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Natural cartilage remodels both in vivo and in vitro in response to mechanical stresses, hence mechanical stimulation is believed to be a potential tool to modulate extra-cellular matrix synthesis in tissue-engineered cartilage. Fluid-induced shear is known to enhance chondrogenesis in engineered cartilage constructs. The quantification of the hydrodynamic environment is a condition required to study the biochemical response to shear of 3D engineered cell systems. We developed a computational model of culture medium flow through the microstructure of a porous scaffold, during direct- perfused culture. The 3D solid model of the scaffold micro-geometry was reconstructed from 250 micro-computed tomography (micro-CT) images. The results of the fluid dynamic simulations were analyzed at the central portions of the fluid domain, to avoid boundary effects. The average, median and mode shear stress values calculated at the scaffold walls were 3.48, 2.90, and 2.45 mPa respectively, at a flow rate of 0.5 cm(3)/min, perfused through a 15 mm diameter scaffold, at an inlet fluid velocity of 53 microm/s. These results were compared to results estimated using a simplified micro-scale model and to results estimated using an analytical macro-scale porous model. The predictions given by the CT-based model are being used in conjunction with an experimental bioreactor model, in order to quantify the effects of fluid-dynamic shear on the growth modulation of tissue-engineered cartilage constructs, to potentially enhance tissue growth in vitro., (Copyright 2005 Wiley Periodicals, Inc.)

Background: Although experimental studies have demonstrated an important role of insulin-like growth factor I (IGF-I) in hepatocarcinogenesis, the clinical data about IGF-I in patients with hepatocellular carcinoma (HCC) are scarce and controversial. To the authors' knowledge, this is the first prospective study investigating the longitudinal correlation between modifications in serum IGF-I levels and the development of HCC in a cohort of patients with hepatitis C virus (HCV)-related cirrhosis., Methods: One hundred fourteen consecutive patients with HCV-related Child Grade A cirrhosis were followed prospectively at the Second University of Naples for 56.4 +/- 12.0 months with ultrasound examinations of the liver and serum alpha-fetoprotein determination every 6 months. At each clinical evaluation, the severity of disease was graded according to the established Child-Pugh scoring system. Serum IGF-I levels were measured prospectively at the study entry and at least every 12 months throughout follow-up., Results: Twenty patients (19.2%) developed HCC during follow-up. Eleven of these patients had persistent Child Grade A cirrhosis for the whole study, whereas the other 9 patients developed HCC after their cirrhosis progressed from Child Grade A to Grade B. In patients who remained free of HCC for the whole study, serum IGF-I concentrations did not modify significantly during follow-up. Conversely, in patients who developed HCC, IGF-I levels decreased significantly during follow-up (from 72.6 +/- 29.9 microg/L to 33.8 +/- 14.5 microg/L; P = 0.001). In these patients, the significant decrease occurred both in patients with persistent Child Grade A cirrhosis and in patients with cirrhosis that progressed from Child Grade A to Grade B. The reduction in IGF-I level preceded the diagnosis of HCC by 9.3 +/- 3.1 months., Conclusions: This prospective study demonstrates that, in patients with HCV-related cirrhosis, 1) the development of HCC is accompanied by a significant reduction of serum IGF-I levels independent of the grade of impairment of liver function; and 2) modification of the IGF-I level precedes the morphologic appearance of HCC, permitting a precocious diagnosis of the tumor., (Copyright 2002 American Cancer Society.DOI 10.1002/cncr.11002)