人脐带源间充质干细胞静脉移植治疗大鼠肝纤维化

背景：近来国内外研究证明,来自其他组织的干细胞能够归巢到肝脏,并可能参与肝组织的再生,这为发展干细胞治疗肝脏疾病提供了新的希望。 目的：探究人脐带源间充质干细胞的分离、培养方法,观察脐带间充质干细胞移植对大鼠肝纤维化模型的修复作用,为脐带间充质干细胞的临床应用提供可靠的理论依据。 方法：自然贴壁法分离、纯化人脐带间充质干细胞并进行体外培养和扩增,用皮下多点注射CCl₄制备肝纤维化大鼠模型。将22只模型大鼠随机分为模型损伤组(n=11)和细胞移植组(n=11)。细胞移植组在模型制备成功后的第1,2,3周经尾静脉给予1×10⁶脐带间充质干细胞治疗,4周后将大鼠处死,收集各组大鼠血液检测肝功能;摘取肝脏行苏木精-伊红染色,观察病理变化;免疫组化法观察库普弗细胞的数量及分布;免疫组化法观察治疗组脐带间充质干细胞的定位情况。 结果与结论：脐带间充质干细胞经尾静脉移植入肝硬化大鼠后,大鼠的肝功能均明显改善,与对照组比较,差异有显著性意义(P < 0.05);肝组织苏木精-伊红染色提示,肝纤维化程度明显改善;免疫组化法观察库普弗细胞的数量提示,库普弗细胞数量明显减少;免疫组化方法利用抗BrdU抗体在治疗组大鼠肝脏观察到BrdU标记的脐带间充质干细胞。说明脐带间充质干细胞移植可以改善大鼠外周血液的血生化特性和肝的组织学结构。中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程全文链接：     

人脐带间充质干细胞移植治疗大鼠急性肺损伤

背景：间充质干细胞具有免疫调节特性,脐带间充质干细胞因其特有的优势,将在急性肺损伤和急性呼吸窘迫综合征的临床应用中有着光明的前景。 目的：探讨脐带间充质干细胞移植对内毒素性大鼠急性肺损伤模型的保护作用。 方法：将48只健康雄性SD大鼠随机均分为正常对照组、急性肺损伤组和脐带间充质干细胞移植组。后两组采用经气管内滴注内毒素建立急性肺损伤模型。成功造模1 h后,脐带间充质干细胞移植组,经气管内滴注脐带间充质干细胞混悬液,正常对照组和急性肺损伤组同法予以等量生理盐水。分别在干预后24,72 h,观察肺组织病理改变,检测病理组织评分、肺组织干湿质量比、髓过氧化物酶活性及血浆白细胞介素6、白细胞介素10及肿瘤坏死因子α水平。 结果与结论：脐带间充质干细胞移植可以减轻内毒素诱导的急性肺损伤模型的损伤程度;脐带间充质干细胞移植组在各时间点与急性肺损伤组比较,病理损伤评分、肺干湿质量比、肺组织髓过氧化物酶活性、血浆白细胞介素6和肿瘤坏死因子α水平均明显降低,血浆白细胞介素10水平明显升高。说明脐带间充质干细胞对内毒素性急性肺损伤模型有保护作用;其保护机制可能为脐带间充质干细胞移植维持肺内炎性递质和抗炎递质平衡。     

