Background:
Platelet-rich plasma (PRP) is used for the treatment of tendinopathy. There are numerous PRP preparations, and the optimal combination of platelets and leukocytes is not known.
...Hypothesis:
Within leukocyte-reduced PRP (lrPRP), there is a plateau effect of platelet concentration, with increasing platelet concentrations being detrimental to extracellular matrix synthesis.
Study Design:
Controlled laboratory study.
Methods:
Different formulations of lrPRP with respect to the platelet:leukocyte ratio were generated from venous blood of 8 horses. Explants of the superficial digital flexor tendon were cultured in lrPRP products for 96 hours. Platelet-derived growth factor–BB (PDGF-BB), tumor necrosis factor−α (TNF-α), transforming growth factor–β1 (TGF-β1), and interleukin-1β (IL-1β) concentrations were determined in the media by enzyme-linked immunosorbent assay. Gene expression in tendon tissue for collagen type I and III (COL1A1 and COL3A1, respectively), matrix metalloproteinase−3 and −13 (MMP-3 and MMP-13, respectively), cartilage oligomeric matrix protein (COMP), and IL-1β was determined. Data were divided into 3 groups of lrPRP based on the ratio of platelets:leukocytes and evaluated to determine the effect of platelet concentration.
Results:
Complete blood counts verified leukocyte reduction and platelet enrichment in all PRP preparations. In the lrPRP preparation, the anabolic growth factors PDGF-BB and TGF-β1 were increased with increasing platelet concentrations, and the catabolic cytokine IL-1β was decreased with increasing platelet concentrations. Increasing the platelet concentration resulted in a significant reduction in COL1A1 and COL3A1 synthesis in tendons.
Conclusion:
Increasing the platelet concentration within lrPRP preparations results in the delivery of more anabolic growth factors and less proinflammatory cytokines, but the biological effect on tendons is diminished metabolism as indicated by a decrease in the synthesis of both COL1A1 and COL3A1. Together, this information suggests that minimizing leukocytes in PRP is more important than maximizing platelet numbers with respect to decreasing inflammation and enhancing matrix gene synthesis.
Clinical Relevance:
This study suggests that reducing leukocytes to minimize catabolic signaling appears to be more important than increasing platelets in an effort to maximize anabolic signaling. Further, a maximum biological threshold of benefit was demonstrated with regard to the number of platelets beyond which further increases in platelet concentration did not result in further anabolic upregulation. In vivo investigations documenting the use of platelets for the treatment of tendinopathy are justified as well as further in vitro characterization of the ideal PRP product for the treatment of tendinopathy and other musculoskeletal applications.
Abstract Articular cartilage is a heterogeneous soft tissue that dissipates and distributes loads in mammalian joints. Though robust, cartilage is susceptible to damage from loading at high rates or ...magnitudes. Such injurious loads have been implicated in degenerative changes, including chronic osteoarthritis (OA), which remains a leading cause of disability in developed nations. Despite decades of research, mechanisms of OA initiation after trauma remain poorly understood. Indeed, although bulk cartilage mechanics are measurable during impact, current techniques cannot access microscale mechanics at those rapid time scales. We aimed to address this knowledge gap by imaging the microscale mechanics and corresponding acute biological changes of cartilage in response to rapid loading. In this study, we utilized fast-camera and confocal microscopy to achieve roughly 85 µm spatial resolution of both the cartilage deformation during a rapid (~3 ms), localized impact and the chondrocyte death following impact. Our results showed that, at these high rates, strain and chondrocyte death were highly correlated ( p <0.001) with a threshold of 8% microscale strain norm before any cell death occurred. Additionally, chondrocyte death had developed by two hours after impact, suggesting a time frame for clinical therapeutics. Moreover, when the superficial layer was removed, strain – and subsequently chondrocyte death – penetrated deeper into the samples ( p <0.001), suggesting a protective role for the superficial layer of articular cartilage. Combined, these results provide insight regarding the detailed biomechanics that drive early chondrocyte damage after trauma and emphasize the importance of understanding cartilage and its mechanics on the microscale.
Cellular response to stimulation governs tissue scale processes ranging from growth and development to maintaining tissue health and initiating disease. To determine how cells coordinate their ...response to such stimuli, it is necessary to simultaneously track and measure the spatiotemporal distribution of their behaviors throughout the tissue. Here, we report on a novel SpatioTemporal Response Analysis IN Situ (STRAINS) tool that uses fluorescent micrographs, cell tracking, and machine learning to measure such behavioral distributions. STRAINS is broadly applicable to any tissue where fluorescence can be used to indicate changes in cell behavior. For illustration, we use STRAINS to simultaneously analyze the mechanotransduction response of 5000 chondrocytes-over 20 million data points-in cartilage during the 50 ms to 4 hours after the tissue was subjected to local mechanical injury, known to initiate osteoarthritis. We find that chondrocytes exhibit a range of mechanobiological responses indicating activation of distinct biochemical pathways with clear spatial patterns related to the induced local strains during impact. These results illustrate the power of this approach.
