Role of CD9 in proliferation and proangiogenic action of human adipose-derived mesenchymal stem cells

Unveiling heterogeneity in MSCs: exploring marker-based strategies for defining MSC subpopulations

Mesenchymal stem/stromal cells (MSCs) represent a heterogeneous cell population distributed throughout various tissues, demonstrating remarkable adaptability to microenvironmental cues and holding immense promise for disease treatment. However, the inherent diversity within MSCs often leads to variability in therapeutic outcomes, posing challenges for clinical applications. To address this heterogeneity, purification of MSC subpopulations through marker-based isolation has emerged as a promising approach to ensure consistent therapeutic efficacy. In this review, we discussed the reported markers of MSCs, encompassing those developed through candidate marker strategies and high-throughput approaches, with the aim of explore viable strategies for addressing the heterogeneity of MSCs and illuminate prospective research directions in this field.

The role of Tetraspanins in digestive system tumor development: update and emerging evidence

Digestive system malignancies, including cancers of the esophagus, pancreas, stomach, liver, and colorectum, are the leading causes of cancer-related deaths worldwide due to their high morbidity and poor prognosis. The lack of effective early diagnosis methods is a significant factor contributing to the poor prognosis for these malignancies. Tetraspanins (Tspans) are a superfamily of 4-transmembrane proteins (TM4SF), classified as low-molecular-weight glycoproteins, with 33 Tspan family members identified in humans to date. They interact with other membrane proteins or TM4SF members to form a functional platform on the cytoplasmic membrane called Tspan-enriched microdomain and serve multiple functions including cell adhesion, migration, propagation and signal transduction. In this review, we summarize the various roles of Tspans in the progression of digestive system tumors and the underlying molecular mechanisms in recent years. Generally, the expression of CD9, CD151, Tspan1, Tspan5, Tspan8, Tspan12, Tspan15, and Tspan31 are upregulated, facilitating the migration and invasion of digestive system cancer cells. Conversely, Tspan7, CD82, CD63, Tspan7, and Tspan9 are downregulated, suppressing digestive system tumor cell metastasis. Furthermore, the connection between Tspans and the metastasis of malignant bone tumors is reviewed. We also summarize the potential role of Tspans as novel immunotherapy targets and as an approach to overcome drug resistance. Finally, we discuss the potential clinical value and therapeutic targets of Tspans in the treatments of digestive system malignancies and provide some guidance for future research.

Extirpating the cancer stem cell hydra: Differentiation therapy and Hyperthermia therapy for targeting the cancer stem cell hierarchy

Ever since the discovery of cancer stem cells (CSCs), they have progressively attracted more attention as a therapeutic target. Like the mythical hydra, this subpopulation of cells seems to contribute to cancer immortality, spawning more cells each time that some components of the cancer cell hierarchy are destroyed. Traditional modalities focusing on cancer treatment have emphasized apoptosis as a route to eliminate the tumor burden. A major problem is that cancer cells are often in varying degrees of dedifferentiation contributing to what is known as the CSCs hierarchy and cells which are known to be resistant to conventional therapy. Differentiation therapy is an experimental therapeutic modality aimed at the conversion of malignant phenotype to a more benign one. Hyperthermia therapy (HT) is a modality exploiting the changes induced in cells by the application of heat produced to aid in cancer therapy. While differentiation therapy has been successfully employed in the treatment of acute myeloid leukemia, it has not been hugely successful for other cancer types. Mounting evidence suggests that hyperthermia therapy may greatly augment the effects of differentiation therapy while simultaneously overcoming many of the hard-to-treat facets of recurrent tumors. This review summarizes the progress made so far in integrating hyperthermia therapy with existing modules of differentiation therapy. The focus is on studies related to the successful application of both hyperthermia and differentiation therapy when used alone or in conjunction for hard-to-treat cancer cell niche with emphasis on combined approaches to target the CSCs hierarchy.

Construction of Metastasis-Specific Regulation Network in Ovarian Cancer Based on Prognostic Stemness-Related Signatures

WE aimed to reveal the correlation between ovarian cancer (OV) metastasis and cancer stemness in OV. RNA-seq data and clinical information of 591 OV samples (551 without metastasis and 40 with metastasis) were obtained from TCGA. The edgeR method was used to determine differentially expressed genes (DEGs) and transcription factors (DETFs). Then, mRNA expression-based stemness index was calculated using one-class logistic regression (OCLR). Weighted gene co-expression network analysis (WGCNA) was used to define stemness-related genes (SRGs). Univariate and multivariate Cox proportional hazard regression were conducted to identify the prognostic SRGs (PSRGs). PSRGs, DETFs, and 50 hallmark pathways quantified by gene set variation analysis (GSVA) were integrated into Pearson co-expression analysis. Significant co-expression interactions were utilized to construct an OV metastasis-specific regulation network. Cell communication analysis was carried out based on single cell RNA sequencing data to explore the molecular regulation mechanism of OV. Eventually, assay for targeting accessible-chromatin with high throughout sequencing (ATAC), chromatin immunoprecipitation sequencing (ChIP-seq) validation, and multiple data sets were used to validate the expression levels and prognostic values of key stemness-related signatures. Moreover, connectivity map (CMap) was used to identify potential inhibitors of stemness-related signatures. Based on edgeR, WGCNA, and Cox proportional hazard regression, 22 PSRGs were defined to construct a prognostic prediction model for metastatic OV. In the metastasis-specific regulation network, key TF-PSRS interaction pair was NR4A1-EGR3 (correlation coefficient = 0.81, p < 0.05, positive), and key PSRG-hallmark pathway interaction pair was EGR3-TNFα signaling via NFκB (correlation coefficient = 0.44, p < 0.05, positive), which were validated in multi-omics databases. Thioridazine was postulated to be the most significant compound in treatment of OV metastasis. PSRGs played critical roles in OV metastasis. Specifically, EGR3 was the most significant PSRG, which was positively regulated by DETF NR4A1, inducing metastasis via TNFα signaling.

