Human adipose-derived adult stem cells produce osteoid in vivo

Adult Stem Cells Freezing Processes and Cryopreservation Protocols

The development of simple but effective storage protocols for adult stem cells will greatly enhance their use and utility in tissue-engineering applications. Cryopreservation has shown the most promise but is a fairly complex process, necessitating the use of chemicals called cryoprotective agents (CPAs), freezing equipment, and obviously, storage in liquid nitrogen. The purpose of this chapter is to present a general overview of cryopreservation storage techniques and the optimal protocols/results obtained in our laboratory for long-term storage of adult stem cells using freezing storage.

Biocompatibility and interaction of porous alumina-zirconia scaffolds with adipose-derived mesenchymal stem cells for bone tissue regeneration

Replacement of bone defects with bone graft or implant is an important therapeutic strategy that has been used in routine practice. However, the identification of biomaterials that can mimic natural bone properties and serve as bone substitutes remains a major challenge. In this context, alumina-zirconia (Al2O3/ZrO2) nanocomposites emerge as potential alternatives for biomedical applications, owing to their high mechanical strength, wear resistance, and biocompatibility. In this sense, in this study, we prepared porous Al2O3/ZrO2 nanocomposites (scaffolds) using the gelcasting method and biomimetically coated them with calcium phosphate (CaP). We evaluated the biocompatibility of the scaffolds using the quantitative MTT cytotoxicity test in L929 cells. Moreover, rabbit adipose-derived mesenchymal stem cells (rADMSCs) were seeded with CaP-containing and CaP-free porous samples to evaluate cell proliferation and cell-scaffold interaction in vitro. Our results showed that the Al2O3/ZrO2 scaffolds were non-cytotoxic, and there were no significant differences between CaP-containing and CaP-free scaffolds in terms of cell growth and adhesion. In contrast, when co-cultured with rADMSCs, the scaffolds enhanced cell proliferation and cell adhesion. The rADMSCs adhered and migrated through the pores of the scaffold and anchored to different poles with differentiated elongated structures. These results suggest osteogenic differentiation of rADMSCs in response to mechanical loading of Al2O3/ZrO2 scaffolds. Therefore, we conclude that Al2O3/ZrO2 scaffolds have demonstrated significant implications in bone tissue engineering and are valuable biomaterials for bone replacement.

Alveolar Ridge Augmentation with a Novel Combination of 3D-Printed Scaffolds and Adipose-Derived Mesenchymal Stem Cells-A Pilot Study in Pigs

Alveolar ridge augmentation is an important dental procedure to increase the volume of bone tissue in the alveolar ridge before the installation of a dental implant. To meet the high demand for bone grafts for alveolar ridge augmentation and to overcome the limitations of autogenous bone, allografts, and xenografts, researchers are developing bone grafts from synthetic materials using novel fabrication techniques such as 3D printing. To improve the clinical performance of synthetic bone grafts, stem cells with osteogenic differentiation capability can be loaded into the grafts. In this pilot study, we propose a novel bone graft which combines a 3D-printed polycaprolactone-tricalcium phosphate (PCL-TCP) scaffold with adipose-derived mesenchymal stem cells (AD-MSCs) that can be harvested, processed and implanted within the alveolar ridge augmentation surgery. We evaluated the novel bone graft in a porcine lateral alveolar defect model. Radiographic analysis revealed that the addition of AD-MSCs to the PCL-TCP scaffold improved the bone volume in the defect from 18.6% to 28.7% after 3 months of healing. Histological analysis showed the presence of AD-MSCs in the PCL-TCP scaffold led to better formation of new bone and less likelihood of fibrous encapsulation of the scaffold. Our pilot study demonstrated that the loading of AD-MSCs improved the bone regeneration capability of PCL-TCP scaffolds, and our novel bone graft is suitable for alveolar ridge augmentation.

Frontiers of Hydroxyapatite Composites in Bionic Bone Tissue Engineering

Bone defects caused by various factors may cause morphological and functional disorders that can seriously affect patient's quality of life. Autologous bone grafting is morbid, involves numerous complications, and provides limited volume at donor site. Hence, tissue-engineered bone is a better alternative for repair of bone defects and for promoting a patient's functional recovery. Besides good biocompatibility, scaffolding materials represented by hydroxyapatite (HA) composites in tissue-engineered bone also have strong ability to guide bone regeneration. The development of manufacturing technology and advances in material science have made HA composite scaffolding more closely related to the composition and mechanical properties of natural bone. The surface morphology and pore diameter of the scaffold material are more important for cell proliferation, differentiation, and nutrient exchange. The degradation rate of the composite scaffold should match the rate of osteogenesis, and the loading of cells/cytokine is beneficial to promote the formation of new bone. In conclusion, there is no doubt that a breakthrough has been made in composition, mechanical properties, and degradation of HA composites. Biomimetic tissue-engineered bone based on vascularization and innervation show a promising future.

Assessing the Efficacy of Whole-Body Titanium Dental Implant Surface Modifications in Inducing Adhesion, Proliferation, and Osteogenesis in Human Adipose Tissue Stem Cells

BACKGROUND

Although the influence of titanium implants' micro-surface properties on titanium discs has been extensively investigated, the research has not taken into consideration their whole-body effect, which may be considered possible using a combinatorial approach.

METHODS

Five titanium dental implants with a similar moderate roughness and different surface textures were thoroughly characterized. The cell adhesion and proliferation were assessed after adipose-tissue-derived stem cells (ADSCs) were seeded on whole-body implants. The implants' inductive properties were assessed by evaluating the osteoblastic gene expression.

RESULTS

The surface micro-topography was analyzed, showing that hydroxyapatite (HA)-blasted and bland acid etching implants had the highest roughness and a lower number of surface particles. Cell adhesion was observed after 24 h on all the implants, with the highest score registered for the HA-blasted and bland acid etching implants. Cell proliferation was observed only on the laser-treated and double-acid-etched surfaces. The ADSCs expressed collagen type I, osteonectin, and alkaline phosphatase on all the implant surfaces, with high levels on the HA-treated surfaces, which also triggered osteocalcin expression on day seven.

CONCLUSIONS

The findings of this study show that the morphology and treatment of whole titanium dental implants, primarily HA-treated and bland acid etching implants, impact the adherence and activity of ADSCs in osteogenic differentiation in the absence of specific osteo-inductive signals.

An In Vitro and In Vivo Comparison of Osteogenic Differentiation of Human Mesenchymal Stromal/Stem Cells

The use of stem cells in regenerative medicine, including tissue engineering and transplantation, has generated a great deal of enthusiasm. Mesenchymal stromal/stem cells (MSCs) can be isolated from various tissues, most commonly, bone marrow but more recently adipose tissue, dental pulp, and Wharton's jelly, to name a few. MSCs display varying phenotypic profiles and osteogenic differentiating capacity depending and their site of origin. MSCs have been successfully differentiated into osteoblasts both in vitro an in vivo but discrepancies exist when the two are compared: what happens in vitro does not necessarily happen in vivo, and it is therefore important to understand why these differences occur. The osteogenic process is a complex network of transcription factors, stimulators, inhibitors, proteins, etc., and in vivo experiments are helpful in evaluating the various aspects of this osteogenic process without distractions and confounding variables. With that in mind, the results of in vitro experiments need to be carefully considered and interpreted with caution as they do not perfectly replicate the conditions found within living organisms. This is where in vivo experiments help us better understand interactions that might occur in the osteogenic process that cannot be replicated in vitro. Potentially, these differences could also be exploited to develop an optimal MSC cell therapeutic product that can be used for bone disorders. There are many bone disorders, most of which cause a great deal of discomfort. Clinically acceptable protocols could be developed in which MSCs are used to aid in bone regeneration providing relief for patients with chronic pain. The aim of this review is to examine the differences between studies conducted in vitro and in vivo with regard to the osteogenic process to better define the gaps in current osteogenic research. By better understanding osteogenic differentiation, we can better define treatment strategies for various bone disorders.

