Poly-<Emphasis Type="SmallCaps">l</Emphasis>-Lactic Acid/Hydroxyapatite Electrospun Nanocomposites Induce Chondrogenic Differentiation of Human MSC

Cartilage and bone tissue engineering has been widely investigated but is still hampered by cell differentiation and transplant integration issues within the constructs. Scaffolds represent the pivotal structure of the engineered tissue and establish an environment for neo-extracellular matrix synthesis. They can be associated to signals to modulate cell activity. In this study, considering the well reported role of hydroxyapatite (HA) in cartilage repair, we focused on the putative chondrogenic differentiation of human mesenchymal stem cells (hMSCs) following culture on membranes of electrospun fibers of poly-l-lactic acid (PLLA) loaded with nanoparticles of HA. hMSCs were seeded on PLLA/HA and bare PLLA membranes and cultured in basal medium, using chondrogenic differentiation medium as a positive control. After 14 days of culture, SOX-9 positive cells could be detected in the PLLA/HA group. Cartilage specific proteoglycan immunostain confirmed the presence of neo-extracellular-matrix production. Co-expression of CD29, a typical surface marker of MSCs and SOX-9, suggested different degrees in the differentiation process. We developed a hydroxyapatite functionalized scaffold with the aim to recapitulate the native histoarchitecture and the molecular signaling of osteochondral tissue to facilitate cell differentiation toward chondrocyte. PLLA/HA nanocomposites induced differentiation of hMSCs in a chondrocyte-like phenotype with generation of a proteoglycan based matrix. This nanocomposite could be an amenable alternative scaffold for cartilage tissue engineering using hMSCs.     

Functionalized PLGA-doped zirconium oxide ceramics for bone tissue regeneration

Bone tissue engineering is an alternative approach to bone grafts. In our study we aim to develop a composite scaffold for bone regeneration made of doped zirconium oxide (ZrO₂) conjugated with poly(lactic-co-glycolic acid) (PLGA) particles for the delivery of growth factors. In this composite, the PLGA microspheres are designed to release a crucial growth factor for bone formation, bone morphogenetic protein-2 (BMP2). We found that by changing the polymer’s molecular weight and composition, we could control microsphere loading, release and size. The BMP2 released from PLGA microspheres retained its biological activity and increased osteoblastic marker expression in human mesenchymal stem cells (hMSCs). Uncapped PLGA microspheres were conjugated to ZrO₂ scaffolds using carbodiimide chemistry, and the composite scaffold was shown to support hMSCs growth. We also demonstrated that human umbilical vein endothelial cells (HUVECs) can be co-cultured with hMSCs on the ZrO₂ scaffold for future vascularization of the scaffold. The ZrO₂ composite scaffold could serve as a bone substitute for bone grafting applications with the added ability of releasing different growth factors needed for bone regeneration.     

电纺纳米羟基磷灰石/聚酯酰胺复合支架材料的制备及其细胞相容性

背景：采用静电纺丝技术将功能性无机纳米微粒复合高分子超细纤维,形成类细胞外基质结构和功能的复合支架材料是骨组织工程支架领域一个新的研究方向。 目的：通过静电纺丝法构建纳米羟基磷灰石/脂肪族聚酯酰胺复合纤维支架材料,并初步考察其细胞相容性。 方法：以静电纺丝法制备纳米羟基磷灰石/脂肪族聚酯酰胺超细纤维支架材料,通过扫描电镜、原子能谱等表面形貌的物相分析,进行细胞在复合材料上的形态学观察。 结果与结论：通过静电纺丝法成功制备出纳米羟基磷灰石/脂肪族聚酯酰胺超细纤维复合材料,成骨细胞直接培养于材料上呈现良好生长行为,初步证实了复合支架材料的细胞相容性。说明静电纺丝技术在构建类骨细胞外基质结构和功能的仿生复合材料方面具有独特优势,电纺超细纤维复合材料有望成为新型的骨组织工程支架。     