Effect of Expansion Media on Functional Characteristics of Bone Marrow-Derived Mesenchymal Stromal Cells

The therapeutic efficacy of mesenchymal stromal cells (MSCs) has been shown to rely on their immunomodulatory and regenerative properties. In order to obtain sufficient numbers of cells for clinical applications, MSCs have to be expanded ex vivo. Expansion media with xenogeneic-free (XF) growth-promoting supplements like human platelet lysate (PL) or serum- and xenogeneic-free (SF/XF) formulations have been established as safe and efficient, and both groups provide different beneficial qualities. In this study, MSCs were expanded in XF or SF/XF media as well as in mixtures thereof. MSCs cultured in these media were analyzed for phenotypic and functional properties. MSC expansion was optimal with SF/XF conditions when PL was present. Metabolic patterns, consumption of growth factors, and secretome of MSCs differed depending on the type and concentration of supplement. The lactate per glucose yield increased along with a higher proportion of PL. Many factors in the supernatant of cultured MSCs showed distinct patterns depending on the supplement (e.g., FGF-2, TGFβ, and insulin only in PL-expanded MSC, and leptin, sCD40L PDGF-AA only in SF/XF-expanded MSC). This also resulted in changes in cell characteristics like migratory potential. These findings support current approaches where growth media may be utilized for priming MSCs for specific therapeutic applications.

A Simplified and Effective Approach for the Isolation of Small Pluripotent Stem Cells Derived from Human Peripheral Blood

Pluripotent stem cells are key players in regenerative medicine. Embryonic pluripotent stem cells, despite their significant advantages, are associated with limitations such as their inadequate availability and the ethical dilemmas in their isolation and clinical use. The discovery of very small embryonic-like (VSEL) stem cells addressed the aforementioned limitations, but their isolation technique remains a challenge due to their small cell size and their efficiency in isolation. Here, we report a simplified and effective approach for the isolation of small pluripotent stem cells derived from human peripheral blood. Our approach results in a high yield of small blood stem cell (SBSC) population, which expresses pluripotent embryonic markers (e.g., Nanog, SSEA-3) and the Yamanaka factors. Further, a fraction of SBSCs also co-express hematopoietic markers (e.g., CD45 and CD90) and/or mesenchymal markers (e.g., CD29, CD105 and PTH1R), suggesting a mixed stem cell population. Finally, quantitative proteomic profiling reveals that SBSCs contain various stem cell markers (CD9, ITGA6, MAPK1, MTHFD1, STAT3, HSPB1, HSPA4), and Transcription reg complex factors (e.g., STAT5B, PDLIM1, ANXA2, ATF6, CAMK1). In conclusion, we present a novel, simplified and effective isolating process that yields an abundant population of small-sized cells with characteristics of pluripotency from human peripheral blood.

Cryobanking European Mink (Mustela lutreola) Mesenchymal Stem Cells and Oocytes

The European mink (Mustela lutreola) is one of Europe’s most endangered species, and it is on the brink of extinction in the Iberian Peninsula. The species’ precarious situation requires the application of new ex situ conservation methodologies that complement the existing ex situ and in situ conservation measures. Here, we report for the first time the establishment of a biobank for European mink mesenchymal stem cells (emMSC) and oocytes from specimens found dead in the Iberian Peninsula, either free or in captivity. New emMSC lines were isolated from different tissues: bone marrow (emBM-MSC), oral mucosa (emOM-MSc), dermal skin (emDS-MSC), oviduct (emO-MSc), endometrium (emE-MSC), testicular (emT-MSC), and adipose tissue from two different adipose depots: subcutaneous (emSCA-MSC) and ovarian (emOA-MSC). All eight emMSC lines showed plastic adhesion, a detectable expression of characteristic markers of MSCs, and, when cultured under osteogenic and adipogenic conditions, differentiation capacity to these lineages. Additionally, we were able to keep 227 Cumulus-oocyte complexes (COCs) in the biobank, 97 of which are grade I or II. The European mink MSC and oocyte biobank will allow for the conservation of the species’ genetic variability, the application of assisted reproduction techniques, and the development of in vitro models for studying the molecular mechanisms of infectious diseases that threaten the species’ precarious situation.

Tracing colonic embryonic transcriptional profiles and their reactivation upon intestinal damage

We lack a holistic understanding of the genetic programs orchestrating embryonic colon morphogenesis and governing damage response in the adult. A window into these programs is the transcriptomes of the epithelial and mesenchymal cell populations in the colon. Performing unbiased single-cell transcriptomic analyses of the developing mouse colon at different embryonic stages (embryonic day 14.5 [E14.5], E15.5, and E18.5), we capture cellular and molecular profiles of the stages before, during, and after the appearance of crypt structures, as well as in a model of adult colitis. The data suggest most adult lineages are established by E18.5. We find embryonic-specific gene expression profiles and cell populations that reappear in response to tissue damage. Comparison of the datasets from mice and human colitis suggests the processes are conserved. In this study, we provide a comprehensive single-cell atlas of the developing mouse colon and evidence for the reactivation of embryonic genes in disease.

