A novel method for the isolation of subpopulations of rat adipose stem cells with different proliferation and osteogenic differentiation potentials

Bone marrow has been the elected cell source of studies published so far concerning bone and cartilage tissue-engineering approaches. Recent studies indicate that adipose tissue presents significant advantages over bone marrow as a cell source for tissue engineering. Most of these studies report the use of adipose stem cells (ASCs) isolated by a method based on the enzymatic digestion of the adipose tissue and on the ability of stem cells to adhere to a cell culture plastic surface. Using this method, a heterogeneous population was obtained containing different cell types that have been shown to compromise the proliferation and differentiation potential of the stem cells. This paper reports the development and optimization of a new isolation method that enables purified cell populations to be obtained that exhibit higher osteogenic differentiation and/or proliferation potential. This method is based on the use of immunomagnetic beads coated with specific antibodies and it is compared with other methods described in the literature for the selection of stem cell populations, e.g. methods based on a gradient solution and enzymatic digestion. The results showed that the isolation method based on immunomagnetic beads allows distinct subpopulations of rat ASCs to be isolated, showing different stem cells marker expressions and different osteogenic differentiation potentials. Therefore, this method can be used to study niches in ASC populations and/or also allow adipose tissue to be used as a stem cell source in a more efficient manner, increasing the potential of this cell source in future clinical applications.

Rapid vascularization of starch-poly(caprolactone) in vivo by outgrowth endothelial cells in co-culture with primary osteoblasts

The successful integration of in vitro-generated tissues is dependent on adequate vascularization in vivo. Human outgrowth endothelial cells (OECs) isolated from the mononuclear cell fraction of peripheral blood represent a potent population of circulating endothelial progenitors that could provide a cell source for rapid anastomosis and scaffold vascularization. Our previous work with these cells in co-culture with primary human osteoblasts has demonstrated their potential to form perfused vascular structures within a starch-poly(caprolactone) biomaterial in vivo. In the present study, we demonstrate the ability of OECs to form perfused vascular structures as early as 48 h following subcutaneous implantation of the biomaterial in vivo. The number of OEC-derived vessels increased throughout the study, an effect that was independent of the OEC donor. This finding of rapid and thorough OEC-mediated scaffold vascularization demonstrates the great potential for OEC-based strategies to promote vascularization in tissue engineering. OECs have the potential to contribute to host-derived scaffold vascularization, and formed vascular structures at a similar density as those arising from the host. Additionally, immunohistochemical evidence demonstrated the close interaction between OECs and the co-cultured osteoblasts. In addition to the known paracrine activity osteoblasts have in modulating angiogenesis of co-cultured OECs, we demonstrate the potential of osteoblasts to provide additional structural support for OEC-derived vessels, perhaps acting in a pericyte-like role.

Modified Gellan Gum hydrogels with tunable physical and mechanical properties

Gellan Gum (GG) has been recently proposed for tissue engineering applications. GG hydrogels are produced by physical crosslinking methods induced by temperature variation or by the presence of divalent cations. However, physical crosslinking methods may yield hydrogels that become weaker in physiological conditions due to the exchange of divalent cations by monovalent ones. Hence, this work presents a new class of GG hydrogels crosslinkable by both physical and chemical mechanisms. Methacrylate groups were incorporated in the GG chain, leading to the production of a methacrylated Gellan Gum (MeGG) hydrogel with highly tunable physical and mechanical properties. The chemical modification was confirmed by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR-ATR). The mechanical properties of the developed hydrogel networks, with Young's modulus values between 0.15 and 148 kPa, showed to be tuned by the different crosslinking mechanisms used. The in vitro swelling kinetics and hydrolytic degradation rate were dependent on the crosslinking mechanisms used to form the hydrogels. Three-dimensional (3D) encapsulation of NIH-3T3 fibroblast cells in MeGG networks demonstrated in vitro biocompatibility confirmed by high cell survival. Given the highly tunable mechanical and degradation properties of MeGG, it may be applicable for a wide range of tissue engineering approaches.

High dose ascorbic acid does not reverse central sympathetic overactivity in chronic heart failure

WHAT IS KNOWN AND OBJECTIVE

The increased central sympathetic activity typically associated with chronic heart failure (CHF) is probably mediated by formation of reactive oxygen species (ROS) in the brain. Our objective was to undertake a trial to test our hypothesis that administration of the well-known antioxidant and ROS scavenger ascorbic acid, would reverse or reduce the sympathetic overactivity in CHF patients.

