The changes of stemness biomarkers expression in human adipose-derived stem cells during long-term manipulation

Macromolecular crowding in animal component-free, xeno-free and foetal bovine serum media for human bone marrow mesenchymal stromal cell expansion and differentiation

Background: Cell culture media containing undefined animal-derived components and prolonged in vitro culture periods in the absence of native extracellular matrix result in phenotypic drift of human bone marrow stromal cells (hBMSCs). Methods: Herein, we assessed whether animal component-free (ACF) or xeno-free (XF) media formulations maintain hBMSC phenotypic characteristics more effectively than foetal bovine serum (FBS)-based media. In addition, we assessed whether tissue-specific extracellular matrix, induced via macromolecular crowding (MMC) during expansion and/or differentiation, can more tightly control hBMSC fate. Results: Cells expanded in animal component-free media showed overall the highest phenotype maintenance, as judged by cluster of differentiation expression analysis. Contrary to FBS media, ACF and XF media increased cellularity over time in culture, as measured by total DNA concentration. While MMC with Ficoll™ increased collagen deposition of cells in FBS media, FBS media induced significantly lower collagen synthesis and/or deposition than the ACF and XF media. Cells expanded in FBS media showed higher adipogenic differentiation than ACF and XF media, which was augmented by MMC with Ficoll™ during expansion. Similarly, Ficoll™ crowding also increased chondrogenic differentiation. Of note, donor-to-donor variability was observed for collagen type I deposition and trilineage differentiation capacity of hBMSCs. Conclusion: Collectively, our data indicate that appropriate screening of donors, media and supplements, in this case MMC agent, should be conducted for the development of clinically relevant hBMSC medicines.

Anti-Aging β-Klotho Gene-Activated Scaffold Promotes Rejuvenative Wound Healing Response in Human Adipose-Derived Stem Cells

Wound healing requires a tight orchestration of complex cellular events. Disruption in the cell-signaling events can severely impair healing. The application of biomaterial scaffolds has shown healing potential; however, the potential is insufficient for optimal wound maturation. This study explored the functional impact of a collagen-chondroitin sulfate scaffold functionalized with nanoparticles carrying an anti-aging gene β-Klotho on human adipose-derived stem cells (ADSCs) for rejuvenative healing applications. We studied the response in the ADSCs in three phases: (1) transcriptional activities of pluripotency factors (Oct-4, Nanog and Sox-2), proliferation marker (Ki-67), wound healing regulators (TGF-β3 and TGF-β1); (2) paracrine bioactivity of the secretome generated by the ADSCs; and (3) regeneration of basement membrane (fibronectin, laminin, and collagen IV proteins) and expression of scar-associated proteins (α-SMA and elastin proteins) towards maturation. Overall, we found that the β-Klotho gene-activated scaffold offers controlled activation of ADSCs' regenerative abilities. On day 3, the ADSCs on the gene-activated scaffold showed enhanced (2.5-fold) activation of transcription factor Oct-4 that was regulated transiently. This response was accompanied by a 3.6-fold increase in the expression of the anti-fibrotic gene TGF-β3. Through paracrine signaling, the ADSCs-laden gene-activated scaffold also controlled human endothelial angiogenesis and pro-fibrotic response in dermal fibroblasts. Towards maturation, the ADSCs-laden gene-activated scaffold further showed an enhanced regeneration of the basement membrane through increases in laminin (2.1-fold) and collagen IV (8.8-fold) deposition. The ADSCs also expressed 2-fold lower amounts of the scar-associated α-SMA protein with improved qualitative elastin matrix deposition. Collectively, we determined that the β-Klotho gene-activated scaffold possesses tremendous potential for wound healing and could advance stem cell-based therapy for rejuvenative healing applications.

Comparison of the Characteristics of Breast Milk-derived Stem Cells with the Stem Cells Derived from the Other Sources: A Comparative Review

Breast milk (BrM) not only supplies nutrition, but it also contains a diverse population of cells. It has been estimated that up to 6% of the cells in human milk possess the characteristics of mesenchymal stem cells (MSC). Available data also indicate that these cells are multipotent and capable of self-renewal and differentiation with other cells. In this review, we have compared different characteristics, such as CD markers, differentiation capacity, and morphology of stem cells, derived from human breast milk (hBr-MSC) with human bone marrow (hBMSC), Wharton's jelly (WJMSC), and human adipose tissue (hADMSC). Through the literature review, it was revealed that human breast milk-derived stem cells specifically express a group of cell surface markers, including CD14, CD31, CD45, and CD86. Importantly, a group of markers, CD13, CD29, CD44, CD105, CD106, CD146, and CD166, were identified, which were common in the four sources of stem cells. WJMSC, hBMSC, hADMSC, and hBr-MSC are potently able to differentiate into the mesoderm, ectoderm, and endoderm cell lineages. The ability of hBr-MSCs todifferentiate into the neural stem cells, neurons, adipocyte, hepatocyte, chondrocyte, osteocyte, and cardiomyocytes has made these cells a promising source of stem cells in regenerative medicine, while isolation of stem cells from the commonly used sources, such as bone marrow, requires invasive procedures. Although autologous breast milk-derived stem cells are an accessible source for women who are in the lactation period, breast milk can be considered as a source of stem cells with high differentiation potential without any ethical concern.

