Comparison between normal and loose fragment chondrocytes in proliferation and redifferentiation potential

Patient-Specific iPSC-Derived Models Link Aberrant Endoplasmic Reticulum Stress Sensing and Response to Juvenile Osteochondritis Dissecans Etiology

Juvenile osteochondritis dissecans (JOCD) is a pediatric disease, which begins with an osteonecrotic lesion in the secondary ossification center which, over time, results in the separation of the necrotic fragment from the parent bone. JOCD predisposes to early-onset osteoarthritis. However, the knowledge gap in JOCD pathomechanisms severely limits current therapeutic strategies. To elucidate its etiology, we conducted a study with induced pluripotent stem cells (iPSCs) from JOCD and control patients. iPSCs from skin biopsies were differentiated to iMSCs (iPSC-derived mesenchymal stromal cells) and subjected to chondrogenic and endochondral ossification, and endoplasmic reticulum (ER)-stress induction assays. Our study, using 3 JOCD donors, showed that JOCD cells have lower chondrogenic capability and their endochondral ossification process differs from control cells; yet, JOCD- and control-cells accomplish osteogenesis of similar quality. Our findings show that endoplasmic reticulum stress sensing and response mechanisms in JOCD cells, which partially regulate chondrocyte and osteoblast differentiation, are related to these differences. We suggest that JOCD cells are more sensitive to ER stress than control cells, and in pathological microenvironments, such as microtrauma and micro-ischemia, JOCD pathogenesis pathways may be initiated. This study is the first, to the best of our knowledge, to realize the important role that resident cells and their differentiating counterparts play in JOCD and to put forth a novel etiological hypothesis that seeks to consolidate and explain previously postulated hypotheses. Furthermore, our results establish well-characterized JOCD-specific iPSC-derived in vitro models and identified potential targets which could be used to improve diagnostic tools and therapeutic strategies in JOCD.

Chondrocyte Isolation from Loose Bodies-An Option for Reducing Donor Site Morbidity for Autologous Chondrocyte Implantation

Loose bodies (LBs) from patients with osteochondritis dissecans (OCD) are usually removed and discarded during surgical treatment of the defect. In this study, we address the question of whether these LBs contain sufficient viable and functional chondrocytes that could serve as a source for autologous chondrocyte implantation (ACI) and how the required prolonged in vitro expansion affects their phenotype. Chondrocytes were isolated from LBs of 18 patients and compared with control chondrocyte from non-weight-bearing joint regions (n = 7) and bone marrow mesenchymal stromal cells (BMSCs, n = 6) obtained during primary arthroplasty. No significant differences in the initial cell yield per isolation and the expression of the chondrocyte progenitor cell markers CD44 + /CD146+ were found between chondrocyte populations from LBs (LB-CH) and control patients (Ctrl-CH). During long-term expansion, LB-CH exhibited comparable viability and proliferation rates to control cells and no ultimate cell cycle arrest was observed within 12 passages respectively 15.3 ± 1.1 mean cumulative populations doublings (CPD). The chondrogenic differentiation potential was comparable between LB-CH and Ctrl-CH, but both groups showed a significantly higher ability to form a hyaline cartilage matrix in vitro than BMSC. Our data suggest that LBs are a promising cell source for obtaining qualitatively and quantitatively suitable chondrocytes for therapeutic applications, thereby circumventing donor site morbidity as a consequence of the biopsies required for the current ACI procedure.

Single-Cell RNA Sequencing Reveals Transcriptional Changes in the Cartilage of Subchondral Insufficiency Fracture of the Knee

Purpose

Subchondral insufficiency fracture of the knee (SIFK) is a common cause of knee joint pain that mainly afflicts the elderly. Until now, how a sudden insufficiency fracture of subchondral bone affects the transcriptomic profiles of cartilage in SIFK and OA patients are largely unknown.

Methods

Single-cell RNA sequencing (scRNA-seq) was used to identify various cell subsets and evaluate transcriptomic differences in cartilage of SIFK and OA patients. In addition, the above findings were confirmed by histological evaluation and immunohistochemical (IHC) staining.

Results

We found that the transcriptomic profiles of cartilage in the SIFK patient was completely different from those of normal and OA patients. Accordingly, several novel cell clusters with activation of hypoxia and endochondral ossification signaling were identified in the SIFK cartilage. Chondrocyte trajectories analysis and IHC staining revealed that transcription factors including TCF4 were found to be highly up-regulated during the occurrence of SIFK, which might drive the reactive formation of cartilage and fibrous tissue and the activation of endochondral ossification.

Conclusion

This is the first report to elucidate the transcriptomic alterations and distinct cell type subpopulations in the cartilage of SIFK and OA by the use of scRNA-seq, which provides a new insight in the understanding of the initiation and progression of SIFK.

