Use of Glycosyltransferase-Programmed Stereosubstitution (GPS) to Improve Targeted Cell Therapies in Traumatic Brain Injury

Abstract

Purpose: Traumatic Brain Injury (TBI) is the leading cause of injury-related death and disability in the US. Given the complex pathophysiological mechanisms that ensue following a TBI, solutions that involve mesenchymal stem cell-based therapies are particularly appealing. To date, successful implementation of stem cell therapies has been largely hindered by the inability to efficiently deliver therapeutic doses of cells to the CNS via a vascular route. The goal of this study was to assess whether modification of cell surface glycoproteins using Glycosyltransferase-Programmed Stereosubstitution (GPS), could improve cell delivery and cell integration at sites of brain injury. Methods: We surgically induced controlled brain injuries in rats, and at either 6 hours or 5 days following the injury, administered a tail vein injection with 200,000 GPS-modified or unmodified stem cells. All rats were sacrificed 24 hours following injection and brain tissue was fixed, sectioned and later inspected by fluorescent microscopy for quantitative analysis. Quantitative western blots of brain tissue following controlled injury were conducted at each of the above time point to assess E-selectin expression. Results: E-selectin expression was significantly higher in the rat brain 5 days post injury compared to 6 hours post injury. An increased number of cells were observed at the site of injury at 5 days compared to 6 hours post TBI (p=0.004). GPS modification did not seem to statistically increase cell homing to the site of injury. However, there was a trend, with a 20 % increase in the average number of modified cells reaching the injury site. Conclusion: These findings serve as persuasive logic to further pursue the use of cell surface ligand modification to enhance delivery of stem cells to the CNS.