Insulin-like growth factor binding proteins 4 and 7 released by senescent cells promote premature senescence in mesenchymal stem cells

Senescent mesenchymal stem cells remodel extracellular matrix driving breast cancer cells to a more-invasive phenotype

Mesenchymal stem cells (MSCs) are essential for the regenerative process; however, biological aging and environmental stress can induce senescence - an irreversible state of growth arrest - that not only affects the behavior of cells but also disrupts their ability to restore tissue integrity. While abnormal tissue properties, including increased extracellular matrix stiffness, are linked with the risk of developing breast cancer, the role and contribution of senescent MSCs to the disease progression to malignancy are not well understood. Here, we investigated senescence-associated biophysical changes in MSCs and how this influences cancer cell behavior in a 3D matrix interface model. Although senescent MSCs were far less motile than pre-senescent MSCs, they induced an invasive breast cancer phenotype, characterized by increased spheroid growth and cell invasion in collagen gels. Further analysis of collagen gels using second-harmonic generation showed increased collagen density when senescent MSCs were present, suggesting that senescent MSCs actively remodel the surrounding matrix. This study provides direct evidence of the pro-malignant effects of senescent MSCs in tumors.

Recurrent pregnancy loss is associated with a pro-senescent decidual response during the peri-implantation window

During the implantation window, the endometrium becomes poised to transition to a pregnant state, a process driven by differentiation of stromal cells into decidual cells (DC). Perturbations in this process, termed decidualization, leads to breakdown of the feto-maternal interface and miscarriage, but the underlying mechanisms are poorly understood. Here, we reconstructed the decidual pathway at single-cell level in vitro and demonstrate that stromal cells first mount an acute stress response before emerging as DC or senescent DC (snDC). In the absence of immune cell-mediated clearance of snDC, secondary senescence transforms DC into progesterone-resistant cells that abundantly express extracellular matrix remodelling factors. Additional single-cell analysis of midluteal endometrium identified DIO2 and SCARA5 as marker genes of a diverging decidual response in vivo. Finally, we report a conspicuous link between a pro-senescent decidual response in peri-implantation endometrium and recurrent pregnancy loss, suggesting that pre-pregnancy screening and intervention may reduce the burden of miscarriage.

Paracrine senescence of human endometrial mesenchymal stem cells: a role for the insulin-like growth factor binding protein 3

Stress-induced premature cell senescence is well recognized to be accompanied by emerging the senescence-associated secretory phenotype (SASP). Secreted SASP factors can promote the senescence of normal neighboring cells through autocrine/paracrine pathways and regulate the senescence response, as well. Regarding human endometrium-derived mesenchymal stem cells (MESCs), the SASP regulation mechanisms as well as paracrine activity of senescent cells have not been studied yet. Here, we examined the role of insulin-like growth factor binding protein 3 (IGFBP3) in the paracrine senescence induction in young MESCs. The H₂O₂-induced premature senescence of MESCs led to increased IGFBP3 in conditioned media (CM). The inhibitory analysis of both MAPK and PI3K signaling pathways showed that IGFBP3 releasing from senescent cells is mainly regulated by PI3K/Akt pathway activity. IGFBP3 appears to be an important senescence-mediating factor as its immunodepletion from the senescent CM weakened the pro-senescent effect of CM on young MESCs and promoted their growth. In contrast, young MESCs acquired the senescence phenotype in response to simultaneous addition of recombinant IGFBP3 (rIGFBP3). The mechanism of extracellular IGFBP3 internalization was also revealed. The present study is the first to demonstrate a significant role of extracellular IGFBP3 in paracrine senescence induction of young MESCs.

