Number Of Viable Chondrocytes Research Articles

Carbon Nanotubes Interference with Luminescence-Based Assays

Carbon nanotubes (CNTs) are one of the most promising nanomaterials synthesized to date. Thanks to their unique mechanical, electronic, and optical properties, they have found a wide application in electronics in the production of biosensors and nanocomposites. The functionalization of multiwalled carbon nanotubes (MWCNTs) is aimed at making them biocompatible by adding hydrophilic groups on their surface, increasing their solubility and thus rendering them applicable in the regenerative medicine. So far, there is conflicting information about carbon nanotubes in biological systems. This paper investigates the effect of functionalized, oxidized, multiwalled carbon nanotubes (MWCNT-Ox) on the cytotoxicity of normal human articular chondrocytes (NHAC-kn cell line). Since absorbance-based and fluorescence-based assays were shown to interfere with carbon nanotubes, luminescence-based tests were carried out, as they work on a different method of detection and provide advantages over the mentioned ones. Cell viability and reactive oxygen species (ROS) tests were carried out. The cell viability assay showed that with the increasing MWCNTs concentration, the number of viable chondrocytes was significantly decreasing. Exposure to MWCNT-Ox indicated oxidative stress in the lowest investigated concentration with a decreased amount of ROS with higher concentrations. However, control experiments with adenosine triphosphate (ATP) and H2O2—molecules that are detected by the assays—showed that carbon nanotubes interfere directly with measurement, thus rendering the results unreliable. To understand the exact interference mechanisms, further studies must be taken. In conclusion, this study shows that luminescence-based tests yield erroneous results, confirming that in vitro experiments in the literature concerning carbon nanotubes should be analyzed with caution.

Protective effects of platelet-rich plasma against lidocaine cytotoxicity on canine articular chondrocytes

BackgroundLidocaine (LD) is one of the most commonly used local anesthetics for performing arthroscopic surgery and managing of osteoarthritic pain in both human and veterinary medicine. However, over the last years, several studies have focused on the chondrotoxic effects of LD. In order to ensure that intra-articular lidocaine is safe to use, treatments aimed at mitigating chondrocyte death have recently been investigated. The aim of this study is to evaluate the possible protective effects of platelet-rich plasma (PRP) against LD cytotoxicity on canine articular chondrocytes.ResultsArticular canine chondrocytes, were exposed to 1% or 1.8% LD alone or in co-presence with 10% PRP for 30 min. In order to evaluate the effects of PRP pre-treatments, experiments were carried out on cells cultured in serum-free medium-or in medium supplemented with 10% PRP or 10% fetal bovine serum. Cell viability was evaluated by methyl thiazolyl tetrazolium assay and cell apoptosis was analyzed by flow cytometry using annexin V-fluorescein isothiocyanate/propidium iodide. The results showed that LD significantly reduced canine chondrocytes viability, probably due to apoptosis induction. Pre-treatment or the co-presence of PRP in the media restored the number of viable chondrocytes. The PRP also seemed to protect the cells from LD-induced apoptosis.ConclusionsPre-treatments and/or the simultaneous administration of PRP reduced LD-induced cytotoxicity in canine chondrocytes. Further in vivo studies are required to determine whether PRP can be used as a save protective treatment for dogs receiving intra-articular LD injections.

Chondroprotection by urocortin involves blockade of a mechanosensitive piezo1 ion channel: novel, exploitable pathways for the treatment and prevention of osteoarthritis?

