Evaluation of articular cartilage repair using biodegradable nanofibrous scaffolds in a swine model: a pilot study

The aim of this study was to evaluate a cell‐seeded nanofibrous scaffold for cartilage repair in vivo. We used a biodegradable poly(ε‐caprolactone) (PCL) nanofibrous scaffold seeded with allogeneic chondrocytes or xenogeneic human mesenchymal stem cells (MSCs), or acellular PCL scaffolds, with no implant as a control to repair iatrogenic, 7 mm full‐thickness cartilage defects in a swine model. Six months after implantation, MSC‐seeded constructs showed the most complete repair in the defects compared to other groups. Macroscopically, the MSC‐seeded constructs regenerated hyaline cartilage‐like tissue and restored a smooth cartilage surface, while the chondrocyte‐seeded constructs produced mostly fibrocartilage‐like tissue with a discontinuous superficial cartilage contour. Incomplete repair containing fibrocartilage or fibrous tissue was found in the acellular constructs and the no‐implant control group. Quantitative histological evaluation showed overall higher scores for the chondrocyte‐ and MSC‐seeded constructs than the acellular construct and the no‐implant groups. Mechanical testing showed the highest equilibrium compressive stress of 1.5 MPa in the regenerated cartilage produced by the MSC‐seeded constructs, compared to 1.2 MPa in the chondrocyte‐seeded constructs, 1.0 MPa in the acellular constructs and 0.2 MPa in the no‐implant group. No evidence of immune reaction to the allogeneically‐ and xenogeneically‐derived regenerated cartilage was observed, possibly related to the immunosuppressive activities of MSCs, suggesting the feasibility of allogeneic or xenogeneic transplantation of MSCs for cell‐based therapy. Taken together, our results showed that biodegradable nanofibrous scaffolds seeded with MSCs effectively repair cartilage defects in vivo, and that the current approach is promising for cartilage repair. Copyright © 2008 John Wiley & Sons, Ltd.     

Construction of tissue‐engineered osteochondral composites and repair of large joint defects in rabbit

In this study, a novel three‐dimensional (3D) heterogeneous/bilayered scaffold was constructed to repair large defects in rabbit joints. The scaffold includes two distinct but integrated layers corresponding to the cartilage and bone components. The upper layer consists of gelatin, chondroitin sulphate and sodium hyaluronate (GCH), and the lower layer consists of gelatin and ceramic bovine bone (GCBB). The two form a 3D bilayered scaffold (GCH–GCBB), which mimics the natural osteochondral matrix for use as a scaffold for osteochondral tissue engineering. The purpose of this study was to evaluate the efficacy of this novel scaffold, combined with chondrocytes and bone marrow stem cells (BMSCs) to repair large defects in rabbit joints. Thirty‐six large defects in rabbit femoral condyles were created; 12 defects were treated with the same scaffold combined with cells (group A); another 12 defects were treated with cell‐free scaffolds (group B); the others were untreated (group C). At 6 and 12 weeks, in group A hyaline‐like cartilage formation could be observed by histological examination; the newly formed cartilage, which stained for type II collagen, was detected by RT–PCR at high‐level expression. Most of the GCBB was replaced by bone, while little remained in the underlying cartilage. At 36 weeks, GCBB was completely resorbed and a tidemark was observed in some areas. In contrast, groups B and C showed no cartilage formation but a great amount of fibrous tissue, with only a little bone formation. In summary, this study demonstrated that a novel scaffold, comprising a top layer of GCH, having mechanical properties comparable to native cartilage, and a bottom layer composed of GCBB, could be used to repair large osteochondral defects in joints. Copyright © 2012 John Wiley & Sons, Ltd.     