移植保存液中脐带间充质干细胞活性与氧化应激的影响

背景：目前临床移植常用的保存液可使人脐带来源间充质干细胞活性下降,影响移植效果,但关于其活性下降原因的报道目前还很少。 目的：探索氧化应激是否为人脐带来源间充质干细胞临床移植保存过程中活性下降的因素;并在保存液中添加自由基清除剂是否可提高保存效果。 方法：室温下用生理盐水保存人脐带来源间充质干细胞,0,2,4,6 h后分别检测细胞内活性氧水平、检测丙二醛含量以及抗氧化酶活性以判定保存后细胞内氧化应激水平;保存液中添加自由基清除剂N-乙酰半胱氨酸后检测细胞贴壁率变化。 结果与结论：经生理盐水保存后人脐带来源间充质干细胞内活性氧水平升高,细胞裂解液丙二醛含量呈时间依赖性增加,抗氧化酶超氧化物歧化酶、过氧化氢酶以及谷胱甘肽过氧化物酶活性均降低。添加N-乙酰半胱氨酸的移植保存液组比不添加组保存人脐带来源间充质干细胞后细胞活性氧水平降低、贴壁率升高。说明在临床常用移植保存液中人脐带来源间充质干细胞内活性氧升高是其活性下降的一个因素,在保存液中添加自由基清除剂N-乙酰半胱氨酸后能够一定程度的改善保存效果。     

Effects of Constant Static Pressure on the Biological Properties of Porcine Aortic Valve Leaflets

An understanding of how mechanical forces impact cells within valve leaflets would greatly benefit the development of a tissue-engineered heart valve. In this study, the effect of constant ambient pressure on the biological properties of heart valve leaflets was evaluated using a custom-designed pressure system. Native porcine aortic valve leaflets were exposed to static pressures of 100, 140, or 170 mmHg for 48 h. Collagen synthesis, DNA synthesis, sulfated glycoaminoglycan (sGAG) synthesis, alpha-SMC actin expression, and extracellular matrix (ECM) structure were examined. Results showed that elevated pressure caused an increase in collagen synthesis. This increase was not statistically significant at 100 mmHg, but at 140 mmHg and 170 mmHg collagen synthesis increased by 37.5 and 90%, respectively. No significant difference in DNA or sGAG synthesis was observed at elevated pressures, with the exception that DNA synthesis at 100 mmHg decreased. A notable decline in alpha-SMC actin was observed over the course of the experiments although no significant difference was observed between the pressure and control groups. It was concluded that elevated pressure caused a proportional increase in collagen synthesis of porcine aortic valve leaflets, but was unable to preserve alpha-SMC actin immunoreactive cells.     

Tissue-engineered heart valve leaflets: an effective method of obtaining acellularized valve xenografts

To determine the most effective method of producing the acellularized xenograft heart valve leaflets, we compared pathological findings of the xenograft heart valve leaflets produced by three methods; freeze-thawing, Triton and NaCl-SDS treatment and further analyzed the pattern of endothelial cells seeded onto them. Materials and methods: Two pigs were sacrificed and three pulmonary valve leaflets were harvested from each animal. They were immediately stored in a tissue preservation solution and assigned in one of the three preparation methods for acellularization. Endothelial cells from the jugular vein of a goat were isolated and seeded onto the acellularized xenograft heart valve leaflets. Light and Electron microscopic analyses were performed. Result and conclusion: H & E stain showed that cells were almost absent in the leaflet treated with NaCl-SDS, while cells were partly present in the leaflets treated, one with Triton and the other Freeze-thawing. Transmission microscopic analyses showed cell-free matrix with well preserved collagen architecture under the seeded endothelial cells in the leaflets treated with NaCl-SDS. In conclusion, the valve leaflets treated with NaCl-SDS among three representative methods of acellularization of tissues (freeze-thawing, Triton X-100, and NaCl-SDS) showed the better results than the others in terms of the efficacy of decellularization and response to endothelial cell seeding.     

Tissue-engineered heart valve leaflets: an animal study.

