Optimum temperature for extracellular matrix production by articular chondrocytes

Mimicking Loading-Induced Cartilage Self-Heating in Vitro Promotes Matrix Formation in Chondrocyte-Laden Constructs with Different Mechanical Properties

Articular cartilage presents a mechanically sensitive tissue. Chondrocytes, the sole cell type residing in the tissue, perceive and react to physical cues as signals that significantly modulate their behavior. Hyaline cartilage is a connective tissue with high dissipative capabilities, able to increase its temperature during daily activities, thus providing a dynamic thermal milieu for the residing chondrocytes. This condition, self-heating, which is still chiefly ignored among the scientific community, adds a new thermal dimension in cartilage mechanobiology. Motivated by the lack of studies exploring this dynamic temperature increase as a potential stimulus in cartilage-engineered constructs, we aimed to elucidate whether loading-induced evolved temperature serves as an independent or complementary regulatory cue for chondrocyte function. In particular, we evaluated the chondrocytes' response to thermal and/or mechanical stimulation in two types of scaffolds exhibiting dissipation levels close to healthy and degenerated articular cartilage. It was found, in both scaffold groups, that the combination of dynamic thermal and mechanical stimuli induced superior effects in the expression of major chondrogenic genes, such as SOX9 and LOXL2, compared to either signal alone. Similar effects were also observed in proteoglycan accumulation over time, along with increased mRNA transcription and synthesis of TRPV4, and for the first time demonstrated in chondrocytes, TREK1 ion channels. Conversely, the chondrogenic response of cells to isolated thermal or mechanical cues was generally scaffold-type dependent. Nonetheless, the significance of thermal stimulus as a chondro-inductive signal was better supported in both studied groups. Our data indicates that the temperature evolution is necessary for chondrocytes to more effectively perceive and translate applied mechanical loading.

Temperature evolution following joint loading promotes chondrogenesis by synergistic cues via calcium signaling

During loading of viscoelastic tissues, part of the mechanical energy is transformed into heat that can locally increase the tissue temperature, a phenomenon known as self-heating. In the framework of mechanobiology, it has been accepted that cells react and adapt to mechanical stimuli. However, the cellular effect of temperature increase as a by-product of loading has been widely neglected. In this work, we focused on cartilage self-heating to present a 'thermo-mechanobiological' paradigm, and demonstrate how the coupling of a biomimetic temperature evolution and mechanical loading could influence cell behavior. We thereby developed a customized in vitro system allowing to recapitulate pertinent in vivo physical cues and determined the cells chondrogenic response to thermal and/or mechanical stimuli. Cellular mechanisms of action and potential signaling pathways of thermo-mechanotransduction process were also investigated. We found that co-existence of thermo-mechanical cues had a superior effect on chondrogenic gene expression compared to either signal alone. Specifically, the expression of Sox9 was significantly upregulated by application of the physiological thermo-mechanical stimulus. Multimodal transient receptor potential vanilloid 4 (TRPV4) channels were identified as key mediators of thermo-mechanotransduction process, which becomes ineffective without external calcium sources. We also observed that the isolated temperature evolution, as a by-product of loading, is a contributing factor to the cell response and this could be considered as important as the conventional mechanical loading. Providing an optimal thermo-mechanical environment by synergy of heat and loading portrays new opportunity for development of novel treatments for cartilage regeneration and can furthermore signal key elements for emerging cell-based therapies.

Cartilage and collagen mechanics under large-strain shear within in vivo and at supraphysiogical temperatures

