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Karchner JP, Yousefi F, Bitman SR, Darvish K, Pleshko N. Non-Destructive Spectroscopic Assessment of High and Low Weight Bearing Articular Cartilage Correlates with Mechanical Properties. Cartilage 2019; 10:480-490. [PMID: 29690771 PMCID: PMC6755878 DOI: 10.1177/1947603518764269] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVE Autologous articular cartilage (AC) harvested for repair procedures of high weight bearing (HWB) regions of the femoral condyles is typically obtained from low weight bearing (LWB) regions, in part due to the lack of non-destructive techniques for cartilage composition assessment. Here, we demonstrate that infrared fiber optic spectroscopy can be used to non-destructively evaluate variations in compositional and mechanical properties of AC across LWB and HWB regions. DESIGN AC plugs (N = 72) were harvested from the patellofemoral groove of juvenile bovine stifle joints, a LWB region, and femoral condyles, a HWB region. Near-infrared (NIR) and mid-infrared (MIR) fiber optic spectra were collected from plugs, and indentation tests were performed to determine the short-term and equilibrium moduli, followed by gravimetric water and biochemical analysis. RESULTS LWB tissues had a significantly greater amount of water determined by NIR and gravimetric assay. The moduli generally increased in tissues from the patellofemoral groove to the condyles, with HWB condyle cartilage having significantly higher moduli. A greater amount of proteoglycan content was also found in HWB tissues, but no differences in collagen content. In addition, NIR-determined water correlated with short-term modulus and proteoglycan content (R = -0.40 and -0.31, respectively), and a multivariate model with NIR data was able to predict short-term modulus within 15% error. CONCLUSIONS The properties of tissues from LWB regions differ from HWB tissues and can be determined non-destructively by infrared fiber optic spectroscopy. Clinicians may be able to use this modality to assess AC prior to harvesting osteochondral grafts for focal defect repair.
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Affiliation(s)
- James P. Karchner
- Department of Bioengineering, Temple University, Philadelphia, PA, USA
| | - Farzad Yousefi
- Department of Bioengineering, Temple University, Philadelphia, PA, USA
| | | | - Kurosh Darvish
- Department of Mechanical Engineering, Temple University, Philadelphia, PA, USA
| | - Nancy Pleshko
- Department of Bioengineering, Temple University, Philadelphia, PA, USA
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Anderson DE, Johnstone B. Dynamic Mechanical Compression of Chondrocytes for Tissue Engineering: A Critical Review. Front Bioeng Biotechnol 2017; 5:76. [PMID: 29322043 PMCID: PMC5732133 DOI: 10.3389/fbioe.2017.00076] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 11/23/2017] [Indexed: 01/19/2023] Open
Abstract
Articular cartilage functions to transmit and translate loads. In a classical structure-function relationship, the tissue resides in a dynamic mechanical environment that drives the formation of a highly organized tissue architecture suited to its biomechanical role. The dynamic mechanical environment includes multiaxial compressive and shear strains as well as hydrostatic and osmotic pressures. As the mechanical environment is known to modulate cell fate and influence tissue development toward a defined architecture in situ, dynamic mechanical loading has been hypothesized to induce the structure-function relationship during attempts at in vitro regeneration of articular cartilage. Researchers have designed increasingly sophisticated bioreactors with dynamic mechanical regimes, but the response of chondrocytes to dynamic compression and shear loading remains poorly characterized due to wide variation in study design, system variables, and outcome measurements. We assessed the literature pertaining to the use of dynamic compressive bioreactors for in vitro generation of cartilaginous tissue from primary and expanded chondrocytes. We used specific search terms to identify relevant publications from the PubMed database and manually sorted the data. It was very challenging to find consensus between studies because of species, age, cell source, and culture differences, coupled with the many loading regimes and the types of analyses used. Early studies that evaluated the response of primary bovine chondrocytes within hydrogels, and that employed dynamic single-axis compression with physiologic loading parameters, reported consistently favorable responses at the tissue level, with upregulation of biochemical synthesis and biomechanical properties. However, they rarely assessed the cellular response with gene expression or mechanotransduction pathway analyses. Later studies that employed increasingly sophisticated biomaterial-based systems, cells derived from different species, and complex loading regimes, did not necessarily corroborate prior positive results. These studies report positive results with respect to very specific conditions for cellular responses to dynamic load but fail to consistently achieve significant positive changes in relevant tissue engineering parameters, particularly collagen content and stiffness. There is a need for standardized methods and analyses of dynamic mechanical loading systems to guide the field of tissue engineering toward building cartilaginous implants that meet the goal of regenerating articular cartilage.