BACKGROUND: Tissue-engineered heart valve leaflets are a promising way to overcome the inherent limitations of current prosthetic valves. The aim of this study was to compare the biological responses of an autologous cell seeded scaffold and an acellular scaffold implanted in the pulmonary valve leaflet in the same animal. METHODS: Myofibroblasts and endothelial cells were isolated and cultured from an ovine artery. A synthetic biodegradable scaffold consisting of polyglycolic acid and polylactic acid was initially seeded with the myofibroblasts, then coated with endothelial cells. Cells were seeded using a medium containing collagen and cultured. A tissue-engineered construct and a plain scaffold were implanted as double pulmonary valve leaflet replacement in the same animal in an ovine model (n=3). Additionally, the tissue-engineered construct (n=2) and the plain scaffold (n=2) were implanted as single valve leaflet replacements for long-term analysis. After sacrifice, the implanted valve leaflet tissues were retrieved, analyzed visually and using light microscopy. RESULTS: Three animals that underwent replacement of two valve leaflets with a tissue-engineered construct and a plain scaffold, survived only a short-time (12, 24, 36 hours). The death was attributed to heart failure caused by severe pulmonary insufficiency. Animals that underwent single valve leaflet replacement survived longer and were electively sacrificed at 6 and 9 weeks after operation. The analysis of the leaflets from the short-term survivors showed that the tissue-engineered constructs contained less fibrins and protein exudates than the plain scaffold. In contrast, leaflets obtained from animals surviving 6 and 9 weeks showed similar well organized granulation tissues in the tissue-engineered constructs and the plain scaffolds. CONCLUSION: This animal experiment demonstrates that in the early phase of implantation, the tissue-engineered construct shows a better biological response in terms of antithrombogenicity than the plain scaffold, although both of them have similar results in the later reparative phase.     

High-Resolution Fluid–Structure Interaction Simulations of Flow Through a Bi-Leaflet Mechanical Heart Valve in an Anatomic Aorta

We have performed high-resolution fluid–structure interaction simulations of physiologic pulsatile flow through a bi-leaflet mechanical heart valve (BMHV) in an anatomically realistic aorta. The results are compared with numerical simulations of the flow through an identical BMHV implanted in a straight aorta. The comparisons show that although some of the salient features of the flow remain the same, the aorta geometry can have a major effect on both the flow patterns and the motion of the valve leaflets. For the studied configuration, for instance, the BMHV leaflets in the anatomic aorta open much faster and undergo a greater rebound during closing than the same valve in the straight axisymmetric aorta. Even though the characteristic triple-jet structure does emerge downstream of the leaflets for both cases, for the anatomic case the leaflet jets spread laterally and diffuse much faster than in the straight aorta due to the aortic curvature and complex shape of the anatomic sinus. Consequently the leaflet shear layers in the anatomic case remain laminar and organized for a larger portion of the accelerating phase as compared to the shear layers in the straight aorta, which begin to undergo laminar instabilities well before peak systole is reached. For both cases, however, the flow undergoes a very similar explosive transition to the small-scale, turbulent-like state just prior to reaching peak systole. The local maximum shear stress is used as a metric to characterize the mechanical environment experienced by blood cells. Pockets of high local maximum shear are found to be significantly more widespread in the anatomic aorta than in the straight aorta throughout the cardiac cycle. Pockets of high local maximum shear were located near the leaflets and in the aortic arc region. This work clearly demonstrates the importance of the aortic geometry on the flow phenomena in a BMHV and demonstrates the potential of our computational method to carry out image-based patient-specific simulations for clinically relevant studies of heart valve hemodynamics.     

脐带间充质干细胞培养中的染色标记及示踪技术

背景：脐带间充质干细胞的培养是进行脐带间充质干细胞研究时极其重要的部分,细胞培养技术的优化对推动间充质干细胞的临床应用特别是细胞治疗至关重要。同时,脐带间充质干细胞标记及示踪技术是干细胞移植治疗的研究热点之一。目的：对国内外脐带间充质干细胞染色标记技术的研究与进展作一综述。方法：以“干细胞,间充质干细胞,脐带间充质干细胞,细胞培养,染色标记”为中文捡索词,以“Umbilical cord-derived mesenchymalstem cells,Cell culture,Labeling methods”为英文检索词,检索维普和中国知网(CNKI)期刊全文数据库、Medline,highwire和外文生物医学期刊全文数据库(Foreign Journals Integration System)2001年1月至2013年10月有关脐带间充质干细胞的培养及标记染色文献。最终纳入35篇文献进行综述。结果与结论：脐带间充质干细胞尚未得到广泛应用,最关键的原因是脐带间充质干细胞的分离培养及染色技术不是很成熟,这些方面都值得在研究中进一步优化。虽然近几年脐带间充质干细胞标记及示踪技术有了较快的进展,但仍存在许多问题有待进一步解决。中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程全文链接：     

