation and differentiation of retinal cells in culture

Many evidences clearly demonstrate that Schwann cells provide trophic support for neurons. Different cytokines, including neurotrophins (NTs), are produced and released by Schwann cells. These trophic molecules play an important role on neuronal survival either during the development or during adult life. Cytokines have also a pivotal role on neuronal regeneration after lesions occurring during pathological conditions. The aim of this work was to study the effect of sciatic conditioned medium (SCM) on rat retinal cells maintained in culture. Our results show that treatment with SCM obtained after 14 days in vitro (SCM 14 day) induced a three-fold increase in protein content of the culture after 48 h in vitro and this value remained equally high up to 72 h. This effect was totally blocked either by addition of 30 microM BAPTA-AM, an intracellular calcium chelator, 15 microM fluorodeoxyuridine, an inhibitor of cell division, or 10 microM genistein (geni) plus 1.25 microM chelerythrine chloride (CC), the two last ones inhibitors of tyrosine kinases and protein kinase C, respectively. SCM induced an increase in [(3)H]-choline uptake and [(3)H]-thymidine incorporation of retinal cells. SCM also stimulated an increase in cytoplasmic processes outgrowth of retinal cells and survival of retinal ganglion cells. Our results clearly suggest that soluble molecules released by sciatic nerve fragments are able to increase the proliferation and survival of retinal cells in culture.