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Affiliation(s)
- Devon E Anderson
- Department of Orthopaedics and Rehabilitation, Oregon Health & Science University, Portland, OR, United States
| | - Brian Johnstone
- Department of Orthopaedics and Rehabilitation, Oregon Health & Science University, Portland, OR, United States
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Li S, Cao J, Caterson B, Hughes CE. Proteoglycan metabolism, cell death and Kashin-Beck disease. Glycoconj J 2012; 29:241-8. [PMID: 22733148 PMCID: PMC3423566 DOI: 10.1007/s10719-012-9421-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Revised: 06/06/2012] [Accepted: 06/12/2012] [Indexed: 12/13/2022]
Abstract
Kashin-Beck Disease (KBD) is an endemic, chronic and degenerative osteoarthropathy principally occurring in children. The characteristic pathological change of KBD is chondrocyte necrosis in hyaline articular cartilage. Proteoglycans are one of the major components in the extracellular matrix of articular cartilage, and disrupted proteoglycan metabolism and loss of proteoglycans in articular cartilage from KBD patients has been observed. In this mini-review, we discuss the close relationship between chondrocyte death including necrosis and loss of proteoglycan, and its potential mechanism during KBD onset and development, which may provide new clues for KBD research.
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Affiliation(s)
- Siyuan Li
- Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University), Ministry of Education, Xi'an, China
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Chiang H, Liao CJ, Wang YH, Huang HY, Chen CN, Hsieh CH, Huang YY, Jiang CC. Comparison of articular cartilage repair by autologous chondrocytes with and without in vitro cultivation. Tissue Eng Part C Methods 2010; 16:291-300. [PMID: 20187869 DOI: 10.1089/ten.tec.2009.0298] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVE autologous chondrocyte implantation usually requires in vitro cell expansion before implantation. We compared the efficacy of cartilage regeneration by in vitro-expanded chondrocytes at high density and freshly harvested chondrocytes at low density. DESIGN surgically created osteochondral defects at weight-bearing surface of femoral condyles of domestic pigs were repaired by biphasic cylindrical porous plugs of DL-poly-lactide-co-glycolide and beta-tricalcium phosphate. Plugs were seeded with autologous chondrocytes in its chondral phase, and press-fit to defects. Seeded cells were (1) in vitro-expanded chondrocytes harvested from stifle joint 3 weeks before implantation and (2) freshly harvested chondrocytes from recipient knee. Seeding densities were 70 x 10(6) and 7 x 10(6) cells/mL, respectively. Cell-free plugs served as control and defects remained untreated as null control. Outcome was examined at 6 months with International Cartilage Repair Society Scale. RESULTS the two experimental groups were repaired by hyaline cartilage with collagen type II and Safranin-O. Tissue in control group was primarily fibrocartilage. No regeneration was found in null control. Experimental groups had higher mean International Cartilage Repair Society scores than control in surface, matrix, and cell distribution, but were comparable with control in cell viability, subchondral bone, and mineralization. No significant difference existed between two experimental groups in any of the six categories. Uni-axial indentation test revealed similar creeping stress-relaxation property as native cartilage on experimental, but not control, specimen. CONCLUSIONS cartilage could regenerate in both experimental models, in comparable quality. Culture of chondrocytes before implantation is not necessary.
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Affiliation(s)
- Hongsen Chiang
- National Taiwan University Hospital, and College of Medicine, Taipei, Taiwan
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Coates EE, Fisher JP. Phenotypic variations in chondrocyte subpopulations and their response to in vitro culture and external stimuli. Ann Biomed Eng 2010; 38:3371-88. [PMID: 20556515 DOI: 10.1007/s10439-010-0096-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Accepted: 06/04/2010] [Indexed: 12/24/2022]
Abstract
Articular cartilage defects have limited capacity to self-repair, and cost society up to 60 billion dollars annually in both medical treatments and loss of working days. Recent developments in cartilage tissue engineering have resulted in many new products coming to market or entering clinical trials. However, there is a distinct lack of treatments which aim to recreate the complex zonal organization of articular cartilage. Cartilage tissue withstands repetitive strains throughout an individual's lifetime and provides frictionless movement between joints. The structure and composition of its intricately organized extracellular matrix varies with tissue depth to provide optimal resistance to loading, ensure ease of movement, and integrate with the subchondral bone. Each tissue zone is specially designed to resist the load it experiences, and maximize the tissue properties needed for its location. It is unlikely that a homogenous solution to tissue repair will be able to optimally restore the function of such a heterogeneous tissue. For zonal engineering of articular cartilage to become practical, maintenance of phenotypically stable zonal cell populations must be achieved. The chondrocyte phenotype varies considerably by zone, and it is the activity of these cells that help achieve the structural organization of the tissue. This review provides an examination of literature which has studied variations in cellular phenotype between cartilage zones. By doing so, we have identified critical differences between cell populations and highlighted areas of research which show potential in the field. Current research has made the morphological and metabolic variations between these cell populations clear, but an ideal way of maintaining these differences in vitro culture is yet to be established. Combinations of delivered growth factors, mechanical loading, and layered three-dimensional culture systems all show potential for achieving this goal. Furthermore, differentiation of progenitor cell populations into chondrocyte subpopulations may also hold promise for achieving large numbers of zonal chondrocytes. Success of the field lies in establishing methods of retaining phenotypically stable cell populations for in vitro culture.