Human amniotic membrane as differentiating matrix for in vitro chondrogenesis

Aim: The aim of the present study is to use human amniotic membrane (HAM) for in vitro chondrogenesis of placenta-derived mesenchymal stem cells (MSCs) and umbilical cord-derived MSCs. Materials & methods: MSCs from the placenta and umbilical cord were isolated, characterized by immunophenotyping and after analyzing their rate of proliferation, cytotoxicity and viability, chondrogenesis was performed on plastic adherent surface and on HAM. Results: Successfully isolated and characterized placenta-derived MSCs and umbilical cord-derived MSCs revealed positive expression of MSCs markers CD90, CD73, CD105 and CD49d, while they were negative for CD45. Both types of cells in the presence of chondrogenic induction medium on plastic adherent surface and HAM showed aggregates of proteoglycan and strong expression of COL2A1 (collagen 2) and ACAN1 (aggrecan). Conclusion: HAM supported proliferation as well as chondrogenesis of MSCs and provide novelty of HAM utilization as an efficient natural delivery matrix for stem cell transplantation.

Articular Cartilage Repair of the Knee in Children and Adolescents

Articular cartilage predominantly serves a biomechanical function, which begins in utero and further develops during growth and locomotion. With regard to its 2-tissue structure (chondrocytes and matrix), the regenerative potential of hyaline cartilage defects is limited. Children and adolescents are increasingly suffering from articular cartilage and osteochondral deficiencies. Traumatic incidents often result in damage to the joint surfaces, while repetitive microtrauma may cause osteochondritis dissecans. When compared with their adult counterparts, children and adolescents have a greater capacity to regenerate articular cartilage defects. Even so, articular cartilage injuries in this age group may predispose them to premature osteoarthritis. Consequently, surgery is indicated in young patients when conservative measures fail. The operative techniques for articular cartilage injuries traditionally performed in adults may be performed in children, although an individualized approach must be tailored according to patient and defect characteristics. Clear guidelines for defect dimension–associated techniques have not been reported. Knee joint dimensions must be considered and correlated with respect to the cartilage defect size. Particular attention must be given to the subchondral bone, which is frequently affected in children and adolescents. Articular cartilage repair techniques appear to be safe in this cohort of patients, and no differences in complication rates have been reported when compared with adult patients. Particularly, autologous chondrocyte implantation has good biological potential, especially for large-diameter joint surface defects.

ROCK inhibition stimulates SOX9/Smad3-dependent COL2A1 expression in inner meniscus cells

BACKGROUND

Proper functioning of the meniscus depends on the composition and organization of its fibrocartilaginous extracellular matrix. We previously demonstrated that the avascular inner meniscus has a more chondrocytic phenotype compared with the outer meniscus. Inhibition of the Rho family GTPase ROCK, the major regulator of the actin cytoskeleton, stimulates the chondrogenic transcription factor Sry-type HMG box (SOX) 9-dependent α1(II) collagen (COL2A1) expression in inner meniscus cells. However, the crosstalk between ROCK inhibition, SOX9, and other transcription modulators on COL2A1 upregulation remains unclear in meniscus cells. The aim of this study was to investigate the role of SOX9-related transcriptional complex on COL2A1 expression under the inhibition of ROCK in human meniscus cells.

METHODS

Human inner and outer meniscus cells were prepared from macroscopically intact lateral menisci. Cells were cultured in the presence or absence of ROCK inhibitor (ROCKi, Y27632). Gene expression, collagen synthesis, and nuclear translocation of SOX9 and Smad2/3 were analyzed.

RESULTS

Treatment of ROCKi increased the ratio of type I/II collagen double positive cells derived from the inner meniscus. In real-time PCR analyses, expression of SOX9 and COL2A1 genes was stimulated by ROCKi treatment in inner meniscus cells. ROCKi treatment also induced nuclear translocation of SOX9 and phosphorylated Smad2/3 in immunohistological analyses. Complex formation between SOX9 and Smad3 was increased by ROCKi treatment in inner meniscus cells. Chromatin immunoprecipitation analyses revealed that association between SOX9/Smad3 transcriptional complex with the COL2A1 enhancer region was increased by ROCKi treatment.

CONCLUSIONS

This study demonstrated that ROCK inhibition stimulated SOX9/Smad3-dependent COL2A1 expression through the immediate nuclear translocation of Smad3 in inner meniscus cells. Our results suggest that ROCK inhibition can stimulates type II collagen synthesis through the cooperative activation of Smad3 in inner meniscus cells. ROCKi treatment may be useful to promote the fibrochondrocytic healing of the injured inner meniscus.

