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.     

Matrilin‐3 codelivery with adipose‐derived mesenchymal stem cells promotes articular cartilage regeneration in a rat osteochondral defect model

Matrilin‐3 is an essential extracellular matrix component present only in cartilaginous tissues. Matrilin‐3 exerts chondroprotective effects by regulating an anti‐inflammatory function and extracellular matrix components. We hypothesized that the codelivery of matrilin‐3 with infrapatellar adipose‐tissue‐derived mesenchymal stem cells (Ad‐MSCs) may enhance articular cartilage regeneration. Matrilin‐3 treatment of Ad‐MSCs in serum‐free media induced collagen II and aggrecan expression, and matrilin‐3 in chondrogenic media also enhanced in vitro chondrogenic differentiation. Next, the in vivo effect of matrilin‐3 codelivery with Ad‐MSCs on cartilage regeneration was assessed in an osteochondral defect model in Sprague Dawley rats: Ad‐MSCs and hyaluronic acid were implanted at the defect site with or without matrilin‐3 (140, 280, and 700 ng). Safranin O staining revealed that matrilin‐3 (140 and 280 ng) treatment significantly improved cartilage regeneration and glycosaminoglycan accumulation. In the animals treated with 140‐ng matrilin‐3, in particular, the defect site exhibited complete integration with surrounding tissue and a smooth glistening surface. The International Cartilage Repair Society macroscopic and O'Driscoll microscopic scores for regenerated cartilage were furthermore shown to be considerably higher for this group (matrilin‐3; 140 ng) compared with the other groups. Furthermore, the defects treated with 140‐ng matrilin‐3 revealed significant hyaline‐like cartilage regeneration in the osteochondral defect model; in contrast, the defects treated with 700‐ng matrilin‐3 exhibited drastically reduced cartilage regeneration with mixed hyaline–fibrocartilage morphology. Codelivery of matrilin‐3 with Ad‐MSCs significantly influenced articular cartilage regeneration, supporting the potential use of this tissue‐specific protein for a cartilage‐targeted stem cell therapy.     

Application of marrow mesenchymal stem cell‐derived extracellular matrix in peripheral nerve tissue engineering

To advance molecular and cellular therapy into the clinic for peripheral nerve injury, modification of neural scaffolds with the extracellular matrix (ECM) of peripheral nerves has been established as a promising alternative to direct inclusion of support cells and/or growth factors within a neural scaffold, while cell‐derived ECM proves to be superior to tissue‐derived ECM in the modification of neural scaffolds. Based on the fact that bone marrow mesenchymal stem cells (BMSCs), just like Schwann cells, are adopted as support cells within a neural scaffold, in this study we used BMSCs as parent cells to generate ECM for application in peripheral nerve tissue engineering. A chitosan nerve guidance conduit (NGC) and silk fibroin filamentous fillers were respectively prepared for co‐culture with purified BMSCs, followed by decellularization to stimulate ECM deposition. The ECM‐modified NGC and lumen fillers were then assembled into a chitosan–silk fibroin‐based, BMSC‐derived, ECM‐modified neural scaffold, which was implanted into rats to bridge a 10 mm‐long sciatic nerve gap. Histological and functional assessments after implantation showed that regenerative outcomes achieved by our engineered neural scaffold were better than those achieved by a plain chitosan–silk fibroin scaffold, and suggested the benefits of BMSC‐derived ECM for peripheral nerve repair. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of resveratrol on enrichment of adipose‐derived stem cells and their differentiation to osteoblasts in two‐and three‐dimensional cultures

