Do adipose tissue-derived mesenchymal stem cells have the same osteogenic and chondrogenic potential as bone marrow-derived cells?

Mesenchymal Stromal Cells as Cell-Based Therapeutics for Wound Healing

Chronic wounds are a source of substantial morbidity for patients and are a major financial burden for the healthcare system. There are no current therapies that reliably improve nonhealing wounds or reverse pathological scarring. Mesenchymal stromal cells (MSCs) are a promising source of novel cell-based therapies due to the ease of their harvest and their integral role in the native wound repair process. Recent work has addressed the problems of loss of plasticity and off-target delivery through use of modern bioengineering techniques. Here we describe the applications of MSCs harvested from different sources to the wound healing process and recent advances in delivery of MSCs to targeted sites of injury.

Tissue engineering strategies for promoting vascularized bone regeneration

This review focuses on current tissue engineering strategies for promoting vascularized bone regeneration. We review the role of angiogenic growth factors in promoting vascularized bone regeneration and discuss the different therapeutic strategies for controlled/sustained growth factor delivery. Next, we address the therapeutic uses of stem cells in vascularized bone regeneration. Specifically, this review addresses the concept of co-culture using osteogenic and vasculogenic stem cells, and how adipose derived stem cells compare to bone marrow derived mesenchymal stem cells in the promotion of angiogenesis. We conclude this review with a discussion of a novel approach to bone regeneration through a cartilage intermediate, and discuss why it has the potential to be more effective than traditional bone grafting methods.

Unraveling mechanisms of mesenchymal stromal cell-mediated immunomodulation through patient monitoring and product characterization

Mesenchymal stromal cells (MSCs) are increasingly used in the treatment of a variety of clinical conditions and to modulate immune responses in conditions related to auto-/alloimmunity, including graft-versus-host disease (GvHD). Although pilot data are promising, treatment responses have been highly variable, and further development of this as a therapeutic modality depends on increased insight into the properties of clinical MSC products and on understanding the mechanisms underlying responses in patients. Here we review the mechanisms that possibly underlie the capacity of MSCs to treat auto-/alloimmunity, and describe how patient monitoring can help to identify the in vivo mechanisms of action in the treatment of GvHD. Since MSCs used in the clinic originate from various donors and from a heterogeneous population of cells, we will also discuss recent insights into MSC heterogeneity and their implications for clinical MSC products. Finally, we describe a framework to improve our understanding of the efficacy and working mechanism of MSCs, which involves patient monitoring and more extensive characterization of the heterogeneity within and between different MSC preparations.

Impact of tissue-specific stem cells on lineage-specific differentiation: a focus on the musculoskeletal system

Tissue-specific stem cells are found throughout the body and, with proper intervention and environmental cues, these stem cells exercise their capabilities for differentiation into several lineages to form cartilage, bone, muscle, and adipose tissue in vitro and in vivo. Interestingly, it has been widely demonstrated that they do not differentiate with the same efficacy during lineage-specific differentiation studies, as the tissue-specific stem cells are generally more effective when differentiating toward the tissues from which they were derived. This review focuses on four mesodermal lineages for tissue-specific stem cell differentiation: adipogenesis, chondrogenesis, myogenesis, and osteogenesis. It is intended to give insight into current multilineage differentiation and comparative research, highlight and contrast known trends regarding differentiation, and introduce supporting evidence which demonstrates particular tissue-specific stem cells' superiority in lineage-specific differentiation, along with their resident tissue origins and natural roles. In addition, some epigenetic and transcriptomic differences between stem cells which may explain the observed trends are discussed.

Evaluation and comparison of the in vitro characteristics and chondrogenic capacity of four adult stem/progenitor cells for cartilage cell-based repair

Cell-based therapy is being considered as a promising approach to regenerate damaged cartilage. Though, autologous chondrocyte implantation is the most effective strategy currently in use, but is hampered by some drawbacks seeking comprehensive research to surmount existing limitations or introducing alternative cell sources. In this study, we aimed to evaluate and compare the in vitro characteristics and chondrogenic capacity of some easily available adult cell sources for use in cartilage repair which includes: bone marrow-derived mesenchymal stem cells (MSC), adipose tissue-derived MSC, articular chondrocyte progenitors, and nasal septum-derived progenitors. Human stem/progenitor cells were isolated and expanded. Cell's immunophenotype, biosafety, and cell cycle status were evaluated. Also, cells were seeded onto aligned electrospun poly (l-lactic acid)/poly (ε-caprolactone) nanofibrous scaffolds and their proliferation rate as well as chondrogenic potential were assessed. Cells were almost phenotypically alike as they showed similar cell surface marker expression pattern. The aligned nanofibrous hybrid scaffolds could support the proliferation and chondrogenic differentiation of all cell types. However, nasal cartilage progenitors showed a higher proliferation potential and a higher chondrogenic capacity. Though, mostly similar in the majority of the studied features, nasal septum progenitors demonstrated a higher chondrogenic potential that in combination with their higher proliferation rate and easier access to the source tissue, introduces it as a promising cell source for cartilage tissue engineering and regenerative medicine. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 600-610, 2016.

Human embryonic stem cell derived-mesenchymal stem cells: an alternative mesenchymal stem cell source for regenerative medicine therapy

AIM

To enumerate and characterize mesenchymal stem cells (MSC) derived from human embryonic stem cells (hESC) for clinical application.

MATERIALS & METHODS

hESC were differentiated into hESC-MSC and characterized by the expression of surface markers using flow cytometry. hESC-MSC were evaluated with respect to growth kinetics, colony-forming potential, as well as osteogenic and adipogenic differentiation capacity. Immunosuppressive effects were assessed using peripheral blood mononuclear cell (PBMC) proliferation and cytotoxicity assays.

RESULTS

hESC-MSC showed similar morphology, and cell surface markers as adipose (AMSC) and bone marrow-derived MSC (BMSC). hESC-MSC exhibited a higher growth rate during early in vitro expansion and equivalent adipogenic and osteogenic differentiation and colony-forming potential as AMSC and BMSC. hESC-MSC demonstrated similar immunosuppressive effects as AMSC and BMSC.

CONCLUSION

hESC-MSC were comparable to BMSC and AMSC and hence can be used as an alternative source of MSC for clinical applications.

