Procoagulant in vitro effects of clinical cellular therapeutics in a severely injured trauma population
Mitchell J. George, Karthik S. Prabhakara, Naama E. Toledano Furman, Brijesh S. Gill, Charles E. Wade, Bryan A. Cotton, Andrew P. Cap, Scott D. Olson, Charles S. Cox
Abstract
Abstract Clinical trials in trauma populations are exploring the use of clinical cellular therapeutics (CCTs) like human mesenchymal stromal cells (MSC) and mononuclear cells (MNC). Recent studies demonstrate a procoagulant effect of these CCTs related to their expression of tissue factor (TF). We sought to examine this relationship in blood from severely injured trauma patients and identify methods to reverse this procoagulant effect. Human MSCs from bone marrow, adipose, and amniotic tissues and freshly isolated bone marrow MNC samples were tested. TF expression and phenotype were quantified using flow cytometry. CCTs were mixed individually with trauma patients’ whole blood, assayed with thromboelastography (TEG), and compared with healthy subjects mixed with the same cell sources. Heparin was added to samples at increasing concentrations until TEG parameters normalized. Clotting time or R time in TEG decreased relative to the TF expression of the CCT treatment in a logarithmic fashion for trauma patients and healthy subjects. Nonlinear regression curves were significantly different with healthy subjects demonstrating greater relative decreases in TEG clotting time. In vitro coadministration of heparin normalized the procoagulant effect and required dose escalation based on TF expression. TF expression in human MSC and MNC has a procoagulant effect in blood from trauma patients and healthy subjects. The procoagulant effect is lower in trauma patients possibly because their clotting time is already accelerated. The procoagulant effect due to MSC/MNC TF expression could be useful in the bleeding trauma patient; however, it may emerge as a safety release criterion due to thrombotic risk. The TF procoagulant effect is reversible with heparin. Significance statement Stem cells are currently under investigation as a treatment for sequela of trauma like brain or lung injury. However, stem cells express tissue factor (TF) that causes rapid blood clotting. It is demonstrated that stem cells make blood from trauma patients, which clot faster. A potential antidote to this effect is heparin, a common and inexpensive blood thinner. It is believed that stem cells used in trauma studies should be risk-stratified based on their TF expression.