脐带间充质干细胞对裸鼠胸腺发育的作用及机制

背景：自身免疫性疾病的传统治疗方法很难有效解决患者免疫耐受机制缺失的问题。间充质干细胞具有再生修复实质组织器官和免疫调节的生物学特性。 目的：探讨人脐带源间充质干细胞对裸鼠胸腺发育的影响及作用机制。 方法：采用腹腔注射的方式向Foxn1-/-的BABL/c裸鼠体内注射人脐带源间充质干细胞,2×106/只,分析治疗后裸鼠胸腺残基的组织结构变化、胸腺上皮细胞的分布及成熟度,以及发育后的胸腺成熟淋巴细胞输出功能,并探讨人脐带源间充质干细胞发挥治疗作用的机制。 结果与结论：胸腺残基出现了清晰的皮髓质结构,胸腺上皮细胞数量增加并且胸腺输出功能增强,外周血中调节性T细胞增多。其作用机制可能是由于人脐带源间充质干细胞能够定植在胸腺组织内并且表达多种促进胸腺发育的细胞因子,尤其是对胸腺发育非常重要的角质形成细胞生长因子。结果表明人脐带源间充质干细胞能够为裸鼠胸腺的结构发育和功能成熟提供合适的微环境,促进裸鼠胸腺残基的发育和功能成熟,为间充质干细胞治疗免疫性疾病的作用机制提出了新的理论观点。中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程全文链接：     

The in vitro development of autologous fibrin-based tissue-engineered heart valves through optimised dynamic conditioning

Our group has previously demonstrated the synthesis of a completely autologous fibrin-based heart valve structure using the principles of tissue engineering. The present approach aims to guide more mature tissue development in fibrin-based valves based on in vitro conditioning in a custom-designed bioreactor system. Moulded fibrin-based tissue-engineered heart valves seeded with ovine carotid artery-derived cells were subjected to 12 days of mechanical conditioning in a bioreactor system. The bioreactor pulse rate was increased from 5 to 10 b.p.m. after 6 days, while a pressure difference of 20 mmH(2)O was maintained over the valve leaflets. Control valves were cultured under stirred conditions in a beaker. Cell phenotype and extracellular matrix (ECM) composition were analysed in all samples and compared to native ovine aortic valve tissue using routine histological and immunohistochemical techniques. Conditioned valve leaflets showed reduced tissue shrinkage compared to stirred controls. Limited ECM synthesis was evident in stirred controls, while the majority of cells were detached from the fibrin scaffold. Dynamic conditioning increased cell attachment/alignment and expression of alpha-smooth muscle actin, while enhancing the deposition of ECM proteins, including types I and III collagen, fibronectin, laminin and chondroitin sulphate. There was no evidence for elastin synthesis in either stirred controls or conditioned samples. The present study demonstrates that the application of low-pressure conditions and increasing pulsatile flow not only enhances seeded cell attachment and alignment within fibrin-based heart valves, but dramatically changes the manner in which these cells generate ECM proteins and remodel the valve matrix. Optimised dynamic conditioning, therefore, might accelerate the maturation of surgically feasible and implantable autologous fibrin-based tissue-engineered heart valves.     

