Fig. 3

Injection of I-5 hydrogel eliminates cystic cavities. a–d Absence of cavity spaces after I-5 injection. Representative images of transverse spinal cord sections stained with eriochrome cyanine and eosin (a, b) or GFAP antibodies (c, d). Spinal cord sections were obtained from animals 4 weeks after PBS (a, c) or I-5 injection (b, d). The sections shown are from the epicenter and 1.2 mm rostral (+1.2 mm) or caudal (−1.2 mm) to it. Asterisks indicate cystic cavities. In animals with I-5 injection, there was no sizable cavity observed. Instead, eosin-stained ECM-like tissue was observed in the central epicenter region, of which boundary was indicated by black arrows (b). Scale bars represent 200 μm. e Three-dimensional reconstructions of the spinal cord tissues from animals with PBS or I-5 injection. Scale bars represent 1 mm. f–h Quantification graphs showing the volumes of cavity (f), pathologic tissue (g) and myelinated white matter (h). * and *** indicate p < 0.05 and p < 0.001, respectively, by two-tailed Student’s t-test. N = 8 animals per group. Error bars represent the SEM. i–l Representative images of transverse spinal cord sections at the epicenter stained with an Iba1 antibody. The sections were obtained from animals 1 week (i, j) or 4 weeks (k, l) after injection. Magnified images of the boxed regions are shown in iʹ–lʹ. Asterisks indicate cystic cavities. Scale bars indicate 200 μm (i–l) and 50 μm (i'–l'). m Graph showing quantification of the Iba1 immunofluorescence intensity at 4 weeks after injection (5 weeks after injury). The fluorescence intensity was measured in three ROIs: one each in dorsal, lateral, and ventral regions containing the border between the residual white matter and damaged tissue with or without cavities at the epicenter. * and ** indicate p < 0.05 and p < 0.01, respectively, by two-tailed Student’s t-test. N = 6 animals per group. Error bars represent the SEM