Detection and initial characterization of synovial lining fragments in synovial fluid

Device-Based Enrichment of Knee Joint Synovial Cells to Drive MSC Chondrogenesis Without Prior Culture Expansion In Vitro: A Step Closer to 1-Stage Orthopaedic Procedures

BACKGROUND

Synovial fluid (SF) mesenchymal stem cells (MSCs) are derived from the synovial membrane and have cartilage repair potential. Their current use in clinical practice is largely exploratory. As their numbers tend to be small, therapeutic procedures using MSCs typically require culture expansion. Previous reports indicate that the stem cell-mobilizing device (STEM device) intraoperatively increases SF-MSCs.

PURPOSE

This study evaluated the chondrogenic potential of non-culture expanded synovium-mobilized MSCs and SF-microfragments obtained after enrichment using the STEM device and ascertained if device-mediated synovial membrane manipulation facilitated ongoing MSC release.

STUDY DESIGN

Controlled laboratory study.

METHODS

Two samples of aspiration fluid were collected intraoperatively before and after STEM device utilization from patients (n = 16) undergoing diagnostic or therapeutic knee arthroscopy. Human knee synovium (n = 5) was collected during total knee replacement, and a suspended culture was performed to assess the effect of the STEM device on ongoing MSC release. Colony forming unit-fibroblastic assays were used to determine the number of MSCs. Additionally, cytometric characterization of stromal and immune cells and chondrogenesis differentiation assay were performed without culture expansion. Filtered platelet concentrates were prepared using the HemaTrate system.

RESULTS

After STEM device use, a significant increase was evident in SF-MSCs (P = .03) and synovial fluid-resident synovial tissue microfragments (P = .03). In vitro-suspended synovium released significantly more MSCs following STEM device use than nonstimulated synovium (P = .01). The STEM device-released total cellular fraction produced greater in vitro chondrogenesis with significantly more glycosaminoglycans (GAGs; P < .0001) when compared with non-STEM device synovial fluid material. Nonexpanded SF-MSCs and SF-microfragments combined with autologous filtered platelet concentrate produced significantly more GAGs than the complete chondrogenic media (P < .0001). The STEM device-mobilized cells contained more M2 macrophage cells and fewer M1 cells.

CONCLUSION

Non-culture expanded SF-MSCs and SF-microfragments had the potential to undergo chondrogenesis without culture expansion, which can be augmented using the STEM device with increased MSC release from manipulated synovium for several days. Although preliminary, these findings offer proof of concept toward manipulation of the knee joint environment to facilitate endogenous repair responses.

CLINICAL RELEVANCE

Although numbers were small, this study highlights 3 factors relevant to 1-stage joint repair using the STEM device: increased SF-MSCs and SF-microfragments and prolonged synovial release of MSCs. Joint repair strategies involving endogenous MSCs for cartilage repair without the need for culture expansion in a 1-stage procedure may be possible.

Cutaneous metaplastic synovial cyst in Ehlers-Danlos syndrome

Classic Ehlers-Danlos syndrome (EDS) is a connective tissue disorder characterized by laxity. The skin, as one of the organs involved, shows hyperextensibility, which makes it prone to trauma. In this context, it would seem logical for cutaneous synovial metaplasia, which is considered a form of repair, to be commonly found in cases of EDS. However, there are only two previously published cases of synovial metaplasia in EDS. We present a third case in a 56-year-old woman with painful redundant skin in both elbows and knees for whom a skin fold of the left elbow was removed to relieve her symptoms. The biopsy showed preservation of the elastic and collagen fibers. The main alteration was the evidence of dermal cystic spaces lined by fibrinoid rests with focal pseudopapillary projections. However, in some zones the cellular lining was preserved, and it was composed of vimentin-positive, fibroblast-like flat, elongated cells, as well as CD68-positive macrophages. No birefringent particles were found in an examination under polarized light.

Prior Surgery Negatively Affects Cell Culture Identity in Patients Undergoing Autologous Chondrocyte Implantation

BACKGROUND

Recently, a cell identity assay has been introduced to evaluate the identity of cultured chondrocytes before autologous chondrocyte implantation (ACI), which was shown to be associated with graft survival after ACI.

