Induction of endostatin expression in meniscal fibrochondrocytes by co-culture with endothelial cells

Endostatin in 3D Fibrin Hydrogel Scaffolds Promotes Chondrogenic Differentiation in Swine Neonatal Meniscal Cells

The success of cell-based approaches for the treatment of cartilage or fibro-cartilaginous tissue defects requires an optimal cell source with chondrogenic differentiation ability that maintains its differentiated properties and stability following implantation. For this purpose, the aim of this study was to evaluate the use of endostatin (COL18A1), an anti-angiogenic factor, which is physiologically involved in cell differentiation during meniscus development. Swine neonatal meniscal cells not yet subjected to mechanical stimuli were extracted, cultured in fibrin hydrogel scaffolds, and treated at two different time points (T1 = 9 days and T2 = 21 days) with different concentrations of COL18A1 (10 ng/mL; 100 ng/mL; 200 ng/mL). At the end of the treatments, the scaffolds were examined through biochemical, molecular, and histochemical analyses. The results showed that the higher concentration of COL18A1 promotes a fibro-chondrogenic phenotype and improves cellularity index (DNA content, p < 0.001) and cell efficiency (GAGs/DNA ratio, p < 0.01) after 21 days. These data are supported by the molecular analysis of collagen type I (COL1A1, a marker of fibrous-like tissue, p < 0.001), collagen type II (COL2A1, a marker of cartilaginous-like tissue, p < 0.001) and SRY-Box Transcription Factor 9 (SOX9, an early marker of chondrogenicity, p < 0.001), as well as by histological analysis (Safranin-O staining), laying the foundations for future studies evaluating the involvement of 3D endostatin hydrogel scaffolds in the differentiation of avascular tissues.

Mesenchymal Stem Cells From Different Sources in Meniscus Repair and Regeneration

Meniscus damage is a common trauma that often arises from sports injuries or menisci tissue degeneration. Current treatment methods focus on the repair, replacement, and regeneration of the meniscus to restore its original function. The advance of tissue engineering provides a novel approach to restore the unique structure of the meniscus. Recently, mesenchymal stem cells found in tissues including bone marrow, peripheral blood, fat, and articular cavity synovium have shown specific advantages in meniscus repair. Although various studies explore the use of stem cells in repairing meniscal injuries from different sources and demonstrate their potential for chondrogenic differentiation, their meniscal cartilage-forming properties are yet to be systematically compared. Therefore, this review aims to summarize and compare different sources of mesenchymal stem cells for meniscal repair and regeneration.

[An optimized protocol of meniscus cell extraction for single-cell RNA sequencing]

OBJECTIVE

To optimize the protocol of meniscus cell extraction to enhance the efficiency of cell suspension preparation and maintain a high cell viability for single-cell RNA sequencing.

METHODS

We compared the efficiency of the routine cell extraction methods (short-time digestion and long-time digestion) and the optimized protocol for obtaining meniscus cell suspensions by evaluating the cell number obtained and the cell viability. Single-cell RNA sequencing datasets were analyzed to evaluate the stability of the cell suspension prepared using the optimized protocol. The reliability of the optimized protocol was assessed by comparing the single-cell RNA sequencing dataset obtained by the optimized protocol with published single-cell RNA sequencing datasets of the meniscus.

RESULTS

The optimized protocol harvested a greater number of cells (over 1×10⁵) than the routine protocols. The cell suspension prepared with the optimized protocol showed a cell viability higher than 80%, the highest among the 3 methods. Analysis of single-cell RNA sequencing datasets showed that the ratio of the mitochondrial genes was below 20% in over 80% of the cells. CD34⁺ cells, MCAM⁺ cells and COL1A1⁺ cells were identified in the datasets. Comparison with the publish datasets showed that the optimized protocol was capable of harvesting COL3A1⁺, COL1A1⁺, MYLK⁺, BMP2⁺, CD93⁺ and CDK1⁺ cells.

CONCLUSION

Single-cell suspension prepared from the meniscus can be stably obtained using the optimized protocol for single-cell RNA sequencing using the 10× Genomics platform.

Angiogenic approaches to meniscal healing

Meniscal injuries commonly result in osteoarthritis causing long term morbidity, lifelong treatment, joint replacement and significant financial burden to the Canadian healthcare system. Injuries to the outer third of the meniscus often heal well due to adequate blood supply. Healing of injuries in the inner two thirds of the meniscus are often critically retarded due to a lack of blood flow necessitating partial meniscectomy in many instances. Localized angiogenesis in the inner meniscus has yet to be achieved despite a belief that vascularization of these lesions corresponds with meniscal healing. This review briefly summarizes the growth factors that have been assessed for a role in meniscal healing and points to a significant knowledge gap in our understanding of meniscal healing.

