Bone marrow aspiration concentrate and platelet rich plasma for osteochondral repair in a porcine osteochondral defect model.

BACKGROUND: Bone marrow aspiration concentrate (BMAC) may possess a high potency for cartilage and osseous defect healing because it contains stem cells and multiple growth factors. Alternatively, platelet rich plasma (PRP), which contains a cocktail of multiple growth factors released from enriched activated thrombocytes may potentially stimulate the mesenchymal stem cells (MSCs) in bone marrow to proliferate and differentiate. METHODS: A critical size osteochondral defect (10×6 mm) in both medial femoral condyles was created in 14 Goettinger mini-pigs. All animals were randomized into the following four groups: biphasic scaffold alone (TRUFIT BGS, Smith & Nephew, USA), scaffold with PRP, scaffold with BMAC and scaffold in combination with BMAC and PRP. After 26 weeks all animals were euthanized and histological slides were cut, stained and evaluated using a histological score and immunohistochemistry. RESULTS: The thrombocyte number was significantly increased (p = 0.049) in PRP compared to whole blood. In addition the concentration of the measured growth factors in PRP such as BMP-2, BMP-7, VEGF, TGF-β1 and PDGF were significantly increased when compared to whole blood (p<0.05). In the defects of the therapy groups areas of chondrogenic tissue were present, which stained blue with toluidine blue and positively for collagen type II. Adding BMAC or PRP in a biphasic scaffold led to a significant improvement of the histological score compared to the control group, but the combination of BMAC and PRP did not further enhance the histological score. CONCLUSIONS: The clinical application of BMAC or PRP in osteochondral defect healing is attractive because of their autologous origin and cost-effectiveness. Adding either PRP or BMAC to a biphasic scaffold led to a significantly better healing of osteochondral defects compared with the control group. However, the combination of both therapies did not further enhance healing

Immunohistochemical analysis for collagen II.

<p>Immunohistochemical analysis for collagen II of the regenerate cartilage in representative slides of all four groups. a) scaffold only b) PRP c) BMAC d) BMAC with PRP. No signs of degenerative changes in the adjacent cartilage were found. In the defects of the therapy groups, areas of chondrogenic tissue, which contained collagen II on the basis of positive immunostaining, were present. However, in the control group the regenerative tissue was generally fibrous. This tissue was deficient in collagen type II as shown by specific staining.</p

Differentiation assays on day 21.

<p>The differentiation of the mesenchymal stem cells from the bone marrow aspiration concentrate into osteoblasts became apparent by an intense blue staining for alkaline phosphatase activity (A). The adipocytes became apparent by the accumulation of lipid-rich vacuoles stained with PPAR (B) Cells cultured in chondrogenic medium showed a positive stain for chondrocyte markers over an increasing proportion of the pellet from 10 to 21 days (C).</p

Mean mononuclear cell count.

<p>The mean mononuclear cell count of both treatment groups (BMAC and BMAC+PRP) in bone marrow (BM) and bone marrow aspiration concentrate (BMAC). In the BMAC group there was a 3.17 (<i>p = 0.021</i>) fold increase of mononuclear cells in BMAC compared to BM, and in the BMAC+PRP a 2.42 (<i>p = 0.006</i>) fold increase of the mononuclear cells.</p

Mean number of platelets.

<p>The mean number of platelets in whole blood and in PRP in both treatment groups. In both groups we measured a significant increase (<i>p<0.001 and p = 0.049</i>) of the platelet number in PRP compared to whole blood.</p

Representative histological slides.

<p>Representative histological slides (stained with toluidine-blue) of each of the investigated groups, a) scaffold only b) PRP c) BMAC d) BMAC with PRP. In the treatment groups the regenerated tissue stained positive for sGAGs.</p

Modified O’Driscoll score.

<p>Modified O’Driscoll score.</p

Osteochondral defect.

<p>In all animals, a 6×10 mm cylindrical osteochondral defect in the medial femoral condyles of both knee joints was surgically created with a cylindrical chisel (a). The osteochondral graft (left) from the defect was measured and then the biphasic scaffold (right) was cut to the respective length of the graft prior to implantation (b). The cut scaffold was then supplemented with the respective supplement and implanted into the condyle (c).</p