Adipose-derived Mesenchymal Stem Cells Are Phenotypically Superior for Regeneration in the Setting of Osteonecrosis of the Femoral Head

BACKGROUND

Bone marrow-derived mesenchymal stem cells (bmMSCs) have been used as a cellular therapeutic option for treatment of osteonecrosis of the femoral head. However, use of bmMSCs as a treatment adjuvant for orthopaedic disorders in general has achieved limited success. Adipose-derived MSCs (aMSCs) may be a more-efficient regenerative cell source given their greater quantity and protection from physiologic stress.

QUESTIONS/PURPOSES

We asked the following questions in a paired analysis of MSCs from patients with osteonecrosis: (1) Is there a difference in proliferation potential between aMSCs and bmMSCs? (2) Is there a difference in osteogenic differentiation potential between aMSCs and bmMSCs? (3) Are genetic pathways differentially expressed between aMSCs and bmMSCs that may govern functional phenotypic discrepancies?

METHODS

Periarticular samples of adipose tissue and bone marrow from the femoral canal were obtained from 15 patients undergoing hip replacement for late-stage (Steinberg Stages III-VI) osteonecrosis. MSCs were isolated from both tissue sources and taken through a standardized 20-day cell division protocol to establish cumulative cell count. They also were grown in osteogenic differentiation media for 14 days with subsequent measurement of alkaline phosphatase in units of optical density. RNA was isolated from aMSCs and bmMSCs in five patients to assess differentially expressed genetic pathways using the Affymetrix GeneChip Human Transcriptome Array 2.0 platform.

RESULTS

Proliferation capacity was increased by fourfold in aMSCs compared with bmMSCs after 20 days in culture. The mean difference in cumulative cell count was 3.99 × 10(8) cells (SD = 1.67 × 10(8) cells; 95% CI, 3.07 × 10(8)-4.92 × 10(8) cells; p < 0.001). Bone differentiation efficiency as measured by optical density was increased by 2.25-fold in aMSCs compared with bmMSCs. The mean difference in optical density was 1.27 (SD = 0.34; 95% CI, 1.08-1.46; p < 0.001). RNA transcriptome analysis showed 284 genes that met statistical (p < 0.05) and biological (fold change > 1.5) significance cutoffs for differential expression between cell populations. Subsequent network topology of differentially expressed genes showed alterations in pathways critical for musculoskeletal tissue development in addition to many nonspecific findings.

CONCLUSIONS

aMSCs outperform bmMSCs in growth rate and bone differentiation potential in the setting of osteonecrosis, suggesting they may provide a more-potent regenerative therapeutic strategy in this population. Differential expression of genes and cellular pathways highlighted in this study may provide therapeutic targets for cellular optimization or acellular treatment strategies.

CLINICAL RELEVANCE

aMSCs may provide a more robust cellular therapeutic than bmMSCs for treatment of osteonecrosis. Ideally, a well-designed prospective study will be able to evaluate the efficacy of these cellular therapies side-by-side in patients with bilateral early stage disease.

An In Vitro Comparison of the Incorporation, Growth, and Chondrogenic Potential of Human Bone Marrow versus Adipose Tissue Mesenchymal Stem Cells in Clinically Relevant Cell Scaffolds Used for Cartilage Repair

AIM

To compare the incorporation, growth, and chondrogenic potential of bone marrow (BM) and adipose tissue (AT) mesenchymal stem cells (MSCs) in scaffolds used for cartilage repair.

METHODS

Human BM and AT MSCs were isolated, culture expanded, and characterised using standard protocols, then seeded into 2 different scaffolds, Chondro-Gide or Alpha Chondro Shield. Cell adhesion, incorporation, and viable cell growth were assessed microscopically and following calcein AM/ethidium homodimer (Live/Dead) staining. Cell-seeded scaffolds were treated with chondrogenic inducers for 28 days. Extracellular matrix deposition and soluble glycosaminoglycan (GAG) release into the culture medium was measured at day 28 by histology/immunohistochemistry and dimethylmethylene blue assay, respectively.

RESULTS

A greater number of viable MSCs from either source adhered and incorporated into Chondro-Gide than into Alpha Chondro Shield. In both cell scaffolds, this incorporation represented less than 2% of the cells that were seeded. There was a marked proliferation of BM MSCs, but not AT MSCs, in Chondro-Gide. MSCs from both sources underwent chondrogenic differentiation following induction. However, cartilaginous extracellular matrix deposition was most marked in Chondro-Gide seeded with BM MSCs. Soluble GAG secretion increased in chondrogenic versus control conditions. There was no marked difference in GAG secretion by MSCs from either cell source.

CONCLUSION

Chondro-Gide and Alpha Chondro Shield were permissive to the incorporation and chondrogenic differentiation of human BM and AT MSCs. Chondro-Gide seeded with BM MSCs demonstrated the greatest increase in MSC number and deposition of a cartilaginous tissue.

Mesenchymal stem cell therapy for osteoarthritis: current perspectives

Osteoarthritis (OA) is a painful chronic condition with a significant impact on quality of life. The societal burden imposed by OA is increasing in parallel with the aging population; however, no therapies have demonstrated efficacy in preventing the progression of this degenerative joint disease. Current mainstays of therapy include activity modification, conservative pain management strategies, weight loss, and if necessary, replacement of the affected joint. Mesenchymal stem cells (MSCs) are a multipotent endogenous population of progenitors capable of differentiation to musculoskeletal tissues. MSCs have a well-documented immunomodulatory role, managing the inflammatory response primarily through paracrine signaling. Given these properties, MSCs have been proposed as a potential regenerative cell therapy source for patients with OA. Research efforts are focused on determining the ideal source for derivation, as MSCs are native to several tissues. Furthermore, optimizing the mode of delivery remains a challenge both for appropriate localization of MSCs and for directed guidance toward stemming the local inflammatory process and initiating a regenerative response. Scaffolds and matrices with growth factor adjuvants may prove critical in this effort. The purpose of this review is to summarize the current state of MSC-based therapeutics for OA and discuss potential barriers that must be overcome for successful implementation of cell-based therapy as a routine treatment strategy in orthopedics.

