Tiziano Barberi

Neural subtype specification of fertilization and nuclear transfer embryonic stem cells and application in parkinsonian mice

Existing protocols for the neural differentiation of mouse embryonic stem (ES) cells require extended in vitro culture, yield variable differentiation results or are limited to the generation of selected neural subtypes. Here we provide a set of coculture conditions that allows rapid and efficient derivation of most central nervous system phenotypes. The fate of both fertilization- and nuclear transfer–derived ES (ntES) cells was directed selectively into neural stem cells, astrocytes, oligodendrocytes or neurons. Specific differentiation into γ-aminobutyric acid (GABA), dopamine, serotonin or motor neurons was achieved by defining conditions to induce forebrain, midbrain, hindbrain and spinal cord identity. Neuronal function of ES cell–derived dopaminergic neurons was shown in vitro by electron microscopy, measurement of neurotransmitter release and intracellular recording. Furthermore, transplantation of ES and ntES cell–derived dopaminergic neurons corrected the phenotype of a mouse model of Parkinson disease, demonstrating an in vivo application of therapeutic cloning in neural disease.

Isolation and directed differentiation of neural crest stem cells derived from human embryonic stem cells

Vertebrate neural crest development depends on pluripotent, migratory precursor cells. Although avian and murine neural crest stem (NCS) cells have been identified, the isolation of human NCS cells has remained elusive. Here we report the derivation of NCS cells from human embryonic stem cells at the neural rosette stage. We show that NCS cells plated at clonal density give rise to multiple neural crest lineages. The human NCS cells can be propagated in vitro and directed toward peripheral nervous system lineages (peripheral neurons, Schwann cells) and mesenchymal lineages (smooth muscle, adipogenic, osteogenic and chondrogenic cells). Transplantation of human NCS cells into the developing chick embryo and adult mouse hosts demonstrates survival, migration and differentiation compatible with neural crest identity. The availability of unlimited numbers of human NCS cells offers new opportunities for studies of neural crest development and for efforts to model and treat neural crest–related disorders.

Derivation of engraftable skeletal myoblasts from human embryonic stem cells

Human embryonic stem cells (hESCs) are a promising source for cell therapy in degenerative diseases. A key step in establishing the medical potential of hESCs is the development of techniques for the conversion of hESCs into tissue-restricted precursors suitable for transplantation. We recently described the derivation of multipotent mesenchymal precursors from hESCs. Nevertheless, our previous study was limited by the requirement for mouse feeders and the lack of in vivo data. Here we report a stroma-free induction system for deriving mesenchymal precursors. Selective culture conditions and fluorescence-activated cell sorting (FACS)-mediated purification yielded multipotent mesenchymal precursors and skeletal myoblasts. Skeletal muscle cells undergo in vitro maturation resulting in myotube formation and spontaneous twitching. We found that hESC-derived skeletal myoblasts were viable after transplantation into the tibialis anterior muscle of SCID/Beige mice, as assessed by bioluminescence imaging. Lack of teratoma formation and evidence of long-term myoblast engraftment suggests considerable potential for future therapeutic applications.

Differentiation of Multipotent Mesenchymal Precursors and Skeletal Myoblasts from Human Embryonic Stem Cells

This unit describes a protocol for the derivation of multipotent mesenchymal precursors from human embryonic stem cells (hESCs). hESCs cultured at low density in the presence of a chemically defined serum-free medium are induced to adopt an endomesodermal fate and later a mesenchymal phenotype. FACS sorting for the surface antigen CD73 is used to purify mesenchymal precursors able to differentiate into fat, bone, cartilage, and skeletal muscle cells. Enrichment in mesenchymal precursors with a myogenic potential is achieved via an additional FACS sorting for the embryonic skeletal muscle surface marker N-CAM.

Wnt1 Overexpression Leads to Enforced Cardiomyogenesis and Inhibition of Hematopoiesis in Murine Embryonic Stem Cells

Recent findings emphasized a critical role for the Wnt signaling pathway during the early steps of embryogenesis, including the development of the hematopoietic system and cardiac development. To date, the role of Wnt in promoting or inhibiting development of both tissues was discussed controversially, dependent on species and time point of expression. Differentiation of embryonic stem cells (ESC) recapitulates early stages of mammalian development. In the present study, we generated murine ESC lines overexpressing Wnt1 (Wnt1 ES). When induced to differentiate toward the cardiomyocytic lineage, Wnt1 ES showed a significant increased ability to generate cardiomyocytes when compared with a control ESC (control ES) line. In addition, Wnt1 ES cells were unable to form hematopoietic cells, whereas development of endothelial cells, a cell type closely associated with blood during embryogenesis, was comparable to control ES. Finally, cardiac differentiation was markedly decreased by the addition of the Wnt antagonist Dkk-1 to the culture medium. These findings suggest that Wnt1 may regulate differentiation of immature mesodermal cells in a tissue-specific manner.