Activation of SIRT1 by hyperbaric oxygenation promotes recovery of motor dysfunction in spinal cord injury rats.

BACKGROUND: Hyperbaric oxygenation (HBO) therapy can improve locomotor dysfunction following spinal cord injury (SCI). Emerging evidence has demonstrated that sirtuin1 (SIRT1) exerts protective effects on neurons. However, whether HBO alleviates locomotor dysfunction by regulating SIRT1 is unclear. METHODS: The traumatic SCI animal model was performed on the adult Sprague-Dawley rats. The Basso, Beattie Bresnahan (BBB) locomotor rating scale was used to evaluate the open-field locomotor function. Western blot, real-time quantitative reverse transcription polymerase chain reaction, SIRT1 activity assay, and enzyme-linked immunosorbent assays were performed to explore the molecular mechanisms. RESULTS: We found that series HBO therapy significantly improved locomotor dysfunction and ameliorated the decreased mRNA, protein, and activity of spinal cord SIRT1 induced by traumatic SCI injury in rats. In addition, intraperitoneal injection of SIRT1 inhibitor EX-527 abolished the beneficial effects of series HBO treatment on locomotor deficits. Importantly, series HBO treatment following the traumatic SCI injury inhibited the inflammatory cascade and apoptosis-related protein, which was retained by EX-527 and enhanced by SRT1720. Furthermore, EX-527 blocked the enhanced induction of autophagy series with the HBO application. CONCLUSION: These findings demonstrated a new mechanism for series HBO therapy involving activation of SIRT1 and subsequent modulation of the inflammatory cascade, apoptosis, and autophagy, which contributed to the recovery of motor dysfunction.

Hypertension and cystatin C account for sex differences in serum homocysteine levels in acute coronary syndrome subjects with normal serum creatinine.

BACKGROUND: Hyperhomocysteinemia is one of cardiovascular disease risk factors and fasting homocysteine levels are significantly elevated in male compared to female acute coronary syndrome (ACS) patients with normal renal function. However, it is not known the sex related determinants of plasma homocysteine levels in ACS subjects without renal dysfunction. METHODS: A total of 165 ACS participants with normal plasma creatinine who underwent coronary angiography were included in the present study. Clinical parameters, homocysteine, fasting glucose and lipid profile, hemoglobin, white blood cell, platelets, creatinine, cystatin C, blood urea nitrogen, uric acid (UA), and albumin were measured. Multivariate linear regression analyses were used to recognize the predictive factors for homocysteine. RESULTS: The levels of plasma homocysteine were significantly higher in men than in women (P < 0.0001). In males, homocysteine (log10) was positively associated with hypertension (r = 0.569, P < 0.001), creatinine (r = 0.367, P < 0.001) and cystatin C (log10) (r = 0.333, P = 0.001). In females, homocysteine (log10) was positively correlated with age (r = 0.307, P = 0.107), hypertension (r = 0.456, P < 0.001), creatinine (r = 0.341, P = 0.008), cystatin C (log10) (r = 0.429, P = 0.001) and UA (r = 0.569, P < 0.001) whereas was negatively associated with LDL-C (r = - 0.298, P = 0.021) and ApoB (r = - 0.273, P = 0.033). Parameters up to statistical significance in males or females were incorporated into the stepwise linear regression models. In men, hypertension (P < 0.001) and creatinine (P = 0.031) were independently related to homocysteine. Most of the variability of homocysteine levels in males were only determined by hypertension. In women, cystatin C (log10) (P = 0.004) and hypertension (P = 0.005) were independently related to homocysteine (log10). Plasma cystatin C had a higher explanatory value than hypertension in females. CONCLUSIONS: Hypertension and cystatin C could explain most of the sex differences in serum homocysteine levels in ACS subjects with normal serum creatinine. This finding suggested the importance of making different strategies in males and females to manage hyperhomocysteinemia effectively in ACS subjects without renal dysfunction.

Visfatin is negatively associated with coronary artery lesions in subjects with impaired fasting glucose.

