Tolga Taha Sönmez

Platelet-released growth factors can accelerate tenocyte proliferation and activate the anti-oxidant response element

Little is know about the pathophysiology of acute and degenerative tendon injuries. Although most lesions are uncomplicated, treatment is long and unsatisfactory in a considerable number of cases. Besides the common growth factors that were shown to be relevant for tendon integrity more recently protection against oxidative stress was shown to promote tendon healing. To improve tendon regeneration, many have advocated the use of platelet-rich plasma (PRP), a thrombocyte concentrate that can serve as an autologous source of growth factors. In this study, we investigated the effect of platelet-released growth factors (PRGF) on tenocytes. Tenocytes were isolated from the Achilles tendon of postnatal rats. Tenocyte cell cultures were stimulated with PRGF. We used a CyQuant assay and WST assay to analyse tendon cell growth and viability in different concentrations of PRGF. Migration and proliferation of cells grown in PRGF were assessed by a scratch test. A dual-luciferase assay was used to demonstrate the activation of the anti-oxidant response element (ARE) in tenocytes. A positive effect of PRGF could be shown on tendon cell growth and migratory capacity. PRGF activated the Nrf2–ARE pathway in a dose-dependent manner. Here, we provide evidence of a biological effect of PRGF on tenocytes by the promotion of tenocyte growth and activation of the Nrf2–ARE pathway. This is a novel aspect of the action of platelet concentrates on tendon growth.

Dietary vitamin C and E modulates oxidative stress induced-kidney and lens injury in diabetic aged male rats through modulating glucose homeostasis and antioxidant systems.

Diabetes induces oxidative stress in aged human and rat, although daily supplementation of vitamins C and E (VCE) can be beneficial to aged diabetic rats by reducing free radical production. The aim of the present study was to evaluate whether dietary VCE supplementation relieves oxidative stress in streptozotocin (STZ)‐induced diabetic in aged rats. Thirty aged rats were randomly divided into three groups. The first group was used as a control. The second group was made diabetic using a single dose of intraperitoneal STZ. VCE‐supplemented feed was given to aged diabetic rats constituting the third group. On the 21st day of the experiment, blood, lens and kidney samples were taken from all animals. Glutathione peroxidase (GSH‐Px) activity in lens and kidney, reduced glutathione (GSH), vitamin E and β‐carotene concentrations in kidney were lower in the diabetic group than in the control whereas plasma glucose, urea and creatinine, and kidney and lens peroxidation (LP) levels were higher in the diabetic group than in the control. However, kidney and lens LP levels, and plasma glucose, urea and creatinine values were decreased by VCE supplementation. Lens and kidney GSH‐Px activity, kidney GSH, vitamin E and β‐carotene concentrations and erythrocyte counts were increased by VCE treatment. Kidney weights, vitamin A, haemoglobin, hematocrit, leukocyte and platelets values were not changed by diabetes and/or VCE supplementation. VCE ameliorated also diabetes‐induced histopathological changes in kidney. In conclusion, we observed that VCE supplementation is beneficial towards kidney and lens of aged diabetic rats by modulating oxidative and antioxidant systems. Copyright

Compartmentalized Protective and Detrimental Effects of Endogenous Macrophage Migration-Inhibitory Factor Mediated by CXCR2 in a Mouse Model of Myocardial Ischemia/Reperfusion

