Michele Temple-Wong - Academia.edu (original) (raw)

Papers by Michele Temple-Wong

Circulation

Introduction: Aortic stenosis (AS) is common, with >= moderate severity ~10% above age 75. Des... more Introduction: Aortic stenosis (AS) is common, with >= moderate severity ~10% above age 75. Despite new therapies, many with AS go undiagnosed due to lack of echo availability and untreated due to improper interpretation. To expand AS diagnosis, we developed an artificial intelligence (AI) algorithm to characterize AS from routine B-mode echo exams without Doppler (AutoAS). Methods: 80,000 de-identified clinical echoes were assembled spanning none, mild, moderate, and severe AS. About 30,000 of these were used to train a convolutional neural network (CNN) using labels derived from a cluster analysis of maximal jet velocity, mean AS gradient, and aortic valve area (AVA). Once labeled, we extracted all available B-mode clips from parasternal long-axis, short axis at aortic level, and apical 5-chamber views, irrespective of image quality. A spatiotemporal CNN was trained to return a probability distribution for none/mild/moderate/severe AS. To assess performance of the model, a hold-...

Articular cartilage is a connective tissue covering the ends of long bones in synovial joints tha... more Articular cartilage is a connective tissue covering the ends of long bones in synovial joints that facilitates low-friction joint articulation. In the case of high loads and low sliding velocities, lubrication of synovial joints occurs in a boundary, surfaceto-surface contact mode, which is governed by interactions of biomolecules, such as hyaluronan (HA) and proteoglycan-4 (PRG4), with cartilage. Injuries increase the risk of osteoarthritis (OA) at a later age, but the mechanism by which this occurs is unclear. While the lubricating ability of synovial fluid in the boundary mode becomes abnormal following injury, the time-dependent changes in SF lubricating and biochemical properties following arthroscopic treatment of acute injury is unknown.

American Journal of Veterinary Research, 2021

OBJECTIVE To assess whether the combination of hyaluronan, sodium chondroitin sulfate, and N-acet... more OBJECTIVE To assess whether the combination of hyaluronan, sodium chondroitin sulfate, and N-acetyl-d-glucosamine (HCSG) lubricates articular cartilage in vitro and modulates joint lubrication in vivo. ANIMALS 16 healthy adult horses. PROCEDURES The effects of HCSG injections on SF lubricant properties and joint health, immediately after injury and 2 weeks later, were analyzed by use an equine osteochondral fracture model of post-traumatic osteoarthritis (OA). Middle carpal joints of adult horses were randomly assigned to 1 of 4 surgical treatment groups as follows: normal nonsurgical group (n = 8), normal sham-surgical group (8), OA-induced surgical group with HCSG injection (8), or OA-induced surgical group with saline (0.9% NaCl) solution injection (8). Synovial fluid was aspirated periodically and analyzed for boundary lubrication function and lubricant molecules. At 17 days, joints were screened for gross pathological changes. RESULTS Induction of OA led to an impairment of SF lubrication function and diminished hyaluronan concentration in a time-dependent manner following surgery, with HCSG injection lessening these effects. Certain friction coefficients approached those of unaffected normal equine SF. Induction of OA also caused synovial hemorrhage at 17 days, which was lower in joints treated with HCSG. CONCLUSIONS AND CLINICAL RELEVANCE After induction of OA, equine SF lubricant function was impaired. Hyaluronan-sodium chondroitin sulfate-N-acetyl-d-glucosamine injection restored lubricant properties at certain time points and reduced pathological joint changes.

Osteoarthritis and Cartilage, 2008

CTS-induced RAS activation resulted in c-Raf phosphorylation. However, c-Raf activation was not m... more CTS-induced RAS activation resulted in c-Raf phosphorylation. However, c-Raf activation was not mediated via PAK phosphorylation and was not inhibited by LY294002. These results suggested that RAS activated c-Raf directly without PI-3-kinase mediated PAK-1 activation. CTS induced c-RAF activation was followed by MEK1/2 (Ser217/221) phosphorylation, which in turn phosphorylated ERK 1/2. Interestingly, Il-1b induced ERK activation was mediated by RAS GTPase activity, however, its activation cascade was distinct from CTS induced ERK1/2 activation. Examination of down stream events revealed that in parallel to ERK activation, CTS induced an increase in c-Myc phosphorylation and upregulation of c-myc, VEGF, ERK 1/2, aggrecan, gene transcription. Furthermore, inhibition of MEK1 by PD98059 inhibited CTS-induced upregulation of c-myc and VEGF mRNA expression. Conclusions: The results demonstrate that the anabolic actions of mechanical signals, at least in part, are mediated via ERK signaling cascade. Furthermore, CTS upregulated RAS GTPase activity to initiate ERK signaling cascade that results in the induction of genes such as VEGF and c-myc that are associated with chondrocyte growth and proliferation.