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Affiliation(s)
- Emily E Coates
- Fischell Department of Bioengineering, University of Maryland, 3238 Jeong H. Kim Engineering Building, College Park, MD 20742, USA
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Breshears LA, Cook JL, Stoker AM, Fox DB, Luther JK. The Effect of Uniaxial Cyclic Tensile Load on Gene Expression in Canine Cranial Cruciate Ligamentocytes. Vet Surg 2010; 39:433-43. [DOI: 10.1111/j.1532-950x.2010.00679.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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van den Boom R, van de Lest CHA, Bull S, Brama RAJ, van Weeren PR, Barneveld A. Influence of repeated arthrocentesis and exercise on synovial fluid concentrations of nitric oxide, prostaglandin E2 and glycosaminoglycans in healthy equine joints. Equine Vet J 2010; 37:250-6. [PMID: 15892235 DOI: 10.2746/0425164054530740] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
REASONS FOR PERFORMING STUDY The importance of osteoarthritis (OA) in the horse and the difficulty in its early diagnosis have led to a search for potential biomarkers of joint disease. If the levels of such markers are to be interpreted accurately, clinicians and researchers need to know whether they are influenced by environmental factors and/or interventions such as exercise and repeated arthrocentesis. OBJECTIVE To investigate the influence of repeated arthrocentesis and exercise on nitric oxide (NO), prostaglandin E2 (PGE2) and glycosaminoglycan (GAG) concentrations in synovial fluid (SF) from normal equine joints. METHODS SF was collected from the left metacarpophalangeal (MCP), radiocarpal and tarsocrural joints of 16 horses. Half of the horses were exercised and arthrocentesis was repeated 14, 14.5, 17 and 24 days after the start of the exercise programme, in both exercised and control horses. Nitric oxide was determined in SF from the MCP joint only and PGE2 and GAG concentrations were determined in SF from all joints. RESULTS Repeated arthrocentesis caused an increase in NO concentration in the MCP joint on Day 145, in PGE2 concentrations in the radiocarpal and tarsocrural joints on Day 145 and the release of GAGs into SF of the MCP and radiocarpal joints on Day 17. Exercise resulted in an increase in PGE2 levels in all joints but did not influence the other parameters measured. POTENTIAL RELEVANCE Repeated arthrocentesis is a potential confounding factor for the use of synovial NO, PGE2 and GAG concentrations as markers of joint disease. Based on this study, such a confounding effect can be avoided if one week or more separates arthrocentesis procedures. Moderate exercise causes a transient rise in PGE2 in SF.
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Affiliation(s)
- R van den Boom
- Departments of Equine Sciences, Faculty of Veterinary Medicine, University of Utrecht, Yalelaan 12, 3584 CM, Utrecht, The Netherlands
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Inflammatory responses to three modes of intense exercise in Standardbred mares – a pilot study. COMPARATIVE EXERCISE PHYSIOLOGY 2009. [DOI: 10.1017/s1478061509294448] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Gupta T, Zielinska B, McHenry J, Kadmiel M, Haut Donahue TL. IL-1 and iNOS gene expression and NO synthesis in the superior region of meniscal explants are dependent on the magnitude of compressive strains. Osteoarthritis Cartilage 2008; 16:1213-9. [PMID: 18439846 DOI: 10.1016/j.joca.2008.02.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2007] [Accepted: 02/22/2008] [Indexed: 02/02/2023]
Abstract
OBJECTIVE Partial meniscectomy is known to cause osteoarthritis (OA) of the underlying cartilage as well as alter the load on the remaining meniscus. Removal of 30-60% of the medial meniscus increases compressive strains from a maximum of approximately 10% to almost 20%. The goal of this study is to determine if meniscal cells produce catabolic molecules in response to the altered loading that results from a partial meniscectomy. METHOD Relative changes in gene expression of interleukin-1 (IL-1), inducible nitric oxide synthase (iNOS) and subsequent changes in the concentration of nitric oxide (NO) released by meniscal tissue in response to compression were measured. Porcine meniscal explants were dynamically compressed for 2 h at 1 Hz to simulate physiological stimulation at either 10% strain or 0.05 MPa stress. Additional explants were pathologically stimulated to either 0% strain, 20% strain or, 0.1 MPa stress. RESULTS iNOS and IL-1 gene expression and NO release into the surrounding media were increased at 20% compressive strain compared to other conditions. Pathological unloading (0% compressive strain) of meniscal explants did not significantly change expression of IL-1 or iNOS genes, but did result in an increased amount of NO released compared to physiological strain of 10%. CONCLUSION These data suggest that meniscectomies which reduce the surface area of the meniscus by 30-60% will increase the catabolic activity of the meniscus which may contribute to the progression of OA.
