Redifferentiation of aged human articular chondrocytes by combining bone morphogenetic protein-2 and melanoma inhibitory activity protein in 3D-culture

<div><p>Melanoma inhibitory activity (MIA) affects the differentiation to hyaline cartilage and can inhibit the osteogenic potential of bone morphogenetic protein (BMP)-2 in mesenchymal stem cells (MSC). The aim of this study was to investigate if MIA also inhibits the osteogenic potential of BMP-2 in human articular chondrocytes during redifferentiation, which may lead to a higher grade of differentiation without calcification. HAC of four female patients (mean age: 73.75 ±6.98) were seeded into 3D culture for 28 days; after adding the recombinant proteins, four groups were formed (Control, BMP-2, MIA, BMP-2+MIA). Samples were analysed for gene expression, glycosaminoglycan (GAG) content and histology on day 0, 14 and 28. Collagen type 2 (<i>COL2A1</i>) was significantly increased in the BMP-2 containing groups on day 28; BMP-2 (100-fold, p = 0.001), BMP-2+MIA (65-fold, p = 0.009) and similar to the level of native cartilage. Higher aggrecan (<i>Agg</i>) levels were present in the BMP-2 (3-fold, p = 0.007) and BMP-2+MIA (4-fold, p = 0.002) group after 14 days and in the BMP-2 (9-fold, p = 0.001) group after 28 days. Collagen type 10 (<i>COL10A1</i>) was increased in the BMP-2 containing groups (6-fold, p = 0.006) but these levels were significantly below native cartilage. Alkaline phosphatase (<i>ALP</i>), collagen type 1 (<i>COL1A1</i>) and the glycosaminoglycan (GAG) content did not reveal any relevant differences between groups. BMP-2 is a potent inducer for differentiation of HAC. A significant enhancement of this effect in combination with MIA could not be observed. Furthermore no significant reduction of osteogenic markers during re-differentiation of chondrocytes was present combining BMP-2 and MIA.</p></div

Alcian blue staining of alginate beads in 10 and 20 times magnification.

<p>Scale in each slide corresponds to 100μm. (A) Control on day 14; (B) BMP-2 on day 14 (C) MIA on day 14; (D) BMP-2+MIA on day 14; (E) Control on day 28; (F) BMP-2 on day 28; (G) MIA on day 28; (H) BMP-2+MIA on day 28.</p

Relative gene expression of <i>COL10A1</i>.

<p>Relative gene expression of <i>COL10A1</i> normalised to native cartilage in log scale. Comparison of native cartilage (native), dedifferentiated cells—prior to 3D cultivation (cells), control on day 0 (CO d0), control and treated groups on day 14 and 28. * (p<0.05), ** (p<0.01).</p

Relative gene expression of <i>COL2A1</i>.

<p>Relative gene expression of <i>COL2A1</i> normalised to native cartilage in log scale. Comparison of native cartilage (native), dedifferentiated cells—prior to 3D cultivation (cells), control on day 0 (CO d0), control and treated groups on day 14 and 28. * (p<0.05), ** (p<0.01).</p

Relative gene expression of <i>COL1A1</i>.

<p>Relative gene expression of <i>COL1A1</i> normalised to native cartilage in log scale. Comparison of native cartilage (native), dedifferentiated cells—prior to 3D cultivation (cells), control on day 0 (CO d0), control and treated groups on day 14 and 28. * (p<0.05), ** (p<0.01).</p

Glycosaminoglycan content in relation to DNA content.

<p>Comparison of control on day 0 (CO d0), control and treated groups on day 14 and 28. * (p<0.05), ** (p<0.01).</p