Arthritis Research & Therapy, 2016

Background: One potential mechanism for early superficial cartilage wear in normal joints is alte... more Background: One potential mechanism for early superficial cartilage wear in normal joints is alteration of the lubricant content and quality of synovial fluid. The purpose of this study was to determine if the concentration and quality of the lubricant, hyaluronan, in synovial fluid: (1) was similar in left and right knees; (2) exhibited similar age-associated trends, whether collected postmortem or antemortem; and (3) varied with age and grade of joint degeneration. Methods: Human synovial fluid of donors (23-91 years) without osteoarthritis was analyzed for the concentrations of protein, hyaluronan, and hyaluronan in the molecular weight ranges of 2.5-7 MDa, 1-2.5 MDa, 0.5-1 MDa, and 0.03-0.5 MDa. Similarity of data between left and right knees was assessed by reduced major axis regression, paired t-test, and Bland-Altman analysis. The effect of antemortem versus postmortem collection on biochemical properties was assessed for age-matched samples by unpaired t-test. The relationships between age, joint grade, and each biochemical component were assessed by regression analysis. Results: Joint grade and the concentrations of protein, hyaluronan, and hyaluronan in the molecular weight ranges of 2.5-7 MDa, 1-2.5 MDa, and 0.5-1 MDa in human synovial fluid showed good agreement between left and right knees and were similar between age-matched patient and cadaver knee joints. There was an age-associated decrease in overall joint grade (-15 %/decade) and concentrations of hyaluronan (-10.5 %/decade), and hyaluronan in the molecular weight ranges of 2.5-7 MDa (-9.4 %/decade), 1-2.5 MDa (-11.3 %/decade), 0.5-1 MDa (-12.5 %/decade), and 0.03-0.5 MDa (-13.0 %/decade). Hyaluronan concentration and quality was more strongly associated with age than with joint grade. Conclusions: The age-related increase in cartilage wear in non-osteoarthritic joints may be related to the altered hyaluronan content and quality of synovial fluid.

Osteoarthritis and Cartilage, 2008

CTS-induced RAS activation resulted in c-Raf phosphorylation. However, c-Raf activation was not m... more CTS-induced RAS activation resulted in c-Raf phosphorylation. However, c-Raf activation was not mediated via PAK phosphorylation and was not inhibited by LY294002. These results suggested that RAS activated c-Raf directly without PI-3-kinase mediated PAK-1 activation. CTS induced c-RAF activation was followed by MEK1/2 (Ser217/221) phosphorylation, which in turn phosphorylated ERK 1/2. Interestingly, Il-1b induced ERK activation was mediated by RAS GTPase activity, however, its activation cascade was distinct from CTS induced ERK1/2 activation. Examination of down stream events revealed that in parallel to ERK activation, CTS induced an increase in c-Myc phosphorylation and upregulation of c-myc, VEGF, ERK 1/2, aggrecan, gene transcription. Furthermore, inhibition of MEK1 by PD98059 inhibited CTS-induced upregulation of c-myc and VEGF mRNA expression. Conclusions: The results demonstrate that the anabolic actions of mechanical signals, at least in part, are mediated via ERK signaling cascade. Furthermore, CTS upregulated RAS GTPase activity to initiate ERK signaling cascade that results in the induction of genes such as VEGF and c-myc that are associated with chondrocyte growth and proliferation.

Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society, 2009

To compare the tensile biomechanical properties of age-matched adult human knee articular cartila... more To compare the tensile biomechanical properties of age-matched adult human knee articular cartilage exhibiting distinct stages of degenerative or osteoarthritic deterioration and to determine the relationships between tensile properties and biochemical and structural properties hypothesized to underlie functional biomechanical deterioration. Age-matched articular cartilage samples, obtained from the lateral and medial femoral condyles (LFC and MFC), exhibited (1) minimal fibrillation, characteristic of normal aging (NLA), (2) overt fibrillation associated with degeneration (DGN), or (3) overt fibrillation associated with osteoarthritis (OA). DGN samples were from knees that exhibited degeneration but not osteophytes while OA samples were from fragments removed during total knee arthroplasty. Cartilage samples were analyzed for tensile properties, cell and matrix composition, and histopathological structure. Differences in tensile, compositional and surface structural properties were...