Mesenchymal adipose stem cells maintain the capacity for differentiation and survival in culture beyond the long term

Mesenchymal cells (MSCs) are considered to be cellular populations of common embryological origin. For clinical research applications, MSCs are expanded and increased with cells obtained from a primary culture. By extracting cells from tissue and encouraging them to reproduce, the stem cell population ends up dominating the culture due to a high proliferation rate and self-renewal. The first subcultures between the third and sixth are chosen in order to obtain the maximum number of cells with optimal differentiation capacity. However, few studies have reported long-term cultivation of MSCs. The objective of this study was to advance the knowledge on the characteristics of MSCs by assessing their capacity for self-renewal and phenotypic maintenance beyond 50 cell subcultures, which is defined as the normal limit for cellular survival. Rat subcutaneous adipose tissue was the source of mesenchymal adipose stem cells (MASCs) cultured over 175 subcultures. Early 1 to 5 and late 25 to 30 subcultures were used to induce cellular differentiation to become adipogenic, chondrogenic and osteogenic connective tissue cells. MASCs characteristics were studied using flow cytometry, transmission electron microscopy (TEM), and immunohistochemical and reverse transcription polymerase chain reaction (RT-qPCR) assays. The MASCs maintained cell differentiation capacity for more than 30 subcultures but lost potentiality starting at 60 up to 175 subcultures. MASCs showed the embryonic phenotypes OCT3/4 and Nanog indefinitely, and developed compensatory mechanisms, such as autophagy, to achieve cell survival over a long time period. Therefore, long-term subcultures showed that MASCs could maintain their potential for clinical research use.

Advances of adipose-derived mesenchymal stem cells-based biomaterial scaffolds for oral and maxillofacial tissue engineering

The management of oral and maxillofacial tissue defects caused by tumors, trauma, and congenital or acquired deformities has been a major challenge for surgeons over the last few decades. Autologous tissue transplantation, the gold standard of tissue reconstruction, is a valid method for repairing the oral and maxillofacial functions and aesthetics. However, several limitations hinder its clinical applications including complications of donor sites, limited tissue volume, and uncertain long-term outcomes. Adipose-derived mesenchymal stem cells (ADMSCs) widely exist in adipose tissue and can be easily obtained through liposuction. Like the bone marrow-derived mesenchymal stem cells (BMSCs), ADMSCs also have the multi-pluripotent potencies to differentiate into osteoblasts, chondrocytes, neurons, and myocytes. Therefore, the multilineage capacity of ADMSCs makes them valuable for cell-based medical therapies. In recent years, researchers have developed many candidates of ADMSCs-based biomaterial scaffolds to cater for the needs of oral and maxillofacial tissue engineering due to their superior performance. This review presents the advances and applications of ADMSCs-based biomaterial scaffolds, and explores their tissue engineering prospects in oral and maxillofacial reconstructions.

Bone regeneration with autologous adipose-derived mesenchymal stem cells: A reliable experimental model in rats

The adult mesenchymal stem cell (MSC) has been proposed to be the definitive tool in regenerative medicine due to its multi-differentiation potential and expansion capacity ex vivo. The use of MSCs on bone regeneration has been assessed in several studies, obtaining promising results. However, the endless combinations that can be tested and the heterogeneity in the experimental conditions become a drawback when comparing results between authors. Moreover, it is very hard to find autologous studies using adipose-derived MSCs (AD-MSC) in rodents, which is the most used preclinical animal model.

In this article an experimental model for basic bone tissue engineering research is described and justified, on which adult AD-MSCs are safely isolated from the rat dorsal interscapular fat pad, allowing ex vivo expansion and autogenous orthotopic reimplantation in a bilateral mandibular bone defect made in the same animal.

This reliable and reproducible model provides a simple way to perform basic experimentation studies in a small animal model using autologous MSC for bone regeneration or cell therapy techniques prior to improve the research on large animal models.•

Predictable and safe harvest of adipose-derived MSC. No need of animal sacrifice.

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Allows for autologous studies with the most frequently used animal model: the rat. No need of allogeneic or human MSC use and, therefore, immunological concerns are avoided.

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Bilateral mandibular critical size defect to allow direct control/experimental comparison.

Water-transport and intracellular ice formation of human adipose-derived stem cells during freezing

The key to optimizing the cryopreservation strategy of human adipose-derived stem cells (hADSCs) is to identify the biophysical characteristics during freezing. Systematic freezing experiments were conducted under a cryo-microscope system to investigate the cryoinjury mechanism for hADSCs at different cooling rates. By simultaneously fitting morphological change data to the water-transport equation at 5, 10 and 20 °C/min, the plasma membrane hydraulic conductivity, L_pg, and activation energy, E_Lp, were determined. Moreover, the optimal cooling rate was also predicted by using mathematical model methods. Additionally, the surface-catalyzed nucleation (SCN) parameters were calculated by fitting in numerical models, Ω₀^SCN and k₀^SCN were determined at cooling rates of 30, 45 and 60 °C/min. These results may provide potential application value for cryopreservation of hADSCs.

Comparative proteomic analysis of osteogenic differentiated human adipose tissue and bone marrow-derived stromal cells

Mesenchymal stromal cells are promising candidates for regenerative applications upon treatment of bone defects. Bone marrow‐derived stromal cells (BMSCs) are limited by yield and donor morbidity but show superior osteogenic capacity compared to adipose‐derived stromal cells (ASCs), which are highly abundant and easy to harvest. The underlying reasons for this difference on a proteomic level have not been studied yet. Human ASCs and BMSCs were characterized by FACS analysis and tri‐lineage differentiation, followed by an intraindividual comparative proteomic analysis upon osteogenic differentiation. Results of the proteomic analysis were followed by functional pathway analysis. 29 patients were included with a total of 58 specimen analysed. In these, out of 5148 identified proteins 2095 could be quantified in >80% of samples of both cell types, 427 in >80% of ASCs only and 102 in >80% of BMSCs only. 281 proteins were differentially regulated with a fold change of >1.5 of which 204 were higher abundant in BMSCs and 77 in ASCs. Integrin cell surface interactions were the most overrepresented pathway with 5 integrins being among the proteins with highest fold change. Integrin 11a, a known key protein for osteogenesis, could be identified as strongly up‐regulated in BMSC confirmed by Western blotting. The integrin expression profile is one of the key distinctive features of osteogenic differentiated BMSCs and ASCs. Thus, they represent a promising target for modifications of ASCs aiming to improve their osteogenic capacity and approximate them to that of BMSCs.

Cellular Stemness Maintenance of Human Adipose-Derived Stem Cells on ZnO Nanorod Arrays

Ever-growing tissue regeneration and other stem cell therapies cause pressing need for large population of self-renewable stem cells. However, stem cells gradually lose their stemness after long-term in vitro cultivation. In this study, a ZnO nanorod (ZnO NR) array is used to maintain the stemness of human adipose-derived stem cells (hADSCs). The results prove that after culturing hADSCs on ZnO NRs for 3 weeks, the stemness genes and protein expression level are higher than that on culture plates and ZnO film. ZnO NRs can maintain stemness of hADSCs without inhibiting the cell proliferation and oriented differentiation capabilities. KLF4 (Kruppel-like factor 4) is a Zn²⁺ -binding gene that plays a vital role in cell proliferation and differentiation. Sustained Zn²⁺ release and the increased expression of KLF4 can be detected, suggesting that ZnO NRs have efficiently released Zn²⁺ for stemness maintenance. Taken together, the nanotopography of ZnO NRs and the Zn²⁺ release synergistically facilitate stemness maintenance. This study has provided a powerful tool for directing cell fate, maintaining stemness, and realizing the expansion of stem cells in vitro, which will open a new route for the manufacture of large populations of stem cells and fulfilling the growing demand for the cell therapy market.

