Increasing Passage Number Research Articles

Reduced matrix metalloproteinase and collagen transcription mediated by the TGF-β/Smad pathway in passaged normal human dermal fibroblasts.

Transforming growth factor-β (TGF-β) is a major regulator of extracellular matrix (ECM) events, particularly collagen production. We explored whether the expression of matrix metalloproteinases (MMPs) and collagen are transcriptionally regulated by the TGF-β and Smad signaling pathways, and the roles played by NF-κB and mitogen-activated protein kinase (MAPK) signaling in normal, aged, human dermal fibroblasts. We quantified mRNA and protein expression using real-time PCR and immunoblotting of proteins from cells in passage 5-15. The levels of mRNAs encoding TGF-β1, TGF-β3, and TGF-β receptor type I (TGFβ RI) decreased with increasing passage number. The levels of mRNAs encoding TGF-β2, TGFβ RII, and TGFβ RIII increased to passage 10 but decreased by passage 15. The levels of mRNAs encoding Smad-2, -3, -4, and -7 decreased with increasing passage number. The level of mRNA encoding MMP-1 increased with increasing passage number, and the levels of mRNAs encoding MMP-2, TIMP-1, and TIMP-2 increased to passage 10 but decreased by passage 15. The levels of mRNAs encoding collagen types I and II decreased with increasing passage number. At the protein level, NF-κB, IκBα, p38, ERK, Akt, and JNK became increasingly phosphorylated at higher passage numbers. Our results suggest that reductions in the expression levels of MMPs and collagen types I and III in aging human dermal fibroblasts reflect reduced expression of TGF-β/Smad and TGF-β receptors, thus compromising the TGF-β receptor-binding capacity of fibroblasts; the NF-κB and Akt-JNK/MAPK signaling pathways may play active roles in this process.

Chromosomal Heterogeneity of the G-401 Rhabdoid Tumor Cell Line: Unusual Partial 7p Trisomy.

Rhabdoid tumor is a very aggressive and hardly curable pediatric malignancy. It commonly starts in the kidneys but also can occur in the brain, liver, and other organs. The treatment of this tumor usually involves a combination of surgery, radiation, and chemotherapy. Because this tumor is rare, there is still limited experience with a defined standard of care. Cytogenetic analysis is an important routine method to monitor chromosomal aberrations. We have analyzed metaphases of the G-401 rhabdoid tumor cell line. In these cells we have observed metaphases with derivative chromosome 12 arising from partial trisomy 7p. With increasing passage number the numbers of metaphases having this derivative chromosome 12 were found to be higher. In passage number 2 only one metaphase had this pathological chromosome 12. By passage number 10 and passage number 15 about 25 and 95% of this derivative chromosome 12 were found, respectively. We were able to subclone G-401 cells by limiting dilutions and successfully separated cells having apparently normal karyotypes from cells having derivative chromosome 12. Using the cell proliferation assay we showed that clones possessing the derivative chromosome 12 grew more rapidly than clones with normal chromosomes. The cell cycle analysis confirmed this observation. Overall, in this study we describe for the first time a 7p triplication in a rare rhabdoid tumor of kidney. Both types of clones described in this study could be used as a preclinical model to study the involvement of partial chromosome 7 alterations in the development of rhabdoid tumors.

Serial Systemic Candida albicans Infection Highlighted by Proteomics.

