Beta-tricalcium phosphate 3D scaffold promote alone osteogenic differentiation of human adipose stem cells: in vitro study

Adipose-Derived Mesenchymal Stem Cell Osteodifferentiation after Exposure to Beta-Tricalcium Phosphate Bioceramic Granules with 300 to 600 and 600 to 1,000 µm Sizes

Beta-tricalcium phosphate (β-TCP) is a synthetic graft material with excellent biocompatibility, osteoconductivity, and osteoinductivity. β-TCP may induce adipose-derived mesenchymal stem cells (ADMSCs) osteodifferentiation. This study aims to investigate the osteoinductivity of 300 to 600 and 600 to 1,000μm β-TCP in ADMSCs.ADMSCs were obtained from the visceral adipose tissue of young male rabbits. To determine the osteoinductive ability, bone morphogenic protein 2 (BMP-2), Osterix, runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), osteopontin, and osteonectin expression was examined using an immunochemical assay on ADMSCs conditioned with an osteogenic medium and a β-TCP bioceramic with granule sizes of 300 to 600 and 600 to 1,000 µm (100 ng diluted to 100 nmol as the final concentration). A 3,3'-diaminobenzidine staining kit was used for immunocytochemical staining. Anti-BMP-2, anti-Osterix, anti-Runx2, anti-ALP, anti-osteopontin, and anti-osteonectin monoclonal antibodies were employed at a 1:500 dilution. A light microscope with magnifications of 400× and 1,000× was used to manually observe and examine cultures in five different fields of view.BMP 2, Runx2, Osterix, and ALP expression was higher in ADMSCs + β-TCP 300 to 600 µm compared with the control group (p < 0.05). Osteonectin and osteopontin expression was higher in ADMSCs + 300 to 600 µm β-TCP compared with the control group (p < 0.05) and ADMSCs + 600 to 1,000 µm β-TCP (p < 0.05).ADMSC osteodifferentiation was influenced by β-TCP bioceramic granule size. The considerable difference in osteonectin and osteopontin expression supports the idea that 300 to 600 µm β-TCP induce ADMSCs osteodifferentiation than 600 to 1,000 µm β-TCP.

Hydroxyapatite-filled osteoinductive and piezoelectric nanofibers for bone tissue engineering

Osteoporotic-related fractures are among the leading causes of chronic disease morbidity in Europe and in the US. While a significant percentage of fractures can be repaired naturally, in delayed-union and non-union fractures surgical intervention is necessary for proper bone regeneration. Given the current lack of optimized clinical techniques to adequately address this issue, bone tissue engineering (BTE) strategies focusing on the development of scaffolds for temporarily replacing damaged bone and supporting its regeneration process have been gaining interest. The piezoelectric properties of bone, which have an important role in tissue homeostasis and regeneration, have been frequently neglected in the design of BTE scaffolds. Therefore, in this study, we developed novel hydroxyapatite (HAp)-filled osteoinductive and piezoelectric poly(vinylidene fluoride-co-tetrafluoroethylene) (PVDF-TrFE) nanofibers via electrospinning capable of replicating the tissue's fibrous extracellular matrix (ECM) composition and native piezoelectric properties. The developed PVDF-TrFE/HAp nanofibers had biomimetic collagen fibril-like diameters, as well as enhanced piezoelectric and surface properties, which translated into a better capacity to assist the mineralization process and cell proliferation. The biological cues provided by the HAp nanoparticles enhanced the osteogenic differentiation of seeded human mesenchymal stem/stromal cells (MSCs) as observed by the increased ALP activity, cell-secreted calcium deposition and osteogenic gene expression levels observed for the HAp-containing fibers. Overall, our findings describe the potential of combining PVDF-TrFE and HAp for developing electroactive and osteoinductive nanofibers capable of supporting bone tissue regeneration.

Advancements and Utilizations of Scaffolds in Tissue Engineering and Drug Delivery

The drug development process requires a thorough understanding of the scaffold and its three-dimensional structure. Scaffolding is a technique for tissue engineering and the formation of contemporary functioning tissues. Tissue engineering is sometimes referred to as regenerative medicine. They also ensure that drugs are delivered with precision. Information regarding scaffolding techniques, scaffolding kinds, and other relevant facts, such as 3D nanostructuring, are discussed in depth in this literature. They are specific and demonstrate localized action for a specific reason. Scaffold's acquisition nature and flexibility make it a new drug delivery technology with good availability and structural parameter management.

The Role of Extracellular Vesicles Secreted From Thermal Stress-Induced Adipose-Derived Stem Cells on Bone Regeneration

PURPOSE

Extracellular vesicles (EVs) are responsible for intercellular communication. Mesenchymal stem cell-derived vesicles have been shown to have similar properties as functional mesenchymal stem cells. The aim of this study was to compare the therapeutic benefit of EVs obtained from adipose tissue-derived stem cells (ADSC) on bone repair whereas using ß-tricalcium phosphate (ß-TCP) biomaterial as a carrier.

MATERIALS AND METHOD

A single critical size bone defect of 8 mm in diameter was created on the right side of rat calvarium using a custom-made punch needle. Animals were randomly divided into 5 groups: group 1 (no treatment), group 2 (bone graft), group 3 (ß-TCP + ADSC), group 4 (ß-TCP + EV), group 5 (ß-TCP). Eight weeks later, animals were sacrificed and histologic and radiologic evaluation was performed.

RESULTS

Semiquantitative histologic scoring demonstrated significantly higher bone regeneration scores for groups 2, 3, and 4 compared to group 1. Radiologic imaging showed significantly higher bone mineral density for groups 2, 3, and 5 compared to group 1. There were no significant differences between treatment groups in either histologic or radiologic scoring.

CONCLUSIONS

Our data showed that EVs provided from thermally induced ADSCs did not show any significant difference in bone regeneration when compared to ADSCs themselves. Future studies should focus on determining the optimum amount and content of EV application since these vary significantly depending on the microenvironment.

