RNA Extraction from Cartilage: Issues, Methods, Tips.

The increase in degenerative diseases involving articular cartilage has pushed research to focus on their pathogenesis and treatment, exploiting increasingly complex techniques. Gene expression analyses from tissue are representative of the in vivo situation, but the protocols to be applied to obtain a reliable analysis are not completely cleared through customs. Thus, RNA extraction from fresh samples and specifically from musculoskeletal tissue such as cartilage is still a challenging issue. The aim of the review is to provide an overview of the techniques described in the literature for RNA extraction, highlighting limits and possibilities. The research retrieved 65 papers suitable for the purposes. The results highlighted the great difficulty in comparing the different studies, both for the sources of tissue used and for the techniques employed, as well as the details about protocols. Few papers compared different RNA extraction methods or homogenization techniques; the case study reported by authors about RNA extraction from sheep cartilage has not found an analog in the literature, confirming the existence of a relevant blank on studies about RNA extraction from cartilage tissue. However, the state of the art depicted can be used as a starting point to improve and expand studies on this topic.

Gender-Specific Differences in Human Vertebral Bone Marrow Clot.

Recently, our group described the application of vertebral bone marrow (vBMA) clot as a cell therapy strategy for spinal fusion. Its beneficial effects were confirmed in aging-associated processes, but the influence of gender is unknown. In this study, we compared the biological properties of vBMA clots and derived vertebral mesenchymal stem cells (MSCs) from female and male patients undergoing spinal fusion procedures and treated with vBMA clot. We analyzed the expression of growth factors (GFs) in vBMA clots and MSCs as well as morphology, viability, doubling time, markers expression, clonogenicity, differentiation ability, senescence factors, Klotho expression, and HOX and TALE gene profiles from female and male donors. Our findings indicate that vBMA clots and derived MSCs from males had higher expression of GFs and greater osteogenic and chondrogenic potential compared to female patients. Additionally, vBMA-clot-derived MSCs from female and male donors exhibited distinct levels of HOX and TALE gene expression. Specifically, HOXA1, HOXB8, HOXD9, HOXA11, and PBX1 genes were upregulated in MSCs derived from clotted vBMA from male donors. These results demonstrate that vBMA clots can be effectively used for spinal fusion procedures; however, gender-related differences should be taken into consideration when utilizing vBMA-clot-based studies to optimize the design and implementation of this cell therapy strategy in clinical trials.

Human Osteoblasts' Response to Biomaterials for Subchondral Bone Regeneration in Standard and Aggressive Environments.

Osteochondral lesions, when not properly treated, may evolve into osteoarthritis (OA), especially in the elderly population, where altered joint function and quality are usual. To date, a collagen/collagen-magnesium-hydroxyapatite (Col/Col-Mg-HAp) scaffold (OC) has demonstrated good clinical results, although suboptimal subchondral bone regeneration still limits its efficacy. This study was aimed at evaluating the in vitro osteogenic potential of this scaffold, functionalized with two different strategies: the addition of Bone Morphogenetic Protein-2 (BMP-2) and the incorporation of strontium (Sr)-ion-enriched amorphous calcium phosphate (Sr-ACP) granules. Human osteoblasts were seeded on the functionalized scaffolds (OC+BMP-2 and OC+Sr-ACP, compared to OC) under stress conditions reproduced with the addition of H2O2 to the culture system, as well as in normal conditions, and evaluated in terms of morphology, metabolic activity, gene expression, and matrix synthesis. The OC+BMP-2 scaffold supported a better osteoblast morphology and stimulated scaffold colonization, cell activity, and extracellular matrix secretion, especially in the stressed culture environment but also in normal culture conditions, with increased expression of genes related to osteoblast differentiation. In conclusion, the incorporation of BMP-2 into the Col/Col-Mg-HAp scaffold also represents an improvement of the osteochondral scaffold in more challenging conditions, supporting further preclinical studies to optimize it for use in clinical practice.

Evaluating Mentors in Violence Prevention: A Longitudinal, Multilevel Assessment of Outcome Changes.