Auricular cartilage repair using cryogel scaffolds loaded with BMP‐7‐expressing primary chondrocytes

The loss of cartilage tissue due to trauma, tumour surgery or congenital defects, such as microtia and anotia, is one of the major concerns in head and neck surgery. Recently tissue‐engineering approaches, including gene delivery, have been proposed for the regeneration of cartilage tissue. In this study, primary chondrocytes were genetically modified with plasmid‐encoding bone morphogenetic protein‐7 (BMP‐7) via the commercially available non‐viral Turbofect vector, with the aim of bringing ex vivo transfected chondrocytes to resynthesize BMP‐7 in vitro as they would in vivo. Genetically modified cells were implanted into gelatin–oxidized dextran scaffolds and cartilage tissue formation was investigated in 15 × 15 mm auricular cartilage defects in vivo in 48 New Zealand (NZ) white rabbits for 4 months. The results were evaluated via histology and early gene expression. Early gene expression results indicated a strong effect of exogenous BMP‐7 on matrix synthesis and chondrocyte growth. In addition, histological analysis results exhibited significantly better cartilage healing with BMP‐7‐modified (transfected) cells than in the non‐modified (non‐transfected) group and as well as the control. Copyright © 2012 John Wiley & Sons, Ltd.     

Utilizing tissue‐engineered cartilage or BMNC‐PLGA composites to fill empty spaces during autologous osteochondral mosaicplasty in porcine knees

The potential empty spaces between cylindrical plugs remaining after autologous osteochondral mosaicplasty rely on fibrous repair, which may constrain the quality and integrity of the repair. Thus, the empty spaces should be repaired, and how to fill the empty spaces is still a problem. In the present study, a standardized full‐thickness defect (diameter, 6 mm) was created in the weight‐bearing area of each medial femoral condyle in both knees of 18 miniature pigs. The 36 knees were randomly assigned to four groups with nine in each group. The defects were initially repaired by autologous osteochondral mosaicplasty. Simultaneously, any empty spaces between the multiple plugs were filled with cell‐free poly(lactide‐co‐glycolide) (PLGA) scaffolds (the scaffold group), tissue‐engineered cartilage (the TE group) or bone marrow mononuclear cell (BMNC)–PLGA composites (the composite group). The empty spaces were left untreated as control (the control group). Six months after surgery, the repair results were assessed via macroscopic observation, histological evaluation, magnetic resonance imaging, biomechanical assessment and glycosaminoglycan content. The results demonstrated that mosaicplasty combined with the treatment of the empty spaces could improve cartilage regeneration. The filling of empty spaces by tissue‐engineered cartilage produced the best result in all the four groups. Meanwhile, utilizing BMNC–PLGA composites achieved a similar repair result. Considering the cost‐effective, time‐saving and convenient performance, the BMNC‐PLGA composite could be an alternative option to fill the empty spaces combined with mosaicplasty. Copyright © 2014 John Wiley & Sons, Ltd.     

In vitro chondrogenesis with lysozyme susceptible bacterial cellulose as a scaffold

A current focus of tissue engineering is the use of adult human mesenchymal stem cells (hMSCs) as an alternative to autologous chondrocytes for cartilage repair. Several natural and synthetic polymers (including cellulose) have been explored as a biomaterial scaffold for cartilage tissue engineering. While bacterial cellulose (BC) has been used in tissue engineering, its lack of degradability in vivo and high crystallinity restricts widespread applications in the field. Recently we reported the formation of a novel bacterial cellulose that is lysozyme‐susceptible and ‐degradable in vivo from metabolically engineered Gluconacetobacter xylinus. Here we report the use of this modified bacterial cellulose (MBC) for cartilage tissue engineering using hMSCs. MBC's glucosaminoglycan‐like chemistry, combined with in vivo degradability, suggested opportunities to exploit this novel polymer in cartilage tissue engineering. We have observed that, like BC, MBC scaffolds support cell attachment and proliferation. Chondrogenesis of hMSCs in the MBC scaffolds was demonstrated by real‐time RT–PCR analysis for cartilage‐specific extracellular matrix (ECM) markers (collagen type II, aggrecan and SOX9) as well as histological and immunohistochemical evaluations of cartilage‐specific ECM markers. Further, the attachment, proliferation, and differentiation of hMSCs in MBC showed unique characteristics. For example, after 4 weeks of cultivation, the spatial cell arrangement and collagen type‐II and ACAN distribution resembled those in native articular cartilage tissue, suggesting promise for these novel in vivo degradable scaffolds for chondrogenesis. Copyright © 2013 John Wiley & Sons, Ltd.     

