Somatic Nuclear Transfer Technique Research Articles

Potential for Somatic Nuclear Transfer Technology in Domestic Chickens

The development of mammalian somatic nuclear transfer techniques by Wilmut et al. in 1997 provided a new option for conserving animal genetic resources; however, this technique cannot be applied directly to avian species due to the anatomical and physiological differences between avian and mammalian embryos. A basic strategy for producing nuclear transferred avian offspring with somatic nuclear transferred primordial germ cells (snt-PGCs) was described in 2002. Under this scenario, somatic nuclear offspring could be produced through germline chimeras by transferring snt-PGCs into the bloodstream of early chicken embryos. In the present study, a series of experiments have been carried out to produce somatic nuclear transferred chickens.

Dissection of Genetic Factors Modulating Fetal Growth in Cattle Indicates a Substantial Role of the Non-SMC Condensin I Complex, Subunit G (NCAPG) Gene

The increasing evidence of fetal developmental effects on postnatal life, the still unknown fetal growth mechanisms impairing offspring generated by somatic nuclear transfer techniques, and the impact on stillbirth and dystocia in conventional reproduction have generated increasing attention toward mammalian fetal growth. We identified a highly significant quantitative trait locus (QTL) affecting fetal growth on bovine chromosome 6 in a specific resource population, which was set up by consistent use of embryo transfer and foster mothers and, thus, enabled dissection of fetal-specific genetic components of fetal growth. Merging our data with results from other cattle populations differing in historical and geographical origin and with comparative data from human whole-genome association mapping suggests that a nonsynonymous polymorphism in the non-SMC condensin I complex, subunit G (NCAPG) gene, NCAPG c.1326T>G, is the potential cause of the identified QTL resulting in divergent bovine fetal growth. NCAPG gene expression data in fetal placentomes with different NCAPG c.1326T>G genotypes, which are in line with recent results about differential NCAPG expression in placentomes from studies on assisted reproduction techniques, indicate that the NCAPG locus may give valuable information on the specific mechanisms regulating fetal growth in mammals.

Commentary: “Re-Programming or Selecting Adult Stem Cells?”

The recent observations that embryonic stemness-associated genes could assist in the "de-differentiation" of adult skin fibroblast cells to "embryonic-like stem cells", using the "somatic cell nuclear transfer" techniques, have been interpreted as indicating a "re-programming" of genes. These reports have demonstrated a "proof of principle" approach to by-pass many, but not all, of the ethical, scientific and medical limitations of the "therapeutic cloning" of embryonic stem cells from embryos. However, while the interpretation that real "re-programming" of all those somatic fibroblastic differentiation genes might be correct, there does exists an alternative hypothesis of these exciting results. Based on the fact that multipotent adult stem cells exist in most, if not all, adult organs, the possibility exists that all these recent "re-programming" results, using the somatic nuclear transfer techniques, actually were the results of transferred rare nuclear material from the adult stem cells residing in the skin of the mouse, monkey and human samples. An examination of the rationale for this challenging hypothesis has been drawn from the hypothesis of the "stem cell theory of cancer", as well as from the field of human adult stem cells research.

Obtaiment of Pudu (Pudu pudu) deer Embryos by the Somatic Nuclear Transfer Technique

Los objetivos de este trabajo fueron los de producir embriones de pudu, obtenidos por la transferencia de nucleos de fibroblastos de la oreja de pudu en ovocitos de un rumiante domesticos que es el bovino. Para posteriormente en un trabajo futuro proceder a la transferencia de embriones de pudu, al utero de hembras receptoras sincronizadas de otra especie. Se obtuvieron biopsias de 1 mm aproximadamente del borde externo de la orejas de dos ciervos pudu machos del jardin zoologico Buin-Zoo, Santiago de Chile. Las lineas celulares han sido establecidas y conservadas segun los protocolos utilizados para las bovinos. Los ovocitos son obtenidos por puncion del complejo cumulos-ovocito (COC).desde ovarios de vacas recuperados del matadero. Cada ovocito es enucleado y fusionado con un fibroblasto aislado insertado bajo la zona pelucida. La fusion de membranas celulares es obtenida por choques electricos. En cuanto a la cronologia, observamos que al segundo dia se forma una etapa de dos blastomeras, al tercer dia morulas de 8 a 16 celulas, y desde el cuarto dia se ha diferenciado como blastocisto, el cual al septimo dia termina por eclosionar de la zona pelucida La obtencion de blastocistos embrionarios indica que es posible obtener embriones de pudu mediante clonaje heteroespecifico, aunque, el porcentaje de exito obtenido es relativamente bajo. Queda aun por verificar la viabilidad de los embriones asi obtenidos despues de la transferencia in utero

Embryonic stem cells and tissue engineering: delivering stem cells to the clinic

One of the challenges facing biomedical science is of its own making—namely, the progressive increase in lifespans. An increasing number of individuals require treatment and the treatments themselves have to work for longer. A shift in emphasis is therefore required towards biological approaches including the regeneration of tissues. Tissue engineering can be best defined by its goal—the design and construction in the laboratory of living components that can be used for the maintenance, repair or replacement of malfunctioning tissues. In this discipline, born in 1933 when tumour cells were wrapped in a polymer membrane and implanted into a pig,1 the life sciences and medicine come together with engineering in activities centred on three basic components—cells, scaffolds and signals. The development of tissue engineering has lately been spurred by the increased availability of cell sources, proteomics, the advent of new biomaterials, improvements in bioreactor design and increased understanding of healing. However, neither commercial development nor clinical application of tissue engineered products has kept pace with this rapidly evolving research. Industrial development has been hindered by difficulties in devising cost-efficient processes, guaranteeing product viability and satisfying the regulators. Nevertheless, the coming years will see a large increase in the number of patients benefiting from tissue engineering. For the cell biology component of tissue engineering, the greatest challenge is to optimize the isolation, proliferation and differentiation of cells and to design scaffolds or delivery systems that yield tissue growth in three dimensions. Ideally, we would harvest stem cells from a patient, expand them in cell culture, seed them on a scaffold and then implant the resultant tissue. Stem cells, when given the specific biological stimuli, can differentiate to become many types of specific mature cells, and use of these cells avoids the immunorejection that can occur with donor transplants. In addition, the technique of somatic nuclear transfer allows the creation of autologous cells and tissues from allogeneic embryonic stem cells. It is then important for the scaffold to act as a template and stimulus for proliferation and differentiation of the stem cells into the mature cells that will generate specific new tissue. The tissue can be grown on a scaffold that will resorb, so that only the new tissue will be implanted, or a 'biocomposite' of the scaffold and new tissue can be implanted. After implantation, the tissue-engineered construct must be able to survive, restore normal function and integrate with the surrounding tissues.

再論複製人——一個比較倫理的分析

再論複製人——一個比較倫理的分析