Aberrant profile of gene expression in cloned mouse embryos derived from donor cumulus nuclei.

Somatic cell nuclear transfer has successfully been used to clone several mammalian species including the mouse, albeit with extremely low efficiency. This study investigated gene expression in cloned mouse embryos derived from cumulus cell donor nuclei, in comparison with in vivo fertilized mouse embryos, at progressive developmental stages. Enucleation was carried out by the conventional puncture method rather than by the piezo-actuated technique, whereas nuclear transfer was achieved by direct cumulus nuclear injection.

Alternative solutions to the current situation of oocyte donation in Singapore.

The rising incidence of age-related female infertility in Singapore, coupled with the prohibition on commercialized oocyte donation and egg sharing, has resulted in a severe shortage of donor oocytes. Infertile women are routinely encouraged by fertility doctors here to seek their close relatives and friends as prospective oocyte donors, which does not alleviate the shortage. A number of alternative solutions are discussed.

Advances in oocyte cryopreservation technology will eventually blur the ethical and moral boundaries between compensated egg sharing and commercialized oocyte donation.

Compensated egg sharing was originally conceived as a patient self-help co-operative scheme to avoid overt 'commodification' of donor oocytes and prevent doctors and medical institutions from acting as 'brokers' of donated human material. As such, egg sharing is an ethically justifiable and much-preferred alternative to commercialized oocyte donation. However, recent advances in oocyte cryopreservation technology are likely to blur the ethical and moral boundaries between compensated egg sharing and commercialized oocyte donation.

The immunogenicity and immunomodulatory function of osteogenic cells differentiated from mesenchymal stem cells.

Multipotent mesenchymal stem cells (MSC) are reported to be immunoprivileged as well as immunosuppressive. Hence, they are ideal candidates for allogeneic transplantation to induce regeneration of diseased tissues and organs. However, it is not known whether MSC would retain their immunoprivileged and immunomodulatory properties after differentiating into the local cell types of the transplantation site.

International egg-sharing to provide donor oocytes for clinical assisted reproduction and derivation of nuclear transfer stem cells.

Recent advances in nuclear transfer technology for derivation of patient-specific stem cells have opened up new avenues of therapy for various human diseases. However, a major bottleneck is the severe shortage of human donor oocytes. Egg-sharing in return for subsidized fertility treatment has been suggested as an ethically justifiable and practical solution to ease the shortage of donor oocytes both for derivation of nuclear transfer stem cells and assisted reproduction.

Ethical issues in paying for long-distance travel and accommodation expenses of oocyte donors.

In many countries where the sale and purchase of donor oocytes is banned, a legal loophole often exploited is the use of free air tickets and hotel stay to entice prospective oocyte donors, in lieu of monetary payment. Such a means of procuring much-needed donor oocytes is ethically unsound. There is a lack of transparency and the personal motivation of the oocyte donor may be clouded by the desire for a 'free' holiday.

Loss of viability during freeze-thaw of intact and adherent human embryonic stem cells with conventional slow-cooling protocols is predominantly due to apoptosis rather than cellular necrosis.

A major challenge in the widespread application of human embryonic stem (hES) cells in clinical therapy and basic scientific research is the development of efficient cryopreservation protocols. Conventional slow-cooling protocols utilizing standard cryoprotectant concentrations i.e.

Combined effects of TGFbeta1 and BMP2 in serum-free chondrogenic differentiation of mesenchymal stem cells induced hyaline-like cartilage formation.

This study investigated the effects of TGFbeta1, BMP2 or a combination of both on the chondrogenic differentiation of mesenchymal stem cells (MSCs) in a serum-free micromass culture system in vitro. Putative MSCs harvested from the iliac crest of 4-5 month old New Zealand White Rabbits were expanded and cultured in three-dimensional high density micromass aggregate cultures containing TGFbeta1, BMP2 or a combination of both, in the absence of serum. After 14-20 days of culture, chondrogenic differentiation of the MSCs was assayed by toluidine blue staining, immunohistochemistry and semi-quantitative RT-RCR of type I collagen (CI) and type II collagen (CII).

The egg-sharing model for human therapeutic cloning research: managing donor selection criteria, the proportion of shared oocytes allocated to research, and amount of financial subsidy given to the donor.

Recent advances in human therapeutic cloning made by Hwang and colleagues have opened up new avenues of therapy for various human diseases. However, the major bottleneck of this new technology is the severe shortage of human donor oocytes. Egg-sharing in return for subsidized fertility treatment has been suggested as an ethically justifiable and practical solution to overcome the shortage of donor oocytes for therapeutic cloning.

Late-adhering human embryonic stem cell clumps during serial passage can yield morphologically 'normal-looking' colonies.

During serial passage of human embryonic stem (hES) cells, freshly-seeded hES cell clumps that do not adhere to the newly-plated murine embryonic fibroblast (MEF) feeder layer after culturing overnight, are routinely discarded with the changing of fresh culture media. Preliminary observations revealed that non-adhered hES cell clumps that were still viable possessed a distinct, rounded morphology with 'sharp,' clearly-defined edges. Typically >90% of 'viable' hES cell clumps with such morphology adhered after a further 24 hr of culture on newly-plated MEF.

Possible advantages of stem cell transfusion into the peripheral circulation, as opposed to localized transplantation in situ.

Studies to date have overlooked the possible limitations of transplanting stem cells locally (in situ), directly at the site of tissue or organ damage. This approach is contrary to the intrinsic physiological process of tissue and organ regeneration in vivo, which is thought to involve the activation of stem cells resident within the transplanted tissues or their mobilization from ectopic sites, in particular the bone marrow. Signaling pathways and other molecular processes within stem cells transplanted in situ may not be primed to achieve optimal tissue regeneration and may even be confused by the sudden rapid transition in the cellular microenvironment encountered during transplantation.