Mineral deposition and vascular invasion of hydroxyapatite reinforced collagen scaffolds seeded with human adipose-derived stem cells

Background

Collagen-based scaffolds reinforced with hydroxyapatite (HA) are an attractive choice for bone tissue engineering because their composition mimics that of bone. We previously reported the development of compression-molded collagen-HA scaffolds that exhibited high porosity, interconnected pores, and mechanical properties that were well-suited for surgical handling and fixation. The objective of this study was to investigate these novel collagen-HA scaffolds in combination with human adipose-derived stem cells (hASCs) as a template for bone formation in a subcutaneous athymic mouse model.

Methods

Collagen-HA scaffolds and collagen-only scaffolds were fabricated as previously described, and a clinically approved bone void filler was used as a control for the material. Constructs were seeded with hASCs and were pre-treated with either control or osteogenic media. A cell-free group was also included. Scaffolds were implanted subcutaneously in the backs of athymic nude mice for 8 weeks. Mineral deposition was quantified via micro-computed tomography. Histological and immunofluorescence images of the explants were used to analyze their vascular invasion, remodeling and cellularity.

Results

Cell-free collagen-HA scaffolds and those that were pre-seeded with osteogenically differentiated hASCs supported mineral deposition and vascular invasion at comparable rates, while cell-seeded constructs treated with the control medium showed lower mineralization after implantation. HA-reinforcement allowed collagen constructs to maintain their shape, provided improved cell-tissue-scaffold integration, and resulted in a more organized tissue when pre-treated in an osteogenic medium. Scaffold type and pre-treatment also determined osteoclast activity and therefore potential remodeling of the constructs.

Conclusions

The results of this study cumulatively indicate that treatment medium and scaffold composition direct mineralization and angiogenic tissue formation in an ectopic model. The data suggest that it may be necessary to match the scaffold with a particular cell type and cell-specific pre-treatment to achieve optimal bone formation.

Review of the Pathways Involved in the Osteogenic Differentiation of Adipose-Derived Stem Cells

Grafts and prosthetic materials used for the repair of bone defects are often accompanied by comorbidity and rejection. Therefore, there is an immense need for novel approaches to combating the issues surrounding such defects. Because of their accessibility, substantial proportion, and osteogenic differentiation potential, adipose-derived stem cells (ASCs) make for an ideal source of bone tissue in regenerative medicine. However, efficient induction of ASCs toward an osteoblastic lineage in vivo is met with challenges, and many signaling pathways must come together to secure osteoblastogenesis. Among them are bone morphogenic protein, wingless-related integration site protein, Notch, Hedgehog, fibroblast growth factor, vascular endothelial growth factor, and extracellular regulated-signal kinase. The goal of this literature review is to conglomerate the present research on these pathways to formulate a better understanding of how ASCs are most effectively transformed into bone in the context of tissue engineering.

Human Platelet Lysate as a Functional Substitute for Fetal Bovine Serum in the Culture of Human Adipose Derived Stromal/Stem Cells

INTRODUCTION

Adipose derived stromal/stem cells (ASCs) hold potential as cell therapeutics for a wide range of disease states; however, many expansion protocols rely on the use of fetal bovine serum (FBS) as a cell culture nutrient supplement. The current study explores the substitution of lysates from expired human platelets (HPLs) as an FBS substitute.

METHODS

Expired human platelets from an authorized blood center were lysed by freeze/thawing and used to examine human ASCs with respect to proliferation using hematocytometer cell counts, colony forming unit-fibroblast (CFU-F) frequency, surface immunophenotype by flow cytometry, and tri-lineage (adipocyte, chondrocyte, osteoblast) differentiation potential by histochemical staining.

RESULTS

The proliferation assays demonstrated that HPLs supported ASC proliferation in a concentration dependent manner, reaching levels that exceeded that observed in the presence of 10% FBS. The concentration of 0.75% HPLs was equivalent to 10% FBS when utilized in cell culture media with respect to proliferation, immunophenotype, and CFU-F frequency. When added to osteogenic, adipogenic, and chondrogenic differentiation media, both supplements showed appropriate differentiation by staining.

CONCLUSION

HPLs is an effective substitute for FBS in the culture, expansion and differentiation of human ASCs suitable for pre-clinical studies; however, additional assays and analyses will be necessary to validate HPLs for clinical applications and regulatory approval.

Lentiviral Gene Therapy for Bone Repair Using Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells

Umbilical cord blood (UCB) has been increasingly explored as an alternative source of stem cells for use in regenerative medicine due to several advantages over other stem-cell sources, including the need for less stringent human leukocyte antigen matching. Combined with an osteoinductive signal, UCB-derived mesenchymal stem cells (MSCs) could revolutionize the treatment of challenging bone defects. This study aimed to develop an ex vivo regional gene-therapy strategy using BMP-2-transduced allogeneic UCB-MSCs to promote bone repair. To this end, human UCB-MSCs were transduced with a lentiviral vector carrying the cDNA for BMP-2 (LV-BMP-2). In vitro assays to determine the UCB-MSC osteogenic potential and BMP-2 production were followed by in vivo implantation of LV-BMP-2-transduced UCB-MSCs in a mouse hind-limb muscle pouch. Non-transduced and LV-GFP-transduced UCB-MSCs were used as controls. Transduction with LV-BMP-2 was associated with abundant BMP-2 production and induction of osteogenic differentiation in vitro. Implantation of BMP-2-transduced UCB-MSCs led to robust heterotopic bone formation 4 weeks postoperatively, as seen on radiographs and histology. These results, along with the fact that UCB-MSCs can be easily collected with no donor-site morbidity and low immunogenicity, suggest that UCB might be a preferable allogeneic source of MSCs to develop an ex vivo gene-therapy approach to treat difficult bone-repair scenarios.

Collagen I Promotes Adipocytogenesis in Adipose-Derived Stem Cells In Vitro

A hallmark of ageing is the redistribution of body fat. Particularly, subcutaneous fat decreases paralleled by a decrease of skin collagen I are typical for age-related skin atrophy. In this paper, we hypothesize that collagen I may be a relevant molecule stimulating the differentiation of adipose-derived stem cells (ASCs) into adipocytes augmenting subcutaneous fat. In this context lipogenesis, adiponectin, and collagen I receptor expression were determined. Freshly isolated ASCs were characterized by stemness-associated surface markers by FACS analysis and then transdifferentiated into adipocytes by specific medium supplements. Lipogenesis was evaluated using Nile Red staining and documented by fluorescence microscopy or quantitatively measured by using a multiwell spectrofluorometer. Expression of adiponectin was measured by real-time RT-PCR and in cell-free supernatants by ELISA, and expression of collagen I receptors was observed by western blot analysis. It was found that supports coated with collagen I promote cell adhesion and lipogenesis of ASCs. Interestingly, a reverse correlation to adiponectin expression was observed. Moreover, we found upregulation of the collagen receptor, discoidin domain-containing receptor 2; receptors of the integrin family were absent or downregulated. These findings indicate that collagen I is able to modulate lipogenesis and adiponectin expression and therefore may contribute to metabolic dysfunctions associated with ageing.

Bone defect healing is induced by collagen sponge/polyglycolic acid

We have evaluated the capability of a collagen/poly glycolic acid (PGA) scaffold in regeneration of a calvarial bone defects in rabbits. 4 bone critical size defects (CSD) were created in the calvarial bone of each rabbit. The following 4 treatment modalities were tested (1) a collagen/PGA scaffold (0.52% w/w); (2) the collagen/PGA scaffold (0.52% w/w) seeded with adipose-derived mesenchymal stem cells (AD-MSCs, 1 × 10⁶ cells per each defect); (3) AD-MSCs (1 × 10⁶ cells) no scaffold material, and (4) blank control. The rabbits were then divided into 3 random groups (of 5) and the treatment outcomes were evaluated at 4, 8 and 12 weeks. New bone formation was histologically assessed. Experimental groups were analyzed by CT scan and real-time PCR. Histological analysis of bone defects treated with collagen/PGA alone exhibited significant fibrous connective tissue formation at the 12 weeks of treatments (P ≤ 0.05). There was no significant difference between collagen/PGA alone and collagen/PGA + AD-MSCs groups. The results were confirmed by CT scan data showing healing percentages of 34.20% for the collage/PGA group alone as compared to the control group and no difference with collagen/PGA containing AD-MSCs (1 × 10⁶ cells). RT-PCR analysis also indicated no significant differences between collagen/PGA and collagen/PGA + AD-MSC groups, although both scaffold containing groups significantly express ALP and SIO rather than groups without scaffolds. Although there was no significant difference between the scaffolds containing cells with non-cellular scaffolds, our results indicated that the Collagen/PGA scaffold itself had a significant effect on wound healing as compared to the control group. Therefore, the collagen/PGA scaffold seems to be a promising candidate for research in bone regeneration.

