Human iPS cell (iPSC)-derived cardiomyocytes (CMs) hold promise for drug discovery for heart diseases and cardiac toxicity tests. To utilize human iPSC-derived CMs, the establishment of three-dimensional (3D) heart tissues from iPSC-derived CMs and other heart cells, and a sensitive bioassay system to depict physiological heart function are anticipated. We have developed a heart-on-a-chip microdevice (HMD) as a novel system consisting of dynamic culture-based 3D cardiac microtissues derived from human iPSCs and microelectromechanical system (MEMS)-based microfluidic chips. The HMDs could visualize the kinetics of cardiac microtissue pulsations by monitoring particle displacement, which enabled us to quantify the physiological parameters, including fluidic output, pressure, and force. The HMDs demonstrated a strong correlation between particle displacement and the frequency of external electrical stimulation. The transition patterns were validated by a previously reported versatile video-based system to evaluate contractile function. The patterns are also consistent with oscillations of intracellular calcium ion concentration of CMs, which is a fundamental biological component of CM contraction. The HMDs showed a pharmacological response to isoproterenol, a β-adrenoceptor agonist, that resulted in a strong correlation between beating rate and particle displacement. Thus, we have validated the basic performance of HMDs as a resource for human iPSC-based pharmacological investigations.

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A Study of 12 Cases YASUAKI NAKASHIMA. MD,' TAKA0 YAMAMURO, MD,t YUZO FUJIWARA, MD,* YOSHlHlKO KOTOURA, MD,t EIGO MORI, M D ,~ AND YOSHIHIRO HAMASHIMA, M D I I Osteofibrous dysplasia (ossifying fibroma of long bones) is one of the fibro-osseous lesions that affects the tibia and fibula in the first decade of life. A study of 12 patients with this lesion showed the high rate of recurrence after surgical intervention. Most commonly, the lesions are eccentrically located in the diaphysis of the tibia. Pseudarthrosis may develop in cases where the lesion is situated in the distal portion. Roentgenologic and histopathologic features are basically similar to those of monostotic fibrous d ysplasia of long bones. However, bony or osteoid trabeculae covered by osteoblasts enable distinction between osteofibrous dysplasia and monostotic fibrous dysplasia, as determined histologically. The current evidence indicates that surgery should not be attempted in patients under 10 years of age.

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