Purpose: Currently, the only treatments for Osteoarthritis (OA) are steroidal and non-steroidal anti-inflammatory drugs, and in severe cases total joint replacement surgery. However, these strategies only ameliorate symptoms but do not address the fundamental cause of the disease. Clearly therefore, there is a need for better therapies which address the underlying cause of OA. Importantly, this includes a reduction in the number of viable chondrocytes in articular cartilage, as the severity of cartilage damage has been shown to correlate negatively with the number of remaining chondrocytes. To develop a treatment strategy at a more fundamental level therefore, it is crucial to understand the nature of this chondrocyte cell death. We have previously found that the small endogenous peptide Urocortin (Ucn) and its two cognate G protein coupled receptors (CRF-R1 and CRF-R2) are expressed by human chondrocytes and crucially, its removal from the surrounding milieu using a Ucn depleting antibody or a pan receptor antagonist (as Ucn can bind to both receptor subtypes) causes profound chondrocyte cell death. Therefore, we believe that Ucn is an essential autocrine/paracrine pro-survival factor for human chondrocytes. Here we examine the pathways involved in this chondroprotective effect of Ucn. Methods: Selective pharmacological antagonists to CRF-R1 (CP-154526, 1–50μM; Tocris) and CRF-R2 (astressin2B 1–50μM; Tocris) were used to determine the receptor subtype responsible for the pro-survival effect of Ucn in human primary articular chondrocytes. Cell death was detected using the Annexin V-FITC Apoptosis Detection Kit I (BD Bioscience) and Western immunoblotting was used to determine the status of pro-apoptotic markers. Downstream signalling pathways involved in antagonist induced cell death were investigated using the adenylate cyclase activator forskolin (0.1μM; Tocris), the phospholipase C (PLC) activator m3M3FBS (0.1μM; Tocris), and the phospholipase A2 (PLA2) inhibitor OBAA (0.1μM; Tocris). Changes in intracellular Ca2+ were detected using Fluo-4 AM permeant dye (Thermo Fisher Scientific) and this effect was studied using the non-selective cation channel blocker Gadolinium (Gd3+ 100μM; Tocris). Human chondrocytes were transfected with siRNAs derived from a selected panel (Dharmacon), to knock down and identify specific ion channel species involved in chondrocyte survival/death. Results: We found that only inhibition of CRF-R1 using CP 154526 caused antagonist induced cell death, suggesting that the chondrocyte pro-survival effect is caused by Ucn binding to CRF-R1 alone (p < 0.05). This cell death was associated with an increased expression of p53 and cleavage of both caspases 9 and 3 but not caspase 8, implicating the intrinsic apoptotic pathway in this process. Furthermore, we were able to rescue chondrocyte cell death in the presence of antagonist, with the adenylate cyclase activator forskolin and the phospholipase A2 inhibitor OBAA but not with the phospholipase C activator m3M3FBS, suggesting a role for cAMP and PKA activation and a decrease in PLA2 activity in this process. Antagonist induced cell death initially involved a large inward flux of Ca2+ resulting in Ca2+ overload. This inward movement of Ca2+ and subsequent cell death could be prevented by Gd3+ p < 0.05, implying that this process involves a non-selective cation channel and that when Ucn is present, this channel is in a closed conformation. Using an siRNA array panel, we identified Piezo1 as the target ion channel responsible for chondrocyte cell death in the absence of Ucn. Conclusions: These findings are of great interest because Piezo1 is a novel type of mechanosensor and has recently been found to be highly expressed in chondrocytes and responsible for chondrocyte cell death in a porcine acute mechanical injury model of OA. This is the first study to bring together all of these critical mediators of chondrocyte survival/death and elucidating fully the relationship between Ucn receptor activation and gating of Piezo1, may highlight novel targets as potential therapy nodes for the treatment/prevention of OA. Additionally, because of the crucial role of Ucn in chondrocyte survival, a study of the molecular status of this peptide and/or its receptor could represent novel biomarkers of OA severity and progression.

Effects of Different Cartilage Sculpting Techniques on Cellular Integrity of Nasal Septal Cartilage

Study background: Several techniques exist to sculpt nasal septal cartilage grafts for use in functional and cosmetic rhinoplasty, including the use of cold steel, Bovie electrosection and the Sonopet ultrasonic bone aspirator. This is the first investigation on the effects of these disparate tools on gross cellular integrity of sculpted cartilage. Methods: After IRB approval, extraneous nasal septal cartilage harvested during routine septoplasty and/or rhinoplasty procedures was collected from three patients treated within our institution for use in this study. Cartilage specimens from each patient were divided into four equal segments and a partial thickness trough was sculpted in the center of each piece with one of the three techniques described above. One segment remained free of any additional manipulation and served as a comparative control. Gross cellular architecture and number of viable chondrocytes were assessed with optical microscopy. Results: Minimal disruption of the cellular integrity of nasal septal cartilage samples sculpted with each of the three techniques was noted compared to control. Average cell counts revealed 96%, 97%, 97% and 97% viable nuclei in the scalpel, electrocautery, ultrasonic bone aspirator and control groups, respectively. Conclusion: Cartilage sculpting using cold steel, Bovie electrosection and the ultrasonic bone aspirator appear to have minimal effects on cellular integrity of cartilage grafts. This portends a favorable outlook on long term durability of these cartilage grafts and suggests that these three techniques can be used interchangeably for cartilage sculpting needs.