Human joints, particularly those of extremities, experience a significant range of temperatures in vivo. Joint temperature influences the mechanics of both joint and cartilage, and the mechanics of cartilage can affect the temperature of both joint and cartilage. Thermal treatments and tissue repairs, such as thermal chondroplasty, and ex vivo tissue engineering may also expose cartilage to supraphysiological temperatures. Furthermore, although cartilage undergoes principally compressive loads in vivo, shear strain plays a significant role at larger compressive strains. Thus, we aimed to determine whether and how the bulk mechanical responses of cartilage undergoing large-strain shear change (1) within the range of temperatures relevant in vivo, and (2) both during and after supraphysiological thermal treatments. We completed large-strain shear tests (10 and 15%) at four thermal conditions: 24^∘C and 40^∘C to span the in vivo range, and 70^∘C and 24^∘C repeated after 70^∘C to explore mechanics during and after potential treatments. We calculated the bulk mechanical responses (strain-energy dissipation densities, peak-to-peak shear stresses, and peak-effective shear moduli) as of function of temperature and used statistical methods to probe significant differences. To probe the mechanisms underlying differences we assessed specimens, principally the type II collagen, with imaging (second harmonic generation and transmission electron microscopies, and histology) and assessed the temperature-dependent mechanics of type II collagen molecules within cartilage using steered molecular dynamics simulations. Our results suggest that the bulk mechanical responses of cartilage depend significantly on temperature both within the in vivo range and at supraphysiological temperatures, showing significant reductions in all mechanical measures with increasing temperature. Using imaging and simulations we determined that one underlying mechanism explaining our results may be changes in the molecular deformation profiles of collagen molecules versus temperature, likely compounded at larger length scales. These new insights into the mechanics of cartilage and collagen may suggest new treatment targets for damaged or osteoarthritic cartilage.

Embryonic canalization and its limits-A view from temperature

Many animals are able to produce similar offspring over a range of environmental conditions. This property of the developmental process has been termed canalization-the channeling of developmental pathways to generate a stable outcome despite varying conditions. Temperature is one environmental parameter that has fundamental effects on cell physiology and biochemistry, yet developmental programs generally result in a stable phenotype under a range of temperatures. On the other hand, there are typically upper and lower temperature limits beyond which the developmental program is unable to produce normal offspring. This review summarizes data on how development is affected by temperature, particularly high temperature, in various animal species. It also brings together information on potential cell biological and developmental genetic factors that may be responsible for developmental stability in varying temperatures, and likely critical mechanisms that break down at high temperature. Also reviewed are possible means for studying temperature effects on embryogenesis and how to determine which factors are most critical at the high-temperature limits for normal development. Increased knowledge of these critical factors will point to the targets of selection under climate change, and more generally, how developmental robustness in varying environments is maintained.

Lipopolysaccharides-mediated injury to chondrogenic ATDC5 cells can be relieved by Sinomenine via downregulating microRNA-192

Sinomenine (SIN) is an isoquinoline derived from Caulis Sinomenii that has been used to treat rheumatoid arthritis and osteoarthritis for several decades in China. This study aims to reveal the effects of SIN on mouse chondrogenic ATDC5 cells growth and inflammation. SIN was used to treat ATDC5 cells injured by lipopolysaccharides (LPS). The following parameters were determined for evaluating the treatment effects of SIN: cell viability, apoptosis, reactive oxygen species generation, and pro-inflammatory cytokines release. Besides, the expression of LPS-sensitive miRNA (miR-192) and the activation of NF-κB and MAPK signaling were studied to explain SIN's function. SIN with concentration of 30 μM significantly attenuated LPS-induced cell damage via increasing cell viability, inhibiting apoptosis and reactive oxygen species generation, and declining IL-6 and TNF-α release. miR-192 was downregulated by SIN treatment. Restoration of miR-192 expression by miRNA transfection could significantly impede SIN's protective action. Besides, the inhibitory effects of SIN on the activation of NF-κB and MAPK signaling were attenuated by miR-192 overexpression. Furthermore, GDF11 was found to be a target gene of miR-192. LPS-mediated injury to chondrogenic ATDC5 cells can be relieved by SIN via downregulating miR-192 and subsequently repressing the activation of NF-κB and MAPK signaling.

Periodic mild heat stimuli diminish extracellular matrix synthesis in pellet cultured human chondrocytes

Objective

This study aimed to clarify the effects of periodic mild heat stimuli on extracellular matrix (ECM) synthesis of adult human chondrocytes in 3-dimensional pellet culture.