Mesenchymal stromal cells and chronic inflammatory bowel disease

Recent experimental findings have shown the ability of mesenchymal stromal cells (MSCs) to home to damaged tissues and to produce paracrine factors with anti-inflammatory properties, potentially resulting in reduction of inflammation and functional recovery of the damaged tissues. Prompted by these intriguing properties and on the basis of encouraging preclinical data, MSCs are currently being studied in several immune-mediated disorders. Inflammatory bowel diseases (IBD) represent a setting in which MSCs-based therapy has been extensively investigated. Phase I and II studies have documented the safety and feasibility of MSCs. However, efficacy results have so far been conflicting. In this review, we will discuss the biologic rationale that makes MSCs a promising therapeutic tool for IBD, and analyze recent experimental and clinical findings, highlighting current limitations and future perspectives of MSCs-related immunotherapy for IBD.

Mesenchymal stromal cells and hematopoietic stem cell transplantation

Mesenchymal stromal cells (MSCs) comprise a heterogeneous population of multipotent cells that can be isolated from various human tissues and culture-expanded ex vivo for clinical use. Due to their immunoregulatory properties and their ability to secrete growth factors, MSCs play a key role in the regulation of hematopoiesis and in the modulation of immune responses against allo- and autoantigens. In light of these properties, MSCs have been employed in clinical trials in the context of hematopoietic stem cell transplantation (HSCT) to facilitate engraftment of hematopoietic stem cells (HSCs) and to prevent graft failure, as well as to treat steroid-resistant acute graft-versus-host disease (GvHD). The available clinical evidence derived from these studies indicates that MSC administration is safe. Moreover, promising preliminary results in terms of efficacy have been reported in some clinical trials, especially in the treatment of acute GvHD. In this review we critically discuss recent advances in MSC therapy by reporting on the most relevant studies in the field of HSCT.

Cartilage tissue engineering: recent advances and perspectives from gene regulation/therapy

Diseases in articular cartilages affect millions of people. Despite the relatively simple biochemical and cellular composition of articular cartilages, the self-repair ability of cartilage is limited. Successful cartilage tissue engineering requires intricately coordinated interactions between matrerials, cells, biological factors, and phycial/mechanical factors, and still faces a multitude of challenges. This article presents an overview of the cartilage biology, current treatments, recent advances in the materials, biological factors, and cells used in cartilage tissue engineering/regeneration, with strong emphasis on the perspectives of gene regulation (e.g., microRNA) and gene therapy.

Cell-based bone regeneration for alveolar ridge augmentation--cell source, endogenous cell recruitment and immunomodulatory function

Alveolar ridge plays a pivotal role in supporting dental prosthesis particularly in edentulous and semi-dentulous patients. However the alveolar ridge undergoes atrophic change after tooth loss. The vertical and horizontal volume of the alveolar ridge restricts the design of dental prosthesis; thus, maintaining sufficient alveolar ridge volume is vital for successful oral rehabilitation. Recent progress in regenerative approaches has conferred marked benefits in prosthetic dentistry, enabling regeneration of the atrophic alveolar ridge. In order to achieve successful alveolar ridge augmentation, sufficient numbers of osteogenic cells are necessary; therefore, autologous osteoprogenitor cells are isolated, expanded in vitro, and transplanted to the specific anatomical site where the bone is required. Recent studies have gradually elucidated that transplanted osteoprogenitor cells are not only a source of bone forming osteoblasts, they appear to play multiple roles, such as recruitment of endogenous osteoprogenitor cells and immunomodulatory function, at the forefront of bone regeneration. This review focuses on the current consensus of cell-based bone augmentation therapies with emphasis on cell sources, transplanted cell survival, endogenous stem cell recruitment and immunomodulatory function of transplanted osteoprogenitor cells. Furthermore, if we were able to control the mobilization of endogenous osteoprogenitor cells, large-scale surgery may no longer be necessary. Such treatment strategy may open a new era of safer and more effective alveolar ridge augmentation treatment options.

Adipose-derived mesenchymal stem cell administration does not improve corneal graft survival outcome

The effect of local and systemic injections of mesenchymal stem cells derived from adipose tissue (AD-MSC) into rabbit models of corneal allograft rejection with either normal-risk or high-risk vascularized corneal beds was investigated. The models we present in this study are more similar to human corneal transplants than previously reported murine models. Our aim was to prevent transplant rejection and increase the length of graft survival. In the normal-risk transplant model, in contrast to our expectations, the injection of AD-MSC into the graft junction during surgery resulted in the induction of increased signs of inflammation such as corneal edema with increased thickness, and a higher level of infiltration of leukocytes. This process led to a lower survival of the graft compared with the sham-treated corneal transplants. In the high-risk transplant model, in which immune ocular privilege was undermined by the induction of neovascularization prior to graft surgery, we found the use of systemic rabbit AD-MSCs prior to surgery, during surgery, and at various time points after surgery resulted in a shorter survival of the graft compared with the non-treated corneal grafts. Based on our results, local or systemic treatment with AD-MSCs to prevent corneal rejection in rabbit corneal models at normal or high risk of rejection does not increase survival but rather can increase inflammation and neovascularization and break the innate ocular immune privilege. This result can be partially explained by the immunomarkers, lack of immunosuppressive ability and immunophenotypical secretion molecules characterization of AD-MSC used in this study. Parameters including the risk of rejection, the inflammatory/vascularization environment, the cell source, the time of injection, the immunosuppression, the number of cells, and the mode of delivery must be established before translating the possible benefits of the use of MSCs in corneal transplants to clinical practice.

Stromal cells and stem cells in clinical bone regeneration

Stem-cell-mediated bone repair has been used in clinical trials for the regeneration of large craniomaxillofacial defects, to slow the process of bone degeneration in patients with osteonecrosis of the femoral head and for prophylactic treatment of distal tibial fractures. Successful regenerative outcomes in these investigations have provided a solid foundation for wider use of stromal cells in skeletal repair therapy. However, employing stromal cells to facilitate or enhance bone repair is far from being adopted into clinical practice. Scientific, technical, practical and regulatory obstacles prevent the widespread therapeutic use of stromal cells. Ironically, one of the major challenges lies in the limited understanding of the mechanisms via which transplanted cells mediate regeneration. Animal models have been used to provide insight, but these models largely fail to reproduce the nuances of human diseases and bone defects. Consequently, the development of targeted approaches to optimize cell-mediated outcomes is difficult. In this Review, we highlight the successes and challenges reported in several clinical trials that involved the use of bone-marrow-derived mesenchymal or adipose-tissue-derived stromal cells. We identify several obstacles blocking the mainstream use of stromal cells to enhance skeletal repair and highlight technological innovations or areas in which novel techniques might be particularly fruitful in continuing to advance the field of skeletal regenerative medicine.