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Affiliation(s)
- T Gupta
- Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, United States
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Pingguan-Murphy B, El-Azzeh M, Bader DL, Knight MM. Cyclic compression of chondrocytes modulates a purinergic calcium signalling pathway in a strain rate- and frequency-dependent manner. J Cell Physiol 2006; 209:389-97. [PMID: 16883605 DOI: 10.1002/jcp.20747] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Mechanical loading modulates cartilage homeostasis through the control of matrix synthesis and catabolism. However, the mechanotransduction pathways through which chondrocytes detect different loading conditions remain unclear. The present study investigated the influence of cyclic compression on intracellular Ca2+ signalling using the well-characterised chondrocyte-agarose model. Cells labelled with Fluo4 were visualised using confocal microscopy following a period of 10 cycles of compression between 0% and 10% strain. In unstrained agarose constructs, not subjected to cyclic compression, a subpopulation of approximately 45% of chondrocytes exhibited spontaneous global Ca2+ transients with mean transient rise and fall times of 19.4 and 29.4 sec, respectively. Cyclic compression modulated global Ca2+ signalling by increasing the percentage of cells exhibiting Ca2+ transients (population modulation) and/or reducing the rise and fall times of these transients (transient shape modulation). The frequency and strain rate of compression differentially modulated these Ca2+ signalling characteristics providing a potential mechanism through which chondrocytes may distinguish between different loading conditions. Treatment with apyrase, gadolinium and the P2 receptor blockers, suramin and basilen blue, significantly reduced the percentage of cells exhibiting Ca2+ transients following cyclic compression, such that the mechanically induced upregulation of Ca2+ signalling was completely abolished. Thus cyclic compression appears to activate a purinergic pathway involving the release of ATP followed by the activation of P2 receptors causing a combination of extracellular Ca2+ influx and intracellular Ca2+ release. Knowledge of this fundamental cartilage mechanotransduction pathway may lead to improved therapeutic strategies for the treatment of cartilage damage and disease.
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Affiliation(s)
- B Pingguan-Murphy
- Biomedical Engineering Department, Faculty of Engineering, University Malaya, Kuala Lumpur, Malaysia
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Eifler RL, Blough ER, Dehlin JM, Haut Donahue TL. Oscillatory fluid flow regulates glycosaminoglycan production via an intracellular calcium pathway in meniscal cells. J Orthop Res 2006; 24:375-84. [PMID: 16479571 DOI: 10.1002/jor.20028] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Mechanical loading in the form of oscillatory fluid flow-induced shear stress was applied to meniscal cells while the biochemical response [intracellular calcium mobilization and sulfated glycosaminoglycan (GAG) production] was studied. Isolated rabbit meniscal cells were cultured onto microscope slides and placed in a parallel plate flow chamber. Cells were exposed to oscillating fluid flow-induced shear stresses of 4 Pa for sulfated GAG studies and 0-6.5 Pa for calcium studies. The calcium response was monitored using a fluorescent probe and imaging techniques, sulfated GAG production was measured using the modified 1,9-dimethylmethylene blue method, and thapsigargin was used to block intracellular calcium ([Ca2+]i) mobilization. A significant dose-dependent relationship was found for the percentage of cells responding to oscillating fluid flow with an increase in [Ca2+]i versus shear stress level. The percentage of cells responding decreased linearly from 72% +/- 17% at 6.5 Pa to 28% +/- 7% at 2.0 Pa to 2% +/- 1% for baseline no-flow (0 Pa). No differences were found in the amplitude of the calcium response of responding cells for any shear stress level. Oscillating fluid flow-induced shear stresses of 4 Pa produced a significantly greater amount of sulfated GAGs (253 +/- 95 ng GAG/microg cell protein) compared to the no-flow control (158 +/- 86 ng/microg). The addition of thapsigargin to the media inhibited both the intracellular calcium response to oscillating fluid flow (less than 1.5% of the cells responded) and the increase in GAG production following oscillating fluid flow, which was returned to control levels (170 +/- 72 ng/microg). These findings suggest that oscillatory fluid flow-induced shear stress increases intracellular calcium levels and sulfated GAG production. Furthermore, they suggests that calcium may modulate the biochemical pathway that leads to sulfated GAG production.