It is not determined whether serum visfatin levels are related to the presence and severity of coronary artery disease (CAD) in non-diabetic subjects. In this study, a total of 65 consecutive non-diabetic participants who underwent coronary angiography were enrolled. Serum visfatin and fasting glucose, as well as the serum total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglyceride, were measured in all participants before the procedure. The extent of coronary artery lesions was determined by Gensini score. Serum visfatin levels were significantly lower in patients with CAD compared to participants with normal coronary arteries. Inversely, the circulating levels of fasting glucose were found to be elevated in patients with CAD compared with the control subjects. Multivariable logistic regression analysis demonstrated that visfatin and impaired fasting glucose (IFG) were independently associated with the presence of CAD in non-diabetics. No significant relationship was found between serum visfatin and fasting glucose levels in IFG subjects. However, there was a negative association between visfatin concentrations and Gensini score in participants with IFG. Both circulating visfatin concentrations and IFG are independently associated with CAD in non-diabetics. Serum visfatin levels are negatively related to the angiographic severity of CAD in subjects with IFG.

The effect of flipped classroom in multiple clinical skills training for clinical interns on Objective Structured Clinical Examinations (OSCE).

AIMS: The flipped classroom (FC) is a hybrid approach, combining online learning and face-to-face classroom activities. To comprehensively evaluate the role of the Flipped Classroom (FC) model in clinical skills teaching of medical interns and investigate the acceptance and recognition of FC and Objective Structured Clinical Examinations (OSCE). METHODS: In the teaching of clinical skills, the students were further grouped into two groups- A and B (A = 37, B = 42), using a computer-based random digital method. group A adopted the traditional classroom (TC) model, and group B adopted the FC model. OSCE was used to assess the clinical skills of the two groups of interns. Two independent sample t-test was used to analyze the difference of participant's demographic data and OSCE scores between the two different teaching model. We sent FC questionnaires to group A and OSCE questionnaires to groups A and B. RESULTS: The score of OSCE in group B was higher than that in group A (P = 0.024), especially in the heart physical examination (P < 0.050), lung physical examination (P < 0.050), and abdominal physical examination (P < 0.050). The result of the FC questionnaires showed that regarding online courses, most students in group B thought watching videos was a good way to prepare for class (97.6%), For offline courses, most medical interns said that it enhanced their learning ability (88.1%), and they could accept this form of teaching (85.7%). As for the form of OSCE questionnaires, most people in group A and B said that they knew more about this form of assessment (81.0%), that it truly reflected the clinical ability (82.3%). CONCLUSIONS: FC model has shown good results in clinical skills training, while FC and OSCE can be further promoted in future teaching and assessment.

HBO-PC Promotes Locomotor Recovery by Reducing Apoptosis and Inflammation in SCI Rats: The Role of the mTOR Signaling Pathway.

Hyperbaric oxygen preconditioning (HBO-PC) has beneficial effects on the promotion of locomotor recovery by reducing apoptosis and inflammation after traumatic spinal cord injury (SCI). The mammalian target of rapamycin (mTOR) signaling pathway has been implicated in apoptosis and inflammation in many pathophysiological conditions. However, whether HBO-PC improves traumatic SCI-induced locomotor dysfunction by regulating the mTOR signaling pathway and its downstream molecules remains unknown. In the present study, we found that HBO-PC significantly promoted SCI-induced hind-limb locomotor recovery and increased the amplitude and potential of motor evoked potential. Magnetic resonance imaging showed that spinal cavitation or atrophy caused by SCI was obviously alleviated by HBO-PC therapy. Histological analysis showed that the changes in spinal cord neural structure in SCI rats were markedly restored by HBO-PC treatment. Western blot analysis showed that the SCI-induced enhanced levels of p-mTOR, inflammatory cytokines and apoptosis in the spinal cord were abrogated after administration of HBO-PC. Furthermore, intrathecal administration of an mTOR agonist reversed the effects of HBO-PC on locomotor function recovery, p-NF-κB p65 and p-p70S6K levels, inflammation and apoptosis. These findings indicated a new mechanism by which HBO-PC therapy suppressed inflammation and apoptosis through inactivation of the mTOR signaling pathway, which contributed to motor disability in SCI rats.

