Prognostic marker CD27 and its micro-environmental in multiple myeloma.

BACKGROUND: The Cluster of Differentiation 27 (CD27) is aberrantly expressed in multiple myeloma (MM) -derived. This expression facilitates the interaction between tumor and immune cells within TME via the CD27-CD70 pathway, resulting in immune evasion and subsequent tumor progression. The objective of this study is to investigate the correlation between CD27 expression and the prognosis of MM, and to elucidate its potential relationship with the immune microenvironment. METHODS: In this research, CD27 expression in T cells within the 82 newly diagnosed MM microenvironment was assessed via flow cytometry. We then examined the association between CD27 expression levels and patient survival. Subsequent a series of bioinformatics and in vitro experiments were conducted to reveal the role of CD27 in MM. RESULTS: Clinical evidence suggests that elevated CD27 expression in T cells within the bone marrow serves as a negative prognostic marker for MM survival. Data analysis from the GEO database has demonstrated a strong association between MM-derived CD27 and the immune response, as well as the hematopoietic system. Importantly, patients with elevated levels of CD27 expression were also found to have an increased presence of MDSCs and macrophages in the bone marrow microenvironment. Furthermore, the PERK-ATF4 signaling pathway has been implicated in mediating the effects of CD27 in MM. CONCLUSIONS: We revealed that CD27 expression levels serve as an indicative marker for the prognosis of MM patients. The CD27- PERK-ATF4 is a promising target for the treatment of MM.

Comparing perioperative outcomes following off-pump multi-vessel minimally invasive via a single left intercostal space incision with median sternotomy coronary artery bypass grafting: A single-center retrospective cohort study.

BACKGROUND: The perioperative outcomes following off-pump multi-vessel minimally invasive surgery (MICS) coronary artery bypass grafting (CABG) via a single left intercostal space incision has not been well evaluated. METHOD: From July 2019 to January 2022, a total of 444 patients with multi-vessel coronary artery disease (CAD) were enrolled and divided into MICS (n = 179) and sternotomy CABG (n = 265). Perioperative outcomes were compared between these two groups, including intraoperative blood loss, postoperative first 24 h drainage, ventilation duration, length of stay (LOS) in ICU and total LOS in hospital. Intraoperative blood flow of graft vessels were measured by transit-time flow measurement after vascular anastomosis and mean flow (MF) and pulsatile index (PI) were compared. RESULTS: There were no significant differences in preoperative profiles between these two groups except younger and lower proportion of female in MICS. No significant difference in the number of graft vessels was observed between MICS (3.18 ± 0.74) and sternotomy CABG (3.28 ± 0.86). Compared to sternotomy CABG, patients with MICS showed longer operation duration [(4.33 ± 0.86) h versus (5.10 ± 1.09) h], fewer intraoperative blood loss [700 (600, 900) mL versus 500 (200, 700) mL], fewer postoperative first 24 h drainage [400 (250, 500) mL versus 300 (200, 400) mL], shorter postoperative ventilation duration [16.5 (12.5, 19.0) h versus 15.0 (12.0, 17.0) h], LOS in ICU [20.0 (16.0, 23.0) h versus 18.0 (15.0, 20.0) h] and total LOS in hospital [(14.5 ± 3.9) d versus (12.6 ± 2.7) d] (all p < .001). MI and PI of graft vessels were similar and no significant differences in major perioperative complications and mortality were observed between MICS and sternotomy CABG (all p > .05). CONCLUSION: Off-pump multi-vessel MICS may be an alternative treatment for patients with multi-vessel CAD with better perioperative outcomes than sternotomy CABG.

A study on the perioperative effects of obesity on minimally invasive coronary artery bypass grafting and its surgical techniques.