不同月龄人脐带间充质干细胞移植梗死心肌的血运重建

背景：干细胞移植有利于心肌梗死后的心肌血运重建及改善心功能,HLA-G分子在免疫耐受状态的形成及维持中具有重要作用。 目的：观察不同月龄有HLA-G表达差异的人脐带间充质干细胞移植后对急性心肌梗死兔血运重建的影响。 方法：健康新西兰大白兔30只,随机数字表法分为小月龄细胞移植组、足月龄细胞移植组及对照组。建立兔心肌梗死模型后2周,将小月龄人脐带间充质干细胞和足月人脐带间充质干细胞分别标记BrdU,多点注射心肌梗死的交界区和中心区,对照组注射无血清培养基。 结果与结论：移植后4周,小月龄和足月龄细胞移植组在心肌梗死区均发现有BrdU示踪细胞,且两组梗死区心肌纤维化程度、心肌梗死面积均少于对照组(P < 0.01),两移植组间差异也有显著性意义(P < 0.05)。Ⅷ因子染色见小月龄细胞移植组毛细血管密度高于足月龄细胞移植组(P < 0.01),且两移植组与对照组比较差异也有显著性意义(P < 0.05)。提示HLA-G表达量较高的小月龄脐带间充质干细胞能更好促进梗死区血管新生,改善血运重建,有潜力成为心肌细胞移植的更理想来源。中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程全文链接：     

Effects of molecular weight of dextran on the adherence of Streptococcus sanguis to damaged heart valves.

Dextran-producing streptococci such as Streptococcus sanguis are the organisms most frequently associated with infective endocarditis in humans. A series of experiments was designed to study how the molecular weight of dextrans affects the adherence of an endocarditis strain of S. sanguis to canine heart valves covered with platelets and fibrin. The data indicated that this adherence was dependent on dextrans of high molecular weight, such as dextran T-2000 or glucans isolated from S. sanguis or S. mutans. The adherence properties of the strain studied were not modified by prior exposure of the bacterial cells of valve leaflets to high-molecular-weight dextrans. Preexposure of bacterial cells or valve leaflets to low-molecular-weight dextrans decreased their adherence. Low-molecular-weight dextrans interfered with adherence of dextran-positive strains to damaged heart valves.     

纳米羟基磷灰石薄膜与人脐静脉血管内皮细胞的增殖

背景：合肥大学材料系和中国科学院安徽光学密精机械研究所联合研究应用脉冲激光沉积合成技术制备出一种新型的纳米羟基磷灰石人工心脏机械瓣膜。 目的：观察纳米羟基磷灰石人工心脏机械瓣膜与人脐静脉血管内皮细胞的相容性。 方法：将体外分离培养的传2-4代人脐静脉血管内皮细胞悬液接种于纳米羟基磷灰石人工心脏机械瓣膜上,培养3,7,21 d后,扫描电子显微镜下观察细胞在纳米羟基磷灰石人工心脏机械瓣膜上的生长情况。分别采用纳米羟基磷灰石人工心脏机械瓣膜常温浸提液、纳米羟基磷灰石人工心脏机械瓣膜高温浸提液、高密度聚乙烯浸提液及苯酚溶液培养人脐静脉血管内皮细胞,72 h后采用MTT法检测细胞增殖情况。 结果与结论：扫描电镜观察培养3 d时,人脐静脉血管内皮细胞呈梭形或多边形,伸出突起黏附于纳米羟基磷灰石人工心脏机械瓣膜上;7 d时,可见瓣膜表面细胞伸展充分,连接融合;21 d时,细胞成片融合,牢固覆盖于瓣膜表面,部分区域形成细胞外基质。MTT检测结果显示,纳米羟基磷灰石人工心脏机械瓣膜对人脐静脉血管内皮细胞无细胞毒性,具有良好的细胞相容性。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