Candida albicans is the major pathogen isolated from nosocomial bloodstream infections, leading to higher mortality rates. Thus, due to its clinical relevance, studies aiming to understand host–pathogen interactions in C. albicans infection are necessary. Therefore, we performed proteomic analysis using a murine model of serial systemic infection by C. albicans to evaluate possible changes in the protein profile of the pathogen over time. Firstly, we observed a reduction in the median survival time of infected animals with increasing passage number, suggesting a higher pathogenicity acquired during repeated infections. By LC-MS/MS, it was possible to obtain protein profiles from the wild-type strain (WT) and compare them to proteins extracted from Candida cells recovered from infected tissues during passages one, three, and four (P1, P3, and P4). We obtained 56, 29, and 97 proteins in P1, P3, P4, respectively, all varying in abundance. Regarding biological processes, the majority of proteins were related to carbohydrate metabolism, stress responses and amino acid metabolism. The proteins were also categorized according to their potential role in virulence traits, such as biofilm production, yeast-to-hyphae transition, phenotypic switching, proteins related to stress responses, and uncharacterized proteins. Therefore, serial infection in combination with proteomic approach enabled us to deepen the existing knowledge about host-pathogen interactions.

Characterization of EIAV env Quasispecies during Long-Term Passage In Vitro: Gradual Loss of Pathogenicity.

As the only widely used live lentiviral vaccine, the equine infectious anima virus (EIAV) attenuated vaccine was developed by in vitro passaging of a virulent strain for 121 generations. In our previous study, we observed that the attenuated vaccine was gradually selected under increased environmental pressure at the population level (termed a quasispecies). To further elucidate the potential correlation between viral quasispecies evolution and pathogenesis, a systematic study was performed by sequencing env using several methods. Some key mutations were identified within Env, and we observed that increased percentages of these mutations were accompanied by an increased passage number and attenuated virulence. Phylogenetic analysis revealed that env mutations related to the loss of virulence might have occurred evolutionarily. Among these mutations, deletion of amino acid 236 in the V4 region of Env resulted in the loss of one N-glycosylation site that was crucial for virulence. Notably, the 236-deleted sequence represented a “vaccine-specific” mutation that was also found in wild EIAVLN40 strains based on single genome amplification (SGA) analysis. Therefore, our results suggest that the EIAV attenuated vaccine may originate from a branch of quasispecies of EIAVLN40. Generally, the presented results may increase our understanding of the attenuation mechanism of the EIAV vaccine and provide more information about the evolution of other lentiviruses.

High throughput screening reveals no significant changes in protein synthesis, processing, and degradation machinery during passaging of mesenchymal stem cells 1.

Increasing reports of successful and safe application of bone marrow derived mesenchymal stem cells (BM-MSCs) for cell therapy are pouring in from numerous studies. However poor survival of transplanted cells in the recipient has impaired the benefits of BM-MSCs based therapies. Therefore cell product preparation procedures pertaining to MSC therapy need to be optimized to improve the survival of transplanted cells. One of the important ex vivo procedures in the preparation of cells for therapy is passaging of BM-MSCs to ensure a suitable number of cells for transplantation, which may affect the turnover of proteins involved in regulation of cell survival and (or) death pathways. In the current study, we investigated the effect of an increase in passage number of BM-MSCs in cell culture on the intracellular protein turnover (protein synthesis, processing, and degradation machinery). We performed proteomic analysis of BM-MSCs at different passages. There was no significant difference observed in the ribosomal, protein processing, and proteasomal pathways related proteins in BM-MSCs with an increase in passage number from P3 to P7. Therefore, expansion of MSCs in the cell culture in clinically relevant passages (Passage 3-7) does not affect the quality of MSCs in terms of intracellular protein synthesis and turnover.

Prolonging culture of primary human keratinocytes isolated from suction blisters with the Rho kinase inhibitor Y-27632.

