A. Subramanian (Huntsville, UM)
University of Alabama-HuntsvillePresenter Of 1 Presentation
12.2.5 - Low-Intensity Ultrasound Attenuates IL-6 and TNFα-induced Catabolic Effects and Repairs Chondral Fissures in Osteochondral Explants
Abstract
Purpose
Cartilage repair takes place in a joint environment, with elevated levels of proinflammatory cytokines. The current work builds on our promising findings and demonstrates that cLIUS, when applied at cell resonant frequency of 5 MHz that maximizes cLIUS-induced bioeffects, promotes cartilage repair in a pro-inflammatory environment (IL6 and TNFα) by inhibiting the expression of catabolic factors and by promoting the chondrocytic phenotype.
Methods and Materials
8-mm bovine osteochondral explants with 4-mm cylindrical incisions were used. The incised explants were maintained under cLIUS stimulation (5 MHz, (14 kPa, 20 minutes, 4 times per day) in the cLIUS-assisted bioreactor as shown in Fig-1 Non-stimulated explants served as controls. Explant specimens were evaluated as shown in Fig-1.
Results
Histological assessment of the explants (Fig.2) displayed closed gaps and maintenance of tissue continuity in LIUS treated explants (panel IV) whereas visible gaps remained in non LIUS-treated controls (panel I). Cartilage-to-cartilage bonding was also observed in osteochondral explants exposed to IL6 or TNFa and treated with cLIUS (panels V and VI). Fissure or a cleft was observed in osteochondral explants exposed to IL6 or TNFa and not exposed to cLIUS (panels II and III). Loss of glycosaminoglycan (GAG) from the matrix was visible in explants treated with cytokines and not treated with cLIUS (Fig. 2, panel B/C). As expected, exposure of chondrocytes to pro-inflammatory cytokines resulted in over-expression of MMP13 and ADAMTS4/5, known matrix metalloproteinases and catabolic agents (Fig. 3A-B). Interestingly, cLIUS was observed to suppress the expression of MMP13 and ADAMTS4/5in osteochondral specimens exposed to IL6 and TNFa (Fig. 3A/B); while increasing the expression of TIMP1, an inhibitor of metalloproteinases (Fig. 3C).
Conclusion
Our work is expected to have broad translational importance in therapies that seek to employ LIUS in both regeneration and rehabilitation, and the knowledge gained will advance solutions to address the needs of persons with impaired joint function.