The goal of this study was to develop a method for increasing the yield of multipotent adipose‐derived mesenchymal stem cells (ASCs) and osteoprogenitor cells (OPCs) from subcutaneous fat. After removing mature adipocytes and haematopoietic cells from rat inguinal fat, ASCs in the remaining cell population were verified by their attachment to plastic, surface marker profile (CD271⁺, CD73⁺ and CD45^–) and ability to differentiate into adipocytes, chondrocytes and osteoblasts. OPCs were defined as E11⁺ and OCN⁺. Adherent cells were cultured in growth medium (GM) or osteogenic medium (OM) and treated with resveratrol (0, 12.5, and 25 µ m ) for 7 days; ASCs and OPCs were assessed by flow cytometry. Osteogenic potential was determined in two‐dimensional (2D) cultures as a function of alkaline phosphatase‐specific activity and osteocalcin production. In addition, cells were seeded onto three‐dimensional (3D) poly‐ε‐caprolactone scaffolds and cultured under dynamic conditions; mineralization was quantified by micro‐CT at 4, 8 and 12 weeks. Resveratrol increased the percentage of ASCs in the population (population%) and number of ASCs in both GM and OM, but increased only the number of OPCs in GM. In both media types resveratrol increased alkaline phosphatase activity and osteocalcin levels. In 3D cultures, resveratrol‐treated cells significantly increased mineralized matrix volume at early time points. Resveratrol exerted a biphasic effect on adherent cells by enriching the ASC and OPC populations and enhancing osteogenic differentiation. Resveratrol pretreatment induced more mineralization at earlier time points and represents a clinically viable technique for orthopaedic and dental applications for autologous stem cell therapy. Copyright © 2012 John Wiley & Sons, Ltd.     

Development of decellularized scaffolds for stem cell‐driven tissue engineering

Organ transplantation is an effective treatment for chronic organ dysfunctioning conditions. However, a dearth of available donor organs for transplantation leads to the death of numerous patients waiting for a suitable organ donor. The potential of decellularized scaffolds, derived from native tissues or organs in the form of scaffolds has been evolved as a promising approach in tissue‐regenerative medicine for translating functional organ replacements. In recent years, donor organs, such as heart, liver, lung and kidneys, have been reported to provide acellular extracellular matrix (ECM)‐based scaffolds through the process called ‘decellularization’ and proved to show the potential of recellularization with selected cell populations, particularly with stem cells. In fact, decellularized stem cell matrix (DSCM) has also emerged as a potent biological scaffold for controlling stem cell fate and function during tissue organization. Despite the proven potential of decellularized scaffolds in tissue engineering, the molecular mechanism responsible for stem cell interactions with decellularized scaffolds is still unclear. Stem cells interact with, and respond to, various signals/cues emanating from their ECM. The ability to harness the regenerative potential of stem cells via decellularized ECM‐based scaffolds has promising implications for tissue‐regenerative medicine. Keeping these points in view, this article reviews the current status of decellularized scaffolds for stem cells, with particular focus on: (a) concept and various methods of decellularization; (b) interaction of stem cells with decellularized scaffolds; (c) current recellularization strategies, with associated challenges; and (iv) applications of the decellularized scaffolds in stem cell‐driven tissue engineering and regenerative medicine. Copyright © 2015 John Wiley & Sons, Ltd.     

Three‐dimensional printed polycaprolactone‐based scaffolds provide an advantageous environment for osteogenic differentiation of human adipose‐derived stem cells

The capacity of bone grafts to repair critical size defects can be greatly enhanced by the delivery of mesenchymal stem cells (MSCs). Adipose tissue is considered the most effective source of MSCs (ADSCs); however, the efficiency of bone regeneration using undifferentiated ADSCs is low. Therefore, this study proposes scaffolds based on polycaprolactone (PCL), which is widely considered a suitable MSC delivery system, were used as a three‐dimensional (3D) culture environment promoting osteogenic differentiation of ADSCs. PCL scaffolds enriched with 5% tricalcium phosphate (TCP) were used. Human ADSCs were cultured in osteogenic medium both on the scaffolds and in 2D culture. Cell viability and osteogenic differentiation were tested at various time points for 42 days. The expression of RUNX2, collagen I, alkaline phosphatase, osteonectin and osteocalcin, measured by real‐time polymerase chain reaction was significantly upregulated in 3D culture. Production of osteocalcin, a specific marker of terminally differentiated osteoblasts, was significantly higher in 3D cultures than in 2D cultures, as confirmed by western blot and immunostaining, and accompanied by earlier and enhanced mineralization. Subcutaneous implantation into immunodeficient mice was used for in vivo observations. Immunohistological and micro‐computed tomography analysis revealed ADSC survival and activity toward extracellular production after 4 and 12 weeks, although heterotopic osteogenesis was not confirmed – probably resulting from insufficient availability of Ca/P ions. Additionally, TCP did not contribute to the upregulation of differentiation on the scaffolds in culture, and we postulate that the 3D architecture is a critical factor and provides a useful environment for prior‐to‐implantation osteogenic differentiation of ADSCs. Copyright © 2016 John Wiley & Sons, Ltd.     