Cellular Heterogeneity in Adipose Tissues

Adipose tissue depots in distinct anatomical locations mediate key aspects of metabolism, including energy storage, nutrient release, and thermogenesis. Although adipocytes make up more than 90% of adipose tissue volume, they represent less than 50% of its cellular content. Here, I review recent advances in genetic lineage tracing and transcriptomics that reveal the identities of the heterogeneous cell populations constituting mouse and human adipose tissues. In addition to mature adipocytes and their progenitors, these include endothelial and various immune cell types that together orchestrate adipose tissue development and functions. One salient finding is the identification of progenitor subtypes that can modulate adipogenic capacity through paracrine mechanisms. Another is the description of fate trajectories of monocyte/macrophages, which can respond maladaptively to nutritional and thermogenic stimuli, leading to metabolic disease. These studies have generated an extraordinary source of publicly available data that can be leveraged to explore commonalities and differences among experimental models, providing new insights into adipose tissues and their role in metabolic disease.

Human Adipose-Derived Stem Cells in Madelung's Disease: Morphological and Functional Characterization

Madelung Disease (MD) is a syndrome characterized by the accumulation of aberrant symmetric adipose tissue deposits. The etiology of this disease is yet to be elucidated, even though the presence of comorbidities, either genetic or environmental, has been reported. For this reason, establishing an in vitro model for MD is considered crucial to get insights into its physiopathology. We previously established a protocol for isolation and culture of stem cells from diseased tissues. Therefore, we isolated human adipose-derived stem cells (ASC) from MD patients and compared these cells with those isolated from healthy subjects in terms of surface phenotype, growth kinetic, adipogenic differentiation potential, and molecular alterations. Moreover, we evaluated the ability of the MD-ASC secretome to affect healthy ASC. The results reported a difference in the growth kinetic and surface markers of MD-ASC compared to healthy ASC but not in adipogenic differentiation. The most commonly described mitochondrial mutations were not observed. Still, MD-ASC secretome was able to shift the healthy ASC phenotype to an MD phenotype. This work provides evidence of the possibility of exploiting a patient-based in vitro model for better understanding MD pathophysiology, possibly favoring the development of novel target therapies.

Alveolar soft-part sarcoma (ASPS) resembles a mesenchymal stromal progenitor: evidence from meta-analysis of transcriptomic data

Alveolar soft-part sarcoma (ASPS) is an extremely rare malignancy characterized by the unbalanced translocation der(17)t(X;17)(p11;q25). This translocation generates a fusion protein, ASPL-TFE3, that drives pathogenesis through aberrant transcriptional activity. Although considerable progress has been made in identifying ASPS therapeutic vulnerabilities (e.g., MET inhibitors), basic research efforts are hampered by the lack of appropriate in vitro reagents with which to study the disease. In this report, previously unmined microarray data for the ASPS cell line, ASPS-1, was analyzed relative to the NCI sarcoma cell line panel. These data were combined with meta-analysis of pre-existing ASPS patient microarray and RNA-seq data to derive a platform-independent ASPS transcriptome. Results demonstrated that ASPS-1, in the context of the NCI sarcoma cell panel, had some similarities to normal mesenchymal cells and connective tissue sarcomas. The cell line was characterized by high relative expression of transcripts such as CRYAB, MT1G, GCSAML, and SV2B. Notably, ASPS-1 lacked mRNA expression of myogenesis-related factors MYF5, MYF6, MYOD1, MYOG, PAX3, and PAX7. Furthermore, ASPS-1 had a predicted mRNA surfaceome resembling an undifferentiated mesenchymal stromal cell through expression of GPNMB, CD9 (TSPAN29), CD26 (DPP4), CD49C (ITGA3), CD54 (ICAM1), CD63 (TSPAN30), CD68 (SCARD1), CD130 (IL6ST), CD146 (MCAM), CD147 (BSG), CD151 (SFA-1), CD166 (ALCAM), CD222 (IGF2R), CD230 (PRP), CD236 (GPC), CD243 (ABCB1), and CD325 (CDHN). Subsequent re-analysis of ASPS patient data generated a consensus expression profile with considerable overlap between studies. In common with ASPS-1, elevated expression was noted for CTSK, DPP4, GPNMB, INHBE, LOXL4, PSG9, SLC20A1, STS, SULT1C2, SV2B, and UPP1. Transcripts over-expressed only in ASPS patient samples included ABCB5, CYP17A1, HIF1A, MDK, P4HB, PRL, and PSAP. These observations are consistent with that expected for a mesenchymal progenitor cell with adipogenic, osteogenic, or chondrogenic potential. In summary, the consensus data generated in this study highlight the unique and highly conserved nature of the ASPS transcriptome. Although the ability of the ASPL-TFE3 fusion to perturb mRNA expression must be acknowledged, the prevailing ASPS transcriptome resembles that of a mesenchymal stromal progenitor.