Advancing bioinks for 3D bioprinting using reactive fillers: A review

The growing demand for personalized implants and tissue scaffolds requires advanced biomaterials and processing strategies for the fabrication of three-dimensional (3D) structures mimicking the complexity of the extracellular matrix. During the last years, biofabrication approaches like 3D printing of cell-laden (soft) hydrogels have been gaining increasing attention to design such 3D functional environments which resemble natural tissues (and organs). However, often these polymeric hydrogels show poor stability and low printing fidelity and hence various approaches in terms of multi-material mixtures are being developed to enhance pre- and post-printing features as well as cytocompatibility and post-printing cellular development. Additionally, bioactive properties improve the binding to the surrounding (host) tissue at the implantation site. In this review we focus on the state-of-the-art of a particular type of heterogeneous bioinks, which are composed of polymeric hydrogels incorporating inorganic bioactive fillers. Such systems include isotropic and anisotropic silicates like bioactive glasses and nanoclays or calcium-phosphates like hydroxyapatite (HAp), which provide in-situ crosslinking effects and add extra functionality to the matrix, for example mineralization capability. The present review paper discusses in detail such bioactive composite bioink systems based on the available literature, revealing that a great variety has been developed with substantially improved bioprinting characteristics, in comparison to the pure hydrogel counterparts, and enabling high viability of printed cells. The analysis of the results of the published studies demonstrates that bioactive fillers are a promising addition to hydrogels to print stable 3D constructs for regeneration of tissues. Progress and challenges of the development and applications of such composite bioink approaches are discussed and avenues for future research in the field are presented. STATEMENT OF SIGNIFICANCE: Biofabrication, involving the processing of biocompatible hydrogels including cells (bioinks), is being increasingly applied for developing complex tissue and organ mimicking structures. A variety of multi-material bioinks is being investigated to bioprint 3D constructs showing shape stability and long-term biological performance. Composite hydrogel bioinks incorporating inorganic bioreactive fillers for 3D bioprinting are the subject of this review paper. Results reported in the literature highlight the effect of bioactive fillers on bioink properties, printability and on cell behavior during and after printing and provide important information for optimizing the design of future bioinks for biofabrication, exploiting the extra functionalities provided by inorganic fillers. Further functionalization with drugs/growth factors can target enhanced printability and local drug release for more specialized biomedical therapies.

Indirect selective laser sintering-printed microporous biphasic calcium phosphate scaffold promotes endogenous bone regeneration via activation of ERK1/2 signaling

The fabrication technique determines the physicochemical and biological properties of scaffolds, including the porosity, mechanical strength, osteoconductivity, and bone regenerative potential. Biphasic calcium phosphate (BCP)-based scaffolds are superior in bone tissue engineering due to their suitable physicochemical and biological properties. We developed an indirect selective laser sintering (SLS) printing strategy to fabricate 3D microporous BCP scaffolds for bone tissue engineering purposes. The green part of the BCP scaffold was fabricated by SLS at a relevant low temperature in the presence of epoxy resin (EP), and the remaining EP was decomposed and eliminated by a subsequent sintering process to obtain the microporous BCP scaffolds. Physicochemical properties, cell adhesion, biocompatibility, in vitro osteogenic potential, and rabbit critical-size cranial bone defect healing potential of the scaffolds were extensively evaluated. This indirect SLS printing eliminated the drawbacks of conventional direct SLS printing at high working temperatures, i.e. wavy deformation of the scaffold, hydroxyapatite decomposition, and conversion of β-tricalcium phosphate (TCP) to α-TCP. Among the scaffolds printed with various binder ratios (by weight) of BCP and EP, the scaffold with 50/50 binder ratio (S4) showed the highest mechanical strength and porosity with the smallest pore size. Scaffold S4 showed the highest effect on osteogenic differentiation of precursor cells in vitro, and this effect was ERK1/2 signaling-dependent. Scaffold S4 robustly promoted precursor cell homing, endogenous bone regeneration, and vascularization in rabbit critical-size cranial defects. In conclusion, BCP scaffolds fabricated by indirect SLS printing maintain the physicochemical properties of BCP and possess the capacity to recruit host precursor cells to the defect site and promote endogenous bone regeneration possibly via the activation of ERK1/2 signaling.

Multimaterial Dual Gradient Three-Dimensional Printing for Osteogenic Differentiation and Spatial Segregation

In this study of three-dimensional (3D) printed composite β-tricalcium phosphate (β-TCP)-/hydroxyapatite/poly(ɛ-caprolactone)-based constructs, the effects of vertical compositional ceramic gradients and architectural porosity gradients on the osteogenic differentiation of rabbit bone marrow-derived mesenchymal stem cells (MSCs) were investigated. Specifically, three different concentrations of β-TCP (0, 10, and 20 wt%) and three different porosities (33% ± 4%, 50% ± 4%, and 65% ± 3%) were examined to elucidate the contributions of chemical and physical gradients on the biochemical behavior of MSCs and the mineralized matrix production within a 3D culture system. By delaminating the constructs at the gradient transition point, the spatial separation of cellular phenotypes could be specifically evaluated for each construct section. Results indicated that increased concentrations of β-TCP resulted in upregulation of osteogenic markers, including alkaline phosphatase activity and mineralized matrix development. Furthermore, MSCs located within regions of higher porosity displayed a more mature osteogenic phenotype compared to MSCs in lower porosity regions. These results demonstrate that 3D printing can be leveraged to create multiphasic gradient constructs to precisely direct the development and function of MSCs, leading to a phenotypic gradient. Impact Statement In this study, three-dimensional (3D) printed ceramic/polymeric constructs containing discrete vertical gradients of both composition and porosity were fabricated to precisely control the osteogenic differentiation of mesenchymal stem cells. By making simple alterations in construct architecture and composition, constructs containing heterogenous populations of cells were generated, where gradients in scaffold design led to corresponding gradients in cellular phenotype. The study demonstrates that 3D printed multiphasic composite constructs can be leveraged to create complex heterogeneous tissues and interfaces.

The poly (l-lactid-co-glycolide; PLGA) fiber component of brushite-forming calcium phosphate cement induces the osteogenic differentiation of human adipose tissue-derived stem cells

A brushite-forming calcium phosphate cement (CPC) was mechanically stabilized by addition of poly (l-lactid-co-glycolide; PLGA) fibers (≤10% w/w). It proved highly biocompatible and its fiber component enhanced bone formation in a sheep lumbar vertebroplasty model. However, possible effects on the osteogenic differentiation of resident mesenchymal stem cells (MSCs) remained unexplored. The present study used a novel approach, simultaneously analyzing the influence of a solid CPC scaffold and its relatively low PLGA proportion (a mimicry of natural bone) on osteogenic, chondrogenic, and adipogenic differentiation, as well as the pluripotency of human adipose tissue-derived mesenchymal stem cells (hASCs). hASCs were cultured on CPC discs with/without PLGA fibers (5% and 10%) in the absence of osteogenic medium for 3, 7, and 14 d. Gene expression of osteogenic markers (Runx2, osterix, alkaline phosphatase, collagen I, osteonectin, osteopontin, osteocalcin), chondrogenic markers (collagen II, Sox9, aggrecan), adipogenic markers (PPARG, Leptin, and FABP4), and pluripotency markers (Nanog, Tert, Rex) was analyzed by RT-PCR. The ability of hASCs to synthesize alkaline phosphatase was also evaluated. Cell number and viability were determined by fluorescein diacetate/propidium iodide staining. Compared to pure CPC, cultivation of hASCs on fiber-reinforced CPC transiently induced the gene expression of Runx2 and osterix (day 3), and long-lastingly augmented the expression of alkaline phosphatase (and its enzyme activity), collagen I, and osteonectin (until day 14). In contrast, augmented expression of all chondrogenic, adipogenic, and pluripotency markers was limited to day 3, followed by significant downregulation. Cultivation of hASCs on fiber-reinforced CPC reduced the cell number, but not the proportion of viable cells (viability > 95%). The PLGA component of fiber-reinforced, brushite-forming CPC supports long-lasting osteogenic differentiation of hASCs, whereas chondrogenesis, adipogenesis, and pluripotency are initially augmented, but subsequently suppressed. In view of parallel animal results, PLGA fibers may represent an interesting clinical target for future improvement of CPC- based bone regeneration.