Results

Human articular chondrocytes were subjected to pellet culture at 37 °C for 3 days. Thereafter, the pellets were divided into three groups: 32 °C group which was cultured at 32 °C without heat stimuli, 32 °C + Heat group which was cultured at 32 °C and applied periodic heat stimuli, 37 °C group which was cultured at 37 °C. Heat stimuli were given by transferring the pellets into a CO₂ incubator set at 41 °C for 20 min/day, 6 times/week. ECM synthesis ability was evaluated by analyzing the mRNA expressions. Additionally, the collagen and proteoglycan content in the pellet was quantified. DNA content was also measured for estimating the cell amount. We found that there were no significant differences in the mRNA expression of COL2A1, COL1A1, and ACAN between the 32 °C group and 32 °C + Heat group. However, the collagen content per cell and DNA content were significantly lower in the 32 °C + Heat group compared to other groups. Our results indicate that periodic mild heat stimuli may diminish ECM synthesis due to inhibition of collagen production and loss of cells.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4058-x) contains supplementary material, which is available to authorized users.

The effect of serum types on Chondrogenic differentiation of adipose-derived stem cells

Background

Fetal bovine serum (FBS) is the most essential supplement in culture media for cellular proliferation, metabolism, and differentiation. However, due to a limited supply and subsequently rising prices, a series of studies have investigated a biological feasibility of replaceable serums to substitute FBS. Along with the increasing interests to manufacture stem cell-based cellular products, optimizing the composition of culture media including serums and exogenous growth factors (GFs) is of importance. In this experiment, the effect of bovine serum (BS) and newborn calf serum (NCS) on proliferation and chondrogenic differentiation capacity of human adipose derived stem cells (ADSCs) was evaluated, especially in the chondrogenically supplemented culture condition.

Methods

ADSCs were chondrogenically cultured with FBS, BS, and NCS for 14 days. For the acceleration of in vitro chondrogenesis, exogenous insulin-like growth factor and transforming growth factor-β3 were added. Viability and proliferation of ADSCs were evaluated using Live/Dead fluorescence staining and DNA amount, respectively. To investigate a chondrogenic differentiation, a series of assays were performed including a quantification of glycosaminoglycan deposition, alcian blue staining, and RT-PCR analysis for type II collagen, aggrecan and Sox-9 genes.

Results

The results demonstrated that proliferation of ADSCs was facilitated in FBS condition as compared with other serum types. For chondrogenic marker gene expression, serum substitutes enhanced Sox-9 expression level on day 14. The deposition of glycosaminoglycan was more facilitated in BS condition regardless of additional chondrogenic GFs.

Conclusion

It could be presumably speculated that serum types and exogenous supplements of GFs could also be important parameters to optimize culture media composition, especially in order to maintain the enhanced levels of both proliferation and chondrogenic differentiation of ADSCs during expansion.

The fascial system and exercise intolerance in patients with chronic heart failure: hypothesis of osteopathic treatment

Chronic heart failure is a progressive, debilitating disease, resulting in a decline in the quality of life of the patient and incurring very high social economic costs. Chronic heart failure is defined as the inability of the heart to meet the demands of oxygen from the peripheral area. It is a multi-aspect complex disease which impacts negatively on all of the body systems. Presently, there are no texts in the modern literature that associate the symptoms of exercise intolerance of the patient with a dysfunction of the fascial system. In the first part of this article, we will discuss the significance of the disease, its causes, and epidemiology. The second part will explain the pathological adaptations of the myofascial system. The last section will outline a possible osteopathic treatment for patients with heart failure in order to encourage research and improve the general curative approach for the patient.