OBJECTIVES: The aim of this study was to discuss the perioperative effects of obesity on minimally invasive coronary artery bypass grafting (CABG) and its surgical techniques. METHODS: A total of 582 patients with multivessel lesion who underwent off-pump CABG by our medical group of Beijing Anzhen Hospital between January 2017 and January 2021 were divided into the minimally invasive cardiac surgery (MICS) group and the conventional group (median sternotomy) according to the surgical method used. The body mass index of the patients was calculated, based on which both groups were divided into obese (≥28 kg/m2) and non-obese subgroups (<28 kg/m2). First, the perioperative data of the obese subgroups of both MICS and conventional groups were compared. Second, the obese and non-obese subgroups were compared in the MICS group. RESULTS: Despite a higher proportion of diabetes in the MICS group, there was no significant difference in preoperative baseline nor in the incidence of major complications within 30 days after surgery between obese subgroups of the MICS and conventional groups. The MICS group had a significantly lower rate of poor wound healing, along with a higher predischarge Barthel Index. Also, the preoperative baseline between the obese and non-obese subgroups of the MICS group exhibited no statistical differences. The obese subgroup had longer postoperative ventilator assistance, while other intraoperative data and postoperative observation indexes exhibited no significant differences. CONCLUSIONS: MICS CABG method is safe and feasible for obese patients with multivessel lesion. Minimally invasive surgery is beneficial to wound healing in obese patients. However, it requires a thorough preoperative evaluation and adequate surgical experience and skills.

Mediating effect of kinesiophobia between self-efficacy and physical activity levels in post-CABG patients: protocol for a prospective, multicentre, cross-sectional study in China.

INTRODUCTION: Physical activity (PA) can improve cardiac function, exercise capacity, and quality of life, in addition to reducing mortality by 20%-30% and preventing the recurrence of adverse cardiovascular events in patients following coronary artery bypass graft (CABG). However, PA levels are low in patients after CABG. This study intends to explore the mediating effect of kinesiophobia between self-efficacy and PA levels in patients following CABG. METHODS AND ANALYSIS: The proposed study constitutes a prospective, multicentre and cross-sectional study comprising 413 patients. Four teaching hospitals with good reputations in CABG will be included in the study. All of them are located in Beijing, China, and provide medical service to the whole country. This study will assess the following patient-reported outcome measures: demographic information, International Physical Activity Questionnaire-Long, Social Support Rating Scale, Cardiac Exercise Self-Efficacy Instrument, Multidimensional Fatigue Inventory, Hospital Anxiety and Depression Scale, and Tampa Scale for Kinesiophobia Heart. ETHICS AND DISSEMINATION: This study conforms to the principles of the Declaration of Helsinki and relevant ethical guidelines. Ethical approval has been obtained from the Ethics Committee of The Sixth Medical Centre of PLA General Hospital (approval number: HZKY-PJ-2022-2). All study participants will provide written informed consent. Findings from this study will be published in Chinese or English for widespread dissemination of the results. TRIAL REGISTRATION NUMBER: Chinese Clinical Trial Register, ChiCTR2100054098.

Comparing patient outcomes following minimally invasive coronary artery bypass grafting surgery vs. coronary artery bypass grafting: a single-center retrospective cohort study.

Background: This present research was designed for comparing coronary artery disease (CAD) patient outcomes following minimally invasive coronary artery bypass grafting surgery (MICS) or coronary artery bypass grafting (CABG). Methods: From 2014-2017, 679 CAD patients underwent MICS (n=281) or CABG (n=398) and were evaluated for the present study. Patient data were analyzed using 1:1 propensity score-matched assessment and a multivariate Cox proportional hazards regression model, and primary study achievements comprised major adverse cardiac and cerebrovascular events (MACCEs), myocardial infarction (MI), cardiac death, heart failure (HF), revascularization, and stroke. The median follow-up period was 2.68 years. Results: CABG patients exhibited a trend towards higher cumulative overall rates of MACCEs at 2 years (CABG: 6.2% vs. MICS: 3.8%) and 4 years (CABG: 9.3% vs. MICS: 7.6%) [adjusted hazard ratio (HR): 1.33; 95% confidence interval (CI): 0.33-5.39 for CABG vs. MICS; P=0.687], although this difference was not significant. No significant differences in 2- or 4-year cardiac death rates were observed between groups (CABG: 3.5%, 5.6% vs. MICS 2.8%, 2.8%; adjusted HR: 0.23; 95% CI: 0.03-1.81 for CABG vs. MICS; P=0.160). Further, there existed no discrepancies in rates of MI (P=1.000), HF (adjusted HR: 4.76; 95% CI: 0.01-6.40 for CABG vs. MICS; P=0.996), stroke (adjusted HR: 9.58; 95% CI: 0.11-25.24 for CABG vs. MICS; P=0.320), or repeated revascularization (adjusted HR: 1.71; 95% CI: 0.01-7.21 for CABG vs. MICS; P=0.631) when comparing these patient groups. In a multivariable Cox proportional hazards regression analysis, patients that were male (adjusted HR: 5.28; 95% CI: 1.48-18.83; P=0.010) and cases with a history of previous MI epsiodes (adjusted HR: 3.20; 95% CI: 1.09-9.37; P=0.034) were found to be at a higher risk of MACCEs. Conclusions: Follow-up data indicated that the MICS and CABG treatments could achieve similar outcomes.