Experimental Pharmacology of Glucosamine Sulfate

Several clinical studies demonstrated that glucosamine sulfate (GS) is effective in controlling osteoarthritis (OA), showing a structure-modifying action. However, little is known about the molecular mechanism(s) by which GS exerts such action and about the effects of GS at a tissue level on osteoarthritic cartilage and other joint structures. Here we provide mechanistic evidence suggesting that in vitro GS attenuates NF-κB activation at concentrations in the range of those observed after GS administration to volunteers and patients, thus strengthening previous findings. Furthermore, we describe the effects of GS at a tissue level on the progression of the disease in a relevant model of spontaneous OA, the STR/ort mouse. In this model, the administration of GS at human corresponding doses was associated with a significant decrease of OA scores. Histomorphometry showed that the lesion surface was also significantly decreased, while the number of viable chondrocytes within the matrix was significantly increased. GS improved the course of OA in the STR/Ort mouse, by delaying cartilage breakdown as assessed histologically and histomorphometrically.

Effects of exercise on chondrocyte viability and subchondral bone sclerosis in the distal third metacarpal and metatarsal bones of young horses

The objective was to determine the effects of early exercise on the articular cartilage and subchondral bone at specific sites of the distal third metacarpal and metatarsal bones of 12 young Thoroughbred horses allowed free choice exercise at pasture. Six of the horses had additional controlled exercise 5 days per week from mean age of 21 ± 20 days of age (range: 3–83 days) until 17.1 months of age. Confocal laser scanning microscopy was used to quantify viable and non-viable chondrocytes. Proteoglycan scoring and modified Mankin scoring was performed and subchondral bone mineral density measured by computed tomography. The number of viable chondrocytes was significantly greater in the conditioned group, which also had a higher Safranin O/Fast Green (SOFG) score than did the group which could exercise only at pasture. There was no difference in mean bone mineral density between groups, nor was there relationship between subchondral bone mineral density and chondrocyte viability. The apparent beneficial effects of early conditioning exercise may support the use of exercise to optimise development of articular cartilage in young individuals.

Sustained transgene expression in cartilage defects in vivo after transplantation of articular chondrocytes modified by lipid-mediated gene transfer in a gel suspension delivery system.

Genetically modified chondrocytes may be able to modulate articular cartilage repair. To date, transplantation of modified chondrocytes into cartilage defects has been restricted to viral vectors. We tested the hypothesis that a recombinant gene can be delivered to sites of cartilage damage in vivo using chondrocytes transfected by a lipid-mediated gene transfer method. Isolated lapine articular chondrocytes were transfected with an expression plasmid vector carrying the P. pyralis luciferase gene using the reagent FuGENE 6. Transfected chondrocytes were encapsulated in alginate spheres and implanted into osteochondral defects in the knee joints of rabbits. In vitro, luciferase activity in pCMVLuc-transfected spheres showed an early peak at day 2 post-transfection and remained elevated at day 32, the longest time point evaluated. The number of viable chondrocytes in non-transfected and transfected spheres increased over the period of cultivation. In vivo, luciferase activity was maximal at day 5 post-transfection, declined by day 16, but was still present at day 32. On histological analysis, the alginate-chondrocyte spheres filled the cartilage defects and were surrounded by a fibrous repair tissue composed of spindle-shaped cells. These data demonstrate the successful introduction of articular chondrocytes modified by lipid-mediated gene transfer in a gel suspension delivery system into osteochondral defects and the sustained expression of the transgene in vivo. This method may be used to define the effects of genes involved in cartilage repair and may provide alternative treatments for articular cartilage defects.

Banking of osteochondral allografts. Part I. Viability assays adapted for osteochondrol and cartilage studies.