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Affiliation(s)
- Robert L Eifler
- Department of Mechanical Engineering, Michigan Technological University, Houghton, Michigan 49931, USA
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Wiseman MA, Birch HL, Akmal M, Goodship AE. Segmental variation in the in vitro cell metabolism of nucleus pulposus cells isolated from a series of bovine caudal intervertebral discs. Spine (Phila Pa 1976) 2005; 30:505-11. [PMID: 15738781 DOI: 10.1097/01.brs.0000154615.22311.66] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN This study focuses on the association between cell metabolism and molecular matrix composition of nucleus pulposus (NP) tissue with spine level in sequential bovine caudal intervertebral discs. OBJECTIVE To explore the hypothesis that the molecular composition of NP tissue and corresponding cell metabolism varies with caudal spine. A secondary hypothesis is tested that potential cellular differences are maintained after monolayer culture. SUMMARY OF BACKGROUND DATA In articular cartilage, cell metabolism and molecular matrix composition are influenced by loading history. This may also be a feature of intervertebral discs in series. METHODS NP cells (nonpooled or level pooled) were isolated from four sequential bovine caudal intervertebral discs (levels 3-4, 4-5, 5-6, and 6-7) and cultured in alginate beads immediately or following monolayer culture. Levels of 3H-TdR (proliferation) and 35SO4 (GAG synthesis) incorporation were determined from 14 animals. In a separate set of 6 animals, total content of water, DNA, collagen (and type), GAG (and type) were also determined. RESULTS The rate of 3H-TdR and 35SO4 incorporation in freshly isolated NP cells increased nonlinearly from level 3-4 to 6-7 (P < 0.05). Monolayer cultured cells retained level-specific differences for 35SO4 and 3H-TdR incorporation similar to that of freshly isolated cells. GAG content and chondroitin sulfate proportion decreased distally (P < 0.05); however, total collagen and Type I proportion increased distally (P < 0.05). No significant differences in water or DNA content could be determined. CONCLUSIONS The results support the hypothesis that level-specific differences in NP cell metabolism and molecular composition are dependent on spine level potentially reflecting subtle mechanical differences between levels. Retention of level-specific differences in monolayer may suggest a certain level of cell "programming." This may be important for cellular strategies to repairspecific sites of degeneration.
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Affiliation(s)
- Mike A Wiseman
- Department of Veterinary Basic Sciences, Royal Veterinary College, Hatfield, Hertfordshire, United Kingdom.
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Clements KM, Burton-Wurster N, Lust G. The spread of cell death from impact damaged cartilage: lack of evidence for the role of nitric oxide and caspases. Osteoarthritis Cartilage 2004; 12:577-85. [PMID: 15219573 DOI: 10.1016/j.joca.2004.04.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2003] [Accepted: 04/05/2004] [Indexed: 02/02/2023]
Abstract
UNLABELLED Over 21 days in culture, cell death spreads, both radially and transversely, from loaded to surrounding cartilage. This spread was prevented by physical separation and separate culture post-impact. OBJECTIVE One aim was to determine if nitric oxide (NO) is the intercellular signal mediating cell death. Another aim was to clarify the nature of the cell death, whether caspase mediated apoptosis or necrosis. DESIGN Cyclic impacts were applied to the central 2 mm core of 4 mm canine articular cartilage discs. Post-impact culturing was for 21 days in the presence or absence of the iNOS inhibitor, L-NAME, or the broad-spectrum caspase inhibitor, Z-VAD FMK. Cell death was quantified using the TUNEL assay. Culture media were collected every 2 days for measurements of glycosaminoglycan (GAG) and NO release. RESULTS Cell death spread from the loaded core into the surrounding ring over 21 days in culture. Although L-NAME significantly reduced nitrite release into the culture media of both loaded and control cartilage, the spread of cell death was not prevented. Neither was the spread of cell death prevented by Z-VAD FMK. CONCLUSIONS These data indicate that NO is not acting as an intercellular signalling factor in this in vitro system and that the cell death post-impact is not caspase mediated.
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Affiliation(s)
- Kristen M Clements
- Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Hungerford Hill Road, Ithaca, NY 14853, USA
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