Mesenchymal stem cells confer chemoresistance in breast cancer via a CD9 dependent mechanism

The development of chemotherapy drug resistance remains a significant barrier for effective therapy in several cancers including breast cancer. Bone marrow-derived mesenchymal stem cells (BMMSCs) have previously been shown to influence tumor progression and the development of chemoresistance. In the present study, we showed that when GFP labelled BMMSCs and RFP labelled HCC1806 cells are injected together in vivo, they create tumors which contain a new hybrid cell that has characteristics of both BMMSCs and HCC1806 cells. By labelling these cells prior to their injection, we were then able to isolate new hybrid cell from harvested tumors using FACS (DP-HCC1806:BMMSCs). Interestingly, when DP-HCC1806:BMMSCs were then injected into the mammary fat pad of NOD/SCID mice, they produced xenograft tumors which were smaller in size, and exhibited resistance to chemotherapy drugs (i.e. doxorubicin and 5-fluorouracil), when compared tumors from HCC1806 cells alone. This chemoresistance was shown to associated with an increased expression of tetraspanins (CD9, CD81) and drug resistance proteins (BCRP, MDR1). Subsequent siRNA-mediated knockdown of BMMSC-CD9 in DP-HCC1806:BMMSCs resulted in an attenuation of doxorubicin and 5-fluorouracil chemoresistance associated with decreased BCRP and serum cytokine expression (CCL5, CCR5, CXCR12). Our findings suggest that within the tumor microenvironment, CD9 is responsible for the crosstalk between BMMSCs and HCC1806 breast cancer cells (via CCL5, CCR5, and CXCR12) which contributes to chemoresistance. Hence, BMMSC-CD9 may serve as an important therapeutic target for the treatment of breast cancer.

The role of stem cells in anti-aging medicine

Aging is the result of two overlapping processes, "intrinsic" and "extrinsic." Intrinsic structural changes occur as a consequence of physiologic aging and are genetically determined; extrinsic relates to exposure to harmful events and habits, like smoking, bad diet, alcohol consumption, lack of sleep, stress, sun exposure, environmental pollution, etc. Aging may be decelerated by improving bad habits or treating signs of aging with various esthetic methods, food supplements, and antioxidants. It is believed that we cannot stop aging entirely due to the intrinsic part, which leads to irreversible cell damage, as well as tissue and organ damage due to their limited ability to regenerate. Stem cells and their ability to exhibit telomerase activity, to self-renew, and to differentiate into all three embryonic tissues challenges aging as a process, which is not inevitable and can even possibly be reversed. Stem cells can promote regeneration of aged tissues and organs by replacing apoptotic and necrotic cells with healthy ones. In addition, they can have antiinflammatory and antiapoptotic properties by paracrine-secreting growth factors and cytokines on the site of administration. Autologous adipose-derived stem cells are the most promising because they can be easily harvested in huge numbers with minimally invasive liposuction and, as such, represent a powerful tool in anti-aging and regenerative medicine. In this contribution, the author discusses their properties and application in clinical practice.

Altered properties of feline adipose-derived mesenchymal stem cells during continuous in vitro cultivation

Cytotherapy with mesenchymal stem cells (MSCs) has been studied in many species, and often requires in vitro cell expansion to obtain therapeutic doses of stem cells. Because the characteristics of MSCs, such as self-renewal and multi-lineage differentiation, can be altered by long-term culture, it is important to maintain stemness during cultivation. This study assessed the changes in the characteristics of feline adipose tissue-derived (fAT)-MSCs during in vitro passaging. Stem cells isolated from the adipose tissue of donor cats were cultured for seven sub-passages. Proliferation capacity was analyzed by calculating the cell doubling time and by colorimetric assay. Expression of stem cell-specific markers was evaluated by quantitative reverse transcription (qRT)-PCR and immunophenotyping. Expression of adipogenic and osteogenic differentiation markers was also measured by qRT-PCR. Histochemical staining and measurement of β-galactosidase activity were conducted to detect cellular senescence. The cell proliferation rate decreased significantly at passage 5 (P5). Gene expression levels of pluripotency markers (Sox2, Nanog and Klf4) and stem cell surface markers (CD9, CD44, CD90 and CD105) decreased during continuous culture; in most assays, statistically significant changes were observed at P5. The ability of cells to undergo adipogenic or osteogenic differentiation was inversely proportional to the number of passages. The proportion of senescent cells increased with the number of passages. These results suggest that repeated passages alter the proliferation and multipotency of fAT-MSCs. In clinical trials, early-passage cells should be used to achieve the maximum therapeutic effect.

Cancer stem cell surface markers on normal stem cells

The cancer stem cell (CSC) hypothesis has captured the attention of many scientists. It is believed that elimination of CSCs could possibly eradicate the whole cancer. CSC surface markers provide molecular targeted therapies for various cancers, using therapeutic antibodies specific for the CSC surface markers. Various CSC surface markers have been identified and published. Interestingly, most of the markers used to identify CSCs are derived from surface markers present on human embryonic stem cells (hESCs) or adult stem cells. In this review, we classify the currently known 40 CSC surface markers into 3 different categories, in terms of their expression in hESCs, adult stem cells, and normal tissue cells. Approximately 73% of current CSC surface markers appear to be present on embryonic or adult stem cells, and they are rarely expressed on normal tissue cells. The remaining CSC surface markers are considerably expressed even in normal tissue cells, and some of them have been extensively validated as CSC surface markers by various research groups. We discuss the significance of the categorized CSC surface markers, and provide insight into why surface markers on hESCs are an attractive source to find novel surface markers on CSCs.