Comparison of early outcomes associated with coronary artery bypass grafting for multi-vessel disease conducted using minimally invasive or conventional off-pump techniques: a propensity-matched study based on SYNTAX score.

BACKGROUND: This study was designed to compare early outcomes associated with coronary artery bypass grafting for multi-vessel disease conducted using either minimally invasive or conventional off-pump techniques. METHODS: From January 2017 through January 2021, 582 patients with multi-vessel lesion coronary artery disease underwent either minimally invasive cardiac surgery coronary artery bypass grafting (MICS CABG) or conventional off-pump coronary artery bypass grafting (OPCABG) treatment by our team at Anzhen Hospital. Patients in the MICS CABG group were propensity score-matched with those in the OPCABG at a 1:1 ratio (MICS CABG = 172; OPCABG = 172), using epidemiological data, preoperative clinical characteristics, and SYNTAX score as covariates. Perioperative outcomes and 6-month computed tomography angiography findings were compared between these groups. RESULTS: No significant differences between groups were observed with respect to 30-day postoperative mortality, myocardial infarction, and stroke incidence. Surgical data indicated that the MICS CABG procedure was able to cover all three main arterial territories with a relatively low need for circulatory assistance. The MICS CABG procedure was associated with a longer operative duration, but was also associated with higher postoperative hemoglobin and activities of daily living index values as well as a shorter duration of postoperative hospitalization (P < 0.05). No differences in 6-month graft patency were observed between groups. CONCLUSIONS: MICS CABG is a safe, less invasive alternative to OPCABG when performing complete revascularization provided patients are properly selected, yielding similar in-hospital outcomes and 6-month graft patency rates together with an earlier return of physical function.

Off-Pump Aortic Bypass for Hypoplastic Arch and Aortic Coarctation Via Anterolateral Thoracotomy.

We report the case of a 21-year-old woman who was referred with uncontrolled hypertension. Computed tomography angiography revealed aortic arch hypoplasia and severe aortic coarctation. An off-pump ascending-to-descending aortic bypass surgery using synthetic graft was performed via left anterolateral thoracotomy. The patient recovered well and was discharged home uneventfully after five days. This procedure was performed without touching the head vessels or any collateral vessels. We consider this a safe and less invasive alternative technique for adult coarctation patients who have aortic hypoplasia or interrupted aorta.

Surgical Challenges in Multi-Vessel Minimally Invasive Coronary Artery Bypass Grafting.