骨髓间充质干细胞在淫羊藿苷/羟基磷灰石/聚乳酸-羟基乙酸共聚物支架上的成骨

文题释义：纳米结构：是尺寸介于分子和微米尺度间的物体结构。当纳米羟基磷灰石与高分子材料物理混合后,羟基磷灰石会发生自聚,从而在材料表面产生纳米结构。这种纳米结构有利于细胞(如骨髓充间质干细胞)的黏附,是骨修复材料表面细胞增殖和后期成骨分化的基础。成骨分化：当干细胞接受诱导时可以向成骨细胞转变。淫羊藿苷高分子复合支架与间充质干细胞共培养一段时间后,其骨分化标志物碱性磷酸酶和骨钙素的活性增高,同时成骨相关基因和蛋白(Runx-2、COLⅠ)表达水平上升,即细胞在淫羊藿苷诱导下发生了成骨分化。  摘要背景：近年来,骨组织工程技术为临床治疗骨缺损提供了全新的思路和模式。该研究首次将传统中药与组织工程支架的纳米结构结合,以期探索并构建一种可用于骨缺损治疗的新型骨组织替代材料。目的：研究淫羊藿苷(icariin,ICA)/羟基磷灰石(hydroxyapatite,HA)/聚乳酸-羟基乙酸共聚物(poly(lactic-co-glycolic acid),PLGA)复合支架的成骨活性。方法：将HA与PLGA通过物理共混的方式制成HA/PLGA复合支架,然后将其浸泡于不同浓度的ICA溶液中,从而得到ICA/HA/PLGA支架。利用兔骨髓间充质干细胞分别对复合支架的细胞黏附、增殖、成骨作用和细胞毒性进行评价。细胞黏附、细胞增殖和细胞毒性采用MTT法进行检测,碱性磷酸酶活性和骨钙素活性采用ELISA法进行检测,成骨相关基因和蛋白表达水平分别用荧光定量PCR和Western blot法进行检测。结果与结论：①PLGA中加入适量HA可以提高支架的力学强度,且在HA含量为10%时效果最佳,拉伸强度为(1.67±0.37) MPa;压缩模量为(4.17±1.62) MPa,且会在支架表面形成纳米结构;该微结构可以促进骨髓间充质干细胞在支架表面的黏附;②ICA不会影响骨髓间充质干细胞在复合支架上的增殖,且1.00 µmol/L ICA水溶液浸泡后的ICA/HA/PLGA复合支架具有最优的成骨分化功能,其碱性磷酸酶活性、骨钙素活性、成骨相关基因和蛋白(Runx-2和COLⅠ)的表达水平均最高;③ICA/HA/PLGA复合支架无细胞毒性;④结果表明,HA(10%)/ICA(1.00 µmol/L)/PLGA支架具有良好的机械性能、成骨作用和生物相容性,是一种具有良好应用潜力的骨组织工程支架。ORCID: 0000-0002-9770-9109(王德欣) 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     

Osteogenic Induction of Bone Marrow-Derived Stromal Cells on Simvastatin-Releasing,Biodegradable, Nano- to Microscale Fiber Scaffolds

Tissue engineering is an effective approach for the treatment of bone defects. Statins have been demonstrated to promote osteoblastic differentiation of bone marrow-derived stromal cells (BMSCs). Electrospun biodegradable fibers have also shown applicability to drug delivery in the form of bone tissue engineered scaffolds with nano- to microscale topography and high porosity similar to the natural extracellular matrix (ECM). The aim of this study was to investigate the feasibility of a simvastatin-releasing, biodegradable, nano- to microscale fiber scaffold (SRBFS) for bone tissue engineering with BMSCs. Simvastatin was released from SRBFS slowly. BMSCs were observed to spread actively and rigidly adhere to SRBFS. BMSCs on SRBFS showed an increase in alkaline phosphatase activity 2 weeks after cell culture. Furthermore, osteoclastogenesis was suppressed by SRBFS in vitro. The new bone formation and mineralization in the SRBFS group were significantly better than in the biodegradable fiber scaffold (BFS) without simvastatin 12 weeks after implantation of the cell-scaffold construct into an ectopic site on the murine back. These results suggest that SRBFS promoted osteoblastic differentiation of BMSCs in vitro and in vivo, and demonstrate feasibility as a bone engineering scaffold.     

