Search Results (72)

Purpose: To determine whether specific in vitro biologic characteristics and manufacturing kinetics of cultured human articular chondrocytes (HACs) can serve as predictive biomarkers for patient-reported and structural outcomes following second-generation autologous chondrocyte implantation (ACI) in the knee. Materials and Methods: This prospective cohort study evaluated 67 patients (mean age 25.1 ± 8.3 years) treated with second-generation ACI for large focal cartilage defects (mean size 5.4 ± 2.5 cm²) between 2017 and 2024. HACs were expanded under Good Manufacturing Practice (GMP) conditions using human platelet lysate-supplemented media. Four biological determinants were analyzed: (1) initial chondrocyte yield (ICY) isolated from the cartilage biopsy; (2) chondrogenic activity (relative ACAN and COL2A1 expression); (3) final culture confluence level; and (4) HAC population doubling time (PDT) pre- and post-cryopreservation. Clinical outcomes (KOOS and IKDC) and MRI outcomes (MOCART) were assessed at 2 years (T1) and at a mean final follow-up of 4.2 ± 1.7 years (T2) via univariate and multiple regression analyses. Results: Static biosynthetic markers (ACAN/COL2A1 expression) and final culture confluence did not significantly correlate with longitudinal clinical (KOOS/IKDC) or structural (MOCART) outcomes. Conversely, the retained kinetic parameters served as strong prognostic indicators. Multiple regression revealed that higher ICY values significantly predicted improvements across most KOOS subscales from baseline to T2, including KOOS Symptoms (β = 63.56; p < 0.01), KOOS Pain (β = 88.83; p < 0.001), KOOS ADL (β = 107.84; p < 0.001), and KOOS Sport and Recreation Function (β = 92.3; p < 0.05). Furthermore, a prolonged PDT, indicative of diminished in vitro proliferative vigor, inversely correlated with functional recovery in IKDC (β = −26.12; p < 0.01), KOOS Pain (β = −23.09; p < 0.05), and KOOS ADL (β = −21.71; p < 0.05) scores. Conclusions: The intrinsic proliferative vigor of the HAC cellular payload (shorter PDT) and higher initial cell yields are robust kinetic biomarkers associated with markedly superior mid-term clinical outcomes following second-generation ACI for large focal chondral defects in the knee. In contrast, standard morphological and gene expression metrics failed to predict in vivo functional success. These findings advocate for a risk-based paradigm shift in GMP quality control methodologies, emphasizing dynamic HAC growth kinetics over static cellular features to optimize patient-specific regenerative potential. Full article

Articular cartilage possesses a limited intrinsic repair capacity, and current treatment strategies frequently result in fibrocartilaginous repair tissue with inferior structural and mechanical properties compared with native hyaline cartilage. Increasing evidence indicates that successful restoration of joint function requires regeneration of the entire osteochondral unit and adequate integration between cartilage and subchondral bone. Cartilage tissue engineering has emerged as an effective approach for repairing damaged cartilage. The present study evaluated the long-term performance of electrospun PLA/PCL (70/30) scaffolds coated with iodine-doped polypyrrole (PPy-I), with and without aggrecan incorporation, in a rabbit osteochondral defect model after 12 months of implantation. Two scaffold formulations were evaluated: M1 (PLA-PCL-PPy-I) and M2 (PLA-PCL-PPy-I-AG), each implanted either without cells or after in vitro pre-culture with autologous chondrocytes prior to implantation. Histological analyses were performed to assess tissue organization and osteochondral integration, while indentation testing was used to characterize the mechanical behavior of the regenerated tissues. Experimental force–displacement data were further analyzed using a generalized nonlinear Maxwell viscoelastic model. Histological evaluation revealed that scaffold composition and cellularization influenced the characteristics of the regenerated tissue. The M2 scaffold pre-cultured with autologous chondrocytes exhibited the structural organization most closely resembling native hyaline cartilage, including a tri-zonal architecture and a continuous tidemark indicative of improved osteochondral integration. Mechanical testing demonstrated nonlinear viscoelastic behavior and hysteresis in both regenerated and native tissues. The proposed generalized nonlinear Maxwell viscoelastic model provides a practical framework for the mechanical characterization of regenerated osteochondral tissues using only two effective parameters representing the elastic and viscous response, and may support future studies aimed at estimating their intrinsic mechanical properties. Full article

