Human embryonic stem cells (hESC) hold great promise for the treatment of patients with many neurodegenerative diseases particularly those arising from cell loss or neural dysfunction including spinal cord injury. This study evaluates the therapeutic effects of transplanted hESC-derived oligodendrocyte progenitors (OPC) and/or motoneuron progenitors (MP) on axonal remyelination and functional recovery of adult rats after complete spinal cord transection. OPC and/or MP were grafted into the site of injury in the acute phase. Based on Basso-Beattie-Bresnahan scores recovery of locomotor function was significantly enhanced in rats treated with OPC and/or MP when compared with control animals. When transplanted into the spinal cord immediately after complete transection, OPC and MP survived, migrated, and differentiated into mature oligodendrocytes and neurons showing in vivo electrophysiological activity. Taken together, these results indicate that OPC and MP derived from hESC could be a useful therapeutic strategy to repair injured spinal cord. Stem Cells 2010; 28:1541–1549.

The cerebellum has critical roles in motor and sensory learning and motor coordination. Many cerebellumrelated disorders indicate cell therapy as a possible treatment of neural loss. Here we show that application of inductive signals involved in early patterning of the cerebellar region followed by application of different factors directs human embryonic stem cell differentiation into cerebellar-like cells such as granule neurons, Purkinje cells, interneuron, and glial cells. Neurons derived using our protocol showed a T-shaped polarity phenotype and express similar markers to the developed human cerebellum. Electrophysiological measurements confirmed functional electrical properties compatible with these cells. In vivo implantation of differentiated human embryonic stem cells transfected with MATH1-GFP construct into neonatal mice resulted in cell migration across the molecular and the Purkinje cell layers and settlement in the internal molecular layers. Our findings demonstrate that the universal mechanisms involved in the development of cerebellum can be efficiently recapitulated in vitro, which enables the design of new strategies for cell replacement therapy, to study early human development and pathogenesis of neurodegenerative diseases.

Reprogramming of human somatic cells by transcription factors to pluripotent state holds great promise for regenerative medicine. However, low efficiencies of current reprogramming methods, immunogenicity and lack of understanding regarding the molecular mechanisms responsible for their generation, limits their utilization and raises questions regarding safety for therapeutic application. Here we report that ACA signaling via PI3K/Akt/mTor induces sustained de-differentiation of human blood progenitor cells leading to generation of ACA pluripotent stem cells. Blood-derived pluripotent stem cells differentiate in vitro into cell types of all three germ layers, exhibiting neuronal, liver, or endothelial characteristics. Our results reveal insight into the molecular events regulating cellular reprogramming and also indicate that pluripotency might be controlled in vivo through binding of a natural ligand(s) to ACA receptor enabling reprogramming through defined pathway(s) and providing a safe and efficient method for generation of pluripotent stem cells which could be a breakthrough in human therapeutics.

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