OBJECTIVES: Minimally invasive coronary artery bypass grafting (MICS CABG) has emerged as an alternative treatment for patients with multi-vessel coronary artery disease, but there are certain surgical challenges inherent in the adoption of this approach. The present study was conducted to provide insight regarding the outcomes associated with our first 118 cases, to discuss the surgical difficulties encountered in these patients, and to outline the potential countermeasures. METHODS: Between January 2017 and January 2020, 118 patients underwent multi-vessel MICS CABG. These patients were stratified into two groups based upon whether they did or did not experience surgical challenges, and early clinical outcomes were compared between these groups to assess the incidence of technical difficulties and associated factors. RESULTS: Surgical challenges arose in 38 of the 118 cases in this study, including 13 cases of exposure-related difficulties, 11 cases of proximal anastomosis-related difficulties, 15 cases of distal anastomosis-related difficulties, 4 cases of LITA-related difficulties, and 3 cases of lung-related difficulties. Relative to the other 80 patients, those patients for whom intraoperative technical challenges arose experience significant increases in operative duration (4.94 ± 0.89 vs. 5.59 ± 1.11 h, P=0.001), intraoperative blood loss (667 ± 313 vs. 892 ± 532 mL, P=0.005), length of the ICU admission (17.59 ± 3.51 vs. 22.59 ± 17.31 h, P=0.015), and the duration of postoperative hospitalization (5.96 ± 1.23 vs. 6.71 ± 1.92 days, P=0.012). There were no significant differences between these groups with respect to the mean graft number, major complications such as stroke or organ dysfunction, or one-year graft patency. CONCLUSIONS: There is a substantial learning curve associated with performing off-pump MICS CABG to treat multi-vessel disease. Surgical challenges encountered during this procedure may increase the operative duration, intraoperative blood loss, ICU admission, and the duration of postoperative hospitalization. However, these issues do not appear to compromise the efficacy of complete revascularization, and early clinical outcomes associated with this procedure remain acceptable.

Development of stimuli-responsive intelligent polymer micelles for the delivery of doxorubicin.

Doxorubicin is still used as a first-line drug in current therapeutics for numerous types of malignant tumours (including lymphoma, transplantable leukaemia and solid tumour). Nevertheless, to overcome the serious side effects like cardiotoxicity and myelosuppression caused by effective doses of doxorubicin remains as a world-class puzzle. In recent years, the usage of biocompatible polymeric nanomaterials to form an intelligently sensitive carrier for the targeted release in tumour microenvironment has attracted wide attention. These different intelligent polymeric micelles (PMs) could change the pharmacokinetics process of drugs or respond in the special microenvironment of tumour site to maximise the efficacy and reduce the toxicity of doxorubicin in other tissues and organs. Several intelligent PMs have already been in the clinical research stage and planned for market. Therefore, related research remains active, and the latest nanotechnology approaches for doxorubicin delivery are always in the spotlight. Centring on the model drugs doxorubicin, this review summarised the mechanisms of PMs, classified the polymers used in the application of doxorubicin delivery and discussed some interesting and imaginative smart PMs in recent years.

Minicircle HBV cccDNA with a Gaussia luciferase reporter for investigating HBV cccDNA biology and developing cccDNA-targeting drugs.

Chronic Hepatitis B Virus (HBV) infection is generally not curable with current anti-viral drugs. Virus rebounds after stopping treatment from the stable HBV covalently-closed-circular DNA (cccDNA). The development of drugs that directly target cccDNA is hampered by the lack of robust HBV cccDNA models. We report here a novel HBV cccDNA technology that will meet the need. We engineered a minicircle HBV cccDNA with a Gaussia Luciferase reporter (mcHBV-GLuc cccDNA), which serves as a surrogate to measure cccDNA activity. The mcHBV-GLuc cccDNA was easily produced in bacteria, and it formed minichromosomes as HBV cccDNA episome DNA does when it was transfected into human hepatocytes. Compared to non-HBV minicircle plasmids, mcHBV-GLuc cccDNA showed persistent HBV-GLuc activity and HBx-dependent gene expression. Importantly, the mcHBV-GLuc cccDNA showed resistance to interferons (IFN) treatment, indicating its unique similarity to HBV cccDNA that is usually resistant to long-term IFN treatment in chronic HBV patients. Most importantly, GLuc illuminates cccDNA as a surrogate of cccDNA activity, providing a very sensitive and quick method to detect trace amount of cccDNA. The mcHBV-GLuc cccDNA model is independent of HBV infection, and will be valuable for investigating HBV cccDNA biology and for developing cccDNA-targeting drugs.

PAK4 confers the malignance of cervical cancers and contributes to the cisplatin-resistance in cervical cancer cells via PI3K/AKT pathway.