Osteoarthritis is a leading cause of disability, most commonly affecting the articular cartilage of the knee in older individuals. Younger people are also at risk of developing post-traumatic osteoarthritis, including athletes and those with a history of joint injury. Focal cartilage defects can be treated through clinical interventions such as autologous chondrocyte implantation, where cells from the patient are isolated, cultured, and subsequently reimplanted into the defect site. Despite recent clinical advances, there is a lack of standardisation in the preparation of chondrocytes for cartilage tissue engineering therapies, with considerable variation in culture conditions reported in the literature. A major challenge in cell-based cartilage repair is the dedifferentiation of chondrocytes during monolayer expansion, which leads to a change in phenotype. Native articular chondrocytes exhibit a rounded morphology and express collagen type II and aggrecan, whilst dedifferentiated cells adopt a fibroblastic phenotype, characterised by an elongated morphology and increased expression of collagen type I. This review summarises the key physical, biochemical, and mechanical factors that mitigate chondrocyte dedifferentiation to support the maintenance of a chondrogenic phenotype and preserve the capacity of cells to redifferentiate. A mechanistically informed approach to chondrocyte culture will enhance cartilage tissue engineering therapies. Full article

Focal articular cartilage defects retain limited intrinsic repair capacity owing to the avascular, alymphatic and aneural nature of hyaline cartilage. Marrow-stimulation procedures often generate mechanically inferior fibrocartilage with declining benefit within 2–5 years in larger or high-demand lesions, while matrix-induced autologous chondrocyte implantation (MACI) achieves durable 10-year benefit but remains constrained by two-stage logistics, in vitro dedifferentiation and cost. This review integrates the cellular, biomaterial, biochemical and immunological dimensions of articular cartilage tissue engineering with quantitative benchmarks and a critical reading of failure modes, scalability and regulatory standing. We benchmark MACI against single-stage chondron- and progenitor-based therapies; examine mesenchymal stromal cells (MSCs) from bone marrow, adipose, synovium and the infrapatellar fat pad with a mechanistic dissection of the Wnt/β-catenin, IHH–PTHrP, RUNX2/MEF2C and HIF-1α inputs driving hypertrophic drift; reframe scaffolds as bioinstructive environments delivering mechanical, biochemical and tribological cues, including stimuli-responsive and 4D-printed systems and low-intensity pulsed ultrasound (LIPUS) as a non-invasive adjunct; develop the immunological dialogue between altered native cartilage, the infrapatellar fat pad–synovium unit and engineered constructs; and appraise CRISPR-based cell engineering and artificial-intelligence applications in biofabrication. We classify the principal approaches into four explicit translational tiers so that the evidentiary standing of each strategy is transparent. Translation will be paced by standardised potency assays, immune-aware construct design and robust long-term in vivo evidence. Full article

Articular cartilage defects affect millions of patients annually and pose one of the most persistent challenges in orthopedic surgery, owing to the tissue’s inherent avascular and alymphatic nature. Current surgical approaches, microfracture, autologous chondrocyte implantation (ACI/MACI), and osteochondral grafting, share a common failure mode: inadequate adhesion between repair constructs and surrounding native cartilage, contributing to deterioration rates of 15–75% at five-year follow-up across all techniques. This review repositions adhesion not as a supplementary material property but as the central determinant of clinical success in cartilage repair. We systematically evaluate the biomechanical demands imposed by the joint environment and define clinically relevant adhesion thresholds. Adhesive hydrogel strategies are categorized by surgical context: microfracture augmentation, ACI/MACI enhancement, osteochondral graft integration, and standalone repair platforms. Material platforms are analyzed across catechol/dopamine systems, NHS ester chemistry, photocrosslinkable hydrogels, supramolecular approaches, and multi-mechanism hybrids. Injectable formulations for arthroscopic delivery are critically examined alongside key translational barriers, including fatigue durability, biocompatibility–adhesion trade-offs, sterilization compatibility, batch variability, and regulatory classification ambiguity. Future directions encompass 4D bioprinting, AI-guided formulation optimization, and stimuli-responsive reversible adhesion systems. Adhesive hydrogels represent the missing link that current cartilage repair paradigms require. Full article