Ultraviolet irradiation enhanced bioactivity and biological response of mesenchymal stem cells on micro-arc oxidized titanium surfaces

This present study investigated the effect of ultraviolet (UV) irradiation on bioactivity of micro-arc oxidized (MAO) titanium surface in vitro by cell culture medium immersion test and interactions with rat-derived mesenchymal stem cells (MSCs). UV-irradiated MAO surface exhibited no obvious changes in surface roughness, morphology, and phase composition when compared with MAO-only surface. However, in cell culture medium immersion test, markedly more bone-like apatite was formed on UV-modified samples than on MAO sample. Rat bone marrow- and adipose tissue-derived MSCs cultured on UV-modified samples displayed accelerated attachment, significant higher levels of alkaline phosphatase (ALP) activity, and up-regulated osteogenesis-related mRNA expression than MAO sample. XPS results provided direct evidence that the amount of basic hydroxyl groups increased with UV irradiation time, which could be one of the key mechanisms underlying their improved bioactivity.

Impact of source tissue and ex vivo expansion on the characterization of goat mesenchymal stem cells

BACKGROUND

There is considerable interest in using goats as models for genetically engineering dairy animals and also for using stem cells as therapeutics for bone and cartilage repair. Mesenchymal stem cells (MSCs) have been isolated and characterized from various species, but are poorly characterized in goats.

RESULTS

Goat MSCs isolated from bone marrow (BM-MSCs) and adipose tissue (ASCs) have the ability to undergo osteogenic, adipogenic and chondrogenic differentiation. Cytochemical staining and gene expression analysis show that ASCs have a greater capacity for adipogenic differentiation compared to BM-MSCs and fibroblasts. Different methods of inducing adipogenesis also affect the extent and profile of adipogenic differentiation in MSCs. Goat fibroblasts were not capable of osteogenesis, hence distinguishing them from the MSCs. Goat MSCs and fibroblasts express CD90, CD105, CD73 but not CD45, and exhibit cytoplasmic localization of OCT4 protein. Goat MSCs can be stably transfected by Nucleofection, but, as evidenced by colony-forming efficiency (CFE), yield significantly different levels of progenitor cells that are robust enough to proliferate into colonies of integrants following G418 selection. BM-MSCs expanded over increasing passages in vitro maintained karyotypic stability up to 20 passages in culture, exhibited an increase in adipogenic differentiation and CFE, but showed altered morphology and amenability to genetic modification by selection.

CONCLUSIONS

Our findings provide characterization information on goat MSCs, and show that there can be significant differences between MSCs isolated from different tissues and from within the same tissue. Fibroblasts do not exhibit trilineage differentiation potential at the same capacity as MSCs, making it a more reliable method for distinguishing MSCs from fibroblasts, compared to cell surface marker expression.

Mesenchymal stromal cells: sensors and switchers of inflammation

In addition to their stem/progenitor properties, mesenchymal stromal cells (MSCs) possess broad immunoregulatory properties that are being investigated for potential clinical application in treating immune-based disorders. An informed view of the scope of this clinical potential will require a clear understanding of the dynamic interplay between MSCs and the innate and adaptive immune systems. In this Review, we outline current insights into the ways in which MSCs sense and control inflammation, highlighting the central role of macrophage polarization. We also draw attention to functional differences seen between vivo and in vitro contexts and between species. Finally, we discuss progress toward clinical application of MSCs, focusing on GvHD as a case study.

Long-term tracking of segmental bone healing mediated by genetically engineered adipose-derived stem cells: focuses on bone remodeling and potential side effects

We previously showed that transplantation of adipose-derived stem cells (ASCs) engineered with hybrid baculovirus (BV) persistently expressing bone morphogenetic protein 2 (BMP2)/vascular endothelial growth factor (VEGF) into segmental defects in New Zealand White (NZW) rabbits led to successful defect reunion. By using microcomputed tomography and histology, here we further demonstrated that transplanting the hybrid BV-engineered ASCs into the massive defects (10 mm in length) at the femoral diaphysis of NZW rabbits resulted in trabecular bone formation in the interior via endochondral ossification and bone remodeling at 3 months post-transplantation. The progression of bone remodeling gave rise to the resorption of trabecular bone and conspicuous reconstruction of medullary cavity and cortical bone with lamellar structure at 8 months post-transplantation, hence conferring mechanical properties that were comparable to those of nonoperated femora. Importantly, X-ray, positron emission tomography/computed tomography scans, and histopathology revealed no signs of heterotopic bone formation and tumor formation. These data altogether attested that the genetically engineered ASCs and prolonged BMP2/VEGF expression not only healed and remodeled the stringent segmental defects, but also revitalized the defects into living bone tissues that structurally and biomechanically resembled intact bones without appreciable side effects, making it one step closer to translate this technology to the clinical setting.

Characterization of mesenchymal stem cells derived from rat bone marrow and adipose tissue: a comparative study

Background and Objectives:

Stem cell technology offers a new hope for many chronic disorders patients. The types of stem cells are different with many differences existing between each type. Mesenchymal stem cells (MSCs) represent one type of adult stem cells that can be easily isolated, then re-transplanted to the patients. This offers potential for their future application in treating many disorders without fear of rejection possibility. MSCs can be isolated from different sources e.g. bone marrow (BMSCs) and adipose tissue (ADSCs). In the present study we compared BMSCs and ADSCs isolated from Sprague-Dawley rats.

Methods and Results:

For this comparison, immunophenotyping, the analysis of growth rates, proliferation by colony forming unit-fibroblast assay, population doubling time, and trilineage differentiation assays were performed for both BMSCs and ADSCs. The findings revealed that despite no difference in immunphenotypic character between BMSC and ADSC, a better proliferative capacity was observed for ADSCs which would advocate their better use in regenerative applications. On the other hand, BMSCs showed more potential for osteogenic and chondrogenic differentiation.

Conclusions:

Our study showed that, despite many similarities between both types of cells, there are differences existing which can offer assistance on choosing type of cell to be used in specific diseases. Although ADSCs seem more promising for regenerative application generally, BMSCs may represent a better choice for treating bone disorders.