Adipose-derived stromal cells in regulation of hematopoiesis

Over the past decade, mesenchymal stromal cells (MSCs) found in the bone marrow microenvironment have been considered to be important candidates in cellular therapy. However, the application of MSCs in clinical settings is limited by the difficulty and low efficiency associated with the separation of MSCs from the bone marrow. Therefore, distinct sources of MSCs have been extensively explored. Adipose-derived stromal cells (ASCs), a cell line similar to MSCs, have been identified as a promising source. ASCs have become increasingly popular in many fields, as they can be conveniently extracted from fat tissue. This review focuses on the properties of ASCs in hematopoietic regulation and the underlying mechanisms, as well as the current applications and future perspectives in ASC-based therapy.

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.

Comparison of the proteome patterns of adipose-derived stem cells with those treated with selegiline using a two dimensional gel electrophoresis analysis

Adipose derived stem cells (ADSCs) are multipotent and can transdifferentiate into neural stem cells. We investigated the transdifferentiation of ADSCs to neural phenotype (NP) cells using selegiline and two-dimensional electrophoresis (2-DE). The perinephric and inguinal fat of rats was collected and used to isolate ADSCs that were characterized by immunophenotyping using flow cytometry. The ADSCs were differentiated into osteogenic and lipogenic cells. The NP cells were generated using 10^-9 mM selegiline and characterized by immunocytochemical staining of nestin and neurofilament 68 (NF-68), and by qRT-PCR of nestin, neurod1 and NF68. Total protein of ADSCs and NP cells was extracted and their proteome patterns were examined using 2-DE. ADSCs carried CD73, CD44 and CD90 cell markers, but not CD34. ADSCs were differentiated into osteocyte and adipocyte lineages. The differentiated NP cells expressed nestin, neuro d1 and NF-68. The proteome pattern of ADSCs was compared with that of NP cells and eight spots showed more than a two fold increase in protein expression. The molecular weights and isoelectric points of these highly expressed proteins were estimated using Melanie software. We compared these results with those of the mouse proteomic database using the protein isoelectric point database, and the functions of the eight proteins in differentiation of NP cells were predicted using the UniProt database. The probable identities of the proteins that showed higher expression in NP cells included cholinesterase, GFRa2, protein kinase C (PKC-eta) and RING finger protein 121. The sequences of the proteins identified from mouse database were aligned by comparing them with similar proteins in rat database using the Basic Local Alignment Search Tool (BLAST). The E values of all aligned proteins were zero, which indicates consistency of the matched protein. These proteins participate in differentiation of the neuron and their overexpression causes ADSCs transdifferentiation into NP cells.

In vitro enhancement and functional characterization of neurite outgrowth by undifferentiated adipose-derived stem cells

Adipose‑derived stem cells (ASCs) can easily be obtained and expanded in vitro for use in autologous cell therapy. Via their production of cytokines and neurotrophic factors, transplanted ASCs provide neuroprotection, neovascularization and induction of axonal sprouting. However, the influencing mechanism of undifferentiated ASCs on nerve regeneration is currently only partially understood. In the present study, undifferentiated ASCs and cutaneous primary afferent dorsal root ganglion (DRG) neurons were co‑cultured in order to investigate their interaction. ASCs were isolated from adult rat fat tissue. The presence of characteristic stem cell markers was determined by flow cytometry in three subsequent passages. Adipogenic, osteogenic, chondrogenic and glial differentiation was performed in order to evaluate their differentiation capacity. A direct co‑culture system with DRG cells was established to determine the effect of undifferentiated pluripotent ASCs on neurite elongation. Neurite outgrowth, length and number was examined in the co‑culture and compared with single‑culture cells and cells stimulated with nerve growth factor (NGF). In ASC cultures, NGF expression was assessed by ELISA. The present results demonstrated that the specific mesenchymal stem cell surface markers CD44, CD73 and CD90 were detected in all three subsequent passages of the isolated ASCs. In accordance, ASC differentiation into adipogenic, osteogenic, chondrogenic and Schwann cell phenotype was conducted successfully. Neurite outgrowth of DRG neurons was enhanced following co‑culture with ASCs, resulting in increased neurite length after 24 h of cultivation. Furthermore, neurite outgrowth of DRG neurons was directed towards the undifferentiated ASC and direct cell‑to‑cell contact was observed. In summary, the results of the present study revealed an interaction between the two cell types with guidance of neurite growth towards the undifferentiated ASC. These findings suggest that the use of undifferentiated ASC optimizing tissue‑engineered constructs may be promising for peripheral nerve repair.

