Radiation synovectomy with yttrium-90 for persisting arthritis has direct harmful effects on human cartilage that cannot be prevented by co-administration of glucocorticoids: an in vitro study

Current role for radioisotope synovectomy

Radioisotope synovectomy has been extensively used to treat patients with chronic inflammatory joint disease but has moved to a less prominent position since the introduction of new and highly effective drugs. Remaining indications are refractory synovitis, pigmented villonodular synovitis as an adjunct to surgery, and hemophilic arthropathy. The three main radioisotopes used are yttrium-90, rhenium-186, and erbium-189. Radioisotope synovectomy should be performed only by highly experienced professionals, to minimize the risk of injection-related complications. The available safety data, in particular regarding the risk of malignancy, are reassuring. The efficacy of yttrium-90 in chronic inflammatory joint disease remains controversial.

Availability of yttrium-90 from strontium-90: a nuclear medicine perspective

Yttrium-90 (T(½) 64.1 hours, E(βmax)=2.28 MeV) is a pure β⁻ particle emitting radionuclide with well-established applications in targeted therapy. There are several advantages of ⁹⁰Y as a therapeutic radionuclide. It has a suitable physical half-life (∼64 hours) and decays to a stable daughter product ⁹⁰Zr by emission of high-energy β⁻ particles. Yttrium has a relatively simple chemistry and its suitability for forming complexes with a variety of chelating agents is well established. The ⁹⁰Sr/⁹⁰Y generator is an ideal source for the long-term continuous availability of no-carrier-added ⁹⁰Y suitable for the preparation of radiopharmaceuticals for radionuclide therapy. The parent radionuclide ⁹⁰Sr, which is a long-lived fission product, is available in large quantities from spent fuel. Several useful technologies have been developed for the preparation of ⁹⁰Sr/⁹⁰Y generators. There are several well-established radiopharmaceuticals based on monoclonal antibodies, peptides, and particulates labeled with ⁹⁰Y, that are in regular use for the treatment of some forms of primary cancers and arthritis. At present, there are no generators for the elution of ⁹⁰Y that can be set up in a hospital radiopharmacy. The radionuclide is procured from manufacturers and the radiopharmaceuticals are formulated on site. This article reviews the development of ⁹⁰Sr/⁹⁰Y generator and the development of ⁹⁰Y radiopharmaceuticals.

Efficacy of radiosynoviorthesis and its impact on chosen inflammatory markers

Radiosynoviorthesis is used for the local treatment of recurrent joint effusions and leads to synovium necrosis after radionuclide administration. This procedure provides opportunity to full recovery of normal synovium function after local corticosteroids and systemic modifying drugs failure.

Complications following radiosynoviorthesis in osteoarthritis and arthroplasty: osteonecrosis and intra-articular infection

OBJECTIVES

In the literature, radiosynoviorthesis (RSO) has been associated only with a small number of complications. There is a trend towards increasing the use of RSO in diverse indications. After repeatedly observing several complications following RSO, a retrospective evaluation was undertaken to estimate the safety of this method.

METHODS

Between 1995-2007, we evaluated the outcome of RSO in 93 patients (143 knees, seven hips, seven shoulders, three elbows, one ankle) who presented to our orthopaedic department after joint treatment with yttrium-90((90)Y) or Rhenium-186((186)Re) colloid in an external nuclear medicine institution.

RESULTS

Seventy-nine of the 93 RSO treated patients had advanced primary or secondary osteoarthritis (OA), 12 had an arthroplasty. In seven cases, rheumatoid arthritis (RA) was responsible for secondary OA. The benefit in pain relief, as self-reported by the patients was low. Twenty-two of the 93 patients showed complications following RSO. We observed osteonecrosis (ON) in 19 and infection in five patients, including two with both complications. These findings were proven clinically, radiologically, intraoperatively, microbiologically and histologically. Statistical analysis revealed a strong correlation of arthroplasty to infection (rho=0.798, alpha=0.01), and a strong correlation of chronic obstructive pulmonary disease (COPD) and RA to ON following RSO (rho=0.674, alpha=0.01). Diabetes mellitus (DM) was also significantly correlated to ON after RSO treatment (rho=0.488,alpha=0.05).

CONCLUSIONS

Our data suggest that RSO may not be as safe as it has previously been reported, especially in advanced OA and arthroplasty.

Thrombin-sensitive photodynamic agents: a novel strategy for selective synovectomy in rheumatoid arthritis

Protease-sensitive macromolecular prodrugs have attracted interest for bio-responsive drug delivery to sites with up-regulated proteolytic activities such as inflammatory or cancerous lesions. Here we report the development of a novel polymeric photosensitizer prodrug (T-PS) to target thrombin, a protease up-regulated in synovial tissues of rheumatoid arthritis (RA) patients, for minimally invasive photodynamic synovectomy. In T-PS, multiple photosensitizer units are tethered to a polymeric backbone via short, thrombin-cleavable peptide linkers. Photoactivity of the prodrug is efficiently impaired due to energy transfer between neighbouring photosensitizer units. T-PS activation by exogenous and endogenous thrombin induced an increase in fluorescence emission by a factor of 16 after in vitro digestion and a selective fluorescence enhancement in arthritic lesions in vivo, in a collagen-induced arthritis mouse model. In vitro studies on primary human synoviocytes showed a phototoxic effect only after enzymatic digestion of the prodrug and light irradiation, thus demonstrating the functionality of T-PS induced PDT. The developed photosensitizer prodrugs combine the passive targeting capacity of macromolecular drug delivery systems with site-selective photosensitizer release and activation. They illuminate lesions with pathologically enhanced proteolytic activity and induce cell death, subsequent to irradiation.

Very rapid clearance after a joint bleed in the canine knee cannot prevent adverse effects on cartilage and synovial tissue

OBJECTIVE

Joint bleeding leads to joint destruction. In vitro exposure of human and canine cartilage to blood results in long-lasting severe adverse changes in cartilage. An in vivo joint haemorrhage in the canine knee joint demonstrates similar adverse effects although significantly less outspoken. As a possible explanation for this discrepancy, we studied the clearance rate of blood from the canine knee joints.

METHODS

Blood was injected into the knee joint of Beagle dogs either 48 h, 24h or 15 min before termination. The amount of red blood cells (RBC) and white blood cells (WBCs) present in the joint cavity was determined. Chondrocyte activity and cartilage matrix integrity as well as cartilage destructive activity of synovial tissue were determined biochemically. Additionally, synovial tissue was analyzed by use of histochemistry.

RESULTS

The amount of blood was decreased to <5% within 48 h. Within this time period the cartilage was negatively affected and the synovial tissue showed cartilage destructive activity. Evaluation of the synovial tissue 15 min post-injection revealed countless numbers of intact RBC that were almost completely disappeared after 48 h without significant recruitment of macrophages.

CONCLUSIONS

Blood is cleared very rapidly from the canine knee joint, but already has adverse effects on both cartilage and synovial tissue within that short time span. This rapid clearance can play a role in the discrepancy between long-term in vitro and in vivo effects of blood-induced joint damage since more than 10% v/v blood present for at least 48 h is needed to induce long-term adverse effects in vitro.