Premature cell senescence in human skin: Dual face in chronic acquired pigmentary disorders

Although senescence was originally described as an in vitro acquired cellular characteristic, it was recently recognized that senescence is physiologically and pathologically involved in aging and age-related diseases in vivo. The definition of cellular senescence has expanded to include the growth arrest caused by various cellular stresses, including DNA damage, inadequate mitochondria function, activated oncogene or tumor suppressor genes and oxidative stress. While senescence in normal aging involves various tissues over time and contributes to a decline in tissue function even with healthy aging, disease-induced premature senescence may be restricted to one or a few organs triggering a prolonged and more intense rate of accumulation of senescent cells than in normal aging. Organ-specific high senescence rate could lead to chronic diseases, especially in post-mitotic rich tissue. Recently, two opposite acquired pathological conditions related to skin pigmentation were described to be associated with premature senescence: vitiligo and melasma. In both cases, it was demonstrated that pathological dysfunctions are not restricted to melanocytes, the cell type responsible for melanin production and transport to surrounding keratinocytes. Similar to physiological melanogenesis, dermal and epidermal cells contribute directly and indirectly to deregulate skin pigmentation as a result of complex intercellular communication. Thus, despite senescence usually being reported as a uniform phenotype sharing the expression of characteristic markers, skin senescence involving mainly the dermal compartment and its paracrine function could be associated with the disappearance of melanocytes in vitiligo lesions and with the exacerbated activity of melanocytes in the hyperpigmentation spots of melasma. This suggests that the difference may arise in melanocyte intrinsic differences and/or in highly defined microenvironment peculiarities poorly explored at the current state of the art. A similar dualistic phenotype has been attributed to intratumoral stromal cells as cancer-associated fibroblasts presenting a senescent-like phenotype which influence the behavior of neoplastic cells in either a tumor-promoting or tumor-inhibiting manner. Here, we present a framework dissecting senescent-related molecular alterations shared by vitiligo and melasma patients and we also discuss disease-specific differences representing new challenges for treatment.

Insulin-like growth factor-binding protein 7 (IGFBP7): Novel, independent marker of cardiometabolic diseases?

Insulin-like growth factor-binding protein 7 (IGFBP7) is a 30kDa modular secreted protein involved in many physiologic processes, including cell proliferation, adhesion, senescence and angiogenesis. It is expressed in many organs and specific cells. It can interact with insulin-like growth factor 1(IGF-1), as well as with insulin. By binding to IGF-1, it limits IGF-1 access to IGF- receptor (IGF-R) and consequently neutralizes IGF-1 activity. Moreover, due to its high affinity to insulin, it may interfere with biological response of insulin and, therefore, it may be involved in the development of diabetes and cardiovascular diseases. According to research, it could be a good biomarker of heart failure. Its elevated serum concentrations were found in patients with heart failure, both with reduced ejection fraction and preserved ejection fraction. Moreover, IGFBP7 could be useful in predicting the presence of atherosclerotic lesions in coronary vessels, although its concentration does not reflect a degree of coronary artery disease (CAD) advancement and it cannot be used as a marker of acute ischemia. Its concentration is also associated with insulin resistance and the risk of metabolic syndrome. What is more, together with tissue inhibitor of metalloproteinases-2, it is a novel marker of tubular damage and it can be used for an early detection of acute kidney injury (AKI) endangered patients, which could allow for subsequent adjustments in medical therapy and the prevention of AKI. IGFBP7 is also regarded as a potential tumor suppressor in various cancers. Its low expression is potentially correlated with increased cancer cell proliferation.

Molecular basis of senescence transmitting in the population of human endometrial stromal cells

Hormone-regulated proliferation and differentiation of endometrial stromal cells (ESCs) determine overall endometrial plasticity and receptivity to embryos. Previously we revealed that ESCs may undergo premature senescence, accompanied by proliferation loss and various intracellular alterations. Here we focused on whether and how senescence may be transmitted within the ESCs population. We revealed that senescent ESCs may induce paracrine senescence in young counterparts via cell contacts, secreted factors and extracellular vesicles. According to secretome-wide profiling we identified plasminogen activator inhibitor -1 (PAI-1) to be the most prominent protein secreted by senescent ESCs (data are available via ProteomeXchange with identifier PXD015742). By applying CRISPR/Cas9 techniques we disclosed that PAI-1 secreted by senescent ESCs may serve as the master-regulator of paracrine senescence progression within the ESCs population. Unraveled molecular basis of senescence transduction in the ESCs population may be further considered in terms of altered endometrial plasticity and sensitivity to invading embryo, thus contributing to the female infertility curing.