A PDGFRα-Mediated Switch toward CD9high Adipocyte Progenitors Controls Obesity-Induced Adipose Tissue Fibrosis

Obesity-induced white adipose tissue (WAT) fibrosis is believed to accelerate WAT dysfunction. However, the cellular origin of WAT fibrosis remains unclear. Here, we show that adipocyte platelet-derived growth factor receptor-α-positive (PDGFRα⁺) progenitors adopt a fibrogenic phenotype in obese mice prone to visceral WAT fibrosis. More specifically, a subset of PDGFRα⁺ cells with high CD9 expression (CD9^high) originates pro-fibrotic cells whereas their CD9^low counterparts, committed to adipogenesis, are almost completely lost in the fibrotic WAT. PDGFRα pathway activation promotes a phenotypic shift toward PDGFRα⁺CD9^high fibrogenic cells, driving pathological remodeling and altering WAT function in obesity. These findings translated to human obesity as the frequency of CD9^high progenitors in omental WAT (oWAT) correlates with oWAT fibrosis level, insulin-resistance severity, and type 2 diabetes. Collectively, our data demonstrate that in addition to representing a WAT adipogenic niche, different PDGFRα⁺ cell subsets modulate obesity-induced WAT fibrogenesis and are associated with loss of metabolic fitness.

Mesenchymal stem/stromal cells-a key mediator for regeneration after perinatal morbidity?

Perinatal complications in both term- and preterm-born infants are a leading cause of neonatal morbidities and mortality. Infants face different challenges in the neonatal intensive care unit with long-term morbidities such as perinatal brain injury and bronchopulmonary dysplasia being particularly devastating. While advances in perinatal medicine have improved our understanding of the pathogenesis, effective therapies to prevent and/or reduce the severity of these disorders are still lacking. The potential of mesenchymal stem/stromal cell (MSC) therapy has emerged during the last two decades, and an increasing effort is conducted to address brain- and lung-related morbidities in neonates at risk. Various studies support the notion that MSCs have protective effects. MSCs are an easy source and may be readily available after birth in a clinical setting. MSCs' mechanisms of action are diverse, including migration and homing, release of growth factors and immunomodulation, and the potential to replace injured cells. Here, we review the pathophysiology of perinatally acquired brain and lung injuries and focus on MSCs as potential candidates for therapeutic strategies summarizing preclinical and clinical evidence.

Therapeutic doses of multipotent stromal cells from minimal adipose tissue

Low yield of adult adipose-derived multipotent stromal cells (ASC) can limit autologous cell therapy in individuals with minimal adipose tissue. In this study, ASC isolation was optimized from approximately 0.2 g of feline epididymal adipose tissue for a treatment dose of 10⁶–10⁷ ASCs/kg. The ASC yield was determined for three digestions, 0.1 % collagenase in medium for 30 min (Classic), 0.3 % collagenase in buffer for 30 min (New) and 0.3 % collagenase in buffer for 1 h (Hour). After isolation by the new tissue digestion, continuously cultured ASCs (fresh) and cells recovered and expanded after cryostorage at P0 (revitalized) were characterized up to cell passage (P) 5. Outcomes included CD9, CD29, CD44, CD90 and CD105 expression, cell doublings and doubling times, fibroblastic, adipogenic and osteogenic colony forming unit (CFU) frequency percentages and lineage-specific target gene expression after induction. The New digestion had the highest CFU yield, and about 7x10⁶ ASCs/kg were available within three cell passages (P2). Compared to earlier passages, target surface antigen expression was lowest in fresh P5 cells, and fresh and revitalized P3–5 cells had slower expansion. Fresh and revitalized P1 ASCs had higher CFU frequency percentages and lineage-specific gene expression than P3. The New method described in this study was most efficient for feline epididymal ASC isolation and did not alter in vitro cell behavior. Fresh and revitalized P0-P2 feline ASCs may be most effective for preclinical and clinical trials. This study offers a potential option for ASC isolation from limited adipose tissue resources across species.

Role of motility-related protein-1 in promoting the development of several types of cancer (Review)

Motility-related protein-1 (CD9), a type of cell surface glycoprotein comprising a four-pass transmembrane domain that forms multimeric complexes with other cell surface proteins, belongs to the tetraspanins family. From previous studies, we know that CD9 is considered to function primarily as a progression and metastasis suppressor in a variety of cancers, including breast, non-small cell lung colon and myeloma. However, an expanding body of literature has shown the contradictory outcome that tetraspanin CD9 is also vital in promoting cancer progression in several types of cancer. This review summarizes the recent studies on CD9 and concludes that it does not always act as a progression and metastasis suppressor. Conversely, in specific cases, CD9 may promote tumor progression through the following three aspects: Facilitating tumor cell transmigration, increasing tumor cell motility and hastening the growth of some cancers. In addition, CD9 appears to be an important marker of cancer stem cells in certain types of tumor.

