Browsing by Subject "extracellular matrix"
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(2012)Human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) have two unique properties: the self-renewal capacity and the broad developmental potential. They both have their advantages and disadvantages, but the current perception is that hESCs and hiPSCs complement rather than replace each other. New scientific problems and ethical challenges will arise because stem cell research is developing rapidly. The potential of hiPSC and hESC technologies in drug discovery is tremendous. The human pluripotent stem cell (hPSC)-derived cells have a potential to replace a part of the current preclinical toxicity and efficacy screening tests and to prevent misrouted drug development and use for lead optimization at phases before clinical trials. The hPSC-based disease models can also narrow the gap between traditional animal models and clinical trials. One major challenge is the differentiation process of hPSCs into cells of the relevant tissue. The recent study of our laboratory shows that the liver cell-deried acellular matrix (ACM) promotes the hepatic commitment of hESCs. To create chemically defined, xeno-free and feeder-free culture matrices for the differentiation of the hESCs into hepatocyte-like cells (HLCs), the ECM components of the ACM were characterized. The results suggest that the ACM contains fibronectin, laminins. After the characterization, the object was to identify which of the ECM proteins are essential and effective in the differentiation. A three-step differentiation protocol with differenent ECM protein solutions was used to produce HLCs. The hESCs were first induced into definitive endoderm (DE) cells. The DE cells were committed to the bipotential hepatic progenitors positive for HNF4α and AFP. Finally the progenitors were differentiated into HLCs. The mRNA expression of albumin, CK8, CK18, AAT, and BCRP was increased in HLCs. All the derived HLCs were albumin positive. The hESCderived HLCs showed hepatic morphology, cytoplasmic vacuole characteristics, and functional albumin secretion. The chemically defined matrices showed a supportive role in the differentiation of the hESCs into HLCs. This study establishes an efficient, chemically defined, xeno-free system to produce HLCs as a cell source for pharmaceutical and developmental studies.
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(2013)Laminins are a family of heterotrimeric glycoproteins found mainly in basement membranes. They interact with numerous other extracellular matrix components and cell surface receptors, including integrins and α-dystroglycan. Laminins play roles in myriad of functions including tissue morphogenesis, organogenesis, maintenance of tissue integrity and compartmentalization. In central nervous system laminins are involved in every major developmental stage from neural tube closure to synaptogenesis. Laminin expression in central nervous system decreases after maturation but has been found inducible by injury after trauma or disease. Since laminins are known to promote neurite outgrowth and neuronal survival, this has been proposed as a regenerative response to injury. Although the effects of endogenous laminin are clearly inadequate for repair, laminin based compounds could be powerful therapeutic agents. In previous in vivo studies KDI-tripeptide, a neurite outgrowth promoting fragment from γ1-laminin, has proved effective neuroprotective and regeneration promoting compound. Encouraged by these results I set out to test whether KDI would rescue midbrain dopaminergic neurons in unilateral 6-hydroxydopamine-induced rat model of Parkinson's disease. KDI (1-30µg) was injected to the striatum six hours prior to 6-hydroxydopamine. The severity of the lesion was then evaluated by measuring D-amphetamine induced rotation 2, 4 and 6 weeks postlesion and by assessing the number of neurons in substantia nigra pars compacta and optical density of striatum after tyrosine hydroxylase immunostaining at week seven. The only effective KDI dose studied was 3 µg. Compared to control it decreased Damphetamine induced rotational behaviour significantly at week four. KDI, however, failed to save tyrosine hydroxylase positive dopaminergic neurons in substantia nigra pars compacta or their axons in striatum. KDI might be usable in treating Parkinson's disease but it's mode of action doesn't appear to rely on protecting dopaminergic neurons or promoting the branching of their axons. KDI is known to inhibit ionotropic glutamate receptors and could therefore improve motor function by opposing striatal denervation induced overactivity of glutamatergic subthalamic nucleus neurons.
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