Objectives: To evaluate the effectiveness and durability of matrix-associated autologous chondrocyte implantation with periosteal flap (pMACI) in treating knee cartilage defects using clinical scores and MRI evaluations. Methods: Data were collected from 37 knees of 17 patients, with a mean follow-up of 5 years (range: 0.1–20 years). Clinical outcomes were assessed using the Lysholm Knee Scoring Scale (LKS) and Knee Injury and Osteoarthritis Outcome Score (KOOS). Tissue quality was quantitatively evaluated using MRI T1ρ and T2 mapping (biochemical) and MR observation of cartilage repair tissue: MOCART 2.0 (morphological). A linear mixed model was used to identify factors affecting outcomes, including etiology (trauma, OCD, OA), graft site, and defect size. Results: At the 20-year follow-up, clinical scores remained significantly improved from baseline (mean LKS: 55.6 to 86.5; KOOS: 37.8 to 70.8). The biochemical MRI parameters (T1ρ and T2 values) stabilized at levels comparable to native cartilage across all etiologies and sites (p = 0.326 and 0.412, respectively), indicating stable long-term tissue quality. In contrast, the MOCART 2.0 scores significantly declined over time (annual rate: −1.14 points; p < 0.001). Etiology was a significant factor; the OA group showed significantly lower clinical and MOCART scores compared to the trauma/OCD groups (p < 0.05). However, no significant differences were found in LKS and KOOS based on graft site (p = 0.489) or defect size (p > 0.05). Conclusions: pMACI may be a highly durable treatment capable of maintaining biological tissue quality and providing clinical benefits for two decades. The observed morphological deterioration after 20 years likely reflects joint-wide aging—especially in OA cases—rather than graft failure, highlighting the importance of long-term MRI monitoring. Full article

Articular cartilage has a limited capacity for self-repair, and effective strategies for its regeneration remain a major clinical challenge. Full-thickness cartilage defects extending to the subchondral bone induce an enhanced inflammatory response and impair spontaneous healing. This study aimed to evaluate the regenerative potential of autologous chondrocyte transplantation using an insoluble polyethersulfone (PES) scaffold in a rabbit model of grade III articular cartilage lesions. Chondrocytes were isolated and expanded in vitro and subsequently seeded onto PES membranes. Sixty-two rabbit knees with defects extending to the subchondral bone were divided into three groups: group I received chondrocyte-seeded PES scaffolds (n = 25), group II received cell-free PES scaffolds (n = 25), and group III served as an untreated control (n = 12). Cartilage regeneration was evaluated macroscopically and histologically over 52 weeks. In addition, the chondrogenic differentiation potential of cells cultured on PES scaffolds was assessed. This study extends our previous investigations of PES scaffolds in grade IV cartilage defects to a clinically relevant grade III lesion model, enabling evaluation of regenerative outcomes at an earlier stage of cartilage degeneration. The results demonstrated superior tissue regeneration in defects treated with chondrocyte-seeded PES scaffolds compared to both control groups. These findings indicate that synthetic PES scaffolds support cartilage repair and represent a promising biomaterial for the development of cell-based therapies in articular cartilage regeneration. Full article