Orthopaedic journal of sports medicine, 2014

Following various types of naturally-occurring traumatic injury to an articular joint, the lubric... more Following various types of naturally-occurring traumatic injury to an articular joint, the lubricating ability of synovial fluid is impaired, with a correlated alteration in the concentration and/or structure of lubricant molecules, hyaluronan and proteoglycan-4. However, the effect of arthroscopic cartilage repair surgery on synovial fluid lubricant function and composition is unknown. Arthroscopic treatment of full-thickness chondral defects in horses with (1) platelet-enriched fibrin or (2) platelet-enriched fibrin+mesenchymal stem cells leads to equine synovial fluid with impaired lubricant function and hyaluronan and proteoglycan-4 composition. Controlled Laboratory Study. Equine synovial fluid was aspirated from normal joints at a pre-injury state (0 days) and at 10 days and 3 months following fibrin or fibrin+mesenchymal stem cell repair of full thickness chondral defects. Equine synovial fluid samples were analyzed for friction-lowering boundary lubrication of normal articul...

ABSTRACT The mechanism by which altered knee joint motions and loads (e.g., following anterior cr... more ABSTRACT The mechanism by which altered knee joint motions and loads (e.g., following anterior cruciate ligament (ACL) injury) contribute to the development of knee osteoarthritis (OA) is not well understood. One mechanobiological hypothesis is that articular cartilage degradation is initiated when altered knee kinematics increase loading on certain regions of the articular surfaces and decrease loading on other regions [1,2]. If homeostatic loading conditions vary from region to region, then load changes induced by altered kinematics could initiate cartilage degradation in a site-specific manner. This hypothesis is attractive from a computational simulation perspective since it is based on mechanical factors that lend themselves well to physical modeling. If computational simulations could reproduce the knee OA development process, then they potentially could be used to facilitate the design of new or improved treatments for the disease.

Osteoarthritis and Cartilage, 2008

Background-Articular cartilage undergoes age-associated degeneration, resulting in both structura... more Background-Articular cartilage undergoes age-associated degeneration, resulting in both structural and functional biomechanical changes. At early stages of degeneration, wear-lines develop in the general direction of joint movement. With aging, cartilage exhibits a decrease in tensile modulus. The tensile modulus of cartilage has also been related to the orientation of the collagen network, as revealed by split-lines. Objective-To determine the relative contribution of wear-line and split-line orientation on the tensile biomechanical properties of human patellar cartilage from different depths. Methods-In human patellar cartilage, wear-and split-lines are aligned parallel to each other at the proximal facet, and perpendicular to each other at the medial facet. Using superficial, middle, and deep cartilage sections from these two sites, tensile samples were prepared in two orthogonal orientations. Thus, for each depth, there were four groups of samples, with their long axes were aligned either parallel or perpendicular to wear-line direction and also aligned parallel or perpendicular to split-line direction. Uniaxial tensile tests were performed to assess equilibrium and ramp moduli. Results-Tensile equilibrium modulus varied with wear-line orientation (p<0.05) and depth (p<0.001), in an interactive manner (p<0.05), and tended to vary with split-line orientation (p=0.16). In the superficial layer, equilibrium and ramp modulus was higher when the samples were loaded parallel to wear-lines (p<0.05). Conclusion-These results indicate that mild wear (i.e., wear-line formation) at the articular surface has deleterious functional effects on articular cartilage and represents an early aging associated degenerative change. The identification and recognition of functional biomechanical consequences of wear-lines is useful for planning and interpreting tensile biomechanical tests in human articular cartilage.

Osteoarthritis and Cartilage, 2007

Journal of Orthopaedic Research, 2013

The long-term efficacy of osteochondral allografts is due to the presence of viable chondrocytes ... more The long-term efficacy of osteochondral allografts is due to the presence of viable chondrocytes within graft cartilage. Chondrocytes in osteochondral allografts, especially those at the articular surface that normally produce the lubricant proteoglycan-4 (PRG4), are susceptible to storage-associated death. The hypothesis of this study was that the loss of chondrocytes within osteochondral grafts leads to decreased PRG4 secretion, after graft storage and subsequent implant. The objectives were to determine the effect of osteochondral allograft treatment (FROZEN vs. FRESH) on secretion of functional PRG4 after (i) storage, and (ii) 6 months in vivo in adult goats. FROZEN allograft storage reduced PRG4 secretion from cartilage by ∼85% compared to FRESH allograft storage. After 6 months in vivo, the PRG4-secreting function of osteochondral allografts was diminished with prior FROZEN storage by ∼81% versus FRESH allografts and by ∼84% versus non-operated control cartilage. Concomitantly, cellularity at the articular surface in FROZEN allografts was ∼96% lower than FRESH allografts and non-operated cartilage. Thus, the PRG4-secreting function of allografts appears to be maintained in vivo based on its state after storage. PRG4 secretion may be not only a useful marker of allograft performance, but also a biological process protecting the articular surface of grafts following cartilage repair.

