Microfluidic co-culture platform for investigating osteocyte-osteoclast signalling during fluid shear stress mechanostimulation

Bone cells exist in a complex environment where they are constantly exposed to numerous dynamic biochemical and mechanical stimuli. These stimuli regulate bone cells that are involved in various bone disorders, such as osteoporosis. Knowledge of how these stimuli affect bone cells have been utilised to develop various treatments, such as pharmaceuticals, hormone therapy, and exercise. To investigate the role that bone loading has on these disorders in vitro, bone cell mechanotransduction studies are typically performed using parallel plate flow chambers (PPFC). However, these chambers do not allow for dynamic cellular interactions among different cell populations to be investigated. We present a microfluidic approach that exposes different cell populations, which are located at physiologically relevant distances within adjacent channels, to different levels of fluid shear stress, and promotes cell-cell communication between the different channels. We employed this microfluidic system to assess mechanically regulated osteocyte-osteoclast communication. Osteoclast precursors (RAW264.7 cells) responded to cytokine gradients (e.g., RANKL, OPG, PGE-2) developed by both mechanically stimulated (fOCY) and unstimulated (nOCY) osteocyte-like MLO-Y4 cells simultaneously. Specifically, we observed increased osteoclast precursor cell densities and osteoclast differentiation towards nOCY. We also used this system to show an increased mechanoresponse of osteocytes when in co-culture with osteoclasts. We envision broad applicability of the presented approach for microfluidic perfusion co-culture of multiple cell types in the presence of fluid flow stimulation, and as a tool to investigate osteocyte mechanotransduction, as well as bone metastasis extravasation. This system could also be applied to any multi-cell population cross-talk studies that are typically performed using PPFCs (e.g. endothelial cells, smooth muscle cells, and fibroblasts).     

Fluid replacement following dehydration reduces oxidative stress during recovery

To investigate the effects of hydration status on oxidative DNA damage and exercise performance, 10 subjects ran on a treadmill until exhaustion at 80% VO_2max during four different trials [control (C), 3% dehydration (D), 3% dehydration + water (W) or 3% dehydration + sports drink (S)]. Dehydration significantly decreased exercise time to exhaustion (D < C and S). Plasma MDA levels were significantly higher at pre-exercise in D than C. Plasma TAS was significantly lower at pre-exercise in C and S than in D, and was significantly lower in S than D at 60 min of recovery. Dehydration significantly increased oxidative DNA damage during exercise, but fluid replacement with water or sports drink alleviated it equally. These results suggest that (1) dehydration impairs exercise performance and increases DNA damage during exercise to exhaustion; and (2) fluid replacement prolongs exercise endurance and attenuates DNA damage.     

羊膜及羊膜匀浆液在眼科学中应用的研究进展

羊膜应用于医学已有一个多世纪,应用于眼科也有70余年的历史。因种种原因,在很长一段时间里,对羊膜的研究停滞不前,但随着生物医学技术和其它相关技术的发展,羊膜的解剖结构及生物学特性研究得越来越深入。而随着羊膜的解剖和生物学特性日益明确,羊膜在医学和组织工程学中的应用也越来越广泛,并且应用前景广阔。近年来,由于羊膜的诸多解剖和生物学特性符合眼科学发展的需要,羊膜在眼科中的应用也日益广泛,并取得了良好的临床效果。羊膜的研磨提取液-羊膜匀浆液保留了羊膜中的有效生物成分,在治疗眼部疾病方面也取得了一定的进展。国内外关于羊膜及羊膜匀浆的研究文献有很多,为了更深入了解羊膜的特性及其在眼科疾病治疗方面的优势,该文将对羊膜的应用历史、羊膜及羊膜匀浆液的制备及保存、生物学特性及其在眼科学中的应用作一综述。     

Direct numerical simulation of expiratory crackles: Relationship between airway closure dynamics and acoustic fluctuations

This paper investigates the relationship between airway closure dynamics and acoustic fluctuations in expiratory crackles using direct numerical simulation. A unified mathematical model is proposed to deal with flow in an airway, elastic deformation of the airway wall, surface tension driven motion of the liquid film that lines the airway, and their acoustic fluctuations because of material compressibility. Airway closure is induced by increasing the surrounding pressure, then the source of the pressure fluctuations is measured over time. Our results show that the airway closure occurs suddenly because of a bridge formation of the liquid film, and high energy transfer occurs between the kinetic energy, the surface energy of the liquid interface, and the elastic energy of the airway wall, invoking a large acoustic fluctuation that causes the expiratory crackles. Nonlinear behavior is observed in terms of the airway wall stiffness; the dynamic motion of the airway closure becomes moderate and both the energy transfer and acoustic fluctuations are dramatically reduced with an increase in airway wall stiffness.     