In vitro osteogenic differentiation of human mesenchymal stem cells and in vivo bone formation in composite nanofiber meshes

Tissue engineering has become an alternative method to traditional surgical treatments for the repair of bone defects, and an appropriate scaffold supporting bone formation is a key element in this approach. In the present study, nanofibrous organic and inorganic composite scaffolds containing nano-sized demineralized bone powders (DBPs) with biodegradable poly(L-lactide) (PLA) were developed using an electrospinning process for engineering bone. To assess their biocompatibility, in vitro osteogenic differentiation of human mandible-derived mesenchymal stem cells (hMSCs) cultured on PLA or PLA/DBP composite nanofiber scaffolds were examined. The mineralization of hMSCs cultured with osteogenic supplements on the PLA/DBP nanofiber scaffolds was remarkably greater than on the PLA nanofiber scaffold during the first 14 days of culture but reached the same level after 21 days. The in vivo osteoconductive effect of PLA/DBP nanofibrous scaffolds was further investigated using rats with critical-sized skull defects. Micro-computerized tomography revealed that a greater amount of newly formed bone extended across the defect area in PLA/DBP scaffolds than in the nonimplant and PLA scaffolds 12 weeks after implantation and that the defect size was almost 90% smaller. Therefore, PLA/DBP composite nanofiber scaffolds may serve as a favorable matrix for the regeneration of bone tissue.     

Multilineage differentiation of human mesenchymal stem cells in a three-dimensional nanofibrous scaffold

Functional engineering of musculoskeletal tissues generally involves the use of differentiated or progenitor cells seeded with specific growth factors in biomaterial scaffolds. Ideally, the scaffold should be a functional and structural biomimetic of the native extracellular matrix and support multiple tissue morphogenesis. We have previously shown that electrospun, three-dimensional nanofibrous scaffolds that morphologically resemble collagen fibrils are capable of promoting favorable biological responses from seeded cells, indicative of their potential application for tissue engineering. In this study, we tested a three-dimensional nanofibrous scaffold fabricated from poly(epsilon-caprolactone) (PCL) for its ability to support and maintain multilineage differentiation of bone marrow-derived human mesenchymal stem cells (hMSCs) in vitro. hMSCs were seeded onto pre-fabricated nanofibrous scaffolds, and were induced to differentiate along adipogenic, chondrogenic, or osteogenic lineages by culturing in specific differentiation media. Histological and scanning electron microscopy observations, gene expression analysis, and immunohistochemical detection of lineage-specific marker molecules confirmed the formation of three-dimensional constructs containing cells differentiated into the specified cell types. These results suggest that the PCL-based nanofibrous scaffold is a promising candidate scaffold for cell-based, multiphasic tissue engineering.     

Collagen I gel promotes homogenous osteogenic differentiation of adipose tissue-derived mesenchymal stem cells in serum-derived albumin scaffold

Repair of bone defects is a difficult clinical problem for reconstructive surgeons. Bone tissue engineering using an appropriate scaffold with cells is a new therapy for the repair of bone defects. The aim of this study was to evaluate the in vitro osteogenesis of canine adipose tissue-derived mesenchymal stem cells (Ad-MSCs) cultured in a combination of collagen I gel and a porous serum-derived albumin scaffold. A serum-derived albumin scaffold was prepared with canine serum by cross-linking and freeze-drying procedures. Ad-MSCs were seeded into serum-derived albumin scaffolds with or without collagen I gel, and were exposed to osteogenic differentiation conditions in vitro. After 28?days of in vitro culture, the distribution and osteogenic differentiation of Ad-MSCs cultured in the scaffold were evaluated by scanning electron microscopy, histology, immunohistochemistry, alkaline phosphatase (ALP) activity assay, and calcium colorimetric assay. Ad-MSCs showed more homogeneous distribution and osteogenic differentiation in the scaffold with collagen I gel than without collagen I gel. ALP activity and extracellular matrix mineralization in the construct with type I collagen were significantly higher than in the construct without type I collagen (p?<?0.05). In conclusion, the combination of collagen I gel and the serum-derived albumin scaffold enhanced osteogenic differentiation and homogenous distribution of Ad-MSCs.     

