Long-term survival and bipotent terminal differentiation of human mesenchymal stem cells (hMSC) in combination with a commercially available three-dimensional collagen scaffold

Actuation of Soft Thermoresponsive Hydrogels Mechanically Stimulates Osteogenesis in Human Mesenchymal Stem Cells without Biochemical Factors

Mesenchymal stem cells (MSCs) have the potential to differentiate into multiple lineages and can be harvested relatively easily from adults, making them a promising cell source for regenerative therapies. While it is well-known how to consistently differentiate MSCs into adipose, chondrogenic, and osteogenic lineages by treatment with biochemical factors, the number of studies exploring how to achieve this with mechanical signals is limited. A relatively unexplored area is the effect of cyclic forces on the MSC differentiation. Recently, our group developed a thermoresponsive N-ethyl acrylamide/N-isopropylacrylamide (NIPAM/NEAM) hydrogel supplemented with gold nanorods that are able to convert near-infrared light into heat. Using light pulses allows for local hydrogel collapse and swelling with physiologically relevant force and frequency. In this study, MSCs are cultured on this hydrogel system with a patterned surface and exposed to intermittent or continuous actuation of the hydrogel for 3 days to study the effect of actuation on MSC differentiation. First, cells are harvested from the bone marrow of three donors and tested for their MSC phenotype, meeting the following criteria: the harvested cells are adherent and demonstrate a fibroblast-like bipolar morphology. They lack the expression of CD34 and CD45 but do express CD73, CD90, and CD105. Additionally, their differentiation potential into adipogenic, chondrogenic, and osteogenic lineages is validated by the addition of standardized differentiation media. Next, MSCs are exposed to intermittent or continuous actuation, which leads to a significantly enhanced cell spreading compared to nonactuated cells. Moreover, actuation results in nuclear translocation of Runt-related transcription factor 2 and the Yes-associated protein. Together, these results indicate that cyclic mechanical stimulation on a soft, ridged substrate modulates the MSC fate commitment in the direction of osteogenesis.

Biofabrication of vascularized adipose tissues and their biomedical applications

Recent advances in adipose tissue engineering and cell biology have led to the development of innovative therapeutic strategies in regenerative medicine for adipose tissue reconstruction. To date, the many in vitro and in vivo models developed for vascularized adipose tissue engineering cover a wide range of research areas, including studies with cells of various origins and types, polymeric scaffolds of natural and synthetic derivation, models presented using decellularized tissues, and scaffold-free approaches. In this review, studies on adipose tissue types with different functions, characteristics and body locations have been summarized with 3D in vitro fabrication approaches. The reason for the particular focus on vascularized adipose tissue models is that current liposuction and fat transplantation methods are unsuitable for adipose tissue reconstruction as the lack of blood vessels results in inadequate nutrient and oxygen delivery, leading to necrosis in situ. In the first part of this paper, current studies and applications of white and brown adipose tissues are presented according to the polymeric materials used, focusing on the studies which could show vasculature in vitro and after in vivo implantation, and then the research on adipose tissue fabrication and applications are explained.

Natural Polymeric Scaffolds for Tissue Engineering Applications

Natural polymeric scaffolds can be used for tissue engineering applications such as cell delivery and cell-free supporting of native tissues. This is because of their desirable properties such as; high biocompatibility, tunable mechanical strength and conductivity, large surface area, porous- and extracellular matrix (ECM)-mimicked structures. Specifically, their less toxicity and biocompatibility makes them suitable for several tissue engineering applications. For these reasons, several biopolymeric scaffolds are currently being explored for numerous tissue engineering applications. To date, research on the nature, chemistry, and properties of nanocomposite biopolymers are been reported, while the need for a comprehensive research note on more tissue engineering application of these biopolymers remains. As a result, this present study comprehensively reviews the development of common natural biopolymers as scaffolds for tissue engineering applications such as cartilage tissue engineering, cornea repairs, osteochondral defect repairs, and nerve regeneration. More so, the implications of research findings for further studies are presented, while the impact of research advances on future research and other specific recommendations are added as well.

Proliferation and Osteogenic Differentiation of hMSCs on Biomineralized Collagen

Biomineralized collagen with intrafibrillar calcium phosphate mineral provides an excellent mimic of the composition and structure of the extracellular matrix of bone, from nano- to micro-scale. Scaffolds prepared from this material have the potential to become the next-generation of synthetic bone graft substitutes, as their unique properties make them closer to the native tissue than synthetic alternatives currently available to clinicians. To understand the interaction between biomineralized collagen and cells that are relevant in the context of bone regeneration, we studied the growth and osteogenic differentiation of bone marrow derived human mesenchymal stromal cells (hMSCs) cultured on biomineralized collagen membranes, and compared it to the cell behavior on collagen membranes without mineral. Cells proliferated normally on both biomimetic membranes, and were more triggered to differentiate toward the osteogenic lineage by the biomineralized collagen. This was shown by the elevated mRNA levels of RUNX2, SPP1, ENPP1, and OCN after 3 days of culture, and COL1A1 after 14 days of culture on mineralized collagen. The mRNA levels of the tested markers of osteogenesis were lower on collagen membranes without mineral, with the exception of OCN, which was more highly expressed on collagen than on biomineralized collagen membranes. Expression by hMSCs of OPG, a gene involved in inhibition of osteoclastogenesis, was higher on biomineralized collagen at day 3, while M-CSF, involved in osteoblast-osteoclast communication, was upregulated on both membranes at day 3 and 14 of culture. Alkaline phosphatase activity of hMSCs was high on both biomimetic membranes when compared with cells cultured on tissue culture plastic. Cell-induced mineralization was observed on collagen membranes, while the high mineral content of the biomineralized membranes prohibited a reliable analysis of cell-induced mineralization on these membranes. In conclusion, we have identified that both collagen and biomineralized collagen support proliferation, osteogenic differentiation and mineralization of hMSCs, with biomineralized membranes having a more pronounced positive effect. These findings support the existing evidence that biomineralized collagen is a promising material in the field of bone regeneration.

Behaviour of human dental pulp stem cell in high glucose condition: impact on proliferation and osteogenic differentiation

OBJECTIVE

The aim of this study is to investigate the changes of human dental pulp stem cell (hDPSC) viability, proliferation and osteogenic differentiation in high glucose condition.

DESIGN

After 21 days of culture in low (5.5 mM) and high (20 mM) glucose medium, hDPSC viability and proliferation were assessed with respectively the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Hoechst assays. To investigate the influence of glucose on osteogenic differentiation hDPSCs were cultured for 28 days in low or high glucose medium with osteoinductive cocktail. Mineralization was examined by alizarin red staining/quantification and the expression of osteogenic-related genes [Runt-related transcription factor 2 (RUNX2), Osteocalcin (OCN), Collagen 1A1 (COL1A1)] analyzed by RT-qPCR.

RESULTS

We observed no significant difference (p >  0.05) on hDPSC proliferation or cell viability between low or high glucose groups. We did not highlight a significant difference after alizarin red staining and quantification between hDPSCs cultured with high or low glucose concentration in the culture medium. In the same manner, high glucose concentration did not appear to modify osteogenic gene expression: there was no significant difference in osteogenic-related gene expression between high or low glucose groups.

CONCLUSION

Proliferation, viability, and osteogenic differentiation of hDPSCs were not changed by high glucose environment.