Gene activated adipose tissue fragments as advanced autologous biomaterials for bone regeneration: osteogenic differentiation within the tissue and implications for clinical translation

Cost-effective, expedited approaches for bone regeneration are urgently needed in an ageing population. Bone Morphogenetic Proteins (BMPs) stimulate osteogenesis but their efficacy is impeded by their short half-life. Delivery by genetically modified cells can overcome this problem. However, cell isolation and propagation represent significant obstacles for the translation into the clinic. Instead, complete gene activated fragments of adipose tissue hold great potential for bone repair. Here, using an in-vitro culture system, we investigated whether adenoviral transduction with human BMP-2 can promote osteogenic differentiation within adipose tissue fragments. Osteoinduction in adipose tissue fragments was evaluated by quantitative reverse transcriptase polymerase chain reaction, immunohistology and histomorphometry. BMP-2 transduced adipose tissue synthesized BMP-2 protein over 30 days peaking by day six, which significantly promoted osteogenic differentiation as indicated by increased calcium depositions, up-regulation of bone marker genes, and bone-related protein expression. Our results demonstrate that cells within adipose tissue fragments can differentiate osteogenically after BMP-2 transduction of cells on the surface of the adipose tissue. BMP-2 gene activated adipose tissue represents an advanced osteo-regenerative biomaterial that can actively contribute to osteogenesis and potentially enable the development of a novel, cost-effective, one-step surgical approach to bone repair without the need for cell isolation.

Buccal Fat Pad-Derived Stem Cells in Three-Dimensional Rehabilitation of Large Alveolar Defects: A Report of Two Cases

This case report seeks to describe efficient clinical application of adipose-derived stem cells (AdSCs) originated from buccal fat pad (BFP) in combination with conventional guided bone regeneration as protected healing space for reconstruction of large alveolar defects after extraction of multiple impacted teeth. The first case was a 19-year-old woman with several impacted teeth in the maxillary and mandibular regions, which could not be forced to erupt and were recommended for surgical extraction by the orthodontist. After this procedure, a large bone defect was created, and this space was filled by AdSC loaded natural bovine bone mineral (NBBM), which was protected with lateral ramus cortical plates, microscrews, and collagen membrane. After 6 months of post-guided bone regeneration, the patient received 6 and 7 implant placements, respectively, in the maxilla and mandible. At 10 months postoperatively, radiographic evaluation revealed thorough survival of implants. The second case was a 22-year-old man with the same complaint and large bony defects created after his teeth were extracted. After 6 months of post-guided bone regeneration, he received 4 dental implants in his maxilla and 7 implants in the mandible. At 48 months postoperatively, radiographs showed complete survival of implants. This approach represented a considerable amount of 3-dimensional bone formation in both cases, which enabled us to use dental implant therapy for rehabilitation of the whole dentition. The application of AdSCs isolated from BFP in combination with NBBM can be considered an efficient treatment for bone regeneration in large alveolar bone defects.

Cardiogenic effects of characterized Geum urbanum extracts on adipose-derived human mesenchymal stem cells

Stem cell therapy is considered as a promising treatment for cardiovascular diseases. Adipose-derived mesenchymal stem cells (ADMSCs) have the ability to undergo cardiomyogenesis. Medicinal plants are effective and safe candidates for cell differentiation. Therefore, the aim of our study was to investigate cardiogenic effects of characterized (HPLC–UV) extracts of Geum urbanum on ADMSCs of adipose tissue. The methanolic extracts of the root and aerial parts of G. urbanum were obtained and MTT assay was used for studying their cytotoxic effects. Then, cells were treated with 50 or 100 μg/mL of the extracts from root and aerial parts of G. urbanum. MTT assay showed that the extracts of G. urbanum did not have any toxic effects on ADMSCs. Immunostaining results showed increase in the expression of α-actinin and cardiac troponin I (cTnI), and quantitative real-time reverse-transcription PCR data confirmed the upregulation of ACTN, ACTC1, and TNNI3 genes in ADMSCs after treatment. According to HPLC fingerprinting, some cardiogenic effects of G. urbanum extracts are probably due to ellagic and gallic acid derivatives. Our findings indicated that G. urbanum extracts effectively upregulated some essential cardiogenic markers, which confirmed the therapeutic role of this plant as a traditional cardiac medicine.

Directing adipose-derived stem cells into keratinocyte-like cells: impact of medium composition and culture condition

BACKGROUND

Adipose-derived stem cells (ASC) are known to transdifferentiate into a wide range of different cell species in vitro including along the epidermal lineage. This property makes them a promising tool for regenerative medicine to restore the epidermal barrier.

OBJECTIVE

This study is dedicated to identify in vitro conditions enabling transdifferentiation to a keratinocyte-like phenotype. In particular, the impact of different culture conditions (media compositions, 2D, 3D cultures) and extracellular matrix (ECM) molecules was evaluated.

METHODS

Adipose-derived stem cells derived from subcutaneous abdominal fat were characterized by stemness-associated markers and subjected to different media. Epithelial differentiation in 2D cultures was monitored by pan-cytokeratin expression using flow cytometry and immunocytochemistry. To evaluate the impact of different ECM molecules on epidermal stratification, 3D cultures were produced, lifted to the air-liquid interface (ALI) and examined by histological analysis and quantitative real-time RT-PCR.

RESULTS

We identified a medium composition containing retinoic acid, hydrocortisone, ascorbic acid and BMP-4 enabling maximum pan-cytokeratin expression in 2D cultures. Moreover, adhesion to type IV collagen further promotes the pan-cytokeratin expression. When cultures were lifted to the ALI, significant stratification was observed, particularly in supports coated with type IV collagen or fibronectin. Moreover, epidermal differentiation markers (involucrin, cytokeratin 1 and 14) become induced.

CONCLUSION

Conditions with hampered wound healing such as non-healing ulcers demand new treatment regimes. The here introduced optimized protocols for transdifferentiation of ASC into keratinocyte-like cells may help to establish more effective treatment procedures.

Structure–property relation of porous poly (l-lactic acid) scaffolds fabricated using organic solvent mixtures and controlled cooling rates and its bio-compatibility with human adipose stem cells

Thermally induced phase separation method was used to make porous three-dimensional poly (l-lactic acid) scaffolds. The effect of imposed thermal profile during freezing of the poly (l-lactic acid) in dioxane solution on the scaffold was characterized by their micro-structure, porosity (%), pore sizes’ distribution, and mechanical strength. The porosity (%) decreased considerably with increasing concentrations of poly (l-lactic acid) in the solution, while a decreasing trend was observed with increasing cooling rates. The mechanical strength increases with increase in poly (l-lactic acid) concentration and also with increase in the cooling rate for both types of solvents. Therefore, mechanical strength was increased by higher cooling rates while the porosity (%) remained relatively consistent. Scaffolds made using higher concentrations of poly (l-lactic acid; 7% and 10% w/v) in solvent showed better mechanical strength which improved relatively with increasing cooling rates (1°C–40°C/min). This phenomenon of enhanced structural integrity with increasing cooling rates was more prominent in scaffolds made from higher initial poly (l-lactic acid) concentrations. Human adipose–derived stem cells were cultured on these scaffold (7% and 10% w/v) prepared by thermally induced phase separation at all cooling rates to measure the cell proliferation efficiency as a function of their micro-structural properties. Mean pore sizes played a crucial role in cell proliferation than percent porosity since all scaffolds were >88% porous. The viability percent of human adipose tissue–derived adult stem cells increased consistently with longer periods of culture. Thus, poly (l-lactic acid) scaffolds prepared by thermally controlled thermally induced phase separation method could be a prime candidate for making ex vivo tissue-engineered grafts for surgical implantation.

