ROLE OF ALFACALCIDIOL ON BONE QUALITY AND IMMUNOMODULATION IN AUTOIMMUNE-DISEASE AND ORGAN-TRANSPLANTATION

In autoimmune diseases, as well as in organ transplantation, corticost eroids are often an obligatory part of the treatment regimen. The dele terious effect of corticosteroids on bone metabolism is well known, al though still controversial [1-3]. It is easier to maintain bone mass t han to restore it. Although the treatment of choice for prevention of bone loss is hormone replacement therapy, it cannot always be applied, and for many reasons compliance is low over the world. Alternative st rategies to prevent bone loss are now tried out in many centers. Calci tonin and bisphosphonates ate well-known antiresorbing drugs, but cost s and long-term efficiency for calcitonin and fear for bone toxicity f or the bisphosphonates limits their use for prevention. An attractive strategy to prevent osteoporosis is the treatment with alfacalcidiol b ecause it is a natural product with important effects on bone metaboli sm in physiological and pharmacological dosages. Calcium absorption fr om the gut and mineralization of the bone matrix are optimalized by al facalcidiol. The purpose of this paper is to report on our experience with alfacalcidiol concerning bone mass and quality in corticosteroid- induced osteoporosis in experimental animals and on long-term bone qua lity in autoimmune diseases and organ transplantation. We have studied the effects of alfacalcidiol on bone mass and quality in ovariectomiz ed animals with and without corticosteroids. In these fundamental stud ies we have found that alfacalcidiol had a profound protective and cur ative effect not only on bone mass but also on bone quality as tested by mechanical testing, namely, impact torsional loading test of whole bones. The combination of alfacalcidiol with estrogens was less effect ive than alfacalcidiol, but more effective than estrogens alone [4-6] (Fig. 1).