Halloysite Nanoclay/Biopolymers Composite Materials in Tissue Engineering

Biocompatible materials for the fabrication of tissue substitutes are crucially important in the advancement of modern medicinal biotechnology. These materials, to serve their function, should be similar in physical, chemical, biological, and structural properties to native tissues which they are aimed to mimic. The porosity of artificial scaffolds is essential for normal nutrient transmission to cells, gas diffusion, and cell attachment and proliferation. Nanoscale inorganic additives and dopants are widely used to improve the functional properties of the polymer materials for tissue engineering. Among these inorganic dopants, halloysite nanotubes are arguably the most perspective candidates because of their biocompatibility and functional properties allowing to enhance significantly the mechanical and chemical stability of tissue engineering scaffolds. Here, this vibrant field of biotechnology for regenerative medicine is overviewed.

Assessment of stem cell viability in the initial healing period in rabbits with a cranial bone defect according to the type and form of scaffold

Purpose

Increased bone regeneration has been achieved through the use of stem cells in combination with graft material. However, the survival of transplanted stem cells remains a major concern. The purpose of this study was to evaluate the viability of transplanted mesenchymal stem cells (MSCs) at an early time point (24 hours) based on the type and form of the scaffold used, including type I collagen membrane and synthetic bone.

Methods

The stem cells were obtained from the periosteum of the otherwise healthy dental patients. Four symmetrical circular defects measuring 6 mm in diameter were made in New Zealand white rabbits using a trephine drill. The defects were grafted with 1) synthetic bone (β-tricalcium phosphate/hydroxyapatite [β-TCP/HA]) and 1×10⁵ MSCs, 2) collagen membrane and 1×10⁵ MSCs, 3) β-TCP/HA+collagen membrane and 1×10⁵ MSCs, or 4) β-TCP/HA, a chipped collagen membrane and 1×10⁵ MSCs. Cellular viability and the cell migration rate were analyzed.

Results

Cells were easily separated from the collagen membrane, but not from synthetic bone. The number of stem cells attached to synthetic bone in groups 1, 3, and 4 seemed to be similar. Cellular viability in group 2 was significantly higher than in the other groups (P<0.05). The cell migration rate was highest in group 2, but this difference was not statistically significant (P>0.05).

Conclusions

This study showed that stem cells can be applied when a membrane is used as a scaffold under no or minimal pressure. When space maintenance is needed, stem cells can be loaded onto synthetic bone with a chipped membrane to enhance the survival rate.

3D collagen microfibers stimulate the functionality of preadipocytes and maintain the phenotype of mature adipocytes for long term cultures

Although adipose tissue is one of the most abundant tissues of the human body, its reconstruction remains a competitive challenge. The conventional in vitro two or three-dimensional (2D or 3D) models of mature adipocytes unfortunately lead to their quick dedifferentiation after one week, and complete differentiation of adipose derived stem cells (ADSC) usually requires more than one month. In this context, we developed biomimetic 3D adipose tissues with high density collagen by mixing type I collagen microfibers with primary mouse mature adipocytes or human ADSC in transwells. These 3D-tissues ensured a better long-term maintained phenotype of unilocular mature adipocytes, compared to 2D, with a viability of 96 ± 2% at day 14 and a good perilipin immunostaining, - the protein necessary for stabilizing the fat vesicles. For comparison, in 2D culture, mature adipocytes released their fat until splitting their single adipose vesicle into several ones with significantly 4 times smaller size. Concerning ADSC, the adipogenic genes expression in 3D-tissues was found at least doubled throughout the differentiation (over 8 times higher for GLUT4 at day 21), along with it, almost 4 times larger fat vesicles were observed (10 ± 4 µm at day 14). Perilipin immunostaining and leptin secretion, the satiety protein, attested the significantly doubled better functionality of ADSC in 3D adipose tissues. These obtained long-term maintained phenotype and fast adipogenesis make this model relevant for either cosmetic/pharmaceutical assays or plastic surgery purposes. STATEMENT OF SIGNIFICANCE: Adipose tissue has important roles in our organism, providing energy from its lipids storage and secreting many vital proteins. However, its reconstruction in a functional in vitro adipose tissue is still a challenge. Mature adipocytes directly extracted from surgery liposuctions quickly lose their lipids after a week in vitro and the use of differentiated adipose stem cells is too time-consuming. We developed a new artificial fat tissue using collagen microfibers. These tissues allowed the maintenance of viable big unilocular mature adipocytes up to two weeks and the faster adipogenic differentiation of adipose stem cells. Moreover, the adipose functionality confirmed by perilipin and leptin assessments makes this model suitable for further applications in cosmetic/pharmaceutical drug assays or for tissue reconstruction.

Differential mineralization of human dental pulp stem cells on diverse polymers

In tissue engineering, biomaterials are used as scaffolds for spatial distribution of specific cell types. Biomaterials can potentially influence cell proliferation and extracellular matrix formation, both in positive and negative ways. The aim of the present study was to investigate and compare mineralized matrix production of human dental pulp stem cells (DPSC), cultured on 17 different well-characterized polymers. Osteogenic differentiation of DPSC was induced for 21 days on biomaterials using dexamethasone, L-ascorbic-acid-2-phosphate, and sodium β-glycerophosphate. Success of differentiation was analyzed by quantitative RealTime PCR, alkaline phosphatase (ALP) activity, and visualization of calcium accumulations by alizarin red staining with subsequent quantification by colorimetric method. All of the tested biomaterials of an established biomaterial bank enabled a mineralized matrix formation of the DPSC after osteoinductive stimulation. Mineralization on poly(tetrafluoro ethylene) (PTFE), poly(dimethyl siloxane) (PDMS), Texin, LT706, poly(epsilon-caprolactone) (PCL), polyesteramide type-C (PEA-C), hyaluronic acid, and fibrin was significantly enhanced (p<0.05) compared to standard tissue culture polystyrene (TCPS) as control. In particular, PEA-C, hyaluronic acid, and fibrin promoted superior mineralization values. These results were confirmed by ALP activity on the same materials. Different biomaterials differentially influence the differentiation and mineralized matrix formation of human DPSC. Based on the present results, promising biomaterial candidates for bone-related tissue engineering applications in combination with DPSC can be selected.

Enhanced chondrogenic differentiation of bone marrow mesenchymal stem cells on gelatin/glycosaminoglycan electrospun nanofibers with different amount of glycosaminoglycan

Tissue engineering is a new technique to help damaged cartilage treatment using cells and scaffolds. In this study we tried to evaluate electrospun scaffolds composed of gelatin/glycosaminoglycan (G/GAG) blend nanofibers in chondrogenesis of bone marrow-derived mesenchymal stem cells (BMMSCs). Scaffolds were fabricated by electrospinning technique with different concentration of glycosaminoglycan (0%, 5%, 10%, and 15%) in gelatin matrix. BMMSCs were cultured on the scaffolds for chondrogenesis process. MTT assay was done for scaffold's biocompatibility and cells viability evaluation. Alcian blue staining was carried out to determine the release of GAG and reverse transcription polymerase chain reaction (RT-PCR) was done for expression of COL2A1 and also immunocytochemistry assay were used to confirm expression of type II collagen. Scaffold with 15% GAG showed better result for biocompatibility (p =0.02). Scanning electron microscopy (SEM) micrographs showed that MSCs have good attachment to the scaffolds. Alcian blue staining result confirmed that cells produce GAG during differentiation time different from GAG in the scaffolds. Also the results for RT-PCR showed the expression of COL2A1 marker. Immunocytochemistry assay for type II collagen confirm that this protein expressed. Scaffold comprising 15% GAG is better results for chondrogenesis and it can be a good applicant for cartilage tissue engineering. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 38-48, 2019.