PURPOSE

To identify the influence of several patient- and lesion-specific factors on cell identity and viability assays.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 187 patients with second-generation ACI were included in this study. Patient and lesion characteristics, cell viability, cell identity, and biopsy specimen weight were recorded for each patient. A binomial logistic regression model was utilized to determine patient-specific predictive factors for cell product quality.

RESULTS

The implanted ACI cell products showed a cell viability of 93% ± 2.4% (mean ± SD; range, 84-98) with an identity score of 5.8 ± 2.1 (range, -0.08 to 9.46). Patients with multiple previous surgical procedures on the index knee had significantly lower cell identity scores when compared with patients without previous surgery (odds ratio = 0.31; 95% CI, 0.16-0.59; P < .001). Patients without surgical history had significantly higher cell identity scores than patients with 1 and ≥2 previous surgical procedures on the index knee (6.32 vs 5.32 vs 5.05; P = .006 and P < .001, respectively). Cell viability was not predicted by any preoperative variable (P > .05). Cell identity and viability were not associated with each other or with biopsy specimen weight (P > .05).

CONCLUSION

Cartilage biopsy specimens from patients with ≥1 previous surgical procedures resulted in implants with lower cell identity scores when compared with patients without previous operations. None of the other patient- or lesion-specific factors were correlated, specifically biopsy specimen weight.

Increased Chondrocytic Gene Expression Is Associated With Improved Repair Tissue Quality and Graft Survival in Patients After Autologous Chondrocyte Implantation

BACKGROUND

Assays to quantitate the quality of autologous chondrocyte implants have recently become available. However, the correlation of the assay score with radiological and clinical outcomes has not been established.

PURPOSE/HYPOTHESIS

The purpose was to assess the influence of cell identity (chondrocyte/synoviocyte gene expression ratio) and viability on patient-reported outcome measures, graft survival, and repair tissue quality. It was hypothesized that greater cell product quality as assessed through an identity assay and cell viability is associated with superior outcomes after autologous chondrocyte implantation (ACI) for symptomatic cartilage defects.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Seventy-nine patients with a minimum follow-up of 2 years were included in this study. Of these, 67 patients were available for imaging assessment utilizing the Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) scoring system. Patients were assigned to groups either below or above the cohort's mean based on their individual cell identity score and viability percentage.

RESULTS

Patients were predominantly female (57.7%) with a mean age of 30.0 ± 9.3 years. No differences were seen between Knee injury and Osteoarthritis Outcome Score, Lysholm, Tegner, or International Knee Documentation Committee Subjective Knee Evaluation Form within the viability and cell identity groups at a final follow-up of 3.8 ± 1.4 years after ACI (P > .05). In a subset of patients, the mean MOCART score was 68.3 ± 15.6 at an average magnetic resonance imaging follow-up of 17.7 ± 9.56 months. Low cell identity was significantly associated with the degree of defect filling (P = .025), integration of border zone (P = .01), effusion (P = .024), and ACI graft failure (P = .002). Patients with above-average cell identity scores had a significantly higher survival rate at 5-year follow-up compared with patients with below-average scores (95.8% vs 64.7%; P = .013). Cell viability did not influence MOCART subscales or graft failure (all P > .05). Cell viability and identity showed no significant correlation with each other (r = -0.045; P = .694).

CONCLUSION

Cell identity was significantly correlated with structural repair quality and graft survival after second-generation ACI for symptomatic chondral lesions in the knee. While improved imaging outcome and higher graft survivorship were associated with a higher individual cell identity score indicating a higher chondrocyte/synoviocyte gene expression ratio in the final cell product, clinical outcome did not correlate with the identity score.

[Synovial fluid cytodiagnosis]

Synovial fluid samples represent only a very small percentage of routine work in a cytology laboratory. However, its microscopic examination allows us to observe different types of cells, particles and structures that, due to their morphological characteristics, may provide relevant data for cytodiagnosis. We present certain aspects related to arthrocentesis, the relationship between the gross appearance of synovial fluid and certain pathological processes, as well as the different techniques for processing and staining the smears. Furthermore, we describe the main cytological findings in various pathological conditions of the synovial joints, such as infections (bacterial and fungal), non-infectious inflammatory type (osteoarthrosis, rheumatoid arthritis, connective tissue diseases) and tumoral, distinguishing between primary and metastatic, both solid and haematological neoplasms.