Concise Review: Differentiation of Human Adult Stem Cells Into Hepatocyte-like Cells In vitro

Adult stem cells (ASCs) are undifferentiated cells found throughout the body that divide to replenish dying cells and regenerate damaged tissues, which are the powerful sources for cell therapy and tissue engineering. Bone marrow-derived mesenchymal stem cells (BMSCs), adipose tissue-derived mesenchymal stem cells (ADSCs), and peripheral blood monocytes (PBMCs) are the common ASCs, and many studies indicated that ASCs isolated from various adult tissues could be induced to hepatocyte-like cells in vitro. However, the isolation, culture protocols, characterization of ASCs and hepatocyte-like cells are different. This review aims to describe the isolation and culture procedures for ASCs, to summarize the molecular characterization of ASCs, to characterize function of hepatocyte-like cells, and to discuss the future role of ASCs in cell therapy and tissue engineering.

Paracrine effect of mesenchymal stem cells derived from human adipose tissue in bone regeneration

Mesenchymal stem cell (MSC) transplantation has proved to be a promising strategy in cell therapy and regenerative medicine. Although their mechanism of action is not completely clear, it has been suggested that their therapeutic activity may be mediated by a paracrine effect. The main goal of this study was to evaluate by radiographic, morphometric and histological analysis the ability of mesenchymal stem cells derived from human adipose tissue (Ad-MSC) and their conditioned medium (CM), to repair surgical bone lesions using an in vivo model (rabbit mandibles). The results demonstrated that both, Ad-MSC and CM, induce bone regeneration in surgically created lesions in rabbit's jaws, suggesting that Ad-MSC improve the process of bone regeneration mainly by releasing paracrine factors. The evidence of the paracrine effect of MSC on bone regeneration has a major impact on regenerative medicine, and the use of their CM can address some issues and difficulties related to cell transplants. In particular, CM can be easily stored and transported, and is easier to handle by medical personnel during clinical procedures.

Comparison of the osteogenic potential of mesenchymal stem cells from the bone marrow and adipose tissue of young dogs

BACKGROUND

The aim of the present study was to compare the osteogenic potential of mesenchymal stem cells extracted from the bone marrow (BM-MSCs) and adipose tissue (AD-MSCs) of young dogs. The following parameters were assessed: dimethyl thiazolyl diphenyl tetrazolium (MTT) conversion, alkaline phosphatase (ALP) activity, collagen and mineralised matrix synthesis, and the expressions of osterix, bone sialoprotein (BSP), and osteocalcin (OC).

RESULTS

MTT conversion was greater in BM-MSCs compared to AD-MSCs after 14 and 21 days of differentiation; ALP activity was greater in differentiated AD-MSCs on day 7; collagen synthesis was greater in BM-MSCs on days 14 and 21; the percentage of mineralized area per field was greater in BM-MSCs compared to AD-MSCs; osterix expression was greater in BM-MSCs in days 14 and 21, and BSP and OC expression levels were greater in BM-MSCs at all the investigation time-points.

CONCLUSIONS

It was concluded that the osteogenic potential was greater in BM-MSCs than AD-MSCs when extracted from young dogs.

Programmed Application of Transforming Growth Factor β3 and Rac1 Inhibitor NSC23766 Committed Hyaline Cartilage Differentiation of Adipose-Derived Stem Cells for Osteochondral Defect Repair

Hyaline cartilage differentiation is always the challenge with application of stem cells for joint repair. Transforming growth factors (TGFs) and bone morphogenetic proteins can initiate cartilage differentiation but often lead to hypertrophy and calcification, related to abnormal Rac1 activity. In this study, we developed a strategy of programmed application of TGFβ3 and Rac1 inhibitor NSC23766 to commit the hyaline cartilage differentiation of adipose-derived stem cells (ADSCs) for joint cartilage repair. ADSCs were isolated and cultured in a micromass and pellet culture model to evaluate chondrogenic and hypertrophic differentiation. The function of Rac1 was investigated with constitutively active Rac1 mutant and dominant negative Rac1 mutant. The efficacy of ADSCs with programmed application of TGFβ3 and Rac1 inhibitor for cartilage repair was studied in a rat model of osteochondral defects. The results showed that TGFβ3 promoted ADSCs chondro-lineage differentiation and that NSC23766 prevented ADSC-derived chondrocytes from hypertrophy in vitro. The combination of ADSCs, TGFβ3, and NSC23766 promoted quality osteochondral defect repair in rats with much less chondrocytes hypertrophy and significantly higher International Cartilage Repair Society macroscopic and microscopic scores. The findings have illustrated that programmed application of TGFβ3 and Rac1 inhibitor NSC23766 can commit ADSCs to chondro-lineage differentiation and improve the efficacy of ADSCs for cartilage defect repair. These findings suggest a promising stem cell-based strategy for articular cartilage repair.

Osteogenic potential: Comparison between bone marrow and adipose-derived mesenchymal stem cells

Bone tissue engineering (BTE) is now a promising research issue to improve the drawbacks from traditional bone grafting procedure such as limited donor sources and possible complications. Stem cells are one of the major factors in BTE due to the capability of self renewal and multi-lineage differentiation. Unlike embryonic stem cells, which are more controversial in ethical problem, adult mesenchymal stem cells are considered to be a more appropriate cell source for BTE. Bone marrow mesenchymal stem cells (BMSCs) are the earliest-discovered and well-known stem cell source using in BTE. However, the low stem cell yield requiring long expansion time in vitro, pain and possible morbidities during bone marrow aspiration and poor proliferation and osteogenic ability at old age impede its’ clinical application. Afterwards, a new stem cell source coming from adipose tissue, so-called adipose-derived stem cells (ASCs), is found to be more suitable in clinical application because of high stem cells yield from lipoaspirates, faster cell proliferation and less discomfort and morbidities during harvesting procedure. However, the osteogenic capacity of ASCs is now still debated because most papers described the inferior osteogenesis of ASCs than BMSCs. A better understanding of the osteogenic differences between ASCs and BMSCs is crucial for future selection of cells in clinical application for BTE. In this review, we describe the commonality and difference between BMSCs and ASCs by cell yield, cell surface markers and multiple-differentiation potential. Then we compare the osteogenic capacity in vitro and bone regeneration ability in vivo between BMSCs and ASCs based on the literatures which utilized both BMSCs and ASCs simultaneously in their articles. The outcome indicated both BMSCs and ASCs exhibited the osteogenic ability to a certain extent both in-vitro and in-vivo. However, most in-vitro study papers verified the inferior osteogenesis of ASCs; conversely, in-vivo research reviews revealed more controversies in this issue. We expect the new researchers can have a quick understanding of the progress in this filed and design a more comprehensive research based on this review.