Background/Objectives: The aim of this study is to evaluate whether preoperative intra-articular corticosteroid injections (CSIs) are associated with an increased risk of reoperation following matrix-associated or autologous chondrocyte implantation (MACI/ACI). Secondary aims included comparing reoperation-free survival, patient-reported outcomes (PROMs), and patient acceptable symptom state (PASS) achievement. Methods: A retrospective cohort study was conducted on adults undergoing primary MACI/ACI between 2011 and 2023 at a single academic institution. Patients with documented CSI status and ≥2 years of follow-up were included. Exclusion criteria were prior MACI/ACI, osteochondral allograft transplantation, multi-ligament reconstruction, or inadequate follow-up. Propensity score matching (2:1, no steroid/steroid) based on age, sex, BMI, laterality, procedure type, and prior surgery yielded 138 matched patients (92 no steroid, 48 steroid). The primary outcome was ipsilateral reoperation, analyzed as a binary outcome, with Kaplan–Meier reoperation-free survival and restricted mean survival time (RMST). PROMs and PASS achievement were also assessed. Statistical significance was set at p < 0.05. Results: Baseline characteristics and follow-up (6.55 ± 3.74 vs. 6.73 ± 3.99 years; p = 0.80) were similar. Graft failure rates were identical (4.3% each; p = 1.00). Reoperation occurred in 21.7% of patients without CSI and 23.9% with CSI (p = 0.83). CSI was not associated with reoperation (adjusted OR 2.28; 95% CI 0.54–9.95; p = 0.26). No significant difference in reoperation-free survival or PROMs was observed. Conclusions: Preoperative intra-articular corticosteroid injections were not associated with increased reoperation risk, inferior reoperation-free survival, or worse functional outcomes following MACI/ACI. Full article

Articular cartilage, a highly specialised and avascular tissue, exhibits limited regenerative potential following trauma or degenerative conditions such as osteoarthritis (OA). Conventional surgical interventions, including microfracture and autologous chondrocyte implantation (ACI), have shown limited long-term efficacy due to donor site morbidity and restricted cell proliferation. In this context, mesenchymal stromal cells (MSCs) have emerged as a promising alternative owing to their multipotency, self-renewal capacity, and low immunogenicity. While bone marrow (BM) remains the traditional source of MSCs, recent studies have reported that peripheral blood-derived mesenchymal stromal cells (PB-MSCs) may possess chondrogenic, osteogenic, and adipogenic potential comparable to that of BM-derived MSCs. PB-MSCs can be harvested through minimally invasive methods, thereby avoiding the complications associated with BM aspiration. Experimental evidence indicates that PB-MSCs exhibit strong cell viability, proliferative potential, and the ability to synthesise cartilage-specific extracellular matrix proteins, such as type II collagen and sulphated glycosaminoglycans, within three-dimensional scaffolds. Immunophenotypically, PB-MSCs express mesenchymal markers including CD29, CD44, CD90, and CD105 while lacking hematopoietic markers CD34 and CD45. Flow cytometry analyses reveal that CD105⁺ populations increase following cryopreservation, highlighting their clinical utility. In contrast to these experimentally defined PB-MSCs, the term peripheral blood stem cells (PBSCs) is used in clinical studies to describe heterogeneous, non-cultured peripheral blood-derived cell preparations, typically enriched in hematopoietic stem and progenitor cells following granulocyte colony-stimulating factor (G-CSF) mobilisation, without full mesenchymal characterisation. In vitro studies confirm successful tri-lineage differentiation, whereas in vivo investigations have demonstrated effective cartilage regeneration using PB-based clinical approaches, including postoperative intra-articular administration of hyaluronic acid (HA) combined with PBSCs, as well as implantation of PBSCs covered with a collagen membrane. Furthermore, advancements in biomaterial engineering, such as poly(ethylene glycol)–cysteine–arginine–glycine–aspartic acid (PEG-CRGD) hydrogels, have enhanced PB-MSC adhesion, proliferation, and chondrogenic differentiation while promoting immunomodulation through M2 macrophage polarisation. Despite these promising outcomes, the available evidence remains limited and heterogeneous, with substantial variability in cell definitions, experimental models, and clinical study designs, which currently constrains definitive conclusions regarding clinical efficacy. Future research should focus on optimising isolation protocols, understanding molecular pathways governing PB-MSC chondrogenesis, and standardising clinical applications. Overall, PB-MSCs represent a viable, less invasive, and translationally relevant cell source for cartilage regeneration and regenerative orthopaedic therapies Full article