Targeted delivery of adipose‐derived stem cells via acellular dermal matrix enhances wound repair in diabetic rats

Cell‐based therapeutic intervention has emerged as a new approach to accelerate wound closure. Adipose‐derived stem cells (ASCs), as a fascinating cell source, have received much attention in tissue repair and regeneration. In this study we evaluated the potential of acellular dermal matrix (ADM) scaffold serving as a carrier for the delivery of ASCs and investigated its therapeutic effects on wound healing. First, ASCs were isolated and characterized for multidifferentiation potential. ASCs–ADM grafts were then prepared, and ADM scaffold was shown to support the in vitro growth and proliferation of ASCs. Next, we analysed paracrine factors in conditioned medium and found that ASCs–ADM grafts secreted various cytokines, including VEGF, HGF, TGFβ and bFGF. Moreover, ASCs–ADM conditioned medium notably stimulated the migration and proliferation of fibroblasts. In vivo, we established an excisional wound model in diabetic rats which received phosphate‐buffered saline (PBS), ADM or ASCs–ADM grafts, respectively. Our results demonstrated that implantation of ASCs–ADM significantly enhanced tissue regeneration and increased epithelialization, resulting in accelerated wound closure. Immunofluorescence analysis further indicated that capillary density was evidently increased in the ASCs–ADM group compared with the control or ADM group. In addition, western blot analysis showed that ASCs–ADM significantly increased the expression of angiogenic factors, which was consistent with in vitro data. Taken together, our results suggest that targeted delivery of ASCs via ADM scaffold accelerate diabetic wound healing through a paracrine mechanism, with enhanced granulation tissue formation and increased re‐epithelialization and neovascularization. Copyright © 2012 John Wiley & Sons, Ltd.     

Matrix‐directed differentiation of human adipose‐derived mesenchymal stem cells to dermal‐like fibroblasts that produce extracellular matrix

Commercially available skin substitutes lack essential non‐immune cells for adequate tissue regeneration of non‐healing wounds. A tissue‐engineered, patient‐specific, dermal substitute could be an attractive option for regenerating chronic wounds, for which adipose‐derived mesenchymal stem cells (ADMSCs) could become an autologous source. However, ADMSCs are multipotent in nature and may differentiate into adipocytes, osteocytes and chondrocytes in vitro, and may develop into undesirable tissues upon transplantation. Therefore, ADMSCs committed to the fibroblast lineage could be a better option for in vitro or in vivo skin tissue engineering. The objective of this study was to standardize in vitro culture conditions for ADMSCs differentiation into dermal‐like fibroblasts which can synthesize extracellular matrix (ECM) proteins. Biomimetic matrix composite, deposited on tissue culture polystyrene (TCPS), and differentiation medium (DM), supplemented with fibroblast‐conditioned medium and growth factors, were used as a fibroblast‐specific niche (FSN) for cell culture. For controls, ADMSCs were cultured on bare TCPS with either DM or basal medium (BM). Culture of ADMSCs on FSN upregulated the expression of differentiation markers such as fibroblast‐specific protein‐1 (FSP‐1) and a panel of ECM molecules specific to the dermis, such as fibrillin‐1, collagen I, collagen IV and elastin. Immunostaining showed the deposition of dermal‐specific ECM, which was significantly higher in FSN compared to control. Fibroblasts derived from ADMSCs can synthesize elastin, which is an added advantage for successful skin tissue engineering as compared to fibroblasts from skin biopsy. To obtain rapid differentiation of ADMSCs to dermal‐like fibroblasts for regenerative medicine, a matrix‐directed differentiation strategy may be employed. Copyright © 2014 John Wiley & Sons, Ltd.     

