Histomorfološke promjene zglobne hrskavice i subhondralne kosti glave bedrene kosti u bolesnika s osteoporozom i osteoartritisom : doktorski rad

CILJ: Utvrditi stupanj promjena subhondralne ploče i subhondralne trabekularne kosti u odnosu na stupanj degenerativnih promjena zglobne hrskavice glave bedrene kosti te utvrditi kakav je taj odnos u osteoporozi (OP), a kakav u osteoartritisu (OA). Cilj je istražiti počinju li promjene u subhondralnoj kosti ranije u odnosu na degenerativne promjene u zglobnoj hrskavici. Istražiti promjene ekspresije koštanog morfogenetskog proteina-7 (BMP-7) i hrskavičnih morfogenetskih proteina -1 i -2 (CDMP-1,-2) te OPG/RANK/RANKL sustava molekula u uzorcima zglobne hrskavice i subhondralne kosti ispitanika s OP i OA. ISPITANICI I METODE: Ispitivano je 106 uzoraka zglobne hrskavice i subhondralne kosti glave bedrene kosti ispitanika kojima su operacijski ugrađivane totalne endoproteze zgloba kuka zbog uznapredovalog osteoartritisa ili zbog prijeloma vrata bedrene kosti gdje je prijelom nastao uslijed pada što je ukazivalo na razvijenu osteoporozu. Na presjecima obojanim metodom SO i Goldner Trichrome izvršena je procjena oštećenja zglobne hrskavice koristeći Mankinov bodovni sustav. Na istim presjecima mjerena je debljina nekalcificirane i kalcificirane hrskavice te subhondralnog kortikalnog sloja. Histomorfometrija subhondralne kortikalne i trabekularne kosti učinjena je pomoću metode za analizu mikroskopske slike i radiološkom metodom mikro-kompjutorizirane tomografije (micro-CT). Mjereni su histomorfometrijski parametri: koštani volumen (BV/TV), debljina gredica (Tb.Th), broj gredica (Tb.N), razdvojenost gredica (Tb.S), structural model index (SMI), poroznost (Po(tot)), gustoća (Conn.D) i stupanj anizotropije (DA). Imunohistokemijskom metodom prikazane su promjene ekspresije BMP-7, CDMP-1 i CDMP-2 u zglobnoj hrskavici te OPG/RANK/RANKL molekula u zglobnoj hrskavici i subhondralnoj kosti. REZULTATI: Uspoređujući histomorfometrijske značajke kosti ispitanika s OP i OA u svim parametrima zglobne hrskavice i subhondralne kosti vide se značajne razlike. U uzorcima OP utvrđeni su različiti stupnjevi degenerativnih promjena zglobne hrskavice uz očuvanu debljinu V hrskavice te značajne promjene u debljini i intenzitetu koštane pregradnje odnosno stvaranja nove kosti u sloju kalcificirane hrskavice, subhondralne kompaktne kosti i subhondralne trabekularne kosti. U uzorcima razvijenog OA uz očuvane dijelove hrskavice subhondralni sloj kompaktne kosti je stanjen, dok je u uzorcima gdje je potpuno nestala hrskavica nastupila subhondralna skleroza uz intenzivno stvaranje novih lamela koštanog tkiva što je značajno za pregradnju kortikalne kosti. Imunohistokemijski uočava se pojačana ekspresija BMP-7, CDMP-1 i CDMP-2 u dubljim slojevima hrskavice i u hipertrofičnim hondrocitima. U uzorcima ispitanika s osteoporozom i osteoartritisom pojačana je ekspresija RANK i OPG molekula u kalcificiranom sloju zglobne hrskavice i u subhondralnoj kosti s pojačanom koštanom pregradnjom. ZAKLJUČAK: U uzorcima s osteoporozom debljina zglobne hrskavice je očuvana, ali se u samoj hrskavici nalaze različiti stupnjevi degenerativnih promjena. U istim tim uzorcima vide se značajne stanične i strukturne promjene u kalcificiranom sloju hrskavice, u subhondralnom sloju kortikalne kosti i u subhondralnoj trabekularnoj kosti. Budući je subhondralno stvaranje nove kosti značajka osteoartritičnih promjena, pojačana pregradnja u osteoporotičnim uzorcima upućuje da se rane promjene prema osteoartritisu zgloba kuka javljaju i u osteoporotičnih bolesnika premda se u kliničkom smislu tvrdi da se te dvije bolesti ne pojavljuju zajedno. To ukazuje da promjene započinju u mineraliziranim slojevima ispod zglobne hrskavice i prije nego što se radiološki mogu dijagnosticirati promjene hrskavice koje upućuju na razvoj osteoartritisa.OBJECTIVE: To determine the degree of changes in subchondral plate and subchondral trabecular bone in relation to the degree of degenerative changes in the articular cartilage of the femoral head respectively in osteoporosis (OP) and osteoarthritis (OA). The goal is to determine whether changes in subchondral bone have an earlier onset in relation to degenerative changes in articular cartilage. To investigate changes in expression of bone morphogenetic protein-7 (BMP-7) and cartilage morphogenetic protein-1 and -2 (CDMP-1, -2) and OPG / RANK / RANKL system in samples with OP and OA. PATIENTS AND METHODS: It was examined 106 samples of articular cartilage and subchondral bone layer taken from the femoral head after removal during the surgical procedure of hip endoprosthesis implantation due to advanced osteoarthritis or pathological fractures due to osteoporosis. In sections stained using Safranin O (SO) and Goldner Trichrome a damage assessment of articular cartilage using Mankins scoring system was performed. On the same sections, the thickness of cartilage layers was measured. The histomorphometry of compact and trabecular subchondral bone was performed by image analysis software for microscopic images and using micro-computerized tomography (micro-CT). Following histomorphometrical parameters were measured: bone volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.S), structural model index (SMI), porosity (Po(tot)), density (Conn.D) and the degree of anisotropy (DA). Using immunohistochemistry, the expression of BMP-7, CDMP-1 and CDMP-2 in articular cartilage and the expression of OPG / RANK / RANKL molecules in the articular cartilage and subchondral bone were analyzed. RESULTS: Comparing all analyzed parameters of subchondral bone and articular cartilage in samples with OA and OP, significant alterations were noticed. In OP samples varying degrees of degenerative changes in articular cartilage with preserved cartilage thickness and VII significant changes in thickness and intensity of bone remodeling and creation of new bone in the layer of calcified cartilage, subchondral compact bone and the subchondral trabecular bone was found. In advanced OA samples with parts of well-preserved cartilage, the thinning of subchondral compact bone layer was found. In OA samples with no cartilage, subchondral sclerosis with intensive formation of new bone which is important for the remodeling of cortical bone was found. Expression of BMP-7, CDMP-1 and CDMP-2 is enhanced in the deeper layers of cartilage and in hypertrophic chondrocytes. In OP and OA samples in the calcified layer of articular cartilage the expression of RANK and OPG molecules was found. In subchondral bone with increased bone turnover the expression of RANK and OPG is also positive. CONCLUSION: In samples with preserved thickness of articular cartilage (OP), varying degrees of degenerative changes are present. In the same samples significant cellular and structural changes in the calcified layer of cartilage are visible, also the subchondral layer of cortical bone and trabecular subchondral bone. Since the formation of new subchondral bone is a characteristic of osteoarthritis, the increased bone turnover found in OP samples is indicating that early OA changes occurs in OP patients despite clear clinical distinction between two entities. Those findings suggest that changes begin in the mineralized layers below the articular cartilage before imaging methods can diagnose changes in the articular cartilage specific for osteoarthritis development