Purpose

The best care paradigm for the older patient with proximal humeral fracture/dislocation is typically hemiarthroplasty, yet post-operative instability and suboptimal functional outcomes are commonplace. The aim of this study was to compare innovative treatment strategies designed to improve outcomes including: hemiarthroplasty combined with capsulolabral repair versus reverse total shoulder arthroplasty.

Introduction and Aims: Aberrations in the balance of chondrocyte metabolism play an integral role in the degeneration of articular cartilage and subsequent osteoarthritis. Gene expression profiling allows a comparison of levels of mRNA expression in large numbers of genes simultaneously. This study compares the mRNA expression from osteoarthritic cartilage in knees and hips with that of normal cartilage.

Method: Human cartilage samples were obtained from osteoarthritic knees and hips at the time of joint arthroplasty surgery. ‘Normal’ cartilage was obtained from femoral heads after fracture or from radial heads after trauma. Cartilage samples were either snap frozen in liquid nitrogen or enzymatically digested and established in primary cell culture prior to RNA isolation. The RNA was reverse-transcribed to cDNA, labelled with a fluorochrome and then hybridised to gene chips.

Results: In addition to confirming that cells raised in primary cell culture dedifferentiate to a fibroblast-like state and cease to synthesise normal products of cartilage matrix we have also developed a reproducible method of processing snap frozen cartilage samples in order to produce a sufficiently pure quantity of mRNA to be used in gene chip technology. We now have gene chips completed for a ‘normal’ control, a standard osteo-arthritic knee and an osteoarthritic hip with a significant genetic history of early onset osteoarthritis. Early analysis and comparison of the data from these chips identifies some potential candidate genes for further analysis.

Conclusion: Human articular cartilage lends itself to gene profiling using cDNA arrays as it contains only one cell type. Thus any changes in gene expression levels can be directly attributable to the chondrocyte. This early data analysis opens the door to a new search for the ‘arthritis gene’. For the data to be meaningful we will need to process gene chips on several more samples of arthritic and ‘normal’ cartilage.

Introduction Aberrations in the balance of chondrocyte metabolism play an integral role in the degeneration of articular cartilage and subsequent arthritis. Gene expression profiling is a powerful tool which allows identification of differences in levels of mRNA expression of large numbers of genes simultaneously. The objective of this study was to compare mRNA expression from osteoarthritic cartilage with that of normal cartilage and by use of the Affymetrix system, identify target genes for further investigation.

Methods Human cartilage samples were obtained from osteoarthritic knees and hips at the time of joint replacement surgery. Non-arthritic cartilage samples were obtained from notchplasty at time of cruciate ligament replacement surgery or from trauma surgery. Cartilage samples were either snap frozen in liquid nitrogen and RNA directly isolated from the frozen tissue or enzymatically digested and established in primary culture prior to RNA isolation. The RNA was reverse transcribed to cDNA, labelled with a fluorochrome and then hybridised to gene chips. This will allow us to: 1. Compare whether RNA expression in cell culture accurately reflects that in the tissue itself. 2. Determine whether there are differences between the gene profiles of knee and hip osteoarthritis. 3. Select candidate genes for further analysis.

Results At present primary cell culture lines have been successfully established and are ready for RNA isolation. Frozen cartilage samples have undergone RNA isolation. Currently techniques are underway to maximise RNA extraction and sufficiently purify it to process a gene chip. Once the gene chip is made a list of up or down-regulated genes will be available for analysis. Human articular cartilage lends itself to gene profiling using cDNA arrays as it contains only one cell type. Thus any changes in gene expression levels can be directly attributed to the chondrocyte.

Conclusions This technology opens the door to a new search for the ‘arthritis gene’.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.