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1.  Non-Neuronal Release of Gamma-Aminobutyric Acid by Embryonic Pluripotent Stem Cells 
Stem Cells and Development  2013;22(22):2944-2953.
γ-Aminobutyric acid (GABA), the principle inhibitory transmitter in the mature central nervous system, is also involved in activities outside the nervous system. Recent studies have shown that functional GABA receptors are expressed in embryonic stem (ES) cells and these receptors control ES cell proliferation. However, it is not clear whether ES cells have their own GABAergic transmission output machinery that can fulfill GABA release or whether the cells merely process the GABA receptors by receiving and responding to the diffused GABA released elsewhere. To get further insight into this unresolved problem, we detected the repertoire of components for GABA synthesis, storage, reaction, and termination in ES and embryonal carcinoma stem cells by biological assays, and then directly quantified released GABA in the intercellular milieu from these pluripotent stem (PS) cells by an analytical chemical assay based on high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). We found that embryonic PS cells processed a GABAergic circuit machinery and spontaneously released GABA, which suggests the potential that embryonic PS cells could autonomously establish a GABA niche via release of the transmitter.
doi:10.1089/scd.2013.0243
PMCID: PMC3822375  PMID: 23799822
2.  A Comparison of Epithelial Cells, Fibroblasts, and Osteoblasts in Dental Implant Titanium Topographies 
The major challenge for dental implants is achieving optimal esthetic appearance and a concept to fulfill this criterion is evaluated. The key to an esthetically pleasing appearance lies in the properly manage the soft tissue profile around dental implants. A novel implant restoration technique on the surface was proposed as a way to augment both soft- and hard-tissue profiles at potential implant sites. Different levels of roughness can be attained by sandblasting and acid etching, and a tetracalcium phosphate was used to supply the ions. In particular, the early stage attaching and repopulating abilities of bone cell osteoblasts (MC3T3-E1), fibroblasts (NIH 3T3), and epithelial cells (XB-2) were evaluated. The results showed that XB-2 cell adhesive qualities of a smooth surface were better than those of the roughened surfaces, the proliferative properties were reversed. The effects of roughness on the characteristics of 3T3 cells were opposite to the result for XB-2 cells. E1 proliferative ability did not differ with any statistical significance. These results suggest that a rougher surface which provided calcium and phosphate ions have the ability to enhance the proliferation of osteoblast and the inhibition of fibroblast growth that enhance implant success ratios.
doi:10.1155/2012/687291
PMCID: PMC3263600  PMID: 22287942
3.  Automated Measurement and Statistical Modeling of Elastic Laminae in Arteries 
Structural features of elastic laminae within arteries can provide vital information for both the mechanobiology and the biomechanics of the wall. In this paper, we propose, test, and illustrate a new computer-based scheme for automated analysis of regional distributions of elastic laminae thickness, inter-lamellar distances, and fragmentation (furcation points) from standard histological images. Our scheme eliminates potential artifacts produced by tissue cutting, automatically aligns tissue according to physiologic orientations, and performs cross-sectional measurements along radial directions. A statistical randomized complete block design (RCBD) and F-test were used to assess potential (non)-uniformity of lamellar thicknesses and separations along both radial and circumferential directions. Illustrative results for both normotensive and hypertensive thoracic porcine aorta revealed marked heterogeneity along the radial direction in nearly stress-free samples. Clearly, regional measurements can provide more detailed information about morphologic changes that cannot be gained by globally averaged evaluations alone. We also found that quantifying Furcation Point densities offers new information about potential elastin fragmentation, particularly in response to increased loading due to hypertension.
doi:10.1080/10255840903580033
PMCID: PMC2972381  PMID: 20221934
Vascular Elastin; Automated Histology; Quantitative Pathology; Discrete Radon Transform; Furcation Point Analysis; Randomized Complete Block Design; Hypertension; Marfan Syndrome; Aging
4.  Characterization of engineered tissue development under biaxial stretch using nonlinear optical microscopy 
Tissue engineering. Part A  2009;15(7):1553-1564.
