Characterization and comparison of osteoblasts derived from mouse embryonic stem cells and induced pluripotent stem cells.

New developments in stem cell biology offer alternatives for the reconstruction of critical-sized bone defects. One of these developments is the use of induced pluripotent stem (iPS) cells. These stem cells are similar to embryonic stem (ES) cells, but can be generated from adult somatic cells and therefore do not raise ethical concerns. Proper characterization of iPS-derived osteoblasts is important for future development of safe clinical applications of these cells. For this reason, we differentiated mouse ES and iPS cells toward osteoblasts using osteogenic medium and compared their functionality. Immunocytochemical analysis showed significant expression of bone markers (osteocalcin and collagen type I) in osteoblasts differentiated from ES and iPS cells on days 7 and 30. An in vitro mineralization assay confirmed the functionality of osteogenically differentiated ES and iPS cells. Gene expression arrays focusing on osteogenic differentiation were performed in order to compare the gene expression pattern in both differentiated and undifferentiated ES cells and iPS cells. We observed a significant upregulation of osteogenesis-related genes such as Runx2, osteopontin, collagen type I, Tnfsf11, Csf1, and alkaline phosphatase upon osteogenic differentiation of the ES and iPS cells. We further validated the expression of key osteogenic genes Runx2, osteopontin, osteocalcin, collagen type I, and osterix in both differentiated and undifferentiated ES and iPS cells by means of quantified real-time polymerase chain reaction. We conclude that ES and iPS cells are similar in their osteogenic differentiation capacities, as well as in their gene expression patterns.

PET imaging of glucose metabolism, neuroinflammation and demyelination in the lysolecithin rat model for multiple sclerosis.

BACKGROUND: Injection of lysolecithin in the central nervous system results in demyelination accompanied by local activation of microglia and recruitment of monocytes. Positron-emission tomography (PET) imaging, using specific tracers, may be an adequate technique to monitor these events in vivo and therefore may become a tool for monitoring disease progression in multiple sclerosis (MS) patients. OBJECTIVES: The objective of this paper is to evaluate the potential of PET imaging in monitoring local lesions, using [(11)C]MeDAS, [(11)C]PK11195 and [(18)F]FDG as PET tracers for myelin density, microglia activation and glucose metabolism, respectively. METHODS: Sprague-Dawley rats were stereotactically injected with either 1% lysolecithin or saline in the corpus callosum and striatum of the right brain hemisphere. PET imaging was performed three days, one week and four weeks after injection. Animals were terminated after PET imaging and the brains were explanted for (immuno)histochemical analysis. RESULTS: PET imaging was able to detect local demyelination induced by lysolecithin in the corpus callosum and striatum with [(11)C]MeDAS and concomitant microglia activation and monocyte recruitment with [(11)C]PK11195. [(18)F]FDG imaging demonstrated that glucose metabolism was maintained in the demyelinated lesions. CONCLUSION: PET imaging with multiple tracers allows simultaneous in vivo monitoring of myelin density, neuroinflammation and brain metabolism in small MS-like lesions, indicating its potential to monitor disease progression in MS patients.

PET imaging of disease progression and treatment effects in the experimental autoimmune encephalomyelitis rat model.

UNLABELLED: The experimental autoimmune encephalomyelitis model is a model of multiple sclerosis that closely mimics the disease characteristics in humans. The main hallmarks of multiple sclerosis are neuroinflammation (microglia activation, monocyte invasion, and T-cell infiltration) and demyelination. PET imaging may be a useful noninvasive technique for monitoring disease progression and drug treatment efficacy in vivo. METHODS: Experimental autoimmune encephalomyelitis was induced by myelin-oligodendrocyte glycoprotein immunization in female Dark Agouti rats. Experimental autoimmune encephalomyelitis rats were imaged at baseline and at days 6, 11, 15, and 19 after immunization to monitor monocyte and microglia activation ((11)C-PK11195) and demyelination ((11)C-MeDAS) during normal disease progression and during treatment with dexamethasone. RESULTS: (11)C-PK11195 PET detected activation of microglia and monocytes in the brain stem and spinal cord during disease progression. The uptake of (11)C-PK11195 was elevated in dexamethasone-treated animals that had shown mild clinical symptoms that had resolved at the time of imaging. Demyelination was not detected by (11)C-MeDAS PET, probably because of the small size of the lesions (average, 0.13 mm). CONCLUSION: PET imaging of neuroinflammation can be used to monitor disease progression and the consequences of treatment in the experimental autoimmune encephalomyelitis rat model. PET imaging was more sensitive than clinical symptoms for detecting inflammatory changes in the central nervous system.

Catecholamine-synthesizing enzymes in carcinoid tumors and pheochromocytomas.

BACKGROUND: Serotonin is the principal endocrine product of carcinoid tumors, but simultaneously increased production of catecholamines has been described in these tumors. As it is not clear whether these tumors contain specific enzymes for catecholamine synthesis, we aimed to detect catecholamine-synthesizing enzymes [tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT)] in midgut carcinoid tumors and pheochromocytoma and to correlate enzyme expression to serotonin production as well as catecholamines and metabolites excreted in urine. METHODS: Paraffin-embedded tumor specimens from 21 midgut carcinoid patients and 20 pheochromocytoma patients (10 sporadic and 10 MEN type IIa-related tumors) were stained for TH, DBH, and PNMT, using a three-step biotin-avidin-peroxidase method. RESULTS: TH was demonstrated in 9 (43%) of 21 carcinoids and in all (100%) of 20 pheochromocytomas, DBH in 8 (38%) carcinoids and in 15 (75%) pheochromocytomas, and PNMT in 7 (33%) carcinoids and in 13 (65%) pheochromocytomas. Increased urinary excretion of catecholamines and metabolites was observed in 10 (48%) carcinoid patients and in all pheochromocytoma patients. No clinically relevant association between enzyme expression and urinary excretion of catecholamines and metabolites was found. CONCLUSIONS: Catecholamine-synthesizing enzymes are present in many carcinoid tumors. This finding possibly indicates the existence of a catecholamine-synthesizing pathway in carcinoids similar to that found in pheochromocytoma.