A meta-analysis and a functional study support the influence of mtDNA variant m.16519C on the risk of rapid progression of knee osteoarthritis.

OBJECTIVES: To identify mitochondrial DNA (mtDNA) genetic variants associated with the risk of rapid progression of knee osteoarthritis (OA) and to characterise their functional significance using a cellular model of transmitochondrial cybrids. METHODS: Three prospective cohorts contributed participants. The osteoarthritis initiative (OAI) included 1095 subjects, the Cohort Hip and Cohort Knee included 373 and 326 came from the PROspective Cohort of Osteoarthritis from A Coruña. mtDNA variants were screened in an initial subset of 450 subjects from the OAI by in-depth sequencing of mtDNA. A meta-analysis of the three cohorts was performed. A model of cybrids was constructed to study the functional consequences of harbouring the risk mtDNA variant by assessing: mtDNA copy number, mitochondrial biosynthesis, mitochondrial fission and fusion, mitochondrial reactive oxygen species (ROS), oxidative stress, autophagy and a whole transcriptome analysis by RNA-sequencing. RESULTS: mtDNA variant m.16519C is over-represented in rapid progressors (combined OR 1.546; 95% CI 1.163 to 2.054; p=0.0027). Cybrids with this variant show increased mtDNA copy number and decreased mitochondrial biosynthesis; they produce higher amounts of mitochondrial ROS, are less resistant to oxidative stress, show a lower expression of the mitochondrial fission-related gene fission mitochondrial 1 and an impairment of autophagic flux. In addition, its presence modulates the transcriptome of cybrids, especially in terms of inflammation, where interleukin 6 emerges as one of the most differentially expressed genes. CONCLUSIONS: The presence of the mtDNA variant m.16519C increases the risk of rapid progression of knee OA. Among the most modulated biological processes associated with this variant, inflammation and negative regulation of cellular process stand out. The design of therapies based on the maintenance of mitochondrial function is recommended.

Histone Extraction from Human Articular Cartilage for the Study of Epigenetic Regulation in Osteoarthritis.

Osteoarthritis (OA) is a chronic disease that affects articular cartilage, causing its degeneration. Although OA is one of the most prevalent pathologies globally, there are no definitive treatments available. Recently, research has focused on elucidating the complex interplay that takes place between inflammatory processes and epigenetic regulation, showing that histone post-translational modifications (PTMs) can exert a pronounced effect on the expression of OA-related genes. OA chondrocytes enhance the production of interleukin 1ß (IL-1ß) and interleukin 8 (IL-8), which are epigenetically regulated. These cytokines upregulate the synthesis of matrix metalloproteinases (MMPs) and aggrecanases, which promote the extracellular matrix (ECM) destruction. This motivates the study of histone PTMs to investigate the epigenetic regulation of proinflammatory molecules, but the absence of specific protocols to extract histones from human articular cartilage has complicated this task. The lack of effective methods can be explained by the structural complexity and low cellularity of this tissue, which are responsible for the biomechanical properties that allow the movement of the joint but also complicate histone isolation. Here, we provide a histone extraction procedure specifically adapted for cryopreserved human articular cartilage that can be useful to understand epigenetic regulation in OA and accelerate the search for novel strategies.

Mitochondrial DNA from osteoarthritic patients drives functional impairment of mitochondrial activity: a study on transmitochondrial cybrids.

With the redefinition of osteoarthritis (OA) and the understanding that the joint behaves as an organ, OA is now considered a systemic illness with a low grade of chronic inflammation. Mitochondrial dysfunction is well documented in OA and has the capacity to alter chondrocyte and synoviocyte function. Transmitochondrial cybrids are suggested as a useful cellular model to study mitochondrial biology in vitro, as they carry different mitochondrial variants with the same nuclear background. The aim of this work was to study mitochondrial and metabolic function of cybrids with mitochondrial DNA from healthy (N) and OA donors. In this work, the authors demonstrate that cybrids from OA patients behave differently from cybrids from N donors in several mitochondrial parameters. Furthermore, OA cybrids behave similarly to OA chondrocytes. These results enhance our understanding of the role of mitochondria in the degeneration process of OA and present cybrids as a useful model to study OA pathogenesis.

Generation of Mesenchymal Cell Lines Derived from Aged Donors.

