Introduction

© 1997 Blackwell Science Ltd 25 Hyaluronan (hyaluronic acid) was discovered in the vitreous humour and characterized as a polysaccharide as long ago as 1934 [1]. Twenty years later its exact chemical structure was determined [2]. In endocrinology, hyaluronan attracted early attention for its excessive accumulation in the skin, joints and serous cavities in myxoedema; for its seemingly paradoxical abundance in malignant exophthalmos and pretibial myxoedema, with little direct relation to the level of thyroid function; and for its response to hormones in the sexual skin of animals. Indeed, research in these fields has made numerous fundamental contributions to the subject including the discovery that hyaluronan synthesis is promoted by long-acting thyroid stimulator. (For reference to this work the readers are referred to a recent review [3].) Although research on endocrine aspects of hyaluronan metabolism continues we have chosen to focus the Minisymposium on fields where the study of hyaluronan has been relatively neglected in the past but is now beginning to influence clinical practice, especially as an index of disease activity and response to treatment; and secondly, on certain aspects of the biology of hyaluronan that are pertinent to current studies of its role in the course and causation of disease. Forty years after its discovery hyaluronan was used as a therapeutic agent in veterinary medicine [4] and 10 years later it was an established aid in cataract surgery [5] and a commercial success. Now, more than 60 years after the paper of Meyer & Palmer [1], hyaluronan is also commonly used for intra-articular injections in osteoarthritis in humans [6]. Furthermore, hyaluronan can be analysed in nanogram quantities in blood and other body fluids and these analyses have turned out to be of diagnostic value in various disorders, for example in liver disease [7]. It has also been demonstrated that hyaluronan accumulates in inflammatory sites (e.g. rheumatic joints, pulmonary disorders, myocardial infarction and rejected organ transplants) which may impair the normal functions of the organs (see Gerdin & Hällgren (pp. 49–55)) in this Minisymposium). It should be added that hyaluronan is being applied to numerous other tasks, for example as a drug carrier, as a tissue replacement, to prevent adhesions after abdominal surgery, to prevent restenosis after vascular surgery, in cancer treatment, etc. Even if only few of these applications should turn out to be of permanent value, hyaluronan has already established itself as a clinically interesting compound which justifies a Minisymposium in the Journal of Internal Medicine. The contributors to this symposium review recent developments in the biochemistry of hyaluronan (Fraser et al.) and discuss its important role in embryonal development (Toole) and the general background for a role in malignancies (Delpech et al.). These three papers are followed by five articles by clinical experts who discuss hyaluronan in connective tissue activation (Gerdin & Hällgren), joint disorders (Engström-Laurent), skin disorders (Juhlin), liver disorders (Lindqvist) and sepsis (Berg). As the symposium is directed towards readers of Internal Medicine, surgical aspects of hyaluronan, for example in ophthalmology and orthopaedic surgery, have been excluded. It is our hope that this Minisymposium will further the knowledge of hyaluronan in the clinical community.