Gene Therapy for Bone Repair Using Human Cells: Superior Osteogenic Potential of Bone Morphogenetic Protein 2-Transduced Mesenchymal Stem Cells Derived from Adipose Tissue Compared to Bone Marrow

Ex vivo regional gene therapy strategies using animal mesenchymal stem cells genetically modified to overexpress osteoinductive growth factors have been successfully used in a variety of animal models to induce both heterotopic and orthotopic bone formation. However, in order to adapt regional gene therapy for clinical applications, it is essential to assess the osteogenic capacity of transduced human cells and choose the cell type that demonstrates the best clinical potential. Bone-marrow stem cells (BMSC) and adipose-derived stem cells (ASC) were selected in this study for in vitro evaluation, before and after transduction with a lentiviral two-step transcriptional amplification system (TSTA) overexpressing bone morphogenetic protein 2 (BMP-2; LV-TSTA-BMP-2) or green fluorescent protein (GFP; LV-TSTA-GFP). Cell growth, transduction efficiency, BMP-2 production, and osteogenic capacity were assessed. The study demonstrated that BMSC were characterized by a slower cell growth compared to ASC. Fluorescence-activated cell sorting analysis of GFP-transduced cells confirmed successful transduction with the vector and revealed an overall higher but not statistically significant transduction efficiency in ASC versus BMSC (90.2 ± 4.06% vs. 80.4 ± 8.51%, respectively; p = 0.146). Enzyme-linked immunosorbent assay confirmed abundant BMP-2 production by both cell types transduced with LV-TSTA-BMP-2, with BMP-2 production being significantly higher in ASC versus BMSC (239.5 ± 116.55 ng vs. 70.86 ± 24.7 ng; p = 0.001). Quantitative analysis of extracellular deposition of calcium (Alizarin red) and alkaline phosphatase activity showed that BMP-2-transduced cells had a higher osteogenic differentiation capacity compared to non-transduced cells. When comparing the two cell types, ASC/LV-TSTA-BMP-2 demonstrated a significantly higher mineralization potential compared to BMSC/LV-TSTA-BMP-2 7 days post transduction (p = 0.014). In conclusion, this study demonstrates that transduction with LV-TSTA-BMP-2 can significantly enhance the osteogenic potential of both human BMSC and ASC. BMP-2-treated ASC exhibited higher BMP-2 production and greater osteogenic differentiation capacity compared to BMP-2-treated BMSC. These results, along with the fact that liposuction is an easy procedure with lower donor-site morbidity compared to BM aspiration, indicate that adipose tissue might be a preferable source of MSCs to develop a regional gene therapy approach to treat difficult bone-repair scenarios.

The Role of Skeletal Stem Cells in the Reconstruction of Bone Defects

Craniofacial surgery, since its inauguration, has been the culmination of collaborative efforts to solve complex congenital, dysplastic, oncological, and traumatic cranial bone defects. Now, 50 years on from the first craniofacial meeting, the collaborative efforts between surgeons, scientists, and bioengineers are further advancing craniofacial surgery with new discoveries in tissue regeneration. Recent advances in regenerative medicine and stem cell biology have transformed the authors' understanding of bone healing, the role of stem cells governing bone healing, and the effects of the niche environment and extracellular matrix on stem cell fate. This review aims at summarizing the advances within each of these fields.

MAPK signaling has stage-dependent osteogenic effects on human adipose-derived stem cells in vitro

OVERVIEW

The use of pro-osteogenic growth factors, such as BMP2, in human adipose-derived stem cell (ASC) osteogenesis is well described. Because these growth factors work via signal transduction pathways, such as the mitogen-activated protein kinase (MAPK) cascade, a study of the relationship between MAPK signaling and ASC osteogenesis was conducted.

MATERIALS AND METHODS

ERK, JNK, and p38MAPK activation were measured in ASCs osteo-induced using either dexamethasone or vitamin D3 and correlated with mineralization. Activation and mineralization were also measured without dexamethasone or using the glucocorticoid, cortisone. The expression of the MAPK phosphatase, MKP1, and its relationship to mineralization was also assessed. The effect of decreasing MAPK activation on mineralization through the use of exogenous inhibitors was examined along with siRNA-knockdown and adenoviral overexpression of ERK1/2. Finally, the effect of ERK1/2 overexpression on ASCs induced on PLGA scaffolds was assessed.

RESULTS

ASC mineralization in dexamethasone or vitamin D3-induced ASCs correlated with both increased ERK1/2 and JNK1/2 activation. ASCs induced without dexamethasone also mineralized, with JNK1/2 signaling possibly mediating this event. No link between cortisone induction and MAPK signaling could be ascertained. ASCs treated with ERK, JNK, or p38MAPK inhibitors showed decreased osteogenic gene expression and diminished mineralization. Mineralization levels were also affected by viruses designed to inhibit or augment ERK1/2 expression and activity. Finally, ASC mineralization appeared to be a balance between the MAPK kinase activity and MKP1.

CONCLUSIONS

It is likely that MAPK signaling plays a significant role in ASC osteogenesis, affecting differentiation in kinase- and stage-specific manners.

3D printed hyperelastic "bone" scaffolds and regional gene therapy: A novel approach to bone healing

The purpose of this study was to evaluate the viability of human adipose-derived stem cells (ADSCs) transduced with a lentiviral (LV) vector to overexpress bone morphogenetic protein-2 (BMP-2) loaded onto a novel 3D printed scaffold. Human ADSCs were transduced with a LV vector carrying the cDNA for BMP-2. The transduced cells were loaded onto a 3D printed Hyperelastic "Bone" (HB) scaffold. In vitro BMP-2 production was assessed using enzyme-linked immunosorbent assay analysis. The ability of ADSCs loaded on the HB scaffold to induce in vivo bone formation in a hind limb muscle pouch model was assessed in the following groups: ADSCs transduced with LV-BMP-2, LV-green fluorescent protein, ADSCs alone, and empty HB scaffolds. Bone formation was assessed using radiographs, histology and histomorphometry. Transduced ADSCs BMP-2 production on the HB scaffold at 24 hours was similar on 3D printed HB scaffolds versus control wells with transduced cells alone, and continued to increase after 1 and 2 weeks of culture. Bone formation was noted in LV-BMP-2 animals on plain radiographs at 2 and 4 weeks after implantation; no bone formation was noted in the other groups. Histology demonstrated that the LV-BMP-2 group was the only group that formed woven bone and the mean bone area/tissue area was significantly greater when compared with the other groups. 3D printed HB scaffolds are effective carriers for transduced ADSCs to promote bone repair. The combination of gene therapy and tissue engineered scaffolds is a promising multidisciplinary approach to bone repair with significant clinical potential. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1104-1110, 2018.

Cryopreservation Protocols for Human Adipose Tissue Derived Adult Stem Cells

The development of simple but effective storage protocols for adult stem cells will greatly enhance their use and utility in tissue-engineering applications. Cryopreservation has shown to be most promising but is a fairly complex process, necessitating the use of chemicals called cryoprotective agents (CPAs), freezing equipment, and obviously, storage in liquid nitrogen. The purpose of this chapter is to present a general overview of cryopreservation storage techniques and the optimal protocols/results obtained in our laboratory for long-term storage of adult stem cells using freezing storage.