METHODS

In a prospective, randomized, placebo-controlled, double-blind, cross-over trial, 11 CHF patients were treated with ascorbic acid 2 g/day or placebo for 3 days. At the end of each treatment period, sympathetic nervous system activity was measured by microneurography for direct muscle sympathetic nerve activity (MSNA) recording, analysis of heart rate variability (HRV) and measurement of plasma norepinephrine concentrations.

RESULTS

During ascorbic acid administration, plasma vitamin C levels were higher than during placebo (74·9 ± 6·0 μmol/L vs. 54·8 ± 4·6 μmol/L, P = 0·03). Ascorbic acid had no effect on sympathetic activity: MSNA (ascorbic acid: 66·8 ± 3·3 vs. placebo 66·9 ± 3·2 bursts/100 beats, P = 0·98). In addition, HRV and plasma norepinephrine levels did not differ.

WHAT IS NEW AND CONCLUSION

  Short-term administration of the antioxidant ascorbic acid in CHF patients does not reverse the increased sympathetic activity as measured by microneurography, HRV and plasma norepinephrine levels. The use of higher oral dosages seems not feasible due to accompanying side effects.

Dynamic culture of osteogenic cells in biomimetically coated poly(caprolactone) nanofibre mesh constructs

In our previous work, biomimetic calcium phosphate-coated poly(caprolactone) nanofibre meshes (BCP-NMs) were demonstrated to be more effective for supporting cell attachment and proliferation under static conditions, when compared with poly(caprolactone) nanofibre meshes (PCL-NMs). In many applications, in vitro cultivation of constructs using bioreactors that support efficient nutrition of cells has appeared as an important step toward the development of functional grafts. This work aimed at studying the effects of dynamic culture conditions and biomimetic coating on bone cells grown on the nanofibre meshes. BCP-NM and PCL-NM were seeded with osteoblast-like cells (MG63--human osteosarcoma-derived cell line). The cell-seeded constructs were cultured within a rotating bioreactor that simulated microgravity, at a fixed rotating speed, for different time periods, and then characterized. Cell morphology, viability, and phenotype were assessed. PCL-NM constructs presented a higher number of dead cells than BCP-NM constructs. Under dynamic conditions, the production of proteins associated with the extracellular matrix of bone was higher on BCP-NM constructs than in the PCL-NM ones, which indicates that coated samples may provide cells with a better environment for tissue growth. It is suggested that improved mass transfer in the bioreactor in combination with the appropriate substrate were decisive factors for this highly positive outcome for generating bone.

Adipose tissue-derived stem cells and their application in bone and cartilage tissue engineering

The adipose tissue was considered a reserve of energy until the '80s, when it was found that this tissue was involved in the metabolism of sex steroids such as estrogens. From then on, the importance attributed to this tissue radically changed as it was then considered an active organ, involved in important functions of the human body. In 2001, for the first time, the existence of stem cells within this tissue was reported, and since then, this tissue has been gaining an increased importance as a stem cell source for a wide range of potential applications in cell therapies and/or tissue engineering and regenerative medicine strategies, mainly due to its wide availability and easy access. This manuscript provides an overview on adipose stem cells (i.e., adipose tissue-derived stem cells, ASCs) considering the tissue of origin, the niche of the ASCs, and their phenotype in all aspects. In this paper it is also discussed the markers that have been used for the characterization of these cells, their differentiation properties, and their immunological reactivity, reporting studies from 2001 until this date. The ASCs are also compared with bone marrow stem cells (BMSCs), until now considered as the gold standard source of stem cells, underlining the common characteristics and the differences between the stem cells obtained from these two sources, as well as the advantages and disadvantages of their potential use in different applications. Finally, this review will also focus on the potential application of ASCs in tissue engineering applications, particularly in the regeneration of bone and cartilage, commenting on the progress of this approach and future trends of the field.

