Hyaline Cartilage Microtissues Engineered from Adult Dedifferentiated Chondrocytes: Safety and Role of WNT Signaling

Latest Advances in Chondrocyte-Based Cartilage Repair

Chondrocyte-based cell therapy has been used for more than 30 years and is still considered to be a promising method of cartilage repair despite some limitations. This review introduces the latest developments of four generations of autologous chondrocyte implantation and current autologous chondrocyte products. The regeneration of cartilage from adult chondrocytes is limited by culture-induced dedifferentiation and patient age. Cartibeads is an innovative three-step method to produce high-quality hyaline cartilage microtissues, and it is developed from adult dedifferentiated chondrocytes with a high number of cell passages. In addition, allogeneic chondrocyte therapies using the Quantum hollow-fiber bioreactor and several signaling pathways involved in chondrocyte-based cartilage repair are mentioned, such as WNT signaling, the BMP-2/WISP1 pathway, and the FGF19 pathway.

Research Progress in Hydrogels for Cartilage Organoids

The repair and regeneration of cartilage has always been a hot topic in medical research. Cartilage organoids (CORGs) are special cartilage tissue created using tissue engineering techniques outside the body. These engineered organoids tissues provide models that simulate the complex biological functions of cartilage, opening new possibilities for cartilage regenerative medicine and treatment strategies. However, it is crucial to establish suitable matrix scaffolds for the cultivation of CORGs. In recent years, utilizing hydrogel to culture stem cells and induce their differentiation into chondrocytes has emerged as a promising method for the in vitro construction of CORGs. In this review, the methods for establishing CORGs are summarized and an overview of the advantages and limitations of using matrigel in the cultivation of such organoids is provided. Furthermore, the importance of cartilage tissue ECM and alternative hydrogel substitutes for Matrigel, such as alginate, peptides, silk fibroin, and DNA derivatives is discussed, and the pros and cons of using these hydrogels for the cultivation of CORGs are outlined. Finally, the challenges and future directions in hydrogel research for CORGs are discussed. It is hoped that this article provides valuable references for the design and development of hydrogels for CORGs.

Collagen and Alginate Hydrogels Support Chondrocytes Redifferentiation In Vitro without Supplementation of Exogenous Growth Factors

Focal cartilage defects are a prevalent knee problem affecting people of all ages. Articular cartilage (AC) possesses limited healing potential, and osteochondral defects can lead to pain and long-term complications such as osteoarthritis. Autologous chondrocyte implantation (ACI) has been a successful surgical approach for repairing osteochondral defects over the past two decades. However, a major drawback of ACI is the dedifferentiation of chondrocytes during their in vitro expansion. In this study, we isolated ovine chondrocytes and cultured them in a two-dimensional environment for ACI procedures. We hypothesized that 3D scaffolds would support the cells' redifferentiation without the need for growth factors so we encapsulated them into soft collagen and alginate (col/alg) hydrogels. Chondrocytes embedded into the hydrogels were viable and proliferated. After 7 days, they regained their original rounded morphology (aspect ratio 1.08) and started to aggregate. Gene expression studies showed an upregulation of COL2A1, FOXO3A, FOXO1, ACAN, and COL6A1 (37, 1.13, 22, 1123, and 1.08-fold change expression, respectively) as early as day one. At 21 days, chondrocytes had extensively colonized the hydrogel, forming large cell clusters. They started to replace the degrading scaffold by depositing collagen II and aggrecan, but with limited collagen type I deposition. This approach allows us to overcome the limitations of current approaches such as the dedifferentiation occurring in 2D in vitro expansion and the necrotic formation in spheroids. Further studies are warranted to assess long-term ECM deposition and integration with native cartilage. Though limitations exist, this study suggests a promising avenue for cartilage repair with col/alg hydrogel scaffolds.

Impact of local delivery of allogeneic chondrocytes on the biological response and healing of the sternum bones after sternotomy

Median sternotomy is the surgical method of choice for many procedures where one of the main problems is the long post-operative wound healing process leading to sternal dehiscence and the development of infection. This leads to prolonged hospital stay and increased mortality due to post-operative complications. A promising solution seems to be the use of allogeneic chondrocytes for wound treatment, whose properties in the field of cartilage reconstruction are widely used in medicine, mainly in orthopedics. In the present study, we investigated the effect of local delivery of allogeneic chondrocytes on the biological response and healing of the sternum after sternotomy. We optimized the culture conditions for the isolated chondrocytes, which were then applied to the sternal incision wound. Chondrocytes in the culture were assessed on the basis of the presence of chondrocyte-specific genes: Sox9, Aggrecan and Collagen II. In turn, the histopathological and immunohistochemical evaluation was used to assess the safety of implantation. In our work, we demonstrated the possibility of obtaining a viable culture of chondrocytes, which were successfully introduced into the sternal wound after sternotomy. Importantly, implantation of allogeneic chondrocytes showed no significant side effects. The obtained results open new possibilities for research on the use of allogeneic chondrocytes in the process of accelerating wound healing after median sternotomy.

Bone/cartilage organoid on-chip: Construction strategy and application

The necessity of disease models for bone/cartilage related disorders is well-recognized, but the barrier between ex-vivo cell culture, animal models and the real human body has been pending for decades. The organoid-on-a-chip technique showed opportunity to revolutionize basic research and drug screening for diseases like osteoporosis and arthritis. The bone/cartilage organoid on-chip (BCoC) system is a novel platform of multi-tissue which faithfully emulate the essential elements, biologic functions and pathophysiological response under real circumstances. In this review, we propose the concept of BCoC platform, summarize the basic modules and current efforts to orchestrate them on a single microfluidic system. Current disease models, unsolved problems and future challenging are also discussed, the aim should be a deeper understanding of diseases, and ultimate realization of generic ex-vivo tools for further therapeutic strategies of pathological conditions.

Role of Wnt signaling pathway in joint development and cartilage degeneration

Osteoarthritis (OA) is a prevalent musculoskeletal disease that affects approximately 500 million people worldwide. Unfortunately, there is currently no effective treatment available to stop or delay the degenerative progression of joint disease. Wnt signaling pathways play fundamental roles in the regulation of growth, development, and homeostasis of articular cartilage. This review aims to summarize the role of Wnt pathways in joint development during embryonic stages and in cartilage maintenance throughout adult life. Specifically, we focus on aberrant mechanical loading and inflammation as major players in OA progression. Excessive mechanical load activates Wnt pathway in chondrocytes, resulting in chondrocyte apoptosis, matrix destruction and other osteoarthritis-related changes. Additionally, we discuss emerging Wnt-related modulators and present an overview of emerging treatments of OA targeting Wnt signaling. Ultimately, this review provides valuable insights towards discovering new drugs or gene therapies targeting Wnt signaling pathway for diagnosing and treating osteoarthritis and other degenerative joint diseases.