Current therapies of the degenerative joint disease osteoarthritis (OA) are limited to alleviate the main symptoms of pain and stiffness until at the end stage of the disease a joint replacement by a prosthesis becomes inevitable. Such an irreversible surgical intervention is particularly problematic for younger patients due to the limited durability of a prosthesis and increased risk of revision surgeries. We previously showed that Tissue Engineered Cartilage generated with autologous Nasal chondrocytes (N-TEC) is suitable for the repair of focal articular cartilage defects (Mumme et al., Lancet 2016). We then evaluated the compatibility of N-TEC in the more challenging OA environment where chronical inflammation is present (Acevedo et al., Sci Transl Med, 2021). Specifically, we investigated the in vitro ability of N-TEC to sustain prolonged exposure to soluble factors simulating an OA environment and to regulate the inflammatory profile of cells typically present in an OA joint. We then explored in different small and large animal models in vivo N-TEC engraftment with OA tissues. Safety of autologous N-TEC was finally addressed in two individual patients with diagnosed advanced knee OA.
Material and Methods: N-TEC were generated with expanded human nasal chondrocytes (NC) and exposed in vitro to an inflammatory cytokine cocktail (IL1b, IL6 and TNFa) or conditioned medium from OA-synoviocytes. Additionally, inflammatory factors secreted by synoviocytes and chondrocytes isolated from OA joints were quantified upon culture with N-TEC conditioned medium.
N-TEC generated with GFP-labelled human NC were combined with a bone-like tissue engineered with osteoblasts or osteochondral tissue explants from patients with OA and subcutaneously implanted in mice for 8 weeks.
OA was induced in an orthotopic sheep model by generation of full thickness cartilage defects in the femoral condyles. Two months after OA induction, N-TEC generated with GFP-labelled autologous sheep NC (sN-TEC) were implanted into the degenerated cartilage defects for up to 12 months and the repair tissue quality assessed immuno-/histochemically. In addition, inflammatory factors were quantified in the synovial fluids harvested from joints of healthy (before OA induction), OA (at the time of treatment) and treated sheep (at the time of explantation).
Safety of autologous N-TEC transplantation was tested in 2 patients with radiological signs of medial compartment OA (Kellgren and Lawrence grades 3 and 4, age 34 and 36) who were otherwise considered for unicondylar knee arthroplasty. N-TEC implantation was combined with corrective high tibial osteotomy to reduce abnormal mechanical loading due to varus malalignment.
Results: We demonstrated that N-TEC were able to maintain cartilaginous properties in different inflammatory in vitro models simulating conditions of an osteoarthritic joint. Importantly, factors secreted by N-TEC significantly reduced the secretion of several specific inflammatory cytokines by OA-synoviocytes, including IL6 and TNFα.
We showed that these effects were at least partially mediated by WNT (wingless/integrated) signaling, a pathway that is chronically upregulated in OA. Interestingly our transcriptomic analyses revealed that this pathway instead is repressed in NC, while the WNT inhibitor sFRP1 (secreted frizzled-related protein-1) is highly expressed. We confirmed sFRP1 to also be secreted by NC and observed that its chemical and genetic inhibition reduced the capacity of N-TEC to maintain cartilaginous properties at OA-like conditions. These observations suggested repression of WNT signaling as a possible mechanism enabling NC to resist / reduce inflammation.
OA bone/osteoblasts are known to release factors that can lead to phenotypic changes and degradation of cartilage tissue. When N-TEC were combined with OA bone tissues in different ectopic in vivo models, we could nevertheless demonstrate cell survival, N-TEC integration and maintenance of the cartilaginous properties. Successful engraftment of N-TEC was also observed in a weight bearing orthotopic sheep OA model. Identification of GFP-positive NC in the explant tissues confirmed sustained survival of the implanted cells over the study duration. Observed high levels of the inflammatory cytokines Il1b, IL8 and TNFα in the synovial fluids from OA joints decreased after treatment with N-TEC to cytokine levels comparable to healthy joints.
No adverse reactions occurred in our first treated patients. In a patient's self-reported Knee Injury and Osteoarthritis Outcome Score (KOOS) both patients stated improvements in all the categories, including reduced pain, improved joint function and life quality until 14 months after the treatment. KOOS scores generally further increased with time until our last follow-up time points at 24 or 30 months.
Conclusion: Our findings demonstrated the compatibility of N-TEC with an OA environment, as it not only resisted, but also seemed to positively modulate the chronically inflamed joint environment. Our pre-clinical results indicated that implanted NC directly contribute to cartilage repair and engraftment in OA cartilage defects. To verify the regenerative capacity of N-TEC in patients, a suitably powered phase II clinical trial in a larger cohort of patients with OA is now required.
Mumme M, Barbero A, Miot S, Wixmerten A, Feliciano S, Wolf F, Asnaghi MA, Baumhoer D, Bieri O, Kretzschmar M, Pagenstert G, Haug M, Schaefer DJ, Martin I, Jakob M. Nasal chondrocytes-based engineered autologous cartilage tissue for the repair of articular cartilage defect: an observational first-in-human trial. Lancet 2016 Oct 22;388(10055):1985-1994. doi: 10.1016/S0140-6736(16)31658-0.
Acevedo L, Mumme M, Manferdini C, Darwiche S, Khalil A, Hilpert M, Buchner DA, Lisignoli G, Occhetta P, von Rechenberg B, Haug M, Schäfer D, Jakob M, Caplan A, Martin I, Barbero A, Pelttari K. Engineered nasal cartilage for the repair of osteoarthritic knee cartilage defects. Science Translational Medicine 2021 Sept;13(609). doi:10.1126/scitranslmed.aaz4499.
This project was supported by the Swiss National Science Foundation (310030_149614, PMPDP3_151396 and as part of the NCCR Molecular Systems Engineering SNSF 51NF40-141825), by Colombian Department of Science, Technology and Innovation (Colciencias), Burckhardt-Bürgin Foundation, Forschungsfond of the University of Basel, Swisslife and Deutsche Arthroseforschung.