Activated platelet‐rich plasma improves cartilage regeneration using adipose stem cells encapsulated in a 3D alginate scaffold

In the current study, the effect of superimposing platelet‐rich plasma (PRP) on different culture mediums in a three‐dimensional alginate scaffold encapsulated with adipose‐derived mesenchymal stem cells for cartilage tissue repair is reported. The three‐dimensional alginate scaffolds with co‐administration of PRP and/or chondrogenic supplements had a significant effect on the differentiation of adipose mesenchymal stem cells into mature cartilage, as assessed by an evaluation of the expression of cartilage‐related markers of Sox9, collagen II, aggrecan and collagen, and glycosaminoglycan assays. For in vivo studies, following induction of osteochondral lesion in a rabbit model, a high degree of tissue regeneration in the alginate plus cell group (treated with PRP plus chondrogenic medium) compared with other groups of cell‐free alginate and untreated groups (control) were observed. After 8 weeks, in the alginate plus cell group, functional chondrocytes were observed, which produced immature matrix, and by 16 weeks, the matrix and hyaline‐like cartilage became completely homogeneous and integrated with the natural surrounding cartilage in the defect site. Similar effect was also observed in the subchondral bone. The cell‐free scaffolds formed fibrocartilage tissue, and the untreated group did not form a continuous cartilage over the defect by 16 weeks.     

Treatment of growth plate injury using IGF‐I‐loaded PLGA scaffolds

Growth plate fracture can lead to retarded growth and unequal limb length, which may have a lifelong effect on a person's physical stature. The goal of this research was to develop an in vivo tissue‐engineering approach for the treatment of growth plate injury via localized delivery of insulin‐like growth factor I (IGF‐I) from cell‐free poly(lactic‐co‐glycolic acid) (PLGA) scaffolds. Mass loss and drug release studies were conducted to study the scaffold degradation and IGF‐I release patterns. In vitro cell studies showed that rat bone marrow stromal cells seeded on the porous scaffolds colonized the pores and deposited matrix within the scaffolds. These in vitro evaluations were followed by a proof‐of‐concept animal study involving implantation of scaffolds in proximal tibial growth plate defects in New Zealand white rabbits. Histological analysis of tissue sections from the in vivo studies showed regeneration of cartilage, albeit with disorganized structure, at the site of implantation of IGF‐I‐releasing scaffolds; in contrast, only bone was formed in empty defects and those treated with IGF‐free scaffolds. The present findings show the potential for treating growth plate injury using in vivo tissue engineering techniques. Copyright © 2012 John Wiley & Sons, Ltd.     

An additive manufacturing‐based PCL–alginate–chondrocyte bioprinted scaffold for cartilage tissue engineering

Regenerative medicine is targeted to improve, restore or replace damaged tissues or organs using a combination of cells, materials and growth factors. Both tissue engineering and developmental biology currently deal with the process of tissue self‐assembly and extracellular matrix (ECM) deposition. In this investigation, additive manufacturing (AM) with a multihead deposition system (MHDS) was used to fabricate three‐dimensional (3D) cell‐printed scaffolds using layer‐by‐layer (LBL) deposition of polycaprolactone (PCL) and chondrocyte cell‐encapsulated alginate hydrogel. Appropriate cell dispensing conditions and optimum alginate concentrations for maintaining cell viability were determined. In vitro cell‐based biochemical assays were performed to determine glycosaminoglycans (GAGs), DNA and total collagen contents from different PCL–alginate gel constructs. PCL–alginate gels containing transforming growth factor‐β (TGFβ) showed higher ECM formation. The 3D cell‐printed scaffolds of PCL–alginate gel were implanted in the dorsal subcutaneous spaces of female nude mice. Histochemical [Alcian blue and haematoxylin and eosin (H&E) staining] and immunohistochemical (type II collagen) analyses of the retrieved implants after 4 weeks revealed enhanced cartilage tissue and type II collagen fibril formation in the PCL–alginate gel (+TGFβ) hybrid scaffold. In conclusion, we present an innovative cell‐printed scaffold for cartilage regeneration fabricated by an advanced bioprinting technology. Copyright © 2013 John Wiley & Sons, Ltd.     