BACKGROUND: Multiple protein or microRNA markers have been recognized to contribute to the progression and recurrence of cervical cancers. Particular those, which are associated with the chemo- or radio-resistance of cervical cancers, have been proposed to be promising and to facilitate the definition for cervical cancer treatment options. METHODS: This study was designed to explore the potential prognosis value of p21-activated kinase (PAK)-4 in cervical cancer, via the Kaplan-Meier analysis, log-rank test and Cox regression analysis, and then to investigate the regulatory role of PAK4 in the cisplatin resistance in cervical cancer cells, via the strategies of both PAK4 overexpression and PAK4 knockout. RESULTS: It was demonstrated that PAK4 was upregulated in cervical cancer tissues, in an association with the cancer's malignance variables such as FIGO stage, lymph node or distant metastasis and the poor histological grade. The high PAK4 expression was also independently associated with poor prognosis to cervical cancer patients. Moreover, PAK4 confers cisplatin resistance in cervical cancer Hela or Caski cells. In addition, the PI3K/Akt pathway has been implicated in the PAK4-confered cisplatin resistance. And the PI3K/Akt inhibitor, LY294002, markedly deteriorated the cisplatin-mediated viability reduction of Hela or Caski cells, indicating the involvement of PI3K/Akt pathway in the cisplatin resistance in cervical cancer cells. CONCLUSION: This study has confirmed the significant prognostic role of PAK4 level in cervical cancer patients and has recognized the regulatory role in cervical cancer progression. Moreover, our study has indicated that PAK4 also confers the chemoresistance of cervical cancer cells in a PI3K/Akt-dependent way. Thus, our study indicates PAK4 as a promising marker for cervical cancer treatment.

Early results of coronary endarterectomy combined with coronary artery bypass grafting in patients with diffused coronary artery disease.

BACKGROUND: It is still a challenge for the cardiac surgeons to achieve adequate revascularization for diffused coronary artery disease (CAD). Coronary endarterectomy (CE) offers an alternative choice of coronary artery reconstruction and revascularization. In this study, short-term result of CE combined with coronary artery bypass graft (CABG) was discussed in the treatment for the diffused CAD. METHODS: From January 2012 to April 2014, 221 cases of CABG were performed by the same surgeon in our unit. Among these cases, 38 cases of CE + CABG were performed, which was about 17.2% (38/221) of the cohort. All these patients were divided into two groups: CE + CABG group (Group A) and CABG alone group (Group B). All clinical data were compared between the two groups, and postoperative complications and in-hospital mortality were analyzed. The categorical and continuous variables were analyzed by Chi-square test and Student's t-test respectively. RESULTS: Diabetes mellitus, hypertension, hyperlipidemia, and peripheral vascular disease were more common in group A. In this cohort, a total of 50 vessels were endarterectomized. Among them, CE was performed on left anterior descending artery in 11 cases, on right coronary artery in 29 cases, on diagonal artery in 3 cases, on intermediate artery in 2 cases, on obtuse marginal artery in 5 cases. There was no hospital mortality in both groups. The intro-aortic balloon pump was required in 3 cases in Group A (3/38), which was more often than that in Group B (3/183). At the time of follow-up, coronary computed tomography angiogram showed all the grafts with CE were patent (50/50). There is no cardio-related mortality in both groups. All these patients were free from coronary re-intervention. CONCLUSIONS: Coronary endarterectomy + CABG can offer satisfactory result for patients with diffused CAD in a short-term after the operation.

Hepatitis B virus infection and immunopathogenesis in a humanized mouse model: induction of human-specific liver fibrosis and M2-like macrophages.