Injectable gellan gum hydrogels with autologous cells for the treatment of rabbit articular cartilage defects

In this work, the ability of gellan gum hydrogels coupled with autologous cells to regenerate rabbit full-thickness articular cartilage defects was tested. Five study groups were defined: (a) gellan gum with encapsulated chondrogenic predifferentiated rabbit adipose stem cells (ASC + GF); (b) gellan gum with encapsulated nonchondrogenic predifferentiated rabbit adipose stem cells (ASC); (c) gellan gum with encapsulated rabbit articular chondrocytes (AC) (standard control); (d) gellan gum alone (control); (e) empty defect (control). Full-thickness articular cartilage defects were created and the gellan gum constructs were injected and left for 8 weeks. The macroscopic aspect of the explants showed a progressive increase of similarity with the lateral native cartilage, stable integration at the defect site, more pronouncedly in the cell-loaded constructs. Tissue scoring showed that ASC + GF exhibited the best results regarding tissue quality progression. Alcian blue retrieved similar results with a better outcome for the cell-loaded constructs. Regarding real-time PCR analyses, ASC + GF had the best progression with an upregulation of collagen type II and aggrecan, and a downregulation of collagen type I. Gellan gum hydrogels combined with autologous cells constitute a promising approach for the treatment of articular cartilage defects, and adipose derived cells may constitute a valid alternative to currently used articular chondrocytes.

Cell Adhesion and Proliferation onto Chitosan-based Membranes Treated by Plasma Surface Modification

Surface properties play a vital role in the functioning of a biomaterial. Cellular adherence and growth onto biomaterials can be enhanced in biomaterial modifications of their surface. In this work, the cell behavior on chitosan membranes modified by argon and nitrogen-plasma treatments was investigated. Characterization of the membranes was performed using atomic force microscopy, contact angle measurements, and X-ray photoelectron spectroscopy. Cytotoxicity assessment and direct contact assay were carried out for untreated and treated chitosan membranes using L929 fibroblast-like cells. Cell morphology and cell viability were assessed to evaluate the cell attachment and proliferation. Changes in terms of roughness, surface chemistry, and hydrophilicity/hydrophobic balance of chitosan-modified membranes were observed. Regarding cell studies, the findings revealed that the extracts of all membranes do not induce cytotoxic effects. Moreover, the in vitro assays evidenced an improvement of the L929 adhesion and attachment when compared to untreated chitosan membranes. Overall, the data obtained clearly demonstrated that plasma treatments constitute an effective way of improving the biocompatibility of chitosan membranes towards to their use in biomedical applications.

Development of new chitosan/carrageenan nanoparticles for drug delivery applications

The use of polymeric nanoparticles, especially those composed of natural polymers, has become a very interesting approach in drug delivery, mainly because of the advantages offered by their small dimensions. The aim of this work was to develop a novel formulation of nanoparticles comprised of two natural marine-derived polymers, namely chitosan and carrageenan, and to evaluate their potential for the association and controlled release of macromolecules. Nanoparticles were obtained in a hydrophilic environment, under very mild conditions, avoiding the use of organic solvents or other aggressive technologies for their preparation. The developed nanocarriers presented sizes within 350-650 nm and positive zeta potentials of 50-60 mV. Polymeric interactions between nanoparticles' components were evaluated by Fourier transform infrared spectroscopy. Using ovalbumin as model protein, nanoparticles evidenced loading capacity varying from 4% to 17% and demonstrated excellent capacity to provide a controlled release for up to 3 weeks. Furthermore, nanoparticles have demonstrated to exhibit a noncytotoxic behavior in biological in vitro tests performed using L929 fibroblasts, which is critical regarding the biocompatibility of those carriers. In summary, the developed chitosan-carrageenan nanoparticles have shown promising properties to be used as carriers of therapeutic macromolecules, with potential application not only strictly in drug delivery, but also in broader areas, such as tissue engineering and regenerative medicine.

The role of lipase and alpha-amylase in the degradation of starch/poly(epsilon-caprolactone) fiber meshes and the osteogenic differentiation of cultured marrow stromal cells