Polymodal Transient Receptor Potential Vanilloid (TRPV) Ion Channels in Chondrogenic Cells

Mature and developing chondrocytes exist in a microenvironment where mechanical load, changes of temperature, osmolarity and acidic pH may influence cellular metabolism. Polymodal Transient Receptor Potential Vanilloid (TRPV) receptors are environmental sensors mediating responses through activation of linked intracellular signalling pathways. In chondrogenic high density cultures established from limb buds of chicken and mouse embryos, we identified TRPV1, TRPV2, TRPV3, TRPV4 and TRPV6 mRNA expression with RT-PCR. In both cultures, a switch in the expression pattern of TRPVs was observed during cartilage formation. The inhibition of TRPVs with the non-selective calcium channel blocker ruthenium red diminished chondrogenesis and caused significant inhibition of proliferation. Incubating cell cultures at 41 °C elevated the expression of TRPV1, and increased cartilage matrix production. When chondrogenic cells were exposed to mechanical load at the time of their differentiation into matrix producing chondrocytes, we detected increased mRNA levels of TRPV3. Our results demonstrate that developing chondrocytes express a full palette of TRPV channels and the switch in the expression pattern suggests differentiation stage-dependent roles of TRPVs during cartilage formation. As TRPV1 and TRPV3 expression was altered by thermal and mechanical stimuli, respectively, these are candidate channels that contribute to the transduction of environmental stimuli in chondrogenic cells.

Culture temperature affects human chondrocyte messenger RNA expression in monolayer and pellet culture systems

Cell-based therapy has been explored for articular cartilage regeneration. Autologous chondrocyte implantation is a promising cell-based technique for repairing articular cartilage defects. However, there are several issues such as chondrocyte de-differentiation. While numerous studies have been designed to overcome some of these issues, only a few have focused on the thermal environment that can affect chondrocyte metabolism and phenotype. In this study, the effects of different culture temperatures on human chondrocyte metabolism- and phenotype-related gene expression were investigated in 2D and 3D environments. Human chondrocytes were cultured in a monolayer or in a pellet culture system at three different culture temperatures (32°C, 37°C, and 41°C) for 3 days. The results showed that the total RNA level, normalized to the threshold cycle value of internal reference genes, was higher at lower temperatures in both culture systems. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and citrate synthase (CS), which are involved in glycolysis and the citric acid cycle, respectively, were expressed at similar levels at 32°C and 37°C in pellet cultures, but the levels were significantly lower at 41°C. Expression of the chondrogenic markers, collagen type IIA1 (COL2A1) and aggrecan (ACAN), was higher at 37°C than at 32°C and 41°C in both culture systems. However, this phenomenon did not coincide with SRY (sex-determining region Y)-box 9 (SOX9), which is a fundamental transcription factor for chondrogenesis, indicating that a SOX9-independent pathway might be involved in this phenomenon. In conclusion, the expression of chondrocyte metabolism-related genes at 32°C was maintained or enhanced compared to that at 37°C. However, chondrogenesis-related genes were further induced at 37°C in both culture systems. Therefore, manipulating the culture temperature may be an advantageous approach for regulating human chondrocyte metabolic activity and chondrogenesis.

Culture temperature affects redifferentiation and cartilaginous extracellular matrix formation in dedifferentiated human chondrocytes

To date, there have been few studies on how temperature affects the phenotype and metabolism of human chondrocytes. Thus, the purpose of this study was to elucidate the effects of culture temperature on chondrocyte redifferentiation and extracellular matrix (ECM) formation using dedifferentiated mature human chondrocytes in vitro. Dedifferentiated chondrocytes were cultured in a pellet culture system for up to 21 days. The pellets were randomly divided into three groups with different culture temperature (32, 37, and 41°C). Chondrocyte redifferentiation and ECM formation were evaluated by wet weight, messenger ribonucleic acid (mRNA), histological, and biochemical analyses. The results showed that the wet weight and the mRNA expressions of collagen type II A1 and cartilage oligomeric matrix protein at 37°C were higher than the corresponding values at 32°C. The histological and biochemical analyses revealed that the syntheses of type II collagen and proteoglycan were promoted at 37°C compared to those at 32°C, whereas they were considerably inhibited at 41°C. In conclusion, the results obtained herein indicated that temperature affects chondrocyte redifferentiation and ECM formation, and modulation of temperature might thus represent an advantageous means to regulate the phenotype and biosynthetic activity of chondrocytes.