Toward Immunocompetent 3D Skin Models

3D human skin models provide a platform for toxicity testing, biomaterials evaluation, and investigation of fundamental biological processes. However, the majority of current in vitro models lack an inflammatory system, vasculature, and other characteristics of native skin, indicating scope for more physiologically complex models. Looking at the immune system, there are a variety of cells that could be integrated to create novel skin models, but to do this effectively it is also necessary to understand the interface between skin biology and tissue engineering as well as the different roles the immune system plays in specific health and disease states. Here, a progress report on skin immunity and current immunocompetent skin models with a focus on construction methods is presented; scaffold and cell choice as well as the requirements of physiologically relevant models are elaborated. The wide range of technological and fundamental challenges that need to be addressed to successfully generate immunocompetent skin models and the steps currently being made globally by researchers as they develop new models are explored. Induced pluripotent stem cells, microfluidic platforms to control the model environment, and new real-time monitoring techniques capable of probing biochemical processes within the models are discussed.

Mesenchymal Stem Cells as a Prospective Therapy for the Diabetic Foot

The diabetic foot is a serious complication of diabetes. Mesenchymal stem cells are an abundant source of stem cells which occupy a special position in cell therapies, and recent studies have suggested that mesenchymal stem cells can play essential roles in treatments for the diabetic foot. Here, we discuss the advances that have been made in mesenchymal stem cell treatments for this condition. The roles and functional mechanisms of mesenchymal stem cells in the diabetic foot are also summarized, and insights into current and future studies are presented.

Fabrication of Adipose-Derived Mesenchymal Stem Cell Aggregates using Biodegradable Porous Microspheres for Injectable Adipose Tissue Regeneration

Injectable mesenchymal stem cell aggregates were formed using hyaluronic acid (HA)-immobilized porous biodegradable microspheres for adipose tissue regeneration. Adipose tissue-derived mesenchymal stem cells (AMSCs) were aggregated in a controlled manner and differentiated into adipocytes by cultivating in a stirred suspension bioreactor. The resultant cellular aggregates were approx. 1700 μm in diameter and exhibited fully differentiated adipocytes, as shown by immunocytochemistry and RT-PCR. The cultured aggregates could be smoothly injected into the subcutaneous region of mice through a syringe needle due to their soft elasticity and deformability. The in vivo regenerated adipose tissue maintained a proper dimension and shape, showing natural adipose tissue characteristics, as demonstrated by various histological staining procedures. HA-immobilized microspheres significantly enhanced cell differentiation during 3D cultivation, and tissue regeneration when implanted in vivo, compared to unmodified porous microspheres. This study showed that AMSC cellular aggregates prepared by using porous microspheres could be delivered in an injectable manner into the body and could have great therapeutic potential for soft tissue augmentation and reconstruction.

Single-Step RNA Extraction from Different Hydrogel-Embedded Mesenchymal Stem Cells for Quantitative Reverse Transcription-Polymerase Chain Reaction Analysis

For many tissue engineering applications, cells such as human mesenchymal stem cells (hMSCs) must be embedded in hydrogels. The analysis of embedded hMSCs requires RNA extraction, but common extraction procedures often produce low yields and/or poor quality RNA. We systematically investigated four homogenization methods combined with eight RNA extraction protocols for hMSCs embedded in three common hydrogel types (alginate, agarose, and gelatin). We found for all three hydrogel types that using liquid nitrogen or a rotor-stator produced low RNA yields, whereas using a microhomogenizer or enzymatic/chemical hydrogel digestion achieved better yields regardless of which extraction protocol was subsequently applied. The hot phenol extraction protocol generally achieved the highest A260 values (representing up to 40.8 μg RNA per 10(6) cells), but the cetyltrimethylammonium bromide (CTAB) method produced RNA of better quality, with A260/A280 and A260/A230 ratios and UV spectra similar to the pure RNA control. The RNA produced by this method was also suitable as a template for endpoint and quantitative reverse transcription-PCR (qRT-PCR), achieving low Ct values of ∼20. The prudent choice of hydrogel homogenization and RNA extraction methods can ensure the preparation of high-quality RNA that generates reliable endpoint and quantitative RT-PCR data. We therefore propose a universal method that is suitable for the extraction of RNA from cells embedded in all three hydrogel types commonly used for tissue engineering.

Combined treatment with platelet-rich plasma and insulin favours chondrogenic and osteogenic differentiation of human adipose-derived stem cells in three-dimensional collagen scaffolds

Osteochondral lesions due to injury or other pathology commonly result in the development of osteoarthritis and progressive joint destruction. Bioengineered scaffolds are widely studied for regenerative surgery strategies in osteochondral defect management, also combining the use of stem cells, growth factors and hormones. The utility in tissue engineering of human adipose-derived stem cells (ASCs) isolated from adipose tissue has been widely noted. Autologous platelet-rich plasma (PRP) represents an alternative strategy in regenerative medicine for the local release of endogenous growth factors and hormones. Here we compared the effects of three-dimensional (3D) collagen type I scaffold culture and combined treatment with PRP and human recombinant insulin on the chondro-/osteogenic differentiation of ASCs. Histochemical and biomolecular analyses demonstrated that chondro-/osteogenic differentiation was increased in ASC-populated 3D collagen scaffolds compared with two-dimensional (2D) plastic dish culture. Chondro-/osteogenic differentiation was further enhanced in the presence of combined PRP (5% v/v) and insulin (100 nm) treatment. In addition, chondro-/osteogenic differentiation associated with the contraction of ASC-populated 3D collagen scaffold and increased β1/β3-integrin expression. Inhibition studies demonstrated that PRP/insulin-induced chondro-/osteogenic differentiation is independent of insulin-like growth factor 1 receptor (IGF-1R) and mammalian target of rapamycin (mTOR) signalling; IGF-R1/mTOR inhibition even enhanced ASC chondro-/osteogenic differentiation. Our findings underline that 3D collagen scaffold culture in association with platelet-derived growth factors and insulin favour the chondro-/osteogenic differentiation of ASCs, suggesting new translational applications in regenerative medicine for the management of osteochondral defects. Copyright © 2016 John Wiley & Sons, Ltd.

Opportunities and challenges in three-dimensional brown adipogenesis of stem cells

The formation of brown adipose tissue (BAT) via brown adipogenesis has become a notable process due to its ability to expend energy as heat with implications in the treatment of metabolic disorders and obesity. With the advent of complexity within white adipose tissue (WAT) along with inducible brown adipocytes (also known as brite and beige), there has been a surge in deciphering adipocyte biology as well as in vivo adipogenic microenvironments. A therapeutic outcome would benefit from understanding early events in brown adipogenesis, which can be accomplished by studying cellular differentiation. Pluripotent stem cells are an efficient model for differentiation and have been directed towards both white adipogenic and brown adipogenic lineages. The stem cell microenvironment greatly contributes to terminal cell fate and as such, has been mimicked extensively by various polymers including those that can form 3D hydrogel constructs capable of biochemical and/or mechanical modifications and modulations. Using bioengineering approaches towards the creation of 3D cell culture arrangements is more beneficial than traditional 2D culture in that it better recapitulates the native tissue biochemically and biomechanically. In addition, such an approach could potentially protect the tissue formed from necrosis and allow for more efficient implantation. In this review, we highlight the promise of brown adipocytes with a focus on brown adipogenic differentiation of stem cells using bioengineering approaches, along with potential challenges and opportunities that arise when considering the energy expenditure of BAT for prospective therapeutics.