A Dynamically Cultured Collagen/Cells-Incorporated Elastic Scaffold for Small-Diameter Vascular Grafts

Abstract

There is an essential demand for tissue-engineered autologous small-diameter vascular grafts, which offer temporary supports and guides for vascular tissue organization, repair and remodeling. This study reports on the effect of collagen/smooth muscle cells (SMCs) mixtures under dynamic cultures and SMC-endothelial cell (ECs) co-culture on cell proliferation, uniform cell distribution, extracellular matrix deposition, and endothelial cells monolayer formation in tissue-engineered tubular arterial constructs of 4 mm inner diameter. Rabbit aortic SMCs were infiltrated with collagen solution in poly(L-lactide-co-?-caprolactone) (PLCL) scaffolds under vacuum to form collagenous gel and subjected to dynamic strain by culturing them in a dynamic perfusion bioreactor. The construct lumen was subsequently seeded with ECs and experiments were completed to create ECs–SMCs co-culture constructs. The collagen/SMCs incorporated elastic scaffold cultured under dynamic culture conditions promoted matrix deposition, leading to the development of tissue-engineered vascular constructs, and induced SMC to have more uniform cell distribution. Scanning electron microscopic examination and von Willebrand Factor staining demonstrated the presence of ECs spread over the lumen. Quantitative analysis of elastin contents demonstrated that the engineered vessels acquired similar elastin contents as native arteries. The collagen/SMCs/ECs incorporated PLCL scaffolds under dynamic culture conditions can be used as a scaffold for tissue engineering to facilitate small-diameter vascular-tissue formation.     

The effect of mechanical stimulation on the maturation of TDSCs-poly(L-lactide-co-e-caprolactone)/collagen scaffold constructs for tendon tissue engineering

Mechanical stimulation plays an important role in the development and remodeling of tendons. Tendon-derived stem cells (TDSCs) are an attractive cell source for tendon injury and tendon tissue engineering. However, these cells have not yet been fully explored for tendon tissue engineering application, and there is also lack of understanding to the effect of mechanical stimulation on the maturation of TDSCs-scaffold construct for tendon tissue engineering. In this study, we assessed the efficacy of TDSCs in a poly(L-lactide-co-ε-caprolactone)/collagen (P(LLA-CL)/Col) scaffold under mechanical stimulation for tendon tissue engineering both in vitro and in vivo, and evaluated the utility of the transplanted TDSCs-scaffold construct to promote rabbit patellar tendon defect regeneration. TDSCs displayed good proliferation and positive expressed tendon-related extracellular matrix (ECM) genes and proteins under mechanical stimulation in vitro. After implanting into the nude mice, the fluorescence imaging indicated that TDSCs had long-term survival, and the macroscopic evaluation, histology and immunohistochemistry examinations showed high-quality neo-tendon formation under mechanical stimulation in vivo. Furthermore, the histology, immunohistochemistry, collagen content assay and biomechanical testing data indicated that dynamically cultured TDSCs-scaffold construct could significantly contributed to tendon regeneration in a rabbit patellar tendon window defect model. TDSCs have significant potential to be used as seeded cells in the development of tissue-engineered tendons, which can be successfully fabricated through seeding of TDSCs in a P(LLA-CL)/Col scaffold followed by mechanical stimulation.     

Three-dimensional nano-HAp/collagen matrix loading with osteogenic cells in organ culture.

