Stem cell controversy

The stem cell controversy is the consideration of the ethics of research involving the development and use of human embryos. Most commonly, this controversy focuses on embryonic stem cells. Not all stem cell research involves human embryos. For example, adult stem cells, amniotic stem cells, and induced pluripotent stem cells do not involve creating, using, or destroying human embryos, and thus are minimally, if at all, controversial. Many less controversial sources of acquiring stem cells include using cells from the umbilical cord, breast milk, and bone marrow, which are not pluripotent. Background Stem cell For many decades, stem cells have played an important role in medical research, beginning in 1868 when Ernst Haeckel first used the phrase to describe the fertilized egg which eventually gestates into an organism. The term was later used in 1886 by William Sedgwick to describe the parts of a plant that grow and regenerate. Further work by Alexander Maximow and Le

Understanding engraftment of cultured epidermal stem cells

Nicolas Grasset

The epidermis and its appendages protect our body from environmental hazards. Cells generated in the basal layer continuously replace the terminally differentiated keratinocytes that are shed off the epidermal surface. Long-term renewal depends on specific tissue cells, called stem cells. The epidermis can efficiently repair itself when wounded, thanks to the proliferation, migration and differentiation of the stem cells and their progeny. In extensive full-thickness burns, restoration of the epidermal barrier can only be achieved by means of autologous skin grafts. Cell therapy using cultured epithelium autografts (CEA) has been part of the therapeutic arsenal since the early eighties (Gallico et al., 1984; O'Connor et al., 1981) and it has saved the life of many patients worldwide. Paradoxically, little is known on the behavior of the transplanted stem cells and engraftment has remained variable. Unpublished data from our laboratory have shown that the number of stem cells decrease rapidly in transplanted CEA in humans. This further highlights the necessity to thoroughly comprehend the cellular and molecular mechanisms of stem cell engraftment. Several fundamental questions must be addressed, for example: 1) By which mechanisms do stem cells adjust to the stress of transplantation? 2) How many stem cells are required for long-term renewal of the regenerated epidermis? 3) Can one manipulate the niche? To thoroughly investigate the mechanisms of engraftment, it is critical to develop a predictable animal model since it is difficult to experiment on human. We have chosen the pig as a large animal model because clinical procedures used for CEA transplantation cannot be recapitulated in laboratory animals. Firstly, we have demonstrated that pig and human skin share many features. In particular, the skin of the pig contains keratinocyte stem cells that can be characterized by clonal analysis using the same criteria as in the human (holoclone, meroclone, paraclone). Secondly, we have reproducibly produced CEA, including some made from the progeny of a single EGFP-labeled keratinocyte stem cell. Thirdly, we have recapitulated in the pig all surgical procedures used to transplanting CEA in humans. Fourthly, CEA engraftment has been systematically investigated by histology, immunochemistry and clonal analysis. Fifthly, we have demonstrated that the number of stem cells rapidly decreases following CEA transplantation and that there is little apoptosis in transplanted CEA, which suggests that stem cells are rather lost through terminal differentiation. Collectively our results demonstrate that the pig is the best available model system to investigate the mechanisms that govern stem cell engraftment. Superior engraftment may be achieved by improving the grafting bed, by designing smart matrices to better mimic the niche, or by manipulating stem cell behavior. A better comprehension of stem cell engraftment will certainly benefit patients suffering from large burns and those with disabling skin diseases (e.g. dystrophic epidermolysis bullosa). It will also profit stem cell therapy at large since optimal engraftment is also needed for hematopoïetic, muscle and neural stem cells.

EPFL2008

Understanding engraftment of cultured epidermal stem cells

Nicolas Grasset

EPFL2008

Stem cell research in Switzerland

Human experimentation and stem cell research

Understanding engraftment of cultured epidermal stem cells

Understanding engraftment of cultured epidermal stem cells

Human experimentation and stem cell research

Stem cell research in Switzerland