Strategies for improving the physiological relevance of human engineered tissues

This review examines important robust methods for sustained, steady-state, in vitro culture. To achieve 'physiologically relevant' tissues in vitro additional complexity must be introduced to provide suitable transport, cell signaling, and matrix support for cells in 3D environments to achieve stable readouts of tissue function. Most tissue engineering systems draw conclusions on tissue functions such as responses to toxins, nutrition, or drugs based on short-term outcomes with in vitro cultures (2-14 days). However, short-term cultures limit insight with physiological relevance because the cells and tissues have not reached a steady-state.

Adhesion of human mesenchymal stem cells can be controlled by electron beam-microstructured titanium alloy surfaces during osteogenic differentiation

Several studies focusing on bone tissue engineering demonstrated that given microstructuring of an implant surface has a strong effect on its interaction with cells, and their adhesion and differentiation. In the present study, geometrically structured titanium alloy surfaces are shown to be able to guide cell adhesion during differentiation

Combined effects of connective tissue growth factor-modified bone marrow-derived mesenchymal stem cells and NaOH-treated PLGA scaffolds on the repair of articular cartilage defect in rabbits

In cartilage tissue engineering using stem cells, it is important to stimulate proliferation and control the differentiation of stem cells to specific lineages. Here we reported a combined technique for articular cartilage repair, consisting of bone marrow mesenchymal stem cells (BMMSCs) transfected with connective tissue growth factor (CTGF) gene and NaOH-treated poly(lactic-co-glycolic) acid (PLGA) scaffolds. In the present study, BMMSCs or CTGF-modified BMMSCs seeded on PLGA or NaOH-treated PLGA scaffolds were incubated in vitro and NaOH-treated PLGA significantly stimulated proliferation of BMMSCs, while CTGF gene transfer promoted chondrogenic differentiation. The effects of the composite on the repair of cartilage defects were evaluated in rabbit knee joints in vivo. Full-thickness cartilage defects (diameter: 5 mm; depth: 3 mm) were created unilaterally in the patellar groove. Defects were either left empty (n = 18) or implanted with BMMSCs/PLGA (n = 18), BMMSCs/NaOH-treated PLGA (n = 18), or CTGF-modified BMMSCs/NaOH-treated PLGA (n = 18). The defect area was examined grossly, histologically, and mechanically at 6, 12, and 24 weeks postoperatively. Implanted cells were tracked using adeno-LacZ labeling at 6 weeks after implantation. Overall, the CTGF-modified BMMSCs/NaOH-treated PLGA group showed successful hyaline-like cartilage regeneration similar to normal cartilage, which was superior to the other groups using gross examination, qualitative and quantitative histology, and mechanical assessment. The in vivo viability of the implanted cells was demonstrated by their retention for 6 weeks after implantation. These findings suggested that a combination of CTGF-modified BMMSCs and NaOH-treated PLGA may be an alternative treatment for large osteochondral defects in high-loading sites.

3D non-woven polyvinylidene fluoride scaffolds: fibre cross section and texturizing patterns have impact on growth of mesenchymal stromal cells

Several applications in tissue engineering require transplantation of cells embedded in appropriate biomaterial scaffolds. Such structures may consist of 3D non-woven fibrous materials whereas little is known about the impact of mesh size, pore architecture and fibre morphology on cellular behavior. In this study, we have developed polyvinylidene fluoride (PVDF) non-woven scaffolds with round, trilobal, or snowflake fibre cross section and different fibre crimp patterns (10, 16, or 28 needles per inch). Human mesenchymal stromal cells (MSCs) from adipose tissue were seeded in parallel on these scaffolds and their growth was compared. Initial cell adhesion during the seeding procedure was higher on non-wovens with round fibres than on those with snowflake or trilobal cross sections. All PVDF non-woven fabrics facilitated cell growth over a time course of 15 days. Interestingly, proliferation was significantly higher on non-wovens with round or trilobal fibres as compared to those with snowflake profile. Furthermore, proliferation increased in a wider, less dense network. Scanning electron microscopy (SEM) revealed that the MSCs aligned along the fibres and formed cellular layers spanning over the pores. 3D PVDF non-woven scaffolds support growth of MSCs, however fibre morphology and mesh size are relevant: proliferation is enhanced by round fibre cross sections and in rather wide-meshed scaffolds.

Hepatocyte growth factor-loaded biomaterials for mesenchymal stem cell recruitment

Human adult mesenchymal stem cells (MSC) can be readily harvested from bone marrow through aspiration. MSC are involved in tissue regeneration and repair, particularly in wound healing. Due to their high self-renewal capacity and excellent differentiation potential in vitro, MSC are ideally suited for regenerative medicine. The complex interactions of MSC with their environment and their influence on the molecular and functional levels are widely studied but not completely understood. MSC secrete, for example, hepatocyte growth factor (HGF), whose concentration is enhanced in wounded areas and which is shown to act as a chemoattractant for MSC. We produced HGF-loaded biomaterials based on collagen and fibrin gels to develop a recruitment system for endogenous MSC to improve wound healing. Here, we report that HGF incorporated into collagen or fibrin gels leads to enhanced and directed MSC migration in vitro. HGF-loaded biomaterials might be potentially used as in vivo wound dressings to recruit endogenous MSC from tissue-specific niches towards the wounded area. This novel approach may help to reduce costly multistep procedures of cell isolation, in vitro culture, and transplantation usually used in tissue engineering.

Adipose and mammary epithelial tissue engineering

Breast reconstruction is a type of surgery for women who have had a mastectomy, and involves using autologous tissue or prosthetic material to construct a natural-looking breast. Adipose tissue is the major contributor to the volume of the breast, whereas epithelial cells comprise the functional unit of the mammary gland. Adipose-derived stem cells (ASCs) can differentiate into both adipocytes and epithelial cells and can be acquired from autologous sources. ASCs are therefore an attractive candidate for clinical applications to repair or regenerate the breast. Here we review the current state of adipose tissue engineering methods, including the biomaterials used for adipose tissue engineering and the application of these techniques for mammary epithelial tissue engineering. Adipose tissue engineering combined with microfabrication approaches to engineer the epithelium represents a promising avenue to replicate the native structure of the breast.