The aim of this study was to adapt a reliable, reproducible and simple viability assay for cartilage and osteochondral studies. The previous assays (radioisotope uptake, assessment of matrix components, histological methods, oxygen consumption etc.) were complex, laborious, time consuming or suffer from difficulty of interpretation. MTT assay was chosen because it has been widely and successfully used in different cell and tissue studies, but has not been published on human solid articular cartilage. Fresh intact cartilage samples of human tali were tested to investigate the assay. The reliability of the MTT assay was also tested by an fluorescent dye combination. The MTT assay is based on the production of purple formazan pigment from methyltetrazolium salt by the mitochondrial enzymes of viable chondrocytes. The enzyme kinetics of the reaction was also investigated because it was unknown in the case of cartilage. The amount of pigment formed can be measured by spectrophotometry after extraction by methyl cellosolve. The color density is proportional to mitochondrial enzyme activity, reflecting the number of viable chondrocytes. The optimal reagent concentration, biopsy size, and incubation period were established. There is a linear relationship between the cartilage weight and the pigment production activity. A 9.8% nonspecific raction was observed in the negative controls. The enzyme kinetics of the reaction was also investigated. The MTT clevage up to 0.1% (w/v) follows the Michaelis kinetics. We calculated the Michaelis constant (2835 +/- 130 microM), the maximal velocity (36 +/- 3.2 x 10(-5)microMsec(-1)) and the velocity constant (1.27 +/- 0.2 x 10(-7)sec(-1)) of the reaction. The latter is a significant marker for each tissue type. The viability of cartilage was also assessed and calculated by a fluorescent dye combination comprising 1 microg/ml propidium iodide (PI) and 4 microM/ml SYTO-16 stains. The PI stains dead cells (red fluorescence), the SYTO-16 stains live cells (green fluorescence). The staining can be visualised simultaneously, and the live/dead ratio can be calculated by image analysis software from saved image files. The MTT assay is a simple, non-expensive, efficient, reliable, reproducible, sensitive viability test for cartilage studies. The MTT reduction assay and the staining method were corrobative.

Physical and biological regulation of proteoglycan turnover around chondrocytes in cartilage explants. Implications for tissue degradation and repair.

The development of clinical strategies for cartilage repair and inhibition of matrix degradation may be facilitated by a better understanding of (1) the chondrocyte phenotype in the context of a damaged extracellular matrix, and (2) the roles of biochemical and biomechanical pathways by which matrix metabolism is mediated. Using methods of quantitative autoradiography, we examined the cell-length scale patterns of proteoglycan deposition and turnover in the cell-associated matrices of chondrocytes in adult bovine and calf cartilage explants. Results highlight a rapid turnover in the pericellular matrix, which may indicate spatial organization of PG metabolic pools, and specific biomechanical roles for different matrix regions. Subsequent to injurious compression of calf explants, which resulted in grossly visible tissue cracks and caused a decrease in the number of viable chondrocytes within explants, cell-mediated matrix catabolic processes appeared to increase, resulting in apparently increased rates of proteoglycan turnover around active cells. Furthermore, the influences of cell-stimulatory factors such as IL-1 beta appeared to be delayed in their effects subsequent to injurious compression, suggesting interactions between biomechanical and biochemical pathways of PG degradation. These results may provide a useful reference point in the development of in vitro models for cartilage injury and disease, and hint at possible new approaches in the development of cartilage repair strategies.

Microvascular transplantation of cryopreserved knee joints.

Successful transplantation of cryopreserved complex tissues has not yet been reported. We wanted to test whether microvascular transplantation of cryopreserved knee joints can be achieved in rats. Twenty-five knee joints were cryopreserved and then microsurgically transplanted to the groin of inbred recipient animals. Ten fresh knee joints were transplanted as controls. One week after transplantation, the transplants were evaluated in situ for pedicle patency and tissue perfusion and then harvested for histology. In all surviving rats (n = 21), the cryopreserved knee joints were well perfused immediately after transplantation. At harvest, 14 knee joints appeared viable with a patent pedicle, whereas 6 were questionably viable and demonstrated arterial thrombosis. Histologically, the viable joints revealed an intact bone and cartilage matrix; however, the number of viable chondrocytes and osteocytes was reduced. Additionally, endothelial cell plugs in some areas of the capillary bed led to scattered microinfarctions despite a patent vascular pedicle. The nonperfused transplants showed infarction. In conclusion, we have demonstrated successful microvascular transplantation of cryopreserved knee joints with reduced short-term viability. Long-term studies must determine whether full recovery occurs.