There is a need to increase understanding of the effectiveness of bystander programmes targeting gender-based violence in the United Kingdom. There is also a need to utilise a robust theoretical models of decision-making while doing so. Changes were examined in bystanders' attitudes, beliefs, motivations towards intervening, and intervention behavior in situations of gender-based violence. To achieve this, a quantitative examination of Mentors in Violence Prevention was conducted. There were 1396 participants (50% female, 50% male) who were aged 11 to 14 years old (M = 12.25, SD = 0.84) attending high school at the first time point. Participants were attending 17 schools (53% Mentors in Violence Prevention and 47% control) in Scotland. Outcome variables were assessed approximately one year apart using questionnaires. Multilevel linear regressions revealed that Mentors in Violence Prevention did not change outcomes reflecting bystanders' attitudes, beliefs, motivations towards intervening, or intervention behavior in gender-based violence. Discrepancies between the current findings and those of other evaluations may be due to other studies including small numbers of schools that may be more motivated to implement the program. This study also identified two key issues that need to be addressed at stakeholder level before concluding that Mentors in Violence Prevention is ineffective at targeting gender-based violence. That the program has moved towards a more gender-neutral approach in the United Kingdom could explain the null results of this study. Furthermore, the current findings could be attributed to a failure to adequately address the theoretical model underpinning the program in practice.

A Social-Ecological Approach to Understanding Adolescent Sexting Behavior.

This study examined the extent to which active and passive sexting behaviors are associated with family-, school-, peer-, and romantic-level variables. Young people (N = 3,322; 49.1% female, 48.3% male, 2.6% other) aged 11 to 15 years old (M = 12.84, SD = 0.89) took part, and all attended mainstream secondary schools in Scotland. Participants completed self-report measures of school connectedness, parental love and support, perceived susceptibility to peer- and romantic-pressure (e.g., to display behaviors just to impress others), and their involvement in active and passive sexting. The importance of both school- and family-level factors was evident, though perceived romantic-pressure had the largest effect. However, neither school- nor family-level variables were moderated by either perceived romantic-pressure or perceived peer-pressure. Efforts to reduce sexting or increase its safety should primarily seek to tackle young people's ability to respond effectively to romantic-pressure. It may also be helpful to develop school connectedness and to help families provide support that is constructive and not intrusive.

Vascular Supply and Bone Marrow Concentrate for the Improvement of Allograft in Bone Defects: A Comparative In Vivo Study.

BACKGROUND: Surgical repair of critical-sized bone defects still remains a big challenge in orthopedic surgery. Biological enhancement, such as growth factors or cells, can stimulate a better outcome in bone regeneration driven by well-established treatments such as allogenic bone graft. However, despite the surgical options available, correct healing can be slowed down or compromised by insufficient vascular supply to the injured site. MATERIALS AND METHODS: In this pilot study, critical size bone defects in rabbit radius were treated with allograft bone, in combination with vascular bundle and autologous bone marrow concentrate seeded onto a commercial collagen scaffold. Microtomographical, histological and immunohistochemical assessments were performed to evaluate allograft integration and bone regeneration. RESULTS: Results showed that the surgical deviation of vascular bundle in the bone graft, regardless from the addition of bone marrow concentrate, promote the onset of healing process at short experimental times (8 wk) in comparison with the other groups, enhancing graft integration. CONCLUSION: The surgical procedure tested stimulates bone healing at early times, preserving native bone architecture, and can be easily combined with biological adjuvant.

An advanced tri-culture model to evaluate the dynamic interplay among osteoblasts, osteoclasts, and endothelial cells.