Background: Mesenchymal stromal cells (MSCs) have the capacity for self-renewal and multi-differentiation, and for this reason they are considered a potential cellular source in regenerative medicine of cartilage and bone. However, research on this field is impaired by the predisposition of primary MSCs to senescence during culture expansion. Therefore, the aim of this study was to generate and characterize immortalized MSC (iMSC) lines from aged donors. Methods: Primary MSCs were immortalized by transduction of simian virus 40 large T antigen (SV40LT) and human telomerase reverse transcriptase (hTERT). Proliferation, senescence, phenotype and multi-differentiation potential of the resulting iMSC lines were analyzed. Results: MSCs proliferate faster than primary MSCs, overcome senescence and are phenotypically similar to primary MSCs. Nevertheless, their multi-differentiation potential is unbalanced towards the osteogenic lineage. There are no clear differences between osteoarthritis (OA) and non-OA iMSCs in terms of proliferation, senescence, phenotype or differentiation potential. Conclusions: Primary MSCs obtained from elderly patients can be immortalized by transduction of SV40LT and hTERT. The high osteogenic potential of iMSCs converts them into an excellent cellular source to take part in in vitro models to study bone tissue engineering.

Proteomic Analysis of Synovial Fibroblasts and Articular Chondrocytes Co-Cultures Reveals Valuable VIP-Modulated Inflammatory and Degradative Proteins in Osteoarthritis.

Osteoarthritis (OA) is the most common musculoskeletal disorder causing a great disability and a reduction in the quality of life. In OA, articular chondrocytes (AC) and synovial fibroblasts (SF) release innate-derived immune mediators that initiate and perpetuate inflammation, inducing cartilage extracellular matrix (ECM) degradation. Given the lack of therapies for the treatment of OA, in this study, we explore biomarkers that enable the development of new therapeutical approaches. We analyze the set of secreted proteins in AC and SF co-cultures by stable isotope labeling with amino acids (SILAC). We describe, for the first time, 115 proteins detected in SF-AC co-cultures stimulated by fibronectin fragments (Fn-fs). We also study the role of the vasoactive intestinal peptide (VIP) in this secretome, providing new proteins involved in the main events of OA, confirmed by ELISA and multiplex analyses. VIP decreases proteins involved in the inflammatory process (CHI3L1, PTX3), complement activation (C1r, C3), and cartilage ECM degradation (DCN, CTSB and MMP2), key events in the initiation and progression of OA. Our results support the anti-inflammatory and anti-catabolic properties of VIP in rheumatic diseases and provide potential new targets for OA treatment.

Effect of balneotherapy in sulfurous water on an in vivo murine model of osteoarthritis.

Osteoarthritis (OA) is a chronic joint disease that results in progressive cartilage destruction and subsequently joint dysfunction. Growing evidence indicates beneficial impact of balneological interventions in OA; however, their mechanisms of action are still unclear. Here, we evaluate the effect of balneotherapy in sulfurous water in an OA experimental model. Experimental OA was induced in Wistar rats by transection of the medial collateral ligament and removal of the medial meniscus of the left knee. Animals were randomized into three groups: non-treated (control) and balneotherapy using sulfurous water (SW) or tap water (TW). Macroscopic evaluation was performed, as well as evaluation of pain levels and analysis of motor function by rotarod test. Histopathological changes in articular cartilage and synovium were also evaluated. The presence of matrix metalloproteinase-13 (MMP-13) and oxidative damage markers was assessed by immunohistochemistry. Joint destabilization induced joint thickening, loss of joint flexion, and increased levels of pain. At day 40, animals from SW group presented lower pain levels than those from control group. Experimental OA also affected motor function. Balneotherapy in sulfur-rich water significantly improved joint mobility in relation to that in tap water. Besides, we observed that cartilage deterioration was lower in SW group than in the other two groups. Likewise, SW group showed reduced levels of MMP-13 in the cartilage. Conversely, we failed to observe any modulation on synovial inflammation. Finally, balneotherapy in sulfurous water diminished the presence of oxidative damage markers. Our results suggest the beneficial effect of balneotherapy in sulfur-rich water on an experimental model of OA, showing a reduced cartilage destruction and oxidative damage. Thus, these findings support the use of balneotherapy as a non-pharmacological treatment in OA.

