M. J. George1, K. Prabhakara1, N. E. Toledano-Furman1, Y. Wang1, S. D. Olson1, B. S. Gill1, C. E. Wade1, C. S. Cox1 1University Of Texas Health Science Center At Houston,Pediatric Surgery,Houston, TX, USA
Introduction: Human mesenchymal stem cells (MSCs) have shown efficacy in reducing inflammation after trauma. Previous studies using bone marrow derived MSCs to treat traumatic brain injury (TBI) demonstrate downregulation of inflammatory biomarkers and preservation of central nervous system architecture. However, MSCs express tissue factor (TF) which stimulates coagulation. We hypothesize that MSCs exhibit procoagulant activity linked to TF expression. We evaluated pro-coagulant activity and tissue factor expression of five different tissue sources of MSCs from multiple donors.
Methods: Multiple MSC samples from bone marrow, adipose, amniotic fluid, umbilical cord, and bone marrow derived cell donors were tested. TF expression and phenotype were quantified using multi-parametric flow cytometry. Fluorescence-activated cell sorting (FACS) separated select samples into high and low tissue factor expressing populations to isolate TF as a test variable. Pro-coagulant activity of the MSCs was measured in-vitro using blood from healthy donors in thromboelastography (TEG) and pooled plasma in calibrated automated thrombogram (CAT). MSCs were tested at concentrations of 10^5 cells/mL, similar to clinical dosing.
Results: All MSC tissue types express pro-coagulant activity that directly correlates with expression of tissue factor. Specifically, time to clot formation measured by R time in TEG decreased logarithmically as percent cells expressing TF increased compared to untreated controls. A Pearson’s product-moment correlation demonstrated strong correlation between percent of control R time and cells expressing TF (r = 0.683, p < 0.0001) (Figure 1). Similarly, time to thrombin generation in CAT decreased with increasing TF expression. High TF expressing MSCs decrease R time more than low TF expressing MSCs when sorted from single samples using FACS.
Conclusion: Human MSCs demonstrate pro-coagulant activity related to TF expression and hasten the kinetics of clot formation. This effect was proven to be related to TF by demonstrating high TF expressing MSCs decrease TEG R time more than low TF expressing MSCs when sorted from the same sample.
