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Aims This study aimed to investigate whether human umbilical cord mesenchymal stem cells (UC-MSCs) can prevent articular cartilage degradation and explore the underlying mechanisms in a rat osteoarthritis (OA) model induced by monosodium iodoacetate (MIA). Methods Human UC-MSCs were characterized by their phenotype and multilineage differentiation potential. Two weeks after MIA induction in rats, human UC-MSCs were intra-articularly injected once a week for three weeks. The therapeutic effect of human UC-MSCs was evaluated by haematoxylin and eosin, toluidine blue, Safranin-O/Fast green staining, and Mankin scores. Markers of joint cartilage injury and pro- and anti-inflammatory markers were detected by immunohistochemistry. Results Histopathological analysis showed that intra-articular injection of human UC-MSCs significantly inhibited the progression of OA, as demonstrated by reduced cartilage degradation, increased Safranin-O staining, and lower Mankin scores. Immunohistochemistry showed that human UC-MSC treatment down-regulated the expression of matrix metalloproteinase-13 (MMP13) and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5), and enhanced the expression of type II collagen and ki67 in the articular cartilage. Furthermore, human UC-MSCs significantly decreased the expression of interleukin (IL)-1β and tumour necrosis factor-α (TNF-α), while increasing TNF-α-induced protein 6 and IL-1 receptor antagonist. Conclusion Our results demonstrated that human UC-MSCs ameliorate MIA-induced OA by preventing cartilage degradation, restoring the proliferation of chondrocytes, and inhibiting the inflammatory response, which implies that human UC-MSCs may be a promising strategy for the treatment of OA. Cite this article: Bone Joint Res 2021;10(3):226–236.

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To take full advantages of high-strength concrete (HSC) and steel fiber reinforced full-lightweight concrete (SFRFLC), a new type of composite beams was suggested, which was cast by HSC superposed on SFRFLC in certain relative depths. Based on the tests of 13 reinforced HSC (in strength grades of C60 and C70)-on-SFRFLC (in strength grades of LC30) superposed beams comparing with 4 reinforced concrete beams, and by using the crack pattern classification analyzing method, this paper studies the regularity of main cross-sectional crack distribution affected by the longitudinal tensile reinforcement ratio, the fraction of steel fiber by volume and the sectional depth of SFRFLC. The methods are determined for the calculation of the height of effective tensile cracked area and the stress of longitudinal tensile rebar considering the loading performance of SFRFLC. The formulas for calculating the crack space and crack width of reinforced HSC-on-SFRFLC superposed beams are suggested.