Quantitative iTRAQ-based proteomic analysis of differentially expressed proteins in aging in human and monkey

BACKGROUND

The underlying physiological mechanisms associated with aging are still complex and unclear. As a very important tissue of human body, the circulatory system also plays a very important role in the process of aging. In this study, we use the isobaric tags for relative and absolute quantification (iTRAQ) method to identify differentially expressed proteins in plasma for humans and monkeys between young and aged. Western blotting and behavioral experiment in mice were performed to validate the expression of the candidate protein.

RESULTS

Between the young / the old humans and the young / the old monkeys 74 and 69 proteins were found to be differently expressed, respectively. For the human samples, these included 38 up-regulated proteins and 36 down-regulated proteins (a fold change ≥1.3 or ≤ 0.667, p value ≤0.05).For the monkey samples, 51 up-regulated proteins and 18 down-regulated proteins (a fold change ≥1.3 or ≤ 0.667, p value ≤0.05). KEGG pathway analysis revealed that phagosome, focal adhesion, ECM-receptor interaction and PI3K/AKT signaling pathway were the most common pathways involved in aging. We found only IGFBP4 protein that existed in up-regulated proteins in aged both for human and monkey. In addition, the differential expression of IGFBP4 was validated by western blot analysis and IGFBP4 treatment mimicked aging-related cognitive dysfunction in mice.

CONCLUSIONS

This first, the integrated proteomics for the plasma protein of human and monkey reveal one protein-IGFBP4, which was validated by western blotting and behavioral analysis can promote the process of aging. And, iTRAQ analysis showed that proteolytic systems, and inflammatory responses plays an important role in the process of aging. These findings provide a basis for better understanding of the underlying mechanisms involved in aging.

Loss of SATB1 Induces p21-Dependent Cellular Senescence in Post-mitotic Dopaminergic Neurons

Cellular senescence is a mechanism used by mitotic cells to prevent uncontrolled cell division. As senescent cells persist in tissues, they cause local inflammation and are harmful to surrounding cells, contributing to aging. Generally, neurodegenerative diseases, such as Parkinson's, are disorders of aging. The contribution of cellular senescence to neurodegeneration is still unclear. SATB1 is a DNA binding protein associated with Parkinson's disease. We report that SATB1 prevents cellular senescence in post-mitotic dopaminergic neurons. Loss of SATB1 causes activation of a cellular senescence transcriptional program in dopamine neurons both in human stem cell-derived dopaminergic neurons and in mice. We observed phenotypes that are central to cellular senescence in SATB1 knockout dopamine neurons in vitro and in vivo. Moreover, we found that SATB1 directly represses expression of the pro-senescence factor p21 in dopaminergic neurons. Our data implicate senescence of dopamine neurons as a contributing factor in the pathology of Parkinson's disease.

The senescence-associated secretory phenotype (SASP) from mesenchymal stromal cells impairs growth of immortalized prostate cells but has no effect on metastatic prostatic cancer cells