Encapsulation of Mesenchymal Stem Cells by Bioscaffolds Protects Cell Survival and Attenuates Neuroinflammatory Reaction in Injured Brain Tissue after Transplantation

Since the brain is naturally inefficient in regenerating functional tissue after injury or disease, novel restorative strategies including stem cell transplantation and tissue engineering have to be considered. We have investigated the use of such strategies in order to achieve better functional repair outcomes. One of the fundamental challenges of successful transplantation is the delivery of cells to the injured site while maintaining cell viability. Classical cell delivery methods of intravenous or intraparenchymal injections are plagued by low engraftment and poor survival of transplanted stem cells. Novel implantable devices such as 3D bioactive scaffolds can provide the physical and metabolic support required for successful progenitor cell engraftment, proliferation, and maturation. In this study, we performed in situ analysis of laminin-linked dextran and gelatin macroporous scaffolds. We revealed the protective action of gelatin–laminin (GL) scaffolds seeded with mesenchymal stem cells derived from donated human Wharton's jelly (hUCMSCs) against neuroinflammatory reactions of injured mammalian brain tissue. These bioscaffolds have been implanted into (i) intact and (ii) ischemic rat hippocampal organotypic slices and into the striatum of (iii) normal and (iv) focally injured brains of adult Wistar rats. We found that transplantation of hUCMSCs encapsulated in GL scaffolds had a significant impact on the prevention of glial scar formation (low glial acidic fibrillary protein) and in the reduction of neuroinflammation (low interleukin-6 and the microglial markers ED1 and Iba1) in the recipient tissue. Moreover, implantation of hUCMSCs encapsulated within GL scaffolds induced matrix metalloproteinase-2 and -9 proteolytic activities in the surrounding brain tissue. This facilitated scaffold biodegradation while leaving the remaining grafted hUCMSCs untouched. In conclusion, transplanting GL scaffolds preseeded with hUCMSCs into mammalian brain tissue escaped the host's immune system and protected neural tissue from neuroinflammatory injury. This manuscript is published as part of the International Association of Neurorestoratology (IANR) supplement issue of Cell Transplantation.

Enhanced survival and neurite network formation of human umbilical cord blood neuronal progenitors in three-dimensional collagen constructs

Umbilical cord blood (CB) stem cells have been proposed for cell-based therapeutic applications for diverse diseases of the CNS. We hypothesized that tissue-engineering strategies may extend the efficacy of these approaches by improving the long-term viability and function of stem cell-derived neuronal progenitors. To test our hypothesis, we explored the survival and differentiation of human CB-derived neuronal progenitors (HUCBNP) in a three-dimensional (3D) collagen construct. In contrast to two-dimensional culture conditions, the cells survived in 3D for an extended period of time of more than 2 months. Under 3D conditions, HUCBNP underwent spontaneous neuronal differentiation, which was further enhanced by treatment with neuronal conditioned medium (CM) and nerve growth factor (NGF). Neurite outgrowth, quantified by assessing the fractal dimension (D f) of the complex neuronal networks, was significantly enhanced under 3D conditions in the presence of CM/NGF, concomitant with a reduced expression of the early neuronal marker nestin (1.9-fold), and increased levels of mature neuronal markers such as MAP-2 (3.6-fold), β-tubulin (1.5-fold), and neuronal specific enolase (6.6-fold) and the appearance of the synaptic marker synaptophysin. To assess the feasibility for clinical usage, HUCBNP were also isolated from frozen CB samples and cultured under 3D conditions. The data indicate the essential complete preservation of neurotrophic (survival) and neurotropic (neurite outgrowth) properties. In conclusion, 3D culture conditions are proposed as an essential step for both maintenance of CB neuronal progenitors in vitro and for investigating specific features of neuronal differentiation towards future use in regenerative therapy.

Comparing scaffold-free and fibrin-based adipose-derived stromal cell constructs for adipose tissue engineering: an in vitro and in vivo study

Success of adipose tissue engineering for soft tissue repair has been limited by insufficient adipogenic differentiation, an unfavorable host response, and insufficient vascularization. In this study, we examined how scaffold-free spheroid and fibrin-based environments impact these parameters in human adipose-derived stromal cell (ASC)-based adipose constructs. ASCs were differentiated in spheroids or fibrin-based constructs. After 7 days, conditioned medium was collected and spheroids/fibrin-based constructs were either harvested or implanted subcutaneously in athymic mice. Following 7 days of implantation, the number of blood vessels in fibrin-based constructs was significantly higher than in spheroids (93±45 vs. 23±11 vessels/mm(2)), and the inflammatory response to fibrin-based constructs was less severe. The reasons for these results were investigated further in vitro. We found that ASCs in fibrin-based constructs secreted significantly higher levels of the angiogenic factors VEGF and HGF and lower levels of the inflammatory cytokine IL-8. Furthermore, ASCs in fibrin-based constructs secreted significantly higher levels of leptin and showed a 2.5-fold upregulation of the adipogenic transcription factor PPARG and a fourfold to fivefold upregulation of the adipocyte-specific markers FABP4, perilipin, and leptin. These results indicate that fibrin-based ASC constructs are potentially more suitable for ASC-based adipose tissue reconstruction than scaffold-free spheroids.

Macrochanneled bioactive ceramic scaffolds in combination with collagen hydrogel: a new tool for bone tissue engineering

New tissue-engineering tool for bone regeneration is described to facilitate homogeneous cell seeding and effective osteogenic development. Calcium phosphate (CaP) scaffolds with macrochanneled and well-defined pore structure was developed, however, a large portion of the cells seeded directly within the scaffold easily penetrates without good adhesion to the scaffold surface. To overcome this, a method was exploited to dispense cells evenly throughout the CaP scaffold using collagen hydrogel. Rat bone marrow-derived mesenchymal stem cells (MSCs) were mixed within a neutralized collagen solution, which was then infiltrated into the macrochanneled pore space and gelled to result in macrochanneled bioceramic scaffold combined with MSCs-hydrogel. MSCs contained within the hydrogel-CaP scaffolds were highly viable, with similar growth pattern to those in the collagen hydrogel. Cells seeded by this approach were initially almost double in number compared with those seeded directly onto the CaP scaffold and had an active proliferation more than 14 days. Assessments of the MSCs showed significantly higher alkaline phosphatase levels in the combined scaffold, which was accompanied by enhanced osteogenesis including the expression of genes [collagen type I, bone sialoprotein, and osteopontin (OPN)] and proteins (OPN and osteocalcin). Extracellular calcium was also elevated significantly in the combined scaffold compared to the CaP scaffold. In addition, mechanical strength of the constructs was improved significantly in the combined scaffold compared to the CaP scaffold. Based on these, the cell culturing and tissue engineering strategy within the macrochanneled bioactive ceramic scaffolds could be improved greatly by the combinatory approach of using collagen hydrogel.

Endothelial progenitor cells improve directly and indirectly early vascularization of mesenchymal stem cell-driven bone regeneration in a critical bone defect in rats

Early vascularization of a composite in a critical bone defect is a prerequisite for ingrowth of osteogenic reparative cells to regenerate bone, since lack of vessels does not ensure a sufficient nutritional support of the bone graft. The innovation of this study was to investigate the direct and indirect effects of endothelial progenitor cells (EPCs) and cotransplanted mesenchymal stem cells (MSCs) on the in vivo neovascularization activity in a critical size defect at the early phase of endochondral ossification. Cultivated human EPCs and MSCs were loaded onto β-TCP in vitro. A critical-sized bone defect (5 mm) was created surgically in the femoral diaphysis of adult athymic rat and stabilized with an external fixateur. The bone defects were filled with β-TCP, MSCs seeded on β-TCP, EPCs seeded on β-TCP, and coculture of MSCs and EPCs seeded on β-TCP or autologous bone of rat. After 1 week, the rats were sacrificed. Using quantitative CD34 immunohistochemistry as well as qualitative analysis of vascularization (staining of MHC and VEGF) in decalcified serial sections were performed by means of an image analysis system. Fluorescence microscopy analyzed the direct effects and indirect effects of human implanted EPCs for vessel formation at bone regeneration site. Formation of a primitive vascular plexus was also detectable in the β-TCP, MSC, or autologous bone group, but on a significantly higher level if EPCs alone or combined with MSCs were transplanted. Moreover, highest amount of vascularization were detected when EPCs and MSCs together were implanted. Early vascularization is improved by transplanted EPCs, which formed new vessels directly. Indeed the indirect effect of EPCs to vascularization is much higher. Transplanted EPC release chemotactic factors (VEGF) to recruit EPCs of the host and stimulate vascularization in the bone defect. Transplantation of human EPCs displays a promising approach to improve early vascularization of a scaffold in a critical bone defect. Moreover, coculture of EPCs and MSCs demonstrate also a synergistic effect on new vessel formation and seems to be a potential osteogenic construct for in vivo application.