Osteointegration of Porous Poly-ε-Caprolactone-Coated and Previtalised Magnesium Implants in Critically Sized Calvarial Bone Defects in the Mouse Model

Metallic biomaterials are widely used in maxillofacial surgery. While titanium is presumed to be the gold standard, magnesium-based implants are a current topic of interest and investigation due to their biocompatible, osteoconductive and degradable properties. This study investigates the effects of poly-ε-caprolactone-coated and previtalised magnesium implants on osteointegration within murine calvarial bone defects: After setting a 3 mm × 3 mm defect into the calvaria of 40 BALB/c mice the animals were treated with poly-ε-caprolactone-coated porous magnesium implants (without previtalisation or previtalised with either osteoblasts or adipose derived mesenchymal stem cells), porous Ti6Al4V implants or without any implant. To evaluate bone formation and implant degradation, micro-computertomographic scans were performed at day 0, 28, 56 and 84 after surgery. Additionally, histological thin sections were prepared and evaluated histomorphometrically. The outcomes revealed no significant differences within the differently treated groups regarding bone formation and the amount of osteoid. While the implant degradation resulted in implant shifting, both implant geometry and previtalisation appeared to have positive effects on vascularisation. Although adjustments in degradation behaviour and implant fixation are indicated, this study still considers magnesium as a promising alternative to titanium-based implants in maxillofacial surgery in future.

Function of microRNAs in the Osteogenic Differentiation and Therapeutic Application of Adipose-Derived Stem Cells (ASCs)

Traumatic wounds with segmental bone defects represent substantial reconstructive challenges. Autologous bone grafting is considered the gold standard for surgical treatment in many cases, but donor site morbidity and associated post-operative complications remain a concern. Advances in regenerative techniques utilizing mesenchymal stem cell populations from bone and adipose tissue have opened the door to improving bone repair in the limbs, spine, and craniofacial skeleton. The widespread availability, ease of extraction, and lack of immunogenicity have made adipose-derived stem cells (ASCs) particularly attractive as a stem cell source for regenerative strategies. Recently it has been shown that small, non-coding miRNAs are involved in the osteogenic differentiation of ASCs. Specifically, microRNAs such as miR-17, miR-23a, and miR-31 are expressed during the osteogenic differentiation of ASCs, and appear to play a role in inhibiting various steps in bone morphogenetic protein-2 (BMP2) mediated osteogenesis. Importantly, a number of microRNAs including miR-17 and miR-31 that act to attenuate the osteogenic differentiation of ASCs are themselves stimulated by transforming growth factor β-1 (TGFβ-1). In addition, transforming growth factor β-1 is also known to suppress the expression of microRNAs involved in myogenic differentiation. These data suggest that preconditioning strategies to reduce TGFβ-1 activity in ASCs may improve the therapeutic potential of ASCs for musculoskeletal application. Moreover, these findings support the isolation of ASCs from subcutaneous fat depots that tend to have low endogenous levels of TGFβ-1 expression.

Inferior In Vivo Osteogenesis and Superior Angiogenesis of Human Adipose‐Derived Stem Cells Compared with Bone Marrow‐Derived Stem Cells Cultured in Xeno‐Free Conditions

The possibility of using adipose tissue-derived stromal cells (ATSC) as alternatives to bone marrow-derived stromal cells (BMSC) for bone repair has garnered interest due to the accessibility, high cell yield, and rapid in vitro expansion of ATSC. For clinical relevance, their bone forming potential in comparison to BMSC must be proven. Distinct differences between ATSC and BMSC have been observed in vitro and comparison of osteogenic potential in vivo is not clear to date. The aim of the current study was to compare the osteogenesis of human xenofree-expanded ATSC and BMSC in vitro and in an ectopic nude mouse model of bone formation. Human MSC were implanted with biphasic calcium phosphate biomaterials in subcutis pockets for 8 weeks. Implant groups were: BMSC, ATSC, BMSC and ATSC mixed together in different ratios, as well as MSC primed with either osteogenic supplements (250 μM ascorbic acid, 10 mM β-glycerolphosphate, and 10 nM dexamethasone) or 50 ng/ml recombinant bone morphogenetic protein 4 prior to implantation. In vitro results show osteogenic gene expression and differentiation potentials of ATSC. Despite this, ATSC failed to form ectopic bone in vivo, in stark contrast to BMSC, although osteogenic priming did impart minor osteogenesis to ATSC. Neovascularization was enhanced by ATSC compared with BMSC; however, less ATSC engrafted into the implant compared with BMSC. Therefore, in the content of bone regeneration, the advantages of ATSC over BMSC including enhanced angiogenesis, may be negated by their lack of osteogenesis and prerequisite for osteogenic differentiation prior to transplantation. Stem Cells Translational Medicine 2017;6:2160-2172.

Three Dimensional Honeycomb Patterned Fibrinogen Based Nanofibers Induce Substantial Osteogenic Response of Mesenchymal Stem Cells

Stem cells therapy offers a viable alternative for treatment of bone disorders to the conventional bone grafting. However clinical therapies are still hindered by the insufficient knowledge on the conditions that maximize stem cells differentiation. Hereby, we introduce a novel 3D honeycomb architecture scaffold that strongly support osteogenic differentiation of human adipose derived mesenchymal stem cells (ADMSCs). The scaffold is based on electrospun hybrid nanofibers consisting of poly (L-lactide ε-caprolactone) and fibrinogen (PLCL/FBG). Classical fibers orientations, random or aligned were also produced and studied for comparison. The overall morphology of ADMSC's generally followed the nanofibers orientation and dimensionality developing regular focal adhesions and direction-dependent actin cytoskeleton bundles. However, there was an initial tendency for cells rounding on honeycomb scaffolds before ADMSCs formed a distinct bridging network. This specific cells organization appeared to have significant impact on the differentiation potential of ADMSCs towards osteogenic lineage, as indicated by the alkaline phosphatase production, calcium deposition and specific genes expression. Collectively, it was observed synergistic effect of nanofibers with honeycomb architecture on the behavior of ADMSCs entering osteogenic path of differentiation which outlines the potential benefits from insertion of such bioinspired geometrical cues within scaffolds for bone tissue engineering.

Ectopic models for endochondral ossification: comparing pellet and alginate bead culture methods

Key aspects of native endochondral bone development and fracture healing can be mimicked in mesenchymal stem cells (MSCs) through standard in vitro chondrogenic induction. Exploiting this phenomenon has recently emerged as an attractive technique to engineer bone tissue, however, relatively little is known about the best conditions for doing so. The objective of the present study was to compare the bone-forming capacity and angiogenic induction of hypertrophic cell constructs containing human adipose-derived stem cells (hASCs) primed for chondrogenesis in two different culture systems: high-density pellets and alginate bead hydrogels. The hASC constructs were subjected to 4 weeks of identical chondrogenic induction in vitro, encapsulated in an agarose carrier, and then implanted subcutaneously in immune-compromised mice for 8 weeks to evaluate their endochondral potential. At the time of implantation, both pellets and beads expressed aggrecan and type II collagen, as well as alkaline phosphatase (ALP) and type X collagen. Interestingly, ASCs in pellets formed a matrix containing higher glycosaminoglycan and collagen contents than that in beads, and ALP activity per cell was higher in pellets. However, after 8 weeks in vivo, pellets and beads induced an equivalent volume of mineralized tissue and a comparable level of vascularization. Although osteocalcin and osteopontin-positive osteogenic tissue and new vascular growth was found within both types of constructs, all appeared to be better distributed throughout the hydrogel beads. The results of this ectopic model indicate that hydrogel culture may be an attractive alternative to cell pellets for bone tissue engineering via the endochondral pathway. Copyright © 2016 John Wiley & Sons, Ltd.