The present work studies the influence of hydrolytic enzymes (alpha-amylase or lipase) on the degradation of fiber mesh scaffolds based on a blend of starch and poly(epsilon-caprolactone) (SPCL) and the osteogenic differentiation of osteogenic medium-expanded rat bone marrow stromal cells (MSCs) and subsequent formation of extracellular matrix on these scaffolds under static culture conditions. The biodegradation profile of SPCL fiber meshes was investigated using enzymes that are specifically responsible for the enzymatic hydrolysis of SPCL using concentrations similar to those found in human serum. These degradation studies were performed under static and dynamic conditions. After several degradation periods (3, 7, 14, 21, and 30 days), weight loss measurements and micro-computed tomography analysis (specifically porosity, interconnectivity, mean pore size, and fiber thickness) were performed. The SPCL scaffolds were seeded with rat MSCs and cultured for 8 and 16 days using complete osteogenic media with and without enzymes (alpha-amylase or lipase). Results indicate that culture medium supplemented with enzymes enhanced cell proliferation after 16 days of culture, whereas culture medium without enzymes did not. No calcium was detected in groups cultured with alpha-amylase or without enzymes after each time period, although groups cultured with lipase presented calcium deposition after the eighth day, showing a significant increase at the sixteenth day. Lipase appears to positively influence osteoblastic differentiation of rat MSCs and to enhance matrix mineralization. Furthermore, scanning electron microscopy images showed that the enzymes did not have a deleterious effect on the three-dimensional structure of SPCL fiber meshes, meaning that the scaffolds did not lose their structural integrity after 16 days. Confocal micrographs have shown cells to be evenly distributed and infiltrated within the SPCL fiber meshes up to 410 microm from the surface. This study demonstrates that supplementation of culture media with lipase holds great potential for the generation of bone tissue engineering constructs from MSCs seeded onto SPCL fiber meshes, because lipase enhances the osteoblastic differentiation of the seeded MSCs and promotes matrix mineralization without harming the structural integrity of the meshes over 16 days of culture.

Proliferation and differentiation of goat bone marrow stromal cells in 3D scaffolds with tunable hydrophilicity

We have synthesized methacrylate-endcapped caprolactone networks with tailored water sorption ability, poly(CLMA-co-HEA), in the form of three-dimensional (3D) scaffolds with the same architecture but exhibiting different hydrophilicity character (x(HEA)=0, 0.3, 0.5), and we investigated the interaction of goat bone marrow stromal cells (GBMSCs) with such structures. For this purpose, GBMSCs were seeded and cultured for 3, 7, 14, 21, and 28 days onto the developed scaffolds. Cells have proliferated throughout the whole scaffold volume. Cell adhesion and morphology were analyzed by SEM, whereas cell viability and proliferation was assessed by MTS test and DNA quantification concluding that numbers of cells increased as a function of the culturing time (until day 14) and also with the hydrophobic content in the samples (from 50 to 100% of CLMA). No significant difference between samples with 100% and 70% of CLMA were detected in some cases. Osteoblastic differentiation was followed by assessing the alkaline phosphatase activity of cells, as well as type I collagen and osteocalcin expressions levels until day 21. The three markers were positive at days 14 and 21 when cells were cultured in 100% CLMA substrates which suggests osteoblastic differentiation of mesenchymal stem cells within these scaffolds. On the other hand, when the CLMA content decreases (until 50%), type I collagen and osteocalcin were positive but ALP was negative indicating that the differentiation process is affected by hydrophilic content. We suggest that such system may be useful to extract information on the effect of materials' wettability on the corresponding biological performance in a 3D environment. Such general insights may be relevant in the context of biomaterials selection for tissue engineering strategies.

Macroporous hydroxyapatite scaffolds for bone tissue engineering applications: physicochemical characterization and assessment of rat bone marrow stromal cell viability

In this work, a new methodology is reported for developing hydroxyapatite (HA) scaffolds using an organic sacrifice template. The novelty of work consists of possibility of obtaining porous and highly interconnected scaffolds mimicking the sacrificial component. Our purpose consisted of evaluating the physicochemical properties of the HA scaffolds by means of Fourier transform infra-red spectroscopy, X-ray diffraction analysis, and scanning electron microscopy (SEM) attached with an X-ray detector. The HA scaffolds obtained possess a porosity of approximately 70%, and macropores diameter in the range of 50-600 microm. In contrast, results regarding the microcomputed tomography analysis have demonstrated both high pore uniformity and interconnectivity across the scaffolds. The compressive strength of the HA scaffolds was found to be 30.2 +/- 6.0 MPa. Bioactivity of the HA scaffolds was assessed by immersion into a simulated body fluid solution, in vitro. SEM observations have showed a deposition of apatite on the surface of the HA scaffolds, with a "cauliflower-like" morphology after 1 day, and tend to be more pronounced with the immersion time. The changes in calcium and phosphorus concentration were monitored by inductively-coupled plasma optical emission spectrometry. Cytotoxicity of the HA scaffolds was preliminarily investigated by carrying direct observation of mouse fibroblasts cells (L929 cell-line) death in the inverted microscope, and then cell viability was determined by means of carrying out a MTS assay. Complementarily, a luminescent cell viability assay based on the quantification of adenosine triphosphate was performed using rat bone marrow stromal cells (RBMSCs). A LIVE/DEAD assay and SEM analysis allowed the visualization of the RBMSCs adhesion and proliferation on the surface of the HA scaffolds. According to the results obtained from 3D architecture, mechanical properties, biocompatibility, and adhesion tests, it is suggested that HA scaffolds has potential to find applications in bone tissue engineering scaffolding.

