How to infuse heterologous human adult liver-derived progenitor cells safely?

Background and Aims: Mesenchymal stem cell (MSC) infusions are currently evaluated in numerous clinical trials, but therapy-induced thrombi have been described in several patients. Most MSCs in fact express a procoagulant activity (PCA) linked to tissue factor (TF) expression. The aim of this study was to optimise infusion protocols using Heterologous Human Adult Liver-derived Progenitor Cells (HHALPC) without inducing a thrombogenic risk after the infusion. We studied infusions of high cell doses in metabolic patients and low cell doses in cirrhotic patients, known to a have rebalanced haemostasis. Method: First cell dose escalation was studied using a xenotransplant animal model (healthy Wistar rat, with or without anticoagulants). Then the crucial role of TF in PCA was confirmed using flow chambers (shear stress model). Finally, we characterized disseminated intravascular coagulation (DIC) induced by HHALPCs in vitro and investigated how to control the induced thrombotic and haemorrhagic risks in whole blood of healthy and cirrhotic patients (by fibrin generation model and tubing loops, mimicking blood flow). Results: In vivo we showed that the thrombogenic risk induced by HHALPC infusions is dose dependent. High cell doses such as 50x106 cells / kg induced DIC 1h after transplantation with a significant decrease in platelets (p < 0.01), fibrinogen (p < 0.001), and coagulation factors II, V and VIII (p < 0.01) compared to control rats infused only with PBS. Infusions of lower cell doses, such as 5x106 cells / kg did not activate the coagulation cascade. Adding anticoagulants during infusions of high cell doses, such as heparin (300 I.U./ 5x106 cells) or a combination of heparin (10 I.U./ 5x106 cells) and bivalirudin can control the thrombogenic risk. By tubing loop model we showed that HHALPCs activate the coagulation cascade in a less explosive way in decompensated cirrhotic patient’s blood compared to healthy volunteers. HHALPCs only induce a significant decrease in platelets (p < 0.01) and fibrinogen (p < 0.01) and not in coagulation factors. Conclusion: Low doses of MSCs (5x106 cells / kg) expressing TF do not induce a thrombogenic risk, and could thus be used in future clinical trials treating acute decompensated cirrhotic patients while monitoring platelet and fibrinogen levels. The thrombogenic risk induced by infusions of higher cell doses can be controlled by adding anticoagulants and could therefore be used to treat metabolic patients.