The Journal of Bone and Joint Surgery (American), 2012

Intra-articular fractures may hasten posttraumatic arthritis in patients who are typically too ac... more Intra-articular fractures may hasten posttraumatic arthritis in patients who are typically too active and too young for joint replacement. Current orthopaedic treatment principles, including recreating anatomic alignment and establishing articular congruity, have not eliminated posttraumatic arthritis. Additional biomechanical and biological factors may contribute to the development of arthritis. The objective of the present study was to evaluate human synovial fluid for friction-lowering function and the concentrations of putative lubricant molecules following tibial plateau fractures. Synovial fluid specimens were obtained from the knees of eight patients (twenty-five to fifty-seven years old) with a tibial plateau fracture, with five specimens from the injured knee as plateau fracture synovial fluid and six specimens from the contralateral knee as control synovial fluid. Each specimen was centrifuged to obtain a fluid sample, separated from a cell pellet, for further analysis. For each fluid sample, the start-up (static) and steady-state (kinetic) friction coefficients in the boundary mode of lubrication were determined from a cartilage-on-cartilage biomechanical test of friction. Also, concentrations of the putative lubricants, hyaluronan and proteoglycan-4, as well as total protein, were determined for fluid samples. The group of experimental samples were obtained at a mean (and standard deviation) of 11 ± 9 days after injury from patients with a mean age of 45 ± 13 years. Start-up and kinetic friction coefficients demonstrated similar trends and dependencies. The kinetic friction coefficients for human plateau fracture synovial fluid were approximately 100% higher than those for control human synovial fluid. Hyaluronan concentrations were ninefold lower for plateau fracture synovial fluid compared with the control synovial fluid, whereas proteoglycan-4 concentrations were more than twofold higher in plateau fracture synovial fluid compared with the control synovial fluid. Univariate and multivariate regression analysis indicated that kinetic friction coefficient increased as hyaluronan concentration decreased. Knees afflicted with a tibial plateau fracture have synovial fluid with decreased lubrication properties in association with a decreased concentration of hyaluronan.

Journal of Biomechanics, 2011

Though changes in normal joint motions and loads (e.g., following anterior cruciate ligament inju... more Though changes in normal joint motions and loads (e.g., following anterior cruciate ligament injury) contribute to the development of knee osteoarthritis, the precise mechanism by which these changes induce osteoarthritis remains unknown. As a first step toward identifying this mechanism, this study evaluates computational wear simulations of a patellofemoral joint specimen wear tested on a knee simulator machine. A multi-body dynamic model of the specimen mounted in the simulator machine was constructed in commercial computer-aided engineering software. A custom elastic foundation contact model was used to calculate contact pressures and wear on the femoral and patellar articular surfaces using geometry created from laser scan and MR data. Two different wear simulation approaches were investigated-one that wore the surface geometries gradually over a sequence of 10 one-cycle dynamic simulations (termed the "progressive" approach), and one that wore the surface geometries abruptly using results from a single one-cycle dynamic simulation (termed the "non-progressive" approach). The progressive approach with laser scan geometry reproduced the experimentally measured wear depths and areas for both the femur and patella. The less costly non-progressive approach predicted deeper wear depths, especially on the patella, but had little influence on predicted wear areas. Use of MR data for creating the articular and subchondral bone geometry altered wear depth and area predictions by at most 13%. These results suggest that MR-derived geometry may be sufficient for simulating articular cartilage wear in vivo and that a progressive simulation approach may be needed for the patella and tibia since both remain in continuous contact with the femur.

Journal of Biomechanics, 2010

With continued development and improvement of tissue engineering therapies for small articular le... more With continued development and improvement of tissue engineering therapies for small articular lesions, increased attention is being focused on the challenge of engineering partial or whole synovial joints. Joint-scale constructs could have applications in the treatment of large areas of articular damage or in biological arthroplasty of severely degenerate joints. This review considers the roles of shape, loading and motion in synovial joint mechanobiology and their incorporation into the design, fabrication, and testing of engineered partial or whole joints. Incidence of degeneration, degree of impairment, and efficacy of current treatments are critical factors in choosing a target for joint bioengineering. The form and function of native joints may guide the design of engineered jointscale constructs with respect to size, shape, and maturity. Fabrication challenges for joint-scale engineering include controlling chemo-mechano-biological microenvironments to promote the development and growth of multiple tissues with integrated interfaces or lubricated surfaces into anatomical shapes, and joint-scale bioreactors which nurture and stimulate the tissue with loading and motion. Finally, evaluation of load-bearing and tribological properties can range from tissue to joint scale and can focus on biological structure at present or after adaptation.

