Implantation of a new porous gelatin-siloxane hybrid into a brain lesion as a potential scaffold for tissue regeneration

Background: For brain tissue regeneration, a scaffold for migrated or transplanted cells with vessels is important if the tissue become pannecrotic. The present study was designed to determine whether the implantation of porous gelatin-siloxane hybrids can serve as a scaffold for brain tissue regeneration. Methods: We used male Wistar rats of 12-weeks old. A new porous gelatin-siloxane hybrid derived from the integration of gelatin and 3-(glycidoxypropyl) trimethoxysilane (GPSM) was implanted into a defect of the cerebral cortex, which was located at 3.0 mm anterior to 2.0 mm posterior of the bregma (5 mm in length) and 2.0-4.0 mm (2 mm in width) lateral to the midline, and the depth of the lesion was approximately 2.0 mm below the skull surface. The block of GPSM was presoaked in basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) or only vehicle, and the time of implantation was just after or at 30d of brain defect making. The animal was decapitated and the frozen sections were prepared. In order to identify the cell types in the newly formed tissue, immunohistochemical analysis was performed for N-acetylglucosamine oligomers (NAGO), an endothelial cell marker, GFAP, ionized calciumbinding adapter molecule-1 (Iba1), NeuN and bromodeoxyuridine (BrdU). Additionally, in order to determine whether BrdU-labeled cells differentiate into vascular endothelial, astroglial and microglial cells, double immunofluorescent studies were performed for BrdU and NAGO, GFAP or Iba1. Furthermore, we observed axonal growth into the scaffold by double staining for BrdU and MAP2. Results: The control brain showed distortion of the cerebral cortex and enlargement of the ipsilateral lateral ventricle (Fig.1 A, C). On the other hand, the GPSM implanted into the lesion remained at the same site for 60 days, kept integrity of the brain shape, and attached well to the surrounding brain tissues (Fig.1 B, D). Marginal cavities of the scaffolds were occupied by newly formed tissue (Fig.1 E), where newly produced vascular endothelial, astroglial and microglial cells were found with BrdU positivity. The numbers of those cells were dose-dependently increased with bFGF and EGF. Extension of dendrites was also found from the surrounding cerebral cortex to the newly formed tissue, especially with addition of bFGF and EGF. Conclusion: The present study showed that GPSM had biocompatibility. It can thus serve as a potential scaffold for cell migration, angiogenesis and dendrite elongation with dose-dependent effects of bFGF and EGF.