Tissue‐engineered constructs: the effect of scaffold architecture in osteochondral repair

Cartilage has a poor regenerative capacity. Tissue‐engineering approaches using porous scaffolds seeded with chondrocytes may improve cartilage repair. The aim of this study was to examine the effect of pore size and pore interconnectivity on cartilage repair in osteochondral defects treated with different scaffolds seeded with allogenic chondrocytes. Scaffolds consisting of 55 wt% poly(ethylene oxide terephthalate) and 45 wt% poly(butylene terephthalate) (PEOT/PBT) with different pore sizes and interconnectivities were made, using a compression moulding (CM) and a three‐dimensional fibre (3DF) deposition technique. In these scaffolds, allogenic chondrocytes were seeded, cultured for 3 weeks and implanted in osteochondral defects of skeletally mature rabbits. At 3 weeks no difference in cartilage repair between an empty osteochondral defect, CM or 3DF scaffolds was found. Three months post‐implantation, cartilage repair was significantly improved after implantation of a 3DF scaffold compared to a CM scaffold. Although not significant, Mankin scores for osteoarthritis (OA) indicated less OA in the 3DF scaffold group compared to empty defects and CM‐treated defects. It is concluded that scaffold pore size and pore interconnectivity influences osteochondral repair and a decreased pore interconnectivity seems to impair osteochondral repair. Copyright © 2012 John Wiley & Sons, Ltd.     

自体脂肪间充质干细胞复合人脐带Wharton胶支架修复兔膝关节软骨缺损

背景:脐带Wharton胶富含透明质酸,糖胺多糖及胶原等,成分与天然软骨细胞外基质类似,因此由人脐带提取的Wharton胶很可能是一种较为理想的软骨组织工程支架材料。目的:评价自体脂肪间充质干细胞复合人脐带Wharton胶支架修复兔膝关节软骨缺损的效果。方法:将终浓度为1010L-1、成软骨方向诱导后的兔自体脂肪间充质干细胞与人脐带Wharton胶支架复合,继续培养1周构建组织工程软骨,对兔膝关节全层软骨缺损进行修复(实验组),并与单纯支架修复的对照组及空白组进行比较。术后3个月对修复组织行大体观察、组织学检测、糖胺多糖、总胶原定量检测及生物力学测定。结果与结论:实验组的缺损多为透明软骨修复,对照组以纤维组织修复为主,空白组无明显组织修复。提示脂肪间充质干细胞作为软骨组织工程种子细胞具有可行性;实验构建的组织工程软骨能有效的修复关节软骨缺损,人脐带Wharton胶可作为软骨组织工程良好的支架材料。     

丝素蛋白/羟基磷灰石材料复合骨髓间充质干细胞构建组织工程化软骨

背景：随着组织工程的兴起,软骨损伤的修复可能性显著地提高,但单一的支架材料均不能符合理想支架,有一定的局限性。目的：观察骨髓间充质干细胞复合丝素蛋白/羟基磷灰石构建组织工程化软骨的可行性。方法：体外分离培养骨髓间充质干细胞,并定向诱导成软骨细胞,与丝素蛋白/羟基磷灰石复合培养,构建膝关节胫骨平台全层关节软骨缺损。54只大白兔单侧膝关节全层软骨缺损模型后随机抽签法分为3组,复合组植入细胞-丝素蛋白/羟基磷灰石复合物;材料组植入单纯丝素蛋白/羟基磷灰石,对照组不行任何植入。植入后8,12周CT检查及组织学检查观察软骨缺损修复情况。结果与结论：植入后8周,复合组关节面不平整,关节间隙增大,形成新生类软骨细胞,基质丰富。材料组关节面塌陷,软骨细胞少量增殖。植入后12周,复合组关节面平整,关节间隙如常。大量软骨细胞出现,与周边软骨色泽一样,支架材料完全降解。材料组关节面不平整,软骨细胞不完全充填,支架材料部分降解。对照组未见修复。提示用骨髓间充质干细胞复合丝素蛋白/羟基磷灰石可形成透明软骨修复动物膝关节全层软骨缺损,显示了丝素蛋白/羟基磷灰石材料作为关节软骨组织工程支架材料的良好生物相容性。     

Platelet‐derived growth factor BB gene‐released scaffolds: biosynthesis and characterization

