C. Mathieu (Vancouver, CA)

Aspect Biosystems Ltd. Genie Chimique

Presenter Of 2 Presentations

Podium Presentation Biomaterials and Scaffolds

23.3.2 - Chitosan oligomers alter the entire knee microenvironment when IA-injected post-bone marrow stimulation in a chronic defect rabbit model

Presentation Number
23.3.2
Presentation Topic
Biomaterials and Scaffolds
Lecture Time
10:39 - 10:48
Session Type
Free Papers
Corresponding Author
Disclosure
C. Mathieu, A. Lemay, S. Desmarais, L. Hotz, P. Chitnis- None; G. Chen, J Guzmán-Morales, M Lavertu - ORTHO RTI shareholders; R McCormack - ORTHO RTI consultant; C Hoemann - ORTHO RTI Board of Directors, shareholder, Grant contract.

Abstract

Purpose

Chitosan oligomers at various degrees of deacetylation (DDA) can modulate macrophages in vitro to release anti-inflammatory factors [1] and could potentially polarize synovial macrophages to an anti-inflammatory phenotype. This study evaluated the effect of intra-articular (IA) injections of chitosan oligomers administered post-operatively after bone marrow stimulation (BMS) of a chronic cartilage defect. We tested the hypothesis that oligomers alter synovial fluid composition, synovial macrophage phenotype, and early cartilage tissue regeneration, compared to saline-only and Synvisc® as a gold standard.

Methods and Materials

Following ethics-approved protocols, 4x4 mm bilateral cartilage defects were created in the femoral trochlea of skeletally mature NZW rabbits (N=12), brought to chronicity over four weeks, then microdrilled (four 0.9 mm diameter holes, 2 mm deep). At 1-week post-BMS, rabbits received 3 weekly IA-injections: 80% or 99% DDA chitosan formulation, saline (-CNL) or Synvisc®. Synovial fluid collected prior to surgeries and at necropsy was analyzed for hyaluronic acid concentration and differential cell counts. Synovial and cartilage repair tissues were analyzed histologically and repairing defects imaged ex vivo by high-frequency ultrasound.

Results

After 3 weeks of post-operative IA-injections, hyaluronic acid concentration was above 2 mg/mL and elevated relative to baseline at 0.72 mg/mL. Synovial fluid monocyte counts increased for all conditions except for 80% DDA chitosan that elicited a high neutrophil count (Fig. 1). Synovitis was observed for all conditions, but macrophage infiltration (RAM-11+) and vascularity were lower following 99% DDA oligomers IA-injections. Saline-injected knees had the most SafO+ cartilage repair tissues, suggesting that all biomaterials slowed chondro-induction (Fig. 2). Ultrasound imaging showed that drill holes were still repairing (Fig. 2).

icrs 2019 ia-inj chitosan figure-1 v2.png

icrs 2019 ia-inj chitosan figure-2.png

Conclusion

Post-BMS IA-injection of 99% DDA oligomers showed a similar outcome as Synvisc® in decelerating the repair rate but with a better potential for reducing synovitis induced by BMS.

Acknowledgements: Jun Sun, Quentin O'Kelly. Funding: CIHR, NSERC, GMU startup.

References: [1] Fong (2017).

Collapse
Podium Presentation Histology

23.4.5 - Synovial membrane response to bone marrow stimulation and IA-injections of saline or Synvisc® in a chronic cartilage defect rabbit model

Presentation Number
23.4.5
Presentation Topic
Histology
Lecture Time
11:06 - 11:15
Session Type
Free Papers
Corresponding Author
Disclosure
C. Mathieu, A. Lemay, S. Desmarais - None; G. Chen, J Guzmán-Morales, M. Lavertu - ORTHO RTI shareholders; R McCormack - ORTHO RTI consultant; C Hoemann - ORTHO RTI Board of Directors, shareholder, Grant contract.

Abstract

Purpose

The synovial membrane lines the inner surface of the joint cavity and has an important role in controlling the synovial microenvironment. Recent studies show that synovitis promotes arthritic disease progression in the knee [1], however little is known on the role of the synovial membrane in aiding or hindering tissue regeneration following cartilage repair therapy. This study aims to evaluate the response of the synovial membrane to bone marrow stimulation (BMS) by microdrilling of a chronic cartilage defect [2].

Methods and Materials

Following ethics-approved protocols, 4x4 mm unilateral or bilateral cartilage defects were created in the femoral trochlea of skeletally mature NZW rabbits (N=9), brought to chronicity over four weeks, and then microdrilled with four 0.9 mm diameter holes at 2 mm depth. Supra-patellar synovial membranes were collected 1 week and 3 weeks after BMS. Starting at 1-week post-BMS, N=6 rabbits were submitted to 3 weekly intra-articular injections of saline or Synvisc®. Synovial membranes were analyzed for lining thickness, blood vessel density by stereology and macrophages infiltration by histomorphometry.

Results

Following a small medial arthrotomy and BMS, the supra-patellar synovial membrane exhibits typical signs of synovitis. The synovial lining was significantly thicker at 1-week and at 3-weeks post-operative compared to the synovium of intact knees (Fig. 1). RAM-11+ macrophage infiltration increased progressively through 3 weeks (Fig. 2A), but recruitment of wound-healing M2 macrophages to the synovial subintima was the highest at 1-week then diminished after 3-weeks of saline or Synvisc® IA-injection (Fig. 2B).

icrs 2019 bms-synovium figure-1.png

icrs 2019 bms-synovium figure-2.png

Conclusion

Following BMS, the supra-patellar synovial membrane displayed a strong inflammatory response similar to synovitis and was sustained up to 3-weeks post-operative. This response could be required or detrimental to cartilage repair processes and requires further study.

Acknowledgements: We thank Jun Sun. Funding sources: CIHR, NSERC.

References: [1] Sellam (2010) Nat Rev Rheumatol; [2] Dwivedi (2019) J Tissue Eng Regen Med.

Collapse