Osteoarthritis (OA) is the most common joint disorder worldwide. Autologous chondrocyte implantation (ACI) is an established treatment for articular cartilage defects of the knee, but its effectiveness in OA is still under investigation. In this study, we investigated the effects of a newly developed mammalian-derived collagen matrix, NC-Col, on the proliferation, migration, adhesion, and gene expression of human articular cartilage-derived chondrocytes from OA patients in vitro, using proliferation assays, wound healing assays, adhesion assays, RT-qPCR, and RNA sequencing, respectively. In addition, the effects of NC-Col were compared with three different commercially available collagen matrices, and the underlying molecular mechanisms through which NC-Col influences these cellular behaviours were explored. Our results showed that NC-Col, used as a coating matrix, enhances cell proliferation, maintains the phenotype, and upregulates Proteoglycan 4 (PRG4) in human articular cartilage-derived chondrocytes. Inhibition of the PI3K-Akt signalling pathway was found to be involved in some of these effects. In conclusion, our findings suggest that NC-Col collagen may offer new strategies for improving therapeutic outcomes in OA, particularly in the context of ACI. Full article

Cartilage damage, particularly in the knee joint, presents a significant challenge in regenerative medicine due to its limited capacity for self-repair. Conventional treatments like microfracture surgery, autologous chondrocyte implantation (ACI), and osteochondral allografts often fall short, particularly in cases of larger defects or degenerative conditions. This has led to a growing interest in tissue engineering approaches that utilize biomaterial scaffolds to support cartilage regeneration. Among the many materials explored, chitosan—a naturally derived polysaccharide—has gained attention for its biocompatibility, biodegradability, and structural resemblance to the extracellular matrix (ECM) of cartilage. Recent advances in scaffold design have focused on modifying chitosan to improve its mechanical properties and enhance its biological performance. These modifications include chemical crosslinking, the incorporation of bioactive molecules, and the development of composite formulations. Such enhancements have allowed chitosan-based scaffolds to better support mesenchymal stem cell (MSC) differentiation into chondrocytes, paving the way for improved regenerative strategies. This review explores the latest progress in chitosan scaffold fabrication, preclinical findings, and the transition toward clinical applications. It also discusses the challenges that need to be addressed, such as mechanical stability, degradation rates, and the successful translation of research into viable therapeutic solutions. Full article

Background/Objectives: The treatment of cartilage damage is an ongoing challenge. Several techniques have been developed to address this problem. Matrix-Induced Autologous Chondrocyte Implantation (MACI) is often referred to as the “gold standard” for cartilage treatment. Numerous long-term outcome studies also have reported favorable results with Autologous Matrix-Induced Chondrogenesis (AMIC). Minced Cartilage Implantation (MCI) is a recently developed arthroscopic method. This technique has demonstrated promising outcomes, with the prospect of longer-term results still under investigation. This study aims to directly compare the patient-reported outcomes of these three techniques over a 2-year follow-up period. Methods: A total of N = 48 patients were included in the retrospective matched pair analysis (n = 16 MACI, n = 16 AMIC, n = 16 MCI). VAS, KOOS-Pain, and KOOS-Symptoms scores served as primary outcomes; the KOOS-ADL and -QOL and the Tegner Activity Scale (TAS) served as secondary outcomes. Results: All three groups did not differ from each other in the primary or secondary outcomes. Pain and function significantly improved from pre-surgery to two years after (VAS: p < 0.000; ES: η² = 0.27; KOOS-Pain: p < 0.000; ES: η² = 0.30; KOOS-Symptoms: p = 0.000; ES: η² = 0.26; KOOS-ADL: p > 0.000; ES: η² = 0.20; KOOS-QOL: p > 0.000; ES: η² = 0.30). There was no significant effect of time on the activity level. Conclusions: All three procedures show good patient-reported outcomes, low complication rates, and long graft longevity in the 2-year follow-up. Therefore, all three methods seem to be equally recommendable for the treatment of cartilage lesions. Full article

