Regenerative medicine is based on the recognition of the potential diagnostic and therapeutic use of Stem Cells (SC). This special cell population is caracterized by three main characteristics: undifferentiation (they have not developed into mature cells that perform a specific function), self-renewal (they are able to divide and produce copies of themselves indefinately), and differentiation capability (they have the potential to become specialized cell types under specific conditions). According to their origin and differentiation capability, different types of SC are recognized.
Human embryonic stem cells (hESC) were first reported in 1998 and since then hESC research has become a field of constant progress and improvement. The specific characteristics of hESC made them a valuable tool not only for research in human development, gene control, pharmacological testing and other basic research approaches but also a potential tool for future therapeutic indications. All this potential scientific and medical benefits would not have been made possible without the knowledge acquired by the improvements made in assisted reproduction, In Vitro Fertilization, and specifically in the handling and optimised in vitro culture of the human embryo to the blastocyst stage. When couples that have undergone Assisted Reproduction Techniques do not have a parental project for their embryos anymore, certain legislations consider the possibility of donation for research. Many human embryos donated for research have been used for the derivation of hESC. Human embryonic stem cells are derived from human embryos that are 4 to 7 days old. The inner cell mass cells are harvested and cultured in specific conditions to develop pluripotent stem cells that can be grown indefinitely in the laboratory. The main characteristics of such cells are their pluripotentiality and their self-renewal capacity. Established hESC lines can be maintained in culture for research activities mostly regarding basic aspects of differentiation and self renewal and for the production of cells for cell-based therapies, when proved safe for clinical use.
Somatic stem cells (SSC) are rare undifferentiated tissue-specific cells present in adult tissues and organs that are defined by the capacity to renew themselves and to differentiate into specialized cell types. They are usually in a quiescent state (G0 phase) and located in a protective environment named the niche. They proliferate through asymmetric cell division, giving rise to one replacement stem cell and one transit amplifying cell. The interactions with the stem cell niche are crucial to this process. SSC have been isolated from several tissue sources, including the central nervous system, bone marrow, retina and skeletal muscle, suggesting that most adult tissues potentially contain the SSC population. This specific cell cluster possesses a diverse differentiation repertoire ranging from unipotential adult stem cells capable of generating one specific cell type to oligopotent cells that produce a limited range of differentiated cell lineages according to their location. SSC are regulated by a specific physiological microenvironment within the niche, and they are different in their cellular composition, structure and location in different tissues. Niches have been identified and characterized in the hair follicle bulge and interfollicular regions of the epidermis, in the intestinal crypts, at the periosteum and blood vessels for HSC, neural stem cells in the subventricular and subgranular zone and in the mouse and human endometrium and myometrium.
Commonly abbreviated as iPS cells or iPSCs, they are a type of pluripotent stem cell artificially derived from a non-pluripotent cell, typically an adult somatic cell, by inducing a "forced" expression of certain genes. IPSCs were first produced in 2006 from mouse cells and in 2007 from human cells. This has been cited as an important advancement in stem cell research, as it may allow researchers to obtain pluripotent stem cells without the need of embryos. These cells also constitute an important tool in research and, as hESC may have potential therapeutic uses. iPS cells are typically derived by transfection of certain stem cell-associated genes into non-pluripotent cells, such as adult fibroblasts. Transfection is typically achieved through viral vectors, such as retroviruses. Research is actively ongoing to achieve protocols that obviate the use of viral transfection and genomic integration. Induced Pluripotent Stem Cells are believed to be very similar to embryonic stem cells and the full extent of their possible differences with hESC is still being assessed.
Other cell types such as spermatogonial stem cells and cells obtained from parthenogenetic embryos have proved to hold pluripotency characteristics and also constitute active fields of research related to human reproduction and embryology.
Being aware of the importance of such an emerging field of research directly related to our activity, the ESHRE has settled a Special Interest Group in Stem Cells. The SIG started its activity in Madrid (ESHRE 19th Annual Meeting, 2003) and pre-congress courses have been organised in most annual meetings (Madrid, Prague, Lyon, Barcelona), in some cases in collaboration with other SIGs such as the Reproductive Genetics and the SIG in Ethics and Law. The SIG Stem Cells is of interest for ESHRE members who are involved in the present and future developments in hESC research. The aims of the SIG Stem cells are the promotion of the study and discussion of all aspects of hESC research as well as the provision of a forum for the exchange of information between scientists in this area. It has to be pointed out that a certain number of IVF laboratory pioneers and leaders are now actively involved in hESC research, making this field of particular interest for the ESHRE. We presume that the interest will be growing in the next future.
SIG Coordination
Future activities
Become a member
hESCreg
Links
Archive