Recent progress in mammalian cloning

A review on reproductive biotechnologies for conservation of endangered mammalian species

This review describes the use of modern reproductive biotechnologies or assisted reproductive techniques (ART) including artificial insemination, embryo transfer/sexing, in vitro fertilization, gamete/embryo micromanipulation, semen sexing, genome resource banking, and somatic cell nuclear transfer (cloning) in conservation programs for endangered mammalian species. Such biotechnologies allow more offspring to be obtained from selected parents to ensure genetic diversity and may reduce the interval between generations. However, the application of reproductive biotechnologies for endangered free-living mammals is rarer than for endangered domestic breeds. Progress in ART for non-domestic species will continue at a slow pace due to limited resources, but also because the management and conservation of endangered species is biologically quite complex. In practice, current reproductive biotechnologies are species-specific or inefficient for many endangered animals because of insufficient knowledge on basic reproduction like estrous cycle, seasonality, structural anatomy, gamete physiology and site for semen deposition or embryo transfer of non-domestic species.

Osteogenic stem cells and orthopedic engineering: summary and update

The use of osteogenic stem cells or osteoprogenitors to reconstruct skeletal tissues is a popular area of research investigation with high potential for successful use of tissue-engineering principles in orthopedics. Recent studies demonstrate the migration of marrow-derived stem cells to skeletal sites and the proliferation and differentiation at local tissue sites and support possibilities for assessing the successful uses of human osteoprogenitors in the treatment of bone deficiency diseases. In addition, the development of gene therapy procedures in these and other conditions is now considered an achievable goal with the use of these primitive marrow cells.

Gender reassignment and assisted reproduction: present and future reproductive options for transsexual people

Transsexual people who want transition to their desired gender have to undergo hormonal and surgical treatments, which lead to irreversible loss of their reproductive potential. This paper argues that transsexual people should be offered the same options as any person that risks losing their germ cells because of treatment for a malignant disease. Indeed, transsexual women (male-to-female transsexual patients) may be given the option to store spermatozoa before they start hormonal therapy, so that their gametes may be used in future relationships. This may be especially important for the many transsexual women who identify as lesbians after their transition. Conversely, transsexual men (female-to-male transsexual patients) may be offered storage of oocytes or ovarian tissue, possibly obtained at the time of their oophorectomy. Current technology offers transsexual people the possibility to obtain children who are genetically their own in their future relationships and the option of gamete banking should therefore be discussed before starting hormonal and surgical reassignment treatment. This is particularly important for transsexual people who are diagnosed and treated at a young age.

Temporal and spatial aspects of fragmentation in early human embryos: possible effects on developmental competence and association with the differential elimination of regulatory proteins from polarized domains

This study examined the relationship between blastomere fragmentation in cultured human embryos obtained by in-vitro fertilization and the effect of fragmentation on the distribution of the following eight regulatory proteins found to be: (i) localized in the mature oocyte in subplasmalemmal, polarized domains; and (ii) unequally inherited by the blastomeres during cleavage: leptin, signal transducer and activator of transcription 3 (STAT3), Bax, Bcl-x, transforming growth factor beta 2 (TGF beta 2), vascular endothelial growth factor (VEGF), c-kit and epidermal growth factor R (EGF-R). Four basic patterns of fragmentation were observed. The severity of the impact of each type of fragmentation on the affected blastomere(s) and the developmental competence of the embryo appeared to be a function of the unique temporal and spatial features associated with the particular fragmentation pattern(s) involved in each instance. The findings demonstrate that certain patterns of fragmentation can result in the partial or near total loss of the eight regulatory proteins from specific blastomeres and that the developmental potential of the affected embryo can be particularly compromised if it occurs during the 1- or 2-cell stages. In contrast, fragmentation from portions of a fertilized egg or a blastomere(s) in a 2-cell embryo that do not contain the protein domains, or the complete loss by fragmentation of a regulatory protein domain-containing blastomere after the 4-cell stage does not necessarily preclude continued development to the blastocyst, although the normality and developmental potential of the embryo may be compromised. The possible association between fragmentation and apoptosis was examined by annexin V staining of plasma membrane phosphatidylserine and TUNEL analysis of blastomere DNA. No direct correlation between fragmentation and apoptosis was found following the analyses of fragmented embryos with these two markers. However, while we suggest that changes in cell physiology unrelated to apoptosis are the more likely causes of fragmentation, we cannot exclude the possibility that fragmentation itself may be an initiator of apoptosis if critical ratios or levels of developmentally important proteins are altered by partial or complete elimination of their polarized domains. The findings are discussed with respect to the possible developmental significance of regulatory protein polarization in human oocytes and preimplantation stage embryos.