Senescent cells secrete inflammatory cytokines, proteases, and other factors, which are indicated as senescence-associated secretory phenotype (SASP). There are contrasting studies on the role of the SASP in cancer. Studies suggested that cancer cells may misuse the senescent secretome for their growth. Other investigations evidenced that the SASP may induce cancer growth arrest, senescence, or apoptosis. These conflicting data can be reconciled considering that cancer cells can coax senescent cells to secrete factors for their survival, thus abrogating the SASP's anti-cancer effect. Cancer stage may also have an impact on the capacity of the SASP to block tumor proliferation and promote senescence. Indeed, senescence is associated with a permanent cell cycle arrest, which needs functional cell cycle checkpoints. We evaluated the SASP effect on the in vitro biological properties of PNT2 and PC3 cells, which are immortalized prostate cells and metastatic prostatic cancer cells, respectively. We evidenced that SASPs, coming either from mesenchymal stromal cells treated with H202 or with low X-ray doses, induced senescence of immortalized cells but not of cancer cells. Hence, the SASP released by acute senescent cells should be considered as an effective weapon against pre-tumorigenesis events rather than an anti-cancer mechanism acting on malignant cells.

IGFBP7 (Insulin-Like Growth Factor-Binding Protein-7) and Neprilysin Inhibition in Patients With Heart Failure

BACKGROUND

Increased activity of IGFBP7 (insulin-like growth factor-binding protein-7) is associated with cellular senescence, tissue aging, and obesity. IGFBP7 may be related to heart failure with preserved ejection fraction, a disease of elderly obese people.

METHODS AND RESULTS

In a subset of patients with heart failure with preserved ejection fraction (N=228) randomized to receive sacubitril/valsartan versus valsartan, IGFBP7 concentrations were measured at baseline, 12 weeks, and 36 weeks. Patient characteristics and echocardiographic measures including left atrial (LA) size and volume, ratio of early mitral inflow velocity/annular diastolic velocity, and ratio of early diastole/peak late diastolic velocity were assessed as a function of IGFBP7 concentration. Effect of sacubitril/valsartan on IGFBP7 concentrations was analyzed. With increasing baseline IGFBP7 quartiles, LA size and LA volume index (LAVi) were higher (both P<0.001); modest association between IGFBP7 and higher early mitral inflow velocity/annular diastolic velocity ( P=0.03) and early diastole/peak late diastolic velocity ratio ( P=0.04) was also seen. IGFBP7 concentrations were higher in those with LAVi ≥34 mL/m² compared with lower LAVi at all time points (all P<0.01). IGFBP7 independently predicted LAVi at baseline even in the presence of NT-proBNP (N-terminal pro-B-type natriuretic peptide) concentrations; highest LAVi was seen in those with elevation in both biomarkers. Treatment with sacubitril/valsartan resulted in lower IGFBP7 concentrations over 36 weeks compared with valsartan (adjusted treatment effect, -7%; P<0.001).

CONCLUSIONS

Among patients with heart failure with preserved ejection fraction, concentrations of the cellular senescence biomarker IGFBP7 were associated with abnormalities in diastolic filling and LA dilation. Treatment with sacubitril/valsartan resulted in lower IGFBP7 concentrations compared with valsartan.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT00887588.

Comparative Assessment of Antitumor Effects and Autophagy Induction as a Resistance Mechanism by Cytotoxics and EZH2 Inhibition in INI1-Negative Epithelioid Sarcoma Patient-Derived Xenograft

Epithelioid sarcoma (ES) is a rare mesenchymal malignancy marked by SMARCB1/INI1 deficiency. Retrospective clinical data report on the activity of anthracycline- and gemcitabine-based regimens. EZH2 inhibitors are currently being tested in clinical trials. Since comparisons of these agents are unlikely to be prospectively evaluated in the clinics, we took advantage of an INI1-deficient proximal-type ES patient-derived xenograft (PDX ES-1) to comparatively assess its preclinical antitumor activity. Mice were treated with doxorubicin and ifosfamide, singly or in combination, gemcitabine, and the EZH2 inhibitor EPZ-011989. Comparable antitumor activity (max tumor volume inhibition: ~90%) was caused by gemcitabine, EPZ-011989, and the doxorubicin-ifosfamide combination. The integration of RNAseq data, generated on tumors obtained from untreated and EPZ-011989-treated mice, and results from functional studies, carried out on the PDX-derived ES-1 cell line, revealed autophagy induction as a possible survival mechanism in residual tumor cells following EPZ-011989 treatment and identified HMGA2 as a main player in this process. Our data support the clinical use of gemcitabine and the doxorubicin-ifosfamide combination, confirm EZH2 as a therapeutic target in proximal-type ES, and suggest autophagy as a cytoprotective mechanism against EZH2 inhibition.