Fibrin sealants are commonly used in cartilage repair surgeries to adhere cells or grafts into a cartilage defect. Both autologous and commercial allogeneic fibrin sealants are used in cartilage ...repair surgeries, yet there are no studies characterizing and comparing the mechanical properties of fibrin sealants from all-autologous sources. The objectives of this study were to investigate (i) the effect of fibrinogen and thrombin sources on failure mechanics of sealants, and (ii) how sealants affect the adhesion of particulated cartilage graft material (BioCartilage) to surrounding cartilage under physiological loading. Allogeneic thrombin and fibrinogen were purchased (Tisseel), and autologous sources were prepared from platelet-rich plasma (PRP) and platelet-poor plasma (PPP) generated from human blood. To compare failure characteristics, sealants were sandwiched between cartilage explants and pulled to failure. The effect of sealant on the adhesion of BioCartilage graft to cartilage was determined by quantifying microscale strains at the graft-cartilage interface using an in vitro cartilage defect model subjected to shear loading at physiological strains well below failure thresholds. Fibrinogen sources were not equivalent; PRP fibrinogen created sealants that were more brittle, failed at lower strains, and resulted in sustained higher strains through the graft-cartilage interface depth compared to PPP and allogeneic sources. PPP clotted slower compared to PRP, suggesting PPP may percolate deeper into the repair to provide more stability through the tissue depth. There was no difference in bulk failure properties or microscale strains at the graft-cartilage interface between the purely autologous sealant (autologous thrombin + PPP fibrinogen) and the commercial allogeneic sealant. Clinical Significance: All-autologous fibrin sealants fabricated with PPP have comparable adhesion strength as commercial allogeneic sealants in vitro, whereas PRP creates an inferior all-autologous sealant that sustains higher strains through the graft-cartilage interface depth.
Context. Planet formation models have been developed during the past years to try to reproduce what has been observed of both the solar system and the extrasolar planets. Some of these models have ...partially succeeded, but they focus on massive planets and, for the sake of simplicity, exclude planets belonging to planetary systems. However, more and more planets are now found in planetary systems. This tendency, which is a result of radial velocity, transit, and direct imaging surveys, seems to be even more pronounced for low-mass planets. These new observations require improving planet formation models, including new physics, and considering the formation of systems. Aims. In a recent series of papers, we have presented some improvements in the physics of our models, focussing in particular on the internal structure of forming planets, and on the computation of the excitation state of planetesimals and their resulting accretion rate. In this paper, we focus on the concurrent effect of the formation of more than one planet in the same protoplanetary disc and show the effect, in terms of architecture and composition of this multiplicity. Methods. We used an N-body calculation including collision detection to compute the orbital evolution of a planetary system. Moreover, we describe the effect of competition for accretion of gas and solids, as well as the effect of gravitational interactions between planets. Results. We show that the masses and semi-major axes of planets are modified by both the effect of competition and gravitational interactions. We also present the effect of the assumed number of forming planets in the same system (a free parameter of the model), as well as the effect of the inclination and eccentricity damping. We find that the fraction of ejected planets increases from nearly 0 to 8% as we change the number of embryos we seed the system with from 2 to 20 planetary embryos. Moreover, our calculations show that, when considering planets more massive than ~5 M⊕, simulations with 10 or 20 planetary embryos statistically give the same results in terms of mass function and period distribution.
Abstract
Background
Burnout is common among physicians and has detrimental effects on patient care and physician health. Recent editorials call attention to perfectionism in medicine; however, no ...studies to date have examined the effect of perfectionism on burnout in physicians practicing in the United States. This study examined associations among demographics, perfectionism and personality traits, and burnout among practicing physicians.
Methods
This cross-sectional study included general pediatric and pediatric sub-specialist physicians. Out of the 152 physicians contacted, 69 enrolled (Mean
age
= 44.16 ± 9.98; 61% female). Emotional exhaustion, depersonalization, and personal accomplishment burnout were assessed via the Maslach Burnout Inventory. Validated instruments were used to measure personality and perfectionism. Data were analyzed using linear regression models.
Results
Across physicians assessed, 42% reported either high emotional exhaustion burnout or depersonalization burnout. High self-critical perfectionism uniquely predicted both high emotional exhaustion burnout (
B
= 0.55, 95%CI 0.25–0.85) and depersonalization burnout (
B
= 0.18, 95%CI 0.05–0.31). Low conscientiousness (
B
= -6.12; 95%CI, -10.95- -1.28) predicted higher emotional exhaustion burnout and low agreeableness (
B
= -3.20, 95%CI -5.93- -0.46) predicted higher depersonalization burnout.