Circulation

Introduction: Aortic stenosis (AS) is common, with >= moderate severity ~10% above age 75. Des... more Introduction: Aortic stenosis (AS) is common, with >= moderate severity ~10% above age 75. Despite new therapies, many with AS go undiagnosed due to lack of echo availability and untreated due to improper interpretation. To expand AS diagnosis, we developed an artificial intelligence (AI) algorithm to characterize AS from routine B-mode echo exams without Doppler (AutoAS). Methods: 80,000 de-identified clinical echoes were assembled spanning none, mild, moderate, and severe AS. About 30,000 of these were used to train a convolutional neural network (CNN) using labels derived from a cluster analysis of maximal jet velocity, mean AS gradient, and aortic valve area (AVA). Once labeled, we extracted all available B-mode clips from parasternal long-axis, short axis at aortic level, and apical 5-chamber views, irrespective of image quality. A spatiotemporal CNN was trained to return a probability distribution for none/mild/moderate/severe AS. To assess performance of the model, a hold-...

Articular cartilage is a connective tissue covering the ends of long bones in synovial joints tha... more Articular cartilage is a connective tissue covering the ends of long bones in synovial joints that facilitates low-friction joint articulation. In the case of high loads and low sliding velocities, lubrication of synovial joints occurs in a boundary, surfaceto-surface contact mode, which is governed by interactions of biomolecules, such as hyaluronan (HA) and proteoglycan-4 (PRG4), with cartilage. Injuries increase the risk of osteoarthritis (OA) at a later age, but the mechanism by which this occurs is unclear. While the lubricating ability of synovial fluid in the boundary mode becomes abnormal following injury, the time-dependent changes in SF lubricating and biochemical properties following arthroscopic treatment of acute injury is unknown.

American Journal of Veterinary Research, 2021

OBJECTIVE To assess whether the combination of hyaluronan, sodium chondroitin sulfate, and N-acet... more OBJECTIVE To assess whether the combination of hyaluronan, sodium chondroitin sulfate, and N-acetyl-d-glucosamine (HCSG) lubricates articular cartilage in vitro and modulates joint lubrication in vivo. ANIMALS 16 healthy adult horses. PROCEDURES The effects of HCSG injections on SF lubricant properties and joint health, immediately after injury and 2 weeks later, were analyzed by use an equine osteochondral fracture model of post-traumatic osteoarthritis (OA). Middle carpal joints of adult horses were randomly assigned to 1 of 4 surgical treatment groups as follows: normal nonsurgical group (n = 8), normal sham-surgical group (8), OA-induced surgical group with HCSG injection (8), or OA-induced surgical group with saline (0.9% NaCl) solution injection (8). Synovial fluid was aspirated periodically and analyzed for boundary lubrication function and lubricant molecules. At 17 days, joints were screened for gross pathological changes. RESULTS Induction of OA led to an impairment of SF lubrication function and diminished hyaluronan concentration in a time-dependent manner following surgery, with HCSG injection lessening these effects. Certain friction coefficients approached those of unaffected normal equine SF. Induction of OA also caused synovial hemorrhage at 17 days, which was lower in joints treated with HCSG. CONCLUSIONS AND CLINICAL RELEVANCE After induction of OA, equine SF lubricant function was impaired. Hyaluronan-sodium chondroitin sulfate-N-acetyl-d-glucosamine injection restored lubricant properties at certain time points and reduced pathological joint changes.

Osteoarthritis and Cartilage, 2008

CTS-induced RAS activation resulted in c-Raf phosphorylation. However, c-Raf activation was not m... more CTS-induced RAS activation resulted in c-Raf phosphorylation. However, c-Raf activation was not mediated via PAK phosphorylation and was not inhibited by LY294002. These results suggested that RAS activated c-Raf directly without PI-3-kinase mediated PAK-1 activation. CTS induced c-RAF activation was followed by MEK1/2 (Ser217/221) phosphorylation, which in turn phosphorylated ERK 1/2. Interestingly, Il-1b induced ERK activation was mediated by RAS GTPase activity, however, its activation cascade was distinct from CTS induced ERK1/2 activation. Examination of down stream events revealed that in parallel to ERK activation, CTS induced an increase in c-Myc phosphorylation and upregulation of c-myc, VEGF, ERK 1/2, aggrecan, gene transcription. Furthermore, inhibition of MEK1 by PD98059 inhibited CTS-induced upregulation of c-myc and VEGF mRNA expression. Conclusions: The results demonstrate that the anabolic actions of mechanical signals, at least in part, are mediated via ERK signaling cascade. Furthermore, CTS upregulated RAS GTPase activity to initiate ERK signaling cascade that results in the induction of genes such as VEGF and c-myc that are associated with chondrocyte growth and proliferation.

