Articular cartilage is made of chondrocytes surrounded by their extracellular matrix that can both sense and respond to various mechanical stimuli. One of the most widely used in vitro model to study cartilage growth is the model of mesenchymal stromal cells-derived cartilage micropellet. However, mechanical stimulation of micropellets has never been reported probably because of their small size and imperfect round shape. The objective of the study was to develop an original custom-made device allowing both the mechanical stimulation and characterization of cartilage micropellets. The fluidic-based device was designed for the concomitant stimulation or characterization of six microspheres placed into the conical wells of a tank. In the present study, the device was validated using alginate-, collagen- and crosslinked collagen-based microspheres. Different types and ranges of pressure signals (square, sinusoidal and constant) were applied. The mechanical properties of microspheres were equivalent to those determined by a conventional compression test. Accuracy, repeatability and reproducibility of all types of pressure signals were demonstrated even though square signals were less accurate and sinusoidal signals were less reproducible than the others. The interest of this new device lies in the reliability to mechanically stimulate and characterize microspheres with diameters in the range of 900 to 1500 μm. Mechanical stimulation can be performed on six microspheres in parallel allowing the mechanical and molecular characterization of the same group of cartilage micropellets. The device will be useful to evaluate the growth of cartilage micropellets under mechanical stimuli.

关节软骨由被细胞外基质包围的软骨细胞组成，它们可以感知并响应各种机械刺激。研究软骨生长的最广泛使用的体外模型之一是间充质基质细胞衍生的软骨微丸的模型。然而，由于小颗粒的尺寸小和不完美的圆形，从未对小颗粒进行机械刺激。该研究的目的是开发一种原始的定制设备，该设备既可以机械刺激又可以表征软骨微丸。基于流体的设备设计用于伴随刺激或表征放置在储罐锥形井中的六个微球。在本研究中，使用藻酸盐，胶原蛋白和交联的胶原蛋白微球对设备进行了验证。应用了不同类型和范围的压力信号（平方，正弦和恒定）。微球的机械性能与通过常规压缩试验确定的那些相等。尽管正方形信号的准确性和重复性都较其他信号差，但所有类型的压力信号的准确性，可重复性和可再现性都得到了证明。这种新设备的兴趣在于机械刺激和表征直径在900至1500μm范围内的微球的可靠性。可以在六个微球上并行执行机械刺激，从而对同一组软骨微丸进行机械和分子表征。该装置可用于评估机械刺激下软骨微丸的生长。