While such grafts have led to striking temporary improvements in the major motion disorder symptoms in many patients, results have been limited, and significant improvements in the protocol are clearly required to realize the potential of cell therapy to help these patients. The grafts are significantly immunogenic, leading to rejection in some cases and necessitating immunosuppression in most patients. The nature of the cell source means that very few patients could ever hope to benefit from treatment, since the supply of fetal midbrain tissue is both inherently limited and subject to politically-imposed restrictions. And the actual benefits to patients have not been as robust as might have been hoped: the magnitude of clinical response has been highly variable, gains have proven impermanent, and ~15% of transplanted patients have developed substantial dyskinesias during the "off" phase of levodopa treatment.
Many of these limitations are attributable to the crude cell sources used in these trials. An important step forward will be to move beyond the use of fetal mesencephalic tissue, and instead derive graft populations of pure DA neurons from pluripotent stem cells, such as embryonic stem cells (ESC), induced pluripotent stem cells (iPS), or somatic cell nuclear transfer (SCNT — "therapeutic cloning")
A Superior Protocol (for better cells for rejuvenation therapies)
The authors had previously reported a protocol for deriving mesencephalic DA neurons by nudging them through an intermediary stage as midbrain floor plate precursor cells. The floor plate is the developmental topos through which cells are thought to acquire DA neural progenitor characteristics. This entailed a dual inhibition of SMAD signalling in the cells through the simultaneous inhibition of BMP4 using Noggin (an inhibitor of BMP4), and activation of the Lefty/Activin/TGFβ pathway with the drug SB431542, and the approach has subsequently been independently validated by investigators at the MRC Centre for Regenerative Medicine. As part of this new report, two lines each of human ESC and iPS cells were used to derive DA neurons using either a modified version of this new strategy, or the currently-standard protocol of moving such cells through a neural rosette intermediate for DA neuron derivation. The dual SMAD inhibition, floor-plate-intermediate protocol proved superior, generating a higher percentage of tyrosine hydroxylase-expressing (TH+) neurons, which unlike rosette-derived cells expressed markers of the developing mesencephalon and (importantly) led to far lower adventitious generation of serotonergic neurons.
Human pluripotent stem cell lines are mainly derived from inner cell mass of blastocysts and primordial germ cells of embryos, which are the cell lines cultivated by the way of inhibited differentiation in vitro and characterized by infinite proliferation potentiality and development totipotency. Research of human pluripotent stem cell is becoming the hottest, most active and front-line subject in field of life science. Doing further research on human pluripotent stem cells is of important significance, which mainly shows: firstly, as the ideal model of developmental biology, it can understand precisely incipient development mechanism and related controlling factors. Secondly, human pluripotent stem cell is characterized by infinite proliferation potentiality and development multipotency, and therefore it provides infinite seed cell working as the basic model for cell, tissue and organ transplantation research. Thirdly, the genetic manipulation feasibility of human pluripotent stem cell makes it the carrier model of genetic and cellular therAKPy. In reality, scientists across the world are fastening the research of human pluripotent stem cell by aid of enormous investment and other channels, for it is obvious who can gain research achievement first will get the leader possition of the life science development of 21th century, and do great contribution to improving the social economy and people’ health. It is of great urgency for all researchers around the globe to set up human pluripotent stem cell line or human pluripotent stem cell bank. By far, research of human pluripotent stem cell is mainly on human ES cell lines which originated from inner cell mass of blastocysts, and the usual feeder layer for cultivating human pluripotent stem cell is murine embryonic fibroblasts. There is only one successful research case of human EG cell lines set up across the world. However, there is no report about successful setting-up of hEGCs in China. So,it is still spacious to research the human embryonic germ cells originated from PGCs. In order to recognize further human EG cells, we have researches as followed: (1) further research the germination, migration and surface marker of human embryonic germ cells which are the origin of human EG cells. (2) using cryobiological technology to freeze, thaw 6-8week primordial germ cells, and prove feasibility of reserving human embryonic primordial germ cells under low temperature. (3) using 3-5m human embryonic lung as material to isolate, purify, cultivate and identify human embryonic lung fibroblasts, choose the best time and density of mitomycin C to inactivate the feeder layer. (4) using human embryonic lung fibroblasts divided and cultivated by ourselves as the feeder layer to isolate and cultivate human embryonic germ cells and identify. (5) comparing influence on growth of human EG cells by STO and human embryonic lung fibroblasts respectively as feeder layers. (6) Finally, using soluble cytokines as the inducer to make human EG cells differentiate committed to hematopoietic cells. 1. The origin, migration and phenotype of human embryonic primordial germ cells:The aim of this research is to lay the basis for recognization of human PGCs biological characteristics and gaining of human embryonic germ cells derived from human primordial germ cells. Collect 4.5 to 12 week postfertilazation human embryos, slice the gonadal ridges, stain with HE and observe with light microscope. Then the slices of gonadal ridges are analyzed for the expression of alkaline phosphatase and immunologic markers (SSEA-1,SSEA-4) that have been used to routinely to characterize embryonic germ cells. Lastly , detect the expression of transcriptional factor Oct-4 by RT-PCR. Experiment results show that there is no PGC migrated to gonad ridgres before 5 w, up to 5-11 weeks, PGCs gradually migrate to gonad ridges and proliferate. During the period, genital ridges consists of AKP positive cells which express SSEA-1 and SSEA-4 and express transcription factor Oct-4. 12 weeks later, there are still AKP positiv
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