Keratinocytes are the most abundant cell type in the epidermis. They prevent desiccation and provide immunological and barrier defense against potential pathogens such as Staphylococcus aureus and Candida albicans. The study of this first line of immune defense may be hindered by invasive isolation methods and/or improper culture conditions to support stem cell maintenance and other potential mechanisms contributing to long-term subcultivation in vitro. Primary keratinocytes have been successfully isolated from blister roofs induced by negative pressure, which separates the epidermis from the dermis in vivo in human subjects. This method allows collection of pure epidermal cells without dermal contamination in a minimally invasive manner. However, the isolated keratinocytes differentiate and senesce when cultured in vitro beyond five passages. Here, we present evidence that the Rho kinase (ROCK) inhibitor Y-27632 can be used to effectively increase the proliferative capabilities of keratinocytes isolated using the suction blister method, similar to what has been previously reported for primary keratinocytes isolated using alternative methods. We show that the increase in passage number is directly correlated to delayed differentiation, and that cells passaged long term with the inhibitor retain their ability to stratify in organotypic raft cultures and respond to cytokine treatment; additionally, the late passage cells have a heterogeneous mix of differentiated and non-differentiated cells which may be predicted by a ratio of select differentiation markers. The described method presents a minimally invasive procedure for keratinocyte isolation and prolonged culture that allows analysis of keratinocyte function in both healthy volunteers and patients with dermatologic diseases.

Effect of Environmental Parameters on Glycosylation of Recombinant Immunoglobulin G Produced from Recombinant CHO Cells

Site specific glycosylation of immunoglobulin G (IgG) occurs at Asn297 in the Fc region. The heterogeneous ensemble of glycoform occurs due to the degree of terminal galactosylation and sialylation, and these differences in glycosylation affect both the pharmacokinetic behavior and effector functions of the IgG, such as complementdependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC). In this study, the differential glycosylation of IgG was compared and environmental physical and chemical parameters were evaluated in an attempt to promote glycosylation of recombinant antibodies, thereby creating more humanized glycoform antibodies and increasing their in vivo efficacy as therapeutic drugs. It was shown that cells at late stationary growth phase in batch cultures, cells with increased passage number, and the culture conditions of lowered temperature and pH promoted galactosylation and sialylation of antibodies. Galactose, fructose and mannose were found to elicit galactosylation and sialylation when they were used alone as a substitute of glucose. Mannose showed synergistic effects on glycosylation when used with other sugars, such as glucose and galactose. However when fructose was used with other sugars, the degree of galactosylation mechanism appeared to be decreased. These results support understandings of the glycosylation mechanisms in glycoprotein, particularly recombinant antibodies for therapeutics.

Stability of gene expression by primary bronchial epithelial cells over increasing passage number

BackgroundAn increasing number of studies using primary human bronchial epithelial cells (BECs) have reported intrinsic differences in the expression of several genes between cells from asthmatic and non-asthmatic donors. The stability of gene expression by primary BECs with increasing cell passage number has not been well characterized.MethodsTo determine if expression by primary BECs from asthmatic and non-asthmatic children of selected genes associated with airway remodeling, innate immune response, immunomodulatory factors, and markers of differentiated airway epithelium, are stable over increasing cell passage number, we studied gene expression patterns in passages 1, 2, 3, 4, and 5 BECs from asthmatic (n = 6) and healthy (n = 6) subjects that were differentiated at an air-liquid interface. RNA was harvested from BECs and RT-PCR was performed for TGFβ1, TGFβ2, activin A, FSTL3, MUC5AC, TSLP, IL-33, CXCL10, IFIH1, p63, KT5, TUBB4A, TJP1, OCLN, and FOXJ1.ResultsExpression of TGFβ1, TGFβ2, activin A, FSTL3, MUC5AC, CXCL10, IFIH1, p63, KT5, TUBB4A, TJP1, OCLN, and FOXJ1 by primary BECs from asthmatic and healthy children was stable with no significant differences between passages 1, 2 and 3; however, gene expression at cell passages 4 and 5 was significantly greater and more variable compared to passage 1 BECs for many of these genes. IL-33 and FOXJ1 expression was also stable between passages 1 through 3, however, expression at passages 4 and 5 was significantly lower than by passage 1 BECs. TSLP, p63, and KRT5 expression was stable across BEC passages 1 through 5 for both asthmatic and healthy BECs.ConclusionsThese observations illustrate the importance of using BECs from passage ≤3 when studying gene expression by asthmatic and non-asthmatic primary BECs and characterizing the expression pattern across increasing cell passage number for each new gene studied, as beyond passage 3 genes expressed by primary BECs appear to less accurately model in vivo airway epithelial gene expression.