Carrageenan-based hydrogels for the controlled delivery of PDGF-BB in bone tissue engineering applications

One of the major drawbacks found in most bone tissue engineering approaches developed so far consists in the lack of strategies to promote vascularisation. Some studies have addressed different issues that may enhance vascularisation in tissue engineered constructs, most of them involving the use of growth factors (GFs) that are involved in the restitution of the vascularity in a damaged zone. The use of sustained delivery systems might also play an important role in the re-establishment of angiogenesis. In this study, kappa-carrageenan, a naturally occurring polymer, was used to develop hydrogel beads with the ability to incorporate GFs with the purpose of establishing an effective angiogenesis mechanism. Some processing parameters were studied and their influence on the final bead properties was evaluated. Platelet derived growth factor (PDGF-BB) was selected as the angiogenic factor to incorporate in the developed beads, and the results demonstrate the achievement of an efficient encapsulation and controlled release profile matching those usually required for the development of a fully functional vascular network. In general, the obtained results demonstrate the potential of these systems for bone tissue engineering applications.

Novel method for the isolation of adipose stem cells (ASCs)

Adipose stem cells (ASCs) represent a cell population with great potential for tissue engineering applications. Several articles have been published showing the proliferation and differentiation potential, the markers and the wide range of potential applications of these cells. In the majority of these studies the ASCs are isolated using a basic enzymatic procedure, which results in a quite heterogeneous cell population that compromises their proliferation and differentiation. This paper reports the development and optimization of a new isolation/purification method that allows populations of ASCs to be obtained, which significantly reduces (and eventually eliminates) the 'contamination' of other cell types. This method is based on the use of immunomagnetic beads coated with specific antibodies. The first part of the study described here analysed the expression of marker genes for stem cells and the colony-forming unit (CFU) capacity of the cells isolated, while the second part is dedicated to the osteogenic differentiation potential of the isolated cells. The results showed that, using the isolation method based on immunomagnetic beads, it was possible to obtain ASCs and also underline the existence of several subpopulations of stem cells in the adipose tissue.

Studies of P(L/D)LA 96/4 non-woven scaffolds and fibres; properties, wettability and cell spreading before and after intrusive treatment methods

Poly(L/D)lactide 96/4 fibres with diameters of 50 and 80 microm were produced. The smaller diameter fibres were carded and needle punched to form a non-woven mat. Fibres and non-woven mats were hydrolysed for a period of 20 weeks. Fibres and pressed non-woven discs were treated with low-temperature oxygen plasma and alkaline KOH hydrolysis and ethanol washing was used as a reference treatment. The non-wovens lost 50% of their tear strength after 8 weeks in vitro while the fibres still retained 65% tensile strength after 20 weeks. Hydrolysation time in KOH, treatment time and power settings of the oxygen plasma were all directly proportional to the mechanical properties of the fibres. Increasing time (and power) resulted in lower tensile properties. Rapid wetting of the scaffolds was achieved by oxygen plasma, KOH hydrolysation and ethanol washing. Cell culturing using fibroblast cell line was carried out for the treated and non-treated non-woven scaffolds. In terms of adhesion and the spreading of the cells into the scaffold, best results after 3-day culturing were obtained for the oxygen plasma treated scaffolds.

Biodegradable nanomats produced by electrospinning: expanding multifunctionality and potential for tissue engineering

