Systematic and objective wet-lab testing of instruments for phacoemulsification: new Formalin Quadrant Model.

PURPOSE: To validate an improved wet-lab model for systematic and objective efficiency testing of instruments for phacoemulsification. SETTING: Institute of Medical Engineering, Lucerne University of Applied Sciences and Arts, Lucerne, Switzerland. DESIGN: Experimental study. METHODS: Porcine lenses were incubated for different time spans in formalin to simulate different cataract densities. Lenses were cut in quadrants and emulsified in a silicone test chamber. The use of ultrasound was restricted to full occlusion and the minimal power needed to promote emulsification. Equivalence to the surgical situation and cataract consistency were judged by an experienced surgeon. Efficiency was rated by effective phacoemulsification time, liquid consumption, and total surgery time. RESULTS: Formalin incubation times of 2 hours, 1.25 hours, and 0.5 hours were validated for hard, middle-hard, and soft cataracts, respectively. Systematic testing of different fluidics settings revealed the unique opportunities of the improved model: Experiments could be performed by laboratory staff without any surgical experience after a short training, and the model provided results in a fast and reproducible manner. Reduced effective phacoemulsification time, shorter total surgery time, and less liquid consumption were observed with higher fluidics settings, confirming and complementing earlier clinical findings. CONCLUSIONS: The Formalin Quadrant Model can be used to test new designs of instrumentation on different cataract densities or various instrument settings for efficiency. Using a validated cataract substitute, it closely represents the clinical situation and thus renders valid results in a short time. Instruments can be tested and improved profoundly before costly and elaborate clinical trials have to be applied.

Scalable Microgravity Simulator Used for Long-Term Musculoskeletal Cells and Tissue Engineering.

We introduce a new benchtop microgravity simulator (MGS) that is scalable and easy to use. Its working principle is similar to that of random positioning machines (RPM), commonly used in research laboratories and regarded as one of the gold standards for simulating microgravity. The improvement of the MGS concerns mainly the algorithms controlling the movements of the samples and the design that, for the first time, guarantees equal treatment of all the culture flasks undergoing simulated microgravity. Qualification and validation tests of the new device were conducted with human bone marrow stem cells (bMSC) and mouse skeletal muscle myoblasts (C2C12). bMSC were cultured for 4 days on the MGS and the RPM in parallel. In the presence of osteogenic medium, an overexpression of osteogenic markers was detected in the samples from both devices. Similarly, C2C12 cells were maintained for 4 days on the MGS and the rotating wall vessel (RWV) device, another widely used microgravity simulator. Significant downregulation of myogenesis markers was observed in gravitationally unloaded cells. Therefore, similar results can be obtained regardless of the used simulated microgravity devices, namely MGS, RPM, or RWV. The newly developed MGS device thus offers easy and reliable long-term cell culture possibilities under simulated microgravity conditions. Currently, upgrades are in progress to allow real-time monitoring of the culture media and liquids exchange while running. This is of particular interest for long-term cultivation, needed for tissue engineering applications. Tissue grown under real or simulated microgravity has specific features, such as growth in three-dimensions (3D). Growth in weightlessness conditions fosters mechanical, structural, and chemical interactions between cells and the extracellular matrix in any direction.

Influence of Mechanical Unloading on Articular Chondrocyte Dedifferentiation.

Due to the limited self-repair capacity of articular cartilage, the surgical restoration of defective cartilage remains a major clinical challenge. The cell-based approach, which is known as autologous chondrocyte transplantation (ACT), has limited success, presumably because the chondrocytes acquire a fibroblast-like phenotype in monolayer culture. This unwanted dedifferentiation process is typically addressed by using three-dimensional scaffolds, pellet culture, and/or the application of exogenous factors. Alternative mechanical unloading approaches are suggested to be beneficial in preserving the chondrocyte phenotype. In this study, we examined if the random positioning machine (RPM) could be used to expand chondrocytes in vitro such that they maintain their phenotype. Bovine chondrocytes were exposed to (a) eight days in static monolayer culture; (b) two days in static monolayer culture, followed by six days of RPM exposure; and, (c) eight days of RPM exposure. Furthermore, the experiment was also conducted with the application of 20 mM gadolinium, which is a nonspecific ion-channel blocker. The results revealed that the chondrocyte phenotype is preserved when chondrocytes go into suspension and aggregate to cell clusters. Exposure to RPM rotation alone does not preserve the chondrocyte phenotype. Interestingly, the gene expression (mRNA) of the mechanosensitive ion channel TRPV4 decreased with progressing dedifferentiation. In contrast, the gene expression (mRNA) of the mechanosensitive ion channel TRPC1 was reduced around fivefold to 10-fold in all of the conditions. The application of gadolinium had only a minor influence on the results. This and previous studies suggest that the chondrocyte phenotype is preserved if cells maintain a round morphology and that the ion channel TRPV4 could play a key role in the dedifferentiation process.