hPL promotes osteogenic differentiation of stem cells in 3D scaffolds

Human platelet lysate (hPL) has been considered as the preferred supplement for the xeno-free stem cell culture for many years. However, the biological effect of hPL on the proliferation and differentiation of dental stem cells combined with the use of medical grade synthetic biomaterial is still under investigation. Thus, the optimal scaffold composition, cell type and specific growth conditions, yet need to be formulated. In this study, we aimed to investigate the regenerative potential of dental stem cells seeded on synthetic scaffolds and maintained in osteogenic media supplemented with either hPL or xeno-derived fetal bovine serum (FBS). Two types of dental stem cells were isolated from human impacted third molars and intact teeth; stem cells of apical papilla (SCAP) and periodontal ligament stem cells (PDLSCs). Cells were expanded in cell culture media supplemented with either hPL or FBS. Consequently, proliferative capacity, immunophenotypic characteristics and multilineage differentiation potential of the derived cells were evaluated on monolayer culture (2D) and on synthetic scaffolds fabricated from poly ’lactic-co-glycolic’ acid (PLGA) (3D). The functionality of the induced cells was examined by measuring the concentration of osteogenic markers ALP, OCN and OPN at different time points. Our results indicate that the isolated dental stem cells showed similar mesenchymal characteristics when cultured on hPL or FBS-containing culture media. Scanning electron microscopy (SEM) and H&E staining revealed the proper adherence of the derived cells on the 3D scaffold cultures. Moreover, the increase in the concentration of osteogenic markers proved that hPL was able to produce functional osteoblasts in both culture conditions (2D and 3D), in a way similar to FBS culture. These results reveal that hPL provides a suitable substitute to the animal-derived serum, for the growth and functionality of both SCAP and PDLSCs. Thus the use of hPL, in combination with PLGA scaffolds, can be useful in future clinical trials for dental regeneration.

Physical Stimulations for Bone and Cartilage Regeneration

A wide range of techniques and methods are actively invented by clinicians and scientists who are dedicated to the field of musculoskeletal tissue regeneration. Biological, chemical, and physiological factors, which play key roles in musculoskeletal tissue development, have been extensively explored. However, physical stimulation is increasingly showing extreme importance in the processes of osteogenic and chondrogenic differentiation, proliferation and maturation through defined dose parameters including mode, frequency, magnitude, and duration of stimuli. Studies have shown manipulation of physical microenvironment is an indispensable strategy for the repair and regeneration of bone and cartilage, and biophysical cues could profoundly promote their regeneration. In this article, we review recent literature on utilization of physical stimulation, such as mechanical forces (cyclic strain, fluid shear stress, etc.), electrical and magnetic fields, ultrasound, shock waves, substrate stimuli, etc., to promote the repair and regeneration of bone and cartilage tissue. Emphasis is placed on the mechanism of cellular response and the potential clinical usage of these stimulations for bone and cartilage regeneration.

Suspended polyhydroxyalkanoate microspheres as 3D carriers for mammalian cell growth

Different forms of biopolyester PHBVHHx microspheres were prepared so as to compare the mammalian cell behaviors in suspension cultivation system. Based on a microbial terpolyester PHBVHHx consisting of 3-hydroxybutyrate (HB), 3-hydroxyvalerate (HV), and 3-hydroxyhexanoate (HHx), solid microspheres (SMSs), hollow microspheres (HMSs), and porous microspheres (PMS) were successfully prepared by a modified solvent evaporation method involving gas-in-oil-in-water (G1/O/W2) double emulsion, water-in-oil-in-water (W1/O/W2) double emulsion and oil-in-water (O/W) single emulsion, respectively. Generally, PMSs have diameters ranging from 330 to 400 μm with pore sizes of 10 to 60 μm. The pores inside the PMSs were found well interconnected compared with PHBVHHx prepared by the traditional solvent evaporation method, resulting in the highest water uptake ratio. When inoculated with human osteoblast-like cells lasting 6 days, PMS showed much better cell attachment and proliferation compared with other less porous microspheres due to its large inner space as a 3 D carrier. Cell migration towards surface and other interconnected inner pores was clearly observable. Dead or apoptotic cells were found more common among less porous SMSs or HMSs compared with highly porous PMSs. It is therefore concluded that porous PHBVHHx microspheres with larger surface open pores and interconnected inner pores can serve as a carrier or scaffold supporting more and better cell growth for either injectable purposes or simply supporting cell growth.

The material and biological characteristics of osteoinductive calcium phosphate ceramics

The discovery of osteoinductivity of calcium phosphate (Ca-P) ceramics has set an enduring paradigm of conferring biological regenerative activity to materials with carefully designed structural characteristics. The unique phase composition and porous structural features of osteoinductive Ca-P ceramics allow it to interact with signaling molecules and extracellular matrices in the host system, creating a local environment conducive to new bone formation. Mounting evidence now indicate that the osteoinductive activity of Ca-P ceramics is linked to their physicochemical and three-dimensional structural properties. Inspired by this conceptual breakthrough, many laboratories have shown that other materials can be also enticed to join the rank of tissue-inducing biomaterials, and besides the bones, other tissues such as cartilage, nerves and blood vessels were also regenerated with the assistance of biomaterials. Here, we give a brief historical recount about the discovery of the osteoinductivity of Ca-P ceramics, summarize the underlying material factors and biological characteristics, and discuss the mechanism of osteoinduction concerning protein adsorption, and the interaction with different types of cells, and the involvement of the vascular and immune systems.

