Association Between Chondrocyte Hypertrophy and Angiogenesis of Cartilage in Osteoarthritis

Laurence Pesesse¹, Christelle Sanchez², Jean-Pierre Delcour³, Caroline Baudouin⁴, Philippe Msika⁴ and Yves Henrotin⁵, ¹Bone and Cartilage Research Unit, University of Liège, Liège, Belgium, ²Bone and Cartilage Research Unit, University of Liège, Liege, Belgium, ³Orthopedic surgery, Centre hospitalier du Bois de l'Abbaye, Seraing, Belgium, ⁴IRD Direction, Laboratoires Expanscience, Epernon, France, ⁵University of Liège, Bone and Cartilage Research Unit, Liège, Belgium

Meeting: 2012 ACR/ARHP Annual Meeting

Keywords: Angiogenesis, cartilage and osteoarthritis

Session Information

Title: Cell-cell Adhesion, Cell Trafficking and Angiogenesis

Session Type: Abstract Submissions (ACR)

Background/Purpose:

Chondrocyte hypertrophy is commonly observed in OA cartilage, associated with matrix mineralization and vascularization. In our previous work, we demonstrated that hypertrophic differentiation of chondrocytes is initiated by serum-enriched medium in long-term culture in alginate beads suggesting a role played by blood supply in the hypertrophic differentiation of chondrocytes in OA.

As hypertrophic differentiation of chondrocytes is an important feature of osteoarthritis (OA), we developed a model of culture in order to study the functional consequences of hypertrophic OA chondrocytes. The aim of this study was to investigate the link between hypertrophic differentiation of chondrocytes and angiogenesis in OA in order to demonstrate that OA hypertrophic chondrocytes expressed an angiogenic phenotype and that some specific factors could be implicated in both processes.

Methods:

Articular OA chondrocytes were cultured for 28 days in alginate beads in medium containing 2% Ultroser G (UG) or 10% Fetal Bovine Serum (FBS). DNA was quantified by fluorimetry. The expression of hypertrophy markers genes type X collagen (col10a1), runt-related factor 2 (runx2) and matrix metalloprotease 13 (MMP13) and a screening of angiogenic factors was evaluated by RT‐PCR. Alkaline phosphatase (AP) activity and 5’phosphodiesterase activity of NTPPPH were quantified by specific enzymatic methods. Non-hypertrophic and hypertrophic human OA chondrocyte conditioned media were used to perform functional tests with huvecs: migration, invasion and wound healing assays. Data were analyzed by one-way ANOVA.

Results:

In alginate beads, chondrocytes cultivated in serum-supplemented medium underwent a hypertrophic differentiation process characterized by significant increased expression of hypertrophic markers and mineralization enzymes (col10a1: p<0.05; runx2: p<0.01; MMP13: p<0.001; PA: p<0.001; NTPPPH: p<0.001). Functional angiogenesis assays showed that chondrocyte hypertrophy positively influenced migration (p<0.0001), invasion (p<0.0001) and wound healing (p=0.0005) of endothelial cells. Among the screened angiogenic factors, bone sialoprotein (BSP) was highly upregulated in hypertrophic chondrocytes (p<0.05).

Conclusion:

Our culture model allowed to mimic hypertrophic differentiation of chondrocytes and to investigate the relationship between this process and functional invasion and migration of endothelial cells, two functional steps in the process of angiogenesis. The results obtained in this study highlighted BSP as a specific factor that could be implicated in hypertrophic differentiation of chondrocytes and cartilage angiogenesis.

Disclosure:

L. Pesesse,
None;

C. Sanchez,
None;

J. P. Delcour,
None;

C. Baudouin,
None;

P. Msika,
None;

Y. Henrotin,
None.

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