Protective role of neuronal and lymphoid cannabinoid CB2 receptors in neuropathic pain.

The study was designed to investigate the feasibility of using an acidic gelatin hydrogel as a biodegradable vehicle for basic fibroblast growth factor (bFGF). bFGF was incorporated by polyion complexation into a biodegradable hydrogel prepared by cross-linking acidic gelatin with the isoelectric point of 4.9. The dried hydrogel (sized to 2x1 mm) was hydrated with bFGF aqueous solution including different doses of bFGF (20, 50, 125, 250 and 500 ng) and implanted into a rabbit corneal pocket (2.5x2 mm). As a control group, the gelatin hydrogel without bFGF or bFGF alone (500 ng) was used. Corneal angiogenesis was evaluated by biomicroscopy, corneal fluorescein angiography and histology for 21 days. Photographs were taken and corneal angiogenesis was evaluated by image analysis. The hydrogel degraded with time after its implantation into the corneal pocket. Experimental eyes receiving the hydrogel containing more than 50 ng of bFGF demonstrated significant corneal angiogenesis. Control eyes and eyes receiving the hydrogel containing 20 ng of bFGF showed no corneal angiogenesis. Corneal angiogenesis, which occurred on the 3rd or 4th day after implantation, reached maximal growth on about day 7 and regressed from day 10 after implantation. The area of angiogenesis showed a dose-dependency on bFGF. The gelatin hydrogel itself induced neither angiogenesis nor inflammation. These results suggested that acidic gelatin hydrogel releases bioactive bFGF with its biodegradation, resulting in corneal neovascularization.