Orchestrated biomechanical, structural, and biochemical stimuli for engineering anisotropic meniscus.

Reconstruction of the anisotropic structure and proper function of the knee meniscus remains an important challenge to overcome, because the complexity of the zonal tissue organization in the meniscus has important roles in load bearing and shock absorption. Current tissue engineering solutions for meniscus reconstruction have failed to achieve and maintain the proper function in vivo because they have generated homogeneous tissues, leading to long-term joint degeneration. To address this challenge, we applied biomechanical and biochemical stimuli to mesenchymal stem cells seeded into a biomimetic scaffold to induce spatial regulation of fibrochondrocyte differentiation, resulting in physiological anisotropy in the engineered meniscus. Using a customized dynamic tension-compression loading system in conjunction with two growth factors, we induced zonal, layer-specific expression of type I and type II collagens with similar structure and function to those present in the native meniscus tissue. Engineered meniscus demonstrated long-term chondroprotection of the knee joint in a rabbit model. This study simultaneously applied biomechanical, biochemical, and structural cues to achieve anisotropic reconstruction of the meniscus, demonstrating the utility of anisotropic engineered meniscus for long-term knee chondroprotection in vivo.

Characterization of human primary chondrocytes of osteoarthritic cartilage at varying severity.

BACKGROUND: There is a difficulty in evaluating the in vivo functionality of individual chondrocytes, and there is much heterogeneity among cartilage affected by osteoarthritis (OA). In this study, in vitro cultured chondrocytes harvested from varying stages of degeneration were studied as a projective model to further understand the pathogenesis of osteoarthritis. METHODS: Cartilage of varying degeneration of end-stage OA was harvested, while cell yield and matrix glycosaminoglycan (GAG) content were measured. Cell morphology, proliferation, and gene expression of collagen type I, II, and X, aggrecan, matrix metalloproteinase 13 (MMP-13), and ADAMTS5 of the acquired chondrocytes were measured during subsequent in vitro culture. RESULTS: Both the number of cells and the GAG content increased with increasing severity of OA. Cell spreading area increased and gradually showed spindle-like morphology during in vitro culture. Gene expression of collagen type II, collagen type X as well as GAG decreased with severity of cartilage degeneration, while expression of collagen type I increased. Expression of MMP-13 increased with severity of cartilage degeneration, while expression of ADAMTS-5 remained stable. Expression of collagen type II, X, GAG, and MMP-13 substantially decreased with in vitro culture. Expression of collagen type I increased with in vitro cultures, while expression of ADAMTS 5 remained stable. CONCLUSIONS: Expression of functional genes such as collagen type II and GAG decreased during severe degeneration of OA cartilage and in vitro dedifferentiation. Gene expression of collagen I and MMP-13 increased with severity of cartilage degeneration.

[Aggrecanases and osteoarthritis].

Osteoarthritis is mainly caused by the degenerative changes of cartilage and cartilage extracellular matrix, while Aggrecanases degradate Proteoglycans which are the major components of cartilage. This review includes three aspects: (1) We have concluded the major enzymes(ADAMTS-4 and ADAMTS-5) which regulate the metabolism of cartilage extracellular matrix. Meanwhile, we have summarized the structure of aggrecanases(ADAMTS-4 and ADAMTS-5) and introduced the function of each regional structure; (2) We have concluded the way cytokines and glycosaminoglycans regulate the metabolism of aggrecanases, and discussed the regulation and control principle of cytokines and glycosaminoglycan; (3) We have summarized the majority of inhibitors to the aggrecanases, introduced the endogenic inhibitors, and put our emphasis on the extrinsic inhibitors (chelating agents, polypeptides and so on). Through deeper research on the enzymes, it will help us further understand the pathogenesis of osteoarthritis, and open up new avenues to clinical treatment.