Acetylbritannilactone attenuates contrast-induced acute kidney injury through its anti-pyroptosis effects.

Contrast-induced acute kidney injury (CI-AKI) is a severe complication caused by intravascular applied radial contrast media (CM). Pyroptosis is a lytic type of cell death inherently associated with inflammation response and the secretion of pro-inflammatory cytokines following caspase-1 activation. The aim of the present study was to investigate the protective effects of acetylbritannilactone (ABL) on iopromide (IOP)-induced acute renal failure and reveal the underlying mechanism. In vivo and in vitro, IOP treatment caused renal damage and elevated the caspase-1 (+) propidium iodide (PI) (+) cell count, interleukin (IL)-1ß and IL-18 levels, lactate dehydrogenase (LDH) release, and the relative expression of nucleotide-binding domain, leucine-rich repeat containing protein 3 (NLRP3), apoptosis-associated speck-like protein (ASC), and gasdermin D (GSDMD), suggesting that IOP induces AKI via the activation of pyroptosis. Furthermore, the pretreatment of ABL partly mitigated the CI-AKI, development of pyroptosis, and subsequent kidney inflammation. These data revealed that ABL partially prevents renal dysfunction and reduces pyroptosis in CI-AKI, which may provide a therapeutic target for the treatment of CM-induced AKI.

Liraglutide protects high-glucose-stimulated fibroblasts by activating the CD36-JNK-AP1 pathway to downregulate P4HA1.

BACKGROUND: Diabetic cardiomyopathy (DCM) is a serious complication of diabetes mellitus. It's known that glucagon-like peptide-1 (GLP-1) and prolyl 4-hydroxylase subunit alpha-1 (P4HA1) have significant effect on cardiovascular function, but their interaction in cardiac fibroblasts (CFs) is still being unraveled. METHODS AND RESULTS: The present study demonstrated that glucose promotes CFs proliferation and cardiac fibrosis. Using qRT-PCR, Western blot, CCK-8, EdU, flow cytometry, wound healing and Transwell assays to explore the functions of liraglutide and P4HA1 in high-glucose (HG)-induced CFs, we proved that liraglutide as well as silencing of P4HA1 inhibited cell proliferation, migration and invasion, and promoted cell cycle arrest and apoptosis in HG-induced CFs. In addition, liraglutide downregulated P4HA1 expression, upregulated CD36 and P-JNK expression levels, and enhanced the DNA binding activity of AP-1 on P4HA1. Inhibition of CD36 or p--JNK promoted P4HA1 expression. CONCLUSIONS: Liraglutide may down-regulate P4HA1 expression at least partly though CD36-JNK-AP1 pathway, thereby reducing myocardial fibrosis. Therefore, our study provides novel insight into the molecular mechanism and function of liraglutide in HG-mediated CFs.

Liraglutide alleviates cardiac fibrosis through inhibiting P4hα-1 expression in STZ-induced diabetic cardiomyopathy.

Diabetic cardiomyopathy is an important contributor to morbidity and mortality of diabetic patients by causing heart failure. Interstitial and perivascular fibrosis plays a crucial role in diabetic cardiomyopathy. However, there is a lack of effective specific treatments available for diabetic cardiomyopathy. In the present study, we aim to explore the effects of Liraglutide, a GLP-1 analogue, on diabetic cardiomyopathy in STZ-induced diabetic rats fed with high-fat diet. A total of 60 male Wistar rats were randomly assigned to three groups, i.e. normal group, model group, and Liraglutide group, with 20 rats in each group. Serum levels of TC, TG, LDL-C, NEFA, and hydroxyproline were measured using commercial kits. Cardiac function was evaluated by QRS waves, LVEDd, LVESd, and LVEF. Myocardial fibrosis was measured by immunohistochemistry. Our results demonstrated that chronic administration of Liraglutide decreased the level of blood glucose and significantly alleviated lipid metabolic disturbance compared with the model group. Furthermore, Liraglutide was found to improve the damaged cardiac function. In line with this, we also found that the alleviation of cardiac dysfunction was associated with the decreased fibrosis in diabetic myocardial tissues, which was reflected by the decreased expressions of P4hα-1, COL-1, COL-3, MMP-1, and MMP-9. Our results thus suggest that Liraglutide might have a myocardial protective effect by inhibiting P4hα-1-mediated myocardial fibrosis.