Immunophenotyping and transcriptional profiling of in vitro cultured human adipose tissue derived stem cells

Adipose-derived stem cells (ASCs) have become an important research model in regenerative medicine. However, there are controversies regarding the impact of prolonged cell culture on the ASCs phenotype and their differentiation potential. Hence, we studied 10 clinical ASCs replicates from plastic and oncological surgery patients, in six-passage FBS supplemented cultures. We quantified basic mesenchymal cell surface marker transcripts and the encoded proteins after each passage. In parallel, we investigated the differentiation potential of ASCs into chondrocytes, osteocytes and adipocytes. We further determined the effects of FBS supplementation and subsequent deprivation on the whole transcriptome by comprehensive mRNA and miRNA sequencing. Our results show that ASCs maintain differentiation potential and consistent profile of key mesenchymal markers, with apparent expression of distinct isoforms, in long-term cultures. No significant differences were observed between plastic and oncological surgery cohorts. ASCs in FBS supplemented primary cultures are almost committed to mesenchymal lineages as they express key epithelial-mesenchymal transition genes including early mesenchymal markers. Furthermore, combined mRNA/miRNA expression profiling strongly supports a modulatory role for the miR-30 family in the commitment process to mesenchymal lineages. Finally, we propose improvements to existing qPCR based assays that address alternative isoform expression of mesenchymal markers.

Osteogenesis for postoperative temporal bone defects using human ear adipose-derived stromal cells and tissue engineering: An animal model study

Mastoidectomy, the removal of infected mastoid bones, is a common surgical procedure for the treatment of chronic otitis media. Persistent and recurrent otorrhea and accumulation of keratin debris following open cavity mastoidectomy are still bothersome issues for both patients and otologists. In this study, we used human ear adipose-derived stromal cells (hEASCs) in combination with polycaprolactone (PCL) scaffolds and osteogenic differentiation medium (ODM) to regenerate temporal bone defects. The hEASCs showed stem cell phenotypes, and these characteristics were maintained up to passage 5. Mastoid bulla and cranial bone defects were induced in Sprague-Dawley rats using AgNO₃ and burr hole drilling, respectively, and the rats were then divided into five groups: (1) control, (2) hEASCs, (3) hEASCs + ODM, (4) hEASCs + PCL scaffolds, and (5) hEASCs + PCL scaffolds + ODM. Osteogenesis was evaluated by micro-computed tomography and histology. Compared with the control group, the groups transplanted with hEASCs and PCL scaffolds had significantly higher bone formation along the periphery of the mastoid bulla area. Moreover, ODM synergistically enhanced bone formation in mastoid bulla defects. Our results suggest that combining hEASCs with PCL scaffolds represents a promising method for anatomical and functional reconstruction of postoperative temporal bone defects following mastoidectomy. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3493-3501, 2017.

Effect of hypoxia on human adipose-derived mesenchymal stem cells and its potential clinical applications

Human adipose-derived mesenchymal stem cells (hASCs) are an ideal cell source for regenerative medicine due to their capabilities of multipotency and the readily accessibility of adipose tissue. They have been found residing in a relatively low oxygen tension microenvironment in the body, but the physiological condition has been overlooked in most studies. In light of the escalating need for culturing hASCs under their physiological condition, this review summarizes the most recent advances in the hypoxia effect on hASCs. We first highlight the advantages of using hASCs in regenerative medicine and discuss the influence of hypoxia on the phenotype and functionality of hASCs in terms of viability, stemness, proliferation, differentiation, soluble factor secretion, and biosafety. We provide a glimpse of the possible cellular mechanism that involved under hypoxia and discuss the potential clinical applications. We then highlight the existing challenges and discuss the future perspective on the use of hypoxic-treated hASCs.

Decellularized adipose tissue microcarriers as a dynamic culture platform for human adipose-derived stem/stromal cell expansion

With the goal of designing a clinically-relevant expansion strategy for human adipose-derived stem/stromal cells (ASCs), methods were developed to synthesize porous microcarriers derived purely from human decellularized adipose tissue (DAT). An electrospraying approach was applied to generate spherical DAT microcarriers with an average diameter of 428 ± 41 μm, which were soft, compliant, and stable in long-term culture without chemical crosslinking. Human ASCs demonstrated enhanced proliferation on the DAT microcarriers relative to commercially-sourced Cultispher-S microcarriers within a spinner culture system over 1 month. ASC immunophenotype was maintained post expansion, with a trend for reduced expression of the cell adhesion receptors CD73, CD105, and CD29 under dynamic conditions. Upregulation of the early lineage-specific genes PPARγ, LPL, and COMP was observed in the ASCs expanded on the DAT microcarriers, but the cells retained their multilineage differentiation capacity. Comparison of adipogenic and osteogenic differentiation in 2-D cultures prepared with ASCs pre-expanded on the DAT microcarriers or Cultispher-S microcarriers revealed similar adipogenic and enhanced osteogenic marker expression in the DAT microcarrier group, which had undergone a higher population fold change. Further, histological staining results suggested a more homogeneous differentiation response in the ASCs expanded on the DAT microcarriers as compared to either Cultispher-S microcarriers or tissue culture polystyrene. A pilot chondrogenesis study revealed higher levels of chondrogenic gene and protein expression in the ASCs expanded on the DAT microcarriers relative to all other groups, including the baseline controls. Overall, this study demonstrates the promise of applying dynamic culture with tissue-specific DAT microcarriers as a means of deriving regenerative cell populations.