利用转录组测序筛选低切应力作用下人脐静脉内皮细胞的差异表达基因

目的:通过转录组测序分析获得不同切应力作用下人脐静脉内皮细胞的基因的表达谱,为进一步探索切应力影响内皮细胞形态和功能的机制提供依据。方法:以人脐静脉内皮细胞为材料,通过Streamer系统建立6通道可调控切应力的流体动力学细胞模型,以层流切应力(15 dynes/cm~2)为对照,以低切应力(0.1 dynes/cm~2)为实验组,分别加载细胞18 h。提取总RNA逆转录合成cDNA,建立文库,以二代测序平台Illumina HiSeq中进行扩增和测序。结果:序列比对结果显示,有19986个基因比对上,新转录本分析显示各组新转录本数约占总转录本数的50%。基因表达差异分析显示,较对照组,低切应力组表达上调基因983个,表达下调基因701个。GO分析显示,有18499个基因得到了归类注释,绝大多数基因富集到生物学过程。KEGG分析显示,富集Top20的信号通路与细胞周期、DNA复制和细胞分裂、细胞应激和凋亡等生物学过程相关。结论:低切应力作用不仅仅激活内皮细胞中细胞的增殖相关基因,同时也涉及到DNA损伤修复和凋亡相关基因。     

脑脊液分流术治疗64例脑肿瘤临床效果分析

目的:通过观察脑脊液分流术在64例脑肿瘤患者中的临床应用效果,探讨其临床应用的价值。方法:收集2009年1月-2010年3月我院64例脑肿瘤患者病例资料,其临床诊断均有颅内高压,对照组32例患者给予常规手术进行肿瘤切除;观察组在对照组的基础上给予脑脊液分流术,比较两组治疗效果。结果:治疗后两组颅内压均降低,观察组降低更为明显(P0.05)。对照组完全缓解率为15.6%,部分缓解率为21.8%,病程稳定率为31.3%,病程进展率为31.3%。观察组分别为28.1%、31.3%、25%和15.6%。观察组完全缓解率和部分缓解率明显高于对照组(P0.05.),病程进展率对照组明显高于观察组(P0.05)。对照组术后两年内复发5例,生存超过三年的17例,生存超过五年的12例。观察组术后两年内复发的2例,生存超过三年的20例,生存超过5年的15例。和对照组比较,观察组术后病情复发率更低,生存指数更高,比较有明显差异(P0.05)。结论:脑脊液分流术在伴颅内高压或脑积水的脑肿瘤手术中的使用效果显著,后期的手术成功率和患者生存率提高,临床上可予以更为深入的探索。     

Response of osteoblasts to low fluid shear stress is time dependent

The process of mechanotransduction of bone, the conversion of a mechanical stimulus into a biochemical response, is known to occur in osteoblasts in response to fluid shear stress. In order to understand the reaction of osteoblasts to various times of flow perfusion, osteoblasts were seeded on three-dimensional scaffolds, and cultured in the following conditions: continuous flow perfusion, intermittent flow perfusion, and static condition. We collected samples on day 4, 8 and 12 for analysis. Osteoblast proliferation was demonstrated by cell proliferation and scanning electron microscopy assay. Additionally, the expression of known markers of differentiation, including alkaline phosphatase and osteocalcin, were tested by qRT-PCR and alkaline phosphatase activity assay, and the deposition of calcium was used as an indicator of mineralization demonstrated by calcium content assay. The results supported that low fluid shear stress plays an important role in the activation of osteoblasts: enhance cell proliferation, increase calcium deposition, and promote the expression of osteoblastic markers. Furthermore, the continuous flow perfusion is a more favorable environment for the initiation of osteoblast activity compared with intermittent flow perfusion. Therefore, the force and time of fluid shear stress are important parameters for osteoblast activation.     

Basic concepts of fluid responsiveness

Predicting fluid responsiveness, the response of stroke volume to fluid loading, is a relatively novel concept that aims to optimise circulation, and as such organ perfusion, while avoiding futile and potentially deleterious fluid administrations in critically ill patients. Dynamic parameters have shown to be superior in predicting the response to fluid loading compared with static cardiac filling pressures. However, in routine clinical practice the conditions necessary for dynamic parameters to predict fluid responsiveness are frequently not met. Passive leg raising as a means to alter biventricular preload in combination with subsequent measurement of the change in stroke volume can provide a fast and accurate way to guide fluid management in a broad population of critically ill patients.