Form and functional repair of long bone using 3D‐printed bioactive scaffolds

Injuries to the extremities often require resection of necrotic hard tissue. For large‐bone defects, autogenous bone grafting is ideal but, similar to all grafting procedures, is subject to limitations. Synthetic biomaterial‐driven engineered healing offers an alternative approach. This work focuses on three‐dimensional (3D) printing technology of solid‐free form fabrication, more specifically robocasting/direct write. The research hypothesizes that a bioactive calcium‐phosphate scaffold may successfully regenerate extensive bony defects in vivo and that newly regenerated bone will demonstrate mechanical properties similar to native bone as healing time elapses. Robocasting technology was used in designing and printing customizable scaffolds, composed of 100% beta tri‐calcium phosphate (β‐TCP), which were used to repair critical sized long‐bone defects. Following full thickness segmental defects (~11 mm × full thickness) in the radial diaphysis in New Zealand white rabbits, a custom 3D‐printed, 100% β‐TCP, scaffold was implanted or left empty (negative control) and allowed to heal over 8, 12, and 24 weeks. Scaffolds and bone, en bloc, were subjected to micro‐CT and histological analysis for quantification of bone, scaffold and soft tissue expressed as a function of volume percentage. Additionally, biomechanical testing at two different regions, (a) bone in the scaffold and (b) in native radial bone (control), was conducted to assess the newly regenerated bone for reduced elastic modulus (E_r) and hardness (H) using nanoindentation. Histological analysis showed no signs of any adverse immune response while revealing progressive remodelling of bone within the scaffold along with gradual decrease in 3D‐scaffold volume over time. Micro‐CT images indicated directional bone ingrowth, with an increase in bone formation over time. Reduced elastic modulus (E_r) data for the newly regenerated bone presented statistically homogenous values analogous to native bone at the three time points, whereas hardness (H) values were equivalent to the native radial bone only at 24 weeks. The negative control samples showed limited healing at 8 weeks. Custom engineered β‐TCP scaffolds are biocompatible, resorbable, and can directionally regenerate and remodel bone in a segmental long‐bone defect in a rabbit model. Custom designs and fabrication of β‐TCP scaffolds for use in other bone defect models warrant further investigation.     

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.     

New insights into epithelial differentiation of human adipose‐derived stem cells

Although many studies using stem cells as therapeutic agents after renal failure have been published in recent years, our knowledge of the factors involved and the cellular mechanisms underlying their beneficial effect on organ regeneration is incomplete. A growing insight into these interactions would help to utilize the biological potential of stem cells for therapeutic approaches. It is here hypothesized that soluble factors released by tubular epithelial cells (TECs) induce epithelial differentiation in adipose‐derived adult mesenchymal stem cells (ASCs). ASCs were therefore cultured in conditioned medium (CM) derived from TECs and the changes in expression genes towards an epithelial pattern were determined by microarray and qPCR analyses. The changes in gene expression were evaluated using Affymetrix HG‐U133 Plus 2.0 arrays. Microarray‐based screening revealed 117 genes differentially expressed in a significant manner after short‐time incubation (3 days) of ASCs with CM, and four of these were solute carriers (SLCs). Changes in mRNA expression of these SLCs were verified by qPCR at several time points, additionally with four stem cell factors and five epithelial markers. qPCR analyses showed that expression of three of the SLCs rose significantly, whereas three of the four stem cell markers analysed decreased during 7 days of CM incubation. Moreover, a robust expression of three characteristic epithelial markers (cytokeratin 18, ZO‐1 and ZO‐2) was observed after 17 days. These changes in the expression patterns strongly indicate differentiation towards the epithelial lineage. The capability of ASCs to differentiate into epithelial cells may be important in organ repair mechanisms. Copyright © 2011 John Wiley & Sons, Ltd.     