With increasing interest in nanotechnology, development of nanofibers (n-fibers) by using the technique of electrospinning is gaining new momentum. Among important potential applications of n-fiber-based structures, scaffolds for tissue-engineering represent an advancing front. Nanoscaffolds (n-scaffolds) are closer to natural extracellular matrix (ECM) and its nanoscale fibrous structure. Although the technique of electrospinning is relatively old, various improvements have been made in the last decades to explore the spinning of submicron fibers from biodegradable polymers and to develop also multifunctional drug-releasing and bioactive scaffolds. Various factors can affect the properties of resulting nanostructures that can be classified into three main categories, namely: (1) Substrate related, (2) Apparatus related, and (3) Environment related factors. Developed n-scaffolds were tested for their cytocompatibility using different cell models and were seeded with cells for to develop tissue engineering constructs. Most importantly, studies have looked at the potential of using n-scaffolds for the development of blood vessels. There is a large area ahead for further applications and development of the field. For instance, multifunctional scaffolds that can be used as controlled delivery system do have a potential and have yet to be investigated for engineering of various tissues. So far, in vivo data on n-scaffolds are scarce, but in future reports are expected to emerge. With the convergence of the fields of nanotechnology, drug release and tissue engineering, new solutions could be found for the current limitations of tissue engineering scaffolds, which may enhance their functionality upon in vivo implantation. In this paper electrospinning process, factors affecting it, used polymers, developed n-scaffolds and their characterization are reviewed with focus on application in tissue engineering.

A cartilage tissue engineering approach combining starch-polycaprolactone fibre mesh scaffolds with bovine articular chondrocytes

In the present work we originally tested the suitability of corn starch-polycaprolactone (SPCL) scaffolds for pursuing a cartilage tissue engineering approach. Bovine articular chondrocytes were seeded on SPCL scaffolds under dynamic conditions using spinner flasks (total of 4 scaffolds per spinner flask using cell suspensions of 0.5 x 10(6) cells/ml) and cultured under orbital agitation for a total of 6 weeks. Poly(glycolic acid) (PGA) non-woven scaffolds and bovine native articular cartilage were used as standard controls for the conducted experiments. PGA is a kind of standard in tissue engineering approaches and it was used as a control in that sense. The tissue engineered constructs were characterized at different time periods by scanning electron microscopy (SEM), hematoxylin-eosin (H&E) and toluidine blue stainings, immunolocalisation of collagen types I and II, and dimethylmethylene blue (DMB) assay for glycosaminoglycans (GAG) quantification assay. SEM results for SPCL constructs showed that the chondrocytes presented normal morphological features, with extensive cells presence at the surface of the support structures, and penetrating the scaffolds pores. These observations were further corroborated by H&E staining. Toluidine blue and immunohistochemistry exhibited extracellular matrix deposition throughout the 3D structure. Glycosaminoglycans, and collagen types I and II were detected. However, stronger staining for collagen type II was observed when compared to collagen type I. The PGA constructs presented similar features to SPCL at the end of the 6 weeks. PGA constructs exhibited higher amounts of matrix glycosaminoglycans when compared to the SPCL scaffolds. However, we also observed a lack of tissue in the central area of the PGA scaffolds. Reasons for these occurrences may include inefficient cells penetration, necrosis due to high cell densities, or necrosis related with acidic by-products degradation. Such situation was not detected in the SPCL scaffolds, indicating the much better biocompatibility of the starch based scaffolds.

Response of micro- and macrovascular endothelial cells to starch-based fiber meshes for bone tissue engineering

The establishment of a functional vasculature is as yet an unrealized milestone in bone reconstruction therapy. For this study, fiber-mesh scaffolds obtained from a blend of starch and poly(caprolactone) (SPCL), that have previously been shown to be an excellent material for the proliferation and differentiation of bone marrow cells and thereby represent great potential as constructs for bone regeneration, were examined for endothelial cell (EC) compatibility. To be successfully applied in vivo, this tissue engineered construct should also be able to support the growth of ECs in order to facilitate vascularization and therefore assure the viability of the construct upon implantation. The main goal of this study was to examine the interactions between ECs and SPCL fiber meshes. Primary cultures of HUVEC cells were selected as a model of macrovascular cells and the cell line HPMEC-ST1.6R as a model for microvascular ECs. Both macro- and microvascular ECs adhered to SPCL fiber-mesh scaffolds and grew to cover much of the available surface area of the scaffold. In addition, ECs growing on the SPCL fibers exhibited a typical morphology, maintained important functional properties, such as the expression of the intercellular junction proteins, PECAM-1 and VE-cadherin, the expression of the most typical endothelial marker vWF and sensitivity to pro-inflammatory stimuli, as shown by induction of the expression of cell adhesion molecules (CAMs) by lipopolysaccharide (LPS). These data indicate that ECs growing on SPCL fiber-mesh scaffolds maintain a normal expression of EC-specific genes/proteins, indicating a cell compatibility and potential suitability of these scaffolds for the vascularization process in bone tissue engineering in vivo.