Metabolically active human brown adipose tissue derived stem cells

Brown adipose tissue (BAT) plays a key role in the evolutionarily conserved mechanisms underlying energy homeostasis in mammals. It is characterized by fat vacuoles 5-10 µm in diameter and expression of uncoupling protein one, central to the regulation of thermogenesis. In the human newborn, BAT depots are typically grouped around the vasculature and solid organs. These depots maintain body temperature during cold exposure by warming the blood before its distribution to the periphery. They also ensure an optimal temperature for biochemical reactions within solid organs. BAT had been thought to involute throughout childhood and adolescence. Recent studies, however, have confirmed the presence of active BAT in adult humans with depots residing in cervical, supraclavicular, mediastinal, paravertebral, and suprarenal regions. While human pluripotent stem cells have been differentiated into functional brown adipocytes in vitro and brown adipocyte progenitor cells have been identified in murine skeletal muscle and white adipose tissue, multipotent metabolically active BAT-derived stem cells from a single depot have not been identified in adult humans to date. Here, we demonstrate a clonogenic population of metabolically active BAT stem cells residing in adult humans that can: (a) be expanded in vitro; (b) exhibit multilineage differentiation potential; and (c) functionally differentiate into metabolically active brown adipocytes. Our study defines a new target stem cell population that can be activated to restore energy homeostasis in vivo for the treatment of obesity and related metabolic disorders.

Putative Population of Adipose-Derived Stem Cells Isolated from Mediastinal Tissue during Cardiac Surgery

Mesenchymal stem cells have been isolated from various adult human tissues and are valuable for not only therapeutic applications but for the study of tissue homeostasis and disease progression. Subcutaneous adipose depots have been shown to contain large amounts of stem cells. There is little information that has been reported to date describing the isolation and characterization of mesenchymal stem cells from visceral adipose tissue. In this study, we describe a mesenchymal stem cell population isolated from mediastinal adipose depots. The cells express CD44, CD105, CD166, and CD90 and are negative for hematopoietic markers CD34, CD45, and HLA-DR. In addition, the cells have a multilineage potential, with the ability to differentiate into adipogenic, osteogenic, and chondrogenic cell types. The biological function of visceral adipose tissue remains largely unknown and uncharacterized. However, the proximity of adipose tissue to the heart suggests a potential role in the pathogenesis of cardiovascular disease in obesity. In addition, with the ability of fat to regulate metabolic activity in humans, this novel stem cell source may be useful to further study the mechanisms involved in metabolic disorders.

Concise review: Adipose-derived stem cells as a novel tool for future regenerative medicine

The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs offers a paradigm shift that may provide alternative therapeutic solutions for a number of diseases. The use of either embryonic stem cells (ESCs) or induced pluripotent stem cells in clinical situations is limited due to cell regulations and to technical and ethical considerations involved in the genetic manipulation of human ESCs, even though these cells are, theoretically, highly beneficial. Mesenchymal stem cells seem to be an ideal population of stem cells for practical regenerative medicine, because they are not subjected to the same restrictions. In particular, large number of adipose-derived stem cells (ASCs) can be easily harvested from adipose tissue. Furthermore, recent basic research and preclinical studies have revealed that the use of ASCs in regenerative medicine is not limited to mesodermal tissue but extends to both ectodermal and endodermal tissues and organs, although ASCs originate from mesodermal lineages. Based on this background knowledge, the primary purpose of this concise review is to summarize and describe the underlying biology of ASCs and their proliferation and differentiation capacities, together with current preclinical and clinical data from a variety of medical fields regarding the use of ASCs in regenerative medicine. In addition, future directions for ASCs in terms of cell-based therapies and regenerative medicine are discussed.

Characterization of human adipose-derived stem cells and expression of chondrogenic genes during induction of cartilage differentiation

OBJECTIVES

Understanding the changes in chondrogenic gene expression that are involved in the differentiation of human adipose-derived stem cells to chondrogenic cells is important prior to using this approach for cartilage repair. The aims of the study were to characterize human adipose-derived stem cells and to examine chondrogenic gene expression after one, two, and three weeks of induction.

MATERIALS AND METHODS

Human adipose-derived stem cells at passage 4 were evaluated by flow cytometry to examine the expression of surface markers. These adipose-derived stem cells were tested for adipogenic and osteogenic differentiation capacity. Ribonucleic acid was extracted from the cells for quantitative polymerase chain reaction analysis to determine the expression levels of chondrogenic genes after chondrogenic induction.

RESULTS

Human adipose-derived stem cells were strongly positive for the mesenchymal markers CD90, CD73, CD44, CD9, and histocompatibility antigen and successfully differentiated into adipogenic and osteogenic lineages. The human adipose-derived stem cells aggregated and formed a dense matrix after chondrogenic induction. The expression of chondrogenic genes (collagen type II, aggrecan core protein, collagen type XI, COMP, and ELASTIN) was significantly higher after the first week of induction. However, a significantly elevated expression of collagen type X was observed after three weeks of chondrogenic induction.

CONCLUSION

Human adipose-derived stem cells retain stem cell characteristics after expansion in culture to passage 4 and serve as a feasible source of cells for cartilage regeneration. Chondrogenesis in human adipose-derived stem cells was most prominent after one week of chondrogenic induction.