Transplantation of osteogenic cells with a suitable matrix is one strategy for engineering bone tissue. Three-dimensional distribution and growth of cells within the porous scaffold are of clinical significance for the repair of large bony defects. A nano-HAp/collagen (nHAC) composite that mimics the natural bone both in composition and microstructure to some extent was employed as a matrix for the tissue engineering of bone. A porous nHAC composite was produced in sheet form and convolved to be a three-dimensional scaffold. Using organ culture techniques and the convolving method, we have developed three-dimensional osteogenic cells/nHAC constructs in vitro. Scanning electron microscopic and histological examination has demonstrated the development of the cells/material complex. Spindle-shaped cells migrating out of bone fragments continuously proliferated and migrated throughout the network of the coil. The porous nHAC scaffold provided a microenvironment resembling that seen in vivo, and cells within the composite eventually acquired a tridimensional polygonal shape. In addition, new bone matrix was synthesized at the interface of bone fragments and the composite.     

Mesenchymal stem cell-seeded collagen matrices for bone repair: effects of cyclic tensile strain, cell density, and media conditions on matrix contraction in vitro

Type I collagen is the most abundant extracellular matrix protein in bone and contains arginine- glycine-aspartic acid sequences that promote cell adhesion and proliferation. We have previously shown that human mesenchymal stem cells (hMSCs) seeded in three-dimensional (3D) collagen gels upregulate BMP-2 mRNA expression in response to tensile strain, indicative of osteogenesis. Therefore, collagen could be a promising scaffold material for functional bone tissue engineering using hMSCs. However, high contraction of the collagen gels by hMSCs poses a challenge to creating large, tissue-engineered bone constructs. The effects of cyclic tensile strain, medium (with and without dexamethasone), and hMSC seeding density on contraction of collagen matrices have not been investigated. hMSCs were seeded in 3D collagen gels and subjected to cyclic tensile strain of 10% or 12% for 4 h/day at a frequency of 1 Hz in osteogenic-differentiating or complete MSC growth media for up to 14 days. Viability of hMSCs was not affected by strain or media conditions. While initial seeding density affected matrix contraction alone, there was a high interdependence of strain and medium on matrix contraction. These findings suggest a correlation between hMSC proliferation and osteogenic differentiation on collagen matrix contraction that is affected by media, cell-seeding density, and cyclic tensile strain. It is vital to understand the effects of culture conditions on collagen matrix contraction by hMSCs in order to consider hMSC-seeded collagen constructs for functional bone tissue engineering in vitro.     

聚左旋乳酸/壳聚糖电纺丝纳米纤维支架与兔内皮祖细胞的生物相容性

背景：电纺丝技术能够使许多高分子材料制备出与细胞外基质相似的三维纳米纤维支架。聚乳酸/壳聚糖纳米纤维复合支架材料能够克服材料的不足,提高组织工程支架生物相容性。 目的：评价聚左旋乳酸/壳聚糖电纺丝纳米纤维支架与兔内皮祖细胞的生物相容性。 方法：电纺丝技术制备聚左旋乳酸,壳聚糖,聚左旋乳酸/壳聚糖的纳米纤维支架,扫描电镜观察其形貌结构。纳米纤维支架与内皮祖细胞进行复合培养后,观察细胞在不同材料上的黏附率、一氧化氮分泌,生长特征和在聚左旋乳酸/壳聚糖纳米纤维支架上的细胞表型特征。 结果与结论：聚左旋乳酸/壳聚糖纳米纤维支架比聚左旋乳酸、壳聚糖具有更合适的纤维直径,具有与细胞外基质相似的纳米纤维三维多孔结构。聚左旋乳酸/壳聚糖纳米纤维支架能够促进内皮祖细胞黏附率和细胞的一氧化氮分泌(P < 0.05,P < 0.01)。内皮祖细胞能够在聚左旋乳酸/壳聚糖复合材料膜上融合成片,保持了细胞的完整形态和分化功能,显示了内皮细胞特异性的vWF表型。提示聚左旋乳酸/壳聚糖电纺丝纳米纤维支架与兔内皮祖细胞具有良好的生物相容性。     

The influence of cyclic tensile strain on multi-compartment collagen-GAG scaffolds for tendon-bone junction repair

ABSTRACT

Background: Orthopedic injuries often occur at the interface between soft tissues and bone. The tendon-bone junction (TBJ) is a classic example of such an interface. Current clinical strategies for TBJ injuries prioritize mechanical reattachment over regeneration of the native interface, resulting in poor outcomes. The need to promote regenerative healing of spatially-graded tissues inspires our effort to develop new tissue engineering technologies that replicate features of the spatially-graded extracellular matrix and strain profiles across the native TBJ.