In vitro and in vivo potentialities for cartilage repair from human advanced knee osteoarthritis synovial fluid-derived mesenchymal stem cells

Background

Mesenchymal stem cells (MSCs) are found in synovial fluid (SF) and can easily be harvested during arthrocentesis or arthroscopy. However, SF-MSC characterization and chondrogenicity in collagen sponges have been poorly documented as well as their hypothetical in vivo chondroprotective properties with intra-articular injections during experimental osteoarthritis (OA).

Methods

SF-MSCs were isolated from human SF aspirates in patients suffering from advanced OA undergoing total knee joint replacements. SF-MSCs at passage 2 (P2) were characterized by flow cytometry for epitope profiling. SF-MSCs at P2 were subsequently cultured in vitro to assess their multilineage potentials. To assess their chondrogenicity, SF-MSCs at P4 were seeded in collagen sponges for 4 weeks under various oxygen tensions and growth factors combinations to estimate their gene profile and matrix production. Also, SF-MSCs were injected into the joints in a nude rat anterior cruciate ligament transection (ACLT) to macroscopically and histologically assess their possible chondroprotective properties,.

Results

We characterized the stemness (CD73+, CD90+, CD105+, CD34−, CD45−) and demonstrated the multilineage potency of SF-MSCs in vitro. Furthermore, the chondrogenic induction (TGF-ß1 ± BMP-2) of these SF-MSCs in collagen sponges demonstrated a good capacity of chondrogenic gene induction and extracellular matrix synthesis. Surprisingly, hypoxia did not enhance matrix synthesis, although it boosted chondrogenic gene expression (ACAN, SOX9, COL2A1). Besides, intra-articular injections of xenogenic SF-MSCs did exert neither chondroprotection nor inflammation in ACLT-induced OA in the rat knee.

Conclusions

Advanced OA SF-MSCs seem better candidates for cell-based constructs conceived for cartilage defects rather than intra-articular injections for diffuse OA.

Synovial fluid‑derived synovial fragments represent an improved source of synovial mesenchymal stem cells in the temporomandibular joint

Surgery-obtained synovium specimens (SSSs) can provide a source of synovial mesenchymal stem cells (SMSCs) for experimental studies. However, these specimens contain diverse tissues, including the intima and subintima; therefore, these SMSCs are not entirely derived from the intima and their cell source is heterogeneous. The present study isolated synovial fragments (SFs) from synovial fluid dilutions extracted from patients with temporomandibular joint (TMJ) osteoarthrosis. Unlike SSSs, SFs, which are membranous and translucent, consist of only several cell layers, indicating the presence of only the intima. In the present study, SF cells (SFCs) and SSS cells (SSSCs) exhibited a homogeneous, fibroblast-like, spindle-shaped morphology after passaging in vitro. Furthermore, both cell types exhibited similar proliferative and differentiation potentials in vitro. However, SFCs exhibited more uniform surface markers compared with SSSCs when analysed by flow cytometry. Taken together, these results indicated that SFs contained a greater amount of unmixed intima than SSSs, and that SFCs exhibited more homogeneous characteristics than SSSCs, thereby offering an improved source of SMSCs in the TMJ.

Synovial fluid and synovial membrane mesenchymal stem cells: latest discoveries and therapeutic perspectives

Mesenchymal stem cells (MSCs) have the ability to differentiate into osteoblasts, chondroblasts, adipocytes, and even myoblasts. Most studies have focused on finding MSCs in different parts of the body for medical treatment. Every joint structure, including bone, joint fat, articular cartilage, and synovium, potentially contains resident MSCs. Recently, a progenitor cell population has been found in synovial fluid and showed similarities with both bone marrow and synovial membrane MSCs. Synovial fluid MSCs have been studied in healthy persons and osteoarthritic patients in order to explore its potential for treatment of some orthopedic disorders. Here, we briefly review the current knowledge on synovial fluid MSCs, their origin, relation to some orthopedic diseases, and future applications.

