Dynamic observation and quantification of type I/II collagen in chondrogenesis of mesenchymal stem cells by second-order susceptibility microscopy.

Second-order susceptibility (SOS) microscopy is used to image and characterize chondrogenesis in cultured human mesenchymal stem cells. SOS analysis shows that the SOS tensor ratios can be used to characterize type I and II collagens in living tissues and that both collagen types are produced at the onset of chondrogenesis. Time-lapse analysis shows a modulation of extracellular matrix results in a higher rate in increase of type II collagen, as compared to type I collagen. With time, type II collagen content stabilizes at the composition of 70% of total collagen content. SOS microscopy can be used to continuously and noninvasively monitor the production of collagens I and II. With additional development, this technique can be developed into an effective quality control tool for monitoring extracellular matrix production in engineered tissues.

Multiphoton dynamic imaging of the effect of chronic hepatic diseases on hepatobiliary metabolism in vivo.

In this study, intravital multiphoton microscopy was used to quantitatively investigate hepatobiliary metabolism in chronic pathologies of the liver. Specifically, through the use of the probe molecule 6-carboxyfluorescein diacetate, the effects of liver fibrosis, fatty liver, and hepatocellular carcinoma on the metabolic capabilities of mouse liver were investigated. After the acquisition of time-lapse images, a first order kinetic model was used to calculate rate constant resolved images of various pathologies. It was found that the ability of the liver to metabolically process the probe molecules varies among different pathologies, with liver fibrosis and fatty liver disease negatively impacted the uptake, processing, and excretion of molecules. The approach demonstrated in this work allows the study of the response of hepatic functions to different pathologies in real time and is useful for studying processes such as pharmacokinetics through direct optical imaging.

Expression of fibroblast growth factors in rat dorsal root ganglion neurons and regulation after peripheral nerve injury.

Using cDNA array, we observed the expression of eight members of the fibroblast growth factor (FGF) family, FGF 2, 5, 7, 9, 10, 13 and 14, in rat lumbar 4 and 5 dorsal root ganglia (DRGs). Over a period of 28 days after sciatic nerve transection, the array signals for FGF 2 and 7 were significantly increased in the DRGs, while FGF 13 decreased. Using the reverse transcription polymerase chain reaction (RT-PCR), we confirmed the axotomy-induced changes in the expression of FGF 7 and 13. hybridization showed that FGF 13 was expressed in 60% of DRG neurons under normal circumstance. Seven days after axotomy the number of FGF 13-positive neurons was decreased to 18%, but partially recovered to 40% after 28 days. FGF 13 immunoreactivity was also decreased. These data indicate that FGFs are important for DRG neurons under normal circumstance and after nerve injury.