Materials and Methods: We recently described a biphasic collagen-glycosaminoglycan (CG) scaffold containing distinct compartment with divergent mineral content and structural alignment (isotropic vs. anisotropic) linked by a continuous interface zone to mimic structural and compositional features of the native TBJ.

Results: Here, we report application of cyclic tensile strain (CTS) to the scaffold via a bioreactor leads to non-uniform strain profiles across the spatially-graded scaffold. Further, combinations of CTS and matrix structural features promote rapid, spatially-distinct differentiation profiles of human bone marrow-derived mesenchymal stem cells (MSCs) down multiple osteotendinous lineages. CTS preferentially upregulates MSC activity and tenogenic differentiation in the anisotropic region of the scaffold. This work demonstrates a tissue engineering approach that couples instructive biomaterials with cyclic tensile stimuli to promote regenerative healing of orthopedic interfaces.     

Fabrication and characterization of chitosan/OGP coated porous poly(ε-caprolactone) scaffold for bone tissue engineering

As one of the stimulators on bone formation, osteogenic growth peptide (OGP) improves both proliferation and differentiation of the bone cells in vitro and in vivo. The aim of this work was the preparation of three dimensional porous poly(ε-caprolactone) (PCL) scaffold with high porosity, well interpore connectivity, and then its surface was modified by using chitosan (CS)/OGP coating for application in bone regeneration. In present study, the properties of porous PCL and CS/OGP coated PCL scaffold, including the microstructure, water absorption, porosity, hydrophilicity, mechanical properties, and biocompatibility in vitro were investigated. Results showed that the PCL and CS/OGP-PCL scaffold with an interconnected network structure have a porosity of more than 91.5, 80.8%, respectively. The CS/OGP-PCL scaffold exhibited better hydrophilicity and mechanical properties than that of uncoated PCL scaffold. Moreover, the results of cell culture test showed that CS/OGP coating could stimulate the proliferation and growth of osteoblast cells on CS/OGP-PCL scaffold. These finding suggested that the surface modification could be a effective method on enhancing cell adhesion to synthetic polymer-based scaffolds in tissue engineering application and the developed porous CS/OGP-PCL scaffold should be considered as alternative biomaterials for bone regeneration.     

Preparation and characterization of bionic bone structure chitosan/hydroxyapatite scaffold for bone tissue engineering

Three-dimensional oriented chitosan (CS)/hydroxyapatite (HA) scaffolds were prepared via in situ precipitation method in this research. Scanning electron microscopy (SEM) images indicated that the scaffolds with acicular nano-HA had the spoke-like, multilayer and porous structure. The SEM of osteoblasts which were polygonal or spindle-shaped on the composite scaffolds after seven-day cell culture showed that the cells grew, adhered, and spread well. The results of X-ray powder diffractometer and Fourier transform infrared spectrometer showed that the mineral particles deposited in the scaffold had phase structure similar to natural bone and confirmed that particles were exactly HA. In vitro biocompatibility evaluation indicated the composite scaffolds showed a higher degree of proliferation of MC3T3-E1 cell compared with the pure CS scaffolds and the CS/HA10 scaffold was the highest one. The CS/HA scaffold also had a higher ratio of adhesion and alkaline phosphate activity value of osteoblasts compared with the pure CS scaffold, and the ratio increased with the increase of HA content. The ALP activity value of composite scaffolds was at least six times of the pure CS scaffolds. The results suggested that the composite scaffolds possessed good biocompatibility. The compressive strength of CS/HA15 increased by 33.07% compared with the pure CS scaffold. This novel porous scaffold with three-dimensional oriented structure might have a potential application in bone tissue engineering.     