The dynamic metabolism and the numerous roles of bone tissue necessitate a suitable in vitro model to represent them. In order to investigate the interaction among the several cell types composing bone microenvironment, we studied a tri-culture model including human osteoblasts (OBs), osteoclasts (OCs), and endothelial cells (HUVEC). While OBs are essential for bone deposition and OCs for bone resorption, the vasculature is necessary to provide growth factors, nutrients, and oxygen in the mature tissue. The results of this study showed a strong mutual influence between OBs, OCs, and HUVEC in term of proliferation, viability, and activity (release of ALP, Coll I, OPG, RANKL, VEGF, CTSK, TGFß, and IL-6). The behavior of the single cultures demonstrated to be different compared to the bi- or tri-cultures and depending on the cell types involved: the coexistence of OBs and OCs stimulated the synthetic activity of both cell types, while the presence of HUVEC induced a stimulating role for OBs but mainly an inhibitory effect for OC. In addition, evidence of the effects of OBs and OCs on HUVEC is highlighted by their morphology: regular and able to "sketch" little vessels in presence of OBs, more disorganized and heterogeneous in presence of OCs. Taken together, these observations well characterize an advanced cellular model to be used as starting point for mimicking bone microenvironment in vivo, thus reducing the use of animals in the preclinical phase and offering a more reliable tool to test new and innovative biomaterials.

Osteogenic commitment and differentiation of human mesenchymal stem cells by low-intensity pulsed ultrasound stimulation.

Low-intensity pulsed ultrasound (LIPUS) as an adjuvant therapy in in vitro and in vivo bone engineering has proven to be extremely useful. The present study aimed at investigating the effect of 30 mW/cm2 LIPUS stimulation on commercially available human mesenchymal stem cells (hMSCs) cultured in basal or osteogenic medium at different experimental time points (7, 14, 21 days). The hypothesis was that LIPUS would improve the osteogenic differentiation of hMSC and guarantying the maintenance of osteogenic committed fraction, as demonstrated by cell vitality and proteomic analysis. LIPUS stimulation (a) regulated the balance between osteoblast commitment and differentiation by specific networks (activations of RhoA/ROCK signaling and upregulation of Ribosome constituent/Protein metabolic process, Glycolysis/Gluconeogenesis, RNA metabolic process/Splicing and Tubulins); (b) allowed the maintenance of a few percentage of osteoblast precursors (21 days CD73+/CD90+: 6%; OCT-3/4+/NANOG+/SOX2+: 10%); (c) induced the activation of osteogenic specific pathways shown by gene expression (early: ALPL, COL1A1, late: RUNX2, BGLAP, MAPK1/6) and related protein release (COL1a1, OPN, OC), in particular in the presence of osteogenic soluble factors able to mimic bone microenvironment. To summarize, LIPUS might be able to improve the osteogenic commitment of hMSCs in vitro, and, at the same time, enhance their osteogenic differentiation.

Uremic Serum Impairs Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stromal Cells.

Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) is characterized by an increased fracture risk. Bone marrow mesenchymal stromal cells (BMSCs) may be involved in the pathogenesis of bone disease and, in view of their promising potential applications in bone tissue engineering, the effect of uremia on BMSCs regenerative potential represents a central issue. The present study evaluated in vitro the effect of a serum pool from hemodialysis patients on BMSCs to observe its influence on osteogenic differentiation. Besides alterations in spatial organization and cytotoxicity along with hyperproliferation, gene expression analysis suggested an impairment in the osteogenic differentiation. More importantly, Receptor activator of nuclear factor kappa-B ligand (RANKL) was upregulated with a mild reduction in osteoprotegerin levels. In summary, uremic environment seems to impair BMSCs osteogenic differentiation. Moreover BMSCs themselves may enhance osteoclastogenesis, feasibly contributing to the altered bone remodeling in CKD-MBD patients. J. Cell. Physiol. 232: 2201-2209, 2017. © 2016 Wiley Periodicals, Inc.

Increased Chondrogenic Potential of Mesenchymal Cells From Adipose Tissue Versus Bone Marrow-Derived Cells in Osteoarthritic In Vitro Models.