Objective—Here, we aimed to clarify the role of CXC chemokine receptor (CXCR) 2 in macrophage migration-inhibitory factor (MIF)–mediated effects after myocardial ischemia and reperfusion. As a pleiotropic chemokine-like cytokine, MIF has been identified to activate multiple receptors, including CD74 and CXCR2. In models of myocardial infarction, MIF exerts both proinflammatory effects and protective effects in cardiomyocytes. Similarly, CXCR2 displays opposing effects in resident versus circulating cells. Approach and Results—Using bone marrow transplantation, we generated chimeric mice with Cxcr2−/− bone marrow–derived inflammatory cells and wild-type (wt) resident cells (wt/Cxcr2−/−), Cxcr2−/− cardiomyocytes and wt bone marrow–derived cells (Cxcr2−/−/wt), and wt controls reconstituted with wt bone marrow (wt/wt). All groups were treated with anti-MIF or isotype control antibody before they underwent myocardial ischemia and reperfusion. Blocking MIF increased infarction size and impaired cardiac function in wt/wt and wt/CXCR2−/− mice but ameliorated functional parameters in Cxcr2−/−/wt mice, as analyzed by echocardiography and Langendorff perfusion. Neutrophil infiltration and angiogenesis were unaltered by MIF blockade or Cxcr2 deficiency. Monocyte infiltration was blunted in wt/Cxcr2−/− mice and reduced by MIF blockade in wt/wt and Cxcr2−/−/wt mice. Furthermore, MIF blockade attenuated collagen content in all groups in a CXCR2-independent manner. Conclusions—The compartmentalized and opposing effects of MIF after myocardial ischemia and reperfusion are largely mediated by CXCR2. Although MIF confers protective effects by improving myocardial healing and function through CXCR2 in resident cells, thereby complementing paracrine effects through CD74/AMP-activated protein kinase, it exerts detrimental effects on CXCR2-bearing inflammatory cells by increasing monocyte infiltration and impairing heart function. These dichotomous findings should be considered when developing novel therapeutic strategies to treat myocardial infarction.

Arthroscopy or ultrasound in undergraduate anatomy education: a randomized cross-over controlled trial

BackgroundThe exponential growth of image-based diagnostic and minimally invasive interventions requires a detailed three-dimensional anatomical knowledge and increases the demand towards the undergraduate anatomical curriculum. This randomized controlled trial investigates whether musculoskeletal ultrasound (MSUS) or arthroscopic methods can increase the anatomical knowledge uptake.MethodsSecond-year medical students were randomly allocated to three groups. In addition to the compulsory dissection course, the ultrasound group (MSUS) was taught by eight, didactically and professionally trained, experienced student-teachers and the arthroscopy group (ASK) was taught by eight experienced physicians. The control group (CON) acquired the anatomical knowledge only via the dissection course. Exposure (MSUS and ASK) took place in two separate lessons (75 minutes each, shoulder and knee joint) and introduced standard scan planes using a 10-MHz ultrasound system as well as arthroscopy tutorials at a simulator combined with video tutorials. The theoretical anatomic learning outcomes were tested using a multiple-choice questionnaire (MCQ), and after cross-over an objective structured clinical examination (OSCE). Differences in student’s perceptions were evaluated using Likert scale-based items.ResultsThe ASK-group (n = 70, age 23.4 (20–36) yrs.) performed moderately better in the anatomical MC exam in comparison to the MSUS-group (n = 84, age 24.2 (20–53) yrs.) and the CON-group (n = 88, 22.8 (20–33) yrs.; p = 0.019). After an additional arthroscopy teaching 1% of students failed the MC exam, in contrast to 10% in the MSUS- or CON-group, respectively. The benefit of the ASK module was limited to the shoulder area (p < 0.001). The final examination (OSCE) showed no significant differences between any of the groups with good overall performances. In the evaluation, the students certified the arthroscopic tutorial a greater advantage concerning anatomical skills with higher spatial imagination in comparison to the ultrasound tutorial (p = 0.002; p < 0.001).ConclusionsThe additional implementation of arthroscopy tutorials to the dissection course during the undergraduate anatomy training is profitable and attractive to students with respect to complex joint anatomy. Simultaneous teaching of basic-skills in musculoskeletal ultrasound should be performed by medical experts, but seems to be inferior to the arthroscopic 2D-3D-transformation, and is regarded by students as more difficult to learn. Although arthroscopy and ultrasound teaching do not have a major effect on learning joint anatomy, they have the potency to raise the interest in surgery.

Myocardial regeneration by transplantation of modified endothelial progenitor cells expressing SDF-1 in a rat model