How chondrogenic are human umbilical cord matrix cells? A comparison to adipose‐derived stem cells

The umbilical cord matrix as well as liposuction material have been demonstrated to contain cells capable of differentiating towards the mesodermal lineage. High availability and low donor site morbidity appear promising for the use of human umbilical cord matrix cells (HUCMs) and adipose‐derived stem cells (ASCs) in cell‐based therapies. In the present study we focused on cartilage regeneration and compared HUCMs and ASCs regarding their potential to differentiate towards the chondrogenic lineage. Cells were isolated by explantation culture or enzymatic digestion, phenotypically characterized by flow cytometry and differentiated as 3D micromass pellets for up to 35 days. Under tested conditions, ASCs demonstrated significantly higher glycosaminoglycan synthesis compared to HUCMs. qRT–PCR data gave evidence that chondrogenic genes are expressed by both ASCs and HUCMs. However, higher expression levels of ASCs suggest that this cell type has higher potential for differentiation towards a cartilage‐like phenotype than HUCMs. In conclusion, both cell types, HUCMs and ASCs, are easily available, possess typical properties of mesenchymal stem cells and are thus promising for cell‐based therapies. However, in terms of cartilage regeneration, ASCs might be more suitable than HUCMs. Copyright © 2009 John Wiley & Sons, Ltd.     

Mesenchymal cell transfer for articular cartilage repair

Mature articular cartilage has a poor reparative response to injury and its irreparable breakdown is the common feature of degenerative joint diseases. If articular cartilage lesions become symptomatic, the orthopaedic surgeon must decide on a treatment option. The treatment options include conversion of chondral lesions to osteochondral lesions, which facilitates migration of cells from the marrow space to effect repair. In recent years, a greater emphasis has been placed on tissue engineering strategies and thus several new treatment options have been introduced, including the use of cell transplantation. Several tissue sources and cell types can potentially be used for this type of therapy. These include autologous or allograft chondrocytes and mesenchymal progenitor cells from various tissues. These cells may be delivered to articular cartilage lesions by a variety of methods including direct cell injection to the lesion or seeding in a biodegradable scaffold prior to implantation. In this review, the potential of cell transplantation for articular cartilage repair and regeneration will be discussed. The authors will focus on the available technologies and the present limitations of cell-based therapies.     

In vivo construction of liver tissue by implantation of a hepatic non‐parenchymal/adipose‐derived stem cell sheet

Subcutaneous hepatocyte sheet implantation is an attractive therapeutic option for various liver diseases. However, this technique is limited by the availability of hepatocytes. Thus, the use of hepatic non‐parenchymal cells (NPCs) containing small hepatocytes, which have the ability to proliferate more rapidly than mature hepatocytes, for transplantation has been suggested. The aim of our study was to construct liver tissue subcutaneously in rats by implanting NPC sheets co‐cultivated with adipose‐derived stem cells (ADSCs), which produce certain angiogenic factors. We crafted NPC‐ADSC sheets on temperature‐responsive culture dishes. NPCs formed functioning bile canaliculi and stored glycogen. In addition, their ability to produce albumin was not inferior to that of hepatocytes. Albumin production increased over time when co‐cultivated with ADSCs. We then implanted the co‐cultivated cell sheets subcutaneously. The co‐cultivated sheets retained glycogen, formed bile canaliculi, showed signs of vascularization and survived subcutaneously without pre‐vascularization. These results suggest that NPCs can be a viable option in cell therapy for liver diseases. This technique using co‐cultivated cell sheets may be useful in the field of regenerative medicine. Copyright © 2017 John Wiley & Sons, Ltd.     

