Cartilage defects caused by joint diseases are difficult to treat clinically. Tissue engineering materials provide a new means to promote the repair of cartilage defects. The purpose of this study is to design a novel scaffold of porous magnesium alloy loaded with icariin and sustained release in order to explore the effect and possible mechanism of this scaffold in repairing SD rat knee articular cartilage defect. We constructed a novel type of icariin/porous magnesium alloy scaffold, observed the structure of the scaffold by electron microscope, detected the drug release of icariin in the scaffold and the biological safety, and established an animal model of cartilage defect in the femoral intercondylar fossa of the knee joint in rats; the scaffold was placed in the defect. After 12 weeks of repair, the rat knee articular cartilage repair was evaluated by gross specimens and micro-CT, HE, safranin O-fast green, and toluidine blue staining combined with the modified Mankin\'s score. The protein expressions of the Wnt/β-catenin signaling pathway-related factors (β-catenin, Wnt5a, Wnt1, sFRP1) and chondrogenic differentiation-related factors (Sox9, Aggrecan, Col2α1) were detected by immunohistochemical staining. We found that the novel scaffold of icariin/porous magnesium alloy can release icariin slowly and has biosafety in rats. Compared with other groups, icariin/porous magnesium alloy can significantly promote the repair of cartilage defects and the expressions of β-catenin, Wnt5a, Wnt1, Sox9, Aggrecan, and Col2α1 (P < 0.05). This novel scaffold can promote the repair of rat knee cartilage defects, and this process may be achieved by activating the Wnt/β-catenin signaling pathway.

Articular cartilage defect is challenged by insufficient regenerative ability of cartilage. Catalpol (CA), the primary active component of Rehmanniae Radix, could exert protective effects against various diseases. However, the impact of CA on the treatment of articular cartilage injuries is still unclear. In this study, full-thickness articular cartilage defect was induced in a mouse model via surgery. The animals were intraperitoneally injected with CA for 4 or 8 weeks. According to the results of macroscopic observation, micro-computed tomography CT (μCT), histological and immunohistochemistry staining, CA treatment could promote mouse cartilage repair, resulting in cartilage regeneration, bone structure improvement and matrix anabolism. Specifically, an increase in the expression of CD90, the marker of mesenchymal stem cells (MSCs), in the cartilage was observed. In addition, we evaluated the migratory and chondrogenic effects of CA on MSCs. Different concentration of CA was added to C3H10 T1/2 cells. The results showed that CA enhanced cell migration and chondrogenesis without affecting proliferation. Collectively, our findings indicate that CA may be effective for the treatment of cartilage defects via stimulation of endogenous MSCs.

There has been increasing application of autologous costal chondral/osteochondral transplantation (ACCT/ACOT) and costa-derived chondrocyte implantation (ACCI) for articular cartilage repair over the past three decades. This review presents the major evidence on the properties of costal cartilage and bone and their qualifications as grafts for articular cartilage repair, the major clinical applications, and the risks and strategies for costal chondral/osteochondral graft(s) harvest. First, costal cartilage has many specific properties that help restore the articular surface. Costa, which can provide abundant cartilage and cylindrical corticocancellous bone, preserves permanent chondrocyte and is the largest source of hyaline cartilage. Second, in the past three decades, autologous costal cartilage-derived grafts, including cartilage, osteochondral graft(s), and chondrocyte, have expanded their indications in trauma and orthopaedic therapy from small to large joints, from the upper to lower limbs, and from non-weight-bearing to weight-bearing joints. Third, the rate of donor-site complications of ACCT or ACOT is low, acceptable, and controllable, and some skills and accumulated experience can help reduce the risks of ACCT and ACOT. Costal cartilage-derived autografting is a promising technique and could be an ideal option for articular chondral lesions with or without subchondral cysts. More high-quality clinical studies are urgently needed to help us further understand the clinical value of such technologies.

Cytotherapies are often necessary for the management of symptomatic large knee (osteo)-chondral defects. While autologous chondrocyte implantation (ACI) has been clinically used for 30 years, allogeneic cells (clinical-grade FE002 primary chondroprogenitors) have been investigated in translational settings (Swiss progenitor cell transplantation program). The aim of this study was to comparatively assess autologous and allogeneic approaches (quality, safety, functional attributes) to cell-based knee chondrotherapies developed for clinical use. Protocol benchmarking from a manufacturing process and control viewpoint enabled us to highlight the respective advantages and risks. Safety data (telomerase and soft agarose colony formation assays, high passage cell senescence) and risk analyses were reported for the allogeneic FE002 cellular active substance in preparation for an autologous to allogeneic clinical protocol transposition. Validation results on autologous bioengineered grafts (autologous chondrocyte-bearing Chondro-Gide scaffolds) confirmed significant chondrogenic induction (COL2 and ACAN upregulation, extracellular matrix synthesis) after 2 weeks of co-culture. Allogeneic grafts (bearing FE002 primary chondroprogenitors) displayed comparable endpoint quality and functionality attributes. Parameters of translational relevance (transport medium, finished product suturability) were validated for the allogeneic protocol. Notably, the process-based benchmarking of both approaches highlighted the key advantages of allogeneic FE002 cell-bearing grafts (reduced cellular variability, enhanced process standardization, rationalized logistical and clinical pathways). Overall, this study built on our robust knowledge and local experience with ACI (long-term safety and efficacy), setting an appropriate standard for further clinical investigations into allogeneic progenitor cell-based orthopedic protocols.

