This controversy session aimed to discuss two provocative questions: 1) Were we right to initiate clinical trials? 2) Do we need the cells? J Martin from London justified the move from animal experiments to clinical trials.
He emphasized that there is no optimal animal for heart disease and pre-clinical data will never be perfect. He stressed the braveness needed to take the first step in translating new concepts into clinical trials. In his rebuttal, BK Fleischmann from Bonn emphasized in animal data the low percentage of adult stem cells in the bone marrow, low transdifferentiation efficacy , poor engraftment and survival and lack of integration of the cells with the infarcted heart. In addition, he reviewed recent reports suggesting that bone marrow mesenchymal stem cells can produce bone in the scar and stressed the need for long-term follow-up. The next question was “Do we need the cells?”. S Janssens from Leuven reviewed the defective endogenous repair mechanism of patients with MI and heart failure. He showed in vitro data that support the concept that BM cells can produce many therapeutic cytokines and may have positive paracrine effect on myocardial healing and repair – without real alternatives. He also highlighted the need to improve the infarct environment by reducing oxidative stress and microvascular obstruction. KC Wollert from Hanover in his rebuttal critically reviewed the clinical data available today and gave the impression that the therapeutic benefit is marginal. In addition, he criticised the administration of cells to patients not under clinical trial protocols and without ethics committee approval.
Helmut Drexler from Hanover concluded the session and said that it has taken 25 years to find the best way to myocardial reperfusion, and thus, we should not expect cell therapy strategy to be established within a few years. I believe that the train has left the station and we cannot stop it or bring it back. To determine the status of cell therapy in acute MI, the efficacy demonstrated in early pioneering clinical trials in Europe should be reproduced in multi-national trials in high-risk patients. In addition, concomitant bench work is needed to identify those subpopulations of stem cells which will provide the most therapeutic benefit-together with safety- and to improve the delivery, engraftment and therapeutic efficacy of the cells.
Stem cells: from bedside to bench again?
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