Predictive value of fasting blood glucose for serious coronary atherosclerosis in non-diabetic patients.

OBJECTIVE: To determine if high fasting blood glucose (FBG) level is an independent predictor of serious coronary lesions in patients with coronary artery disease (CAD). METHODS: We enrolled 64 patients who had symptoms of chest discomfort and who underwent coronary angiography. FBG was determined from blood samples and the extent of coronary artery lesions was analyzed according to Gensini score. We examined the relationships among diabetes, FBG, and coronary artery severity. RESULTS: Diabetes and FBG were significantly and positively related to Gensini score. Diabetes, but not FBG, was independently correlated with the occurrence of a Gensini score >41. However, FBG was significantly associated with Gensini score >41 in non-diabetic patients. CONCLUSION: Hyperglycemia is an independent predictor of severe CAD in non-diabetic patients. Clinicians should be aware of this and should carry out appropriate early interventions.

Growth Hormone-Releasing Hormone and Its Analogues: Significance for MSCs-Mediated Angiogenesis.

Mesenchymal stromal cells (MSCs) are promising candidates for regenerative medicine because of their multipotency, immune-privilege, and paracrine properties including the potential to promote angiogenesis. Accumulating evidence suggests that the inherent properties of cytoprotection and tissue repair by native MSCs can be enhanced by various preconditioning stimuli implemented prior to cell transplantation. Growth hormone-releasing hormone (GHRH), a stimulator in extrahypothalamus systems including tumors, has attracted great attentions in recent years because GHRH and its agonists could promote angiogenesis in various tissues. GHRH and its agonists are proangiogenic in responsive tissues including tumors, and GHRH antagonists have been tested as antitumor agents through their ability to suppress angiogenesis and cell growth. GHRH-R is expressed by MSCs and evolving work from our laboratory indicates that treatment of MSCs with GHRH agonists prior to cell transplantation markedly enhanced the angiogenic potential and tissue reparative properties of MSCs through a STAT3 signaling pathway. In this review we summarized the possible effects of GHRH analogues on cell growth and development, as well as on the proangiogenic properties of MSCs. We also discussed the relationship between GHRH analogues and MSC-mediated angiogenesis. The analyses provide new insights into molecular pathways of MSCs-based therapies and their augmentation by GHRH analogues.

Amlodipine and atorvastatin improve ventricular hypertrophy and diastolic function via inhibiting TNF-α, IL-1ß and NF-κB inflammatory cytokine networks in elderly spontaneously hypertensive rats.

This study aimed to examine the effects of amlodipine and atorvastatin alone or in combination on the regulation of inflammatory cytokines and the underlying mechanisms in elderly spontaneously hypertensive (SH) rats. The level of serum hs-CRP was detected with ELISA. The serum TNF-α and IL-1ß levels were assessed by radioimmunity assay (RIA). Cardiac inflammatory cell infiltration was observed by HE staining. The protein levels of TNF-α, IL-1ß, of NF-κB P65 and IκBα were detected by immunoblotting. The intracellular localization of NF-κB p65 was observed using immunohistochemistry. Amlodipine or atorvastatin obviously ameliorated the myocardial inflammatory cell infiltration in SH rats, which was further improved by combinatorial treatment with amlodipine and atorvastatin. Either amlodipine or atorvastatin decreased plasma IL-1ß content in SH rats, but there was no significant difference when compared with untreated SH rats. However, the combination of amlodipine and atorvastatin significantly decreased plasma IL-1ß level in SH rats. Moreover, amlodipine or atorvastatin intervention significantly reduced myocardial TNF-α and IL-1ß protein levels in SH rats, which was further suppressed by the combination of amlodipine and atorvastatin. In addition, amlodipine or atorvastatin inhibited the activity of NF-κB signaling in SH rats, which was further suppressed by combinatorial treatment. Furthermore, amlodipine or atorvastatin restored the activity of IκB-α in SH rats, which was enhanced by combinatorial treatment. Our results demonstrated amlodipine and atorvastatin improved ventricular hypertrophy and diastolic function possibly through the intervention of TNF-α, IL-1ß, NF-κB/IκB inflammatory cytokine network. Our study suggests that amlodipine combined with atorvastatin may have additive effect on inhibiting inflammatory response.

