SU-E-T-179: MVCB Pelvic Surface Dosimetry.

PURPOSE: To compare commonly clinically available methods of estimating skin dose for a Megavoltage Conebeam CT of the pelvis. METHODS: The clinical 6 MV conebeam uses 15 MU on a Siemens Oncor linac. Film tests using XV-2 film were done on a solid water phantom, as were tests using a parallel plate ion chamber at 2 mm depth. A Rando pelvic phantom was set up for a MVCB CT, and a cylindrically symmetric Isorad 6-12 MV PDM diode was placed at various angles around the phantom and irradiated using a 150 MU 6 MV arc beam with the same geometry as the clinical conebeam, giving higher and more accurate readings than would be obtained with the 15 MU conebeam. A comparison was made with the Pinnacle 8.0m treatment planning system. A strip of Optically Stimulated Luminescence dosimeters provides an accurate check of the surface dose distribution. RESULTS: All methods revealed an expected lateral asymmetry in the dose due to the starting and stopping angles of 270 (-90) and 110 for the conebeam. On the sides of the phantom, the diode dose was comparable to the Pinnacle-calculated dose at a depth of 3-5 mm. Near the anterior portion the diode dose was about 5% higher than the maximum Pinnacle-calculated dose at that angle. This difference is partly due to the increased diode response at shorter SSDs and higher dose rates, and to the geometry with the arc beam radiation being mainly anterior to posterior. The skin dose, corresponding to a depth of about 2 mm, is expected to be somewhat lower. CONCLUSIONS: To estimate pelvic skin dose in the MV CB geometry, corrections for measurement depth and geometry can be used to improve the dosimetry for these common clinically available dosimeters.

Efficient animal-serum free 3D cultivation method for adult human neural crest-derived stem cell therapeutics.

Due to their broad differentiation potential and their persistence into adulthood, human neural crest-derived stem cells (NCSCs) harbour great potential for autologous cellular therapies, which include the treatment of neurodegenerative diseases and replacement of complex tissues containing various cell types, as in the case of musculoskeletal injuries. The use of serum-free approaches often results in insufficient proliferation of stem cells and foetal calf serum implicates the use of xenogenic medium components. Thus, there is much need for alternative cultivation strategies. In this study we describe for the first time a novel, human blood plasma based semi-solid medium for cultivation of human NCSCs. We cultivated human neural crest-derived inferior turbinate stem cells (ITSCs) within a blood plasma matrix, where they revealed higher proliferation rates compared to a standard serum-free approach. Three-dimensionality of the matrix was investigated using helium ion microscopy. ITSCs grew within the matrix as revealed by laser scanning microscopy. Genetic stability and maintenance of stemness characteristics were assured in 3D cultivated ITSCs, as demonstrated by unchanged expression profile and the capability for self-renewal. ITSCs pre-cultivated in the 3D matrix differentiated efficiently into ectodermal and mesodermal cell types, particularly including osteogenic cell types. Furthermore, ITSCs cultivated as described here could be easily infected with lentiviruses directly in substrate for potential tracing or gene therapeutic approaches. Taken together, the use of human blood plasma as an additive for a completely defined medium points towards a personalisable and autologous cultivation of human neural crest-derived stem cells under clinical grade conditions.

Angiopoietin-1 and its receptor Tie-2 participate in the regulation of capillary-like tubule formation and survival of endothelial cells.

Angiopoietin-1 (Ang-1) and its receptor Tie-2, a trans-membrane tyrosine kinase uniquely expressed by endothelial cells, are shown by null mutation studies to be essential to developmental angiogenesis. The phenotypic abnormalities in these knockout animals suggest that Tie-2 signaling is necessary for the maintenance and expansion of the primitive capillary network. We present in vitro evidence indicating that the Ang-1/Tie-2 system participates in the regulation of capillary tubule formation and is necessary for the survival of confluent endothelial cells. Although recombinant Ang-1, which induces Tie-2 phosphorylation, has no effect on the proliferation of endothelial cells, treatment of confluent adult bovine aortic endothelial cells (ABAE) cells grown on collagen gels with Ang-1 (100 ng/ml) causes the cells to migrate into the collagen gel and form capillary-like tubules. The tubule-forming effect of Ang-1 is similar to the effect caused by FGF-2. A soluble form of the Tie-2 extracellular domain, in fivefold molar excess, blocks Ang-1-induced tubule formation. Specific elimination of Tie-2 protein expression in cultured ABAE cells as a result of transfection with an antisense oligonucleotide causes cell death in a dose-dependent manner (IC(50) = 50 nM). The antisense treatment has no effect on cells that do not express Tie-2. Cells treated with antisense oligonucleotide show a sixfold increase in the rate of apoptosis as assessed by in situ end labeling of fragmented DNA. These findings are consistent with the view that Ang-1/Tie-2 signaling is essential for both angiogenesis and endothelial cell survival.