Primarily, to compare the behavior of human mesenchymal stem cells (MSCs) derived from bone marrow (hBMSCs) and adipose tissue (hADSCs) in an osteoarthritic (OA) microenvironment; secondly, to investigate the reaction of these cell types in two alternative in vitro culture systems, obtained by using TNFα and/or IL1ß as inflammation mediators, or by using synovial fluid harvested by OA patients (OSF) to simulate the complex inflamed knee microenvironment. 3D micromass cultures of hBMSCs or hADSCs were grown in chondrogenic medium (CTR), in the presence of TNFα and/or IL1ß, or synovial fluid from OA patients. After 1 month of culture, the chondrogenic differentiation of micromasses was evaluated by gene expression, matrix composition, and organization. Both hMSCs types formed mature micromasses in CTR, but a better response of hADSCs to the inflammatory environment was documented by micromass area and Bern score evaluations. The addition of OSF elicited a milder reaction than with TNFα and/or IL1ß by both cell types, probably due to the presence of both catabolic and protective factors. In particular, SOX9 and ACAN gene expression and GAG synthesis were more abundant in hADSCs than hBMSCs when cultured in OSF. The expression of MMP1 was increased for both hMSCs in inflammatory conditions, but in particular by hBMSCs. hADSCs showed an increased chondrogenic potential in inflammatory culture systems, suggesting a better response of hADSCs in the OA environment, thus underlining the importance of appropriate in vitro models to study MSCs and potential advantages of using these cells for future clinical applications. J. Cell. Physiol. 232: 1478-1488, 2017. © 2016 Wiley Periodicals, Inc.

Vitamin D Level Between Calcium-Phosphorus Homeostasis and Immune System: New Perspective in Osteoporosis.

Vitamin D is a key molecule in calcium and phosphate homeostasis; however, increasing evidence has recently shown that it also plays a crucial role in the immune system, both innate and adaptive. A deregulation of vitamin D levels, due also to mutations and polymorphisms in the genes of the vitamin D pathway, determines severe alterations in the homeostasis of the organism, resulting in a higher risk of onset of some diseases, including osteoporosis. This review gives an overview of the influence of vitamin D levels on the pathogenesis of osteoporosis, between bone homeostasis and immune system.

Effect of adipose-derived mesenchymal stromal cells on tendon healing in aging and estrogen deficiency: an in vitro co-culture model.

BACKGROUND AIMS: Aging and estrogen deficiency play a pivotal role in reducing tenocyte proliferation, collagen turnover and extracellular matrix remodeling. Mesenchymal stromal cells are being studied as an alternative for tendon regeneration, but little is known about the molecular events of adipose-derived mesenchymal stromal cells (ADSCs) on tenocytes in tendons compromised by aging and estrogen deficiency. The present in vitro study aims to compare the potential therapeutic effects of ADSCs, harvested from healthy young (sham) and aged estrogen-deficient (OVX) subjects, for tendon healing. METHODS: An indirect co-culture system was set up with ADSCs, isolated from OVX or sham rats, and tenocytes from OVX rats. Cell proliferation, healing rate and gene expression were evaluated in both a standard culture condition and a microwound-healing model. RESULTS: It was observed that tenocyte proliferation, healing rate and collagen expression improved after the addition of sham ADSCs in both culture situations. OVX ADSCs also increased tenocyte proliferation and healing rate but less compared with sham ADSCs. Decorin and Tenascin C expression increased in the presence of OVX ADSCs. CONCLUSIONS: Findings suggest that ADSCs might be a promising treatment for tendon regeneration in advanced age and estrogen deficiency. However, some differences between allogenic and autologous cells were found and should be investigated in further in vivo studies. It appears that allogenic ADSCs improve tenocyte proliferation, collagen expression and the healing rate more than autologous cells. Autologous cells increase collagen expression only in the absence of an injury and increase Decorin and Tenascin C more than allogenic cells.

In vitro mutual interaction between tenocytes and adipose-derived mesenchymal stromal cells.