Cartilage damage is common in sports injuries and cartilage-related diseases, such as degenerative joint and rheumatic disorders. Autologous chondrocyte implantation (ACI) is a widely used cell-based therapy for repairing cartilage damage in clinical practice. In this procedure, a patient’s chondrocytes are isolated, cultured in vitro to expand the cell population, and then implanted into the damaged site. However, in vitro expansion of chondrocytes on standard 2D culture surfaces leads to dedifferentiation (loss of the chondrocyte phenotype), and the delivery of detached cells has proven to be ineffective. To overcome these limitations, the matrix-assisted ACI (MACI) procedure was developed. In MACI, matrices such as hydrogels and microspheres are used as cell carriers or scaffolds to deliver expanded chondrocytes, enhancing cell viability and precision delivery. To streamline the two key steps of MACI—cell expansion and delivery—this study aims to investigate various configurations of gelatin-based hydrogels for their potential to support both cell expansion and delivery as a single step. This study evaluated gelatin microspheres (Gel MS), micronized photo-crosslinked GelMA microparticles (GelMA MP), and bulky GelMA hydrogels containing cells (GelMA HG). Cell growth, maintenance of the chondrocyte phenotype, and cartilage extracellular matrix (ECM) production were assessed in pellet cultures for cells grown on/in these carriers, compared with cells cultured on tissue culture-treated polystyrene (TCP). Our results demonstrate that normal human knee articular chondrocytes exhibit robust growth on Gel MS and form aggregates enriched with glycosaminoglycan-rich ECM. Gel MS outperformed both GelMA MP and GelMA HG as a cell carrier by both supporting long-term cell growth with reduced dedifferentiation and precision delivery. Full article

(1) Background: Knee cartilage injury is at the top of the rising concerns among bone and joint disorder patients. Autologous chondrocyte implantation (ACI) is widely used to approach knee cartilage deterioration. Integrating autologous chondrocytes and periosteal patches aids in forming new cartilage-like tissue at the lesion area. This study uses a novel cell source from one-day-old porcine cartilage to fabricate a biomembrane as a substitute for periosteal membranes in cell implantation techniques for treating knee cartilage injuries. (2) Methods: Cells isolated from one-day-old porcine cartilage tissue were identified and assessed for their proliferation capability, differentiation ability, and membrane formation potential. The protein component of the biomembrane was also defined by proteomics. The cartilage repair ability was also confirmed using an in vitro transplantation model. (3) Results: Negative results for porcine infectious diseases are pivotal in selecting suitable piglets to provide cartilage tissue. The cells successfully obtained from one-day-old porcine cartilage exhibited stem-cell-like characteristics (CD34-, CD45-, CD90+, CD105+), including a high proliferation to 20 passages (doubling time: 1–2 days) and a capacity to differentiate into various cell types (osteogenesis, adipogenesis, and chondrogenesis). The stem cells were successfully applied in the fabrication of the biomembranes. The protein components of the biomembrane included an extracellular matrix and growth factors. The in vitro transplantation model showed that the biomembrane induced the repair ability of cartilage defects. (4) Conclusions: This study is the first to successfully harvest stem cells from one-day-old porcine cartilage for biomembrane fabrication for a knee cartilage injury therapeutic application. Full article

(1) Autologous chondrocyte implantation (ACI) is a prominent method for treating cartilage damage, but periosteal patches can cause chondrocyte leakage. This study evaluates the potential of a decellularized membrane derived from the cell-produced extracellular matrix of 1-day-old porcine cartilage (pcECM-DM) to act as a substitute for periosteal patches. (2) The interaction between young rabbit chondrocyte cells and pcECM-DM was assessed through cytotoxicity, differentiation, cell viability, cell migration, and adhesive ability. Rabbit chondrocyte cells, cultivated until passage two, were seeded onto a 6 mm diameter membrane. Assessments included DAPI-PKH26 staining, histological staining, live/dead assay, WST-1 assay, and proteomics analysis. (3) Results: DAPI-PKH26 staining showed successful adhesion and the uniform distribution of cells on the membrane. Safranin-O and H&E staining confirmed that the membrane supports chondrocyte adhesion and extracellular matrix production with high cell density and typical chondrocyte morphology. The live/dead assay demonstrated a high proportion of viable cells at 24 and 48 h, with increased cell proliferation over time. The WST-1 assay showed a significant increase in OD450 values, confirming cell proliferation and biocompatibility. Proteomic analysis revealed the significant enrichment of genes associated with extracellular matrix organization, cell adhesion, and cartilage development. (4) Conclusions: This novel biomaterial holds the potential to enhance cartilage regeneration and offer a viable alternative to periosteal patches. Full article