Endogenous precursor cells

Craig, C.G., Tropepe, V., Morshead, C.M., Reynolds, B.A., Weiss, S., van der Kooy, D. (1996). In vivo growth factor expansion of endogenous subependymal neural precursor cell populations in the adult mouse brain. JNeurosci, 16, 2649-58. 

Whether this is a direct effect of IGF-1 on the proliferation of the neuronal precursor cells, or whether the IGF-1 is acting principally as a survival agent and there are endogenous proliferative factors in these cultures, as we have observed in cultures of neuroepithelial cells (Drago et al.,... 

K. Toriyama, et al.. Endogenous adipocyte precursor cells for regenerative soft-tissue engineering, Tissue Eng. 8 (2002) 157-165. 

An alternative to cell delivery per se is to attract endogenous stem cells and precursor cells to the defect site for de novo tissue regeneration. Hepatocyte growth factor (HGF) induces migration of MSCs in vitro but is rapidly degraded by proteolysis in vivo. Extended, localized delivery of HGF was achieved with Heprasil sECM hydrogels, and the sECM composition could be optimized for controlled release of HGF that resulted in recruitment of human bone marrow MSCs into the scaffold in vitro (Zhao et al, 2008). 

Endogenous small molecules such as phosphoserine and ATRA were also found to promote neural differentiation. Although ATRA has been shown to promote neurogenesis in vivo it shows relatively low levels of efficiency in vitro, and is also unstable upon irradiation. In an attempt to circumvent this problem, Christie et al. prepared stable ATRA mimics based on biaryl acetylenes. Intriguingly, /jara-substituted 4a was observed to give rise to a neural phenotype in vitro, but the corresponding meta-isomer 4b was observed to give primarily epithelial phenotype upon treatment of the same precursor cells. 

Together with dopamine, adrenaline and noradrenaline belong to the endogenous catecholamines that are synthesized from the precursor amino acid tyrosine (Fig. 1). In the first biosynthetic step, tyrosine hydroxylase generates l-DOPA which is further converted to dopamine by the aromatic L-amino acid decarboxylase ( Dopa decarboxylase). Dopamine is transported from the cytosol into synaptic vesicles by a vesicular monoamine transporter. In sympathetic nerves, vesicular dopamine (3-hydroxylase generates the neurotransmitter noradrenaline. In chromaffin cells of the adrenal medulla, approximately 80% of the noradrenaline is further converted into adrenaline by the enzyme phenylethanolamine-A-methyltransferase. 

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