Cryopreservation of Human Mesenchymal Stem Cells for Clinical Applications: Current Methods and Challenges

Mesenchymal stem cells (MSCs) hold many advantages over embryonic stem cells (ESCs) and other somatic cells in clinical applications. MSCs are multipotent cells with strong immunosuppressive properties. They can be harvested from various locations in the human body (e.g., bone marrow and adipose tissues). Cryopreservation represents an efficient method for the preservation and pooling of MSCs, to obtain the cell counts required for clinical applications, such as cell-based therapies and regenerative medicine. Upon cryopreservation, it is important to preserve MSCs functional properties including immunomodulatory properties and multilineage differentiation ability. Further, a biosafety evaluation of cryopreserved MSCs is essential prior to their clinical applications. However, the existing cryopreservation methods for MSCs are associated with notable limitations, leading to a need for new or improved methods to be established for a more efficient application of cryopreserved MSCs in stem cell-based therapies. We review the important parameters for cryopreservation of MSCs and the existing cryopreservation methods for MSCs. Further, we also discuss the challenges to be addressed in order to preserve MSCs effectively for clinical applications.

Spontaneous and specific myogenic differentiation of human mesenchymal stem cells on polyethylene glycol-linked multi-walled carbon nanotube films for skeletal muscle engineering

This study explored the influence of polyethylene glycol-linked multi-walled carbon nanotube (PEG-CNT) films on skeletal myogenic differentiation of human mesenchymal stem cells (hMSCs). PEG-CNT films were prepared with nanoscale surface roughness, orderly arrangement of PEG-CNTs, high hydrophilicity and high mechanical strength. Notably, PEG-CNT films alone could direct the skeletal myogenic differentiation of hMSCs in the absence of myogenic induction factors. The quantitative real-time polymerase chain reaction (RT-PCR) showed that the non-induced hMSCs plated on the PEG-CNT films, compared to the negative control, presented significant up-regulation of general myogenic markers including early commitment markers of myoblast differentiation protein-1 (MyoD) and desmin, as well as a late phase marker of myosin heavy chain-2 (MHC). Corresponding protein analysis by immunoblot assays corroborated these results. Skeletal muscle-specific markers, fast skeletal troponin-C (TnC) and ryanodine receptor-1 (Ryr) were also significantly increased in the non-induced hMSCs on PEG-CNT films by RT-PCR. For these cells, the commitment to specific skeletal myoblasts was further proved by the absence of enhanced adipogenic, chondrogenic and osteogenic markers. This study elucidated that PEG-CNT films supported a dedicated differentiation of hMSCs into a skeletal myogenic lineage and can work as a promising material towards skeletal muscle injury repair.

Stem cells: a promising source for vascular regenerative medicine

The rising and diversity of many human vascular diseases pose urgent needs for the development of novel therapeutics. Stem cell therapy represents a challenge in the medicine of the twenty-first century, an area where tissue engineering and regenerative medicine gather to provide promising treatments for a wide variety of diseases. Indeed, with their extensive regeneration potential and functional multilineage differentiation capacity, stem cells are now highlighted as promising cell sources for regenerative medicine. Their multilineage differentiation involves environmental factors such as biochemical, extracellular matrix coating, oxygen tension, and mechanical forces. In this review, we will focus on human stem cell sources and their applications in vascular regeneration. We will also discuss the different strategies used for their differentiation into both mature and functional smooth muscle and endothelial cells.

Critical steps in the isolation and expansion of adipose-derived stem cells for translational therapy

Since the discovery of adipose-derived stem cells (ASCs), there have been high expectations of their putative clinical use. Recent advances support these expectations, and it is expected that the transition from pre-clinical and clinical studies to implementation as a standard treatment modality is imminent. However ASCs must be isolated and expanded according to good manufacturing practice guidelines and a basic assurance of quality, safety, and medical effectiveness is needed for authorisation by regulatory agencies, such as European Medicines Agency and US Food and Drug Administration. In this review, a collection of studies investigating the influence of different steps of the isolation and expansion protocol on the yield and functionality of ASCs has been presented in an attempt to come up with best recommendations that ensure potential beneficial clinical outcome of using ASCs in any therapeutic setting. If the findings confirm the initial observations of beneficial effects of ASCs, the path is paved for implementing these ASC-based therapies as standard treatment options.

