Bladder wall grafting in rats using salt-modified and collagen-coated polycaprolactone scaffolds: Preliminary report

AIM: A rat model was used for the evaluation of collagen-coated and salt-modified polycaprolactone (PCL) scaffolds for bladder grafting after hemicystectomy. METHODS: SD rats underwent partial cystectomy and cystoplasty with collagen-coated and salt-modified polycaprolactone scaffolds. The grafts of the regenerated bladder wall were harvested at different intervals and tissue regeneration was evaluated microscopically. Anatomic and functional characters were evaluated by cystography and urodynamics. RESULTS: At harvesting, after 1 and 2 months, we found good preservation of the bladder shape and volume in all 16 rats receiving PCL cystorrhaphy. No stone formation was observed. Good epithelialization and ingrowth of smooth muscle cells were seen after 2 months grafting. Collagen-coated PCL scaffolds showed considerable encrustation, which appeared to be absorbed and disappear with time. The cystographic and urodynamic examinations revealed intact contour and a well-accommodated bladder with reservoir volume and contractility. CONCLUSIONS: In the rat model, we have successfully demonstrated the applicability of collagen coated and salt-modified PCL in reconstruction of the partial cystectomized bladder.     

Bladder tissue engineering through nanotechnology

The field of tissue engineering has developed in phases: initially researchers searched for "inert" biomaterials to act solely as replacement structures in the body. Then, they explored biodegradable scaffolds-both naturally derived and synthetic-for the temporary support of growing tissues. Now, a third phase of tissue engineering has developed, through the subcategory of "regenerative medicine." This renewed focus toward control over tissue morphology and cell phenotype requires proportional advances in scaffold design. Discoveries in nanotechnology have driven both our understanding of cell-substrate interactions, and our ability to influence them. By operating at the size regime of proteins themselves, nanotechnology gives us the opportunity to directly speak the language of cells, through reliable, repeatable creation of nanoscale features. Understanding the synthesis of nanoscale materials, via "top-down" and "bottom-up" strategies, allows researchers to assess the capabilities and limits inherent in both techniques. Urology research as a whole, and bladder regeneration in particular, are well-positioned to benefit from such advances, since our present technology has yet to reach the end goal of functional bladder restoration. In this article, we discuss the current applications of nanoscale materials to bladder tissue engineering, and encourage researchers to explore these interdisciplinary technologies now, or risk playing catch-up in the future.     

Fetal tissue engineering: chest wall reconstruction

Background/Purpose: This study was aimed at applying fetal tissue engineering to chest wall reconstruction.Methods: Fetal lambs underwent harvest of elastic and hyaline cartilage specimens. Once expanded in vitro, fetal chondrocytes were seeded onto synthetic scaffolds, which then were placed in a bioreactor. After birth, fetal cartilage constructs (n = 10) were implanted in autologous fashion into the ribs of all lambs (n = 6) along with identical, but acellular scaffolds, as controls (n = 6). Engineered and acellular specimens were harvested for analysis at 4 to 12 weeks postimplantation. Standard histology and matrix-specific staining were performed both before implantation and after harvest on all constructs.Results: Regardless of the source of chondrocytes, all fetal constructs resembled hyaline cartilage, both grossly and histologically, in vitro. In vivo, engineered implants retained hyaline characteristics for up to 10 weeks after implantation but remodeled into fibrocartilage by 12 weeks postoperatively. Mononuclear inflammatory infiltrates surrounding residual PGA/PLLA polymer fibers were noted in all specimens but most prominently in the acellular controls.Conclusions: Engineered fetal cartilage can provide structural replacement for at least up to 10 weeks after autologous, postnatal implantation in the chest wall. Fetal tissue engineering may prove useful for the treatment of severe congenital chest wall defects at birth.     