OBJECTIVE: Osteochondral lesions of the talus (OLT) is a common and clinically challenging disease. The optimal management is still under debate. The purpose of this prospective study was to investigate the feasibility and clinical outcomes of autologous costal osteochondral transplantation (ACOT) for the treatment of cystic OLT.
METHODS: From November 2021 to April 2023, five patients underwent autologous costal osteochondral transplantation (ACOT) for cystic OLT. The demographic data was described, including age, gender, lesion size and location. We prospectively evaluated their functional and imaging outcomes of the five patients for 12 months postoperatively, including numeric rating score (NRS) for pain when walking, Tegner score, American Orthopedic Foot & Ankle Society (AOFAS) score and Foot and Ankle Ability Measure (FAAM) score, and imaging results. A paired t-test was used for preoperative and postoperative comparison of the paired-design dataset.
RESULTS: The average age was 36.6 ± 11.1 years. The average diameter of chondral lesions was 14.95 ± 2.71 mm, the average diameter of subchondral cysts was 10.66 ± 1.84 mm, and their average depth was 10.40 ± 1.86 mm. At 12 months postoperatively, the clinical function indexes improved significantly, including NRS (from 5.2 ± 2.3 to 0), Tegner score (from 3.2 ± 0.4 to 5.8 ± 0.4), AOFAS score (from 72.8 ± 10.0 to 98.2 ± 4.0), and FAAM score (FAAM/ADL from 61.2 ± 24.7 to 99.3 ± 1.6; FAAM/Sports from 32.5 ± 13.73 to 96.3 ± 8.4). Their magnetic resonance observation of cartilage repair tissue (MOCART) scores reached 78.0 ± 7.6 points. ICRS scores of three patients were nearly normal (10 or 11 points). The biopsy of the surviving grafts showed plenty of hyaline cartilage matrix and scattered chondrocytes histologically. No major severe complications were reported during the 12 months follow-up.
CONCLUSIONS: ACOT could significantly relieve the symptoms of patients with OLT and improve their clinical function at short-term follow-up. ACOT might be a feasible and useful method for repairing OLT with subchondral cysts.

OBJECTIVE: To provide an overview of the incidence of knee donor -site morbidity after autologous osteochondral mosaicplasty.
METHODS: A comprehensive search was conducted in PubMed, EMbase, Wanfang Medical Network, and CNKI databases from January 2010 to April 20, 2021. Relevant literature was selected based on predefined inclusion and exclusion criteria, and data were evaluated and extracted. The correlation between the number and size of transplanted osteochondral columns and donor-site morbidity was analyzed.
RESULTS: A total of 13 literatures were included, comprising a total of 661 patients. Statistical analysis revealed an incidence of knee donor-site morbidity at 8.6% (57/661), with knee pain being the most common complaint, accounting for 4.2%(28/661). There was no significant correlation between the number of osteochondral columns and postoperative donor-site incidence (P=0.424, N=10), nor between the diameter size of osteochondral columns and postoperative donor-site incidence(P=0.699, N=7).
CONCLUSIONS: Autologous osteochondral mosaicplasty is associated with a considerable incidence of knee donor-site morbidity, with knee pain being the most frequent complaint. There is no apparent correlation between donor-site incidence and the number and size of transplanted osteochondral columns. Donors should be informed about the potential risks.

OBJECTIVE: To describe associations between MRI markers with knee symptoms in young adults.
METHODS: Knee symptoms were assessed using the WOMAC scale during the Childhood Determinants of Adult Health Knee Cartilage study (CDAH-knee; 2008-2010) and at the 6- to 9-year follow-up (CDAH-3; 2014-2019). Knee MRI scans obtained at baseline were assessed for morphological markers (cartilage volume, cartilage thickness, subchondral bone area) and structural abnormalities [cartilage defects and bone marrow lesions (BMLs)]. Univariable and multivariable (age, sex, BMI adjusted) zero-inflated Poisson (ZIP) regression models were used for analysis.
RESULTS: The participants\' mean age in CDAH-knee and CDAH-3 were 34.95 (s.d. 2.72) and 43.27 (s.d. 3.28) years, with 49% and 48% females, respectively. Cross-sectionally, there was a weak but significant negative association between medial femorotibial compartment (MFTC) [ratio of the mean (RoM) 0.99971084 (95% CI 0.9995525, 0.99986921), P < 0.001], lateral femorotibial compartment (LFTC) [RoM 0.99982602 (95% CI 0.99969915, 0.9999529), P = 0.007] and patellar cartilage volume [RoM 0.99981722 (95% CI 0.99965326, 0.9999811), P = 0.029] with knee symptoms. Similarly, there was a negative association between patellar cartilage volume [RoM 0.99975523 (95% CI 0.99961427, 0.99989621), P = 0.014], MFTC cartilage thickness [RoM 0.72090775 (95% CI 0.59481806, 0.87372596), P = 0.001] and knee symptoms assessed after 6-9 years. The total bone area was negatively associated with knee symptoms at baseline [RoM 0.9210485 (95% CI 0.8939677, 0.9489496), P < 0.001] and 6-9 years [RoM 0.9588811 (95% CI 0.9313379, 0.9872388), P = 0.005]. The cartilage defects and BMLs were associated with greater knee symptoms at baseline and 6-9 years.
CONCLUSIONS: BMLs and cartilage defects were positively associated with knee symptoms, whereas cartilage volume and thickness at MFTC and total bone area were weakly and negatively associated with knee symptoms. These results suggest that the quantitative and semiquantitative MRI markers can be explored as a marker of clinical progression of OA in young adults.