Proteomic analysis of microvesicles derived from human mesenchymal stem cells

Mesenchymal stem cells (MSCs) have emerged as a promising means for treating degenerative or incurable diseases. Recent studies have shown that microvesicles (MVs) from MSCs (MSC-MVs) contribute to recovery of damaged tissues in animal disease models. Here, we profiled the MSC-MV proteome to investigate their therapeutic effects. LC-MS/MS analysis of MSC-MVs identified 730 MV proteins. The MSC-MV proteome included five positive and two variable known markers of MSCs, but no negative marker, as well as 43 surface receptors and signaling molecules controlling self-renewal and differentiation of MSCs. Functional enrichment analysis showed that cellular processes represented by the MSC-MV proteins include cell proliferation, adhesion, migration, and morphogenesis. Integration of MSC's self-renewal and differentiation-related genes and the proteome of MSC-conditioned media (MSC-CM) with the MSC-MV proteome revealed potential MV protein candidates that can be associated with the therapeutic effects of MSC-MVs: (1) surface receptors (PDGFRB, EGFR, and PLAUR); (2) signaling molecules (RRAS/NRAS, MAPK1, GNA13/GNG12, CDC42, and VAV2); (3) cell adhesion (FN1, EZR, IQGAP1, CD47, integrins, and LGALS1/LGALS3); and (4) MSC-associated antigens (CD9, CD63, CD81, CD109, CD151, CD248, and CD276). Therefore, the MSC-MV proteome provides a comprehensive basis for understanding the potential of MSC-MVs to affect tissue repair and regeneration.

Upregulation of CD9 in ovarian cancer is related to the induction of TNF-α gene expression and constitutive NF-κB activation

Ovarian cancer is a gynecological cancer with a high death rate. We utilized global gene expression profiles of ovarian carcinomas obtained by complementary DNA (cDNA) microarray to identify ovarian cancer-specific proteins. CD9 was upregulated in ovarian carcinomas, and overexpression of the CD9 protein was detected in ovarian carcinomas by immunohistochemistry. CD9 was also overexpressed in several cancer cell lines, including ovarian cancer cells. In order to elucidate the biological significance of highly expressed CD9 in cancer cells, functional studies of CD9 were performed by ectopic expression, knockdown of CD9 using small interfering RNA (siRNA) and blockage of CD9 activity using the CD9-specific monoclonal antibody ALB6. Ectopic CD9 induced cell survival. In order to identify signaling pathways related to CD9, the gene expressions of CD9/SKOV3 cells were analyzed by cDNA microarray. Among the many upregulated genes, tumor necrosis factor (TNF)-α was induced in CD9/SKOV3 cells. The effect of overexpressed CD9 on the downstream signaling events of TNF-α was further investigated. In CD9/SKOV3 cells, the nuclear factor-kappaB (NF-κB)-signaling pathway was constitutively activated. Knockdown of CD9 by siRNA and blockage of CD9 activity by ALB6 in ovarian cancer cells demonstrated that constitutive activation of NF-κB is CD9 dependent and that CD9 is involved in anti-apoptosis. A CD9 functional study was performed in an ovarian cancer-xenograft mouse by injecting ALB6 into the peritoneum. ALB6 resulted in reduced tumor weight compared with that of control IgG(1). Collectively, these results demonstrate that CD9 functions as an oncogene and represents a target for the development of cancer-specific therapeutics.

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

One of the advantages of human adipose-derived stem cells (ASCs) in regenerative medicine is that they can be harvested in abundance. However, the stemness biomarkers, which marked the safety and efficacy of ASCs in accordance with the good manufacturing practice guidelines, is not yet well established. This study was designed to investigate the effect of long-term culture on the stemness properties of ASCs using quantitative real-time polymerase chain reaction and flow cytometry. Results showed the growth rate of ASCs was at its peak when they reached P10 (population doubling; PD = 26) but started to decrease when they were expanded to P15 (PD = 36) and P20 (PD = 46). The ASCs can be culture expanded with minimal alteration in the stemness genes and cluster of differentiation (CD) markers expression up to P10. Expression level of Sox2, Nestin, and Nanog3 was significantly decreased at later passage. CD31, CD45, CD117, and human leukocyte antigen DR, DQ, and DP were lowly expressed at P5 and P10 but their expressions increased significantly at P15 or P20. The differentiation ability of ASCs (adipogenesis, osteogenesis, and neurogenesis) also decreased in long-term culture. Our findings suggested that P10 (PD = 26) should be the "cutoff point" for clinical usage because ASCs at passage 15 onward showed significant changes in the stemness genes, CD markers expression, and differentiation capability.

The human nose harbors a niche of olfactory ectomesenchymal stem cells displaying neurogenic and osteogenic properties

We previously identified multipotent stem cells within the lamina propria of the human olfactory mucosa, located in the nasal cavity. We also demonstrated that this cell type differentiates into neural cells and improves locomotor behavior after transplantation in a rat model of Parkinson's disease. Yet, next to nothing is known about their specific stemness characteristics. We therefore devised a study aiming to compare olfactory lamina propria stem cells from 4 individuals to bone marrow mesenchymal stem cells from 4 age- and gender-matched individuals. Using pangenomic microarrays and immunostaining with 34 cell surface marker antibodies, we show here that olfactory stem cells are closely related to bone marrow stem cells. However, olfactory stem cells also exhibit singular traits. By means of techniques such as proliferation assay, cDNA microarrays, RT-PCR, in vitro and in vivo differentiation, we report that when compared to bone marrow stem cells, olfactory stem cells display (1) a high proliferation rate; (2) a propensity to differentiate into osseous cells; and (3) a disinclination to give rise to chondrocytes and adipocytes. Since peripheral olfactory stem cells originate from a neural crest-derived tissue and, as shown here, exhibit an increased expression of neural cell-related genes, we propose to name them olfactory ectomesenchymal stem cells (OE-MSC). Further studies are now required to corroborate the therapeutic potential of OE-MSCs in animal models of bone and brain diseases.