Orthopedic tissue regeneration: cells, scaffolds, and small molecules

Orthopedic tissue regeneration would benefit the aging population or patients with degenerative bone and cartilage diseases, especially osteoporosis and osteoarthritis. Despite progress in surgical and pharmacological interventions, new regenerative approaches are needed to meet the challenge of creating bone and articular cartilage tissues that are not only structurally sound but also functional, primarily to maintain mechanical integrity in their high load-bearing environments. In this review, we discuss new advances made in exploiting the three classes of materials in bone and cartilage regenerative medicine--cells, biomaterial-based scaffolds, and small molecules--and their successes and challenges reported in the clinic. In particular, the focus will be on the development of tissue-engineered bone and cartilage ex vivo by combining stem cells with biomaterials, providing appropriate structural, compositional, and mechanical cues to restore damaged tissue function. In addition, using small molecules to locally promote regeneration will be discussed, with potential approaches that combine bone and cartilage targeted therapeutics for the orthopedic-related disease, especially osteoporosis and osteoarthritis.

Comparison of Osteogenesis between Adipose-Derived Mesenchymal Stem Cells and Their Sheets on Poly-ε-Caprolactone/β-Tricalcium Phosphate Composite Scaffolds in Canine Bone Defects

Multipotent mesenchymal stem cells (MSCs) and MSC sheets have effective potentials of bone regeneration. Composite polymer/ceramic scaffolds such as poly-ε-caprolactone (PCL)/β-tricalcium phosphate (β-TCP) are widely used to repair large bone defects. The present study investigated the in vitro osteogenic potential of canine adipose-derived MSCs (Ad-MSCs) and Ad-MSC sheets. Composite PCL/β-TCP scaffolds seeded with Ad-MSCs or wrapped with osteogenic Ad-MSC sheets (OCS) were also fabricated and their osteogenic potential was assessed following transplantation into critical-sized bone defects in dogs. The alkaline phosphatase (ALP) activity of osteogenic Ad-MSCs (O-MSCs) and OCS was significantly higher than that of undifferentiated Ad-MSCs (U-MSCs). The ALP, runt-related transcription factor 2, osteopontin, and bone morphogenetic protein 7 mRNA levels were upregulated in O-MSCs and OCS as compared to U-MSCs. In a segmental bone defect, the amount of newly formed bone was greater in PCL/β-TCP/OCS and PCL/β-TCP/O-MSCs/OCS than in the other groups. The OCS exhibit strong osteogenic capacity, and OCS combined with a PCL/β-TCP composite scaffold stimulated new bone formation in a critical-sized bone defect. These results suggest that the PCL/β-TCP/OCS composite has potential clinical applications in bone regeneration and can be used as an alternative treatment modality in bone tissue engineering.

Proliferation and osteogenic differentiation of mesenchymal stromal cells in a novel porous hydroxyapatite scaffold

AIM

To compare the effect of bovine bone derived porous hydroxyapatite (BDHA) scaffold on proliferation and osteogenic differentiation of human bone marrow-derived mesenchymal stromal cells (hMSCs) compared with commercial hydroxyapatite (CHA) scaffold.

MATERIALS AND METHODS

The porosity and pore size were analyzed using micro-CT. The biocompatibility was demonstrated by alamar blue assay, and cell attachment through SEM and Hoechst staining. The osteogenic differentiation was demonstrated using biochemical assay and osteogenic gene expression.

RESULTS

BDHA and CHA scaffolds showed porosity of 76.6 ± 0.6 and 64.3 ± 0.3% and pore size diameter of 0.04-0.25 and 0.1-2.6 mm, respectively. hMSCs proliferation, ALP activity, osteocalcin secretion and osteogenic gene expression are comparable in both the scaffolds.

CONCLUSION

These results demonstrated that BDHA is biocompatible, supports cell adhesion and promotes proliferation and osteogenic differentiation.

A Comparative Evaluation of the Mechanical Properties of Two Calcium Phosphate/Collagen Composite Materials and Their Osteogenic Effects on Adipose-Derived Stem Cells

Adipose-derived stem cells (ADSCs) are ideal seed cells for use in bone tissue engineering and they have many advantages over other stem cells. In this study, two kinds of calcium phosphate/collagen composite scaffolds were prepared and their effects on the proliferation and osteogenic differentiation of ADSCs were investigated. The hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) composite scaffolds (HTPSs), which have an additional β-tricalcium phosphate, resulted in better proliferation of ADSCs and showed osteogenesis-promoting effects. Therefore, such composite scaffolds, in combination with ADSCs or on their own, would be promising for use in bone regeneration and potential clinical therapy for bone defects.

Mineral particles modulate osteo-chondrogenic differentiation of embryonic stem cell aggregates

Pluripotent stem cell aggregates offer an attractive approach to emulate embryonic morphogenesis and skeletal development. Calcium phosphate (CaP) based biomaterials have been shown to promote bone healing due to their osteoconductive and potential osteoinductive properties. In this study, we hypothesized that incorporation of CaP-coated hydroxyapatite mineral particles (MPs) within murine embryonic stem cell (ESC) aggregates could promote osteo-chondrogenic differentiation. Our results demonstrated that MP alone dose-dependently promoted the gene expression of chondrogenic and early osteogenic markers. In combination with soluble osteoinductive cues, MPs enhanced the hypertrophic and osteogenic phenotype, and mineralization of ESC aggregates. Additionally, MPs dose-dependently reduced ESC pluripotency and thereby decreased the size of teratomas derived from MP-incorporated ESC aggregates in vivo. Our data suggested a novel yet simple means of using mineral particles to control stem cell fate and create an osteochondral niche for skeletal tissue engineering applications.

STATEMENT OF SIGNIFICANCE

Directing stem cell differentiation and morphogenesis via biomaterials represents a novel strategy to promote cell fates and tissue formation. Our study demonstrates the ability of calcium phosphate-based mineral particles to promote osteochondrogenic differentiation of embryonic stem cell aggregates as well as modulate teratoma formation in vivo. This hybrid biomaterial-ESC aggregate approach serves as an enabling platform to evaluate the ability of biomaterials to regulate stem cell fate and regenerate functional skeletal tissues for clinical applications.

Advanced Properties of Urine Derived Stem Cells Compared to Adipose Tissue Derived Stem Cells in Terms of Cell Proliferation, Immune Modulation and Multi Differentiation

Adipose tissue stem cells (ADSCs) would be an attractive autologous cell source. However, ADSCs require invasive procedures, and has potential complications. Recently, urine stem cells (USCs) have been proposed as an alternative stem cell source. In this study, we compared USCs and ADSCs collected from the same patients on stem cell characteristics and capacity to differentiate into various cell lineages to provide a useful guideline for selecting the appropriate type of cell source for use in clinical application. The urine samples were collected via urethral catheterization, and adipose tissue was obtained from subcutaneous fat tissue during elective laparoscopic kidney surgery from the same patient (n = 10). Both cells were plated for primary culture. Cell proliferation, colony formation, cell surface markers, immune modulation, chromosome stability and multi-lineage differentiation were analyzed for each USCs and ADSCs at cell passage 3, 5, and 7. USCs showed high cell proliferation rate, enhanced colony forming ability, strong positive for stem cell markers expression, high efficiency for inhibition of immune cell activation compared to ADSCs at cell passage 3, 5, and 7. In chromosome stability analysis, both cells showed normal karyotype through all passages. In analysis of multi-lineage capability, USCs showed higher myogenic, neurogenic, and endogenic differentiation rate, and lower osteogenic, adipogenic, and chondrogenic differentiation rate compared to ADSCs. Therefore, we expect that USC can be an alternative autologous stem cell source for muscle, neuron and endothelial tissue reconstruction instead of ADSCs.

Histochemical examination of adipose derived stem cells combined with β-TCP for bone defects restoration under systemic administration of 1α,25(OH)2D3

The purpose of this study was to evaluate the effects of osteogenic differentiated adipose-derived stem cell (ADSC) loaded beta-tricalcium phosphate (β-TCP) in the restoration of bone defects under intraperitoneal administration of 1α,25-dihydroxyvitamin D3(1α,25(OH)2D3). ADSCs were isolated from the fat tissue of 8 week old Wister rats and co-cultured with β-TCP for 21 days under osteogenic induction. Then the ADSC-β-TCP complexes were implanted into bone defects in the femora of rats. 1α,25(OH)2D3 (VD) or normal saline (NS) was administrated intraperitoneally every other day after the surgery. Femora were harvested at day 7, day 14 and day 28 post-surgery. There were 4 groups for all specimens: β-TCP-NS group; β-TCP-ADSC-NS group; β-TCP-VD group and β-TCP-ADSC-VD group. Alkaline phosphatase (ALP) was up-regulated obviously in ADSC groups compared with non-ADSC groups at day 7, day 14 and day 28, although high expression of runt-related transcription factor 2 (RUNX2) was only seen at day 7. Furthermore, the number of TRAP-positive osteoclasts and the expression of cathepsin K (CK) were significantly decreased in VD groups compared with non-VD groups at day 7 and day 14. As a most significant finding, the β-TCP-ADSC-VD group showed the highest BV/TV ratio compared with the other three groups at day 28. Taken together, ADSC-loaded β-TCP under the administration of 1α,25(OH)2D3 made a promising therapy for bone defects restoration.

Evaluation of implant-materials as cell carriers for dental stem cells under in vitro conditions

BACKGROUND

Dental stem cells in combination with implant materials may become an alternative to autologous bone transplants. For tissue engineering different types of soft and rigid implant materials are available, but little is known about the viability and the osteogenic differentiation of dental stem cells on these different types of materials. According to previous studies we proposed that rigid bone substitute materials are superior to soft materials for dental tissue engineering.

METHODS

We evaluated the proliferation, the induction of apoptosis and the osteogenic differentiation of dental stem/progenitor cells on a synthetic bone-like material and on an allograft product. The soft materials silicone and polyacrylamide (PA) were used for comparison. Precursor cells from the dental follicle (DFCs) and progenitor cells from the dental apical papilla of retained third molar tooth (dNC-PCs) were applied as dental stem cells in our study.

RESULTS

Both dental cell types attached and grew on rigid bone substitute materials, but they did not grow on soft materials. Moreover, rigid bone substitute materials only sustained the osteogenic differentiation of dental stem cells, although the allograft product induced apoptosis in both dental cell types. Remarkably, PA, silicone and the synthetic bone substitute material did not induce the apoptosis in dental cells.

CONCLUSIONS

Our work supports the hypothesis that bone substitute materials are suitable for dental stem cell tissue engineering. Furthermore, we also suggest that the induction of apoptosis by bone substitute materials may not impair the proliferation and the differentiation of dental stem cells.

Synergetic effects of hBMSCs and hPCs in osteogenic differentiation and their capacity in the repair of critical-sized femoral condyle defects

Tissue-engineered bone grafts require an osteoblastic cellular source to be utilized in bone transplantation therapy. Human bone marrow stem cells (hBMSCs) and periosteal-derived stem cells (hPCs) are the commonly used cellular sources for bone tissue engineering and are essential in fracture healing. In the present study, hBMSCs and hPCs were co-cultured from the same donors, as the cellular source. In monolayer cultivation, co-culturing hBMSCs and hPCs demonstrated more robust mineralized nodule formation and stronger alkaline phosphatase (ALP) positive staining than hBMSCs or hPCs. Three-dimensional (3-D) culturing on porous β-tricalcium phosphate (TCP) scaffolds and co-culturing of hBMSCs and hPCs significantly promoted the osteogenic specific mRNA expression of COL1α1, BMP-2, osteopontin (OPN) and osteocalcin (OC). For in vivo bone formation and neovascularization assessment, the cellular-β-TCP scaffolds were transplanted into critical-sized femoral condyle defects in rabbits. The results confirmed that co-culturing hBMSCs and hPCs accelerated bone regeneration and enhanced mature bone formation, but also facilitated central vascularization in scaffold pores. Based on these data, we recommend co-culturing hBMSCs and hPCs as a promising cellular source for bone tissue engineering applications.

Bone marrow stromal cells on a three-dimensional bioactive fiber mesh undergo osteogenic differentiation in the absence of osteogenic media supplements: the effect of silanol groups

Osteogenic differentiation is a tightly regulated process dependent on the stimuli provided by the micro-environment. Silicon-substituted materials are known to have an influence on the osteogenic phenotype of undifferentiated and bone-derived cells. This study aims to investigate the bioactivity profile as well as the mechanical properties of a blend of starch and poly-caprolactone (SPCL) polymeric fiber mesh scaffolds functionalized with silanol (Si-OH) groups as key features for bone tissue engineering strategies. The scaffolds were made from SPCL by a wet spinning technique. A calcium silicate solution was used as a non-solvent to develop an in situ functionalization with Si-OH groups in a single-step approach. We also explored the relevance of silicon incorporated in SPCL-Si scaffolds to the in vitro osteogenic process of goat bone marrow stromal cells (gBMSCs) with and without osteogenic supplements in the culture medium. We hypothesized that SPCL-Si scaffolds could act as physical and chemical millieus to induce per se the osteogenic differentiation of gBMSCs. Results show that osteogenic differentiation of gBMSCs and the production of a mineralized extracellular matrix on bioactive SPCL-Si scaffolds occur for up to 2weeks, even in the absence of osteogenic supplements in the culture medium. The omission of media supplements to induce osteogenic differentiation is a promising feature towards simplified and cost-effective cell culturing procedures of a potential bioengineered product, and concomitant translation into the clinical field. Thus, the present work demonstrates that SPCL-Si scaffolds and their intrinsic properties sustain gBMSC osteogenic features in vitro, even in the absence of osteogenic supplements to the culture medium, and show great potential for bone regeneration strategies.

Increased survival of human free fat grafts with varying densities of human adipose-derived stem cells and platelet-rich plasma

The high absorption rate of transplanted fat has limited the application of autogenous fat grafts in the clinical setting. Therefore, this study aimed to evaluate the effects of platelet-rich plasma (PRP) and adipose-derived stem cells (ASCs) on fat regeneration by investigating the impact of PRP and conditioned medium on the biological characteristics of ASCs. Fat grafts were prepared with ASCs at densities of 10⁷ /ml, 10⁶ /ml, 10⁵ /ml, 10⁴ /ml and 0/ml with and without PRP and injected subcutaneously into nude mice. Liquid overflow method, haematoxylin and eosin staining, and immunohistochemical analyses were used to examine the fat grafts. The residual fat volume of the 10⁵ /ml ASC + PRP group was significantly higher than that of other treatment conditions after 90 days. Furthermore, histological examination revealed that in 10⁵ /ml ASCs-treated grafts normal adipocyte area and capillary formation were increased dramatically compared with other treatment conditions. It is concluded that fat grafts consisting of PRP and 10⁵ /ml ASCs constitute an ideal transplant strategy, which may result in decreased absorption and accelerated fat regeneration. This simple and reliable method could provide a valuable and needed tool in plastic and reconstructive surgery. Copyright © 2014 John Wiley & Sons, Ltd.

Isolation, characterization, differentiation, and application of adipose-derived stem cells

While bone marrow-derived mesenchymal stem cells are known and have been investigated for a long time, mesenchymal stem cells derived from the adipose tissue were identified as such by Zuk et al. in 2001. However, as subcutaneous fat tissue is a rich source which is much more easily accessible than bone marrow and thus can be reached by less invasive procedures, adipose-derived stem cells have moved into the research spotlight over the last 8 years.Isolation of stromal cell fractions involves centrifugation, digestion, and filtration, resulting in an adherent cell population containing mesenchymal stem cells; these can be subdivided by cell sorting and cultured under common conditions.They seem to have comparable properties to bone marrow-derived mesenchymal stem cells in their differentiation abilities as well as a favorable angiogenic and anti-inflammatory cytokine secretion profile and therefore have become widely used in tissue engineering and clinical regenerative medicine.

Effects of novel hydroxyapatite-based 3D biomaterials on proliferation and osteoblastic differentiation of mesenchymal stem cells

The aim of this study was to examine the differential capacity of isolated dental pulp stem cells (SHED) cultured onto four different scaffold materials. The differential potential of isolated SHED was examined on the following scaffolds: porous hydroxyapatite (pHAP) alone or combined with three polymers [polylactic-co-glycolic acid (PLGA), alginate, and ethylene vinylacetate / ethylene vinylversatate (EVA/EVV)]. SHED were isolated by "outgrowth" method and characterized by the flow cytometry. Viability of cells grown with scaffolds was assessed by MTT and LDH assays. No significant cytotoxic effect of any of the tested materials was shown. Staining with alizarin red and estimated alkaline phosphatase activity to identify differentiation, demonstrated osteoblastic phenotype of SHED and newly deposited and mineralized extra cellular matrix (ECM) in presence of all tested scaffolds. The developed ECM seen at scanning electronic micrographs additionally confirmed the osteogenic differentiation and biocompatibility between cells and materials. In summary, all studied biomaterials are suitable carriers for proliferation and osteoblastic differentiation of dental pulp mesenchymal stem cells in vitro.

A novel method to apply osteogenic potential of adipose derived stem cells in orthopaedic surgery

Background

A number of publications have reported that adipose derived stem cells (ADSCs) have the capacity to be induced to differentiate into osteoblasts both in vitro and in vivo. However, it has been difficult to use separate ADSCs for cortical bone regeneration and bone reconstruction so far. Inspired by the research around stromal stem cells and cell sheets, we developed a new method to fabricate ADSCs sheets to accelerate and enhance the bone regeneration and bone reconstruction.

Purpose

To fabricate ADSCs sheets and evaluate their capacity to be induced to differentiate to osteoblasts in vitro.

Methods

Human adipose derived stem cells (hADSCs) were employed in this research. The fabricating medium containing 50 µM ascorbate-2-phosphate was used to enhance the secretion of collagen protein by the ADSCs and thus to make the cell sheets of ADSCs. As the separate ADSCs were divided into osteo-induction group and control group, the ADSCs sheets were also divided into two groups depending on induction by osteogenesis medium or no induction. The osteogenic capacity of each group was evaluated by ALP staining, Alizarin Red staining and ALP activity.

Results

The ADSCs sheets were fabricated after one-week culture in the fabricating medium. The ALP staining of ADSCs sheets showed positive results after 5 days osteo-induction and the Alizarin Red staining of ADSCs sheets showed positive results after 1 week osteo-induction. The ALP activity showed significant differences between these four groups. The ALP activity of ADSCs sheets groups showed higher value than that of separate ADSCs.

Conclusion

The experiments demonstrated that ADSCs sheets have better capacity than separate ADSCs to be induced to differentiate into osteoblasts. This indicates that it is possible to use the ADSCs sheets as a source of mesenchymal stem cells for bone regeneration and bone reconstruction.

In situ precipitation of amorphous and crystalline calcium sulphates in cellulose thin films

Cellulose films regenerated with calcium sulphate are fabricated using N-methylmorpholine N-oxide as a solvent and capping agent for polysaccharide dissolution and nanoparticle stabilization, respectively.

Adipose-derived mesenchymal cells for bone regereneration: state of the art

Adipose tissue represents a hot topic in regenerative medicine because of the tissue source abundance, the relatively easy retrieval, and the inherent biological properties of mesenchymal stem cells residing in its stroma. Adipose-derived mesenchymal stem cells (ASCs) are indeed multipotent somatic stem cells exhibiting growth kinetics and plasticity, proved to induce efficient tissue regeneration in several biomedical applications. A defined consensus for their isolation, classification, and characterization has been very recently achieved. In particular, bone tissue reconstruction and regeneration based on ASCs has emerged as a promising approach to restore structure and function of bone compromised by injury or disease. ASCs have been used in combination with osteoinductive biomaterial and/or osteogenic molecules, in either static or dynamic culture systems, to improve bone regeneration in several animal models. To date, few clinical trials on ASC-based bone reconstruction have been concluded and proved effective. The aim of this review is to dissect the state of the art on ASC use in bone regenerative applications in the attempt to provide a comprehensive coverage of the topics, from the basic laboratory to recent clinical applications.

Exogenously added BMP-6, BMP-7 and VEGF may not enhance the osteogenic differentiation of human adipose stem cells

In the present study bone morphogenetic protein (BMP)-6 alone or in synergy with BMP-7 and vascular endothelial growth factor (VEGF) were tested with human adipose stem cells (hASCs) seeded on cell culture plastic or 3D bioactive glass. Osteogenic medium (OM) was used as a positive control for osteogenic differentiation. The same growth factor groups were also tested combined with OM. None of the growth factor treatments could enhance the osteogenic differentiation of hASCs in 3D- or 2D-culture compared to control or OM. In 3D-culture OM promoted significantly total collagen production, whereas in 2D-culture OM induced high total ALP activity and mineralization compared to control and growth factors groups, but also high cell proliferation. In this study, hASCs did not respond to exogenously added growth although various parameters of the study set-up may have affected these findings contradictory to the previous literature.

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.

In vitro human adipose-derived stromal/stem cells osteogenesis in akermanite:poly-ε-caprolactone scaffolds

This study compared the metabolic activity, cell proliferation and osteogenic differentiation of human adipose-derived stromal/stem cells cultured on four different scaffolds (poly-ε-caprolactone, akermanite:poly-ε-caprolactone composites, akermanite and β-tricalcium phosophate) with or without osteogenic media supplementation for up to 21 days. The hypothesis was that human adipose-derived stromal/stem cells osteogenesis in akermanite-containing scaffolds would be greater than the other scaffold types independent of the media supplementation. According to the results, human adipose-derived stromal/stem cells loaded on different scaffolds and cultured in both media conditions displayed significant changes in the metabolic activity and cell proliferation. After 21 days of culture in osteogenic medium, the human adipose-derived stromal/stem cells loaded onto akermanite-based scaffolds had greater calcium deposition and osteocalcin expression relative to human adipose-derived stromal/stem cells loaded onto β-tricalcium phosophate and poly-ε-caprolactone. In vivo investigations are needed to further assess the bone tissue engineering potential of human adipose-derived stromal/stem cells loaded to akermanite:poly-ε-caprolactone composites.

Development of fully defined xeno-free culture system for the preparation and propagation of cell therapy-compliant human adipose stem cells

Introduction

Adipose tissue is an attractive and abundant source of multipotent stem cells. Human adipose stem cells (ASCs) have shown to have therapeutic relevancy in diverse clinical applications. Nevertheless, expansion of ASCs is often necessary before performing clinical studies. Standard in vitro cell-culture techniques use animal-derived reagents that should be avoided in clinical use because of safety issues. Therefore, xeno- and serum-free (XF/SF) reagents are highly desirable for enhancing the safety and quality of the transplanted ASCs.

Methods

In the current study, animal component-free isolation and cell-expansion protocols were developed for ASCs. StemPro MSC SFM XF medium with either CELLstart™ CTS™ coating or Coating Matrix Kit were tested for their ability to support XF/SF growth. Basic stem-cell characteristics such as immunophenotype (CD3, CD11a, CD14, CD19, CD34, CD45RO, CD54, CD73, CD80, CD86, CD90, CD105, HLA-DR), proliferation, and differentiation potential were assessed in XF/SF conditions and compared with human serum (HS) or traditionally used fetal bovine serum (FBS) cultures.

Results

ASCs cultured in XF/SF conditions had significantly higher proliferation rates compared with HS/FBS cultures. Characteristic immunophenotypes of ASCs were maintained in every condition; however, cells expanded in XF/SF conditions showed significantly lower expression of CD54 (intercellular adhesion molecule 1, ICAM-1) at low passage number. Further, multilineage differentiation potential of ASCs was maintained in every culture condition.

Conclusions

Our findings demonstrated that the novel XF/SF conditions maintained the basic stem cell features of ASCs and the animal-free workflow followed in this study has great potential in clinical cell therapies.

Adipose-Derived Stem Cells in Tissue Regeneration: A Review

In 2001, researchers at the University of California, Los Angeles, described the isolation of a new population of adult stem cells from liposuctioned adipose tissue. These stem cells, now known as adipose-derived stem cells or ADSCs, have gone on to become one of the most popular adult stem cells populations in the fields of stem cell research and regenerative medicine. As of today, thousands of research and clinical articles have been published using ASCs, describing their possible pluripotency in vitro, their uses in regenerative animal models, and their application to the clinic. This paper outlines the progress made in the ASC field since their initial description in 2001, describing their mesodermal, ectodermal, and endodermal potentials both in vitro and in vivo, their use in mediating inflammation and vascularization during tissue regeneration, and their potential for reprogramming into induced pluripotent cells.

A novel cyclic RGD-containing peptide polymer improves serum-free adhesion of adipose tissue-derived mesenchymal stem cells to bone implant surfaces

Seeding of bone implants with mesenchymal stem cells (MSCs) may promote osseointegration and bone regeneration. However, implant material surfaces, such as titanium or bovine bone mineral, fail to support rapid and efficient attachment of MSCs, especially under serum-free conditions that may be desirable when human applications or tightly controlled experiments are envisioned. Here we demonstrate that a branched poly[Lys(Ser(i)-DL-Ala(m))] polymer functionalized with cyclic arginyl-glycyl-aspartate, when immobilized by simple adsorption to tissue culture plastic, surgical titanium alloy (Ti6Al4V), or Bio-Oss(®) bovine bone substitute, significantly accelerates serum-free adhesion and enhances seeding efficiency of human adipose tissue-derived MSCs. Moreover, when exposed to serum-containing osteogenic medium, MSCs survived and differentiated on the peptide-coated scaffolds. In summary, the presented novel polypeptide conjugate can be conveniently used for coating various surfaces, and may find applications whenever quick and efficient seeding of MSCs is required to various scaffolds in the absence of serum.

Novel polypyrrole-coated polylactide scaffolds enhance adipose stem cell proliferation and early osteogenic differentiation

An electrically conductive polypyrrole (PPy) doped with a bioactive agent is an emerging functional biomaterial for tissue engineering. We therefore used chondroitin sulfate (CS)-doped PPy coating to modify initially electrically insulating polylactide resulting in novel osteogenic scaffolds. In situ chemical oxidative polymerization was used to obtain electrically conductive PPy coating on poly-96L/4D-lactide (PLA) nonwoven scaffolds. The coated scaffolds were characterized and their electrical conductivity was evaluated in hydrolysis. The ability of the coated and conductive scaffolds to enhance proliferation and osteogenic differentiation of human adipose stem cells (hASCs) under electrical stimulation (ES) in three-dimensional (3D) geometry was compared to the noncoated PLA scaffolds. Electrical conductivity of PPy-coated PLA scaffolds (PLA-PPy) was evident at the beginning of hydrolysis, but decreased during the first week of incubation due to de-doping. PLA-PPy scaffolds enhanced hASC proliferation significantly compared to the plain PLA scaffolds at 7 and 14 days. Furthermore, the alkaline phosphatase (ALP) activity of the hASCs was generally higher in PLA-PPy seeded scaffolds, but due to patient variation, no statistical significance could be determined. ES did not have a significant effect on hASCs. This study highlights the potential of novel PPy-coated PLA scaffolds in bone tissue engineering.

Characterization of novel akermanite:poly-ϵ-caprolactone scaffolds for human adipose-derived stem cells bone tissue engineering

In this study, three different akermanite:poly-ϵ-caprolactone (PCL) composite scaffolds (wt%: 75:25, 50:50, 25:75) were characterized in terms of structure, compression strength, degradation rate and in vitro biocompatibility to human adipose-derived stem cells (hASC). Pure ceramic scaffolds [CellCeram™, custom-made, 40:60 wt%; β-tricalcium phosphate (β-TCP):hydroxyapatite (HA); and akermanite] and PCL scaffolds served as experimental controls. Compared to ceramic scaffolds, the authors hypothesized that optimal akermanite:PCL composites would have improved compression strength and comparable biocompatibility to hASC. Electron microscopy analysis revealed that PCL-containing scaffolds had the highest porosity but CellCeram™ had the greatest pore size. In general, compression strength in PCL-containing scaffolds was greater than in ceramic scaffolds. PCL-containing scaffolds were also more stable in culture than ceramic scaffolds. Nonetheless, mass losses after 21 days were observed in all scaffold types. Reduced hASC metabolic activity and increased cell detachment were observed after acute exposure to akermanite:PCL extracts (wt%: 75:25, 50:50). Among the PCL-containing scaffolds, hASC cultured for 21 days on akermanite:PCL (wt%: 75:25) discs displayed the highest viability, increased expression of osteogenic markers (alkaline phosphatase and osteocalcin) and lowest IL-6 expression. Together, the results indicate that akermanite:PCL composites may have appropriate mechanical and biocompatibility properties for use as bone tissue scaffolds.

Tissue engineered bone grafts based on biomimetic nanocomposite PLGA/amorphous calcium phosphate scaffold and human adipose-derived stem cells

For tissue engineering of critical size bone grafts, nanocomposites are getting more and more attractive due to their controllable physical and biological properties. We report in vitro and in vivo behaviour of an electrospun nanocomposite based on poly-lactic-co-glycolic acid and amorphous calcium phosphate nanoparticles (PLGA/a-CaP) seeded with human adipose-derived stem cells (ASC) compared to PLGA. Major findings were that cell attachment, three-dimensional ingrowth and proliferation were very good on both materials. Cell morphology changed from a spindle-shaped fibroblast-like form to a more roundish type when ASC were seeded on PLGA, while they retained their morphology on PLGA/a-CaP. Moreover, we found ASC differentiation to a phenotype committed towards osteogenesis when a-CaP nanoparticles were suspended in normal culture medium without any osteogenic supplements, which renders a-CaP nanoparticles an interesting osteoinductive component for the synthesis of other nanocomposites than PLGA/a-CaP. Finally, electrospun PLGA/a-CaP scaffold architecture is suitable for a rapid and homogenous vascularisation confirmed by a complete penetration by avian vessels from the chick chorioallantoic membrane (CAM) within one week.

Human adipose-derived stem cells and three-dimensional scaffold constructs: a review of the biomaterials and models currently used for bone regeneration

In the past decade, substantial strides have been taken toward the use of human adipose-derived stromal/stem cells (hASC) in the regeneration of bone. Since the discovery of the hASC osteogenic potential, many models have combined hASC with biodegradable scaffold materials. In general, rats and immunodeficient (nude) mice models for nonweight bearing bone formation have led the way to assess hASC osteogenic potential in vivo. The goal of this review is to present an overview of the recent literature describing hASC osteogenesis in conjunction with three-dimensional scaffolds for bone regeneration.

Review of biophysical factors affecting osteogenic differentiation of human adult adipose-derived stem cells

Developing bone is subject to the control of a broad variety of influences in vivo. For bone repair applications, in vitro osteogenic assays are routinely used to test the responses of bone-forming cells to drugs, hormones, and biomaterials. Results of these assays are used to predict the behavior of bone-forming cells in vivo. Stem cell research has shown promise for enhancing bone repair. In vitro osteogenic assays to test the bone-forming response of stem cells typically use chemical solutions. Stem cell in vitro osteogenic assays often neglect important biophysical cues, such as the forces associated with regular weight-bearing exercise, which promote bone formation. Incorporating more biophysical cues that promote bone formation would improve in vitro osteogenic assays for stem cells. Improved in vitro osteogenic stimulation opens opportunities for "pre-conditioning" cells to differentiate towards the desired lineage. In this review, we explore the role of select biophysical factors-growth surfaces, tensile strain, fluid flow and electromagnetic stimulation-in promoting osteogenic differentiation of stem cells from human adipose. Emphasis is placed on the potential for physical microenvironment manipulation to translate tissue engineering and stem cell research into widespread clinical usage.

Stem cell-based therapies for bone repair

This article provides an overview of the cellular and molecular events involved in bone repair and the current approaches to using stem cells as an adjunct to this process. The article emphasizes the key role of osteoprogenitor cells in the formation of bone and where the clinical applications of current research may lend themselves to large animal orthopaedics. The processes involved in osteogenic differentiation are presented and strategies for bone formation, including induction by osteogenic factors, bioscaffolds, and gene therapy, are reviewed.

Tissue-engineering strategies for the tendon/ligament-to-bone insertion

Injuries to connective tissues are painful and disabling and result in costly medical expenses. These injuries often require reattachment of an unmineralized connective tissue to bone. The uninjured tendon/ligament-to-bone insertion (enthesis) is a functionally graded material that exhibits a gradual transition from soft tissue (i.e., tendon or ligament) to hard tissue (i.e., mineralized bone) through a fibrocartilaginous transition region. This transition is believed to facilitate force transmission between the two dissimilar tissues by ameliorating potentially damaging interfacial stress concentrations. The transition region is impaired or lost upon tendon/ligament injury and is not regenerated following surgical repair or natural healing, exposing the tissue to risk of reinjury. The need to regenerate a robust tendon-to-bone insertion has led a number of tissue engineering repair strategies. This review treats the tendon-to-bone insertion site as a tissue structure whose primary role is mechanical and discusses current and emerging strategies for engineering the tendon/ligament-to-bone insertion in this context. The focus lies on strategies for producing mechanical structures that can guide and subsequently sustain a graded tissue structure and the associated cell populations.