Effect of aging on behaviour of mesenchymal stem cells

Organs whose source is the mesoderm lineage contain a subpopulation of stem cells that are able to differentiate among mesodermal derivatives (chondrocytes, osteocytes, adipocytes). This subpopulation of adult stem cells, called "mesenchymal stem cells" or "mesenchymal stromal cells (MSCs)", contributes directly to the homeostatic maintenance of their organs; hence, their senescence could be very deleterious for human bodily functions. MSCs are easily isolated and amenable their expansion in vitro because of the research demanding to test them in many diverse clinical indications. All of these works are shown by the rapidly expanding literature that includes many in vivo animal models. We do not have an in-depth understanding of mechanisms that induce cellular senescence, and to further clarify the consequences of the senescence process in MSCs, some hints may be derived from the study of cellular behaviour in vivo and in vitro, autophagy, mitochondrial stress and exosomal activity. In this particular work, we decided to review these biological features in the literature on MSC senescence over the last three years.

Bone marrow mesenchymal stem cells: Aging and tissue engineering applications to enhance bone healing

Bone has well documented natural healing capacity that normally is sufficient to repair fractures and other common injuries. However, the properties of bone change throughout life, and aging is accompanied by increased incidence of bone diseases and compromised fracture healing capacity, which necessitate effective therapies capable of enhancing bone regeneration. The therapeutic potential of adult mesenchymal stem cells (MSCs) for bone repair has been long proposed and examined. Actions of MSCs may include direct differentiation to become bone cells, attraction and recruitment of other cells, or creation of a regenerative environment via production of trophic growth factors. With systemic aging, MSCs also undergo functional decline, which has been well investigated in a number of recent studies. In this review, we first describe the changes in MSCs during aging and discuss how these alterations can affect bone regeneration. We next review current research findings on bone tissue engineering, which is considered a promising and viable therapeutic solution for structural and functional restoration of bone. In particular, the importance of MSCs and bioscaffolds is highlighted. Finally, potential approaches for the prevention of MSC aging and the rejuvenation of aged MSC are discussed.

Intraarticular senescent chondrocytes impair the cartilage regeneration capacity of mesenchymal stem cells

Background

Senescent cells exert a significant influence over their surrounding cellular environment. Senescent chondrocytes (SnChos) were found to be accumulated in degenerated cartilage present in joints affected by osteoarthritis. The influence of SnChos on exogenously transplanted stem cells has yet to be reported.

Methods

In this study, we evaluated the interactions between SnChos and bone marrow mesenchymal stem cells (BMSCs) when co-cultured as well as in the intra-articular senescent microenvironment (IASM). The effect of IASM on cartilage regeneration was also assessed.

Results

It was found that a small fraction of SnChos induced BMSC cellular senescence and apoptosis. SnChos also inhibited proliferation, facilitated stemness, and suppressed chondrogenic differentiation of BMSCs. BMSCs induced the apoptosis of SnChos, reduced the proportion of SnChos, stimulated SnChos proliferation, and revealed a bidirectional effect on SnChos inflammaging. IASM significantly suppressed the survival, proliferation, and appropriate differentiation of grafted BMSCs in vivo, all of which impaired cartilage regeneration. Anti-senescence agent ABT-263 was able to partly rescue the cells from the negative effects of SnChos.

Conclusions

The SnChos and BMSCs interacted with each other at cellular senescence, apoptosis, proliferation, differentiation, and cell functions. This interaction impaired the cartilage repair of MSCs. Anti-senescence agent provided a possible solution for this impairment.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1193-1) contains supplementary material, which is available to authorized users.