Changes in phenotype and differentiation potential of human mesenchymal stem cells aging in vitro

BackgroundAdult mesenchymal stem cells (MSCs) hold great promise for regenerative medicine because of their self-renewal, multipotency, and trophic and immunosuppressive effects. Due to the rareness and high heterogeneity of freshly isolated MSCs, extensive in-vitro passage is required to expand their populations prior to clinical use; however, senescence usually accompanies and can potentially affect MSC characteristics and functionality. Therefore, a thorough characterization of the variations in phenotype and differentiation potential of in-vitro aging MSCs must be sought.MethodsHuman bone marrow-derived MSCs were passaged in vitro and cultivated with either DMEM-based or αMEM-based expansion media. Cells were prepared for subculture every 10 days up to passage 8 and were analyzed for cell morphology, proliferative capacity, and surface marker expression at the end of each passage. The gene expression profile and adipogenic and osteogenic differentiation capability of MSCs at early (passage 4) and late (passage 8) passages were also evaluated.ResultsIn-vitro aging MSCs gradually lost the typical fibroblast-like spindle shape, leading to elevated morphological abnormality and inhomogeneity. While the DMEM-based expansion medium better facilitated MSC proliferation in the early passages, the cell population doubling rate reduced over time in both DMEM and αMEM groups. CD146 expression decreased with increasing passage number only when MSCs were cultured under the DMEM-based condition. Senescence also resulted in MSCs with genetic instability, which was further regulated by the medium recipe. Regardless of the expansion condition, MSCs at both passages 4 and 8 could differentiate into adipocyte-like cells whereas osteogenesis of aged MSCs was significantly compromised. For osteogenic induction, use of the αMEM-based expansion medium yielded longer osteogenesis and better quality.ConclusionsHuman MSCs subjected to extensive in-vitro passage can undergo morphological, phenotypic, and genetic changes. These properties are also modulated by the medium composition employed to expand the cell populations. In addition, adipogenic potential may be better preserved over osteogenesis in aged MSCs, suggesting that MSCs at early passages must be used for osteogenic differentiation. The current study presents valuable information for future basic science research and clinical applications leading to the development of novel MSC-based therapeutic strategies for different diseases.

Early passaging of mesenchymal stem cells does not instigate significant modifications in their immunological behavior

BackgroundBone marrow-derived allogeneic mesenchymal stem cells (MSCs) from young healthy donors are immunoprivileged and their clinical application for regenerative medicine is under evaluation. However, data from preclinical and initial clinical trials indicate that allogeneic MSCs after transplantation provoke a host immune response and are rejected. In the current study, we evaluated the effect of an increase in passage number in cell culture on immunoprivilege of the MSCs. Since only limited numbers of MSCs can be sourced at a time from a donor, it is imperative to expand them in culture to meet the necessary numbers required for cell therapy. Presently, the most commonly used passages for transplantation include passages (P)3–7. Therefore, in this study we included clinically relevant passages, i.e., P3, P5, and P7, for evaluation.MethodsThe immunoprivilege of MSCs was assessed with the mixed leukocyte reaction assay, where rat MSCs were cocultured with peripheral blood leukocytes for 72 h. Leukocyte-mediated cytotoxicity, apoptosis (Bax/Bcl-xl ratio), leukocyte proliferation, and alterations in cellular bioenergetics in MSCs were assessed after the coculture. Furthermore, the expression of various oxidized phospholipids (oxidized phosphatidylcholine (ox-PC)) was analyzed in MSCs using a lipidomic platform. To determine if the ox-PCs were acting in tandem with downstream intracellular protein alterations, we performed proteome analysis using a liquid chromatography/mass spectrometry (LC/MS) proteomic platform.ResultsOur data demonstrate that MSCs were immunoprivileged at all three passages since coculture with leukocytes did not affect the survival of MSCs at P3, P5, and P7. We also found that, with an increase in the passage number of MSCs, leukocytes did not cause any significant effect on cellular bioenergetics (basal respiration rate, spare respiratory capacity, maximal respiration, and coupling efficiency). Interestingly, in our omics data, we detected alterations in some of the ox-PCs and proteins in MSCs at different passages; however, these changes were not significant enough to affect their immunoprivilege.ConclusionsThe outcome of this study demonstrates that an increase in passage number (from P3 to P7) in the cell culture does not have any significant effect on the immunoprivilege of MSCs.