Enhancing chondrogenic phenotype for cartilage tissue engineering: monoculture and coculture of articular chondrocytes and mesenchymal stem cells

Articular cartilage exhibits an inherently low rate of regeneration. Consequently, damage to articular cartilage often requires surgical intervention. However, existing treatments generally result in the formation of fibrocartilage tissue, which is inferior to native articular cartilage. As a result, cartilage engineering strategies seek to repair or replace damaged cartilage with an engineered tissue that restores full functionality to the impaired joint. These strategies often involve the use of chondrocytes, yet in vitro expansion and culture can lead to undesirable changes in chondrocyte phenotype. This review focuses on the use of articular chondrocytes and mesenchymal stem cells (MSCs) in either monoculture or coculture for the enhancement of chondrogenesis. Coculture strategies increasingly outperform their monoculture counterparts with regard to chondrogenesis and present unique opportunities to attain chondrocyte phenotype stability in vitro. Methods to prevent chondrocyte dedifferentiation and promote chondrocyte redifferentiation as well as to promote the chondrogenic differentiation of MSCs while preventing MSC hypertrophy are discussed.

Cartilage regeneration by chondrogenic induced adult stem cells in osteoarthritic sheep model

Objectives

In this study, Adipose stem cells (ADSC) and bone marrow stem cells (BMSC), multipotent adult cells with the potentials for cartilage regenerations were induced to chondrogenic lineage and used for cartilage regenerations in surgically induced osteoarthritis in sheep model.

Methods

Osteoarthritis was induced at the right knee of sheep by complete resection of the anterior cruciate ligament and medial meniscus following a 3-weeks exercise regimen. Stem cells from experimental sheep were culture expanded and induced to chondrogenic lineage. Test sheep received a single dose of 2×10⁷ autologous PKH26-labelled, chondrogenically induced ADSCs or BMSCs as 5 mls injection, while controls received 5 mls culture medium.

Results

The proliferation rate of ADSCs 34.4±1.6 hr was significantly higher than that of the BMSCs 48.8±5.3 hr (P = 0.008). Chondrogenic induced BMSCs had significantly higher expressions of chondrogenic specific genes (Collagen II, SOX9 and Aggrecan) compared to chondrogenic ADSCs (P = 0.031, 0.010 and 0.013). Grossly, the treated knee joints showed regenerated de novo cartilages within 6 weeks post-treatment. On the International Cartilage Repair Society grade scores, chondrogenically induced ADSCs and BMSCs groups had significantly lower scores than controls (P = 0.0001 and 0.0001). Fluorescence of the tracking dye (PKH26) in the injected cells showed that they had populated the damaged area of cartilage. Histological staining revealed loosely packed matrixes of de novo cartilages and immunostaining demonstrated the presence of cartilage specific proteins, Collagen II and SOX9.

Conclusion

Autologous chondrogenically induced ADSCs and BMSCs could be promising cell sources for cartilage regeneration in osteoarthritis.

Adipose-derived stromal cells for osteoarticular repair: trophic function versus stem cell activity

The identification of multipotent adipose-derived stromal cells (ASC) has raised hope that tissue regeneration approaches established with bone-marrow-derived stromal cells (BMSC) can be reproduced with a cell-type that is far more accessible in large quantities. Recent detailed comparisons, however, revealed subtle functional differences between ASC and BMSC, stressing the concept of a common mesenchymal progenitor existing in a perivascular niche across all tissues. Focussing on bone and cartilage repair, this review summarises recent in vitro and in vivo studies aiming towards tissue regeneration with ASC. Advantages of good accessibility, high yield and superior growth properties are counterbalanced by an inferiority of ASC to form ectopic bone and stimulate long-bone healing along with their less pronounced osteogenic and angiogenic gene expression signature. Hence, particular emphasis is placed on establishing whether stem cell activity of ASC is so far proven and relevant for successful osteochondral regeneration, or whether trophic activity may largely determine therapeutic outcome.

Osteogenesis from human induced pluripotent stem cells: an in vitro and in vivo comparison with mesenchymal stem cells

The purpose of this study was to examine the in vitro and in vivo osteogenic potential of human induced pluripotent stem cells (hiPSCs) against that of human bone marrow mesenchymal stem cells (hBMMSCs). Embryoid bodies (EBs), which were formed from undifferentiated hiPSCs, were dissociated into single cells and underwent osteogenic differentiation using the same medium as hBMMSCs for 14 days. Osteoinduced hiPSCs were implanted on the critical-size calvarial defects and long bone segmental defects in rats. The healing of defects was evaluated after 8 weeks and 12 weeks of implantation, respectively. Osteoinduced hiPSCs showed relatively lower and delayed in vitro expressions of the osteogenic marker COL1A1 and bone sialoprotein, as well as a weaker osteogenic differentiation through alkaline phosphatase staining and mineralization through Alizarin red staining compared with hBMMSCs. Calvarial defects treated with osteoinduced hiPSCs had comparable quality of new bone formation, including full restoration of bone width and robust formation of trabeculae, to those treated with hBMMSCs. Both osteoinduced hiPSCs and hBMMSCs persisted in regenerated bone after 8 weeks of implantation. In critical-size long bone segmental defects, osteoinduced hiPSC treatment also led to healing of segmental defects comparable to osteoinduced hBMMSC treatment after 12 weeks. In conclusion, despite delayed in vitro osteogenesis, hiPSCs have an in vivo osteogenic potential as good as hBMMSCs.

c-Kit identifies a subpopulation of mesenchymal stem cells in adipose tissue with higher telomerase expression and differentiation potential

The stromal vascular fraction (SVF) of adipose tissue is an easy to obtain source of adipose tissue-derived stem cells (ADSCs). We and others have achieved significant but suboptimal therapeutic effects with ADSCs in various settings, mainly due to low rates of differentiation into specific cell types and with the downside of undesired side effects as a consequence of the undifferentiated ADSCs. These data prompted us to find new stem cell-specific markers for ADSCs and/or subpopulations with higher differentiation potential to specific lineages. We found a subpopulation of human ADSCs, marked by c-Kit positiveness, resides in a perivascular location, and shows higher proliferative activity and self-renewal capacity, higher telomerase activity and expression, higher in vitro adipogenic efficiency, a higher capacity for the maintenance of cardiac progenitors, and higher pancreatogenic and hepatogenic efficiency independently of CD105 expression. Our data suggests that the isolation of ADSC subpopulations with anti-c-Kit antibodies allows for the selection of a more homogeneous subpopulation with increased cardioprotective properties and increased adipogenic and endodermal differentiation potential, providing a useful tool for specific therapies in regenerative medicine applications.