脐带源间充质干细胞移植治疗肝纤维化及肝硬化的相关机制

背景：肝硬化是多种原因引起的肝脏慢性病变,目前尚没有有效的治疗方法,很多研究表明,间充质干细胞对肝纤维化及肝硬化有一定的治疗作用。 目的：研究人脐带源间充质干细胞移植对大鼠肝纤维化及肝硬化的治疗作用及其作用机制。 方法：应用CCl4诱导制备肝纤维化及肝硬化模型,造模后经尾静脉注射人脐带间充质干细胞。细胞移植后采用Beckman Coulter analyzer检测人脐带源间充质干细胞移植对大鼠肝功能的影响;采用天狼猩红染色检测肝组织病理改变;应用免疫组织化学染色、Western blot和real-time Q-PCR方法检测Ⅰ、Ⅲ型胶原、基质金属蛋白酶2、基质金属蛋白酶抑制剂2蛋白与mRNA在大鼠肝组织中的表达。 结果与结论：人脐带源间充质干细胞移植可以改善肝纤维化及肝硬化大鼠的肝功能。人脐带源间充质干细胞移植后,除肝纤维化细胞移植1周组与对应模型组相比差异无显著性意义外,其余各细胞移植组肝脏组织中基质金属蛋白酶2 mRNA及蛋白表达水平明显升高,而Ⅰ、Ⅲ型胶原、基质金属蛋白酶抑制剂2表达水平明显降低。人脐带源间充质干细胞通过上调基质金属蛋白酶2表达,下调基质金属蛋白酶抑制剂2表达,对肝纤维化及肝硬化起到治疗作用;在致病因素持续存在的情况下,人脐带源间充质干细胞移植并不能逆转肝纤维化或者肝硬化,只能延缓肝纤维化或肝硬化的进程。中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程     

Tissue-engineered acellularized valve xenografts: a comparative animal study between plain acellularized xenografts and autologous endothelial cell seeded acellularized xenografts

BACKGROUND: Acellularized valve xenografts are considered a promising way of overcoming the inherent limitations of current prosthetic valves. The aim of this study was to compare the biological responses of an autologous endothelial cell seeded acellularized xenograft (AAX) and a plain acellularized xenograft (PAX) implanted in the pulmonary valve leaflet in the same animal. METHODS: Endothelial cells were isolated and cultured from the jugular vein of goats. Porcine valve leaflets were acellularized with Nacl-SDS, and for AAX, leaflets were then seeded with autologous endothelial cells. A PAX and an AAX were implanted as double pulmonary valve leaflet replacement in the same animal in a goat model (n = 6). After sacrifice, the implanted valve leaflet tissues were retrieved and analyzed visually and under a light microscope. RESULTS AND CONCLUSIONS: Six animals were sacrificed as scheduled during the short-term (6 and 24 hours), mid-term (1 week and 1 month) and long-term (3 and 6 months). Gross and ultrasonographic examinations revealed good valve function with no thrombosis but with slight thickening. Microscopic analysis of the leaflets showed abundant cellular ingrowth into the acellularized leaflets over time. The role of endothelial cell seeding remains controversial. This animal experiment demonstrates the practical feasibility of using acellularized valve xenografts.     

脱细胞猪主动脉瓣叶的生物力学特性和免疫反应性

目的：探讨脱细胞猪主动脉瓣叶构建组织工程心脏瓣膜支架的可行性。方法：经胰酶-EDTA、表面活性剂、核酸酶处理,去除瓣叶的细胞成分,测定脱细胞瓣叶的生物力学特性,同时行大鼠皮下包埋实验,观察其免疫反应性。结果：瓣叶中的细胞成分能完全去除,获得无细胞的纤维网状支架。脱细胞瓣叶与新鲜瓣叶有基本相同的应力-应变曲线及应力-松弛曲线,而弹性模量、面积比、松弛强度、断裂强度和断裂伸长率两者无显著差异。脱细胞瓣叶的免疫反应性明显降低。结论：猪主动脉瓣叶经脱细胞处理后可以作为组织工程心脏瓣膜的支架材料。     

Observations on Durability of a Pyrolytic Carbon Bileaflet Mechanical Heart Valve

This study aims to observe the durability of a pyrolytic carbon bileaflet mechanical valve prosthesis. The mechanical valves prosthesis was tested in vitro by the durability test instrument of valve prosthesis. Then in vivo, the durability of the implanted valves was observed with animal experiments and clinical application. In the impact test for 5 min and durability test of 380 million cycles in vitro, there was no the phenomenon of flyer, perforation and fracture observed, as well as no wear or pit found on the surface of valve leaflets. The valve leaflets could normally be turned on or off. The weight of the valve was(1.0031±0.0004) g for 23 mm and(1.6003±0.0002) g for 27 mm. The hydrodynamics test demonstrated that the valve prosthesis had still excellent hemodynamic performance after the durability test. The animal autopsy showed that the valve leaflets could normally be turned on or off, and no wear was found. By follow-up of 62 patients implanted the valves, all patients had long-terms survival, no complication caused by valve was found. The age of the longest survival was more than 10 years. This study demonstrates that the new mechanical valve prosthesis have excellent durable performance.     

