Gelatin promotes rapid restoration of the blood brain barrier after acute brain injury

Gelatin coating of brain implants is known to provide considerable benefits in terms of reduced inflammatory sequalae and long-term neuroprotective effects. However, the mechanisms for gelatin's protective role in brain injury are still unknown. To address this question, cellular and molecular markers were studied with quantitative immunohistochemical microscopy at acute (<2 hours, 1,3 days), intermediate (1-2 weeks) and long-term time points (6 weeks) after transient insertion of stainless steel needles into female rat cortex cerebri with or without gelatin coating. Compared to non-coated controls, injuries caused by gelatin coated needles showed a significantly faster resolution of post-stab bleeding/leakage and differential effects on different groups of microglia cells. While similar levels of matrix metalloproteinase (MMP-2 and MMP-9, two gelatinases) was found for coated and noncoated needle stabs during the first week, markedly increased levels of both MMPs was seen for gelatin-coated but not non coated needle stabs after 2 weeks. Neuronal populations and activated astrocytes were largely unaffected. In conclusion, the beneficial effects of gelatin may be the combined results of faster healing of the blood brain barrier curtailing leakage of blood borne molecules/cells into brain parenchyma and to a modulation of the microglial population response favoring restitution of the injured tissue. These findings present an important therapeutic potential for gelatin coatings in various disease, injury and surgical conditions. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd.