Bone differentiation of marrow-derived mesenchymal stem cells using beta-tricalcium phosphate-alginate-gelatin hybrid scaffolds

Calcium Orthophosphate (CaPO4) Containing Composites for Biomedical Applications: Formulations, Properties, and Applications

The goal of this review is to present a wide range of hybrid formulations and composites containing calcium orthophosphates (abbreviated as CaPO4) that are suitable for use in biomedical applications and currently on the market. The bioactive, biocompatible, and osteoconductive properties of various CaPO4-based formulations make them valuable in the rapidly developing field of biomedical research, both in vitro and in vivo. Due to the brittleness of CaPO4, it is essential to combine the desired osteologic properties of ceramic CaPO4 with those of other compounds to create novel, multifunctional bone graft biomaterials. Consequently, this analysis offers a thorough overview of the hybrid formulations and CaPO4-based composites that are currently known. To do this, a comprehensive search of the literature on the subject was carried out in all significant databases to extract pertinent papers. There have been many formulations found with different material compositions, production methods, structural and bioactive features, and in vitro and in vivo properties. When these formulations contain additional biofunctional ingredients, such as drugs, proteins, enzymes, or antibacterial agents, they offer improved biomedical applications. Moreover, a lot of these formulations allow cell loading and promote the development of smart formulations based on CaPO4. This evaluation also discusses basic problems and scientific difficulties that call for more investigation and advancements. It also indicates perspectives for the future.

Post-decellularization techniques ameliorate cartilage decellularization process for tissue engineering applications

Due to the current lack of innovative and effective therapeutic approaches, tissue engineering (TE) has attracted much attention during the last decades providing new hopes for the treatment of several degenerative disorders. Tissue engineering is a complex procedure, which includes processes of decellularization and recellularization of biological tissues or functionalization of artificial scaffolds by active cells. In this review, we have first discussed those conventional steps, which have led to great advancements during the last several years. Moreover, we have paid special attention to the new methods of post-decellularization that can significantly ameliorate the efficiency of decellularized cartilage extracellular matrix (ECM) for the treatment of osteoarthritis (OA). We propose a series of post-decellularization procedures to overcome the current shortcomings such as low mechanical strength and poor bioactivity to improve decellularized ECM scaffold towards much more efficient and higher integration.

Hybrid porous zirconia scaffolds fabricated using additive manufacturing for bone tissue engineering applications

For the formation of new bone in critical-sized bone defects, bioactive scaffolds with an interconnected porous network are necessary. Herein, we fabricated three-dimensional (3D) porous hybrid zirconia scaffolds to promote hybrid functionality, i.e., excellent mechanical properties and bioactive performance. Specifically, the 3D printed scaffolds were subjected to Zn-HA/glass composite coating on glass-infiltrated zirconia (ZC). In addition, to pertain the extracellular matrix of bone, biopolymer (alginate/gelatine) was embedded in a developed 3D construct (ZB and ZCB). A zirconia-printed scaffold (Z) group served as a control. The structural and mechanical properties of the constructed scaffolds were studied using essential characterization techniques. Furthermore, the biological performance of the designed scaffolds was tested by a sequence of in vitro cell tests, including the attachment, proliferation, and osteogenic differentiation of dental pulp cells (DPCs). The ZC and ZCB scaffolds exhibited 20% higher compression strength than the zirconia (Z) scaffolds. More importantly, the ZC constructs exhibited superior cell-adhesion, distribution, and osteogenic differentiation ability due to the synergistic effects of the composite coating. In addition, the biopolymer-embedded scaffolds (ZB, ZCB) showed an excellent biological and mechanical performance. Thus, our results suggest that the Zn-HA/glass composite-coated glass-infiltrated zirconia (ZC, ZCB) scaffolds are a dynamic approach to designing bioactive 3D scaffolds for the load-bearing bone regeneration applications.

Strategies for Bone Regeneration: From Graft to Tissue Engineering

Bone is a regenerative organ characterized by self-renewal ability. Indeed, it is a very dynamic tissue subjected to continuous remodeling in order to preserve its structure and function. However, in clinical practice, impaired bone healing can be observed in patients and medical intervention is needed to regenerate the tissue via the use of natural bone grafts or synthetic bone grafts. The main elements required for tissue engineering include cells, growth factors and a scaffold material to support them. Three different materials (metals, ceramics, and polymers) can be used to create a scaffold suitable for bone regeneration. Several cell types have been investigated in combination with biomaterials. In this review, we describe the options available for bone regeneration, focusing on tissue engineering strategies based on the use of different biomaterials combined with cells and growth factors.

[Application status of hypoxia mimetic agents in bone tissue engineering]

Objective

To summarize the application status of hypoxia mimetic agents in bone tissue engineering.

Methods

The related literature about the hypoxia mimetic agents in bone tissue engineering was reviewed and analyzed. And the application status and progress of hypoxia mimetic agents in bone tissue engineering were retrospectively analyzed.

Results

Hypoxia mimetic agents have the same effect as hypoxia in up-regulating the level of hypoxia inducible factor 1α (HIF-1α). The combination of hypoxia mimetic agents and scaffolds can up-regulate the level of HIF-1α in bone tissue engineering, thus promoting early vascularization and bone regeneration of the bone defect area, which provides a new idea for using bone tissue engineering to repair bone defect. At present, the commonly used hypoxia mimetic agents include iron chelating agents, oxoglutarate competitive analogues, proline hydroxylase inhibitors, etc.

Conclusion

Hypoxia mimetic agents have a wide application prospect in bone tissue engineering, but they have been used in bone tissue engineering for a short time, more attention should be paid to their possible side effects. In the future research, the hypoxia mimetic agents should be developed in the direction of higher targeting specificity and safety, and the exact mechanism of hypoxia mimetic agents in promoting bone regeneration should be further explored.

Human Fat-Derived Mesenchymal Stem Cells Xenogenically Implanted in a Rat Model Show Enhanced New Bone Formation in Maxillary Alveolar Tooth Defects

BACKGROUND

Due to restorative concerns, bone regenerative therapies have garnered much attention in the field of human oral/maxillofacial surgery. Current treatments using autologous and allogenic bone grafts suffer from inherent challenges, hence the ideal bone replacement therapy is yet to be found. Establishing a model by which MSCs can be placed in a clinically acceptable bone defect to promote bone healing will prove valuable to oral/maxillofacial surgeons.

METHODS

Human adipose tissue-derived MSCs were seeded onto Gelfoam® and their viability, proliferation, and osteogenic differentiation was evaluated in vitro. Subsequently, the construct was implanted in a rat maxillary alveolar bone defect to assess in vivo bone healing and regeneration.

RESULTS

Human MSCs were adhered, proliferated, and uniformly distributed, and underwent osteogenic differentiation on Gelfoam®, comparable with the tissue culture surface. Data confirmed that Gelfoam® could be used as a scaffold for cell attachment and a delivery vehicle to implant MSCs in vivo. Histomorphometric analyses of bones harvested from rats treated with hMSCs showed statistically significant increase in collagen/early bone formation, with cells positive for osteogenic and angiogenic markers in the defect site. This pattern was visible as early as 4 weeks post treatment.

CONCLUSIONS

Xenogenically implanted human MSCs have the potential to heal an alveolar tooth defect in rats. Gelfoam®, a commonly used clinical biomaterial, can serve as a scaffold to deliver and maintain MSCs to the defect site. Translating this strategy to preclinical animal models provides hope for bone tissue engineering.

3D-porous β-tricalcium phosphate-alginate-gelatin scaffold with DMOG delivery promotes angiogenesis and bone formation in rat calvarial defects

Hypoxia-inducible factor-1α (HIF-1α), a well-studied angiogenesis pathway, plays an essential role in angiogenesis-osteogenesis coupling. Targeting the HIF-1a pathway frequently leads to successful reconstruction of large-sized bone defects through promotion of angiogenesis. Dimethyloxalylglycine (DMOG) small molecule regulates the stability of HIF-1α at normal oxygen tension by mimicking hypoxia, which subsequently accelerates angiogenesis. The current study aims to develop a novel construct by seeding adipose derived mesenchymal stem cells (ADMSCs) onto a scaffold that contains DMOG to induce angiogenesis and regeneration of a critical size calvarial defect in a rat model. The spongy scaffolds have been synthesized in the presence and absence of DMOG and analyzed in terms of morphology, porosity, pore size, mechanical properties and DMOG release profile. The effect of DMOG delivery on cellular behaviors of adhesion, viability, osteogenic differentiation, and angiogenesis were subsequently evaluated under in vitro conditions. Histological analysis of cell-scaffold constructs were also performed following transplantation into the calvarial defect. Physical characteristics of fabricated scaffolds confirmed higher mechanical strength and surface roughness of DMOG-loaded scaffolds. Scanning electron microscopy (SEM) images and MTT assay demonstrated the attachment and viability of ADMSCs in the presence of DMOG, respectively. Osteogenic activity of ADMSCs that included alkaline phosphatase (ALP) activity and calcium deposition significantly increased in the DMOG-loaded scaffold. Computed tomography (CT) imaging combined with histomorphometry and immunohistochemistry analysis showed enhanced bone formation and angiogenesis in the DMOG-loaded scaffolds. Therefore, spongy scaffolds that contained DMOG and had angiogenesis ability could be utilized to enhance bone regeneration of large-sized bone defects.

Mesenchymal Stem Cells of Different Origin-Seeded Bioceramic Construct in Regeneration of Bone Defect in Rabbit

BACKGROUND

Stem cell is currently playing a major role in the treatment of number of incurable diseases via transplantation therapy. The objective of this study was to determine the osteogenic potential of allogenic and xenogenic bone-derived MSC seeded on a hydroxyapatite (HA/TCP) bioceramic construct in critical size bone defect (CSD) in rabbits.

METHODS

A 15 mm long radial osteotomy was performed unilaterally in thirty-six rabbits divided equally in six groups. Bone defects were filled with bioscaffold seeded with autologous, allogenic, ovine, canine BMSCs and cell free bioscaffold block in groups A, B, C, D and E respectively. An empty defect served as the control group.

RESULTS

The radiological, histological and SEM observations depicted better and early signs of new bone formation and bridging bone/implant interfaces in the animals of group A followed by B. Both xenogenous MSC-HA/TCP construct also accelerated the healing of critical sized bone defect. There was no sign of any inflammatory reaction in the xenogenic composite scaffold group of animals confirmed their well acceptance by the host body.

CONCLUSION

In vivo experiments in rabbit CSD model confirmed that autogenous, allogenous and xenogenous BMSC seeded on bioscaffold promoted faster healing of critical size defects. Hence, we may suggest that BMSCs are suitable for bone formation in fracture healing and non-union.

The Challenge in Using Mesenchymal Stromal Cells for Recellularization of Decellularized Cartilage

Some decellularized musculoskeletal extracellular matrices (ECM)s derived from tissues such as bone, tendon and fibrocartilaginous meniscus have already been clinical use for tissue reconstruction. Repair of articular cartilage with its unique zonal ECM architecture and composition is still an unsolved problem, and the question is whether allogenic or xenogeneic decellularized cartilage ECM could serve as a biomimetic scaffold for this purpose.Hence, this survey outlines the present state of preparing decellularized cartilage ECM-derived scaffolds or composites for reconstruction of different cartilage types and of reseeding it particularly with mesenchymal stromal cells (MSCs).The preparation of natural decellularized cartilage ECM scaffolds hampers from the high density of the cartilage ECM and lacking interconnectivity of the rather small natural pores within it: the chondrocytes lacunae. Nevertheless, the reseeding of decellularized ECM scaffolds before implantation provided superior results compared with simply implanting cell-free constructs in several other tissues, but cartilage recellularization remains still challenging. Induced by cartilage ECM-derived scaffolds MSCs underwent chondrogenesis.Major problems to be addressed for the application of cell-free cartilage were discussed such as to maintain ECM structure, natural chemistry, biomechanics and to achieve a homogenous and stable cell recolonization, promote chondrogenic and prevent terminal differentiation (hypertrophy) and induce the deposition of a novel functional ECM. Some promising approaches were proposed including further processing of the decellularized ECM before recellularization of the ECM with MSCs, co-culturing of MSCs with chondrocytes and establishing bioreactor culture e.g. with mechanostimulation, flow perfusion pressure and lowered oxygen tension. Graphical Abstract Synopsis of tissue engineering approaches based on cartilage-derived ECM.

The influence of tissue microenvironment on stem cell-based cartilage repair

Mesenchymal stem/progenitor cells and induced pluripotent stem cells have become viable cell sources for prospective cell-based cartilage engineering and tissue repair. The development and function of stem cells are influenced by the tissue microenvironment. Specifically, the local tissue microenvironment can dictate how stem cells integrate into the existing tissue matrix and how successfully they can restore function to the damaged area in question. This review focuses on the microenvironmental features of articular cartilage and how they influence stem cell-based cartilage tissue repair. Also discussed are current tissue-engineering strategies used in combination with cell-based therapies, all of which are designed to mimic the natural properties of cartilage tissue in order to achieve a better healing response.

Polymer surface interacts with calcium in aqueous media to induce stem cell assembly

Bioinspired surface with functional group rearrangement abilities are highly desirable for designing functional materials. Calcium ion (Ca(2+) ) is a pivotal life element and the ion transport is tightly regulated through calcium channels. It is demonstrated here that Ca(2+) can be transported by polymer surface to induce cell assembly. A series of polyurethane materials is synthesized with different abilities to rearrange the surface functional groups in response to aqueous environment. It is observed that surface recruitment of carboxyl and amino groups from the bulk material can interact with Ca(2+) and facilitate its translocation from aqueous media into cells. The surface rearrangement of functional group triggers the calcium trafficking and turns on signals involving cell merging and assembly. This observation provides an insight on adjusting material-calcium interaction to design nature-inspired smart interfaces to induce cell organization and tissue regeneration.

Calcium Orthophosphate-Containing Biocomposites and Hybrid Biomaterials for Biomedical Applications

The state-of-the-art on calcium orthophosphate (CaPO4)-containing biocomposites and hybrid biomaterials suitable for biomedical applications is presented. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through the successful combinations of the desired properties of matrix materials with those of fillers (in such systems, CaPO4 might play either role), innovative bone graft biomaterials can be designed. Various types of CaPO4-based biocomposites and hybrid biomaterials those are either already in use or being investigated for biomedical applications are extensively discussed. Many different formulations in terms of the material constituents, fabrication technologies, structural and bioactive properties, as well as both in vitro and in vivo characteristics have been already proposed. Among the others, the nano-structurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin, as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using CaPO4-based biocomposites and hybrid biomaterials in the selected applications are highlighted. As the way from a laboratory to a hospital is a long one and the prospective biomedical candidates have to meet many different necessities, the critical issues and scientific challenges that require further research and development are also examined.

Concentrated gelatin/alginate composites for fabrication of predesigned scaffolds with a favorable cell response by 3D plotting

Developed concentrated gelatin/alginate with/without HAP composites were plotted into pre-designed scaffolds, which showed good cells attachments and penetration.

Bone tissue engineering scaffolding: computer-aided scaffolding techniques

Tissue engineering is essentially a technique for imitating nature. Natural tissues consist of three components: cells, signalling systems (e.g. growth factors) and extracellular matrix (ECM). The ECM forms a scaffold for its cells. Hence, the engineered tissue construct is an artificial scaffold populated with living cells and signalling molecules. A huge effort has been invested in bone tissue engineering, in which a highly porous scaffold plays a critical role in guiding bone and vascular tissue growth and regeneration in three dimensions. In the last two decades, numerous scaffolding techniques have been developed to fabricate highly interconnective, porous scaffolds for bone tissue engineering applications. This review provides an update on the progress of foaming technology of biomaterials, with a special attention being focused on computer-aided manufacturing (Andrade et al. 2002) techniques. This article starts with a brief introduction of tissue engineering (Bone tissue engineering and scaffolds) and scaffolding materials (Biomaterials used in bone tissue engineering). After a brief reviews on conventional scaffolding techniques (Conventional scaffolding techniques), a number of CAM techniques are reviewed in great detail. For each technique, the structure and mechanical integrity of fabricated scaffolds are discussed in detail. Finally, the advantaged and disadvantage of these techniques are compared (Comparison of scaffolding techniques) and summarised (Summary).

The effect of dimethyl sulfoxide on hepatic differentiation of mesenchymal stem cells

INTRODUCTION

Adipose tissue-derived mesenchymal stem cells (AT-MSCs) are suitable choices in autologous stem cell treatment of liver-associated diseases due to their hepatic differentiation potential. Dimethyl sulfoxide (DMSO) is an amphipathic molecule with potential of delivering both lipophilic and hydrophilic agents into cells, also a common cryoprotectant for freezing of the cells. DMSO was used in some protocols for induction of AT-MSCs towards hepatocyte like cells. However, the effect of DMSO on hepatogenic differentiation of AT-MSCs were not surveyed, previously. In the present study, we aimed at evaluation of the effect of DMSO on differentiation of AT-MSCs into hepatic lineage.

METHODS

We isolated mesenchymal stem cells (MSCs) from adipose tissue, and then verifies multi-potency and surface markers of AT-MSCs . Isolated AT-MSCs randomly dispensed in four groups including Group 1: HGF treated, 2: HGF+ DMSO treated, 3: HGF+ DMSO+ OSM treated, and group control for a period of 3 weeks in the expansion medium without serum; EGF and bFGF were also included in the first days of inductions. The morphologic changes during induction period was observed with microscopy. The secretion of albumin (ALB) of the differentiating MSCs was investigated using ELISA, and urea production was evaluated using colorimetric assay. The qRT-PCR was performed for quantitation of hepatocyte marker genes including AFP, ALB, CK18, HNF4a, and HNF6. The glycogen storage of differentiated cells was visualized by periodic-acid Schiff‘s staining.

RESULTS

The results demonstrate that DMSO speeds up hepatic differentiation of AT-MSCs characterized by rapid changes in morphology; higher expression of hepatic marker gene (ALB) in both mRNA and protein level (P < 0.05); also increased transcriptional levels of other liver genes including CK18, HNF4a, and HNF6 (P < 0.01); and moreover, greater percentage of glycogen storage(p < 0.05) in DMSO-treated groups.

CONCLUSION

DMSO catalyzes hepatic differentiation; therefore, using DMSO for acceleration of the hepatogenic protocols of AT-MSCs appears advantageous.

Comprehensive characterization of four different populations of human mesenchymal stem cells as regards their immune properties, proliferation and differentiation

In the present study, we compared mesenchymal stem cells (MSCs) derived from 4 different sources, human bone marrow (BM), adipose tissue (AT), umbilical cord Wharton's Jelly (WJ) and the placenta (PL), in order to determine which population of MSCs displayed the most prominent immunosuppressive effects on phytohemagglutinin-induced T cell proliferation, and which one had the highest proliferative and differentiation potential. MSC and T lymphocyte co-culture (mixed culture) was used to determine whether the MSCs inhibit T cell proliferation, as well as which population of MSCs has the strongest inhibitory ability. The expression of immune-related genes was analyzed by RT-PCR and RT-qPCR. The proliferation and differentiation potential of the MSCs were determined using standard methods. Following MSC and T cell co-culture, mitogen-induced T cell proliferation was effectively suppressed by all 4 populations of MSCs. This occurred through soluble factors rather than direct contact inhibition. Among the 4 populations of MSCs, the WJ-MSC has the strongest suppression effects. On immune related genes, WJ-MSC has the weakest expression of MHC II genes, TLR4, TLR3, JAG1, NOTCH2 and NOTCH3. To compare the proliferation potential, WJ-MSCs showed the most rapid growth rate followed by the AT-, PL- and BM-MSCs. As regards differentiation potential, the WJ-MSCs had the strongest osteogenetic ability followed by PL, AT and BM-MSC. AT-MSC has the strongest adipogenetic ability followed by the WJ-, BM- and PL-MSCs. These data indicated that the WJ-MSCs had the strongest immunomodulatory and immunosuppressive potential. In light of these observations, we suggest that WJ-MSCs are the most attractive cell population for use in immune cellular therapy when immunosuppressive action is required.

Calcium phosphate ceramics in bone tissue engineering: a review of properties and their influence on cell behavior

Calcium phosphate ceramics (CPCs) have been widely used as biomaterials for the regeneration of bone tissue because of their ability to induce osteoblastic differentiation in progenitor cells. Despite the progress made towards fabricating CPCs possessing a range of surface features and chemistries, the influence of material properties in orchestrating cellular events such as adhesion and differentiation is still poorly understood. Specifically, questions such as why certain CPCs may be more osteoinductive than others, and how material properties contribute to osteoinductivity/osteoconductivity remain unanswered. Therefore, this review article systematically discusses the effects of the physical (e.g. surface roughness) and chemical properties (e.g. solubility) of CPCs on protein adsorption, cell adhesion and osteoblastic differentiation in vitro. The review also provides a summary of possible signaling pathways involved in osteoblastic differentiation in the presence of CPCs. In summary, these insights on the contribution of material properties towards osteoinductivity and the role of signaling molecules involved in osteoblastic differentiation can potentially aid the design of CPC-based biomaterials that support bone regeneration without the need for additional biochemical supplements.

Scaffold/Extracellular matrix hybrid constructs for bone-tissue engineering

The limited natural ability of the body to fully repair large bone defects often necessitates the implantation of a replacement material to promote healing. While the current clinical strategies to address such bone defects generally carry associated limitations, bone-tissue engineering approaches seek to minimize any adverse effects and facilitate complete regeneration of the lost tissue. Of particular interest are hybrid constructs that incorporate multiple components found within the native bone matrix to enhance the osteogenicity of biocompatible materials, which might otherwise be non-osteogenic. This Progress Report will focus on such hybrid constructs that incorporate multiple components from native bone matrix for bone-tissue engineering and will highlight the synthesis and characterization of the hybrid constructs, cellular attachment and proliferation within the constructs, in vitro osteogenicity of the constructs, and the biological response to in vivo implantation of the constructs at ectopic and orthotopic sites.

Bone tissue engineering using bone marrow stromal cells and an injectable sodium alginate/gelatin scaffold

To investigate the potential application of bone marrow stromal cells (BMSCs) and an injectable sodium alginate/gelatin scaffold for bone tissue engineering (BTE). The phenotype of osteogenic BMSCs was examined by mineralized nodules formation and type I collagen expression. Cell proliferation was evaluated by MTT assay. The biocompatibility of scaffold and osteogenic cells were examined by hematoxylin and eosin (H&E) staining. Ectopic bone formation as well as closure of rabbit calvarial critical-sized defects following scaffold-cell implantation were analyzed by histological examination and computed tomography (CT) scanning. Spindle-shaped osteogenic cells of high purity were derived from BMSCs. The osteogenic cells and sodium alginate/gelatin (2:3) scaffold presented fine biocompatibility following cross-linking with 0.6% of CaCl(2). After implantation, the scaffold-cell construct promoted both ectopic bone formation and bone healing in the rabbit calvarial critical-sized defect model. Our data demonstrated that the sodium alginate/gelatin scaffold could be a suitable biomaterial for bone engineering, and the scaffold-osteogenic cells construct is a promising alternative approach for the bone healing process.

Biocomposites and hybrid biomaterials based on calcium orthophosphates

The state-of-the-art of biocomposites and hybrid biomaterials based on calcium orthophosphates that are suitable for biomedical applications is presented in this review. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through successful combinations of the desired properties of matrix materials with those of fillers (in such systems, calcium orthophosphates might play either role), innovative bone graft biomaterials can be designed. Various types of biocomposites and hybrid biomaterials based on calcium orthophosphates, either those already in use or being investigated for biomedical applications, are extensively discussed. Many different formulations, in terms of the material constituents, fabrication technologies, structural and bioactive properties as well as both in vitro and in vivo characteristics, have already been proposed. Among the others, the nanostructurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using biocomposites and hybrid biomaterials based on calcium orthophosphates in the selected applications are highlighted. As the way from the laboratory to the hospital is a long one, and the prospective biomedical candidates have to meet many different necessities, this review also examines the critical issues and scientific challenges that require further research and development.

Coupling of gelatin to inner surfaces of pore walls in spongy alginate-based scaffolds facilitates the adhesion, growth and differentiation of human bone marrow mesenchymal stromal cells

We have developed a novel wide-pore scaffold for cell 3D culturing, based on the technology of freeze-drying of Ca-alginate and gelatin. Two different preparation methodologies were compared: (i) freeze-drying of Na-alginate + gelatin mixed solution followed by the incubation of dried polymer in saturated ethanolic solution of CaCl₂; (ii) freeze-drying of the Na-alginate solution followed by the chemical "activation" of polysaccharide core with divinylsulfone with subsequent gelatin covalent attachment to the inner surfaces of pore walls. The scaffolds produced using the first approach did not provide adhesion and proliferation of human bone marrow mesenchymal stromal cells (MSCs). Conversely, the second approach allowed to obtain scaffolds with a high adherence ability for the cells. When cultured within the latter type of scaffold, MSCs proliferated and were able to differentiate into adipogenic, osteogenic and chondrogenic cell lineages, in response to specific induction stimuli. The results indicate that Ca-alginate wide-pore scaffolds with covalently attached gelatin could be useful for stem cell-based bone, cartilage and adipose tissue engineering.

Expansion and preservation of multipotentiality of rabbit bone-marrow derived mesenchymal stem cells in dextran-based microcarrier spin culture

The use of mesenchymal stem cells (MSCs) in tissue repair and regeneration despite their multipotentiality has been limited by their cell source quantity and decelerating proliferative yield efficiency. A study was thus undertaken to determine the feasibility of using microcarrier beads in spinner flask cultures for MSCs expansion and compared to that of conventional monolayer cultures and static microcarrier cultures. Isolation and characterization of bone marrow derived MSCs were conducted from six adult New Zealand white rabbits. Analysis of cell morphology on microcarriers and culture plates at different time points (D0, D3, D10, D14) during cell culture were performed using scanning electron microscopy and bright field microscopy. Cell proliferation rates and cell number were measured over a period of 14 days, respectively followed by post-expansion characterization. MTT proliferation assay demonstrated a 3.20 fold increase in cell proliferation rates in MSCs cultured on microcarriers in spinner flask as compared to monolayer cultures (p < 0.05). Cell counts at day 14 were higher in those seeded on stirred microcarrier cultures (6.24 ± 0.0420 cells/ml) × 10(5) as compared to monolayer cultures (0.22 ± 0.004 cells/ml) × 10(5) and static microcarrier cultures (0.20 ± 0.002 cells/ml) × 10(5). Scanning electron microscopy demonstrated an increase in cell colonization of the cells on the microcarriers in stirred cultures. Bead-expanded MSCs were successfully differentiated into osteogenic and chondrogenic lineages. This system offers an improved and efficient alternative for culturing MSCs with preservation to their phenotype and multipotentiality.

Autologous mesenchymal stem cells loaded in Gelfoam(®) for structural bone allograft healing in rabbits

This study was designed to evaluate the effect of autologous bone marrow mesenchymal stem cells (MSCs) seeded into Gelfoam® on structural bone allograft healing. Thirty New Zealand white rabbits were divided into two groups. Segmental bone defect was created on diaphysis of the femur, and the defect was reconstructed with structural bone allograft. In experimental group, structural allograft was wrapped around by Gelfoam® containing autologous MSCs, whereas cells were not included in control group. At 4, 8, 12 weeks, the femur of rabbits underwent radiographic and histologic evaluation for bony union. Bone morphogenic protein-2 (BMP-2), BMP-4, BMP-7, vascular endothelial growth factor (VEGF), and receptor activator of nuclear factor-kappa B ligand (RANKL) were measured within the grafted periosteal tissue. Bony union was not achieved in both groups at 4 and 8 weeks. At 12 weeks, three out of five femurs in experimental group were united, but one out of five in control group was united. Mean Taira scores were significantly different between two groups. The expression of BMP-2 was significantly higher at 4, 8 weeks, the expressions of BMP-4 and BMP-7 were significantly higher at 8 and 12 weeks, and the expression of VEGF and RANKL were significantly higher at all time points in experimental group. Incorporation of the structural bone allograft could be enhanced if allograft is covered with Gelfoam® containing autologous MSCs. MSCs have influence on not only bone formation, but neo-angiogenesis, and bone resorption.

Biocompatibility evaluation of nano-rod hydroxyapatite/gelatin coated with nano-HAp as a novel scaffold using mesenchymal stem cells

This study is devoted to fabricate a novel hydroxyapatite(HAp)/gelatin scaffold coated with nano-HAp in nano-rod configuration to evaluate its biocompatibility potential. The nano-HAp particles are needle and rod-like with widths ranging between 30 to 60 nm and lengths from 100 to 300 nm, respectively. Because of their higher surface area and higher reactivity, the nano-rod particles were distributed in gelatin much better than spherical and mixed shapes particles. The compressive modulus of the nano-HAp/gelatin scaffolds coated with nano-HAp was comparable with the compressive modulus of a human cancellous bone. The potential performance of the fabricated scaffolds as seeding media was assayed using mesenchymal stem cells (MSCs). MTT (3-(4,5-dimethylthiazol-2-yl)-1,5-diphenyl tetrazulium bromide) assays were performed on days 4 and 7 and the number of the cells per scaffold was determined. On the basis of this assay, all the studied scaffolds exhibited an appropriate environment in which the loaded cells appeared to be proliferated during the cultivation periods. In all fabricated composite scaffolds, marrow-derived MSCs appeared to occupy the scaffolds internal spaces and attach on their surfaces. According to the cell culture experiments, the incorporation of rod-like nano-HAp and coating of scaffolds with nano-HAp particles enabled the prepared scaffolds to possess desirable biocompatibility, high bioactivity, and sufficient mechanical strength in comparison with noncoated HAp samples. This research suggests that the newly developed scaffold has a potential as a suitable scaffold for bone tissue engineering.