Age-related modulation of angiogenesis-regulating factors in the swine meniscus

An in‐depth knowledge of the native meniscus morphology and biomechanics in its different areas is essential to develop an engineered tissue. Meniscus is characterized by a great regional variation in extracellular matrix components and in vascularization. Then, the aim of this work was to characterize the expression of factors involved in angiogenesis in different areas during meniscus maturation in pigs. The menisci were removed from the knee joints of neonatal, young and adult pigs, and they were divided into the inner, intermediate and outer areas. Vascular characterization and meniscal maturation were evaluated by immunohistochemistry and Western blot analysis. In particular, expression of the angiogenic factor Vascular Endothelial Growth Factor (VEGF) and the anti‐angiogenic marker Endostatin (ENDO) was analysed, as well as the vascular endothelial cadherin (Ve‐CAD). In addition, expression of Collagen II (COLL II) and SOX9 was examined, as markers of the fibro‐cartilaginous differentiation. Expression of VEGF and Ve‐CAD had a similar pattern in all animals, with a significant increase from the inner to the outer part of the meniscus. Pooling the zones, expression of both proteins was significantly higher in the neonatal meniscus than in young and adult menisci. Conversely, the young meniscus revealed a significantly higher expression of ENDO compared to the neonatal and adult ones. Analysis of tissue maturation markers showed an increase in COLL II and a decrease in SOX9 expression with age. These preliminary data highlight some of the changes that occur in the swine meniscus during growth, in particular the ensemble of regulatory factors involved in angiogenesis.

Correlation between vascular endothelial growth factor and long-term prognosis in patients with acute myocardial infarction

The aim of the present study was to investigate the correlation between plasma the levels of vascular endothelial growth factor (VEGF) and major adverse cardiovascular events (MACE) in patients with acute myocardial infarction (AMI). A total of 124 patients with AMI undergoing emergency percutaneous coronary intervention (PCI) were selected, and plasma VEGF levels were measured 7 days after the onset of AMI using an enzyme-linked immunosorbent assay. The patients were divided into the L (≤190 pg/ml VEGF) and H (>190 pg/ml VEGF) groups, and were followed up every 2 months for an average of 12 months. MACE were recorded during follow-up. On the basis of these results, the patients were further divided into the MACE and non-MACE (N-MACE) groups, and the serum VEGF concentration was compared between the two groups. At the 6-month follow-up, the incidence of MACE in the H group was found to be significantly reduced compared with the L group. The serum VEGF concentration in the N-MACE group was significantly higher compared with the MACE group. Multinomial logistic regression revealed that reduced VEGF levels (β=1.243; 95% CI, 1.018-1.326; P=0.026) were independent risk factors for MACE. In conclusion, high plasma VEGF levels at 7 days after AMI onset facilitate the long-term prognosis in the same infarct zone in patients with AMI, while low plasma VEGF levels are independent risk factors for MACE.

Chondromodulin-I derived from the inner meniscus prevents endothelial cell proliferation

The meniscus is a fibrocartilaginous tissue that plays an important role in controlling complex biomechanics of the knee. A perimeniscal capillary plexus supplies the outer meniscus, whereas the inner meniscus is composed of avascular tissue. Anti-angiogenic molecules, such as chondromodulin-I (ChM-I) and endostatin, have pivotal roles in preserving the avascularity of cartilage. However, the anti-angiogenic role of ChM-I is unclear in the meniscus. We hypothesized that the inner meniscus might maintain its avascular feature by expressing ChM-I. Immunohistochemical analyses revealed that ChM-I was mainly detected in the inner and superficial zones of the meniscus. On the other hand, endostatin distribution was similar between the inner and outer meniscus. In Western blot, ChM-I was detected only in the inner meniscus, whereas endostatin was equally observed in both inner and outer menisci. In addition, ChM-I concentration of the inner meniscus-derived conditioned medium was higher than that of the outer meniscus-derived medium. ChM-I removal from the inner meniscus-derived medium and functional blocking of ChM-I significantly increased endothelial cell proliferation. In this study, we demonstrated that the inner meniscus contained larger amounts of ChM-I, and that the inner meniscus-derived ChM-I inhibited endothelial cell proliferation. Our results suggest that ChM-I may be a key anti-angiogenic factor for maintaining the avascularity of the inner meniscus.

Biological strategies to enhance healing of the avascular area of the meniscus

Meniscal injuries in the vascularized peripheral part of the meniscus have a better healing potential than tears in the central avascular zone because meniscal healing principally depends on its vascular supply. Several biological strategies have been proposed to enhance healing of the avascular area of the meniscus: abrasion therapy, fibrin clot, organ culture, cell therapy, and applications of growth factors. However, data are too heterogeneous to achieve definitive conclusions on the use of these techniques for routine management of meniscal lesions. Although most preclinical and clinical studies are very promising, they are still at an experimental stage. More prospective randomised controlled trials are needed to compare the different techniques for clinical results, applicability, and cost-effectiveness.