Biopolymer/Calcium phosphate scaffolds for bone tissue engineering

With nearly 30 years of progress, tissue engineering has shown promise in developing solutions for tissue repair and regeneration. Scaffolds, together with cells and growth factors, are key components of this development. Recently, an increasing number of studies have reported on the design and fabrication of scaffolding materials. In particular, inspired by the nature of bone, polymer/ceramic composite scaffolds have been studied extensively. The purpose of this paper is to review the recent progress of the naturally derived biopolymers and the methods applied to generate biomimetic biopolymer/calcium phosphate composites as well as their biomedical applications in bone tissue engineering.

Porous membrane with reverse gradients of PDGF-BB and BMP-2 for tendon-to-bone repair: in vitro evaluation on adipose-derived stem cell differentiation

Polycaprolactone (PCL)/Pluronic F127 membrane with reverse gradients of dual platelet-derived growth factor-β (PDGF-BB) and bone morphogenetic protein 2 (BMP-2) concentrations was fabricated using a diffusion method to investigate the effect of reverse gradients of dual growth factor concentrations on adipose-derived stem cell (ASC) differentiations, such as tenogenesis and osteogenesis. The PDGF-BB and BMP-2 were continuously released from the membrane for up to 35 days, with reversely increasing/decreasing growth factors along the membrane length. Human ASCs were seeded on the membrane with reverse PDGF-BB and BMP-2 gradients. The cells were confluent after 1 week of culture, regardless of growth factor types or concentrations on the membrane. Gene expression (real-time polymerase chain reaction), Western blot and immunohistological analyses after 1 and 2 weeks of ASC culture showed that the membrane sections with higher PDGF-BB and lower BMP-2 concentrations provided a better environment for ASC tenogenesis, while the membrane sections with higher BMP-2 and lower PDGF-BB concentrations were better for promoting osteogenesis. The results suggest that the membrane with reverse gradients of PDGF-BB and BMP-2 may be promising for tendon-to-bone repair, as most essential biological processes are mediated by gradients of biological molecules in the body.

Chondrogenic differentiation and three dimensional chondrogenesis of human adipose-derived stem cells induced by engineered cartilage-derived conditional media

Due to lack of optimal inductive protocols, how to effectively improve chondrogenesis of adiposederived stem cells (ASCs) is still a great challenge. Our previous studies demonstrated that the culture media derived from chondrocyte-scaffold constructs (conditional media) contained various soluble chondrogenic factors and were effective for directing chondrogenic differentiation of bone marrow stem cells. Nevertheless, it remains unclear whether the conditional media can induce ASCs towards chondrogenic differentiation, especially for three-dimensional (3D) cartilage formation in a preshaped scaffold. In this study, it demonstrated that the conditional media derived from chondrocyte-scaffold constructs could promote ASCs to differentiate into chondrocyte-like cells, with similar expression of type II collagen to those induced by chondrogenic growth factors. Moreover, the expression level of chondrocyte-specific genes, such as SOX9, type II collagen, and COMP, was even higher in conditional medium group (CM) than that in optimized chondrogenic growth factor group (GF), indicating that the conditional media can serve as an effective inducer for chondrogenic differentiation of ASCs. Most importantly, the conditional media could also induce ASC-scaffold constructs to form 3D cartilage-like tissue with typical lacunae structures and positive expression of cartilage specific matrices, even higher contents of GAG and type II collagen were achieved in CM group compared to GF group. The current study establishes a simple, but stable, efficient, and economical method for directing 3D cartilage formation of ASCs, a strategy that may be more closely applicable for repairing cartilage defects.

Adipose tissue-derived mesenchymal stem cells: isolation, expansion, and characterization

Over the last decade, cell therapy has emerged as a potentially new approach for the treatment of cardiovascular diseases. Among the wide range of cell types and sources, adipose-derived mesenchymal stem cells have shown promise, mainly due to its plasticity and remarkable paracrine-secretion capacity, largely demonstrated at the in vitro and in vivo levels. Furthermore, its accessibility and abundance, the low morbidity of the surgical procedure, its easy isolation, culture, and long-term passaging capacity added to its immunomodulatory properties that could allow its allogeneic transplantation, making it one of the most attractive candidates for clinical application. In this chapter, we will focus on the methodology for the isolation, expansion, phenotypical characterization, differentiation, and storage of the adipose-derived stem cells.

Osteogenically differentiated mesenchymal stem cells and ceramics for bone tissue engineering

INTRODUCTION

In the human body, cells having self-renewal and multi-differentiation capabilities reside in many tissues and are called adult stem cells. In bone marrow tissue, two types of stem cells are well known: hematopoietic stem cells and mesenchymal stem cells (MSCs). Though the number of MSCs in bone marrow tissue is very low, it can be increased by in vitro culture of the marrow, and culture-expanded MSCs are available for various tissue regeneration.

AREAS COVERED

The culture-expanded MSCs can further differentiate into osteogenic cells such as bone forming osteoblasts by culturing the MSCs in an osteogenic medium. This paper discusses osteogenically differentiated MSCs derived from the bone marrow of patients. Importantly, the differentiation can be achieved on ceramic surfaces which demonstrate mineralized bone matrix formation as well as appearance of osteogenic cells. The cell/matrix/ceramic constructs could show immediate in vivo bone formation and are available for bone reconstruction surgery.

EXPERT OPINION

Currently, MSCs are clinically available for the regeneration of various tissues due to their high proliferation/differentiation capabilities. However, the capabilities are still limited and thus technologies to improve or recover the inherent capabilities of MSCs are needed.