Adipose stem cells differentiated chondrocytes regenerate damaged cartilage in rat model of osteoarthritis

Transplantation of mesenchymal stem cells (MSCs) or autologous chondrocytes has been shown to repair damages to articular cartilage due to osteoarthritis (OA). However, survival of transplanted cells is considerably reduced in the osteoarthritic environment and it affects successful outcome of the transplantation of the cells. Differentiated chrondroytes derived from adipose stem cells have been proposed as an alternative source and our study investigated this possibility in rats. We investigated the regenerative potential of ADSCs and DCs in osteoarthritic environment in the repair of cartilage in rats. We found that ADSCs maintained fibroblast morphology in vitro and also expressed CD90 and CD29. Furthermore, ADSCs differentiated into chondrocytes, accompanied by increased level of proteoglycans and expression of chondrocytes specific genes, such as, Acan, and Col2a1. Histological examination of transplanted knee joints showed regeneration of cartilage tissue compared to control OA knee joints. Increase in gene expression for Acan, Col2a1 with concomitant decrease in the expression of Col1a1 suggested formation of hyaline like cartilage. A significant increase in differentiation index was observed in DCs and ADSCs transplanted knee joints (P = 0.0110 vs. P = 0.0429) when compared to that in OA control knee joints. Furthermore, transplanted DCs showed increased proliferation along with reduction in apoptosis as compared to untreated control. In conclusion, DCs showed better survival and regeneration potential as compared with ADSCs in rat model of OA and thus may serve a better option for regeneration of osteoarthritic cartilage.

The anterior cruciate ligament-lateral meniscus complex: A histological study

The anterior root of the lateral meniscus (LM) dives underneath the tibial attachment of the anterior cruciate ligament (ACL). Although the distinct role of meniscal attachments has been investigated, the relationship between the LM anterior insertion (LMAI) and ACL tibial insertion (ACLTI) remains unclear. This study histologically analyzed the LMAI and ACLTI. Samples were divided into four regions in an anterior-to-posterior direction. Histological measurements of these insertion sites were performed using safranin O-stained coronal sections. Distribution and signal densities of type I and II collagen were quantified. The ACLTI and LMAI formed the ACL-LM complex via fiber connections. The anterior part of the ACLTI had a widespread attachment composed of dense fibers. Attachment fibers of the LMAI became dense and wide gradually at the middle-to-posterior region. The ACL-LM transition zone (ALTZ) was observed between the LMAI and the lateral border of the ACLTI at the middle part of the ACL tibial footprint. Type II collagen density of the LMAI was higher than that of the ACLTI and ALTZ. Our results can help create an accurate tibial bone tunnel within the dense ACL attachment during ACL reconstruction surgery.

Postoperative change in the length and extrusion of the medial meniscus after anterior cruciate ligament reconstruction

PURPOSE

The medial meniscus is a secondary stabilizer of anterior tibial translation in anterior cruciate ligament (ACL)-deficient knees. ACL reconstruction effectively restores an increased anterior tibial translation in the ACL-deficient knee. However, knee osteoarthritis sometimes develops in ACL-reconstructed patients during a long-term follow-up period. We hypothesized that the medial meniscal position would be different between the ACL-deficient and reconstructed knees. The aim of this study was to investigate pre-operative and postoperative location of the medial meniscus in patients who underwent ACL reconstruction.

METHODS

ACL-reconstructed knees (28 knees) and normal knees (27 knees) were investigated. Medial tibial plateau length (MTPL) and medial tibial plateau width (MTPW) were determined using radiographic images. Magnetic resonance imaging (MRI)-based medial meniscal length (MML), medial meniscal width (MMW), and medial meniscal extrusion (MME) were measured. Postoperative change in the MML, MMW, and MME were evaluated and compared with those in normal knees.

RESULTS

No significant differences between the ACL-deficient (pre-operative) and normal groups were noted. The ACL-reconstructed (postoperative) group showed an increase in the MML, in the percentage of the MML (%MML = 100 MML/MTPL), and in the MME. Significant differences between postoperative and normal groups were observed in the MML, %MML, and MME. MMW and MMW percentage (100 MMW/MTPW) were similar in all groups.

CONCLUSIONS

The anteroposterior length and radial extrusion of the medial meniscus increased after ACL reconstruction. Transposition of the medial meniscus may be a possible cause of developing further degenerative knee joint disorders after ACL reconstruction.