MicroRNA‑32 silences WWP2 expression to maintain the pluripotency of human amniotic epithelial stem cells and β islet‑like cell differentiation.

Human amniotic epithelial stem cells (HuAECs) exhibit pluripotent characteristics, which are similar to those of embryonic stem cells, and can differentiate into various adult tissues and cells through directed induction. However, in culture, HuAECs tend to lose their pluripotency, and their directed differentiation capability declines with increasing passage number. The stem cell pluripotency factor octamer-binding protein 4 (Oct4) is an important transcription factor that promotes stem cell self-proliferation and maintains their pluripotency. Previous studies have demonstrated that WW domain containing E3 ubiquitin protein ligase 2 (WWP2) negatively regulates Oct4 expression and stem cell pluripotency. Therefore, the present study aimed to investigate the regulation of WWP2 by microRNAs (miRs), and to evaluate the expression of the downstream factor Oct4 and the maintenance of HuAEC pluripotency. Bioinformatics analysis identified a complementary binding site for miR-32 in the 3′untranslated region of the WWP2 gene, thus suggesting that it may be a target gene of miR-32. Post-infection of HuAECs with a vector overexpressing miR-32, the endogenous expression of WWP2 was significantly decreased, whereas Oct4 expression was significantly increased. Furthermore, miR-32-infected cells differentiated into β islet-like cells by directed induction. The results indicated that after induction, HuAECs overexpressing miR-32 also overexpressed the biomarkers of β islet-like cells. In addition, the ability to secrete insulin was markedly enhanced in response to glucose stimulation, in cells overexpressing miR-32. In conclusion, the present study suggested that miR-32 may effectively inhibit WWP2 expression in HuAECs and promote Oct4 overexpression to maintain their pluripotency.

Phenotypic characteristics of feline adipose-derived stem cells affected by cell passage number.

In this study we evaluated the influence of passage number on the phenotypic characteristics of feline adipose-derived stem cells (ASCs) in order to develop a broader understanding of their dynamics. Feline ASCs were individually isolated from five domestic cats and subjected to proliferative culture at passage (P) 2, 6 and 10. The cells at each sub-passage were examined in regard to their phenotypic properties associated with multipotent mesenchymal stem cells (MSCs), such as morphology, proliferation kinetics, self-renewal, and expression of MSCs-specific surface markers. The differentiation capacity into adipocytes and osteoblasts was also identified. Feline ASCs appeared with a fibroblast-like morphology with minimal alteration through P10. The rate of cell proliferation gradually decreased, while cell doubling time gradually increased with each passage. A significant decrease in CFU-F efficiency was observed with increasing cell passage number. The ASC population uniformly expressed their characteristic markers CD44 and CD90, but did not express the hematopoietic marker CD45. However, MSC markers gradually decreased in the later passage stages. Feline ASCs were capable of undergoing both adipogenesis and osteogenesis at P2. These findings suggested that the phenotypic characteristics of feline ASCs could be affected by long-term passages, which is potentially very important in regard to their therapeutic application.

Amplification of the EGFR gene can be maintained and modulated by variation of EGF concentrations in in vitro models of glioblastoma multiforme.