Tissue engineering generally requires three basic elements; stem/progenitor cells, inductive agents and a biomaterial scaffold; the latter is one of the key components which directly influences cellular activity and matrix formation. Commonly used scaffolds to repair defects in general do not induce stem cell recruitment, which is an essential element to tissue regeneration. In this study, fabrication of a scaffold which is capable of restoring damaged tissue through the recruitment of mesenchymal stem cells (MSCs) by gene therapy of the gene encoding platelet‐derived growth factor‐B (PDGF‐B) was investigated. PDGF‐B adenovirus (AdPDGF) was combined into novel mesoporous bioglass–silk fibrin scaffolds, which were characterized for their controlled release and sustained bioactivity. Our results demonstrate that these scaffolds can release PDGF‐B adenovirus for up to 3 weeks and increase MSC recruitment, both in vitro and following subcutaneous implantation in mice. Osseous calvarial defects in mice further demonstrate the ability of these scaffolds to enhance tissue regeneration through stem cell homing. This study demonstrates the potent ability of host stem cells to regenerate tissue defects through recruitment of MSCs via gene therapy. Copyright © 2013 John Wiley & Sons, Ltd.     

不同生物材料复合支架对关节软骨缺损的修复评价

背景:不同生物材料制备的复合软骨支架其修复软骨缺损也各具特点.目的:探讨不同生物材料制备复合支架的组织工程学特性及其修复关节软骨缺损的性能评价.方法:以"软骨组织工程,生物材料,工程软骨,复合支架"为中文关键词,以"tissue enginneering,articular cartilage,scaffold material"为英文关键词,采用计算机检索中国期刊全文数据库、PubMed数据库(1993-01/2010-11)相关文章.纳入复合支架材料-细胞复合物修复关节软骨损伤等相关的文章,排除重复研究或Meta分析类文章.结果与结论:复合支架是当前软骨组织工程中应用较多的支架,它是将具有互补特征的生物相容性可降解支架,按一定比例和方式组合,设计出结构与性能优化的复合支架.较单一支架材料具有更好的生物相容性和一定强度的韧性,较好的孔隙和机械强度.复合支架的制备不仅包括同一类生物材料的复合,还包括不同类别生物材料之间的交叉复合.可分为纯天然支架材料、纯人工支架材料以及天然与人工支架材料的复合等3类.复合支架使生物材料具有互补特性,一定程度上满足了理想生物材料支架应具的综合特点,但目前很多研究仍处于实验阶段,还有一些问题有待于解决,如不同材料的复合比例、复合工艺等.     

In situ handheld three‐dimensional bioprinting for cartilage regeneration

Articular cartilage injuries experienced at an early age can lead to the development of osteoarthritis later in life. In situ three‐dimensional (3D) printing is an exciting and innovative biofabrication technology that enables the surgeon to deliver tissue‐engineering techniques at the time and location of need. We have created a hand‐held 3D printing device (biopen) that allows the simultaneous coaxial extrusion of bioscaffold and cultured cells directly into the cartilage defect in vivo in a single‐session surgery. This pilot study assessed the ability of the biopen to repair a full‐thickness chondral defect and the early outcomes in cartilage regeneration, and compared these results with other treatments in a large animal model. A standardized critical‐sized full‐thickness chondral defect was created in the weight‐bearing surface of the lateral and medial condyles of both femurs of six sheep. Each defect was treated with one of the following treatments: (i) hand‐held in situ 3D printed bioscaffold using the biopen (HH group), (ii) preconstructed bench‐based printed bioscaffolds (BB group), (iii) microfractures (MF group) or (iv) untreated (control, C group). At 8 weeks after surgery, macroscopic, microscopic and biomechanical tests were performed. Surgical 3D bioprinting was performed in all animals without any intra‐ or postoperative complication. The HH biopen allowed early cartilage regeneration. The results of this study show that real‐time, in vivo bioprinting with cells and scaffold is a feasible means of delivering a regenerative medicine strategy in a large animal model to regenerate articular cartilage.     