Decreased contact inhibition in mouse adipose mesenchymal stem cells

The proliferation of embryonic cells or adult stem cells in tissue is critically regulated during development and repair. How limited the proliferation of cells, so far, is not much explored. Cell-cell contact proliferation inhibition is known as a crucial mechanism regulating cell proliferation in vitro and in vivo. In this study we examined the characters of mouse subcutaneous adipose derived stem cells (msADSC) whether they lost or get contact inhibition during in vitro culture. The characters of msADSC growth after confluence were analyzed using confocal microscope and the expression profiles of contact inhibition related genes were analyzed according to the morphological changes using real-time PCR method. msADSC showed overlapping growth between them but not after passage 14. The cell shapes were also changed after passage 14. The expression profiles of genes which are involved in contact inhibition were modified in the msADSC after passage 14. The differentiation ability of msADSCs to adipocyte, chondrocyte and osteocyte was not changed by such changes of gene expression profiles. Based on these results, it is revealed that smADSC were characterized by getting of strong cell-cell contact inhibition after passage 14 but the proliferation and developmental ability were not blocked by the change of cell-cell contact proliferation inhibition. These finding will help to understand the growth of adipose tissue, although further studies are needed to evaluate the physiological meaning of the cell-cell contact proliferation inhibition during in vitro culture of msADSC.

Phenotypic and functional characterization of long-term cryopreserved human adipose-derived stem cells

Cryopreservation represents an effective technique to maintain the functional properties of human adipose-derived stem cells (ASCs) and allows pooling of cells via long-term storage for clinical applications, e.g., cell-based therapies. It is crucial to reduce freezing injury during the cryopreservation process by loading the ASCs with the optimum concentration of suitable cryoprotective agents (CPAs). In this study, human ASCs were preserved for 3 months in different combinations of CPAs, including 1) 0.25 M trehalose; 2) 5% dimethylsulfoxide (DMSO); 3) 10% DMSO; 4) 5% DMSO + 20% fetal bovine serum (FBS); 5) 10% DMSO + 20% FBS; 6) 10% DMSO + 90% FBS. Interestingly, even with a reduction of DMSO to 5% and without FBS, cryopreserved ASCs maintained high cell viability comparable with standard cryomedium (10% DMSO + 90% FBS), with normal cell phenotype and proliferation rate. Cryopreserved ASCs also maintained their differentiation capability (e.g., to adipocytes, osteocytes and chondrocytes) and showed an enhanced expression level of stemness markers (e.g., NANOG, OCT-4, SOX-2 and REX-1). Our findings suggest that 5% DMSO without FBS may be an ideal CPA for an efficient long-term cryopreservation of human ASCs. These results aid in establishing standardized xeno-free long-term cryopreservation of human ASCs for clinical applications.

Human adipose-derived stromal/stem cells protect against STZ-induced hyperglycemia: analysis of hASC-derived paracrine effectors

Adipose-derived stromal/stem cells (ASCs) ameliorate hyperglycemia in rodent models of islet transplantation and autoimmune diabetes, yet the precise human ASC (hASC)-derived factors responsible for these effects remain largely unexplored. Here, we show that systemic administration of hASCs improved glucose tolerance, preserved β cell mass, and increased β cell proliferation in streptozotocin-treated nonobese diabetic/severe combined immunodeficient mice. Coculture experiments combining mouse or human islets with hASCs demonstrated that islet viability and function were improved by hASCs following prolonged culture or treatment with proinflammatory cytokines. Analysis of hASC-derived factors revealed vascular endothelial growth factor and tissue inhibitor of metalloproteinase 1 (TIMP-1) to be highly abundant factors secreted by hASCs. Notably, TIMP-1 secretion increased in the presence of islet stress from cytokine treatment, while TIMP-1 blockade was able to abrogate in vitro prosurvival effects of hASCs. Following systemic administration by tail vein injection, hASCs were detected in the pancreas and human TIMP-1 was increased in the serum of injected mice, while recombinant TIMP-1 increased viability in INS-1 cells treated with interleukin-1beta, interferon-gamma, and tumor necrosis factor alpha. In aggregate, our data support a model whereby factors secreted by hASCs, such as TIMP-1, are able to mitigate against β cell death in rodent and in vitro models of type 1 diabetes through a combination of local paracrine as well as systemic effects.

Proliferation and differentiation of human adipose-derived mesenchymal stem cells (ASCs) into osteoblastic lineage are passage dependent

OBJECTIVE

The effect of in vitro expansion of human adipose-derived stem cells (ASCs) on stem cell properties is controversial. We examined serial subcultivation with expansion on the ability of ASCs to grow and differentiate into osteoblastic lineages.