Glioblastoma multiforme (GBM) is the most common and lethal brain tumor in adults. It is known that amplification of the epidermal growth factor receptor gene (EGFR) occurs in approximately 40% of GBM, leading to enhanced activation of the EGFR signaling pathway and promoting tumor growth. Although GBM mutations are stably maintained in GBM in vitro models, rapid loss of EGFR gene amplification is a common observation during cell culture. To maintain EGFR amplification in vitro, heterotopic GBM xenografts with elevated EGFR copy number were cultured under varying serum conditions and EGF concentrations. EGFR copy numbers were assessed over several passages by quantitative PCR and chromogenic in situ hybridization. As expected, in control assays with 10% FCS, cells lost EGFR amplification with increasing passage numbers. However, cells cultured under serum free conditions stably maintained elevated copy numbers. Furthermore, EGFR protein expression positively correlated with genomic amplification levels. Although elevated EGFR copy numbers could be maintained over several passages in vitro, levels of EGFR amplification were variable and dependent on the EGF concentration in the medium. In vitro cultures of GBM cells with elevated EGFR copy number and corresponding EGFR protein expression should prove valuable preclinical tools to gain a better understanding of EGFR driven glioblastoma and assist in the development of new improved therapies.

Uptake of magnetic nanoparticles for adipose-derived stem cells with multiple passage numbers

With the increasingly promising role of nanomaterials in tissue engineering and regenerative medicine, the interaction between stem cells and nanoparticles has become a critical focus. The entry of nanoparticles into cells has become a primary issue for effectively regulating the subsequent safety and performance of nanomaterials in vivo . Although the influence of nanomaterials on endocytosis has been extensively studied, reports on the influence of stem cells are rare. Moreover, the effect of nanomaterials on stem cells is also dependent upon the action mode. Unfortunately, the interaction between stem cells and assembled nanoparticles is often neglected. In this paper, we explore for the first time the uptake of γ-Fe2O3 nanoparticles by adipose-derived stem cells with different passage numbers. The results demonstrate that cellular viability decreases and cell senescence level increases with the extension of the passage number. We found the surface appearance of cellular membranes to become increasingly rough and uneven with increasing passage numbers. The iron content in the dissociative nanoparticles was also significantly reduced with increases in the passage number. However, we observed multiple-passaged stem cells cultured on assembled nanoparticles to have similarly low iron content levels. The mechanism may lie in the magnetic effect of γ-Fe2O3 nanoparticles resulting from the field-directed assembly. The results of this work will facilitate the understanding and translation of nanomaterials in the clinical application of stem cells.

Cryopreservation of canine cardiosphere-derived cells: Implications for clinical application.

The clinical application of cardiosphere-derived cells (CDCs) to treat cardiac disease has gained increasing interest over the past decade. Recent clinical trials confirm their regenerative capabilities, although much remains to be elucidated about their basic biology. To develop this new treatment modality, in a cost effective and standardized workflow, necessitates the creation of cryopreserved cell lines to facilitate access for cardiac patients requiring urgent therapy. Cryopreservation may however lead to alterations in cell behavior and potency. The aim of this study was to investigate the effect of cryopreservation on canine CDCs. CDCs and mesenchymal stem cells (MSCs) isolated from five dogs were characterized. CDCs demonstrated a population doubling time that was unchanged by cryopreservation (fresh vs. cryopreserved; 57.13 ± 5.27 h vs. 48.94 ± 9.55 h, P = 0.71). This was slower than for MSCs (30.46 h, P < 0.05). The ability to form clones, self-renew, and commit to multiple lineages was unaffected by cryopreservation. Cryopreserved CDCs formed larger cardiospheres compared to fresh cells (P < 0.0001). Fresh CDCs showed a high proportion of CD105+ (89.0% ± 4.98) and CD44+ (99.68% ± 0.13) cells with varying proportions of CD90+ (23.36% ± 9.78), CD34+ (7.18% ± 4.03) and c-Kit+ (13.17% ± 8.67) cells. CD45+ (0.015% ± 0.005) and CD29+ (2.92% ± 2.46) populations were negligible. Increasing passage number of fresh CDCs correlated with an increase in the proportion of CD34+ and a decrease in CD90+ cells (P = 0.003 and 0.03, respectively). Cryopreserved CDCs displayed increased CD34+ (P < 0.001) and decreased CD90+ cells (P = 0.042) when compared to fresh cells. Overall, our study shows that cryopreservation of canine CDCs is feasible without altering their stem characteristics, thereby facilitating their utilization for clinical trials. © 2017 International Society for Advancement of Cytometry.