The mechanisms of chronic HBV infection and immunopathogenesis are poorly understood due to a lack of a robust small animal model. Here we report the development of a humanized mouse model with both human immune system and human liver cells by reconstituting the immunodeficient A2/NSG (NOD.Cg-Prkdc(scid) Il2rg(tm1Wjl)/SzJ mice with human HLA-A2 transgene) with human hematopoietic stem cells and liver progenitor cells (A2/NSG-hu HSC/Hep mice). The A2/NSG-hu HSC/Hep mouse supported HBV infection and approximately 75% of HBV infected mice established persistent infection for at least 4 months. We detected human immune responses, albeit impaired in the liver, chronic liver inflammation and liver fibrosis in infected animals. An HBV neutralizing antibody efficiently inhibited HBV infection and associated liver diseases in humanized mice. In addition, we found that the HBV mediated liver disease was associated with high level of infiltrated human macrophages with M2-like activation phenotype. Importantly, similar M2-like macrophage accumulation was confirmed in chronic hepatitis B patients with liver diseases. Furthermore, gene expression analysis showed that induction of M2-like macrophage in the liver is associated with accelerated liver fibrosis and necrosis in patients with acute HBV-induced liver failure. Lastly, we demonstrate that HBV promotes M2-like activation in both M1 and M2 macrophages in cell culture studies. Our study demonstrates that the A2/NSG-hu HSC/Hep mouse model is valuable in studying HBV infection, human immune responses and associated liver diseases. Furthermore, results from this study suggest a critical role for macrophage polarization in hepatitis B virus-induced immune impairment and liver pathology.

[Safety analysis of application of medical anti-adhesion modified chitosan in cardiac surgery].

OBJECTIVE: To verify the application safety of medical anti-adhesion modified chitosan (Baifeimi) in cardiac surgery. METHODS: From August to December 2010, 42 patients undergoing surgery for congenital heart disease, valvular heart disease or ischemic heart disease were selected and divided into testing (n = 22) and control (n = 20) groups. After complete intraoperative hemostasis, two sheets of anti-adhesion modified chitosan (Baifeimi) were placed on the surface of heart and vessels in the testing group and then chest was closed. And the control group underwent routine chest closing without an application of Baifeimi. The systemic and local reactions and drainage fluid were observed. The postoperative drainage fluid was subject to bacteria culture. Blood routines and laboratory tests at preoperation and Day 1 and Week 1 postoperation were performed to evaluate the changes of chemical, biological and immunological parameters. RESULTS: There was no occurrence of systemic reaction, local inflammation or exudation.Wounds were healed at Phase I. The drainage fluid of pericardium and mediastina had no significant intergroup difference. Drainage was unobstructed in the testing group. A comparison of two groups revealed that the differences of aspartate aminotransferase ( (24 ± 17) vs (40 ± 22) U/L), preoperative and postoperative immunoglobulin A( (1.9 ± 0.7) vs (2.9 ± 1.4) g/L, (2.3 ± 0.9) vs (3.3 ± 1.5) g/L) were statistically significant (all P < 0.05). But the average values of both group stayed within a normal range without clinical significance while other indices had no significant difference. The bacteria cultures of all patients in the control group were negative. CONCLUSIONS: Anti-adhesion modified chitosan is both convenient and safe for clinical application. The duration of cardiac surgery is not extended.No systemic or local adverse event is reported. There is no interference of hepatic, renal or immune functions.

A modified chordal transfer technique to treat anterior mitral leaflet prolapse.

Chordal transfer from the intact posterior mitral leaflet (PML) to the anterior mitral leaflet (AML) is an effective way to correct anterior leaflet prolapse and provides good long-term results. However, it is difficult to determine the accurate segment of the PML which needs to be transferred and the suture point of the leaflets. We describe a modified technique to determine the correct segment that needs to be transferred to effectively correct AMLs with elongated or ruptured chordae. This technique renders performing chordal transfer easier and more accurate.

Edge-to-edge chordal transfer repair for anterior leaflet prolapse of mitral valve in 21 patients.

