AB0156 INTRA-ARTICULAR AGRIN PROVIDES DIRECT PAIN RELIEF IN OSTEOARTHRITIS AND CARTILAGE DEFECTS

Background

Osteoarthritis is the leading cause of disability worldwide with a financial burden estimated between 1.5 and 2% of the GDP in all westernised countries. The main driver of progression in osteoarthritis is cartilage loss, which may be associated with bone changes, low degree synovitis and lesions to menisci and ligaments. These pathological features result in pain, which contributes to chronic disability.

Improving cartilage integrity without pain relief does not help patients and results in failure in clinical trials. Therefore, there is a need for therapeutics that induce rapid pain relief and long-term cartilage regeneration.

We previously showed that Agrin results in cartilage regeneration and in this study, following on the serendipitous finding of rapid pain relief after Agrin administration we explore its analgesic effect in animal models of osteochondral defects and osteoarthritis.

Objectives

Test the analgesic potential of Agrin in post-surgical pain associated with osteochondral defects in mice and sheep.

Determine whether Agrin can relieve chronic pain induced by osteoarthritis in mice.

Investigate the therapeutic potential of Agrin in models of primary and injury-induced secondary osteoarthritis.

Methods

Acute post-surgical pain: Surgery was performed on skeletally mature male mice and female sheep to create critical-sized osteochondral defects; defects were filled with collagen gel containing PBS or Agrin. Animals were sacrificed 8 weeks (mice) and 6 months (sheep) after surgery. Pain was measured in mice using von Frey filaments and incapacitance readings. Sheep were fitted with accelerometers for the duration of the study.

Osteoarthritic pain: Osteoarthritis was surgically induced in skeletally mature male mice by menisco-ligament injury (MLI). Control mice received sham surgery. Nine weeks post-surgery, once chronic pain was established, mice were injected intra-articularly with recombinant Agrin. Pain was measured by von Frey filaments and incapacitance.

Treatment in therapeutic regime: Tamoxifen-inducible transgenic mice overexpressing Agrin under the AggrecanCre promotor were generated. Skeletally mature male mice were subjected to menisco-ligament injury surgery. Four weeks later, tamoxifen was administered to overexpress Agrin in the cartilage. Pain was measured by von Frey filaments and incapacitance.

Ex-vivo: MicroCT, X-ray, Kellgren-Laurence scoring, histology, OARSI scoring and immunohistochemistry.

Results

In sheep, Agrin administration induced regeneration in osteochondral defects and, more importantly, reduced the levels of secondary osteoarthritis. This was associated with a rapid and sustained symptomatic relief.

In mice, Agrin expression was lost in the dorsal root ganglia corresponding to the limb subjected to MLI but not in the dorsal root ganglia corresponding to the sham operated limbs.

Intra-articular recombinant Agrin in mice with established OA (9 weeks after MLI surgery) resulted in pain relief as early as three hours after administration. Acute administration of recombinant Agrin does not have any analgesic effects in sham operated mice.

Inducible, cartilage-specific Agrin-overexpression mice were protected from developing pain associated with instability-induced osteoarthritis.

In mice with acute osteochondral defects, intra-articular Agrin administration resulted in pain relief for at least five days.

In humans, the loss of Agrin in the articular cartilage correlated significantly with the Mankin score of patients undergoing knee replacement surgery.

Conclusion

Agrin has analgesic properties in both the acute phases of cartilage damage and in established osteoarthritis. Our findings support the therapeutic use of Agrin for joint surface regeneration and pain relief.

Disclosure of Interests

Suzanne Eldridge: None declared, Aida Barawi: None declared, Anne-Sophie Thorup: None declared, Beatriz F Fernandez: None declared, Sabah Bharde: None declared, Shafaq Sikandar: None declared, Zeyu Guan: None declared, Magdalena Kaneva: None declared, Helen Lydon: None declared, Fran Henson: None declared, Cosimo De Bari: None declared, Andrew McCaskie: None declared, Francesco Dell’Accio Consultant of: Prof Dell’Accio has consulted for Samumed, Grant/research support from: A PhD studentship unrelated to this abstract is funded by UCB

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