Type I collagen gel in seeding medium improves murine mesencymal stem cell loading onto the scaffold, increases their subsequent proliferation, and enhances culture mineralization

Collagen I as a major organic component of bone matrix may be important for establishment and maintenance of mesenchymal stem cells (MSCs) in osteogenic 3D culture. To explore this subject, murine marrow-derived MSCs were seeded onto hybrid scaffolds of alginate/gelatin/beta-tricalcium phosphate in a medium either with or without collagen I gel. The cultures were then provided with osteogenic medium and incubated for three weeks during which loading efficiency, cell proliferation and the culture mineralization were quantified and statistically compared. According to the findings, in culture with collagen, although about 60% of the cells left the scaffolds, the remaining cells, however, proliferated extensively with a population doubling number (PDN) equivalent to 2.46 +/- 0.31 and organized as cell aggregations that were heavily mineralized (calcium concentration = 1.017 +/- 0.141 mM per scaffold), whereas in the culture without collagen, about 75% of the cells left the scaffolds, less cell proliferation occurred (PDN = 1.48 +/- 0.29) and no cell aggregation was observed. The calcium concentration in this culture was 0.185 +/- 0.029 mM per scaffold. All these differences were statistically significant (p < 0.001). Taken together, these data suggested that using the collagen I in seeding medium could help mMSCs loading into the scaffold, enhance their subsequent proliferation, and increase calcium deposition in 3D culture system.

Characterization of mesenchymal stem cells from rat bone marrow: ultrastructural properties, differentiation potential and immunophenotypic markers

Bone marrow-derived mesenchymal stem cells (BM-MSCs) can differentiate into many lineages. Although the growing interest in BM-MSCs has led to a number of characterization studies, some important biochemical and immunohistochemical properties are still lacking. In this study, morphological and immunophenotypic properties of BM-MSCs were examined in detail. Differentiation potential and growth kinetics of adult rat BM-MSCs were also determined. Immunohistochemistry and RT-PCR results indicated that BM-MSCs expressed myogenic (desmin, myogenin, myosin IIa, and alpha-SMA), neurogenic (gamma-enolase, MAP2a,b, c-fos, nestin, GFAP and beta III tubulin), and osteogenic (osteonectin, osteocalcin, osteopontin, Runx-2, BMP-2, BMP-4 and type I collagen) markers without stimulation towards differentiation. These expression patterns indicated why these cells can easily differentiate into multiple lineages both in vitro and in vivo. Ultrastructural characteristics of rBM-MSCs showed more developed and metabolically active cells.

Proliferation and osteogenic differentiation of human bone marrow stromal cells on alginate-gelatine-hydroxyapatite scaffolds with anisotropic pore structure

Porous mineralized scaffolds are required for various applications in bone engineering. In particular, tube-like pores with controlled orientation inside the scaffold may support homogeneous cell seeding as well as sufficient nutrient supply and may facilitate blood vessel ingrowth. Scaffolds with parallely orientated tube-like pores were generated by diffusion-controlled ionotropic gelation of alginate. Incorporation of hydroxyapatite (HA) during the gelation process yielded stable scaffolds with an average pore diameter of approximately 90 microm. To evaluate the potential use of alginate-gelatine-HA scaffolds for bone tissue engineering, in vitro tests with human bone marrow stromal cells (hBMSCs) were carried out. We analysed biocompatibility and cell penetration into the capillary pores by microscopic methods. hBMSCs were also cultivated on alginate-gelatine-HA scaffolds for 3 weeks in the presence and absence of osteogenic supplements. We studied proliferation and osteogenic differentiation in terms of total lactate dehydrogenase (LDH) activity, DNA content and alkaline phosphatase (ALP) activity and found a 10-14-fold increase of cell number after 2 weeks of cultivation, as well as an increase of specific ALP activity for osteogenic-induced hBMSCs. Furthermore, the expression of bone-related genes [ALP, bone sialoprotein II (BSPII)] was analysed. We found an increase of ALP as well as BSPII expression for osteogenic-induced hBMSCs on alginate-gelatin-HA scaffolds.