Isolation and culture of rat aortic valve interstitial cells.

OBJECTIVE: Culturing aortic valve interstitial cells is a useful way to investigate the physiology and pathology of the aortic valve at the cellular level. The culture methods of the cells have been established in many species. However, the previous methods need some improvements. METHODS: We evaluated various techniques with regard to the isolation of Sprague-Dawley (SD) rat aortic valve interstitial cells and established suitable conditions about the culture and passage of the primary cells. The specimens from the aortic valve were processed by tissue explant methods before seeding them onto the dishes. RESULTS: The cells obtained emerged from the explants after 2 to 3 days and stained positive for α-SMA and vimentin protein. Moreover, transmission electron microscopy images showed that the cells had abundant mitochondria, prominent rough endoplasmic reticulum, and plentiful myofilaments. CONCLUSION: In the present study, we provided reliable and efficient methods for the isolation and culture of rat aortic valve interstitial cells that could serve for in vitro studies on aortic valve physiology and pathophysiology.

Heparanase released from mesenchymal stem cells activates integrin beta1/HIF-2alpha/Flk-1 signaling and promotes endothelial cell migration and angiogenesis.

Heparanase plays important roles in tumor angiogenesis. Our previous study demonstrated that hypoxic preconditioning (HPC) enhanced the angiogenic and therapeutic effects of mesenchymal stem cells (MSCs), effects that were paralleled by enhanced heparanase expression. This study was designed to elucidate the role of heparanase in the improved therapeutic properties of HPC-MSCs and to explore underlying mechanisms using an ischemic rat hind limb model. MSCs transfected with heparanase (MSC(hpa) ) or empty vector (MSC(null) ) were delivered by intramuscular injections to ischemic hind limbs. Hind limbs that received MSC(hpa) recovered blood flow more rapidly at 7 days and acquired higher capillary density at 14 days compared with MSC(null) . Conditioned medium from MSC(hpa) increased endothelial cell migration and promoted greater tube formation relative to that from the MSC(null) groups. Vascular endothelial growth factor receptor 2 (VEGFR2, Flk-1) and its downstream signaling pathway (p38MAPK/HSP27) were significantly increased in human umbilical vein endothelial cells (HUVECs) after treatment with MSC(hpa) conditioned medium. Each of these responses was decreased by cocultured with MSC(hpa-KD) conditioned medium. MSC(hpa) conditioned medium activated hypoxia-inducible factor-2α (HIF-2α) and increased in parallel the transcript level of Flk-1 as determined by chromatin immunoprecipitation-PCR and luciferase assays. Analyses of integrin expression revealed an important role for integrin ß1 in the regulation of HIF-2α. All angiogenic effects of MSC(hpa) conditioned medium were abolished by knockdown of integrin ß1, HIF-2α, and Flk-1 in HUVECs with selective shRNAs. These findings identify heparanse as a key regulator of angiogenesis by MSCs. We propose a novel pathway wherein heparanse sequentially activates integrin ß1, HIF-2α, Flk-1, and p38MAPK/HSP27 with corresponding enhancement of angiogenesis.

Hypoxia preconditioned mesenchymal stem cells prevent cardiac fibroblast activation and collagen production via leptin.

