FIG. 5.

Morphological plasticity of differentiated glial restricted progenitors (GRP). Human GRP were differentiated for 10 days with bone morphogenetic protein 4 (BMP-4) or ciliary neurotrophic factor (CNTF), challenged for an additional four days with an alternate factor, and evaluated by phase contrast microscopy for morphological characteristics. Panels A–D (GRP pre-differentiated with BMP-4) and panels E–H (GRP pre-differentiated with CNTF), show the morphological phenotypes for each condition and indicate that BMP-4 and CNTF exhibited striking morphological plasticity when challenged with fetal bovine serum (FBS) and assume the fibroblast-like, flat-cell morphology typical of FBS treatment. These changes were less obvious when BMP-4 treated cells were challenged with CNTF and CNTF-treated cells are challenged with BMP-4. In contrast, GRP pre-differentiated with FBS displayed only minor morphological changes when switched to an alternate treatment. Scale bar=25 μm.