大鼠毛囊细胞构建组织工程全层皮肤

目的:以大鼠毛囊细胞为种子细胞培养组织工程皮肤。方法:分离培养新生SD大鼠毛囊外根鞘细胞和真皮鞘细胞,以这两种细胞为种子细胞构建全层组织工程全层皮肤。结果:成功构建了具有表皮层和真皮层的组织工程皮肤。结论:毛囊细胞可以用作种子细胞来构建组织工程全层皮肤。     

半月板组织工程的研究进展

半月板损伤临床常见,据美国矫形外科学会2008年的统计资料,美国每年全膝关节置换手术＆gt;250000例,其中半月板损伤是骨性关节炎进展的关键因素。然而,半月板仅外周1/3有血液供应,发生于此部位的损伤采用缝合治疗可以愈合;而内侧缘2/3均为无血管区,损伤后自行愈合能力较差,目前临床上针对这类损伤多采用半月板部分切除或全部切除术。     

组织工程与干细胞技术在尿道重建中的应用

先天性畸形、外伤、炎症、肿瘤等导致的尿道缺损是泌尿外科常见的疾病,传统尿道重建方法存在诸多并发症,并且受供体材料有限性的限制,应用组织工程与干细胞技术构建生物替代物以维持、修复损伤组织和器官功能,为尿道修复重建开创了新的临床治疗前景,本文就其在尿道重建中的基础研究与临床应用进展作一综述。     

富含血小板血浆双相接种法构建组织工程骨

目的：传统的细胞接种法接种效率低,影响组织工程骨的成骨质量。本研究预探讨富含血小板血浆双相接种法是否可以提高细胞接种效率、优化组织工程骨的构建。方法：分别用富含血小板血浆、乏血小板血浆重悬BMSCs,灌注于三维多孔PLGA支架中,凝血酶促凝,体外培养。通过扫描电镜观察支架表面的细胞分布;通过检测支架内DNA含量、ALP含量、成骨基因表达情况分析细胞的接种效率、增殖和分化情况,并与传统的接种方法进行比较。结果：富含血小板血浆和乏血小板血浆双相接种法均能提高细胞与三维支架的结合效率;富含血小板血浆还可以促进支架内细胞的增殖,同时不影响细胞的分化。结论：双相接种法可以提高细胞的接种效率;与普通双相接种法相比,富含血小板血浆双相接种法可以进一步优化组织工程骨的构建。     

Cartilage tissue engineering by expanded goat articular chondrocytes.

In this study we investigated whether expanded goat chondrocytes have the capacity to generate cartilaginous tissues with biochemical and biomechanical properties improving with time in culture. Goat chondrocytes were expanded in monolayer with or without combinations of FGF-2, TGF-beta1, and PDGFbb, and the postexpansion chondrogenic capacity assessed in pellet cultures. Expanded chondrocytes were also cultured for up to 6 weeks in HYAFF-M nonwoven meshes or Polyactive foams, and the resulting cartilaginous tissues were assessed histologically, biochemically, and biomechanically. Supplementation of the expansion medium with FGF-2 increased the proliferation rate of goat chondrocytes and enhanced their postexpansion chondrogenic capacity. FGF-2-expanded chondrocytes seeded in HYAFF-M or Polyactive scaffolds formed cartilaginous tissues with wet weight, glycosaminoglycan, and collagen content, increasing from 2 days to 6 weeks culture (up to respectively 2-, 8-, and 41-fold). Equilibrium and dynamic stiffness measured in HYAFF M-based constructs also increased with time, up to, respectively, 1.3- and 16-fold. This study demonstrates the feasibility to engineer goat cartilaginous tissues at different stages of development by varying culture time, and thus opens the possibility to test the effect of maturation stage of engineered cartilage on the outcome of cartilage repair in orthotopic goat models.     