AIMS: Activation of cardiac fibroblasts into myofibroblasts constitutes a key step in cardiac remodeling after myocardial infarction (MI), due to interstitial fibrosis. Mesenchymal stem cells (MSCs) have been shown to improve post-MI remodeling an effect that is enhanced by hypoxia preconditioning (HPC). Leptin has been shown to promote cardiac fibrosis. The expression of leptin is significantly increased in MSCs after HPC but it is unknown whether leptin contributes to MSC therapy or the fibrosis process. The objective of this study was to determine whether leptin secreted from MSCs modulates cardiac fibrosis. METHODS: Cardiac fibroblast (CF) activation was induced by hypoxia (0.5% O2). The effects of MSCs on fibroblast activation were analyzed by co-culturing MSCs with CFs, and detecting the expression of α-SMA, SM22α, and collagen IαI in CFs by western blot, immunofluorescence and Sirius red staining. In vivo MSCs antifibrotic effects on left ventricular remodeling were investigated using an acute MI model involving permanent ligation of the left anterior descending coronary artery. RESULTS: Co-cultured MSCs decreased fibroblast activation and HPC enhanced the effects. Leptin deficit MSCs from Ob/Ob mice did not decrease fibroblast activation. Consistent with this, H-MSCs significantly inhibited cardiac fibrosis after MI and mediated decreased expression of TGF-ß/Smad2 and MRTF-A in CFs. These effects were again absent in leptin-deficient MSCs. CONCLUSION: Our data demonstrate that activation of cardiac fibroblast was inhibited by MSCs in a manner that was leptin-dependent. The mechanism may involve blocking TGF-ß/Smad2 and MRTF-A signal pathways.

Transplantation of SIRT1-engineered aged mesenchymal stem cells improves cardiac function in a rat myocardial infarction model.

BACKGROUND: Previous studies have demonstrated that biological aging has a negative influence on the therapeutic effects of mesenchymal stem cells (MSCs)-based therapy. Using a rat myocardial infarction (MI) model, we tested the hypothesis that silent mating type information regulation 2 homolog 1 (SIRT1) may ameliorate the phenotype and improve the function of aged MSCs and thus enhance the efficacy of aged MSCs-based therapy. METHODS: Sixty female rats underwent left anterior descending coronary artery ligation and were randomly assigned to receiving: intramyocardial injection of cell culture medium (DMEM group); SIRT1 overexpression vector-treated aged MSCs (SIRT1-aged MSCs group) obtained from aged male SD rats or empty vector-treated aged MSCs (vector-aged MSCs group). Another 20 sham-operated rats that underwent open-chest surgery without coronary ligation or any other intervention served as controls. RESULTS: SIRT1-aged MSC group exhibited enhanced blood vessel density in the border zone of MI hearts, which was associated with reduced cardiac remodeling, leading to improved cardiac performance. Consistent with the in vivo data, our in vitro experiments also demonstrated that SIRT1 overexpression ameliorated aged MSCs senescent phenotype and recapitulated the pro-angiogenesis property of MSCs and conferred the anti-stress response capabilities, as indicated by increases in pro-angiogenic factors, angiopoietin 1 (Ang1) and basic fibroblast growth factor (bFGF), expressions and a decrease in anti-angiogenic factor thrombospondin-1 (TBS1) at mRNA levels, and increases in Bcl-2/Bax ratio at protein level. CONCLUSIONS: Up-regulating SIRT1 expression could enhance the efficacy of aged MSCs-based therapy for MI as it relates to the amelioration of senescent phenotype and hence improved biological function of aged MSCs.

Leptin signaling is required for augmented therapeutic properties of mesenchymal stem cells conferred by hypoxia preconditioning.

Hypoxia preconditioning enhances the therapeutic effect of mesenchymal stem cells (MSCs). However, the mechanism underlying hypoxia-induced augmentation of the protective effect of MSCs on myocardial infarction (MI) is poorly understood. We show that hypoxia-enhanced survival, mobility, and protection of cocultured cardiomyocytes were paralleled by increased expression of leptin and cell surface receptor CXCR4. The enhanced activities were abolished by either knockdown of leptin with a selective shRNA or by genetic deficiency of leptin or its receptor in MSCs derived, respectively, from ob/ob or db/db mice. To characterize the role of leptin in the regulation of MSC functions by hypoxia and its possible contribution to enhanced therapeutic efficacy, cell therapy using MSCs derived from wild-type, ob/ob, or db/db mice was implemented in mouse models of acute MI. Augmented protection by hypoxia pretreatment was only seen with MSCs from wild-type mice. Parameters that were differentially affected by hypoxia pretreatment included MSC engraftment, c-Kit(+) cell recruitment to the infarct, vascular density, infarct size, and long-term contractile function. These data show that leptin signaling is an early and essential step for the enhanced survival, chemotaxis, and therapeutic properties of MSCs conferred by preculture under hypoxia. Leptin may play a physiological role in priming MSCs resident in the bone marrow endosteum for optimal response to systemic signaling molecules and subsequent tissue repair.