DESIGN

Flow cytometric analysis, growth kinetics, cell population doubling time, light microscopy and confocal analysis, and osteogenesis induction were performed to assess growth and osteogenic potential of subcultivated ASCs at passages 2 (P2), P4 and P6.

RESULTS

Flow cytometric analysis revealed that ASCs at P2 express classical mesenchymal stem cell markers including CD44, CD73, and CD105, but not CD14, CD19, CD34, CD45, or HLA-DR. Calcium deposition and alkaline phosphatase activity were the highest at P2 but completely abrogated at P4. Increased passage number impaired cell growth; P2 cultures exhibited exponential growth, while cells at P4 and P6 showed near linear growth with cell population doubling times increased from 3.2 at P2 to 4.8 d at P6. Morphologically, cells in various subcultivation stages showed flattened shape at low density but spindle-like structures at confluency as judged by phalloidin staining.

CONCLUSIONS

Osteogenic potential of ASCs is impaired by successive passaging and may not serve as a useful clinical source of osteogenic ASCs past P2.

Impact of low oxygen tension on stemness, proliferation and differentiation potential of human adipose-derived stem cells

Adipose-derived stem cells (ASCs) have been found adapted to a specific niche with low oxygen tension (hypoxia) in the body. As an important component of this niche, oxygen tension has been known to play a critical role in the maintenance of stem cell characteristics. However, the effect of O2 tension on their functional properties has not been well determined. In this study, we investigated the effects of O2 tension on ASCs stemness, differentiation and proliferation ability. Human ASCs were cultured under normoxia (21% O2) and hypoxia (2% O2). We found that hypoxia increased ASC stemness marker expression and proliferation rate without altering their morphology and surface markers. Low oxygen tension further enhances the chondrogenic differentiation ability, but reduces both adipogenic and osteogenic differentiation potential. These results might be correlated with the increased expression of HIF-1α under hypoxia. Taken together, we suggest that growing ASCs under 2% O2 tension may be important in expanding ASCs effectively while maintaining their functional properties for clinical therapy, particularly for the treatment of cartilage defects.

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.

Biomaterial strategies for stem cell maintenance during in vitro expansion

Stem cells, having the potential for self-renewal and multilineage differentiation, are the building blocks for tissue/organ regeneration. Stem cells can be isolated from various sources but are, in general, available in too small numbers to be used directly for clinical purpose without intermediate expansion procedures in vitro. Although this in vitro expansion of undifferentiated stem cells is necessary, stem cells typically diminish their ability to self-renew and proliferate during passaging. Consequently, maintaining the stemness of stem cells has been recognized as a major challenge in stem cell-based research. This review focuses on the latest developments in maintaining the self-renewal ability of stem cells during in vitro expansion by biomaterial strategies. Further, this review highlights what should be the focus for future studies using stem cells for regenerative applications.

Retropatellar fat pad-derived stem cells from older osteoarthritic patients have lesser differentiation capacity and expression of stemness genes

BACKGROUND AIMS

The use of retropatellar fat pad-derived mesenchymal stromal cells (RFMSCs) for cell-based therapy, particularly for cartilage repair, has been reported by several investigators in recent years. However, the effects of the donor's age and medical condition on the characteristics of RFMSCs have not been well established. The aim of this study was to determine whether age and medical condition can reduce the multipotential of stem cells isolated from the retropatellar fat pad.

METHODS

The RFMSCs were isolated from patients with osteoarthritic knee cartilage (degenerative group; 40-60 years old) and compared with patients without degenerative knee disease (young group; <40 years old) in terms of their growth kinetics, immunophenotype, differentiation ability and stemness gene expression.

RESULTS

Data showed that RFMSCs from both groups have similar growth kinetics and immunophenotype profile at passage 3. However, RFMSCs from the degenerative group showed lower adipogenic, osteogenic and chondrogenic differentiation ability compared with RFMSCs derived from the young group. The stemness gene expression level of RFMSCs derived from the degenerative group was lower than that in the young group. RFMSCs from both groups met the minimum criteria of mesenchymal stromal cells and have the potential for cartilage regeneration. However, RFMSCs from the degenerative group showed lower regeneration capability.

CONCLUSIONS

These results indicate that older age and osteoarthritic condition did affect the multipotential of stem cells derived from the retropatellar fat pad under the current prescribed condition. More studies will be conducted to clarify whether the age or medical condition contributed more to the loss of differentiation capacity and stemness gene expression of RFMSCs.