The enhancement of osteogenesis through the use of dental pulp pluripotent stem cells in 3D

The potential for osteogenic differentiation of dental pulp mesenchymal stem cells (DPMSCs) in vitro and in vivo has been well documented in a variety of studies. Previously, we obtained a population of cells from human dental pulp called dental pulp pluripotent stem cells (DPPSCs) that could differentiate into mesodermal, ectodermal and endodermal progenies. We compared the osteogenic capacity of DPPSCs and DPMSCs that had been isolated from the same donors (N=5) and cultivated in the same osteogenic medium in 3D (three dimensions) Cell Carrier glass scaffolds. We also compared the architecture of bone-like tissue obtained from DPPSCs and human maxillary bone tissue. Differentiation was evaluated by scanning electron microscopy, whereas the expression of bone markers such as ALP, Osteocalcin, COLL1 and Osteonectin was investigated by quantitative real time polymerase chain reaction (qRT-PCR). We also used calcium quantification, Alizarin red staining and alkaline phosphatase (ALP) activity to compare the two cell types. New bone tissue formed by DPPSCs was in perfect continuity with the trabecular host bone structure, and the restored bone network demonstrated high interconnectivity. Significant differences between DPPSCs and DPMSCs were observed for the expression of bone markers, calcium deposition and ALP activity during osteogenic differentiation; these criteria were higher for DPPSCs than DPMSCs. Both DPPSCs and differentiated tissue showed normal chromosomal dosage after being cultured in vitro and analysed using short-chromosome genomic hybridisation (short-CGH). This study demonstrates the stability and potential for the use of DPPSCs in bone tissue engineering applications.

[Mesenchymal stem cells and their interaction with biomaterials: potential applications in tissue engineering]

INTRODUCTION

Mesenchymal stem cells (MSC) are an important cell type for regenerative medicine and tissue engineering. They are involved in tissue regeneration by means of: (a) differentiation into specialised mesodermal cells and (b) their biosynthetic activity that is both immunomodulatory and trophic. In recent studies we analysed MSC in contact with different biomaterials to identify suitable combinations for tissue engineering.

METHODS

A biomaterial test platform was established to analyse cell adhesion, viability, proliferation, cytotoxicity according to ISO 10993-5, apoptosis and differentiation to adipocytes and osteoblasts on a variety of polymers (degradable biopolymers, degradable synthetic polymers, non-degradable synthetic polymers, shape memory polymers, and ceramics).

RESULTS

Using this platform, biomaterials which support MSC growth by maintaining their stem cell characteristics and support the differentiation of MSC towards mature osteoblasts were identified. Furthermore, we showed that MSC possess fibrinolytic capacities and perform extracellular matrix remodelling.

CONCLUSION

The data support the theory that MSC are involved in tissue regeneration both via their differentiation capacity and their trophic characteristics. We identified different MSC/biomaterial combinations which are suitable for stem cell-based bone tissue engineering.

Transcriptome analysis of MSC and MSC-derived osteoblasts on Resomer® LT706 and PCL: impact of biomaterial substrate on osteogenic differentiation

Background

Mesenchymal stem cells (MSC) represent a particularly attractive cell type for bone tissue engineering because of their ex vivo expansion potential and multipotent differentiation capacity. MSC are readily differentiated towards mature osteoblasts with well-established protocols. However, tissue engineering frequently involves three-dimensional scaffolds which (i) allow for cell adhesion in a spatial environment and (ii) meet application-specific criteria, such as stiffness, degradability and biocompatibility.

Methodology/Principal Findings

In the present study, we analysed two synthetic, long-term degradable polymers for their impact on MSC-based bone tissue engineering: PLLA-co-TMC (Resomer® LT706) and poly(ε-caprolactone) (PCL). Both polymers enhance the osteogenic differentiation compared to tissue culture polystyrene (TCPS) as determined by Alizarin red stainings, scanning electron microscopy, PCR and whole genome expression analysis. Resomer® LT706 and PCL differ in their influence on gene expression, with Resomer® LT706 being more potent in supporting osteogenic differentiation of MSC. The major trigger on the osteogenic fate, however, is from osteogenic induction medium.

Conclusion

This study demonstrates an enhanced osteogenic differentiation of MSC on Resomer® LT706 and PCL compared to TCPS. MSC cultured on Resomer® LT706 showed higher numbers of genes involved in skeletal development and bone formation. This identifies Resomer® LT706 as particularly attractive scaffold material for bone tissue engineering.

Chondrogenic potential of stem cells derived from amniotic fluid, adipose tissue, or bone marrow encapsulated in fibrin gels containing TGF-β3

In this study, several types of hMSCs, derived from bone marrow, adipose tissue, or amniotic fluid, were encapsulated in a fibrin hydrogel mixed with TGF-β3 and then evaluated for their capacity for differentiation in vitro and in vivo. For determination of stem cell differentiation, RT-PCR, real time quantitative PCR (qPCR), histology, and immunohistochemical assays were used for analysis of chondrogenesis. Using these analysis methods, several of the cultured hMSCS were found to highly express genes and proteins specific to cartilage forming tissues. Additionally, similar trends in expression were found in tissue recovered from nude mice transplanted with several types of hMSCs encapsulated in a fibrin hydrogel containing TGF-β3. The results of both in vitro and in vivo analyses showed that cultured or transplanted hMSCs mixed with TGF-β3 in a fibrin hydrogel differentiated into chondrocytes, suggesting that these cells would be suitable for reconstruction of hyaline articular cartilage.

Adipose tissue engineering for soft tissue regeneration

Current treatment modalities for soft tissue defects caused by various pathologies and trauma include autologous grafting and commercially available fillers. However, these treatment methods present a number of challenges and limitations, such as donor-site morbidity and volume loss over time. As such, improved therapeutic modalities need to be developed. Tissue engineering techniques offer novel solutions to these problems through development of bioactive tissue constructs that can regenerate adipose tissue in both structure and function. Recently, a number of studies have been designed to explore various methods to engineer human adipose tissue. This review will focus on these developments in the area of adipose tissue engineering for soft tissue replacement. The physiology of adipose tissue and current surgical therapies used to replace lost tissue volume, specifically in breast tissue, are introduced, and current biomaterials, cell sources, and tissue culture strategies are discussed. We discuss future areas of study in adipose tissue engineering.