Tetraspanin family protein CD9 in the mouse sperm: unique localization, appearance, behavior and fate during fertilization

A tetraspanin family protein, CD9, has not previously been identified in sperm cells. Here, we characterize sperm CD9 in the mouse, including its unique localization in sperm, appearance during spermatogenesis, and behavior and fate during mouse fertilization. In sperm, CD9 is an inner acrosomal membrane-associated protein, not a plasma membrane-associated protein. Its molecular weight is approximately 24 kDa throughout its processing, from testicular germ cells to acrosome-reacted sperm. A temporal difference was found between mRNA and protein expression; CD9 mRNA was detected in the stages from spermatogonia through round spermatids showing the strongest levels in midpachytene spermatocytes. CD9 protein was detected in the cytoplasm throughout the stages from spermatogonia to spermatocytes. While CD9 was weakly expressed in the spermatids from step 1 through step 14, the signals became clearly positive at the marginal region of the anterior acrosome in elongated spermatids. After the acrosome reaction, the majority of sperm CD9 was retained in the inner acrosomal membrane, but some quantity of CD9 was found on the plasma membrane covering the equatorial segment as detected by immunogold electron microscopy using anti-CD9 antibody. CD9 was maintained on the sperm head after reaching the perivitelline space of CD9-deficient eggs that were recovered after natural mating with wild males. Thus, this study characterizes CD9 in sperm development and fertilization.

Identification of mesenchymal stromal cells in human lung parenchyma capable of differentiating into aquaporin 5-expressing cells

The lack of effective therapies for end-stage lung disease validates the need for stem cell-based therapeutic approaches as alternative treatment options. In contrast with exogenous stem cell sources, the use of resident progenitor cells is advantageous considering the fact that the lung milieu is an ideal and familiar environment, thereby promoting the engraftment and differentiation of transplanted cells. Recent studies have shown the presence of multipotent 'mesenchymal stem cells' in the adult lung. The majority of these reports are, however, limited to animal models, and to date, there has been no report of a similar cell population in adult human lung parenchyma. Here, we show the identification of a population of primary human lung parenchyma (pHLP) mesenchymal stromal cells (MSCs) derived from intraoperative normal lung parenchyma biopsies. Surface and intracellular immunophenotyping by flow cytometry revealed that cultures do not contain alveolar type I epithelial cells or Clara cells, and are devoid of the following hematopoietic markers: CD34, CD45 and CXCR4. Cells show an expression pattern of surface antigens characteristic of MSCs, including CD73, CD166, CD105, CD90 and STRO-1. As per bone marrow MSCs, our pHLP cells have the ability to differentiate along the adipogenic, osteogenic and chondrogenic mesodermal lineages when cultured in the appropriate conditions. In addition, when placed in small airway growth media, pHLP cell cultures depict the expression of aquaporin 5 and Clara cell secretory protein, which is identified with that of alveolar type I epithelial cells and Clara cells, respectively, thereby exhibiting the capacity to potentially differentiate into airway epithelial cells. Further investigation of these resident cells may elucidate a therapeutic cell population capable of lung repair and/or regeneration.

Interplay between Numb and Notch in epithelial cancers: role for dual oxidase maturation factor

Numb and Notch signalling pathways are vitally important in cell fate and differentiation. The outcome of these signalling processes is determined by a delicate balance between opposing effects of Notch and Numb. Imbalance in Numb/Notch regulation was implicated in aberrant differentiation programme and epithelial cancer progression and metastasis. Recent identification of Numb-interacting protein (NIP), which is also known as dual oxidase maturation factor, and was shown to associate with Numb and DUOX and promote their translocation, sheds a new light on how Numb/Notch network may be coordinated in epithelial cancers. Here, a possible link between Numb, Notch and Dual oxidase maturation factor is examined.

The use of fibrin based matrices and fibrin microbeads (FMB) for cell based tissue regeneration

BACKGROUND

Due to its good cell attachment capabilities and promotion of cell migration, fibrin serves as an interim cell-binding matrix in wounded tissues. Due to their fast degradation, unprocessed fibrin matrices have limited use in tissue engineering.

OBJECTIVE

To describe stable fibrin-based matrices for isolation, growth and delivery of stem cells for implantation to enhance tissue regeneration.

METHODS

Fibrin microbeads (FMB) were produced by moderate-heat condensation of fibrin particles in oil without compromising the cell binding capability of the fibrin.

RESULTS

Mesenchymal stem cells (MSC) were separated from different sources at much higher yields with FMB. They were further expanded on them in suspension without trypsinization and passages. Cells on FMB could be induced to differentiate into different phenotypes, such as bone and cartilage. This enabled implantation of the cells on FMB for cell-based tissue regeneration.

CONCLUSIONS

FMB technology provides a simple and effective method for cell separation, expansion in suspension and delivery for tissue regeneration.