Determination of hydroxyproline.

Age-associated increases in collagen cross-linking and accumulation of advanced glycosylation products are both accelerated by diabetes, suggesting that glucose-derived cross-link formation may contribute to the development of chronic diabetic complications as well as certain physical changes of aging. Aminoguanidine, a nucleophilic hydrazine compound, prevented both the formation of fluorescent advanced nonenzymatic glycosylation products and the formation of glucose-derived collagen cross-links in vitro. Aminoguanidine administration to rats was equally effective in preventing diabetes-induced formation of fluorescent advanced nonenzymatic glycosylation products and cross-linking of arterial wall connective tissue protein in vivo. The identification of aminoguanidine as an inhibitor of advanced nonenzymatic glycosylation product formation now makes possible precise experimental definition of the pathogenetic significance of this process and suggests a potential clinical role for aminoguanidine in the future treatment of chronic diabetic complications.

http://science.sciencemag.org/content/sci/232/4758/1629.full.pdf

Aminoguanidine prevents diabetes-induced arterial wall protein cross-linking

A simplified method for the analysis of hydroxyproline in biological tissues.

Transforming growth factor (TGF)-beta1 has been implicated in the pathogenesis of fibrosis based upon its matrix-inducing effects on stromal cells in vitro, and studies demonstrating increased expression of total TGF-beta1 in fibrotic tissues from a variety of organs. The precise role in vivo of this cytokine in both its latent and active forms, however, remains unclear. Using replication-deficient adenovirus vectors to transfer the cDNA of porcine TGF-beta1 to rat lung, we have been able to study the effect of TGF-beta1 protein in the respiratory tract directly. We have demonstrated that transient overexpression of active, but not latent, TGF-beta1 resulted in prolonged and severe interstitial and pleural fibrosis characterized by extensive deposition of the extracellular matrix (ECM) proteins collagen, fibronectin, and elastin, and by emergence of cells with the myofibroblast phenotype. These results illustrate the role of TGF-beta1 and the importance of its activation in the pulmonary fibrotic process, and suggest that targeting active TGF-beta1 and steps involved in TGF-beta1 activation are likely to be valuable antifibrogenic therapeutic strategies. This new and versatile model of pulmonary fibrosis can be used to study such therapies.

/pdf/adenovector-mediated-gene-transfer-of-active-transforming-4ssshu2gs8.pdf

Adenovector-mediated gene transfer of active transforming growth factor-beta1 induces prolonged severe fibrosis in rat lung.

Due to its avascular nature, articular cartilage exhibits a very limited capacity to regenerate and to repair. Although much of the tissue-engineered cartilage in existence has been successful in mimicking the morphological and biochemical appearance of hyaline cartilage, it is generally mechanically inferior to the natural tissue. In this study, we tested the hypothesis that the application of dynamic deformational loading at physiological strain levels enhances chondrocyte matrix elaboration in cell-seeded agarose scaffolds to produce a more functional engineered tissue construct than in free swelling controls. A custom-designed bioreactor was used to load cell-seeded agarose disks dynamically in unconfined compression with a peak-to-peak compressive strain amplitude of 10 percent, at a frequency of 1 Hz, 3 x (1 hour on, 1 hour off)/day, 5 days/week for 4 weeks. Results demonstrated that dynamically loaded disks yielded a sixfold increase in the equilibrium aggregate modulus over free swelling controls after 28 days of loading (100 +/- 16 kPa versus 15 +/- 8 kPa, p < 0.0001). This represented a 21-fold increase over the equilibrium modulus of day 0 (4.8 +/- 2.3 kPa). Sulfated glycosaminoglycan content and hydroxyproline content was also found to be greater in dynamically loaded disks compared to free swelling controls at day 21 (p < 0.0001 and p = 0.002, respectively).

Karlheinz Stalder

Papers

Determination of hydroxyproline.

Einbau von β-Aminopropionitril in die Kollagenmolekel beim Lathyrismus der Ratte

On the isomerization of hydroxyproline

[Metabolic experiments with 6-aminocaproic acid].

Die Hämolyse von Warm- und Kaltblütererythrozyten durch Quarz