Cell factory‐derived bioactive molecules with polymeric cryogel scaffold enhance the repair of subchondral cartilage defect in rabbits

We have explored the potential of cell factory‐derived bioactive molecules, isolated from conditioned media of primary goat chondrocytes, for the repair of subchondral cartilage defects. Enzyme‐linked immunosorbent assay (ELISA) confirms the presence of transforming growth factor‐β1 in an isolated protein fraction (12.56 ± 1.15 ng/mg protein fraction). These bioactive molecules were used alone or with chitosan–agarose–gelatin cryogel scaffolds, with and without chondrocytes, to check whether combined approaches further enhance cartilage repair. To evaluate this, an in vivo study was conducted on New Zealand rabbits in which a subchondral defect (4.5 mm wide × 4.5 mm deep) was surgically created. Starting after the operation, bioactive molecules were injected at the defect site at regular intervals of 14 days. Histopathological analysis showed that rabbits treated with bioactive molecules alone had cartilage regeneration after 4 weeks. However, rabbits treated with bioactive molecules along with scaffolds, with or without cells, showed cartilage formation after 3 weeks; 6 weeks after surgery, the cartilage regenerated in rabbits treated with either bioactive molecules alone or in combinations showed morphological similarities to native cartilage. No systemic cytotoxicity or inflammatory response was induced by any of the treatments. Further, ELISA was done to determine systemic toxicity, which showed no difference in concentration of tumour necrosis factor‐α in blood serum, before or after surgery. In conclusion, intra‐articular injection with bioactive molecules alone may be used for the repair of subchondral cartilage defects, and bioactive molecules along with chondrocyte‐seeded scaffolds further enhance the repair. Copyright © 2015 John Wiley & Sons, Ltd.     

Asymmetrical seeding of MSCs into fibrin–poly(ester‐urethane) scaffolds and its effect on mechanically induced chondrogenesis

Mesenchymal stem cells (MSCs) are currently being investigated as candidate cells for regenerative medicine approaches for the repair of damaged articular cartilage. For these cells to be used clinically, it is important to understand how they will react to the complex loading environment of a joint in vivo. In addition to investigating alternative cell sources, it is also important for the structure of tissue‐engineered constructs and the organization of cells within them to be developed and, if possible, improved. A custom built bioreactor was used to expose human MSCs to a combination of shear and compression loading. The MSCs were either evenly distributed throughout fibrin‐poly(ester‐urethane) scaffolds or asymmetrically seeded with a small proportion seeded on the surface of the scaffold. The effect of cell distribution on the production and deposition of cartilage‐like matrix in response to mechanical load mimicking in vivo joint loading was then investigated. The results show that asymmetrically seeding the scaffold led to markedly improved tissue development based on histologically detectable matrix deposition. Consideration of cell location, therefore, is an important aspect in the development of regenerative medicine approaches for cartilage repair. This is particularly relevant when considering the natural biomechanical environment of the joint in vivo and patient rehabilitation protocols. © 2016 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.     

不同生物材料复合支架对关节软骨缺损的修复评价

背景：不同生物材料制备的复合软骨支架其修复软骨缺损也各具特点。目的：探讨不同生物材料制备复合支架的组织工程学特性及其修复关节软骨缺损的性能评价。方法：以＂软骨组织工程,生物材料,工程软骨,复合支架＂为中文关键词,以＂tissue enginneering,articular cartilage,scaffold material＂为英文关键词,采用计算机检索中国期刊全文数据库、PubMed数据库（1993-01/2010-11）相关文章。纳入复合支架材料-细胞复合物修复关节软骨损伤等相关的文章,排除重复研究或Meta分析类文章。结果与结论：复合支架是当前软骨组织工程中应用较多的支架,它是将具有互补特征的生物相容性可降解支架,按一定比例和方式组合,设计出结构与性能优化的复合支架。较单一支架材料具有更好的生物相容性和一定强度的韧性,较好的孔隙和机械强度。复合支架的制备不仅包括同一类生物材料的复合,还包括不同类别生物材料之间的交叉复合。可分为纯天然支架材料、纯人工支架材料以及天然与人工支架材料的复合等3类。复合支架使生物材料具有互补特性,一定程度上满足了理想生物材料支架应具的综合特点,但目前很多研究仍处于实验阶段,还有一些问题有待于解决,如不同材料的复合比例、复合工艺等。     

Evidence of innervation following extracellular matrix scaffold‐mediated remodelling of muscular tissues