Fibroblast-like synoviocytes induce calcium mineral formation and deposition

Calcium crystals are present in the synovial fluid of 65%–100% patients with osteoarthritis (OA) and 20%–39% patients with rheumatoid arthritis (RA). This study sought to investigate the role of fibroblast-like synoviocytes (FLSs) in calcium mineral formation. We found that numerous genes classified in the biomineral formation process, including bone gamma-carboxyglutamate (gla) protein/osteocalcin, runt-related transcription factor 2, ankylosis progressive homolog, and parathyroid hormone-like hormone, were differentially expressed in the OA and RA FLSs. Calcium deposits were detected in FLSs cultured in regular medium in the presence of ATP and FLSs cultured in chondrogenesis medium in the absence of ATP. More calcium minerals were deposited in the cultures of OA FLSs than in the cultures of RA FLSs. Examination of the micromass stained with nonaqueous alcoholic eosin indicated the presence of birefringent crystals. Phosphocitrate inhibited the OA FLSs-mediated calcium mineral deposition. These findings together suggest that OA FLSs are not passive bystanders but are active players in the pathological calcification process occurring in OA and that potential calcification stimuli for OA FLSs-mediated calcium deposition include ATP and certain unidentified differentiation-inducing factor(s). The OA FLSs-mediated pathological calcification process is a valid target for the development of disease-modifying drug for OA therapy.

Death receptor 5-targeted depletion of interleukin-23-producing macrophages, Th17, and Th1/17 associated with defective tyrosine phosphatase in mice and patients with rheumatoid arthritis

OBJECTIVE

Bidirectional interactions between granulocyte-macrophage colony-stimulating factor-positive (GM-CSF+) T cells and interferon regulatory factor 5-positive (IRF-5+) macrophages play a major role in autoimmunity. In the absence of SH2 domain-containing phosphatase 1 (SHP-1), GM-CSF-stimulated cells are resistant to death receptor (DR)-mediated apoptosis. The objective of this study was to determine whether TRA-8, an anti-DR5 agonistic antibody, can eliminate inflammatory macrophages and CD4 T cells in the SHP-1-deficient condition.

METHODS

Ubiquitous Cre (Ubc.Cre) human/mouse-chimeric DR5-transgenic mice were crossed with viable SHP-1-defective motheaten (mev/mev) mice. TRA-8 was administered weekly for up to 4 weeks. The clinical scores, histopathologic severity, and macrophage and CD4 T cell phenotypes were evaluated. The role of TRA-8 in depleting inflammatory macrophages and CD4 T cells was also evaluated, using synovial fluid obtained from patients with rheumatoid arthritis (RA).

RESULTS

The levels of inflammatory macrophages (interleukin-23-positive [IL-23+] IRF-5+) and CD4 T cells (IL-17+ GM-CSF+) were elevated in mev/mev mice. In DR5-transgenic mev/mev mice, DR5 expression was up-regulated in these 2 cell populations. TRA-8 treatment depleted these cell populations and resulted in a significant reduction in inflammation and in the titers of autoantibodies. In synovial cells from patients with RA, the expression of IRF5 and DR5 was negatively correlated with the expression of PTPN6. TRA-8, but not TRAIL, suppressed RA inflammatory macrophages and Th17 cells under conditions in which the expression of SHP-1 is low.

CONCLUSION

In contrast to TRAIL, which lacks the capability to counteract the survival signal in the absence of SHP-1, TRA-8 eliminated both IRF-5+ IL-23+ M1 macrophages and pathogenic GM-CSF+ IL-17+ CD4 T cells in a SHP-1-independent manner. The results of the current study suggest that TRA-8 can deplete inflammatory cell populations that result from a hyperactive GM-CSF/IRF-5 axis.