Cell based therapy has been shown to attenuate myocardial dysfunction after myocardial infarction (MI) in different acute and chronic animal models. It has been further shown that stromal‐cell derived factor‐1α (SDF‐1α) facilitates proliferation and migration of endogenous progenitor cells into injured tissue. The aim of the present study was to investigate the role of exogenously applied and endogenously mobilized cells in a regenerative strategy for MI therapy. Lentivirally SDF‐1α‐infected endothelial progenitor cells (EPCs) were injected after 90 min. of ligation and reperfusion of the left anterior descending artery (LAD) intramyocardial and intracoronary using a new rodent catheter system. Eight weeks after transplantation, echocardiography and isolated heart studies revealed a significant improvement of LV function after intramyocardial application of lentiviral with SDF‐1 infected EPCs compared to medium control. Intracoronary application of cells did not lead to significant differences compared to medium injected control hearts. Histology showed a significantly elevated rate of apoptotic cells and augmented proliferation after transplantation of EPCs and EPCs + SDF‐1α in infarcted myocardium. In addition, a significant increased density of CD31+ vessel structures, a lower collagen content and higher numbers of inflammatory cells after transplantation of SDF‐1 transgenic cells were detectable. Intramyocardial application of lentiviral‐infected EPCs is associated with a significant improvement of myocardial function after infarction, in contrast to an intracoronary application. Histological results revealed a significant augmentation of neovascularization, lower collagen content, higher numbers of inflammatory cells and remarkable alterations of apoptotic/proliferative processes in infarcted areas after cell transplantation.

Compartmentalized Protective and Detrimental Effects of Endogenous Migration-Inhibitory Factor Mediated by CXCR2 in a Mouse Model of Myocardial Ischemia/Reperfusion

Objective—Here, we aimed to clarify the role of CXC chemokine receptor (CXCR) 2 in macrophage migration-inhibitory factor (MIF)–mediated effects after myocardial ischemia and reperfusion. As a pleiotropic chemokine-like cytokine, MIF has been identified to activate multiple receptors, including CD74 and CXCR2. In models of myocardial infarction, MIF exerts both proinflammatory effects and protective effects in cardiomyocytes. Similarly, CXCR2 displays opposing effects in resident versus circulating cells. Approach and Results—Using bone marrow transplantation, we generated chimeric mice with Cxcr2−/− bone marrow–derived inflammatory cells and wild-type (wt) resident cells (wt/Cxcr2−/−), Cxcr2−/− cardiomyocytes and wt bone marrow–derived cells (Cxcr2−/−/wt), and wt controls reconstituted with wt bone marrow (wt/wt). All groups were treated with anti-MIF or isotype control antibody before they underwent myocardial ischemia and reperfusion. Blocking MIF increased infarction size and impaired cardiac function in wt/wt and wt/CXCR2−/− mice but ameliorated functional parameters in Cxcr2−/−/wt mice, as analyzed by echocardiography and Langendorff perfusion. Neutrophil infiltration and angiogenesis were unaltered by MIF blockade or Cxcr2 deficiency. Monocyte infiltration was blunted in wt/Cxcr2−/− mice and reduced by MIF blockade in wt/wt and Cxcr2−/−/wt mice. Furthermore, MIF blockade attenuated collagen content in all groups in a CXCR2-independent manner. Conclusions—The compartmentalized and opposing effects of MIF after myocardial ischemia and reperfusion are largely mediated by CXCR2. Although MIF confers protective effects by improving myocardial healing and function through CXCR2 in resident cells, thereby complementing paracrine effects through CD74/AMP-activated protein kinase, it exerts detrimental effects on CXCR2-bearing inflammatory cells by increasing monocyte infiltration and impairing heart function. These dichotomous findings should be considered when developing novel therapeutic strategies to treat myocardial infarction.

The accuracy of computer-assisted primary mandibular reconstruction with vascularized bone flaps: iliac crest bone flap versus osteomyocutaneous fibula flap.

Background The intention of mandibular reconstruction is to restore the complex anatomy with maximum possible functionality and high accuracy. The aim of this study was to evaluate the accuracy of computer-assisted surgery in primary mandibular reconstruction with an iliac crest bone flap compared with an osteomyocutaneous fibula flap. Materials and methods Preoperative computed tomography data of the mandible and the iliac crest or fibula donor site were imported into a specific surgical planning software program. Surgical guides were manufactured using a rapid prototyping technique for translating the virtual plan, including information on the transplant dimensions and shape, into real-time surgery. Using postoperative computed tomography scans and an automatic surface-comparison algorithm, the actual postoperative situation was compared with the preoperative virtual simulation. Results The actual flap position showed a mean difference from the virtual plan of 2.43 mm (standard deviation [SD] ±1.26) and a surface deviation of 39% <2 mm and 15% <1 mm for the iliac crest bone flap, and a mean difference of 2.18 mm (SD ±1.93) and a surface deviation of 60% <2 mm and 37% <1 mm for the osteomyocutaneous fibula flap. The position of the neomandible reconstructed with an osteomyocutaneous fibula flap indicated a mean difference from the virtual plan of 1.25 mm (SD ±1.31) and a surface deviation of 82% <2 mm and 57% <1 mm, in contrast to a mean difference of 1.68 mm (SD ±1.25) and a surface deviation of 63% <2 mm and 38% <1 mm for the neomandible after reconstruction with an iliac crest bone flap. For shape analysis, a similarly high accuracy could be calculated for both flaps. Conclusion Virtual surgical planning is an effective method for mandibular reconstruction with vascularized bone flaps, and can help to restore the anatomy of the mandible with high accuracy in position and shape. It seems that primary mandibular reconstruction with the osteomyocutaneous fibula flap is more accurate compared with the vascularized iliac crest bone flap.