Naturally occurring porcine‐derived extracellular matrix (ECM) has successfully been used as a biological scaffold material for site‐specific reconstruction of a wide variety of tissues. The site‐specific remodelling process includes rapid degradation of the scaffold, with concomitant recruitment of mononuclear, endothelial and bone marrow‐derived cells, and can lead to the formation of functional skeletal and smooth muscle tissue. However, the temporal and spatial patterns of innervation of the remodelling scaffold material in muscular tissues are not well understood. A retrospective study was conducted to investigate the presence of nervous tissue in a rat model of abdominal wall reconstruction and a canine model of oesophageal reconstruction in which ECM scaffolds were used as inductive scaffolds. Evidence of mature nerve, immature nerve and Schwann cells was found within the remodelled ECM at 28 days in the rat body wall model, and at 91 days post surgery in a canine model of oesophageal repair. Additionally, a microscopic and morphological study that investigated the response of primary cultured neurons seeded upon an ECM scaffold showed that neuronal survival and outgrowth were supported by the ECM substrate. Finally, matricryptic peptides resulting from rapid degradation of the ECM scaffold induced migration of terminal Schwann cells in a concentration‐dependent fashion in vitro. The findings of this study suggest that the reconstruction of tissues in which innervation is an important functional component is possible with the use of biological scaffolds composed of extracellular matrix. Copyright © 2009 John Wiley & Sons, Ltd.     

Stem cells display a donor dependent response to escalating levels of growth factor release from extracellular matrix‐derived scaffolds

Numerous growth factor delivery systems have been developed for tissue engineering. However, little is known about how the dose of a specific protein will influence tissue regeneration, or how different patients will respond to altered levels of growth factor presentation. The objective of the present study was to assess stem cell chondrogenesis within extracellular‐matrix (ECM)‐derived scaffolds loaded with escalating levels of transforming growth factor (TGF)‐β3. It was also sought to determine if stem cells display a donor‐dependent response to different doses of TGF‐β3, from low (5 ng) to high (200 ng), released from such scaffolds. It was found that ECM‐derived scaffolds possess the capacity to bind and release increasing amounts of TGF‐β3, with between 60% and 75% of this growth factor released into the media over the first 12 days of culture. After seeding these scaffolds with human infrapatellar fat pad‐derived stem cells (FPSCs), it was found that cartilage‐specific ECM accumulation was greatest for the higher levels of growth factor loading. Importantly, soak‐loading cartilage ECM‐derived scaffolds with high levels of TGF‐β3 always resulted in at least comparable levels of chondrogenesis to controls where this growth factor was continuously added to the culture media. Similar results were observed for FPSCs from all donors, although the absolute level of secreted matrix did vary from donor to donor. Therefore, while no single growth factor release profile will be optimal for all patients, the results of this study suggest that the combination of a highly porous cartilage ECM‐derived scaffold coupled with appropriate levels of TGF‐β3 can consistently drive chondrogenesis of adult stem cells. Copyright © 2016 John Wiley & Sons, Ltd.     

Investigating cellulose derived glycosaminoglycan mimetic scaffolds for cartilage tissue engineering applications

Articular cartilage has a limited capacity to heal and, currently, no treatment exists that can restore normal hyaline cartilage. Creating tissue engineering scaffolds that more closely mimic the native extracellular matrix may be an attractive approach. Glycosaminoglycans, which are present in native cartilage tissue, provide signalling and structural cues to cells. This study evaluated the use of a glycosaminoglycan mimetic, derived from cellulose, as a potential scaffold for cartilage repair applications. Fully sulfated sodium cellulose sulfate (NaCS) was initially evaluated in soluble form as an additive to cell culture media. Human mesenchymal stem cell (MSC) chondrogenesis in pellet culture was enhanced with 0.01% NaCS added to induction media as demonstrated by significantly higher gene expression for type II collagen and aggrecan. NaCS was combined with gelatine to form fibrous scaffolds using the electrospinning technique. Scaffolds were characterized for fibre morphology, overall hydrolytic stability, protein/growth factor interaction and for supporting MSC chondrogenesis in vitro. Scaffolds immersed in phosphate buffered saline for up to 56 days had no changes in swelling and no dissolution of NaCS as compared to day 0. Increasing concentrations of the model protein lysozyme and transforming growth factor‐β3 were detected on scaffolds with increasing concentrations of NaCS (p < 0.05). MSC chondrogenesis was enhanced on the scaffold with the lowest NaCS concentration as seen with the highest collagen type II production, collagen type II immunostaining, and expression of cartilage‐specific genes. These studies demonstrate the feasibility of cellulose sulfate as a scaffolding material for cartilage tissue engineering. Copyright © 2016 John Wiley & Sons, Ltd.