Objective-Human embryonic stem cells (hESCs) offer a sustainable source of endothelial cells for therapeutic vascularization and tissue engineering, but current techniques for generating these cells remain inefficient. We endeavored to induce and isolate functional endothelial cells from differentiating hESCs. Methods and Results-To enhance endothelial cell differentiation above a baseline of Ϸ2% in embryoid body (EB) spontaneous differentiation, 3 alternate culture conditions were compared. Vascular endothelial growth factor (VEGF) treatment of EBs showed the best induction, with markedly increased expression of endothelial cell proteins CD31, VE-Cadherin, and von Willebrand Factor, but not the hematopoietic cell marker CD45. CD31 expression peaked around days 10 to 14. Continuous VEGF treatment resulted in a 4-to 5-fold enrichment of CD31 ϩ cells but did not increase endothelial proliferation rates, suggesting a primary effect on differentiation. CD31 ϩ cells purified from differentiating EBs upregulated ICAM-1 and VCAM-1 in response to TNF␣, confirming their ability to function as endothelial cells. These cells also expressed multiple endothelial genes and formed lumenized vessels when seeded onto porous poly(2-hydroxyethyl methacrylate) scaffolds and implanted in vivo subcutaneously in athymic rats. Collagen gel constructs containing hESC-derived endothelial cells and implanted into infarcted nude rat hearts formed robust networks of patent vessels filled with host blood cells. A persisting challenge to the application of cell-based therapies is the sourcing of specific cells of interest. Because many mature tissues cannot be rebuilt using adult cells derived from biopsies, human embryonic stem cells (hESCs) could be instrumental in regenerative tissue engineering. Their immense proliferative and differentiation potential could provide extensive banks of cells-in quantity as well as type-for therapeutic applications. Conclusions-VEGFNatural and engineered tissues more than Ϸ200 m thick require suitable vascular support to survive and function properly. Although growth of host vessels into tissue engineering scaffolds has been achieved via controlled release of angiogenic molecules, this strategy requires many days to produce mature vessels. Further, host-derived vessel formation may be compromised by conditions that reduce angiogenesis such as diabetes and radiation therapy. 1 As angiogenesis is directed by a series of cytokines in a precise temporal sequence, adding 1 or even 2 cytokines may lead to incomplete blood vessel formation. Providing scaffolds with exogenous vascular cells before implantation may increase both the speed and extent of vascularization of engineered tissues. Before this approach can be successful, it will be critical to develop reliable methods to generate sufficient endothelial cells.Differentiation of hESCs in embryoid bodies treated with serum proceeds in a complex and largely uncontrolled manner. Methods to guide hESC differentiation into a specific lineage would therefore prov...

Common equipment in the dental operatory generate cumulative noise at sufficient decibel levels that can damage hearing. Although noise exposure in the dental office is typically intermittent, dentists and other dental care providers have been shown to be at risk of hearing loss. This article provides dentist-generated insight to use when incorporating hearing protection devices during dental practice. Four hearing protection devices (HPDs) were provided to 15 dentists in randomized sequence for evaluation. Perceptions were gathered via questionnaires and analyzed to determine mean ratings and product preferences. Battery requirements of electronic HPDs were also examined. Qualitative assessments of the HPDs evaluated are presented, including dentist preferences and recommendations. There were statistically significant differences (P ≤ 0.0031) among the HPDs in terms of ease of insertion, aesthetics, ability to hear while using a handpiece, and the openness of the ear. Battery life was not found to differ between the 2 electronic HPDs evaluated. Dentists most highly valued ease of hearing, ability to communicate, and comfort while wearing HPDs. The DI-15 High-Fidelity Electronic Earplugs HPD was ranked the highest, followed by Music PRO Electronic Earplugs. Battery longevity for these electronic HPDs was similar under all tested conditions studied. Knowledge Transfer Statement: Dentists should understand the potential ramifications of hearing loss and be aware that there are commercially available hearing protection products that preserve the ability to communicate with patients and coworkers.