Nrf2 augments skeletal muscle regeneration after ischaemia–reperfusion injury

Skeletal muscles harbour a resident population of stem cells, termed satellite cells (SCs). After trauma, SCs leave their quiescent state to enter the cell cycle and undergo multiple rounds of proliferation, a process regulated by MyoD. To initiate differentiation, fusion and maturation to new skeletal muscle fibres, SCs up‐regulate myogenin. However, the regulation of these myogenic factors is not fully understood. In this study we demonstrate that Nrf2, a major regulator of oxidative stress defence, plays a role in the expression of these myogenic factors. In both promoter studies with myoblasts and a mouse model of muscle injury in Nrf2‐deficient mice, we show that Nrf2 prolongs SC proliferation by up‐regulating MyoD and suppresses SC differentiation by down‐regulating myogenin. Moreover, we show that IL‐6 and HGF, both factors that facilitate SC activation, induce Nrf2 activity in myoblasts. Thus, Nrf2 activity promotes muscle regeneration by modulating SC proliferation and differentiation and thereby provides implications for tissue regeneration.Copyright

The effect of platelet rich plasma on angiogenesis in ischemic flaps in VEGFR2-luc mice

To improve skin flap healing, one promising strategy in reconstructive surgery might be to optimize platelet rich plasma (PRP) bioactivity and the ischemia-altered expression of genes. We studied both the effect of PRP on ischemic flaps, and whether in vivo bioluminescence imaging (BLI) is a suitable method for the longitudinal monitoring of angiogenesis in surgical wounds. Axial murine skin flaps were created in four experimental groups. In vivo measurements of VEGFR2 expression levels were made every other day until the 14th day. The local VEGF level and microvessel density were quantified on the 14th day via ELISA and immunohistochemistry, and flap survival rates were measured. We demonstrated that PRP and induced ischemia have a beneficial influence on angiogenesis and flap healing. Combining the two resulted in a significantly robust increase in angiogenesis and flap survival rate that was corroborated by bioluminescence imaging of VEGFR2 activity. This study shows that angiogenic effects of PRP may be potentialized by the stimulus of induced ischemia during free flap harvesting, and thus the two procedures appear to have a synergistic effect on flap healing. This study further demonstrates that BLI of modulated genes in reconstructive surgery is a valuable model for longitudinal in vivo evaluation of angiogenesis.

Nrf2 deficiency impairs fracture healing in mice.

Oxidative stress plays an important role in wound healing but data relating oxidative stress to fracture healing are scarce. Nuclear factor erythroid 2-related factor 2 (Nrf2) is the major transcription factor that controls the cellular defence essential to combat oxidative stress by regulating the expression of antioxidative enzymes. This study examined the impact of Nrf2 on fracture healing using a standard closed femoral shaft fracture model in wild-type (WT) and Nrf2-knockout (Nrf2-KO)-mice. Healing was evaluated by histology, real-time RT-PCR, µCT and biomechanical measurements. We showed that Nrf2 expression is activated during fracture healing. Bone healing and remodelling were retarded in the Nrf2-KO compared to the WT-mice. Nrf2-KO-mice developed significantly less callus tissue compared to WT-mice. In addition, biomechanical testing demonstrated lower strength against shear stress in the Nrf2-KO-group compared to WT. The expression of vascular endothelial growth factor (VEGF) and osteocalcin is reduced during fracture healing in Nrf2-KO-mice. Taken together, our results demonstrate that Nrf2 deficiency in mice results in impaired fracture healing suggesting that Nrf2 plays an essential role in bone regeneration. Pharmacological activation of Nrf2 may have therapeutic potential for the enhancement of fracture healing.