Publisher Summary The development of the avian cornea involves a remarkable continuum of highly coordinated events. The corneal epithelium is the first of the component tissues to differentiate. This ectodermal derivative, with the help of the lens, secretes the highly ordered primary stroma composed of orthogonally arranged collagen fibrils embedded in a chondroitin sulfate (CS)-rich matrix. The fibroblasts of the avian cornea may produce the first fibronectin to appear within the stroma, although fibronectin is present earlier on the posterior stromal surface and lens. Several striking events occur together during the period of stromal condensation. An enzyme—hyaluronidase—appears, which may remove hyaluronic acid (HA), contributing to the dehydration that begins next to the endothelium and leads to the compaction of the posterior stroma. The dehydration of the stroma and acquisition of transparency are triggered by thyroxine. Thyroxine accelerates interdigitation of endothelial cells and conceivably tells this tissue to begin pumping water out of the cornea. The mitogenic effect of thyroxine on mammalian corneal epithelium in situ is mimicked by fibroblast growth factor (FGF) and epidermal growth factor (EFG), both of which stimulate stratification.

Development of the Vertebrate Cornea

Rumalon has shown itself clinically to be an effective medication for osteoarthrosis. The manner in which this GAG-peptide-complex acts upon the metabolism of cartilage and connective tissue has therefore been studied biochemically in various test systems both in vivo and in vitro. In studies on chicken embryos, Rumalon augmented the incorporation of radioactively tagged precursors into the proteoglycan and collagen of articular, sternal and costal cartilage. It was found that in particular the synthesis of the proteoglycan link proteins is promoted. The effect was most clearly apparent in the articular cartilage. Collagen synthesis in the connective tissue of the cornea and sclera was less markedly influenced. In rat granulomas after subcutaneous implantation of a polyurethane sponge, the synthesis of type I collagen was markedly increased while that of type III collagen was not. In investigations of the incorporation of the precursors of proteoglycan and collagen into normal and osteoarthrotic human cartilage, Rumalon stimulated collagen synthesis only in osteoarthrotic cartilage, which already showed a marked increase in synthesis in relation to the normal. Incorporation into proteoglycan was reduced in osteoarthrosis, the synthesis of the link proteins being particularly affected. Rumalon promoted the incorporation of precursors into proteoglycan in normal and osteoarthrotic cartilage, in particular into the link proteins. On the whole the results indicated that in these studies Rumalon tends to stabilise the cartilage matrix. Comparative studies were carried out with DAK 16, a high-molecular fraction from Rumalon, and various components of the GAG-peptide-complex. In this connection differing effects were observed. A striking feature was the marked activation by the bone marrow extract of the incorporation of glycosaminoglycan into proteoglycan. Otherwise the complete extract was found to be more effective than the investigated components. Rumalon hat sich klinisch als erfolgreiches Therapeutikum der Osteoarthrose erwiesen. Der Wirkungsmechanismus dieses GAG-Peptid-Komplex auf den Stoffwechsel von Knorpel und Bindegewebe wurde daher an verschiedenen Testsystemen in vivo und in vitro biochemisch untersucht. Rumalon erhohte in Untersuchungen am Huhnerembryo den Einbau von radiomarkierten Praecursoren in Proteoglykan und Kollagen von Gelenk-, Sternal- und Rippenknorpel. Es zeigte sich, das insbesondere die Synthese der Proteoglykan-Link-Proteine gefordert wird. Die Wirkung war am deutlichsten im Gelenkknorpel. Die Kollagensynthese in Bindegewebe von Kornea und Sklera wurde weniger beeinflust. Am Granulom der Ratte war nach subkutaner Implantation eines Polyurethanschwamms die Synthese von Typ I Kollagen deutlich verstarkt, nicht die von Typ III Kollagen. In Versuchen zum Einbau der Praecursoren von Proteoglykan und Kollagen in normalen und osteoarthrotischen menschlichen Gelenkknorpel stimulierte Rumalon die Kollagensynthese nur am osteoarthrotischen Knorpel, der bereits deutlich verstarkte Synthese gegenuber der Norm zeigte. Der Einbau in Proteoglykan war bei Osteoarthrose reduziert, insbesondere war die Synthese der Link-Proteine betroffen. Rumalon forderte den Einbau von Praecursoren in Proteoglykan bei normalem und Osteoarthroseknorpel, insbesondere in die Link-proteine. Die Resultate fuhrten insgesamt zur Vorstellung, das Rumalon in diesen Untersuchungen zu einer Stabilisierung der Knorpelmatrix fuhrt. Vergleichende Untersuchungen betrafen DAK 16, eine hochmolekulare Fraktion aus Rumalon sowie verschiedene Komponenten des GAG-Peptid-Komplex. Dabei zeigten sich unterschiedliche Effekte. Auffallig war die hohe Aktivierung des Glykosaminoglykaneinbaus in Proteoglykan durch den Knochenmarkextrakt. Sonst erwies sich der Gesamtextrakt wirksamer als die untersuchten Komponenten.

Biochemische Untersuchungen zur Wirkungsweise des GAG-Peptid-Komplex Rumalon®

Summary In this chapter an attempt has been made to draw together the known biology of cartilage and some of the mechanisms thought to be responsible for its failure in arthritis The picture is far from complete but we are now in a good position to use this information to help appraise the pros and cons of the wide range of drugs now available to treat articular disorders For convenience, these drugs were classified as NSAIDs, corticosteroids and chondroprotective agents The influence of each of these classes on the metabolism of cartilage was examined in the light of published laboratory and clinical studies It has been clearly shown that not all NSAIDs are the same While many of the older drugs provided no benefit to cartilage metabolism, and in some instances suppressed it, the more recently discovered molecules appear to be free of these undesirable effects Tiaprofenic acid, diclofenac and piroxicam emerged as drugs with little or no harmful effects on cartilage metabolism when used at concentrations within the human therapeutic range For all NSAIDs, their potential effects on cartilage must be weighed against their respective anti-inflammatory potency, half-life, and effects on the gastric mucosa and other tissues Other chapters in this book have addressed these important problems The long-acting corticosteroids, betamethasone and triamcinolone hexacetonide, also appear to offer some benefit in the management of OA; however, as in RA, their use should be restricted to short-term applications In terms of cartilage metabolism the chondroprotective agents pentosan polysulphate, Arteparon ® and Rumalon ® have been the most extensively studied class of drugs While the laboratory studies have provided convincing evidence of their chondroprotective efficacy, it has been difficult to prove this clinically This dichotomy of opinion (laboratory versus clinical) stems largely from the inadequacy of the methodologies currently available for the objective clinical assessment of patient response to anti-rheumatic drug therapy With the advent of nuclear magnetic resonance imaging techniques and monoclonal antibodies to detect specific proteoglycan breakdown fragments in synovial fluid and plasma, the prospects for a unified research approach for the evaluation of these agents may now be possible

Anti-rheumatic drugs and cartilage

Cartilage bone-marrow extract has stimulated the collagen formation of articular as well as sternal cartilage collagen in chick embryo. Collagen biosynthesis has been stimulated also in other investigated tissues, i.e. in cornea and sclera of chick embryo as well as in sponge granuloma of rats, where mainly formation of collagen type I was stimulated. Glycosaminoglycans formation has also been increased after administration of cartilage bone-marrow extract.

Effect of Cartilage Bone-Marrow Extract on Articular Cartilage Collagen Formation

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Effect of Cartilage Bone-Marrow Extract on Articular Cartilage Collagen Formation