Hypothermia reduces VEGF-165 expression, but not osteogenic differentiation of human adipose stem cells under hypoxia

Cryotherapy is successfully used in the clinic to reduce pain and inflammation after musculoskeletal damage, and might prevent secondary tissue damage under the prevalent hypoxic conditions. Whether cryotherapy reduces mesenchymal stem cell (MSC) number and differentiation under hypoxic conditions, causing impaired callus formation is unknown. We aimed to determine whether hypothermia modulates proliferation, apoptosis, nitric oxide production, VEGF gene and protein expression, and osteogenic/chondrogenic differentiation of human MSCs under hypoxia. Human adipose MSCs were cultured under hypoxia (37°C, 1% O2), hypothermia and hypoxia (30°C, 1% O2), or control conditions (37°C, 20% O2). Total DNA, protein, nitric oxide production, alkaline phosphatase activity, gene expression, and VEGF protein concentration were measured up to day 8. Hypoxia enhanced KI67 expression at day 4. The combination of hypothermia and hypoxia further enhanced KI67 gene expression compared to hypoxia alone, but was unable to prevent the 1.2-fold reduction in DNA amount caused by hypoxia at day 4. Addition of hypothermia to hypoxic cells did not alter the effect of hypoxia alone on BAX-to-BCL-2 ratio, alkaline phosphatase activity, gene expression of SOX9, COL1, or osteocalcin, or nitric oxide production. Hypothermia decreased the stimulating effect of hypoxia on VEGF-165 gene expression by 6-fold at day 4 and by 2-fold at day 8. Hypothermia also decreased VEGF protein expression under hypoxia by 2.9-fold at day 8. In conclusion, hypothermia decreased VEGF-165 gene and protein expression, but did not affect differentiation, or apoptosis of MSCs cultured under hypoxia. These in vitro results implicate that hypothermia treatment in vivo, applied to alleviate pain and inflammation, is not likely to harm early stages of callus formation.

An Overview of Neural Differentiation Potential of Human Adipose Derived Stem Cells

There is wide interest in application of adult stem cells due to easy to obtain with a minimal patient discomfort, capable of producing cell numbers in large quantities and their immunocompatible properties without restriction by ethical concerns. Among these stem cells, multipotent mesenchymal stem cells (MSCs) from human adipose tissue are considered as an ideal source for various regenerative medicine. In spite of mesodermal origin of human adipose-derived stem cells (hADSCs), these cells have differentiation potential toward mesodermal and non-mesodermal lineages. Up to now, several studies have shown that hADSCs can undergo transdifferentiation and produce cells outside of their lineage, especially into neural cells when they are transferred to a specific cell environment. The purpose of this literature review is to provide an overview of the existing state of knowledge of the differentiation potential of hADSCs, specifically their ability to give rise to neuronal cells. The following review discusses different protocols considered for differentiation of hADSCs to neural cells, the neural markers that are used in each procedure and possible mechanisms that are involved in this differentiation.

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.

Study of the chlorpyrifos neurotoxicity using neural differentiation of adipose tissue-derived stem cells

Chlorpyrifos (CPF) is the most commonly used organophosphorus insecticide which causes neurodevelopmental toxicity. So far, animals have been used as ideal models for neurotoxicity studies, but working with animals is very expensive, laborious, and ethically challenging. This has encouraged researchers to seek alternatives. During recent years, several studies have reported successful differentiation of embryonic and adult stem cells to neurons. This has provided an excellent model for neurotoxicologic studies. In this study, neural differentiation of mouse adipose tissue-derived stem cells (ADSCs) was used as an in vitro model for investigation of CPF neurotoxicity. For this purpose, mouse ADSCs were cultured in a medium containing knockout serum replacement and were treated with different concentrations of CPF at several stages of differentiation. Cytotoxic effect of CPF and the expression of neuron-specific genes and proteins were studied in the differentiating ADSCs. Furthermore, the activity of acetylcholinesterase was assessed by Ellman assay at different stages of differentiation. This study showed that up to 500 μM CPF did not alter viability of the undifferentiated ADSCs, whereas viability of the differentiating cells decreased with 500 μM CPF. CPF upregulated the expression of some neuron-specific genes and seemed to decrease the number of β-tubulin III and MAP2 proteins-expressing cells. There was no detectable acetylcholine esterase activity in differentiated ADSCs. In summary, it was shown that CPF treatment can decrease the viability of ADSC-derived neurons and dysregulate the expression of some neuronal markers through acetylcholinesterase-independent mechanisms. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1510-1519, 2016.

Immunomodulatory Role of Mesenchymal Stem Cell Therapy in Vascularized Composite Allotransplantation

This review aims to summarize contemporary evidence of the in vitro and in vivo immunomodulatory effects of mesenchymal stem cells (MSCs) in promoting vascularized composite allotransplant (VCA) tolerance. An extensive literature review was performed to identify pertinent articles of merit. Prospective preclinical trials in mammal subjects receiving VCA (or skin allograft) with administration of MSCs were reviewed. Prospective clinical trials with intravascular delivery of MSCs in human populations undergoing solid organ transplant were also identified and reviewed. Sixteen preclinical studies are included. Eleven studies compared MSC monotherapy to no therapy; of these, ten reported improved graft survival, which was statistically significantly prolonged in eight. Eight studies analyzed allograft survival with MSC therapy as an adjunct to proven immunosuppressive regimens. In these studies, daily immunosuppression was transiently delivered and then stopped. In all studies, treatment-free graft survival was statistically significantly prolonged in animals that received MSC therapy. MSCs have been safely administered clinically and their use in renal transplant clinical trials provides evidence that they improve allograft transplant tolerance in clinical practice. There is potential for MSC induction therapy to overcome many of the obstacles to widespread VCA in clinical practice. Preclinical studies are needed before MSC-induced VCA tolerance becomes a clinical reality.

Ectopic osteogenic capacity of freshly isolated adipose-derived stromal vascular fraction cells supported with platelet-rich plasma: A simulation of intraoperative procedure

Bone defects represent a serious problem in cranio-maxillofacial surgery. Autologous adipose-derived stromal vascular fraction (SVF) cells in combination with biological factors and bone substitutes were previously proposed as alternative to bone grafting. By simulating an intraoperative procedure we examined osteogenic capacity of the combination of two autologous components, freshly isolated adipose-derived SVF cells, and platelet-rich plasma (PRP), delivered on bone mineral matrix (BMM) carrier (SPB group) in mice ectopic bone forming model. Implantation of BMM only (B group) was a control. The presence of adipose-derived stem cells (ADSCs) in SVF was detected by immunocytochemical analysis. Expression of bone- and endothelial-related genes was compared between freshly isolated SVF and ADSCs obtained from SVF after in vitro cultivation. The implants were analyzed using expression analysis of bone-related genes at one, two, four and eight weeks and histochemical, immunohistochemical and histomorphometrical analyses at two and eight weeks after implantation. Freshly isolated adipose-derived SVF contained ADSCs and exhibited promising osteogenic and vasculogenic capacity. At two and four weeks, significantly higher expression of bone-related genes was detected in SPB group compared to B group. The signs of osteogenic process were more pronounced in SPB than in B implants. By the end of experiment, percentage of infiltrated tissue and vascularization was significantly higher in SPB than in B implants. Adipose-derived SVF cells, PRP and BMM rapidly initiated osteogenesis what makes this combination promising candidate for treatment of bone defects.

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.

Osteoporosis Recovery by Antrodia camphorata Alcohol Extracts through Bone Regeneration in SAMP8 Mice

Antrodia camphorata has previously demonstrated the efficacy in treating cancer and anti-inflammation. In this study, we are the first to evaluate Antrodia camphorata alcohol extract (ACAE) for osteoporosis recovery in vitro with preosteoblast cells (MC3T3-E1) and in vivo with an osteoporosis mouse model established in our previous studies, ovariectomized senescence accelerated mice (OVX-SAMP8). Our results demonstrated that ACAE treatment was slightly cytotoxic to preosteoblast at 25 μg/mL, by which the osteogenic gene expression (RUNX2, OPN, and OCN) was significantly upregulated with an increased ratio of OPG to RANKL, indicating maintenance of the bone matrix through inhibition of osteoclastic pathway. Additionally, evaluation by Alizarin Red S staining showed increased mineralization in ACAE-treated preosteoblasts. For in vivo study, our results indicated that ACAE inhibits bone loss and significantly increases percentage bone volume, trabecular bone number, and bone mineral density in OVX-SAMP8 mice treated with ACAE. Collectively, in vitro and in vivo results showed that ACAE could promote osteogenesis and prevent bone loss and should be considered an evidence-based complementary and alternative medicine for osteoporosis therapy through the maintenance of bone health.

Comparison of the characteristics and multipotential and in vivo cartilage formation capabilities between porcine adipose-derived stem cells and porcine skin-derived stem cell-like cells

OBJECTIVE

To compare the characteristics and multipotential and in vivo cartilage formation capabilities of porcine adipose-derived stem cells (pASCs) with those of porcine skin-derived stem cell-like cells (pSSCs).

ANIMALS

Three 6-month-old female pigs and four 6-week-old female athymic mice.

PROCEDURES

Adipose and skin tissue specimens were obtained from each pig following slaughter and digested to obtain pASCs and pSSCs. For each cell type, flow cytometry and reverse transcription PCR assays were performed to characterize the expression of cell surface and mesenchymal stem cell markers, and in vitro cell cultures were performed to determine the adipogenic, osteogenic, and chondrogenic capabilities. Each cell type was then implanted into athymic mice to determine the extent of in vivo cartilage formation after 6 weeks.

RESULTS

The cell surface and mesenchymal stem cell marker expression patterns, multipotential capability, and extent of in vivo cartilage formation did not differ significantly between pASCs and pSSCs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that pSSCs may be a viable alternative to pASCs as a source of progenitor cells for tissue engineering in regenerative medicine.

Advances in Adipose-Derived Stem Cells Isolation, Characterization, and Application in Regenerative Tissue Engineering

Obesity is a complex, multifactorial disease that has been extensively researched in recent times. Obesity is characterized by excess deposition of adipose tissue in response to surplus energy. Despite the negative connotations of adipose tissue (AT), it serves as a critical endocrine organ. Adipose tissue is a source of several adipokines and cytokines which have been deemed important for both normal metabolic function and disease formation. The discoveries of metabolically active brown AT in adult humans and adipose tissue derived stem cells (ADSC) have been key findings in the past decade with potential therapeutic implications. ADSCs represent an enticing pool of multipotent adult stem cells because of their noncontroversial nature, relative abundance, ease of isolation, and expandability. A decade and a half since the discovery of ADSCs, the scientific community is still working to uncover their therapeutic potential in a wide range of diseases. In this review, we provide an overview of the recent developments in the field of ADSCs and examine their potential use in transplantation and cell-based therapies for the regeneration of diseased organs and systems. We also hope to provide perspective on how to best utilize this readily available, powerful pool of stem cells in the future.

Stem Cells for Bone Regeneration: From Cell-Based Therapies to Decellularised Engineered Extracellular Matrices

Currently, autologous bone grafting represents the clinical gold standard in orthopaedic surgery. In certain cases, however, alternative techniques are required. The clinical utility of stem and stromal cells has been demonstrated for the repair and regeneration of craniomaxillofacial and long bone defects although clinical adoption of bone tissue engineering protocols has been very limited. Initial tissue engineering studies focused on the bone marrow as a source of cells for bone regeneration, and while a number of promising results continue to emerge, limitations to this technique have prompted the exploration of alternative cell sources, including adipose and muscle tissue. In this review paper we discuss the advantages and disadvantages of cell sources with a focus on adipose tissue and the bone marrow. Additionally, we highlight the relatively recent paradigm of developmental engineering, which promotes the recapitulation of naturally occurring developmental processes to allow the implant to optimally respond to endogenous cues. Finally we examine efforts to apply lessons from studies into different cell sources and developmental approaches to stimulate bone growth by use of decellularised hypertrophic cartilage templates.

Repair of critical size defects using bioactive glass seeded with adipose-derived mesenchymal stem cells

Bioactive glass has been demonstrated as a biocompatible bone substitute. However bone healing process can be prolonged due to late resorption of the material. Adipose derived stem cells (ASC) have osteogenic differentiation potential and hence can be a cell source for bone regeneration. The aim of this study was to test whether combination of bioactive glass with ASCs would enhance bone regeneration. Following creation of critical sized defects on the calvaria of 32 Wistar rats, the animals were randomly divided into four groups: Group C (control): Defects were left untreated; Group G: Defects were covered with autologous bone graft; Group BG: Defects were filled with bioactive glass; Group BG/ASC: Defects were filled with bioactive glass seeded with ASCs. The defect size was significantly greater in Group C compared to all other groups. Bone density was significantly lower in Group C compared to Group G and Group BG/ASC. Bone regeneration score of Group C was significantly lower than other groups. Group BG/ASC demonstrated lamellar bone and havers canal formation. The results of this study demonstrated that bioactive glass implanted with ASC is a biocompatible construct stimulating radiologically and histologically evident bone regeneration similar to autologous bone grafting. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1002-1008, 2017.

Advances in Adipose-Derived Stem Cells Isolation, Characterization, and Application in Regenerative Tissue Engineering

Obesity is a complex, multifactorial disease that has been extensively researched in recent times. Obesity is characterized by excess deposition of adipose tissue in response to surplus energy. Despite the negative connotations of adipose tissue (AT), it serves as a critical endocrine organ. Adipose tissue is a source of several adipokines and cytokines which have been deemed important for both normal metabolic function and disease formation. The discoveries of metabolically active brown AT in adult humans and adipose tissue derived stem cells (ADSC) have been key findings in the past decade with potential therapeutic implications. ADSCs represent an enticing pool of multipotent adult stem cells because of their noncontroversial nature, relative abundance, ease of isolation, and expandability. A decade and a half since the discovery of ADSCs, the scientific community is still working to uncover their therapeutic potential in a wide range of diseases. In this review, we provide an overview of the recent developments in the field of ADSCs and examine their potential use in transplantation and cell-based therapies for the regeneration of diseased organs and systems. We also hope to provide perspective on how to best utilize this readily available, powerful pool of stem cells in the future.

Behaviour of telocytes during physiopathological activation

We consider CD34+ stromal cells/telocytes (CD34+ SC/TCs) in normal and pathological conditions. These cells are involved in organisation and control of the extracellular matrix, structural support, creation of microenvironments, intercellular communication, neurotransmission, immunomodulation and immunosurveillance, inhibition of apoptosis, and control, regulation and source of other cell types. CD34+ SC/TCs are widely reported in the origin of interstitial cells of Cajal and in regeneration in the heart, skeletal muscle, skin, respiratory tree, liver, urinary system and the eye. In addition, we contribute CD34+ SC/TC hyperplasia associated with several processes, including neurogenous hyperplasia (neuroma of the appendix), hyperplasia of Leydig cells in undescended testes (Cryptorchidism), peripheral areas of inflammatory/repair processes (pericicatricial tissue and transitional zones between diseased segments in Crohn's disease and normal bowel), benign tumours (neurofibromas, Antoni-B zones of neurilemmomas, granular cell tumours, and melanocytic nevi) and in some lesions with myxoid, oedematous and degenerative changes (Reinke's oedema, myxomatous mitral valve degeneration, thyroid-associated ophthalmopathy and basophilic degenerative changes of the collagen in the dermis). We pay particular attention to the role of CD34+ SC/TCs during repair through granulation tissue, including morphologic changes, loss of CD34 expression and gain of αSMA expression with myofibroblast transformation, and interactions with pericytes, endothelial and inflammatory cells. Finally, we consider CD34 or αSMA expression in stromal cells of malignant epithelial tumours, and the role of CD34+ SC/TCs in the origin of carcinoma-associated fibroblasts (CAFs) and myofibroblasts. In conclusion, CD34+ SC/TCs play an important role in the maintenance and modulation of tissue homeostasis and in morphogenesis/renewal/repair.