Tissue compatibility of interfacial polyelectrolyte complexation fibrous scaffold: evaluation of blood compatibility and biocompatibility

Interfacial polyelectrolyte complexation (PEC) fiber has been proposed as a biostructural unit and biological construct for tissue engineering applications, with its ability to incorporate proteins, drug molecules, DNA nanoparticles, and cells. In this study, we evaluated the biocompatibility and blood compatibility of PEC fiber in order to assess its potential for in vivo applications in tissue engineering. Although chitosan-alginate PEC fibrous scaffold was found to be thrombogenic, the blood compatibility of the scaffold could be significantly improved by incorporating a small amount of heparin in the polyelectrolyte solution during fiber formation. The platelet microparticle production and platelet adhesion on the chitosan-alginate-heparin fibrous scaffold were comparable to those on the resting control. In vitro cytotoxicity test showed that the scaffold was not toxic to human mesenchymal stem cells (hMSCs). In the in vivo biocompatibility test in rats, no acute inflammation was observed in the subcutaneously or intramuscularly implanted specimens. Good cell infiltration and vascularization were observed after 2 months of implantations. Enhanced extracellular matrix (ECM) deposition was observed when hMSCs were cultured in the transforming growth factor-beta3 (TGF-beta3)-encapsulated PEC fibrous scaffold in vitro, or when the TGF-beta3-encapsulated PEC was implanted intramuscularly in vivo. The results showed that this versatile PEC fibrous scaffold could be used in various tissue engineering applications for its good biocompatible and blood compatible properties.     

Development of a biodegradable scaffold with interconnected pores by heat fusion and its application to bone tissue engineering

Tissue engineering has been proposed as an approach to alleviate the shortage of donor tissue and organs by combining cells and a biodegradable scaffold as a temporary extracellular matrix. While numerous scaffold fabrication methods have been proposed, tissue formation is typically limited to the surface of the scaffolds in bone tissue engineering applications due to early calcification on the surface. To improve tissue formation, a novel scaffold with a hierarchical interconnected pore structure on two distinct length scales has been developed. Here we present the fabrication process and the application of the scaffold to bone tissue engineering. Porous poly(lactide-co-glycolide) (PLGA) scaffolds were made by combining solvent casting/particulate leaching with heat fusion. Porcine bone marrow-derived mesenchymal stem cells (MSCs) were differentiated into osteoblasts and cultured on these scaffolds in vitro for 2, 4, and 6 weeks. Subsequently, the constructs were assessed using histology and scanning electron microscopy. The bone marrow-derived osteoblasts attached well on these scaffolds. Cells were observed throughout the scaffolds. These initial results show promise for this scaffold to aid in the regeneration of bone.     

<Emphasis Type="Italic">In vivo</Emphasis> MR Imaging of Tissue-engineered Human Mesenchymal Stem Cells Transplanted to Mouse: a Preliminary Study

Current progress integrating stem cell biology and tissue engineering techniques has been invaluable to clinical applications. Prior to the application of celluar transplantation technique to patients, we need to establish techniques that can monitor their tissue biodistribution non-invasively. In this study, we proposed an imaging modality using MRI to not only monitor implanted scaffold in vivo, but also to track transplanted cells and behavior around the implant. For this purpose, human bone marrow-derived mesenchymal stem cells (hMSCs) were labeled with superparamagnetic iron oxide (Feridex) and then labeled hMSCs were cultured in a gelatin sponge used as a scaffold to support cell growth and proliferation. Histological assessment and MTT assay showed that cell labeling with MR contrast agent did not harm cell viability. Also, Feridex-labeled hMSCs showed a significant decrease in T2 signal intensity, even within the gelatin sponge in vitro. After implanting the sponge/cell complex in vivo, we could visualize cellular behavior around the implant over time using a noninvasive MRI modality and this finding was correlated with histological study, which illustrates the potential of a new approach proposed here for in vivo monitoring of implanted cell-based tissue-engineered product.