Arthritis Research & Therapy, 2016

Background: One potential mechanism for early superficial cartilage wear in normal joints is alte... more Background: One potential mechanism for early superficial cartilage wear in normal joints is alteration of the lubricant content and quality of synovial fluid. The purpose of this study was to determine if the concentration and quality of the lubricant, hyaluronan, in synovial fluid: (1) was similar in left and right knees; (2) exhibited similar age-associated trends, whether collected postmortem or antemortem; and (3) varied with age and grade of joint degeneration. Methods: Human synovial fluid of donors (23-91 years) without osteoarthritis was analyzed for the concentrations of protein, hyaluronan, and hyaluronan in the molecular weight ranges of 2.5-7 MDa, 1-2.5 MDa, 0.5-1 MDa, and 0.03-0.5 MDa. Similarity of data between left and right knees was assessed by reduced major axis regression, paired t-test, and Bland-Altman analysis. The effect of antemortem versus postmortem collection on biochemical properties was assessed for age-matched samples by unpaired t-test. The relationships between age, joint grade, and each biochemical component were assessed by regression analysis. Results: Joint grade and the concentrations of protein, hyaluronan, and hyaluronan in the molecular weight ranges of 2.5-7 MDa, 1-2.5 MDa, and 0.5-1 MDa in human synovial fluid showed good agreement between left and right knees and were similar between age-matched patient and cadaver knee joints. There was an age-associated decrease in overall joint grade (-15 %/decade) and concentrations of hyaluronan (-10.5 %/decade), and hyaluronan in the molecular weight ranges of 2.5-7 MDa (-9.4 %/decade), 1-2.5 MDa (-11.3 %/decade), 0.5-1 MDa (-12.5 %/decade), and 0.03-0.5 MDa (-13.0 %/decade). Hyaluronan concentration and quality was more strongly associated with age than with joint grade. Conclusions: The age-related increase in cartilage wear in non-osteoarthritic joints may be related to the altered hyaluronan content and quality of synovial fluid.

Osteoarthritis and Cartilage, 2008

CTS-induced RAS activation resulted in c-Raf phosphorylation. However, c-Raf activation was not m... more CTS-induced RAS activation resulted in c-Raf phosphorylation. However, c-Raf activation was not mediated via PAK phosphorylation and was not inhibited by LY294002. These results suggested that RAS activated c-Raf directly without PI-3-kinase mediated PAK-1 activation. CTS induced c-RAF activation was followed by MEK1/2 (Ser217/221) phosphorylation, which in turn phosphorylated ERK 1/2. Interestingly, Il-1b induced ERK activation was mediated by RAS GTPase activity, however, its activation cascade was distinct from CTS induced ERK1/2 activation. Examination of down stream events revealed that in parallel to ERK activation, CTS induced an increase in c-Myc phosphorylation and upregulation of c-myc, VEGF, ERK 1/2, aggrecan, gene transcription. Furthermore, inhibition of MEK1 by PD98059 inhibited CTS-induced upregulation of c-myc and VEGF mRNA expression. Conclusions: The results demonstrate that the anabolic actions of mechanical signals, at least in part, are mediated via ERK signaling cascade. Furthermore, CTS upregulated RAS GTPase activity to initiate ERK signaling cascade that results in the induction of genes such as VEGF and c-myc that are associated with chondrocyte growth and proliferation.

Osteoarthritis and cartilage / OARS, Osteoarthritis Research Society, 2009

To compare the tensile biomechanical properties of age-matched adult human knee articular cartila... more To compare the tensile biomechanical properties of age-matched adult human knee articular cartilage exhibiting distinct stages of degenerative or osteoarthritic deterioration and to determine the relationships between tensile properties and biochemical and structural properties hypothesized to underlie functional biomechanical deterioration. Age-matched articular cartilage samples, obtained from the lateral and medial femoral condyles (LFC and MFC), exhibited (1) minimal fibrillation, characteristic of normal aging (NLA), (2) overt fibrillation associated with degeneration (DGN), or (3) overt fibrillation associated with osteoarthritis (OA). DGN samples were from knees that exhibited degeneration but not osteophytes while OA samples were from fragments removed during total knee arthroplasty. Cartilage samples were analyzed for tensile properties, cell and matrix composition, and histopathological structure. Differences in tensile, compositional and surface structural properties were...

