sentences:  Problems with working with MAPCs proved difficult to several laboratories who were keen to co-operate in expanding the use of MAPCs.In a report in "Nature", Dr. Rudolf Jaenisch at MIT was quoted by "Nature" stating that "I have not seen any convincing data showing that anyone has repeated the chimaera experiment, so I don't think this part of it is true", referring to the claim by Verfaillie that MAPCs when injected into mouse embryos contribute to all tissues.The same article also quoted Orkin as saying that the material transfer agreement (MTA) for procuring these cells were so restrictive that his group refused to work with them.