骨组织工程血管化的研究现状与挑战

对骨组织工程血管化的文献进行综述,介绍研究现状和最新科研成果,分析需解决的问题。提出各种新型生物材料、细胞移植、细胞因子以及显微技术加速移植物新生血管循环的建立是该领域的研究热点。     

Optimal control of one‐dimensional cellular uptake in tissue engineering

A control problem motivated by tissue engineering is formulated and solved, in which control of the uptake of growth factors (signaling molecules) is necessary to spatially and temporally regulate cellular processes for the desired growth or regeneration of a tissue. Four approaches are compared for determining one‐dimensional optimal boundary control trajectories for a distributed parameter model with reaction, diffusion, and convection: (i) basis function expansion, (ii) method of moments, (iii) internal model control, and (iv) model predictive control (MPC). The proposed method of moments approach is computationally efficient while enforcing a nonnegativity constraint on the control input. Although more computationally expensive than methods (i)–(iii), the MPC formulation significantly reduced the computational cost compared with simultaneous optimization of the entire control trajectory. A comparison of the pros and cons of each of the four approaches suggests that an algorithm that combines multiple approaches is most promising for solving the optimal control problem for multiple spatial dimensions. Copyright © 2012 John Wiley & Sons, Ltd.     

Adult ovine chondrocytes in expansion culture adopt progenitor cell properties that are favorable for cartilage tissue engineering

Human chondrocytes in expansion culture can become progenitor-like in their ability to proliferate extensively and secrete neocartilage in chondrogenic culture. Sheep are used as a large animal model for cartilage tissue engineering, although for testing progenitor-like chondrocytes it is important that ovine chondrocytes resemble human in the ability to adopt progenitor properties. Here, we investigate whether ovine chondrocytes can adopt progenitor properties as indicated by rapid proliferation in a colony-forming fashion, and high levels of neocartilage secretion in chondrogenic culture. In conditions known to promote expansion of mesenchymal stromal cells, ovine chondrocytes proliferated through approximately 12 population doublings in 10 days. Time-lapse imaging indicated rapid proliferation in a colony-forming pattern. Expanded ovine chondrocytes that were seeded into agarose and cultured in chondrogenic medium accumulated neocartilage over 2 weeks, to a greater extent than primary chondrocytes. These data confirm that ovine chondrocytes resemble human chondrocytes in their ability to acquire progenitor properties that are important for cartilage tissue engineering. Given the broad interest in using progenitor cells to heal connective tissues, next we compared proliferation and trilineage differentiation of ovine chondrocytes, meniscus cells, and tenocytes. Meniscus cells and tenocytes experienced more than 13 population doublings in 10 days. In chondrogenic culture, cartilage matrix accumulation, and gene expression were largely similar among the cell types. All cell types resisted osteogenesis, while expanded tenocytes and meniscal cells were capable of adipogenesis. While ovine connective tissue cells demonstrated limited lineage plasticity, these data support the potential to promote certain progenitor properties with expansion.     

皮肤组织工程学在我国

Great progress has been made in the basic research and clinical application of skin tissue engineering in China over the past 20 years. It includes culture of epithelial cells and their preliminary clinicaluse , research and development of various dermal substitutes such as acellular dermal matrix, spongi form collagen membrane and high molecular weight polymer membrane , and modification of physical properties of dermal substitutes for the sake of raising their bioaffinity and vascular ization , based on which composite skin containing epithelial cell layers has been constructed and used successfully in the repair of full-thickness skin defects. More recently , greater efforts have been made in the study of new epithelial seeding cells such as epithelial stem cell and hair follicle stem cell. With the work going into the center, it is hopeful into constructing an artificial skin that mimics the normal human skin in terms of structure and function with better viability of the transplant, so that it can eventually be used in clinical practice as a skin source for large area deep burn patients to improve the wound healing quality.     

从膀胱癌患者分离并培养人膀胱平滑肌细胞

目的：建立从膀胱癌患者的分离并培养膀胱平滑肌细胞的实验技术.方法：取一小块无明显肿瘤生长的膀胱组织,分离并培养膀胱平滑肌细胞;动态观察细胞形态变化、生长增殖情况以及平滑肌肌动蛋白（SMA）、结蛋白（Desmin）和广谱细胞角蛋白（AE1/AE3）的表达.结果：接种24 h后即有长梭形细胞贴壁生长,10天后长至80%融合,呈典型的＂峰谷＂样形态;传代后1天为潜伏期,2～6天为指数生长期,然后进入融合平台期,需再次传代.第2代细胞的SMA和Desmin表达阳性率分别高达（99.0±0.8）%和（97.0±2.1）%,不表达AE1/AE3.随着传代次数的增加,细胞去分化,细胞形态变成短梭状或椭圆形;SMA和Desmin的表达开始下降,传至第5代时,SMA和Desmin阳性率分别降至（78.0±3.3）%和（74.0±2.6）%;至第7代时,SMA和Desmin阳性率降至（51.0±3.0）%和（49.0±2.6）%.第7代细胞经血清饥饿培养48 h后,细胞又能再分化,形态转变成长梭状,SMA和Desmin阳性率可分别升至（90.0±3.5）%和（88.0±2.5）%,具有显著性差异.结论：本研究所培养的人膀胱平滑肌细胞具有较高的纯度,血清饥饿能促进去分化的细胞再分化,能为构建组织工程膀胱提供种子细胞.     