Intraarticular Administration Effect of Hydrogen Sulfide on an In Vivo Rat Model of Osteoarthritis.

Osteoarthritis (OA) is the most common articular chronic disease. However, its current treatment is limited and mostly symptomatic. Hydrogen sulfide (H2S) is an endogenous gas with recognized physiological activities. The purpose here was to evaluate the effects of the intraarticular administration of a slow-releasing H2S compound (GYY-4137) on an OA experimental model. OA was induced in Wistar rats by the transection of medial collateral ligament and the removal of the medial meniscus of the left joint. The animals were randomized into three groups: non-treated and intraarticularly injected with saline or GYY-4137. Joint destabilization induced articular thickening (≈5% increment), the loss of joint mobility and flexion (≈12-degree angle), and increased levels of pain (≈1.5 points on a scale of 0 to 3). Animals treated with GYY-4137 presented improved motor function of the joint, as well as lower pain levels (≈75% recovery). We also observed that cartilage deterioration was attenuated in the GYY-4137 group (≈30% compared with the saline group). Likewise, these animals showed a reduced presence of pro-inflammatory mediators (cyclooxygenase-2, inducible nitric oxide synthase, and metalloproteinase-13) and lower oxidative damage in the cartilage. The increment of the nuclear factor-erythroid 2-related factor 2 (Nrf-2) levels and Nrf-2-regulated gene expression (≈30%) in the GYY-4137 group seem to be underlying its chondroprotective effects. Our results suggest the beneficial impact of the intraarticular administration of H2S on experimental OA, showing a reduced cartilage destruction and oxidative damage, and supporting the use of slow H2S-producing molecules as a complementary treatment in OA.

Wnt and RUNX2 mediate cartilage breakdown by osteoarthritis synovial fibroblast-derived ADAMTS-7 and -12.

Failure of therapeutic approaches for the treatment of osteoarthritis (OA) based on the inhibition of metalloproteinases, might be because of their constitutive expression in homeostasis, together with their network complexity. The knowledge of this network would contribute to selective target pathological conditions. In this sense, blockade of mediators produced by neighbouring joint cells, such as synovial fibroblasts (SF), would prevent cartilage damage. Thus, we studied the contribution of ADAMTS-7 and -12 from SF to cartilage oligomeric matrix protein (COMP) degradation, and the signalling pathways involved in their expression. We report for the first time in SF, the involvement of ERK-Runx2 axis and Wnt/ß-catenin signalling in ADAMTS-12 and ADAMTS-7 expressions, respectively, with the subsequent consequences in COMP degradation from cartilage extracellular matrix. After stimulation with IL-1ß or fibronectin fragments, we showed that ERK inhibition decreased Runx2 activation and ADAMTS-12 expression in OA-SF, also reducing Fn-fs-induced COMP degradation. Blockage of Wnt signalling by DKK1 reduced ADAMTS-7 and COMP degradation in OA-SF as well. In addition, Wnt7B expression was induced by IL-1ß and by itself, also increasing ADAMTS-7. Our results could contribute to the development of disease-modifying OA drugs targeting ADAMTS-7 and -12 for the prevention of extracellular matrix components degradation like COMP.

Mitochondrial DNA haplogroups influence the risk of incident knee osteoarthritis in OAI and CHECK cohorts. A meta-analysis and functional study.

OBJECTIVE: To evaluate the influence of the mitochondrial DNA (mtDNA) haplogroups in the risk of incident knee osteoarthritis (OA) and to explain the functional consequences of this association to identify potential diagnostic biomarkers and therapeutic targets. METHODS: Two prospective cohorts contributed participants. The osteoarthritis initiative (OAI) included 2579 subjects of the incidence subcohort, and the cohort hip and cohort knee (CHECK) included 635, both with 8-year follow-up. The analysis included the association of mtDNA haplogroups with the rate of incident knee OA in subjects from both cohorts followed by a subsequent meta-analysis. Transmitochondrial cybrids harbouring haplogroup J or H were constructed to detect differences between them in relation to physiological features including specific mitochondrial metabolic parameters, reactive oxygen species production, oxidative stress and apoptosis. RESULTS: Compared with H, the haplogroup J associates with decreased risk of incident knee OA in subjects from OAI (HR=0.680; 95% CI 0.470 to 0.968; p<0.05) and CHECK (HR=0.728; 95% CI 0.469 to 0.998; p<0.05). The subsequent meta-analysis including 3214 cases showed that the haplogroup J associates with a lower risk of incident knee OA (HR=0.702; 95% CI 0.541 to 0.912; p=0.008). J cybrids show a lower free radical production, higher cell survival under oxidative stress conditions, lower grade of apoptosis as well as lower expression of the mitochondrially related pro-apoptotic gene BCL2 binding component 3 (BBC3). In addition, J cybrids also show a lower mitochondrial respiration and glycolysis leading to decreased ATP production. CONCLUSIONS: The physiological effects of the haplogroup J are beneficial to have a lower rate of incident knee OA over time. Potential drugs to treat OA could focus on emulating the mitochondrial behaviour of this haplogroup.

