Background/Purpose: There is controversy about the effect of catabolic cytokines in regenerative medicine. The purpose of this study was to evaluate the effect of interleukin 1β (IL1β) in the repair capacity of bone marrow mesenchymal stromal cells (BMSCs) seeded on collagen (Col)/proteoglycan (PG) scaffolds, in an in vitro cartilage lesion model.

Methods: Samples were obtained from hips (BMSCs and cartilage) and knees (only cartilage) of patients who underwent total joint replacement. 3 mm-diameter lesions were made in cartilage biopsies using a dental drill. Injured biopsies were pre-treated with 10 ng/ml of IL1β for 24 hours. 2×10⁵ BMSCs were seeded on type I and II Col with heparan sulfate (C1C2HS), and C1C2 with chondroitin sulfate (C1C2CHS) scaffolds.  Resulting constructs were introduced inside the lesion and cultured for 60 days in chondrogenic medium. Controls without IL1β pre-treatment were performed. Histological analyses were made and repaired tissue was evaluated using the International Cartilage Research Society scale II (ICRSII) [1].

Results: In the IL1β pre-treated model, Hematoxilin-Eosin staining (HE, Figure) showed neotissue formation within the lesion with fewer rounded cells than in the non pre-treated model. Staining with Masson’s Thrichrome (MT, Figure) showed the presence of Col in the extracellular matrix (ECM) of all the constructs. The presence of PGs detected by Safranin O (SO, Figure) staining was more metachromatic in non pre-treated C1C2HS (52.426±4.877) and C1C2CHS (32.722±8.781) constructs than in IL1β pre-treated C1C2HS (20.973±6.849) and C1C2CHS (23.228±1.704) ones.

By ICRS II assessment of the non-pretreated model, the repair score for C1C2CHS was 46% (fibrocartilage neotissue), and 73% (mixed fibrocartilage and hyaline cartilage) for C1C2HS constructs. In the IL1β pre-treated model, morphological changes with the loss of ECM components observed by SO and MT staining resulted in lowering of the ICRSII scores.

Conclusion: In absence of IL1β, BMSCs seeded on Col and PG scaffolds showed higher in vitro cartilage repair capacity than in the IL1β pre-treated model. References: [1]. Mainil-Varlet P, et al. Am J Sports Med. 2010;38(5):880-90. Acknowledgements: Opocrin S.P.A.; CAM (S2009/MAT-1472); REDICENT and GPC (R2014/050 and GPC2014/048), Xunta de Galicia; MINECO-FEDER (RTC-2016-5386-1); CIBER-BBN; Fund. Española de Reumatología (2014 grant); Fund. Profesor Novoa Santos; Diputación da Coruña; Universidade da Coruña.