Orthopaedic journal of sports medicine, 2014

Following various types of naturally-occurring traumatic injury to an articular joint, the lubric... more Following various types of naturally-occurring traumatic injury to an articular joint, the lubricating ability of synovial fluid is impaired, with a correlated alteration in the concentration and/or structure of lubricant molecules, hyaluronan and proteoglycan-4. However, the effect of arthroscopic cartilage repair surgery on synovial fluid lubricant function and composition is unknown. Arthroscopic treatment of full-thickness chondral defects in horses with (1) platelet-enriched fibrin or (2) platelet-enriched fibrin+mesenchymal stem cells leads to equine synovial fluid with impaired lubricant function and hyaluronan and proteoglycan-4 composition. Controlled Laboratory Study. Equine synovial fluid was aspirated from normal joints at a pre-injury state (0 days) and at 10 days and 3 months following fibrin or fibrin+mesenchymal stem cell repair of full thickness chondral defects. Equine synovial fluid samples were analyzed for friction-lowering boundary lubrication of normal articul...

ABSTRACT The mechanism by which altered knee joint motions and loads (e.g., following anterior cr... more ABSTRACT The mechanism by which altered knee joint motions and loads (e.g., following anterior cruciate ligament (ACL) injury) contribute to the development of knee osteoarthritis (OA) is not well understood. One mechanobiological hypothesis is that articular cartilage degradation is initiated when altered knee kinematics increase loading on certain regions of the articular surfaces and decrease loading on other regions [1,2]. If homeostatic loading conditions vary from region to region, then load changes induced by altered kinematics could initiate cartilage degradation in a site-specific manner. This hypothesis is attractive from a computational simulation perspective since it is based on mechanical factors that lend themselves well to physical modeling. If computational simulations could reproduce the knee OA development process, then they potentially could be used to facilitate the design of new or improved treatments for the disease.

Osteoarthritis and Cartilage, 2008

Background-Articular cartilage undergoes age-associated degeneration, resulting in both structura... more Background-Articular cartilage undergoes age-associated degeneration, resulting in both structural and functional biomechanical changes. At early stages of degeneration, wear-lines develop in the general direction of joint movement. With aging, cartilage exhibits a decrease in tensile modulus. The tensile modulus of cartilage has also been related to the orientation of the collagen network, as revealed by split-lines. Objective-To determine the relative contribution of wear-line and split-line orientation on the tensile biomechanical properties of human patellar cartilage from different depths. Methods-In human patellar cartilage, wear-and split-lines are aligned parallel to each other at the proximal facet, and perpendicular to each other at the medial facet. Using superficial, middle, and deep cartilage sections from these two sites, tensile samples were prepared in two orthogonal orientations. Thus, for each depth, there were four groups of samples, with their long axes were aligned either parallel or perpendicular to wear-line direction and also aligned parallel or perpendicular to split-line direction. Uniaxial tensile tests were performed to assess equilibrium and ramp moduli. Results-Tensile equilibrium modulus varied with wear-line orientation (p<0.05) and depth (p<0.001), in an interactive manner (p<0.05), and tended to vary with split-line orientation (p=0.16). In the superficial layer, equilibrium and ramp modulus was higher when the samples were loaded parallel to wear-lines (p<0.05). Conclusion-These results indicate that mild wear (i.e., wear-line formation) at the articular surface has deleterious functional effects on articular cartilage and represents an early aging associated degenerative change. The identification and recognition of functional biomechanical consequences of wear-lines is useful for planning and interpreting tensile biomechanical tests in human articular cartilage.

Osteoarthritis and Cartilage, 2007

Journal of Orthopaedic Research, 2013

The long-term efficacy of osteochondral allografts is due to the presence of viable chondrocytes ... more The long-term efficacy of osteochondral allografts is due to the presence of viable chondrocytes within graft cartilage. Chondrocytes in osteochondral allografts, especially those at the articular surface that normally produce the lubricant proteoglycan-4 (PRG4), are susceptible to storage-associated death. The hypothesis of this study was that the loss of chondrocytes within osteochondral grafts leads to decreased PRG4 secretion, after graft storage and subsequent implant. The objectives were to determine the effect of osteochondral allograft treatment (FROZEN vs. FRESH) on secretion of functional PRG4 after (i) storage, and (ii) 6 months in vivo in adult goats. FROZEN allograft storage reduced PRG4 secretion from cartilage by ∼85% compared to FRESH allograft storage. After 6 months in vivo, the PRG4-secreting function of osteochondral allografts was diminished with prior FROZEN storage by ∼81% versus FRESH allografts and by ∼84% versus non-operated control cartilage. Concomitantly, cellularity at the articular surface in FROZEN allografts was ∼96% lower than FRESH allografts and non-operated cartilage. Thus, the PRG4-secreting function of allografts appears to be maintained in vivo based on its state after storage. PRG4 secretion may be not only a useful marker of allograft performance, but also a biological process protecting the articular surface of grafts following cartilage repair.