A computational modelling framework to quantify the effects of passaging cell lines.

In vitro cell culture is routinely used to grow and supply a sufficiently large number of cells for various types of cell biology experiments. Previous experimental studies report that cell characteristics evolve as the passage number increases, and various cell lines can behave differently at high passage numbers. To provide insight into the putative mechanisms that might give rise to these differences, we perform in silico experiments using a random walk model to mimic the in vitro cell culture process. Our results show that it is possible for the average proliferation rate to either increase or decrease as the passaging process takes place, and this is due to a competition between the initial heterogeneity and the degree to which passaging damages the cells. We also simulate a suite of scratch assays with cells from near–homogeneous and heterogeneous cell lines, at both high and low passage numbers. Although it is common in the literature to report experimental results without disclosing the passage number, our results show that we obtain significantly different closure rates when performing in silico scratch assays using cells with different passage numbers. Therefore, we suggest that the passage number should always be reported to ensure that the experiment is as reproducible as possible. Furthermore, our modelling also suggests some avenues for further experimental examination that could be used to validate or refine our simulation results.

Cellular automata model for human articular chondrocytes migration, proliferation and cell death: An in vitro validation.

Articular cartilage is characterized by low cell density of only one cell type, chondrocytes, and has limited self-healing properties. When articular cartilage is affected by traumatic injuries, a therapeutic strategy such as autologous chondrocyte implantation is usually proposed for its treatment. This approach requires in vitro chondrocyte expansion to yield high cell number for cell transplantation. To improve the efficiency of this procedure, it is necessary to assess cell dynamics such as migration, proliferation and cell death during culture. Computational models such as cellular automata can be used to simulate cell dynamics in order to enhance the result of cell culture procedures. This methodology has been implemented for several cell types; however, an experimental validation is required for each one. For this reason, in this research a cellular automata model, based on random-walk theory, was devised in order to predict articular chondrocyte behavior in monolayer culture during cell expansion. Results demonstrated that the cellular automata model corresponded to cell dynamics and computed-accurate quantitative results. Moreover, it was possible to observe that cell dynamics depend on weighted probabilities derived from experimental data and cell behavior varies according to the cell culture period. Thus, depending on whether cells were just seeded or proliferated exponentially, culture time probabilities differed in percentages in the CA model. Furthermore, in the experimental assessment a decreased chondrocyte proliferation was observed along with increased passage number. This approach is expected to having other uses as in enhancing articular cartilage therapies based on tissue engineering and regenerative medicine.

Mesenchymal stromal cells derived from whole human umbilical cord exhibit similar properties to those derived from Wharton's jelly and bone marrow.