Human Cartilage Engineering in an In Vitro Repair Model Using Collagen Scaffolds and Mesenchymal Stromal Cells.

The purpose of this study was to investigate cartilage repair of in vitro lesion models using human bone marrow mesenchymal stromal cells (hBMSCs) with different collagen (Col) scaffolds. Lesions were made in human cartilage biopsies. Injured samples were pre-treated with interleukin 1ß (IL1ß) for 24 h; also, samples were not pre-treated. hBMSCs were seeded on different types of collagen scaffolds. The resulting constructs were placed into the lesions, and the biopsies were cultured for 2 months in chondrogenic medium. Using the modified ICRSII scale, neotissues from the different scaffolds showed ICRS II overall assessment scores ranging from 50% (fibrocartilage) to 100% (hyaline cartilage), except for the Col I +Col II +HS constructs (fibrocartilage/hyaline cartilage, 73%). Data showed that hBMSCs cultured only on Col I +Col II +HS scaffolds displayed a chondrocyte-like morphology and cartilage-like matrix close to native cartilage. Furthermore, IL1ß pre-treated biopsies decreased capacity for repair by hBMSCs and decreased levels of chondrogenic phenotype of human cartilage lesions.

Alternative protocols to induce chondrogenic differentiation: transforming growth factor-ß superfamily.

Mesenchymal stem cells (MSCs) are an accepted candidate for cell-based therapy of multiple diseases. The interest in MSCs and their possible application in cell therapy have resulted in a better understanding of the basic biology of these cells. Recently, like aggregation and transforming growth factor beta (TGFß) delivery, hypoxia has been indicated as crucial for complete chondrogenesis. The aim of this study was to test different culture conditions for directing stem cell differentiation into the chondrogenic lineage in vitro by testing different TGFß superfamily members into the culture media under normoxic conditions. All chondrogenic culture conditions used allowed the differentiation of bone marrow-MSCs (BM-MSCs) into chondrogenic lineage. Chondrogenic induction capacity depended on the growth factor added to the culture media. In particular, the chondrogenic culture condition that better induced chondrogenesis was the medium that included the combination of three growth factors: bone morphogenetic protein-2 (BMP-2), BMP-7 and TGFß-3. In this culture media, differentiated cells showed the highest levels expression of two markers of chondrogenesis, SOX9 and COL2A1, compared to the control points (p < 0.05, two-tailed t test). In our experimental conditions, the combination of BMP-2, BMP-7 and TGFß-3 was the most effective in promoting chondrogenesis of BM-MSCs. These results underline the importance of determining in each experimental design the best protocol for in vitro directing stem cell differentiation into the chondrogenic lineage.

Anti-Inflammatory Activity of APPA (Apocynin and Paeonol) in Human Articular Chondrocytes.

Osteoarthritis (OA) is a chronic joint disease leading to cartilage loss and reduction in the joint space which results in pain. The current pharmacological treatment of OA is inadequate and pharmacological interventions focus on symptom management. APPA, a combination of apocynin (AP) and paeonol (PA), is a potential drug for treating OA. The aim of this study was to analyze the effects of APPA on the modulation of the inflammatory response in chondrocytes. Samples were incubated with IL-1ß and APPA, and their responses to proinflammatory cytokines, catabolic mediators and redox responses were then measured. The effect of APPA on mitogenesis was also evaluated. Results show that APPA attenuated the expression of IL-8, TNF-α, MMP-3, MMP-13, SOD-2 and iNOS, resulting in the protection of human articular cartilage. APPA decreased PGC-1α gene expression induced by IL-1ß. APPA did not modulate the gene expression of Mfn2, Sirt-1 or Sirt-3. The overall findings indicate that APPA may be an effective treatment for OA by targeting several of the pathways involved in OA pathogenesis.