Expansion of adipose mesenchymal stromal cells is affected by human platelet lysate and plating density

The composition of mesenchymal stromal cells (MSCs) changes in the course of in vitro culture expansion. Little is known how these cell preparations are influenced by culture media, plating density, or passaging. In this study, we have isolated MSCs from human adipose tissue in culture medium supplemented with either fetal calf serum (FCS) or human platelet lysate (HPL). In addition, culture expansion was simultaneously performed at plating densities of 10 or 10,000 cells/cm(2). The use of FCS resulted in larger cells, whereas HPL significantly enhanced proliferation. Notably, HPL also facilitated expansion for more population doublings than FCS (43 ± 3 vs. 22 ± 4 population doubling; p < 0.001), while plating density did not have a significant effect on long-term growth curves. To gain further insight into population dynamics, we conceived a cellular automaton model to simulate expansion of MSCS. It is based on the assumptions that the number of cell divisions is limited and that due to contact inhibition proliferation occurs only at the rim of colonies. The model predicts that low plating densities result in more heterogeneity with regard to cell division history, and favor subpopulations of higher migratory activity. In summary, HPL is a suitable serum supplement for isolation of MSC from adipose tissue and facilitates more population doublings than FCS. Cellular automaton computer simulations provided additional insights into how complex population dynamics during long-term expansion are affected by plating density and migration.

Bone marrow mesenchymal stem cells in a three-dimensional gelatin sponge scaffold attenuate inflammation, promote angiogenesis, and reduce cavity formation in experimental spinal cord injury

Three-dimensional (3D) gelatin sponge (GS) scaffolds were constructed by ensheathing GS with a thin film of poly-(lactide-co-glycolide) (PLGA). Rat bone marrow-derived mesenchymal stem cells (MSCs) were isolated, cultured, and then seeded to the scaffolds. Distribution of cells and cell growth, survival, and proliferation within the scaffolds were then determined. Immunofluorescence and Western blot analysis were employed to detect the deposition of fibronectin to the scaffolds on day 3 and day 7 of culture. Scaffolds with or without MSCs were then transplanted into the transected rat spinal cord. One or 8 weeks following transplantation, cavity areas, activated macrophages/microglia, expression of TNF-α and IL-1β, and neovascularization within the grafts were examined and quantified. Deposition of fibronectin (FN) and expression of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α) as potential inducing factors for angiogenesis were also examined. Results showed that 3D GS scaffolds allowed MSCs to adhere, survive, and proliferate and also FN to deposit. In vivo transplantation experiments demonstrated that these scaffolds were biocompatible, and MSCs seeded to the scaffolds played an important role in attenuating inflammation, promoting angiogenesis, and reducing cavity formation. Therefore, the GS scaffolds with MSCs may serve as promising supporting transplants for repairing spinal cord injury.

Stem cells isolated from human dental follicles have osteogenic potential

OBJECTIVE

Stem cells isolated from human dental follicles as a potential cell source for bone-tissue engineering were examined for correcting a critical bone defect.

STUDY DESIGN

Impacted third molars were collected and single cell-derived cell populations were cultivated in growth medium. Single cell-derived cell lines were examined in terms of cell shape, gene expression patterns, differentiation capacity in vitro, and osteogenic potential in vivo.

RESULTS

Three distinct cell populations were identified with different morphologies, patterns of gene expression, and differentiation capacity. All 3 cell populations promoted bone formation when transplanted into surgically created critical-size defects in immunodeficient rat calvaria, compared with control animals without cell transplantation, although one of these populations showed a weak capacity for osteogenetic differentiation in vitro.

CONCLUSIONS

Human dental follicle can derive at least 3 unique cell populations in culture, all of which promote bone formation in vivo.

Stem cell research in cell transplantation: sources, geopolitical influence, and transplantation

If the rapidly progressing field of stem cell research reaches its full potential, successful treatments and enhanced understanding of many diseases are the likely results. However, the full potential of stem cell science will only be reached if all possible avenues can be explored and on a worldwide scale. Until 2009, the US had a highly restrictive policy on obtaining cells from human embryos and fetal tissue, a policy that pushed research toward the use of adult-derived cells. Currently, US policy is still in flux, and retrospective analysis does show the US lagging behind the rest of the world in the proportional increase in embryonic/fetal stem cell research. The majority of US studies being on either a limited number of cell lines, or on cells derived elsewhere (or funded by other sources than Federal) rather than on freshly isolated embryonic or fetal material. Neural, mesenchymal, and the mixed stem cell mononuclear fraction are the most commonly investigated types, which can generally be classified as adult-derived stem cells, although roughly half of the neural stem cells are fetal derived. Other types, such as embryonic and fat-derived stem cells, are increasing in their prominence, suggesting that new types of stem cells are still being pursued. Sixty percent of the reported stem cell studies involved transplantation, of which over three quarters were allogeneic transplants. A high proportion of the cardiovascular systems articles were on allogeneic transplants in a number of different species, including several autologous studies. A number of pharmaceutical grade stem cell products have also recently been tested and reported on. Stem cell research shows considerable promise for the treatment of a number of disorders, some of which have entered clinical trials; over the next few years it will be interesting to see how these treatments progress in the clinic.

Cell transplantation for articular cartilage defects: principles of past, present, and future practice

As articular cartilage has very limited self-repair capability, the repair and regeneration of damaged cartilage is a major challenge. This review aims to outline the past, present, and future of cell therapies for articular cartilage defect repair. Autologous chondrocyte implantation (ACI) has been used clinically for more than 20 years, and the short, medium, and long-term clinical outcomes of three generation of ACI are extensively overviewed. Also, strategies of clinical outcome evaluation, ACI limitations, and the comparison of ACI clinical outcomes with those of other surgical techniques are discussed. Moreover, mesenchymal stem cells and pluripotent stem cells for cartilage regeneration in vitro, in vivo, and in a few clinical studies are reviewed. This review not only comprehensively analyzes the ACI clinical data but also considers the findings from state-of-the-art stem cell research on cartilage repair from bench and bedside. The conclusion provides clues for the future development of strategies for cartilage regeneration.

Treatment of ocular surface injuries by limbal and mesenchymal stem cells growing on nanofiber scaffolds

Stem cell (SC) therapy represents a promising approach to treat a wide variety of injuries, inherited diseases, or acquired SC deficiencies. One of the major problems associated with SC therapy remains the absence of a suitable matrix for SC growth and transfer. We describe here the growth and metabolic characteristics of mouse limbal stem cells (LSCs) and mesenchymal stem cells (MSCs) growing on 3D nanofiber scaffolds fabricated from polyamide 6/12 (PA6/12). The nanofibers were prepared by the original needleless electrospun Nanospider technology, which enables to create nanofibers of defined diameter, porosity, and a basis weight. Copolymer PA6/12 was selected on the basis of the stability of its nanofibers in aqueous solutions, its biocompatibility, and its superior properties as a matrix for the growth of LSCs, MSCs, and corneal epithelial and endothelial cell lines. The morphology, growth properties, and viability of cells grown on PA6/12 nanofibers were comparable with those grown on plastic. LSCs labeled with the fluorescent dye PKH26 and grown on PA6/12 nanofibers were transferred onto the damaged ocular surface, where their seeding and survival were monitored. Cotransfer of LSCs with MSCs, which have immunosuppressive properties, significantly inhibited local inflammatory reactions and supported the healing process. The results thus show that nanofibers prepared from copolymer PA6/12 represent a convenient scaffold for growth of LSCs and MSCs and transfer to treat SC deficiencies and various ocular surface injuries.