软骨组织工程支架材料研究进展

各种原因引起的关节软骨损伤在临床工作中非常常见,但临床治疗手段有限,组织工程的发展为关节软骨损伤的修复提供了新的途径。在软骨组织工程中支架材料起着重要作用,选择合适的载体是一个首先要解决的问题。本文对目前软骨组织工程支架材料的现状做一综述,指出了当前软骨组织工程所面临的问题,并针对此问题对未来软骨组织工程材料的研究作出了展望。     

Low-power laser stimulation of tissue engineered cartilage tissue formed on a porous calcium polyphosphate scaffold

BACKGROUND AND OBJECTIVE: Forming cartilage tissue in vitro that resembles native tissue is one of the challenges of cartilage tissue engineering. The aim of this study was to determine whether low-power laser stimulation would improve the formation of cartilage tissue in vitro. STUDY DESIGN/MATERIALS AND METHODS: Bovine articular chondrocytes were seeded on the top surface of porous calcium polyphosphate substrates. After 2 days, laser stimulation was applied daily at a wavelength of 650 nm using a laser diode with energy densities of either 1.75 or 3 J/cm(2) for 4 weeks. Proteoglycan and collagen synthesis and matrix content were determined. Cartilage tissue morphology was evaluated histologically. RESULTS: Histologically, there was no difference in the appearance or cellularity of the tissues that formed in the presence or absence of laser stimulation at either dosage. There were no differences in DNA content between treated and untreated constructs and live-dead assay confirmed that this treatment was not toxic to the cells. Laser stimulation at 3 J/cm(2) enhanced matrix synthesis resulting in significantly more tissue formation than laser stimulation at 1.75 J/cm(2) or untreated cultures. CONCLUSION: Short exposures to low-power laser stimulation using a laser diode with 3 J/cm(2) dose improves cartilage tissue formation.     

Strategies in cardiac tissue engineering

In heart failure, post-myocardial infarction and some congenital cardiac anomalies, organ transplantation is the only effective cure. Shortage of organ donors and complications of orthotopic heart transplant remain major challenges to the modern field of transplantation. Tissue engineering using cell-based strategies presents itself as a new way of generating functional myocardium. Engineering functional myocardium de novo requires an abundant source of cells that can form cardiomyocytes. These cells may be used with biocompatible scaffold materials to generate a contractile myocardium. Lastly, to sustain the high metabolism of the construct, a functional vasculature needs to be developed with the forming cardiac tissue. This review provides an update on the progress of stem cell research in the context of cardiac tissue development, types of biomaterials used in cardiac tissue engineering (CTE) and currently employed strategies for vascularization in CTE. In addition, a brief overview of strategies utilized in CTE is provided.     

组织工程皮肤修复皮肤缺损的初步实验研究

目的:探讨组织工程皮肤移植的手术方法、注意事项及临床效果。方法:2.5～3月龄约克猪6只,制备全厚皮肤缺损创面48个,随机分为三组,每组16例。A组:组织工程全层皮肤移植组;B组:组织工程真皮和自体表皮复合移植组;C组(对照组):自体全厚皮片移植组。观察实验组与对照组间的治愈率。结果:A组治愈率75.00%,B组治愈率87.50%,C组治愈率93.75%,三组比较无显著性差异(χ2=2.34,P>0.05)。结论:组织工程皮肤修复皮肤缺损是可行的。