Adipose- and bone marrow-derived mesenchymal stem cells display different osteogenic differentiation patterns in 3D bioactive glass-based scaffolds

Mesenchymal stem cells can be isolated from a variety of different sources, each having their own peculiar merits and drawbacks. Although a number of studies have been conducted comparing these stem cells for their osteo-differentiation ability, these are mostly done in culture plastics. We have selected stem cells from either adipose tissue (ADSCs) or bone marrow (BMSCs) and studied their differentiation ability in highly porous three-dimensional (3D) 45S5 Bioglass®-based scaffolds. Equal numbers of cells were seeded onto 5 × 5 × 4 mm³ scaffolds and cultured in vitro, with or without osteo-induction medium. After 2 and 4 weeks, the cell-scaffold constructs were analysed for cell number, cell spreading, viability, alkaline phosphatase activity and osteogenic gene expression. The scaffolds with ADSCs displayed osteo-differentiation even without osteo-induction medium; however, with osteo-induction medium osteogenic differentiation was further increased. In contrast, the scaffolds with BMSCs showed no osteo-differentiation without osteo-induction medium; after application of osteo-induction medium, osteo-differentiation was confirmed, although lower than in scaffolds with ADSCs. In general, stem cells in 3D bioactive glass scaffolds differentiated better than cells in culture plastics with respect to their ALP content and osteogenic gene expression. In summary, 45S5 Bioglass-based scaffolds seeded with ADSCs are well-suited for possible bone tissue-engineering applications. Induction of osteogenic differentiation appears unnecessary prior to implantation in this specific setting. Copyright © 2013 John Wiley & Sons, Ltd.

Osteogenic potentials of osteophytes in the cervical spine compared with patient matched bone marrow stromal cells

BACKGROUND

Osteophytes that form adjacent to degenerated disc have osteogeic potential. Studies suggest that their formation is associated with mesenchymal precursors arising from the chondrosynovial junction. This study is aimed to determine the cellular aging and osteogenic differentiation potential of osteophyte-derived mesenchymal cells (oMSCs) when compared to patient-matched bone marrow stromal cells (bMSCs).

MATERIALS AND METHODS

oMSCs and bMSCs were isolated from tissue samples during anterior cervical discectomy and fusion surgery. Extensive expansion of cell cultures was performed and early and late passage cells (P4 and P9, respectively) were used to study cell senescence and telomerase activity. Furthermore, osteogenic differentiation was applied to detect their osteogenic capacity.

RESULTS

The proliferation capacity of oMSCs in culture was superior to that of bMSCs and these cells readily underwent osteogenic differentiation. Our results showed that oMSCs had higher telomerase activity in late passages compared with bMSCs, although there was no significant difference in the telomerase activity in the early passages in either cell types. The telomerase activity was detectable only in early passage oMSCs and not in bMSCs.

CONCLUSIONS

Our results indicate that oMSCs retain a level of telomerase activity in vitro, which may account for the relatively greater longevity of these cells, compared to bMSCs. Furthermore, when compared to bMSCs, oMSCs maintained a higher proliferative capacity and the same osteogenic capacity, which may offer new insights of tissue formation.

Comparison of Effects of Mechanical Stretching on Osteogenic Potential of ASCs and BMSCs

Mechanical forces play critical roles in the development and remodeling processes of bone. As an alternative cell source for bone engineering, adipose-derived stem cells (ASCs) should be fully investigated for their responses to mechanical stress. Similarly, the osteogenic potential, stimulated by mechanical stress, should be compared with bone marrow stromal cells (BMSCs), which have been clinically used for bone tissue engineering. In this study, ASCs and BMSCs were osteogenic-induced for 48 hours, and then subjected to uniaxial mechanical stretching for 2 or 6 hours. Cell orientation, osteogenic regulatory genes, osteogenic genes and ALP activities were measured and compared between ASCs and BMSCs. ASCs could align in a perpendicular way to the direction of stretching stress, while BMSCs did not present a specific alignment. Both 2 and 6 hours mechanical stretching could enhance the mRNA expression of Osx and Runx2 in BMSCs and ASCs, while OCN mRNA only increased in ASCs after 6 hours mechanical loading. Mechanical stretching enhanced the BMP-2 mRNA expression in ASCs, while only after 6 hours of mechanical loading significantly increased the BMP-2 gene expression in BMSCs. Significant differences only exist between ASCs and BMSCs loaded at 2 hours of mechanical stretching. It is concluded that ASCs are more rapid responders to mechanical stress, and have greater potential than BMSCs in osteogenesis when stimulated by mechanical stretching, indicating their usefulness for bone study in a rat model.

Mesenchymal stem cells: new aspect in cell-based regenerative therapy

MSCs are multipotent progenitors which reside in bone marrow. They support hematopoietic stem cells homing, self renewal and differentiation in bone marrow. They can also differentiate into osteoblasts, adipocytes, chondrocytes, myocyates and many other tissues. In vivo, when trauma happens, MSCs operate cell renewal and migrate to the damaged tissues to regenerate that injury. In vitro, MSCs are able to proliferate and differentiate to a variety of cell lineages. This makes them a very hopeful tool for cell-based regenerative therapy for large bone defects, maxillofacial skeletal reconstruction, cardiovascular and spinal cord injury and so many other defects. The most important characteristic that make MSCs an excellent tool for cell replacement is their ability to escape from immune rejection. For therapeutic purposes they usually isolated from human bone marrow or fat and they should proliferate in order to reach an adequate number for implantation. Conventionally DMEM medium supplemented with 10% FBS is used for their expansion, but currently autologous platelet rich products are replaced FBS. Platelet granules contain so many growth factors that can support MSCs proliferation.

Adipose tissue-derived stem cells show considerable promise for regenerative medicine applications

The stromal-vascular cell fraction (SVF) of adipose tissue can be an abundant source of both multipotent and pluripotent stem cells, known as adipose-derived stem cells or adipose tissue-derived stromal cells (ADSCs). The SVF also contains vascular cells, targeted progenitor cells, and preadipocytes. Stromal cells isolated from adipose tissue express common surface antigens, show the ability to adhere to plastic, and produce forms that resemble fibroblasts. They are characterized by a high proliferation potential and the ability to differentiate into cells of meso-, ecto- and endodermal origin. Although stem cells obtained from an adult organism have smaller capabilities for differentiation in comparison to embryonic and induced pluripotent stem cells (iPSs), the cost of obtaining them is significantly lower. The 40 years of research that mainly focused on the potential of bone marrow stem cells (BMSCs) revealed a number of negative factors: the painful sampling procedure, frequent complications, and small cell yield. The number of stem cells in adipose tissue is relatively large, and obtaining them is less invasive. Sampling through simple procedures such as liposuction performed under local anesthesia is less painful, ensuring patient comfort. The isolated cells are easily grown in culture, and they retain their properties over many passages. That is why adipose tissue has recently been treated as an attractive alternative source of stem cells. Essential aspects of ADSC biology and their use in regenerative medicine will be analyzed in this article.