Numerical comparison of the closing dynamics of a new trileaflet and a bileaflet mechanical aortic heart valve

The closing velocity of the leaflets of mechanical heart valves is excessively rapid and can cause the cavitation phenomenon. Cavitation bubbles collapse and produce high pressure which then damages red blood cells and platelets. The closure mechanism of the trileaflet valve uses the vortices in the aortic sinus to help close the leaflets, which differs from that of the monoleaflet or bileaflet mechanical heart valves which mainly depends on the reverse flow. We used the commercial software program Fluent to run numerical simulations of the St. Jude Medical bileaflet valve and a new trileaflet mechanical heart valve. The results of these numerical simulations were validated with flow field experiments. The closing velocity of the trileaflet valve was clearly slower than that of the St. Jude Medical bileaflet valve, which would effectively reduce the occurrence of cavitation. The findings of this study are expected to advance the development of the trileaflet valve.     

Development and maturation of the fibrous components of the arterial roots in the mouse heart

The arterial roots are important transitional regions of the heart, connecting the intrapericardial components of the aortic and pulmonary trunks with their ventricular outlets. They house the arterial (semilunar) valves and, in the case of the aorta, are the points of coronary arterial attachment. Moreover, because of the semilunar attachments of the valve leaflets, the arterial roots span the anatomic ventriculo‐arterial junction. By virtue of this arrangement, the interleaflet triangles, despite being fibrous, are found on the ventricular aspect of the root and located within the left ventricular cavity. Malformations and diseases of the aortic root are common and serious. Despite the mouse being the animal model of choice for studying cardiac development, few studies have examined the structure of their arterial roots. As a consequence, our understanding of their formation and maturation is incomplete. We set out to clarify the anatomical and histological features of the mouse arterial roots, particularly focusing on their walls and the points of attachment of the valve leaflets. We then sought to determine the embryonic lineage relationships between these tissues, as a forerunner to understanding how they form and mature over time. Using histological stains and immunohistochemistry, we show that the walls of the mouse arterial roots show a gradual transition, with smooth muscle cells (SMC) forming the bulk of wall at the most distal points of attachments of the valve leaflets, while being entirely fibrous at their base. Although the interleaflet triangles lie within the ventricular chambers, we show that they are histologically indistinguishable from the arterial sinus walls until the end of gestation. Differences become apparent after birth, and are only completed by postnatal day 21. Using Cre‐lox‐based lineage tracing technology to label progenitor populations, we show that the SMC and fibrous tissue within the walls of the mature arterial roots share a common origin from the second heart field (SHF) and exclude trans‐differentiation of myocardium as a source for the interleaflet triangle fibrous tissues. Moreover, we show that the attachment points of the leaflets to the walls, like the leaflets themselves, are derived from the outflow cushions, having contributions from both SHF‐derived endothelial cells and neural crest cells. Our data thus show that the arterial roots in the mouse heart are similar to the features described in the human heart. They provide a framework for understanding complex lesions and diseases affecting the aortic root.     

Stem cells in the umbilical cord

Stem cells are the next frontier in medicine. Stem cells are thought to have great therapeutic and biotechnological potential. This will not only to replace damaged or dysfunctional cells, but also rescue them and/or deliver therapeutic proteins after they have been engineered to do so. Currently, ethical and scientific issues surround both embryonic and fetal stem cells and hinder their widespread implementation. In contrast, stem cells recovered postnatally from the umbilical cord, including the umbilical cord blood cells, amnion/placenta, umbilical cord vein, or umbilical cord matrix cells, are a readily available and inexpensive source of cells that are capable of forming many different cell types (i.e., they are “multipotent”). This review will focus on the umbilical cord-derived stem cells and compare those cells with adult bone marrow-derived mesenchymal stem cells.