The Journal of Bone and Joint Surgery (American), 2012

Intra-articular fractures may hasten posttraumatic arthritis in patients who are typically too ac... more Intra-articular fractures may hasten posttraumatic arthritis in patients who are typically too active and too young for joint replacement. Current orthopaedic treatment principles, including recreating anatomic alignment and establishing articular congruity, have not eliminated posttraumatic arthritis. Additional biomechanical and biological factors may contribute to the development of arthritis. The objective of the present study was to evaluate human synovial fluid for friction-lowering function and the concentrations of putative lubricant molecules following tibial plateau fractures. Synovial fluid specimens were obtained from the knees of eight patients (twenty-five to fifty-seven years old) with a tibial plateau fracture, with five specimens from the injured knee as plateau fracture synovial fluid and six specimens from the contralateral knee as control synovial fluid. Each specimen was centrifuged to obtain a fluid sample, separated from a cell pellet, for further analysis. For each fluid sample, the start-up (static) and steady-state (kinetic) friction coefficients in the boundary mode of lubrication were determined from a cartilage-on-cartilage biomechanical test of friction. Also, concentrations of the putative lubricants, hyaluronan and proteoglycan-4, as well as total protein, were determined for fluid samples. The group of experimental samples were obtained at a mean (and standard deviation) of 11 ± 9 days after injury from patients with a mean age of 45 ± 13 years. Start-up and kinetic friction coefficients demonstrated similar trends and dependencies. The kinetic friction coefficients for human plateau fracture synovial fluid were approximately 100% higher than those for control human synovial fluid. Hyaluronan concentrations were ninefold lower for plateau fracture synovial fluid compared with the control synovial fluid, whereas proteoglycan-4 concentrations were more than twofold higher in plateau fracture synovial fluid compared with the control synovial fluid. Univariate and multivariate regression analysis indicated that kinetic friction coefficient increased as hyaluronan concentration decreased. Knees afflicted with a tibial plateau fracture have synovial fluid with decreased lubrication properties in association with a decreased concentration of hyaluronan.

Journal of Biomechanics, 2011

Though changes in normal joint motions and loads (e.g., following anterior cruciate ligament inju... more Though changes in normal joint motions and loads (e.g., following anterior cruciate ligament injury) contribute to the development of knee osteoarthritis, the precise mechanism by which these changes induce osteoarthritis remains unknown. As a first step toward identifying this mechanism, this study evaluates computational wear simulations of a patellofemoral joint specimen wear tested on a knee simulator machine. A multi-body dynamic model of the specimen mounted in the simulator machine was constructed in commercial computer-aided engineering software. A custom elastic foundation contact model was used to calculate contact pressures and wear on the femoral and patellar articular surfaces using geometry created from laser scan and MR data. Two different wear simulation approaches were investigated-one that wore the surface geometries gradually over a sequence of 10 one-cycle dynamic simulations (termed the "progressive" approach), and one that wore the surface geometries abruptly using results from a single one-cycle dynamic simulation (termed the "non-progressive" approach). The progressive approach with laser scan geometry reproduced the experimentally measured wear depths and areas for both the femur and patella. The less costly non-progressive approach predicted deeper wear depths, especially on the patella, but had little influence on predicted wear areas. Use of MR data for creating the articular and subchondral bone geometry altered wear depth and area predictions by at most 13%. These results suggest that MR-derived geometry may be sufficient for simulating articular cartilage wear in vivo and that a progressive simulation approach may be needed for the patella and tibia since both remain in continuous contact with the femur.

Journal of Biomechanics, 2010

With continued development and improvement of tissue engineering therapies for small articular le... more With continued development and improvement of tissue engineering therapies for small articular lesions, increased attention is being focused on the challenge of engineering partial or whole synovial joints. Joint-scale constructs could have applications in the treatment of large areas of articular damage or in biological arthroplasty of severely degenerate joints. This review considers the roles of shape, loading and motion in synovial joint mechanobiology and their incorporation into the design, fabrication, and testing of engineered partial or whole joints. Incidence of degeneration, degree of impairment, and efficacy of current treatments are critical factors in choosing a target for joint bioengineering. The form and function of native joints may guide the design of engineered jointscale constructs with respect to size, shape, and maturity. Fabrication challenges for joint-scale engineering include controlling chemo-mechano-biological microenvironments to promote the development and growth of multiple tissues with integrated interfaces or lubricated surfaces into anatomical shapes, and joint-scale bioreactors which nurture and stimulate the tissue with loading and motion. Finally, evaluation of load-bearing and tribological properties can range from tissue to joint scale and can focus on biological structure at present or after adaptation.