Do gene expression changes in articular cartilage proteases of the synovial membrane correlate with expression changes of the same genes in systemic blood cells?

Is the Synovium the First Responder to Posttraumatic Knee Joint Stress? The Molecular Pathogenesis of Traumatic Cartilage Degeneration

OBJECTIVE

The aim of this study was to evaluate if a similar catabolic and inflammatory gene pattern exists between the synovium, hyaline cartilage, and blood of patients with the knee joint tissues and if one precedes the other.

DESIGN

A total of fifty-eight patients (34 females and 24 males) with a mean age of 44.7 years (range, 18-75) underwent elective knee arthroscopy due to previously diagnosed pathology. Full blood samples were collected preoperatively from synovium and cartilage samples intraoperatively. Real time PCR with spectrophotometric analysis was performed. Following genes taking part in ECM (extracellular matrix) remodeling were selected for analysis: MMP-1, MMP-2, MMP-8, MMP-9, MMP-13, MMP-14, ADAMTS-4 (Agg1) and ADAMTS-5 (Agg2) proteases, TIMP-1, and TIMP-2 - their inhibitors - and IL-1 and TNF-α cytokines.

RESULTS

Analysis revealed a strong and significant correlation between gene expression in synovial and systemic blood cells (p <0.05 for all studied genes) with ADAMTS-4, ADAMTS-5, IL-1, TNF-α and TIMP-2 expression most positively correlated with an R>0.8 for each. An analysis between chondrocytes and systemic blood gene expression shown no significant correlation for all genes. Bivariate correlation of International Cartilage Repair Society grading and genes expression revealed significant associations with synovial MMP-1, MMP-2, MMP-8, MMP-9, IL-1, TNF-α and TIMP-2.

CONCLUSION

We suggest that the synovial tissue is the first responder for knee joint stress factors in correlation with the response of blood cells. The chondrocyte's genetic response must be further investigated to elucidate the genetic program of synovial joints, as an organ, during OA development and progression.

Proteolysis and cartilage development are activated in the synovium after surgical induction of post traumatic osteoarthritis

Anterior cruciate ligament (ACL) transection surgery in the minipig induces post-traumatic osteoarthritis (PTOA) in a pattern similar to that seen in human patients after ACL injury. Prior studies have reported the presence of cartilage matrix-degrading proteases, such as Matrix metalloproteinase-1 (MMP-1) and A disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4), in the synovial fluid of injured or arthritic joints; however, the tissue origin of these proteases is unknown. The objective of this study was to identify transcriptional processes activated in the synovium after surgical induction of PTOA with ACL transection, and to determine if processes associated with proteolysis were enriched in the synovium after ACL transection. Unilateral ACL transection was performed in adolescent Yucatan minipigs and synovium samples were collected at 1, 5, 9, and 14 days post-injury. Transcriptome-wide gene expression levels were determined using bulk RNA-Sequencing in the surgical animals and control animals with healthy knees. The greatest number of transcripts with significant changes was observed 1 day after injury. These changes were primarily associated with cellular proliferation, consistent with measurements of increased cellularity of the synovium at the two-week time point. At five to 14 days, the expression of transcripts relating to proteolysis and cartilage development was significantly enriched. While protease inhibitor-encoding transcripts (TIMP2, TIMP3) represented the largest fraction of protease-associated transcripts in the uninjured synovium, protease-encoding transcripts (including MMP1, MMP2, ADAMTS4) predominated after surgery. Cartilage development-associated transcripts that are typically not expressed by synovial cells, such as ACAN and COMP, were enriched in the synovium following ACL-transection. The upregulation in both catabolic processes (proteolysis) and anabolic processes (cartilage development) suggests that the synovium plays a complex, balancing role in the early response to PTOA induction.

Fibrin-hyaluronic acid hydrogel-based delivery of antisense oligonucleotides for ADAMTS5 inhibition in co-delivered and resident joint cells in osteoarthritis

To date no disease-modifying drugs for osteoarthritis (OA) are available, with treatment limited to the use of pain killers and prosthetic replacement. The ADAMTS (A Disintegrin and Metallo Proteinase with Thrombospondin Motifs) enzyme family is thought to be instrumental in the loss of proteoglycans during cartilage degeneration in OA, and their inhibition was shown to reverse osteoarthritic cartilage degeneration. Locked Nucleic Acid (LNA)-modified antisense oligonucleotides (gapmers) released from biomaterial scaffolds for specific and prolonged ADAMTS inhibition in co-delivered and resident chondrocytes, is an attractive therapeutic strategy. Here, a gapmer sequence identified from a gapmer screen showed 90% ADAMTS5 silencing in a monolayer culture of human OA chondrocytes. Incorporation of the gapmer in a fibrin-hyaluronic acid hydrogel exhibited a sustained release profile up to 14 days. Gapmers loaded in hydrogels were able to transfect both co-embedded chondrocytes and chondrocytes in a neighboring gapmer-free hydrogel, as demonstrated by flow cytometry and confocal microscopy. Efficient knockdown of ADAMTS5 was shown up to 14 days in both cell populations, i.e. the gapmer-loaded and gapmer-free hydrogel. This work demonstrates the use applicability of a hydrogel as a platform for combined local delivery of chondrocytes and an ADAMTS-targeting gapmer for catabolic gene modulation in OA.

Mesenchymal stem cells reside in anterior cruciate ligament remnants in situ

PURPOSE

It has been reported that the anterior cruciate ligament (ACL) has certain self-healing ability after acute injury or with primary suture repair. Many studies have confirmed that a remnant preservation technique with ACL reconstruction contributes to biological augmentation for ACL healing. However, it remains unclear whether mesenchymal stem cells (MSC) reside in ACL remnants in situ. The aim of this study was to investigate the methods of culture and identification of MSC derived from the remnants of ACL rupture patients and to analyse these MSC's properties.

METHODS

The cells of ACL remnants from the ACL rupture patients were isolated by the methods of enzymatic digestion and cultured in vitro to the third passage under the microscope to observe their morphology and growth status. The third passage of isolated cells was analysed for the identification of immunophenotype, osteogenic, adipogenic and chondrogenic differentiation.

RESULTS

On the third to fifth days of in vitro culture, a few cells of long fusiform shape appeared and were adherent to the plastic walls. On the sixth to ninth days, cells clustered and colonies were observed. The third passage cells showed uniform cell morphology and good proliferation, with appearance of the typical surface markers of MSC, CD29, CD44, CD90 and CD105. The surface markers of CD34 and CD45 of haematopoietic stem cells were not expressed. Under appropriate conditions of in vitro culture, isolated cells could be differentiated into osteoblasts that deposit mineralised matrix and express early osteogenic markers, adipocytes that accumulate lipid droplets in cytoplasm and chondrocytes that secrete chondrogenic-specific matrix aggrecan and collagen II. Real-time polymerase chain reaction (PCR) analysis demonstrated that the specific mRNA expression of osteogenesis, adipogenesis and chondrogenesis increased significantly compared with the control groups at day zero.

CONCLUSIONS

Stem cells derived in situ from the human ACL stump were successfully isolated and characterised. Those isolated cells were identified as MSC according to their adherent ability, morphology, surface markers and multilineage differentiation potential. MSC derived from ACL remnants could be a potential source of seeding cells for ligament regeneration.