Cytocompatibility of high strength non-oxide ceramics

Oxide ceramic materials like alumina (Al(2)O(3)) and zirconia (ZrO(2)) are frequently used for medical applications like implants and prostheses because of their excellent biocompatibility and high wear resistance. Unfortunately, oxide ceramics cannot be used for minimal invasive thin-walled implants like resurfacing hip prostheses because of their limited strength. The hypothesis of this study is that non-oxide ceramics like silicon nitride (Si(3)N(4)) and silicon carbide (SiC)-not previously used in the medical field-are not only high strength and mechanically reliable ceramic materials due to their high amount of covalent bonds, but also exhibit a suitable biocompatibility for use as medical implants and prostheses. Mechanical investigations and cell culture tests with mouse fibroblast cells (L929) and human mesenchymal stem cells (hMSC) were performed on the ceramics. An excellent cytocompatibility was demonstrated by live/dead stainings for both L929 cells and hMSC. HMSC were able to differentiate towards osteoblasts on all tested ceramics. The determined strength of silicon nitride and silicon carbide was shown as significantly higher than that of oxide ceramics. Our results indicate that the high strength non-oxide ceramics are material candidates in the future especially for highly loaded, thin-walled implants like ceramic resurfacing hip prostheses.

Adipocyte transplantation and stem cells: plastic surgery meets regenerative medicine

The technologies for adipose tissue harvesting, processing, and transplantation have substantially evolved in the past two decades. Clinically driven advancements have paralleled a significant improvement in the understanding of cellular, molecular, and immunobiological events surrounding cell and tissue transplantation. These new mechanistic insights could be of assistance to better understand the mechanisms underlying some of the observed clinical improvements. In addition to plastic and reconstructive surgical applications, adipose tissue has become central to an increasing number of translational efforts involving adipose tissue-derived progenitor cells. The growing interest in this area of research has resulted in the exploration of many novel research and clinical applications that utilize adipose tissue grafting and/or progenitor/stem cell- derived cell products obtained from this tissue source. Progenitor, endothelial, and mesenchymal stem cells derived from adipose tissue could therefore not only be central to plastic and reconstructive surgery applications, but also become the focus of an array of therapeutic solutions for many disease conditions, such as those affecting bone, cartilage, muscle, liver, kidney, cardiac, neural, and the pancreas, expanding the possible indications and translational potential of tissue, cell-based, and regenerative medicine strategies.

Isolation, characterization, and differentiation potential of canine adipose-derived stem cells

Adipose tissue may represent a potential source of adult stem cells for tissue engineering applications in veterinary medicine. It can be obtained in large quantities, under local anesthesia, and with minimal discomfort. In this study, canine adipose tissue was obtained by biopsy from subcutaneous adipose tissue or by suction-assisted lipectomy (i.e., liposuction). Adipose tissue was processed to obtain a fibroblast-like population of cells similar to human adipose-derived stem cells (hASCs). These canine adipose-derived stem cells (cASCs) can be maintained in vitro for extended periods with stable population doubling and low levels of senescence. Immunofluorescence and flow cytometry show that the majority of cASCs are of mesodermal or mesenchymal origin. cASCs are able to differentiate in vitro into adipogenic, chondrogenic, myogenic, and osteogenic cells in the presence of lineage-specific induction factors. In conclusion, like human lipoaspirate, canine adipose tissue may also contain multipotent cells and represent an important stem cell source both for veterinary cell therapy as well as preclinical studies.

Advances in progenitor cell therapy using scaffolding constructs for central nervous system injury

Traumatic brain injury (TBI) is a major cause of morbidity and mortality in the United States. Current clinical therapy is focused on optimization of the acute/subacute intracerebral milieu, minimizing continued cell death, and subsequent intense rehabilitation to ameliorate the prolonged physical, cognitive, and psychosocial deficits that result from TBI. Adult progenitor (stem) cell therapies have shown promise in pre-clinical studies and remain a focus of intense scientific investigation. One of the fundamental challenges to successful translation of the large body of pre-clinical work is the delivery of progenitor cells to the target location/organ. Classically used vehicles such as intravenous and intra arterial infusion have shown low engraftment rates and risk of distal emboli. Novel delivery methods such as nanofiber scaffold implantation could provide the structural and nutritive support required for progenitor cell proliferation, engraftment, and differentiation. The focus of this review is to explore the current state of the art as it relates to current and novel progenitor cell delivery methods.

Human multipotent mesenchymal stromal cells from fetal lung expressing pluripotent markers and differentiating into cell types of three germ layers

Multipotent mesenchymal stromal cells (MSCs) are a promising cell type for cell transplantation; however, their utilization remains limited until the availability of adequate alternative sources of MSCs and the thorough understanding of the biology of MSCs isolated from various sources are realized. Fetal lung has been identified as a rich source of MSCs. To explore the therapeutic potential of passaged fetal lung MSCs (FLMSCs), the present study evaluated their growth kinetics, telomere length, karyotype, immunophenotype, and the differentiation potential during in vitro expansion. FLMSCs could be easily amplified in vitro with no significant shorting of telomere length and had a normal karyotype. No significant differences between passage 5 or passage 25 were observed in the immunophenotype analysis using flow cytometry. Moreover, flow cytometry results provided the first demonstration, to our knowledge, that FLMSCs stably expressed pluripotent markers including Oct4, Nanog, Sox2, TRA-1-60, c-Myc, and SSEA-4 through 25 passages. In vitro differentiation studies as identified by confocal microscopy, flow cytometry, RT-PCR, and immunohistochemistry showed that FLMSCs had extended capacity of differentiating into mesodermal, ectodermal, and endodermal lineages, and that their potential for adipogenic, osteogenic, and chondrogenic differentiation may be maintained over 25 passages. Furthermore, osteogenic and chondrogenic differentiation was used as an indicator of their differentiation capability in vivo, as evidenced by ectopic bone and cartilage formation. In summary, these results suggest that FLMSCs are a primitive population and that their extensive in vitro expansion does not involve significant functional modification of the cells, including morphology, growth, karyotype, immunophenotype, and mesodermal differentiation potential. Hence, FLMSCs might constitute an attractive cell resource for cell transplantation to induce regeneration of damaged tissues/organs.

The use of a shape-memory poly(epsilon-caprolactone)dimethacrylate network as a tissue engineering scaffold

Shape-memory polymers produced from many natural or synthetic raw polymers are able to undergo a shape transformation after exposure to a specific external stimulus. This feature enables their use in minimal-invasive surgery with a small, compact starting material switching over to a more voluminous structure in the body. The use of biomaterials in modern medicine calls for compatibility tests with cell types, encountering the biomaterial during a short-term or long-term in vivo application. We analysed the cell behaviour of L929 mouse fibroblasts, human mesenchymal stem cells, human mesothelial cells and rat mesothelial cells on a biodegradable shape-memory polymer network to assess its suitability for medical applications. Further, we investigated the differentiation capacity of mesenchymal stem cells into osteoblasts and adipocytes on the polymer and we analysed the influence of the shape-memory effect on adherent cells. The polymer was cytocompatible for all tested cell types, supporting cell viability and proliferation. The differentiation capacity of mesenchymal stem cells was supported by the polymer and shape-memory effect activation did not affect the majority of adherent cells.