Select Committee on Science and Technology Written Evidence

Memorandum 66

Supplementary submission from Dr Stephen Minger, Director, Stem Cell Biology Laboratory, Wolfson Centre for Age-Related Disease, King's College London

  In response to your letter of 7 February, 2007 regarding the generation of interspecies embryos using somatic cell nuclear transfer.

  1)  I can see no reason for culturing the embryo beyond the 14 day limit as set out in the HFE Act. In reality, the embryo will only be cultured for five to seven days after nuclear transfer and activation until the formation of inner cell mass, at which the time the embryo is disaggregated and the inner cell mass is placed into culture to form human embryonic stem cells.

  2 & 3)  Like all embryonic stem cell lines, it will be important to determine that interspecies cloned stem cell lines are pluripotent, that is capable of differentiating into cells of all three germ layers and thus into a wide range of cell types. The general methods for determining pluripotency are to a) allow embryonic stem cells to spontaneously differentiate or to use differentiation protocols and then look for the generation of a number of cell types across the three germ layers using markers that recognise specific cell types; b) to inject undifferentiated cells into mice lacking an immune system and then analysing the resultant benign tumours (teratomas) that form for multilineage differentiation; and c) introduction of labelled undifferentiated stem cells into the inner cell mass of a developing blastocyst which is then implanted into a surrogate uterus. Pluripotency can thus be assessed by looking for the presence of marked cells throughout the organs and tissues of the resultant embryo or adult organism.

  It is my belief that the first two tests of pluripotency are sufficient to provide the necessary information, though there may be instances where the third test might be valuable. However, for our research projects we will rely solely on the use of teratomas and in vitro differentiation to assess pluirpotency.

  4)  There are likely to be a number of instances where implantation of human embryonic stem cell-derived populations into experimental animals will be necessary. These include for example, testing the neuronal differentiation pattern of cells transplanted into lesioned brain, assessing the contribution of stem cells to repair of the damaged spinal cord, and determining the ability of stem cells to integrate into damaged myocardium. These and other similar procedures all required Home Office approval and do not differ in any significant way from traditional preclinical testing of human cell populations in experimental animals.

  Many thanks for allowing me to respond to your queries.

February 2007

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