BACKGROUND AIMS: Tendon is a complex tissue with a reduced regenerative ability. Nowadays, little or nothing is known about the regenerative effect of adipose-derived mesenchymal stromal cells (ADSCs) on tendons. METHODS: The study aimed to evaluate the in vitro mutual interaction of ADSCs and tenocytes in standard culture conditions and a microwound healing model. Tenocyte viability, microwound recovery and the expression of genes encoding for the main extracellular matrix components and ADSC viability, differentiation and growth factor gene expression were evaluated. RESULTS: The effects of ADSCs on tenocytes were observed more in the microwound healing model, in which the rate of microwound healing and the expression of decorin, tenascin and collagens were significantly increased. The influence of tenocytes on ADSCs was also found in standard culture conditions: ADSCs were directed toward a tenogenic lineage, and growth factor expression increased. CONCLUSIONS: This study clarifies some aspects of the mutual interaction of ADSCs and tenocytes and provides in vitro evidence for a possible future application of ADSCs as a therapeutic strategy for tendon repair.

Response of human chondrocytes and mesenchymal stromal cells to a decellularized human dermis.

BACKGROUND: Although progress has been made in the treatment of articular cartilage lesions, they are still a major challenge because current techniques do not provide satisfactory long-term outcomes. Tissue engineering and the use of functional biomaterials might be an alternative regenerative strategy and fulfill clinical needs. Decellularized extracellular matrices have generated interest as functional biologic scaffolds, but there are few studies on cartilage regeneration. The aim of this study was to evaluate in vitro the biological influence of a newly developed decellularized human dermal extracellular matrix on two human primary cultures. METHODS: Normal human articular chondrocytes (NHAC-kn) and human mesenchymal stromal cells (hMSC) from healthy donors were seeded in polystyrene wells as controls (CTR), and on decellularized human dermis batches (HDM_derm) for 7 and 14 days. Cellular proliferation and differentiation, and anabolic and catabolic synthetic activity were quantified at each experimental time. Histology and scanning electron microscopy were used to evaluate morphology and ultrastructure. RESULTS: Both cell cultures had a similar proliferation rate that increased significantly (p < 0.0005) at 14 days. In comparison with CTR, at 14 days NHAC-kn enhanced procollagen type II (CPII, p < 0.05) and aggrecan synthesis (p < 0.0005), whereas hMSC significantly enhanced aggrecan synthesis (p < 0.0005) and transforming growth factor-beta1 release (TGF-ß1, p < 0.0005) at both experimental times. Neither inflammatory stimulus nor catabolic activity induction was observed. By comparing data of the two primary cells, NHAC-kn synthesized significantly more CPII than did hMSC at both experimental times (p < 0.005), whereas hMSC synthesized more aggrecan at 7 days (p < 0.005) and TGF-ß1 at both experimental times than did NHAC-kn (p < 0.005). CONCLUSIONS: The results obtained showed that in in vitro conditions HDM_derm behaves as a suitable scaffold for the growth of both well-differentiated chondrocytes and undifferentiated mesenchymal cells, thus ensuring a biocompatible and bioactive substrate. Further studies are mandatory to test the use of HDM_derm with tissue engineering to assess its therapeutic and functional effectiveness in cartilage regeneration.

Evaluating the Mentors in Violence Prevention Program: A Process Examination of How Implementation Can Affect Gender-Based Violence Outcomes.

Gender-based violence is a global public health issue and major human rights concern. It is also a type of violence that is disproportionately experienced by women and girls. This study is the first to examine multiple implementation process (dosage, fidelity, and adaptation) effects on changes in anticipated outcomes of a school-based bystander program targeting gender-based violence, Mentors in Violence Prevention (MVP). Data were collected from two participant groups: mentees (students receiving MVP) and mentors (students delivering MVP), across nine participating high schools. The mentee sample comprised 698 students (about 48.9% males and 49.7% females), aged 11 to 14 years old (M = 11.86, SD = 0.64). The mentor sample comprised 118 students (17.80% males, 82.20% females), aged 15 to 18 years old (M = 16.42, SD = 0.60). Anticipated outcomes were changes in bystanders' attitudes, social influences, control perceptions, intentions, willingness, and intervention behavior, measured using mentees' self-reports at two time points approximately 1 year apart. Implementation processes were measured using mentors' self-reports. Analyses revealed no effects for any of the implementation variables across changes in any of the outcomes measured. These results highlight important implications for the implementation of the MVP program going forward, given its widespread implementation in the United Kingdom. Possible ways that MVP may be enhanced in future are discussed. For example, furthering understanding into how gender-based violence and bystander intervention are addressed and framed during MVP lessons would give more insight into how the current implementation of the program can be improved to maximize its potential benefits.