Mechano growth factor (MGF), an isoform of insulin-like growth factor 1 (IGF-1), is recognized as a typical mechanically sensitive growth factor and has been shown to play an indispensable role in the skeletal system. In the joint cavity, MGF is highly expressed in chondrocytes, especially in the damaged cartilage tissue caused by trauma or degenerative diseases such as osteoarthritis (OA). Cartilage is an extremely important component of joints because it functions as a shock absorber and load distributer at the weight-bearing interfaces in the joint cavity, but it can hardly be repaired once injured due to its lack of blood vessels, lymphatic vessels, and nerves. MGF has been proven to play an important role in chondrocyte behaviors, including cell proliferation, migration, differentiation, inflammatory reactions and apoptosis, in and around the injury site. Moreover, under the normalized mechanical microenvironment in the joint cavity, MGF can sense and respond to mechanical stimuli, regulate chondrocyte activity, and maintain the homeostasis of cartilage tissue. Recent reports continue to explain its effects on various cell types and sport-related tissues, but its role in cartilage development, homeostasis and disease occurrence is still controversial, and its internal biological mechanism is still elusive. In this review, we summarize recent discoveries on the role of MGF in chondrocytes and cartilage defects, including tissue repair at the macroscopic level and chondrocyte activities at the microcosmic level, and discuss the current state of research and potential gaps in knowledge.

BACKGROUND: Autogenous osteochondral mosaicplasty (AOM) is a widely used optimal surgical technique for cartilage repair in young patients with focal articular cartilage defects. However, the alterations in balance control in these patients after AOM have not been sufficiently investigated. This study aimed to compare different balance control performances between the patients with knee cartilage defects and healthy controls before and after AOM, as well as evaluate the influence of AOM on balance control in these patients.
METHODS: Static posturographic tests were performed in twenty-four patients who were scheduled for AOM two weeks pre-, three months, and one year postoperatively, along with thirty matched controls, respectively. All participants underwent posturography under four standing conditions: eyes open and closed, without and with foam support to assess the balance control ability. Subsequently, patient-reported outcome measures (PROMs) were synchronously obtained and analyzed.
RESULTS: Compared to the control subjects, less efficient balance control was observed in study patients at three testing phases (p < 0.05), whereas no alterations in postural control were visible in these patients within a year following AOM (p > 0.05). Significant improvements were found in all PROMs such as the International Knee Documentation Committee, the Lysholm Knee Score, and the visual analogue scale in the study patients postoperatively (p < 0.01).
CONCLUSIONS: The results indicated that patients with knee cartilage defects have a prominent balance control deficit compared to healthy individuals. Furthermore, AOM does not improve balance control in these patients for at least one year postoperatively, and more effective approaches for postural regulation are required for the management of cartilage defect patients.

Cartilage injury affects numerous individuals, but the efficient repair of damaged cartilage is still a problem in clinic. Hydrogel is a potent scaffold candidate for tissue regeneration, but it remains a big challenge to improve its mechanical property and figure out the interaction of chondrocytes and stiffness. Herein, a novel hybrid hydrogel with tunable stiffness was fabricated based on methacrylated gelatin (GelMA) and iron oxide nanoparticles (Fe2O3) through chemical bonding. The stiffness of Fe2O3/GelMA hybrid hydrogel was controlled by adjusting the concentration of magnetic nanoparticles. The hydrogel platform with tunable stiffness modulated its cellular properties including cell morphology, microfilaments and Young\'s modulus of chondrocytes. Interestingly, Fe2O3/GelMA hybrid hydrogel promoted oxidative phosphorylation of mitochondria and facilitated catabolism of lipids in chondrocytes. As a result, more ATP and metabolic materials generated for cellular physiological activities and organelle component replacements in hybrid hydrogel group compared to pure GelMA hydrogel. Furthermore, implantation of Fe2O3/GelMA hybrid hydrogel in the cartilage defect rat model verified its remodeling potential. This study provides a deep understanding of the bio-mechanism of Fe2O3/GelMA hybrid hydrogel interaction with chondrocytes and indicates the hydrogel platform for further application in tissue engineering.