Mesenchymal stromal cells (MSC) can be isolated from several regions of human umbilical cords, including Wharton's jelly (WJ), artery, vein or cord lining. These MSC appear to be immune privileged and are promising candidates for cell therapy. However, isolating MSC from WJ, artery, vein or cord lining requires time‐consuming tissue dissection. MSC can be obtained easily via briefly digesting complete segments of the umbilical cord, likely containing heterogenous or mixed populations of MSC (MC‐MSC). MC‐MSC are generally less well characterized than WJ‐MSC, but nevertheless represent a potentially valuable population of MSC. This study aimed to further characterize MC‐MSC in comparison to WJ‐MSC and also the better‐characterized bone marrow‐derived MSC (BM‐MSC). MC‐MSC proliferated faster, with significantly faster doubling times reaching passage one 8.8 days sooner and surviving longer in culture than WJ‐MSC. All MSC retained the safety aspect of reducing telomere length with increasing passage number. MSC were also assessed for their ability to suppress T‐cell proliferation and for the production of key markers of pluripotency, embryonic stem cells, tolerogenicity (CD40, CD80, CD86 and HLA‐DR) and immunomodulation (indoleamine 2,3‐dioxygenase [IDO] and HLA‐G). The MC‐MSC population displayed all of the positive attributes of WJ‐MSC and BM‐MSC, but they were more efficient to obtain and underwent more population doublings than from WJ, suggesting that MC‐MSC are promising candidates for allogeneic cell therapy in regenerative medicine.

Adipose-derived stem cells undergo spontaneous osteogenic differentiation in vitro when passaged serially or seeded at low density

Adipose-derived stem cells (ADSCs) are a convenient source of cells for regenerating tissue. Widespread application of ADSCs requires that they propagate efficiently and differentiate in vitro. We investigated the differentiation potential of ADSCs during long-term expansion in vitro and when the cells were seeded at low density. ADSCs were isolated from the inguinal fat pads of 3-week-old male rats, then cultured serially for 12 passages; some ADSCs at passage 3 were seeded at low density. The differentiation potential of ADSCs from passage 3 to passage 12 was assessed by their capacity for adipogenesis and osteogenesis while cultured in specific induction media. Spontaneous osteogenesis of ADSCs at passage 12 and of ADSCs that were seeded at low density was detected by western blotting, alizarin red S staining and measurement of alkaline phosphatase (ALP) activity. We found that with increasing passage number, the adipogenic potential of ADSCs decreased and osteogenic differentiation increased. Alizarin red S staining, bone morphogenetic protein-2 (BMP-2) and runt-related transcription factor 2 (Runx2) expressions, and ALP activity demonstrated that both ADSCs at passage 12 and those that were seeded at low density differentiated into osteoblasts without additional induction factors.

The monolayer–spheres–monolayer cycle: Ultrastructural changes in stem cells

Stem cell sphere formation is applied as a preconditioning treatment prior to transplantation. Here, stem cells (SC) isolated from human subepicardial adipose tissue were analyzed at different stages of the monolayer–spheres–monolayer cycle by transmission electron microscopy. Spheres obtained on a non-adherent surface or through hanging drops gave similar results. At the first two or three passages (stage 1), isolated SC displayed an embryonal cell-like ultrastructure. With increased passage number (stage 2), SC became larger and more electron-dense with a multilobed nucleus, well-developed rough endoplasmic reticulum (RER), well-developed Golgi apparatus, and numerous vacuoles. At 2 h after sphere induction (stage 3), SC gathered into clusters and formed desmosome-like intercellular contacts. Their nuclei possessed a large loose fibrillo-granular nucleolus, the cytoplasm was tightly packed with disintegrated cisternae of RER, and Golgi apparatus was not identified. Twenty-four hours afterward (stage 4), SC in well-formed spheres exhibited a large dense nucleolus and poorly developed Golgi apparatus and RER. One day after sphere dissociation (stage 5), SC looked like embryonal cells and were morphologically similar to the cells of the first stage except for the presence of a large nucleolus and several Golgi complexes. At 48 h after sphere dissociation (stage 6), SC became electron-dense and resembled SC of the second stage, bearing irregular nuclei and cytoplasm that was rich in RER. We interpret these results as SC senescence with increasing passage number after isolation from the tissue or 1 day after sphere dissociation and rejuvenation of the SC just after sphere dissociation. Further research is needed to determine the genetic, biochemical, and physiological parameters of the SC corresponding to morphologically defined distinct stages in order to provide high quality cellular material for cell therapy.