Altered in vitro chondrogenic properties of chondrocytes harvested from unaffected cartilage in osteoarthritic joints1

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Summary

Objective

In vitro models of chondrogenesis often depart from chondrocytes harvested from less-affected areas of osteoarthritic joints. However, there are indications that these chondrocytes are phenotypically different from chondrocytes from healthy joints and thus might differ in their capacity to generate hyaline cartilage. The goal of this study was to compare the chondrogenic capacity of chondrocytes from healthy and OA joints.

Design

Chondrocytes isolated from nine healthy and nine OA knee joints were expanded in monolayer for two passages. Chondrocytes from passages 1 and 2 were analyzed for expression of (de)differentiation and hypertrophy markers and were seeded at passage 2 on collagen-coated filters for redifferentiation culture to study cartilage matrix formation.

Results

The collagen II/I mRNA ratio, reflecting differentiation, decreased from passage 1 to 2 in both chondrocytes from OA joints and chondrocytes from healthy joints (P < 0.05), without a significant difference between the two donor types. At passage 1, levels of the cartilage transcription factors Sox-5, Sox-6 and Sox-9 appeared to be higher in chondrocytes from OA joints (n.s.), but this was not seen at passage 2. However, a clear difference was observed in collagen type X expression, which was high in chondrocytes from OA joints at both passages, while undetectable in chondrocytes from healthy joints (P < 0.01). Tissue generated by chondrocytes from healthy joints redifferentiated for 28 days, showed a significantly better morphology, as assessed by histological scoring (P < 0.01) and higher proteoglycan content (P < 0.05), compared to chondrocytes from OA joints. Matrix turnover parameters, i.e., proteoglycan synthesis and degradation rate, were not significantly affected by donor tissue origin.

Conclusions

These results suggest that clear differences between chondrocytes from healthy and OA joints exist and that these are not completely abolished during the process of de- and redifferentiation. Therefore, in vitro cartilage regeneration models, which use chondrocytes from OA joints, should be interpreted with care.

Key words

Cartilage
Tissue engineering
Osteoarthritis
Chondrocytes
Culture technique

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1

Investigation was performed at the Department of Orthopaedics at the University Medical Center Utrecht, The Netherlands. Funding: Dr Saris is supported by the Netherlands Organisation for Health Research and Development (NWO). Dr Auw Yang is supported by the Anna Foundation and the Foundation “De Drie Lichten” in The Netherlands.