Objectives

Intra-articular injections of local anaesthetics (LA), glucocorticoids (GC), or hyaluronic acid (HA) are used to treat osteoarthritis (OA). Contrast agents (CA) are needed to prove successful intra-articular injection or aspiration, or to visualize articular structures dynamically during fluoroscopy. Tranexamic acid (TA) is used to control haemostasis and prevent excessive intra-articular bleeding. Despite their common usage, little is known about the cytotoxicity of common drugs injected into joints. Thus, the aim of our study was to investigate the effects of LA, GC, HA, CA, and TA on the viability of primary human chondrocytes and tenocytes in vitro.

Due to well-known complications of metal-on-metal hip resurfacing arthroplasty the indication for this procedure has significantly decreased over the past years. As a high number of patients is currently living with resurfacing implants, however, there is a clear need for information about the longterm results and especially about the rate of local as well as systemic adverse effects.

We retrospectively reviewed our first 95 patients who had 100 consecutive BHR hip resurfacings performed from 1998–2001. Median age at surgery was 52 years (range, 28–69 years); 49% were men. After a mean follow-up period of 16.1 years (range 15.2 – 17.6 years) we assessed survival rate (revision for any reason as endpoint), radiographic changes and patient-related outcome in patients who had not undergone revision. In addition we measured whole blood concentrations of cobalt at follow-up.

17% of our patients in the original cohort were lost to follow-up. In the remaining patients the 16-year survivorship was 80.1%. The overall survival rate was slightly higher in males (80.6%) than in females (77.1%). The WOMAC overall score showed a median value of 91.7 points (range 35.4 – 100). Median whole blood ion levels were 1.9 µg/L for cobalt (0.6 – 140.2 µg/L), 14.9% of patients showed elevated levels. The number of patients with relevant radiographic signs of local adverse reactions to metal debris was relatively low.

In contrast to earlier reports and very few other longterm studies our results show an unsatisfactory performance of resurfacing. In particular the outcome of male patients deteriorated between 10 and 16 years of follow-up. Although only a small number of patients shows relevant elevation of metal-ion levels, the clinical relevance has still to be determined.

Metallic implants are widely used in orthopedic, oral and maxillofacial surgery. Durable osseous fixation of an implant requires that osteoprogenitor cells attach and adhere to the implant, proliferate, differentiate into osteoblasts, and produce mineralized matrix. We previously observed that human mesenchymal stem cells (MSCs) adherent to smooth tantalum (Ta) surfaces demonstrated superior biocompatibility compared with titanium (Ti) coatings.

The aim of the present study was to investigate the interactions between MSCs and smooth surfaces of Ta and by means of whole-genome microarray technology.

Immortalized human mesenchymal stem cells were cultivated on smooth surfaces of Ti and Ta. Total RNA was extracted after culturing for 1, 2, 4, and 8 days and hybridized to Affymetrix whole-genome microarrays (N=16). Replicate arrays were averaged and the ratios of gene expression by MSCs cultivated on Ta versus Ti coating were calculated. Absolute fold differences were also calculated and lists of upregulated genes were generated. Moreover, gene Ontology (GO) annotation analysis of differentially regulated genes was performed.

For both Ta and Ti coatings, the vast majority of genes were upregulated after 4 d of cultivation. Genes upregulated by MSCs cultivated on Ta coating for 4 d were annotated to relevant GO terms. Ti-regulated GO annotation clusters were predominantly transcription-related. By using the K-means clustering algorithm, 10 clusters containing more than 5 genes were identified. Moreover, various genes related to osteogenesis and cell adhesion were upregulated by MSCs exposed to Ta surface.

Microarray analysis of MSCs exposed to smooth metallic surfaces of both Ta and Ti generally showed a huge increase in transcriptional activity after 4 d of cultivation. According to GO annotation analysis Ta coating may induce increased adhesion and earlier differentiation of MSCs compared to Ti surface making Ta a promising biocompatible material for bone implants.

Major drawbacks associated with autologous bone grafting are the risk of donor site morbidity and its limited availability. Sterilized bone allograft, however, lacking osteoinductive properties, carries the risk of graft failure resulting from insufficient osseointegration of the graft.

The aim of this study was to vitalize bone allograft with human osteoprogenitor cells under GMP-conform conditions. For this purpose we investigated proliferation, osteogenic differentiation and large-scale gene expression of human MSCs cultured three-dimensionally on peracetic acid (PAA)-treated spongious bone chips.

MSCs were isolated from healthy donors (N=5) and seeded onto PAA-treated spongious bone samples (~5×5×5 mm, DIZG, Germany) under GMP-conform conditions. Proliferation (total protein assay), osteogenic differentiation (cell-specific ALP activity assay, quantitative gene expression analysis of selected osteogenic marker genes), and morphology were assessed. RNA was isolated and microarray analysis was performed using the PIQORTM Stem Cell Microarray system (Miltenyi Biotec) including 942 target sequences.

Increasing cellularity was observed during the 42 d observation period while cell-specific ALP activity peaked at day 21. Effective proliferation and adhesion of human MSCs on PAA-treated spongious bone was confirmed by histology, scanning electron and confocal laser scanning microscopy. Gene expression of early (Runx-2), intermediate (ALP), and late (osteocalcin) osteogenic marker genes was present during 42 days of cultivation. Microarray analysis of MSCs cultivated on bone allograft versus 2-D tissue culture demonstrated temporal upregulation of genes involved in extracellular matrix synthesis (e.g., matrix metalloproteases, collagens), osteogenesis (e.g., BMPR1b, Runx-2) and angiogenesis (angiopoietin, VEGF).

PAA-treated spongious bone allograft is a biocompatible carrier matrix for long-term ex vivo cultivation of MSCs as observed by favorable proliferation, cell distribution, gene expression profile, and persisting osteogenic differentiation. GMP-grade vitalisation of bone allograft by cultivation with autologous MSCs represents a promising clinical application for the treatment of osseous defects.