DOS BULLETIN - Dansk Ortopædisk Selskab

2010-378_DOS nr. 3 2010 29/09/10 10:08 Side 124
Different responses to hypoxia of mesenchymal stem
cells compared to chondrocytes
Casper Bindzus Foldager, Anna Bay Nielsen, Bjørn Borsøe
Christensen, Moustapha Kassem, Cody Bünger, Martin Lind
Orthopaedic Research Lab, Aarhus University Hospital; Department of
Endocrinology and Metabolism, University Hospital of Odense,
Sports Trauma Clinic, Aarhus University Hospital
Background: Articular cartilage is a specialized tissue in which the
native chondrocytes are exposed to low oxygen tensions. This hypoxic
environment is essential for the chondrogenic viability. Hypoxia
inducible factors (HIFs) are believed to play an essential role in the adaption
to this environment. The most commonly used treatment for cartilage
defects is microfracture, which relies on mesenchymal stem cells
(MSCs) to differentiate into chondrocytes for subsequent cartilage production.
Purpose: The aim of this study is to investigate the response of hypoxia
on normal and differentiating MSCs compared to native chondrocytes.
Methods: Three cell cultures were used: 1. Human chondrocytes; 2.
Immortalized (TERT-) MSCs in chondrogenic differentiation medium
(diff); 3. TERT-MSCs in standard medium(std). The three groups were
divided into three oxygen tensions: 21%, 15%, and 5%. They were cultured
in groups for 1, 2, 7, and 14 days. Quantitative gene expression
analysis was obtained using qRT-PCR and protein synthesis was measured
with ELISA. Statistics were performed with ANOVA with repeated
measures.
Findings: Chondrocytes and TERT-MSCs(diff) did not show an increase
in HIF-1alpha and HIF- 2aplha with lowering of oxygen from 21% to
5%. However, TERT-MSCs(std) showed a significant 3-fold increase.
The expression of VEGF in chondrocytes showed 5-fold increase while
TERT-MSC(diff) showed a 8- fold increase and TERT-MSCs a 12-fold
increase.
Conclusion: Vascularization of regenerating cartilage is a main contributor
to the generation of fibrous tissue and failed cartilage formation.
This is the first study to describe the unfortunate response of stem cells
compared to chondrocytes, which might contribute significantly to the
understanding of impaired regeneration of cartilage using microfracture.
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