Adipose tissue engineering using adipose‐derived stem cells enclosed within an injectable carboxymethylcellulose‐based hydrogel

In situ gelation of an aqueous solution of carboxymethylcellulose derivative bearing phenolic hydroxyl groups (CMC‐Ph) that contained suspended adipose‐derived stem cells (ASCs) was studied in vitro and in vivo for evaluating feasibility in adipose tissue‐engineering strategies. The rat ASCs that were enclosed in the CMC‐Ph gels through a horseradish peroxidase‐catalysed reaction showed 92.8% viability, good proliferation and adipogenic differentiation in vitro. Ten weeks after the subcutaneous injection of ASCs‐suspending CMC‐Ph for in situ gelation, clearly visible new vascularized adipose tissue formed at the injection site. The number of blood vessels and the area occupied by adipose tissues were five and eight times larger, respectively, than those found in the implanted acellular gel. The adipogenesis and neovascularization were further enhanced by incorporation of fibroblast growth factor into the CMC‐Ph gel containing ASCs. Copyright © 2012 John Wiley & Sons, Ltd.     

间充质干细胞体内迁移研究进展

间充质干细胞（MSC）具有低免疫源性、多向分化、强大的支持造血和免疫调节功能,同时具有来源广泛,易于体外分离和扩增的特点,目前广泛应用于临床疾病的治疗。研究资料表明,MSC输注后广泛分布于受者各组织器官,然而MSC体内靶向迁移是达到临床治疗的高效性和安全性的关键所在,本文对静脉输注后MSC的体内分布特点和增强MSC体内靶向迁移策略研究的新进展作一综述。     

In vitro evaluation of gel‐encapsulated adipose derived stem cells: Biochemical cues for in vivo peripheral nerve repair

Adipose‐derived stem cells (ASC) are becoming one of the most exploited cells in peripheral nerve repair. They are fast‐growing and able to protect neurons from apoptosis; they can reduce post‐injury latency and the risk of muscle atrophy. This study evaluates laminin‐loaded fibrin gel as an ASC‐carrying scaffold for nerve repair. In vitro, ASC retained their proliferative activity but showed significant increase in proliferation rate when encapsulated in gels with low laminin concentrations (i.e., 1 μg/mL). We observed a linear decrease of ASC proliferation rate with increasing laminin concentration from 1 to 100 μg/mL. We next examined the effect of the ASC‐carrying fibrin gels on in vitro dorsal root ganglia (DRG) neurite extension, then in vivo sciatic nerve regeneration in adult rats. The ASC‐carrying gel was embedded in 15‐mm‐long, 1.5‐mm‐diameter polydimethylsiloxane regenerative conduits for in vivo evaluation. At 8‐week post implantation, robust regeneration was observed across the long gap. Taken together, these results suggest ASC‐carrying gels are a potential path to improve the efficacy of nerve regeneration through artificial guidance conduits and electrode nerve interfaces.     

Enhanced endothelial differentiation of adipose‐derived stem cells by substrate nanotopography

Adipose‐derived stem cells (ADSCs) have great potential as a cell source for tissue engineering and regenerative medicine because they are easier to obtain, have lower donor‐site morbidity and are available in larger numbers than stem cells harvested using bone marrow aspiration. Until now, little has been known about how nanotopography affects the proliferation and endothelial differentiation of ADSCs. In the present study, two nanograting substrates with a period (ridge and groove) of about 250 and 500 nm, respectively, were fabricated on quartz and their effect on ADSC fate was investigated. The results showed that proliferation of ADSCs on nanograting substrates decreased while cell attachment was not significantly affected compared to a flat substrate. Endothelial differentiation of ADSCs on both flat and nanograting substrates can be induced with vascular endothelial growth factor, as shown by immunofluorescent staining. Quantitative real‐time PCR analysis showed significantly enhanced upregulation of vWF, PECAM‐1 and VE‐cadherin at the gene level by ADSCs on the nanograting substrates. In vitro angiogenesis assay on Matrigel showed that nanograting substrates enhanced capillary tube formation. This study highlights the beneficial influence of nanotopography on the differentiation of ADSC into endothelial cells which play an important role in vascularization. Copyright © 2012 John Wiley & Sons, Ltd.     

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.