Conclusions
Perfectionism is understudied among physicians and the current findings suggest that addressing system and individual-level factors that encourage perfectionism is warranted and may reduce risk for physician burnout.
•Priming of MSCs through TLR3 or TLR4 receptors increases their immunomodulatory function.•The polarization paradigm was tested for the first time in Equine MSCs.•In contrast to the polarization ...paradigm, inflammatory macrophages enhances MSC immunomodulation more than TLR3/TLR4 priming.•MHC class II positive MSCs have a greater magnitude of response compared to MHC class II negative MSCs.
Mesenchymal stem cells (MSCs) have the therapeutic potential to treat a variety of inflammatory and degenerative disease processes, however the effects of the tissue environment on MSCs have been overlooked. Our hypothesis was that the immunomodulatory function of MSCs would be impaired by TLR4 stimulation or exposure to inflammatory macrophages, whereas their immunosuppressive properties would be enhanced by TLR3 stimulation.
MSCs were exposed to polyinosinic:polycytidylic acid (poly I:C) to stimulate TLR3 receptors or lipopolysaccharide (LPS) to stimulate TLR4 receptors. MSC1 proinflammatory phenotype in human MSCs was associated with increased IL-6 and IL-8 and MSC2 regenerative phenotype was associated with increased CCL2 and CXCL10. MSC immunomodulatory function was assessed by measuring the ability of primed MSCs to suppress mitogen-stimulated T cell proliferation. Peripheral blood monocytes were isolated using CD14 MACs positive selection, differentiated into macrophages, and polarized using interferon-gamma (IFN-γ). Polarization was confirmed by increased gene expression of TNFα, CCL2, and CXCL10. Inflammatory macrophages were co-cultured with MSCs for 6h, and the resultant MSC phenotype was analyzed as described above.
Both TLR3 and TLR4 priming and co-culture of MSCs with inflammatory macrophages resulted in increased expression of IL-6, CCL2, and CXCL10 in MSCs. Both TLR3 and TLR4 priming or exposure of MSCs to inflammatory macrophages significantly (p<0.05) enhanced their immunomodulatory function, demonstrated by a decrease in T cell proliferation in the presence of poly I:C primed MSCs (11%), LPS primed MSCs (7%), or MSCs exposed to inflammatory macrophages (12%), compared to unstimulated MSCs. Additionally, MHC class II positive MSCs tended to have a greater magnitude of response to priming compared to MHC class II negative MSCs. These results suggest that MSCs can be activated by a variety of inflammatory stimuli, but the recipient injured tissue bed in chronic injuries may not contain sufficient inflammatory signals to activate MSC immunomodulatory function. Enhancement of MSCs immunomodulatory function through inflammatory priming prior to clinical application might improve the therapeutic effect of MSC treatments.
Biologics containing growth factors are frequently used to enhance healing after musculoskeletal injuries. One mechanism of action is thought to be though the ability of biologics to induce homing ...and migration of endogenous mesenchymal stromal cells (MSCs) to a target tissue. However, the ability of biologics to stimulate chemotaxis (directed migration of cells) and chemokinesis (increase rate of cell migration) of MSCs is unknown.
The aim of this study was to directly compare the ability of biologics including platelet rich plasma (PRP) and bone marrow concentrate (BMC) to induce MSC migration. The hypothesis was that leukocyte-low platelet rich plasma (Llo PRP) would induce migration to a greater extent than leukocyte-high platelet rich plasma (Lhi PRP) or BMC.
Bone marrow-derived MSCs were isolated from 8 horses. Migration of MSCs toward a biologic (BMC, Llo PRP, and Lhi PRP) or the positive control platelet derived growth factor (PDGF) was continuously traced and measured for 24hrs using time-lapse microscopy and a microfluidics device. Cell migration, chemotaxis and chemokinesis were determined by measurements of displacement, number of cells migrated, and cell flux.
All biologics resulted in a significantly greater percentage of MSCs migrated compared to the positive control (PDGF). MSCs migrated further toward BMC compared to Llo PRP. Cell migration, measured as cell flux, was greater toward BMC and Lhi PRP than Llo PRP.
The biologics BMC and Lhi PRP elicit greater chemotaxis and chemokinesis of MSCs than Llo PRP. However, all biologics recruited the same number of MSCs suggesting that differences in other regenerative effects, such as growth factor concentration, between biologics should be strongly considered when choosing a biologic for treatment of musculoskeletal injuries. The results of this study have the potential to reduce the need, risks, and costs associated with MSC culture and delivery.
The application of stem cells in regenerative and reparative therapies is emerging in surgery. Published information can lead to an over simplified view of stem cells with respect to their ...definitions, tissues of origin, abilities to differentiate into tissue lineages, and their capacity for functional tissue regeneration. The goals of this review article are to define embryonic and adult stem cells, compare differences between them, and summarize their potential clinical applications.
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