Mitochondrial Role on Cellular Apoptosis, Autophagy, and Senescence during Osteoarthritis Pathogenesis.

Authors have demonstrated that apoptosis activation is a pathway related to cartilage degradation characteristics of the OA process. Autophagy is an adaptive response to protect cells from various environmental changes, and defects in autophagy are linked to cell death. In this sense, decreased autophagy of chondrocytes has been observed in OA articular cartilage. The aim of this work was to study the role of OA mitochondria in apoptosis, autophagy, and senescence, using OA and Normal (N) transmitochondrial cybrids. Results: OA cybrids incubated with menadione showed a higher percentage of late apoptosis and necrosis than N cybrids. Stimulation of cybrids with staurosporine and IL-1ß showed that OA cybrids were more susceptible to undergoing apoptosis than N cybrids. An analysis of the antioxidant response using menadione on gene expression revealed a lower expression of nuclear factor erythroid 2-like 2 and superoxide dismutase 2 in OA than N cybrids. Activation of microtubule-associated protein 1A/1B-light chain 3 was reduced in OA compared to N cybrids. However, the percentage of senescent cells was higher in OA than N cybrids. Conclusion: This work suggests that mitochondria from OA patients could be involved in the apoptosis, autophagy, and senescence of chondrocytes described in OA cartilage.

Generation of human immortalized chondrocytes from osteoarthritic and healthy cartilage : a new tool for cartilage pathophysiology studies.

AIMS: After a few passages of in vitro culture, primary human articular chondrocytes undergo senescence and loss of their phenotype. Most of the available chondrocyte cell lines have been obtained from cartilage tissues different from diarthrodial joints, and their utility for osteoarthritis (OA) research is reduced. Thus, the goal of this research was the development of immortalized chondrocyte cell lines proceeded from the articular cartilage of patients with and without OA. METHODS: Using telomerase reverse transcriptase (hTERT) and SV40 large T antigen (SV40LT), we transduced primary OA articular chondrocytes. Proliferative capacity, degree of senescence, and chondrocyte surface antigen expression in transduced chondrocytes were evaluated. In addition, the capacity of transduced chondrocytes to synthesize a tissue similar to cartilage and to respond to interleukin (IL)-1ß was assessed. RESULTS: Coexpression of both transgenes (SV40 and hTERT) were observed in the nuclei of transduced chondrocytes. Generated chondrocyte cell lines showed a high proliferation capacity and less than 2% of senescent cells. These cell lines were able to form 3D aggregates analogous to those generated by primary articular chondrocytes, but were unsuccessful in synthesizing cartilage-like tissue when seeded on type I collagen sponges. However, generated chondrocyte cell lines maintained the potential to respond to IL-1ß stimulation. CONCLUSION: Through SV40LT and hTERT transduction, we successfully immortalized chondrocytes. These immortalized chondrocytes were able to overcome senescence in vitro, but were incapable of synthesizing cartilage-like tissue under the experimental conditions. Nonetheless, these chondrocyte cell lines could be advantageous for OA investigation since, similarly to primary articular chondrocytes, they showed capacity to upregulate inflammatory mediators in response to the IL-1ß cytokine.Cite this article: Bone Joint Res 2023;12(1):46-57.

Characterization of microRNA expression profiles in normal and osteoarthritic human chondrocytes.