Anti-Oxidant Multi-Functionalized Materials: Strontium-Substituted Monetite and Brushite as Delivery Systems for Curcumin.

Curcumin has numerous biological activities and pharmaceutical applications related to its ability to inhibit reactive oxygen species. Herein, strontium-substituted monetite (SrDCPA) and strontium-substituted brushite (SrDCPD) were synthesized and further functionalized with curcumin with the aim to develop materials that combine the anti-oxidant properties of the polyphenol, the beneficial role of strontium toward bone tissue, and the bioactivity of calcium phosphates. Adsorption from hydroalcoholic solution increases with time and curcumin concentration, up to about 5-6 wt%, without affecting the crystal structure, morphology, and mechanical response of the substrates. The multi-functionalized substrates exhibit a relevant radical scavenging activity and a sustained release in phosphate buffer. Cell viability, morphology, and expression of the most representative genes were tested for osteoclast seeded in direct contact with the materials and for osteoblast/osteoclast co-cultures. The materials at relatively low curcumin content (2-3 wt%) maintain inhibitory effects on osteoclasts and support the colonization and viability of osteoblasts. The expressions of Alkaline Phosphatase (ALPL), collagen type I alpha 1 chain (COL1A1), and osteocalcin (BGLAP) suggest that curcumin reduces the osteoblast differentiation state but yields encouraging osteoprotegerin/receptor activator for the NFkB factor ligand (OPG/RANKL) ratio.

Bystander intervention among secondary school pupils: Testing an augmented Prototype Willingness Model.

This study augmented the Prototype Willingness Model (PWM) to assess reactive and deliberative decision-making underpinning bystander intervention in gender-based violence contexts. There were 2079 participants (50% male, 49% female, and 1% unreported), aged 11-15 years old (M = 12.32, SD = 0.91), attending 19 secondary schools across Scotland. Participants self-reported the augmented PWM variables, then their intervention behaviour approximately 1 month later. Path analyses mostly supported the predicted relationships between positive and negative bidimensional attitudes, subjective norms, prototype perceptions, perceived behavioural control, and self-efficacy on intentions and willingness. Willingness predicted positive (speaking with a teacher) and negative (doing nothing) intervention in less serious violence. Self-efficacy predicted negative intervention in more serious violence. Subjective norms positively moderated the attitudes-intentions relationship. Overall, the results suggested that reactive (willingness) more so than deliberative (intention) decision-making account for intervention when young people witness gender-based violence. Additionally, the findings highlight the complexity of bystander intervention decision-making, where adding control perceptions, bidimensional attitudes, and moderators have independent contributions. Furthermore, self-comparison to the typical bystander who positively intervenes (prototype perceptions) was the strongest predictor of intentions and willingness, highlighting in a novel way the importance of image and group membership on decision-making.

Monetite vs. Brushite: Different Influences on Bone Cell Response Modulated by Strontium Functionalization.

Monetite and brushite are regarded with increasing interest for the preparation of biomaterials for applications in the musculoskeletal system. Herein, we investigated the influence of strontium substitution in the structures of these two phosphates on bone cell response. To achieve this aim, co-cultures of human primary osteoclasts and human osteoblast-like MG63 cells were tested on strontium-substituted monetite and strontium-substituted brushite, as well as on monetite and brushite, as controls. In both structures, strontium substitution for calcium amounted to about 6 at% and provoked enlargement of the cell parameters and morphologic variations. Cumulative release in physiological solution increased linearly over time and was greater from brushite (up to about 160 and 560 mg/L at 14 days for Sr and Ca, respectively) than from monetite (up to about 90 and 250 mg/L at 14 days for Sr and Ca, respectively). The increasing viability of osteoblast-like cells over time, with the different expression level of some typical bone markers, indicates a more pronounced trigger toward osteoblast differentiation and osteoclast inhibition by brushite materials. In particular, the inhibition of cathepsin K and tartrate-resistant acid phosphatase at the gene and morphological levels suggests strontium-substituted brushite can be applied in diseases characterized by excessive bone resorption.