Differentiation potential and profile of nuclear receptor expression during expanded culture of human adipose tissue-derived stem cells reveals PPARγ as an important regulator of Oct4 expression

Potential therapeutic use of human adipose tissue-derived stem cells (hADSCs) requires the production of large cell numbers by in vitro expansion. However, long-term in vitro culture is associated with reduced stem cell characteristics and differentiation capability. We investigated the proliferation rate and expression of p16(INK4a) mRNA, surface stem cell markers, and stem cell transcription factors. The proliferation rate decreased significantly as passages increased, and the expression of p16(INK4a) mRNA significantly increased. FACS analysis of CD73, CD90, and CD105 expression showed no significant difference among examined passages; however, the mRNA expression levels of pluripotent markers, Oct4 and Nanog, were significantly decreased at higher passages. At passages 12 and 20, there was decreased differentiation capability into insulin-producing cells, evidenced by significantly decreased expression of insulin and related β cell markers. Adipogenic and osteogenic differentiation was also decreased at higher passages. We then analyzed the transcriptional expression profiles of 48 nuclear receptors at four different passages. We found that the expression of peroxisome proliferator-activated receptor γ (PPARγ) and thyroid hormone receptor TRβ was significantly decreased at higher passages. Treatment with PPARγ activators or overexpression of PPARγ in hADSCs at passage 20 could recover Oct4 expression levels and increase Oct4 promoter activity. PPARγ inactivation by GW9662 inhibited the troglitazone-induced Oct4 mRNA expression. Furthermore, PPARγ overexpression in hADSC at passage 20 improved the differentiation potential to insulin-producing cells. In conclusion, we demonstrated that hADSCs undergo characteristic changes and reduction of differentiation capability during expanded culture in vitro, and revealed the role of PPARγ as one potential factor in the regulation of Oct4 expression during in vitro aging of hADSCs.

Effects of continuous passaging on mineralization of MC3T3-E1 cells with improved osteogenic culture protocol

The murine-derived MC3T3-E1 cell line provided by the American Type Culture Collection (ATCC) is a well-known osteogenic cell culture model system to test materials in vitro. However, the effect of passaging on its mineralization capacity has never been described and their culture supplements can be further optimized. Therefore, we evaluated the influence of the passage number and different osteogenic culture supplements, including ascorbic acid (AsAP) and dexamethasone (Dex) on the osteogenic capacity of MC3T3-E1 cells. This capacity was measured by the deposited calcium, the alkaline phosphatase activity, and the expression of osteogenic-related genes, including bone sialoprotein (BSP), osteocalcin (OC), and osteopontin (OPN). The results indicated that the mineralization capacity of MC3T3-E1 cells significantly decreased during passaging and got exhausted at passage 34, as assessed by measuring calcium deposition after 28 days of osteogenic induction. Moreover, the combination of AsAP and Dex triggered significantly more mineralization in MC3T3-E1 cells than the ATCC recommended addition of AsAP alone, as indicated by increased calcium deposition and higher expression of BSP and OPN. However, Dex alone could not trigger this effect, but only in combination with the AsAP, which indicates that Dex has no direct effect on mineralization. In conclusion, the passage number of MC3T3-E1 cells is of great importance and the use of cells above 30 passages should be avoided. In addition, the favored osteogenic supplements providing an improved osteogenic differentiation of MC3T3-E1 cells are the combination of AsAP and Dex.

Effects of serum reduction and VEGF supplementation on angiogenic potential of human adipose stromal cells in vitro

OBJECTIVES

This study investigated effects of reduced serum condition and vascular endothelial growth factor (VEGF) on angiogenic potential of adipose stromal cells (ASCs) in vitro.

MATERIALS AND METHODS

Adipose stromal cells were cultured in three different types of medium: (i) F12/DMEM (FD) supplemented with 10% FBS from passage 0 (P0) to P6; (ii) FD supplemented with 2% FBS at P6; and (iii) FD supplemented with 2% FBS plus 50 ng/ml of VEGF at P6. Morphological changes and growth rate of ASCs were recorded. Changes in stemness, angiogenic and endogenic genes' expressions were analysed using Real-Time PCR.

RESULTS

Adipose stromal cells changed from fibroblast-like shape when cultured in 10% FBS medium to polygonal when cultured in 2% FBS plus VEGF-supplemented medium. Their growth rate was lower in 2% FBS medium, but increased with addition of VEGF. Real-Time PCR showed that ASCs maintained most of their stemness and angiogenic genes' expression in 10% FBS at P1, P5 and P6, but this increased significantly in 2% FBS at P6. Endogenic genes expression such as PECAM-1, VE chaderin and VEGFR-2 decreased after serial passage in 10% FBS, but increased significantly at P6 in 2% FBS. Addition of VEGF did not cause any significant change in gene expression level.

CONCLUSION

Adipose stromal cells had greater angiogenic potential when cultured in reduced serum conditions. VEGF did not enhance their angiogenic potential in 2% FBS-supplemented medium.

Unravelling the retention of proliferation and differentiation potency in extensive culture of human subcutaneous fat-derived mesenchymal stem cells in different media

OBJECTIVES

This study has intended to investigate longevity of subcutaneous fat-derived mesenchymal stem cells (SF-MSCs) under extensive culturing. It has also focused on optimization of culture media for them over prolonged periods in vitro.