Identification of the chondrocyte lineage using microfibril-associated glycoprotein-2, a novel marker that distinguishes chondrocytes from synovial cells

Methods for the lineage identification of cell or tissue-engineered therapeutics must provide a high degree of performance to confidently distinguish the intended cell type from other lineages that could be present in the finished product. For many applications, these methods also require rapid, high-throughput capability. In this work, methods for the identification of autologous cultured chondrocytes for implantation were investigated. A histological analysis confirmed that fibrous tissue occasionally present in biopsies procured for autologous chondrocyte implantation production comprised synovium. Chondrocyte and synovial cell cultures were then examined using a full transcriptome microarray analysis, which revealed cartilage link protein and microfibril-associated glycoprotein-2 (MAGP2) as the most differentially expressed transcripts between the culture types. Performance characteristics of gene expression assays formed by the analysis of cartilage link protein with normalization to either standard reference genes or to MAGP2 were evaluated. The results demonstrate that the MAGP2-based assay provided superior performance for the purpose of cell culture identification compared to assays using standard reference genes. The selectivity against synovial and heterogeneous samples provided by the novel assay suggests it as an appropriate lineage identification method for cell cultures derived from cartilage.

Phenotypic characterization and invasive properties of synovial fluid-derived adherent cells in rheumatoid arthritis

The present study aimed at characterizing the phenotype and functions of adherent synovial fluid (SF) cells derived from rheumatoid arthritis (RA), comparing with fibroblast-like synoviocytes (FLS) derived from RA synovial tissue (ST). Adherent SF-derived cells were spindle-shaped from passages 1-6 under light microscopy. The cell surface marker profile in SF-derived cells from passage 1-6 was similar to that of ST-derived FLS. Levels of MMP-1 and MMP-3 were not significantly different between SF-derived cells and ST-derived FLS (p = 0.20 and p = 0.40, respectively). There was no significant difference in the optical density value between two cell types in the cell invasion assay (p = 0.10). SF-derived adherent cells have a fibroblast-like phenotype from very early culture passages and have the potential to produce MMPs with the invasive capacity to degrade cartilage, identical to ST-derived FLS. Therefore, these cells could substitute for ST-derived FLS in studying the pathogenesis of RA.

Synovial fluid mesenchymal stem cells in health and early osteoarthritis: detection and functional evaluation at the single-cell level

OBJECTIVE

Arthritic synovial fluid (SF) contains mesenchymal stem cells (MSCs), which could simply reflect their shedding from diseased joint structures. This study used the bovine model to explore SF MSCs in health and enumerated them at the earliest stages of human osteoarthritis (OA) in radiographically normal joints.

METHODS

Clonogenicity and multipotentiality of normal bovine SF MSCs were compared with donor-matched bone marrow (BM) MSCs at the single-cell level. The colony-forming unit-fibroblastic assay was used for MSC enumeration. The XTT assay was employed to assess cell proliferation, and flow cytometry was used to investigate the marker phenotype of bovine and human SF MSCs.

RESULTS

Single MSCs were present in normal bovine SF, and 96% of them were able to expand at least 1 million-fold. These cells were CD271-, multipotential, considerably more clonogenic, and less adipogenic than matched BM MSCs. In both pellet assays and on polyglycolic acid scaffolds, SF clones displayed consistent chondrogenic differentiation, while BM clones were variable. MSCs were present in arthroscopically normal human joints and were increased 7-fold in early OA (P = 0.034). Their numbers correlated with numbers of free microscopic synovial tissue fragments (r = 0.826, P < 0.0001). OA SF had a growth-promoting effect on synovial MSCs.

CONCLUSION

This study confirms the presence of MSCs in normal SF and shows their numerical increase in early human OA. SF MSCs are likely to originate from synovium. These findings provide a platform for the exploration of the potential role of SF MSCs in joint homeostasis and for investigation of their utility in novel joint regeneration strategies.

A Novel Strategy for the Preparation of Naturally Occurring Phosphocitrate and Its Partially Esterified Derivatives

A novel method for the synthesis of phosphocitrate (1, PC) starting from triethyl ester of citric acid and MeOPCl2 is described. The method is based on selective stepwise hydrolysis of ester moieties from the intermediate Me-O-P(O)(Cl)(Z) (Z = triethylcitrate), 4a, which also allows one to prepare partially esterified derivatives of PC with good yield and purity without chromatographic purifications.