BACKGROUND: Repair of anterior mitral leaflet (AML) prolapse is still a technical challenge for cardiac surgeons. It is an important issue to find a way to repair the AML prolapse with a reliable and reproducible technique. METHODS: Between January 2002 and June 2009, the operation of chordal transfer based on the "edge-to-edge" technique was performed in 21 patients with serious mitral valve regurgitation because of prolapse of the anterior leaflet. After the operation, echocardiography was performed in each patient before discharge and at the time of follow-up. RESULTS: All patients survived the operation. One patient required mitral valve replacement because of anterior leaflet perforation 3 days after the operation. The other patients were free from reoperation. At the time of follow-up, all these patients were in New York Heart Association (NYHA) functional class I. In all these patients, pre-discharge and follow-up echocardiography showed neither stenosis nor significant regurgitation of the mitral valve: the cross-sectional area of the mitral valve was 3.3 - 4.8 cm(2) (mean (3.78 ± 0.52) cm(2)), the mean regurgitation area was (0.45 ± 0.22) cm(2). At the same time, both dimension of left atrium and left ventricle reduced significantly (left atrium diameter: pre-operation (48.26 ± 11.12) mm, post-operation (37.57 ± 9.56) mm, P < 0.05; the end-diastolic diameter of the left ventricle: pre-operation (61.43 ± 8.24) mm, post-operation (42.35 ± 10.79) mm, P < 0.01). CONCLUSION: "Edge-to-edge" chordal transfer technique is a simple, reliable, and reproducible technique that can provide good results for repair of anterior leaflet prolapse of mitral valve.

Modulation of collagen gel compaction by extracellular ATP is MAPK and NF-kappaB pathways dependent.

Understanding the mechanisms that regulate mechanosensitivity in osteoblasts is important for controlling bone homeostasis and the development of new drugs to combat bone loss. It is believed that prestress or force generation (the tensile stress within the cell body) plays an important role in regulating cellular mechanosensitivity. In the present study, a three-dimensional (3D) collagen culture was used to monitor the change in prestress of the osteoblast-like cells. Collagen hydrogel compaction has been used as an indicator of the change in the degree of cell prestress. Previous results in this model demonstrated that extracellular ATP reduced the mechanosensitivity of osteoblasts by reducing cellular prestress. To elucidate the potential mechanisms involved in this process, the signaling pathways downstream of P2 purinoceptors involved in regulating the compaction of type I collagen gels were investigated. By using specific inhibitors to these signaling pathways, we found that ATP-induced reduction in collagen gel compaction rate is dependent on mitogen-activated protein kinase (MAKP) and NF-kappaB pathways. However, blocking protein kinase C with GF109203X did not change the compaction kinetics in the presence of ATPgammaS. Moreover, blocking cyclic AMP (cAMP), phosphatidylinositol-3 kinase (PI3K), calmodulin (CaM) or L-type voltage sensitive calcium channels did not affect ATP's ability to reduce collagen gel compaction. The results from the present and previous studies indicate that extracellular ATP may act as a negative feedback modulator in the mechanotransduction system since mechanical stimuli increase ATP release from stimulated cells.

ATP reduces gel compaction in osteoblast-populated collagen gels.

Bone remodeling is a localized process, but regulated by systemic signals such as hormones, cytokines, and mechanical loading. The mechanism by which bone cells convert these systemic signals into local signals is not completely understood. It is broadly accepted that the "prestress" in cytoskeleton of cells affects the magnitude of cellular responses to mechanical stimuli. Prestress derives from stiff cytoskeletal proteins and their connections within the cell and from cell contractility upon attaching to matrix. In an in vitro model of three-dimensional gel compaction, the relative cellular prestress levels in the same matrix environment were determined by matrix compaction rate: a greater compaction rate resulted in a higher level of prestress. In the present study, the effects of ATP on the prestress of osteoblasts were studied using mouse MC3T3-E1 cells grown in three-dimensional bioartificial tissues (BATs). ATP (> or =100 microM) reduced the compaction rate of BATs in a dose-dependent manner. ADP, 2'-(or 3')-O-(4-benzoylbenzoyl) ATP, and UTP, but not alpha,beta-methylene ATP, also reduced the compaction rate but to a lesser extent. Pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid tetrasodium did not block the effect of ATP on BAT compaction rate. These results indicate that both P2X and P2Y receptors are involved in ATP-induced reduction of BAT compaction rate. Steady fluid flow and RT-PCR results showed that ATP reduced cell attachment on type I collagen by downregulating the expression of integrin alpha(1). These results suggest a potential role for P2 receptors in matrix remodeling and repair and as a potential drug target in treatment of bone diseases.