[Dissertations 25 years after date 34. breakdown of collagen by fibroblasts and osteoclasts].

The remodeling of soft and hard connective tissue is ssential for the proper functioning of an organism and also for the proper functioning of a tooth. An element of this remodeling is the disintegration mediated by fibroblasts or osteoclasts. The precise means by which the remodeling process takes place was and continues to be in part unknown. This doctoral research was able to show that collagen fibres are absorbed by fibroblasts from the surrounding tissue and consequently broken down in the lysosomal apparatus. Osteoclasts, the only cell type capable of breaking down mineralized bone, also appear to be capable of absorbing collagens. It was demonstrated that intracellular bone collagens in these cells can be found in patients who sufferfrom the rare disease pycnodysostosis. It is postulated that, in the osteoclasts of these patients, the activity of one or more enzymes which break down protein were reduced or absent. During the last 25 years, significant advances in the understanding of the processes which underlie the bone remodeling.