Novel hydroxyapatite/chitosan bilayered scaffold for osteochondral tissue-engineering applications: Scaffold design and its performance when seeded with goat bone marrow stromal cells

Recent studies suggest that bone marrow stromal cells are a potential source of osteoblasts and chondrocytes and can be used to regenerate damaged tissues using a tissue-engineering (TE) approach. However, these strategies require the use of an appropriate scaffold architecture that can support the formation de novo of either bone and cartilage tissue, or both, as in the case of osteochondral defects. The later has been attracting a great deal of attention since it is considered a difficult goal to achieve. This work consisted on developing novel hydroxyapatite/chitosan (HA/CS) bilayered scaffold by combining a sintering and a freeze-drying technique, and aims to show the potential of such type of scaffolds for being used in TE of osteochondral defects. The developed HA/CS bilayered scaffolds were characterized by Fourier transform infra-red spectroscopy, X-ray diffraction analysis, micro-computed tomography, and scanning electron microscopy (SEM). Additionally, the mechanical properties of HA/CS bilayered scaffolds were assessed under compression. In vitro tests were also carried out, in order to study the water-uptake and weight loss profile of the HA/CS bilayered scaffolds. This was done by means of soaking the scaffolds into a phosphate buffered saline for 1 up to 30 days. The intrinsic cytotoxicity of the HA scaffolds and HA/CS bilayered scaffolds extract fluids was investigated by carrying out a cellular viability assay (MTS test) using Mouse fibroblastic-like cells. Results have shown that materials do not exert any cytotoxic effect. Complementarily, in vitro (phase I) cell culture studies were carried out to evaluate the capacity of HA and CS layers to separately, support the growth and differentiation of goat marrow stromal cells (GBMCs) into osteoblasts and chondrocytes, respectively. Cell adhesion and morphology were analysed by SEM while the cell viability and proliferation were assessed by MTS test and DNA quantification. The chondrogenic differentiation of GBMCs was evaluated measuring the glucosaminoglycans synthesis. Data showed that GBMCs were able to adhere, proliferate and osteogenic differentiation was evaluated by alkaline phosphatase activity and immunocytochemistry assays after 14 days in osteogenic medium and into chondrocytes after 21 days in culture with chondrogenic medium. The obtained results concerning the physicochemical and biological properties of the developed HA/CS bilayered scaffolds, show that these constructs exhibit great potential for their use in TE strategies leading to the formation of adequate tissue substitutes for the regeneration of osteochondral defects.

Influence of the Porosity of Starch-Based Fiber Mesh Scaffolds on the Proliferation and Osteogenic Differentiation of Bone Marrow Stromal Cells Cultured in a Flow Perfusion Bioreactor

This study investigates the influence of the porosity of fiber mesh scaffolds obtained from a blend of starch and poly(epsilon-caprolactone) on the proliferation and osteogenic differentiation of marrow stromal cells cultured under static and flow perfusion conditions. For this purpose, biodegradable scaffolds were fabricated by a fiber bonding method into mesh structures with two different porosities-- 50 and 75%. These scaffolds were then seeded with marrow stromal cells harvested from Wistar rats and cultured in a flow perfusion bioreactor or in 6-well plates for up to 15 days. Scaffolds of 75% porosity demonstrated significantly enhanced cell proliferation under both static and flow perfusion culture conditions. The expression of alkaline phosphatase activity was higher in flow cultures, but only for cells cultured onto the higher porosity scaffolds. Calcium deposition patterns were similar for both scaffolds, showing a significant enhancement of calcium deposition on cellscaffold constructs cultured under flow perfusion, as compared to static cultures. Calcium deposition was higher in scaffolds of 75% porosity, but this difference was not statistically significant. Observation by scanning electron microscopy showed the formation of pore-like structures within the extracellular matrix deposited on the higher porosity scaffolds. Fourier transformed infrared spectroscopy with attenuated total reflectance and thin-film X-ray diffraction analysis of the cell-scaffold constructs after 15 days of culture in a flow perfusion bioreactor revealed the presence of a mineralized matrix similar to bone. These findings indicate that starch-based scaffolds, in conjunction with fluid flow bioreactor culture, minimize diffusion constraints and provide mechanical stimulation to the marrow stromal cells, leading to enhancement of differentiation toward development of bone-like mineralized tissue. These results also demonstrate that the scaffold structure, namely, the porosity, influences the sequential development of osteoblastic cells and, in combination with the culture conditions, may affect the functionality of tissues formed in vitro.