ROCK inhibition enhances aggrecan deposition and suppresses matrix metalloproteinase-3 production in human articular chondrocytes

Homeostasis of articular cartilage is maintained by a balance between catabolism and anabolism. Matrix metalloproteinase-3 (MMP-3) catabolism of cartilaginous extracellular matrix (ECM), including aggrecan (AGN), is an important factor in osteoarthritis progression. We previously reported that inhibition of Rho-associated coiled-coil forming kinase (ROCK), an effector of Rho family GTPases, activates the chondrogenic transcription factor SRY-type high-mobility-group box (SOX) 9 and prevents dedifferentiation of monolayer-cultured chondrocytes. We hypothesized that ROCK inhibition prevents chondrocyte dedifferentiation by altering the transcriptional balance between MMP-3 and AGN. Normal human articular chondrocytes were cultured in the presence or absence of ROCK inhibitor (ROCKi, Y-27632). Expression of MMP-3 and AGN during monolayer cultivation was assessed by quantitative real-time PCR and western blot analysis. Chondrogenic redifferentiation potential of ROCKi-treated chondrocytes was evaluated by immunohistological analysis of pellet cultures. ROCKi treatment suppressed MMP-3 expression in monolayer- and pellet-cultured chondrocytes but increased AGN expression. Chromatin immunoprecipitation revealed that the association between transcription factors E26 transformation specific (ETS)-1 and SOX9 and their target genes MMP-3 and AGN, respectively, was affected by ROCKi treatment. ROCKi decreased the association between ETS-1 and its binding sites on the MMP-3 promoter, whereas ROCKi promoted the interaction between SOX9 and the AGN promoter. Our results suggest that ROCK inhibition may have an important role in modulating the balance between degradation and synthesis of cartilaginous ECM, a finding that may facilitate development of techniques to prepare differentiated chondrocytes for cartilage regeneration therapy.

Comparative study by computed radiography, histology, and scanning electron microscopy of the articular cartilage of normal goats and in chronic infection with caprine arthritis-encephalitis virus

In the northeast of Brazil, caprine arthritis-encephalitis (CAE) is one of the key reasons for herd productivity decreasing that result in considerable economic losses. A comparative study was carried out using computed radiography (CR), histological analysis (HA), and scanning electronic microscopy (SEM) of the joints of CAE infected and normal goats. Humerus head surface of positive animals presented reduced joint space, increased bone density, and signs of degenerative joint disease (DJD). The carpal joint presented no morphological alterations in CR in any of the animals studied. Tarsus joint was the most affected, characterized by severe DJD, absence of joint space, increased periarticular soft tissue density, edema, and bone sclerosis. Histological analysis showed chronic tissue lesions, complete loss of the surface zone, absence of proteoglycans in the transition and radial zones and destruction of the cartilage surface in the CAE positive animals. Analysis by SEM showed ulcerated lesions with irregular and folded patterns on the joint surface that distinguished the limits between areas of normal and affected cartilage. The morphological study of the joints of normal and CAE positive goats deepened understanding of the alteration in the tissue bioarchitecture of the most affected joints. The SEM finding sustained previous histological reports, similar to those found for rheumatoid arthritis, suggesting that the goat infected with CAE can be considered as a potential model for research in this area.

Postoperative change in medial meniscal length in concurrent all-inside meniscus repair with anterior cruciate ligament reconstruction

PURPOSE

Meniscus repair can restore meniscal function that transfers the axial compressive force to circumferential tensile strain. However, few reports have investigated the relationship between concurrent meniscus repair with acute anterior cruciate ligament (ACL) reconstruction and postoperative meniscal position. This study aimed to evaluate medial meniscal size and clinical results in patients who underwent ACL reconstruction and concomitant all-inside medial meniscus repair.

METHODS

Twenty patients underwent ACL reconstruction and concurrent medial meniscus repair of a peripheral longitudinal tear using the FasT-Fix meniscal repair device. Medial tibial plateau length (MTPL) and width (MTPW) were determined by radiographic images. We evaluated the Lysholm score, anteroposterior instability, meniscal healing and magnetic resonance imaging (MRI)-based medial meniscal length (MML) and width (MMW). Correlations between MRI-based meniscal size, radiographic measurement and height were investigated.

RESULTS

All patients showed complete healing of the repaired meniscus in arthroscopic evaluation. However, one patient needed a subsequent meniscus repair during the follow-up period. Lysholm score and anteroposterior instability improved significantly. A better correlation was observed between MMW and MTPW than between MML and MTPL. Concurrent all-inside medial meniscus repair with ACL reconstruction significantly increased MML percentage (%MML) (100 MML/MTPL) but did not affect MMW percentage (%MMW) (100 MMW/MTPW).

CONCLUSIONS

Concurrent all-inside medial meniscus repair with ACL reconstruction had satisfactory clinical results. %MML was increased by concurrent medial meniscus repair without affecting %MMW. Our results suggest that medial meniscus repair associated with ACL reconstruction may restore meniscal function by adjusting the anteroposterior length of the torn medial meniscus.