SIRT1 ameliorates age-related senescence of mesenchymal stem cells via modulating telomere shelterin.

Mesenchymal stem cells (MSCs) senescence is an age-related process that impairs the capacity for tissue repair and compromises the clinical use of autologous MSCs for tissue regeneration. Here, we describe the effects of SIRT1, a NAD(+)-dependent deacetylase, on age-related MSCs senescence. Knockdown of SIRT1 in young MSCs induced cellular senescence and inhibited cell proliferation whereas overexpression of SIRT1 in aged MSCs reversed the senescence phenotype and stimulated cell proliferation. These results suggest that SIRT1 plays a key role in modulating age-induced MSCs senescence. Aging-related proteins, P16 and P21 may be downstream effectors of the SIRT1-mediated anti-aging effects. SIRT1 protected MSCs from age-related DNA damage, induced telomerase reverse transcriptase (TERT) expression and enhanced telomerase activity but did not affect telomere length. SIRT1 positively regulated the expression of tripeptidyl peptidase 1 (TPP1), a component of the shelterin pathway that protects chromosome ends from DNA damage. Together, the results demonstrate that SIRT1 quenches age-related MSCs senescence by mechanisms that include enhanced TPP1 expression, increased telomerase activity and reduced DNA damage.

Stem cell-based therapies for atherosclerosis: perspectives and ongoing controversies.

Atherosclerosis is a major contributor to life-threatening cardiovascular events, the leading cause of death worldwide. Since the mechanisms of atherosclerosis have not been fully understood, currently, there are no effective approaches to regressing atherosclerosis. Therefore, there is a dire need to explore the mechanisms and potential therapeutic strategies to prevent or reverse the progression of atherosclerosis. In recent years, stem cell-based therapies have held promises to various diseases, including atherosclerosis. Unfortunately, the efficacy of stem cell-based therapies for atherosclerosis as reported in the literature has been inconsistent or even conflicting. In this review, we summarize the current literature of stem cell-based therapies for atherosclerosis and discuss possible mechanisms and future directions of these potential therapies.

Stability of tibial defect reconstruction with fibular graft and unilateral external fixation: a finite element study.

Tibial defect is generally caused by high-energy injury, tumor, osteomyelitis, development deformity and bone non-union after internal fixation. This study was to determine stability of tibial defect reconstruction with fibular graft (FG) of different lengths by single free vascularized fibular graft (SFVFG) and double-barrel free vascularized fibular graft (DBFVFG). The left lower extremity of a male volunteer was scanned with computer tomography scanner. The contours of the tibia and fibula were extracted and the geometry of both bones rebuilt. From this intact model, the models of tibial defect reconstruction with fibular graft and external fixation were developed. Inter-fragmentary motion (IFM) and Von Mises stress on the fibular bone flap, and the locations of maximum Von Mises stress were introduced to quantify the biomechanical environment. Under the condition of the same graft length, the Von Mises stress value in DBFVFG group was 1.37 to 1.77 times higher than that in SFVFG group. When the length of graft was greater than 15 cm in the SFVFG group, the IFM exceeded 1 mm, but the IFM of the graft in the DBFVFG group was always less than 1 mm. The maximum Von Mises stress of models was frequently located at the second or third pin-bone interface. Thus, external fixation can provide a stable biomechanical environment for the reconstruction of tibial defect by both SFVFG and DBFVFG. The second or third pin-bone interface requires intensive care and that in the reconstruction of tibial defect by SFVFG, the graft length should not exceed 15 cm.