Little is known about the precise mechanical stimuli that cells sense and respond to as they maintain or refashion the extracellular matrix in multiaxially loaded native or bioengineered tissues. Such information would benefit many areas of research involving soft tissues, including tissue morphogenesis, wound healing, and tissue engineering. A custom tissue culture device has been constructed that can impart well defined biaxial stretches on cruciform-shaped, fibroblast-seeded collagen gels and be mounted on the stage of a nonlinear optical microscopy (NLOM) system for microscopic characterization of matrix organization. The cruciform geometry permitted direct comparison of matrix (re-) organization within regions of the collagen gel exposed to either uniaxial or biaxial boundary conditions and examined by NLOM for up to six days. In addition, sequential NLOM measurements of collagen fiber orientations within gels while stretched, unloaded, or decellularized delineated contributions of applied stretches, cell-mediated tractions and matrix remodeling on the measured distributions. The integration of intravital NLOM with novel bioreactors enables visualization of dynamic tissue properties in culture.
doi:10.1089/ten.tea.2008.0287
PMCID: PMC2742218  PMID: 19063662
fibroblast-seeded collagen gel; tissue engineering; tissue anisotropy; second harmonic generation; multiphoton microscopy; biaxial mechanical load; collagen orientation distribution
5.  Characterization of Engineered Tissue Development Under Biaxial Stretch Using Nonlinear Optical Microscopy 
Tissue Engineering. Part A  2008;15(7):1553-1564.
Little is known about the precise mechanical stimuli that cells sense and respond to as they maintain or refashion the extracellular matrix in multiaxially loaded native or bioengineered tissues. Such information would benefit many areas of research involving soft tissues, including tissue morphogenesis, wound healing, and tissue engineering. A custom tissue culture device has been constructed that can impart well-defined biaxial stretches on cruciform-shaped, fibroblast-seeded collagen gels and be mounted on the stage of a nonlinear optical microscopy (NLOM) system for microscopic characterization of matrix organization. The cruciform geometry permitted direct comparison of matrix (re-)organization within regions of the collagen gel exposed to either uniaxial or biaxial boundary conditions and examination by NLOM for up to 6 days. In addition, sequential NLOM measurements of collagen fiber orientations within gels while stretched, unloaded, or decellularized delineated contributions of applied stretches, cell-mediated tractions, and matrix remodeling on the measured distributions. The integration of intravital NLOM with novel bioreactors enables visualization of dynamic tissue properties in culture.
doi:10.1089/ten.tea.2008.0287
PMCID: PMC2742218  PMID: 19063662
6.  A Microstructurally Motivated Model of the Mechanical Behavior of Tissue Engineered Blood Vessels 
Annals of biomedical engineering  2008;36(11):1782-1792.
Mechanical models have potential to guide the development and use of engineered blood vessels as well as other engineered tissues. This paper presents a microstructurally motivated, pseudoelastic, mechanical model of the biaxial mechanics of engineered vessels in the physiologic pressure range. The model incorporates experimentally measured densities and alignments of engineered collagen. Specifically, these microstructural and associated mechanical inputs were measured directly from engineered blood vessels that were cultured over periods of 5–7.5 weeks. To the best of our knowledge, this is the first successful application of either a phenomenological or a microstructurally motivated mechanical model to engineered vascular tissues. Model development revealed the need to use novel theoretical configurations to describe the strain history of engineered vessels. The constitutive equations developed herein suggested that collagen remodeled between 5 and 7.5 weeks during a 7.5-week culture period. This remodeling led to strain energies for collagen that differed with alignment, which likely resulted from undulations that varied with alignment. Finally, biaxial data emphasized that axial extensions increase stresses in engineered vessels in the physiologic pressure range, thereby providing a guideline for surgical use: engineered vessels should be implanted at appropriate axial extension to minimize adverse stress responses.
doi:10.1007/s10439-008-9554-4
PMCID: PMC2605792  PMID: 18720007
Tissue engineering; Blood vessels; Arteries; Mechanics; Model; Collagen; Microstructural influences

Results 1-6 (6)