Reorganization of lesion margins by GDAs. (a,c) Control lesions; (b,d) transplanted lesions. Control lesions at (a) 4 days and particularly at (c) 8 days after injury have a dense meshwork of hypertrophic cell bodies and processes of endogenous astrocytes within lesion margins that is typical of forming glial scar tissue. (b) At 4 days after injury and transplantation, 'flares' of hPAP+ GDAs (green) are interwoven with realigned host GFAP+ astrocytes within lesion margins (the caudal margin is shown). Processes of both transplanted GDAs and host astrocytes are oriented towards the lesion center. Note that hPAP+ GDAs are not GFAP+. (d) At 8 days after injury and transplantation, GDAs have effected a reduction in host astrogliosis and a striking realignment of host GFAP+ astrocytes compared with the control (c). (e) Quantification of the alignment of host GFAP+ processes in lesion margins. The angles measured between each pair of GFAP+ processes in control (n = 100) and GDA-transplanted lesion margins (n = 100) are graphically displayed in a histogram. Each bin along the x-axis represents the angle between a pair of processes: 0° is parallel and 90° is perpendicular. The y-axis indicates the number of pairs of GFAP+ processes within each bin. Note the striking difference in alignment of GFAP+ host astrocytic processes in margins of GDA-transplanted lesions versus controls. GDA-transplanted lesions have an average angle of just 11.6° (median 7°) between paired processes, versus 59.4° (median 61°) for control lesion margins. Statistical analysis: p < 0.0001, t-test. Scale bars: (a,c,d) 100 μm; (b) 50 μm.