BACKGROUND: Osteoarthritis (OA) is a multifactorial disease characterized by destruction of the articular cartilage due to environmental, mechanical and genetic components. The genetics of OA is complex and is not completely understood. Recent works have demonstrated the importance of microRNAs (miRNAs) in cartilage function. MiRNAs are a class of small noncoding RNAs that regulate gene expression and are involved in different cellular process: apoptosis, proliferation, development, glucose and lipid metabolism. The aim of this study was to identify and characterize the expression profile of miRNAs in normal and OA chondrocytes and to determine their role in the OA. METHODS: Chondrocytes were moved to aggregate culture and evaluated using histological and qPCR techniques. miRNAs were isolated and analyzed using the Agilent Human miRNA Microarray. RESULTS: Of the 723 miRNAs analyzed, 7 miRNAs showed a statistically significant differential expression. Amongst these 7 human miRNAs, 1 was up-regulated in OA chondrocytes (hsa-miR-483-5p) and 6 were up-regulated in normal chondrocytes (hsa-miR-149*, hsa-miR-582-3p, hsa-miR-1227, hsa-miR-634, hsa-miR-576-5p and hsa-miR-641). These profiling results were validated by the detection of some selected miRNAs by qPCR. In silico analyses predicted that key molecular pathways potentially altered by the miRNAs differentially expressed in normal and OA chondrocytes include TGF-beta, Wnt, Erb and mTOR signalling; all of them implicated in the development, maintenance and destruction of articular cartilage. CONCLUSIONS: We have identified 7 miRNAs differentially expressed in OA and normal chondrocytes. Our potential miRNA target predictions and the signalling cascades altered by the differentially expressed miRNAs supports the potential involvement of the detected miRNAs in OA pathology. Due to the importance of miRNA in mediating the translation of target mRNA into protein, the identification of these miRNAs differentially expressed in normal and OA chondrocyte micropellets could have important diagnostic and therapeutic potential. Further studies are needed to know the function of these miRNAs, including the search of their target mRNA genes, which could lead to the development of novel therapeutic strategies for the OA treatment.

Human amniotic membrane as an alternative source of stem cells for regenerative medicine.

The human amniotic membrane (HAM) is a highly abundant and readily available tissue. This amniotic tissue has considerable advantageous characteristics to be considered as an attractive material in the field of regenerative medicine. It has low immunogenicity, anti-inflammatory properties and their cells can be isolated without the sacrifice of human embryos. Since it is discarded post-partum it may be useful for regenerative medicine and cell therapy. Amniotic membranes have already been used extensively as biologic dressings in ophthalmic, abdominal and plastic surgery. HAM contains two cell types, from different embryological origins, which display some characteristic properties of stem cells. Human amnion epithelial cells (hAECs) are derived from the embryonic ectoderm, while human amnion mesenchymal stromal cells (hAMSCs) are derived from the embryonic mesoderm. Both populations have similar immunophenotype and multipotential for in vitro differentiation into the major mesodermal lineages, however they differ in cell yield. Therefore, HAM has been proposed as a good candidate to be used in cell therapy or regenerative medicine to treat damaged or diseased tissues.

Reduced Levels of H2S in Diabetes-Associated Osteoarthritis Are Linked to Hyperglycaemia, Nrf-2/HO-1 Signalling Downregulation and Chondrocyte Dysfunction.

Different findings indicate that type 2 diabetes is an independent risk factor for osteoarthritis (OA). However, the mechanisms underlying the connection between both diseases remain unclear. Changes in the balance of hydrogen sulphide (H2S) are thought to play an important role in the pathogenesis of diabetes and its complications, although its role is still controversial. In this study, we examined the modulation of H2S levels in serum and chondrocytes from OA diabetic (DB) and non-diabetic (non-DB) patients and in cells under glucose stress, in order to elucidate whether impairment in H2S-mediated signalling could participate in the onset of DB-related OA. Here, we identified a reduction in H2S synthesis in the cartilage from OA-DB patients and in cells under glucose stress, which is associated with hyperglycaemia-mediated dysregulation of chondrocyte metabolism. In addition, our results indicate that H2S is an inductor of the Nrf-2/HO-1 signalling pathway in cartilage, but is also a downstream target of Nrf-2 transcriptional activity. Thereby, impairment of the H2S/Nrf-2 axis under glucose stress or DB triggers chondrocyte catabolic responses, favouring the disruption of cartilage homeostasis that characterizes OA pathology. Finally, our findings highlight the benefits of the use of exogeneous sources of H2S in the treatment of DB-OA patients, and warrant future clinical studies.

Molecular profile and cellular characterization of human bone marrow mesenchymal stem cells: donor influence on chondrogenesis.

