Cartilage Technology for Advanced Learners

15. November 2006

Twenty years later, the autologous cartilage cell transplantation still suffers from a blatant lack of studies. But - data or no data, the old technology will be left behind now anyway. Biophysicians open new sources for cells and invent tricky carrier substances on their way to a new dream in hyaline.

He may say that, because he is one of the fathers of this method: Dr. Mats Brittberg of the Goeteborg University is in no way satisfied with the situation of autologous cartilage cell transplantation (ACT), about twenty years after its first application: "Still only a few good randomized-controlled studies are available", as Brittberg said at the Congress of the German Orthopedists and Orthopedic Surgeons in Berlin. That is why, to him, ACT still is the second choice method with cartilage damages, if other technologies fail. Which does not mean, that he is not convinced of its success: "In 95 percent of knee joint patients, disorders and function improve long-term", estimates the expert and refers to his own cohort of patients, he observes for more than ten years now.

ACT reloaded: Surgeon immerse into the Matrix

But the autologous cartilage cell transplantation has its weaknesses. This method is applied in case of an injury-related or degenerative cartilage defect. The body's own cartilage cells are taken from another area, cultivated in the laboratory and finally re-implanted in the area of the faulty cartilage. Because the used material is rather liquid, a periosteum lobe is being put on top, which has to be sewn up, so nothing leaks. "One of the disadvantages is, that a long-range arthrotomy is necessary", said Dr. Christoph Gaissmaier of the Unfallklinik Tübingen (casualty hospital). Even more problematic: A not insignificant share of the patients develop a hyperthrophy of the transplant, thus causing joint disorders. "Most likely it comes from the periosteum component", said Gaissmaier in Berlin. That's why the people from Tuebingen count on the modification of ACT working without periosteum – the matrix technology. In this version of ACT the removed and cultivated cartilage cells are bedded in a matrix of chondroitinsulfate and collagens. This is surrounded by a solid membrane, also made of collagen. The advantage: The whole lot does not leak. A water-proof suture with periosteum couverture is not necessary any more. That is one of the reasons, why a lot can be done minimal invasive. The experience of Gaissmaier and colleagues are not bad up so far: Only about one percent of the patients develop a hyperthrophy of the transplant. The old method causes ten- to twenty times as many.

Adult stem cells produce mainly scrap cartilage

Unwanted tissue reactions are not the only problem of ACT. Also the extraction of cells is not solved ideally. After all, intact cartilage is normally damaged here. In vitro breeding has its limits as well: Cartilage cells cannot be spawned indefinitely. This is problematic, insofar as experts like Brittberg point out time and again, that the described good results are only possible, if a large number of cells is used and if the cell concentration in the suspension is very high. It would be great to get cartilage cells from somewhere else. Those trained in biomedical discourse call – almost as a reflex – for the adult stem cell. Hyaline cartilage by venous blood withdrawal – that's something like the "it-does-everything-except-making-the-tea" of cartilage-"ology". In principle that works. Professor Wiltrud Richter of Heidelberg University turns for example mesenchymale stem cells into chondrocytes – virtually at the push of a button – by stimulation with the growth factor TGF. So far so good, but chondrocyte does by far not equal hyaline cartilage, as Richter was able to provide evidence for by e. g. genetic expression analyses. "With the established stem cell protocols developing in the direction of hypertrophic replacement cartilage, something diverges from mother nature", says Richter. Somewhat closer to nature, it shows what is going differently here. When the scientists implant their stem cell chondrocytes in a mouse, the joint cartilage generated was not smooth, but reminded rather of an arthrosis. The very "scrap cartilage".
Reincarnation for used joints
Of course this does not mean, that arthrotic cartilage is good for nothing. From Tuebingen we got word, that cartilage cells, won from a joint removed for a total prothesis with arthrosis, are absolutely suitable to supply the seed for autologic cartilage cell transplantation. Other than the TGF beta-stimulated stem cells, the extracted suspension does not differ from the one resulting from intact cartilage as cell donor. Dr. Dirk Albrecht of the Unfallklinik Tuebingen (casualty hospital) was able to detect in 13 patients, that suitable replacement cartilage from in vivo emerges as well. Now we don't want to hear you say again, that being sick is not good for anything.

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