Ageing and Osteoarthritis Synergically Affect Human Synoviocyte Cells: An In Vitro Study on Sex Differences.

Osteoarthritis is a chronic inflammatory disease that affects all of the joints, especially those of the elderly. Aging is a natural and irreversible biological process implicated in the pathophysiology of many chronic diseases, such as osteoarthritis. Inflammation and oxidative stress are the main factors involved in osteoarthritis and aging, respectively, with the production of several pro-inflammatory cytokines such as Interleukin 1ß (IL1ß) and reactive oxygen species. The aim of the study was to set-up an in vitro model of osteoarthritis and aging, focusing on the sex differences by culturing male and female fibroblast-like synoviocytes (FLSs) with IL1ß, hydrogen peroxide (H2O2), IL1ß+H2O2 or a growth medium (control). IL1ß+H2O2 reduced the cell viability and microwound healing potential, increased Caspase-3 expression and reactive oxygen species and IL6 production; IL1ß increased IL6 production more than the other conditions did; H2O2 increased Caspase-3 expression and reactive oxygen species production; Klotho expression showed no differences among the treatments. The FLSs from female donors demonstrated a better response capacity in unfavorable conditions of inflammation and oxidative stress than those from the male donors did. This study developed culture conditions to mimic the aging and osteoarthritis microenvironment to evaluate the behavior of the FLSs which play a fundamental role in joint homeostasis, focusing on the sex-related aspects that are relevant in the osteoarthritis pathophysiology.

Matrix metalloproteinase 13 loss associated with impaired extracellular matrix remodeling disrupts chondrocyte differentiation by concerted effects on multiple regulatory factors.

OBJECTIVE: To link matrix metalloproteinase 13 (MMP-13) activity and extracellular matrix (ECM) remodeling to alterations in regulatory factors leading to a disruption in chondrocyte homeostasis. METHODS: MMP-13 expression was ablated in primary human chondrocytes by stable retrotransduction of short hairpin RNA. The effects of MMP-13 knockdown on key regulators of chondrocyte differentiation (SOX9, runt-related transcription factor 2 [RUNX-2], and beta-catenin) and angiogenesis (vascular endothelial growth factor [VEGF]) were scored at the protein level (by immunohistochemical or Western blot analysis) and RNA level (by real-time polymerase chain reaction) in high-density monolayer and micromass cultures under mineralizing conditions. Effects on cellular viability in conjunction with chondrocyte progression toward a hypertrophic-like state were assessed in micromass cultures. Alterations in SOX9 subcellular distribution were assessed using confocal microscopy in micromass cultures and also in osteoarthritic cartilage. RESULTS: Differentiation of control chondrocyte micromasses progressed up to a terminal phase, with calcium deposition in conjunction with reduced cell viability and scant ECM. MMP-13 knockdown impaired ECM remodeling and suppressed differentiation in conjunction with reduced levels of RUNX-2, beta-catenin, and VEGF. MMP-13 levels in vitro and ECM remodeling in vitro and in vivo were linked to changes in SOX9 subcellular localization. SOX9 was largely excluded from the nuclei of chondrocytes with MMP-13-remodeled or -degraded ECM, and exhibited an intranuclear staining pattern in chondrocytes with impaired MMP-13 activity in vitro or with more intact ECM in vivo. CONCLUSION: MMP-13 loss leads to a breakdown in primary human articular chondrocyte differentiation by altering the expression of multiple regulatory factors.