Abstract
Aim of the study was to evaluate if abrasion-arthroplasty (AAP) and abrasion-chondroplasty (ACP) leads to a release of mesenchymal stem cell (MSC) like cells from the bone marrow to the joint cavity where they probably differentiate into a chondrogenic phenotype.
Introduction
Cartilage demage is a sever problem in our aging society. About 5 million people only in Germany are affected. Osteoathritis is a degeneration of cartilage caused by aging or traumata 50 % of the people over 40 have signs of osteoarthritis. But the ability of self-regeneration of cartilage is strongly limited. There are different approaches to therapy osteoathritic lesions. Arthroscopic treatment of OA includes bone marrow stimulation technique such as abrasion arthroplasty (AAP) and microfracturing (MF). Beside the support of chondrocyte progenitor cells the environment is also important for the commitment to chondrocytes. Therefore insulin-like growth factor-1 (IGF-1) and transforming growth factor beta-1 (TGF-β1) are important factors during the regeneration process. In the present study we characterised the heamarthrosis and the released cells after AAP and its ability to differentiate into the chondrocyte lineage.
Material and Methods
Postoperative haemarthrosis was taken 5, 22 or 44 hours after surgery. 7.5 mg Dexamethasone (Corticosteroid) was administered into the knee joint to prevent postoperative inflammation. Mononuclear cells were isolated from haemarthrosis from the drainage bottle by ficoll density gradient centrifugation. The isolated cells were characterised using fluorescence-activated cell-sorting (FACS) analysis for characteristic markers of MSC such as CD 44, 73, 90, 105. After expanding cells were cultured in a pellet culture. After 3 weeks, histochemistry and immunohistochemistry against Sox9, collagen II and proteoglycan were performed. The release of IGF1, BMP4 and BMP7 was analysed in haemarthrosis serum by ELISA and Luminex technology.
Results
The isolated cells after AAP are positive for the mesenchymal stem cell marker CD105, CD90, CD73, CD 44 and negative for the marker of hematopoetic stem cells CD 34. Isolated cells after ACP couldn't be expanded for further characterizations. The staining of the 3D-culture revealed a positive signal for the chondrogen transcription factor Sox9 and the expression of extracellular markerproteins like collagen type II and proteoglycan. Both surgery techniques, AAP and ACP provides a chondrogenic environment. We were able to detect IGF-1, TGFß, BMP4 and BMP7 in the haemarthrosis.
Discussion
The benefit of abrasion arthroplasty surgery and microfracturing is controversial discussed because they do not consistently result in hyaline cartilage.
But the opening of the bone marrow allows the release of monocytic cells which have the potential to differentiate into a chondrogenic phenotype. In 3D-culture these cells express Sox9 and a collagen proteoglycan rich matrix. The haemarthrosis provides also a cartilage-stimulating environment. We could detect IGF1, TGFβ, BMP4 and 7 which could enhance the commitment concerning differentiation of MSCs to a chondrogenic lineage concerning the production of cartilage specific extracellular matrix.
Taken together our study provides the evidence for a therapeutic benefit of opening bone marrow in order to generate neocartilage after AAP.