MATERIALS AND METHODS

We evaluated SF-MSCs with reference to phenotypic characterization, proliferative ability, karyotype stability and differentiation potency with early (P3) and late passage (P20) conditions, using four different media, DMEM-LG, ALPHA-MEM, DMEM-F12 and DMEM-KO.

RESULTS

This study unravels retention of SF-MSC characteristics in facets of phenotypic expression profile (CD 90, CD 105, CD 73, CD 34, CD 29, CD 54, CD 49d, CD 117, HLA-DR, CD 166, CD 31, CD 44), proliferative characteristics, karyotyping and differentiation potency prolonged culturing to P25 in all media. Population doubling time (PDT) in Alpha MEM, DMEM LG, DMEM F 12, DMEM KO were identified to be (1.81, 1.84, 1.9, 2.08 days) at early passage and (2.93, 2.94, 3.12, 3.06 days) at late passage. As a corollary, Alpha MEM and DMEM LG serve as appropriate basal media for SF-MSC when proliferative potency is considered.

CONCLUSIONS

In research, it is imperative that SF-MSC uphold their expansion potency in the aforesaid attributes in all media over extensive culturing, thereby transforming their colossal in vitro potency, with the aim of curing a wide horizon of diseases.

5-Azacytidine is insufficient for cardiogenesis in human adipose-derived stem cells

BACKGROUND

Adipose tissue is a source of multipotent adult stem cells and it has the ability to differentiate into several types of cell lineages such as neuron cells, osteogenic cells and adipogenic cells. Several reports have shown adipose-derived stem cells (ASCs) have the ability to undergo cardiomyogenesis. Studies have shown 5-azacytidine can successfully drive stem cells such as bone marrow derived stem cells to differentiate into cardiomyogenic cells. Therefore, in this study, we investigated the effect 5-azacytidine on the cardiogenic ability of ASCs.

METHODS

The cardiogenic potential of ASCs was analysed by studying the morphological changes after induction, the changes in the cardiogenic genes expression i.e. GATA4, MLC-2v, MLC-2a, NKX2.5, β-MHC, α-MHC, Atrial natriuretic peptide (ANP), Connexin 43, Cardiac Troponin C, Cardiac Troponin I and myocyte enhancer factor (MEF2C) and the changes of embryonic stem cells genes expression at P5 and P10 using quantitative PCR.

RESULTS

Our results showed that the induced ASCs did not show significant morphological difference compared to the non-induced ASCs. While quantitative PCR data indicated that most cardiogenic genes and stemness genes expression level decreased after induction at P5 and P10.

CONCLUSION

5-azacytidine is insufficient for the cardiogenic induction of the ASCs.

Brief review of models of ectopic bone formation

Ectopic bone formation is a unique biologic entity--distinct from other areas of skeletal biology. Animal research models of ectopic bone formation most often employ rodent models and have unique advantages over orthotopic (bone) environments, including a relative lack of bone cytokine stimulation and cell-to-cell interaction with endogenous (host) bone-forming cells. This allows for relatively controlled in vivo experimental bone formation. A wide variety of ectopic locations have been used for experimentation, including subcutaneous, intramuscular, and kidney capsule transplantation. The method, benefits and detractions of each method are summarized in the following review. Briefly, subcutaneous implantation is the simplest method. However, the most pertinent concern is the relative paucity of bone formation in comparison to other models. Intramuscular implantation is also widely used and relatively simple, however intramuscular implants are exposed to skeletal muscle satellite progenitor cells. Thus, distinguishing host from donor osteogenesis becomes challenging without cell-tracking studies. The kidney capsule (perirenal or renal capsule) method is less widely used and more technically challenging. It allows for supraphysiologic blood and nutrient resource, promoting robust bone growth. In summary, ectopic bone models are extremely useful in the evaluation of bone-forming stem cells, new osteoinductive biomaterials, and growth factors; an appropriate choice of model, however, will greatly increase experimental success.

Porcine uterus contains a population of mesenchymal stem cells

The uterus has a remarkable ability of cycling remodeling throughout the reproductive life of the female. Recent findings in the human and mouse indicate that adult stem/progenitor cells may play a prominent role in the maintenance of uterine endometrial and myometrial homeostasis. We aimed to characterize the prospective stem/progenitor cells in the porcine uterus and establish a new model for uterine stem cell research. In this study, we demonstrated that cells isolated from porcine uterus have capacity for in vitro differentiation into adipogenic and osteogenic lineages and express the mesenchymal stem cell (MSC) markers CD29, CD44, CD144, CD105, and CD140b as revealed by RT-PCR. Moreover, we showed that some cells isolated from the porcine uterus when cultured at low density produce large clones with an efficiency of 0.035%. Simultaneously, they were negative for hematopoietic stem cell markers such as CD34 and CD45. Low expression of nestin, which is specific for neural stem cells and various progenitor cells, was also detected. We conclude that the porcine uterus contains a small population of undifferentiated cells with MSC-like properties similar to human and mouse uteri.