BACKGROUND: The use of autologous or allogenic stem cells has recently been suggested as an alternative therapeutic approach for treatment of cartilage defects. Bone marrow mesenchymal stem cells (BM-MSCs) are well-characterized multipotent cells that can differentiate into different cell types. Understanding the potential of these cells and the molecular mechanisms underlying their differentiation should lead to innovative protocols for clinical applications. The aim of this study was to evaluate the usefulness of surface antigen selection of BM-MSCs and to understand the mechanisms underlying their differentiation. METHODS: MSCs were isolated from BM stroma and expanded. CD105+ subpopulation was isolated using a magnetic separator. We compared culture-expanded selected cells with non-selected cells. We analyzed the phenotypic profiles, the expression of the stem cell marker genes Nanog, Oct3/4, and Sox2 and the multi-lineage differentiation potential (adipogenic, osteogenic, and chondrogenic). The multi-lineage differentiation was confirmed using histochemistry, immunohistochemistry and/or real-time polymerase chain reaction (qPCR) techniques. RESULTS: The selected and non-selected cells displayed similar phenotypes and multi-lineage differentiation potentials. Analyzing each cell source individually, we could divide the six donors into two groups: one with a high percentage of CD29 (ß1-integrin) expression (HL); one with a low percentage of CD29 (LL). These two groups had different chondrogenic capacities and different expression levels of the stem cell marker genes. CONCLUSIONS: This study showed that phenotypic profiles of donors were related to the chondrogenic potential of human BM-MSCs. The chondrogenic potential of donors was related to CD29 expression levels. The high expression of CD29 antigen seemed necessary for chondrogenic differentiation. Further investigation into the mechanisms responsible for these differences in BM-MSCs chondrogenesis is therefore warranted. Understanding the mechanisms for these differences will contribute to improved clinical use of autologous human BM-MSCs for articular cartilage repair.

Multilineage differentiation potential of cells isolated from the human amniotic membrane.

The human amniotic membrane (HAM) contains two cell types from different embryological origins. Human amnion epithelial cells (hAECs) are derived from the embryonic ectoderm, while human amnion mesenchymal stromal cells (hAMSCs) are derived from the embryonic mesoderm. In this study, we localized, isolated, quantified and phenotypically characterized HAM-derived cells and analysed their in vitro differentiation potential towards mesodermal cell lineages. Human amnion-derived cells were isolated and characterized by flow cytometry. Immunohistochemistry and quantitative real-time reverse transcription-polymerase chain reaction studies were performed for the analysis of multipotentiality. Immunophenotypic characterization of both cell types demonstrated the presence of the common, well-defined human mesenchymal stem cell (MSC) markers (CD90, CD44, CD73, CD166, CD105, CD29), as well as the embryonic stem-cell markers SSEA-4 and STRO-1. Phenotypes of both cell populations were maintained from passages P0 to P9. The assessment of multilineage potential demonstrated that the hAMSCs showed greater adipogenic and chondrogenic potential. Both populations had the ability to retain their capacity for differentiation during culture passages from P0 to P4. Our data demonstrate the successful localization and isolation of hAMSCs and hAECs from the HAM. Both cell populations possessed similar immunophenotype. However, they differed in cell yield and multipotential for differentiation into the major mesodermal lineages. Our functional differentiation studies demonstrated that hAMSCs possess a much greater mesodermal differentiation capacity than hAECs. These considerations will be important for use of these cells for cell therapy.

Potential use of the human amniotic membrane as a scaffold in human articular cartilage repair.

The human amniotic membrane (HAM) is an abundant and readily obtained tissue that may be an important source of scaffold for transplanted chondrocytes in cartilage regeneration in vivo. To evaluate the potential use of cryopreserved HAMs as a support system for human chondrocytes in human articular cartilage repair. Chondrocytes were isolated from human articular cartilage, cultured and grown on the chorionic basement membrane side of HAMs. HAMs with chondrocytes were then used in 44 in vitro human osteoarthritis cartilage repair trials. Repair was evaluated at 4, 8 and 16 weeks by histological analysis. Chondrocytes cultured on the HAM revealed that cells grew on the chorionic basement membrane layer, but not on the epithelial side. Chondrocytes grown on the chorionic side of the HAM express type II collagen but not type I, indicating that after being in culture for 3-4 weeks they had not de-differentiated into fibroblasts. In vitro repair experiments showed formation on OA cartilage of new tissue expressing type II collagen. Integration of the new tissue with OA cartilage was excellent. The results indicate that cryopreserved HAMs can be used to support chondrocyte proliferation for transplantation therapy to repair OA cartilage.