Manufacturing of primed mesenchymal stromal cells for therapy

Mesenchymal stromal cells (MSCs) for basic research and clinical applications are manufactured and developed as unique cell products by many different manufacturers and laboratories, often under different conditions. The lack of standardization of MSC identity has limited consensus around which MSC properties are relevant for specific outcomes. In this Review, we examine how the choice of media, cell source, culture environment and storage affects the phenotype and clinical utility of MSC-based products, and discuss the techniques better suited to prime MSCs with specific phenotypes of interest and the need for the continued development of standardized assays that provide quality assurance for clinical-grade MSCs. Bioequivalence between cell products and batches must be investigated rather than assumed, so that the diversity of phenotypes between differing MSC products can be accounted for to identify products with the highest therapeutic potential and to preserve their safety in clinical treatments.

Senescent cell clearance by the immune system: Emerging therapeutic opportunities

Senescent cells (SCs) arise from normal cells in multiple organs due to inflammatory, metabolic, DNA damage, or tissue damage signals. SCs are non-proliferating but metabolically active cells that can secrete a range of pro-inflammatory and proteolytic factors as part of the senescence-associated secretory phenotype (SASP). Senescent cell anti-apoptotic pathways (SCAPs) protect SCs from their own pro-apoptotic SASP. SCs can chemo-attract immune cells and are usually cleared by these immune cells. During aging and in multiple chronic diseases, SCs can accumulate in dysfunctional tissues. SCs can impede innate and adaptive immune responses. Whether immune system loss of capacity to clear SCs promotes immune system dysfunction, or conversely whether immune dysfunction permits SC accumulation, are important issues that are not yet fully resolved. SCs may be able to assume distinct states that interact differentially with immune cells, thereby promoting or inhibiting SC clearance, establishing a chronically pro-senescent and pro-inflammatory environment, leading to modulation of the SASP by the immune cells recruited and activated by the SASP. Therapies that enhance immune cell-mediated clearance of SCs could provide a lever for reducing SC burden. Such therapies could include vaccines, small molecule immunomodulators, or other approaches. Senolytics, drugs that selectively eliminate SCs by transiently disabling their SCAPs, may prove to alleviate immune dysfunction in older individuals and thereby accelerate immune-mediated clearance of SCs. The more that can be understood about the interplay between SCs and the immune system, the faster new interventions may be developed to delay, prevent, or treat age-related dysfunction and the multiple senescence-associated chronic diseases and disorders.

Senescent Cells Drive Frailty through Systemic Signals

Senescent cells drive ageing and the associated loss in health and lifespan. Whether this is mediated by systemic signalling remained unclear. Recently, Xu et al. [1] (Nat. Med. 2018;24:1246-1256) answered this question by injecting senescent cells into young mice and observing a long-lasting increase in frailty and mortality.

Insulin-like growth factor binding protein 4 inhibits proliferation of bone marrow mesenchymal stem cells and enhances growth of neurospheres derived from the stem cells

Insulin-like growth factor binding protein 4 (IGFBP-4) was reported to trigger cellular senescence and reduce cell growth of bone marrow mesenchymal stem cells (BMSCs), but its contribution to neurogenic differentiation of BMSCs remains unknown. In the present study, BMSCs were isolated from the femur and tibia of young rats to investigate effects of IGFBP-4 on BMSC proliferation and growth of neurospheres derived from BMSCs. Bone marrow mesenchymal stem cell proliferation was assessed using CCK-8 after treatment with IGFBP-4 or blockers of IGF-IR and β-catenin. Phosphorylation levels of Akt, Erk, and p38 in BMSCs were analysed by Western blotting. Bone marrow mesenchymal stem cells were induced into neural lineages in NeuroCult medium; the number and the size of BMSC-derived neurospheres were counted after treatment with IGFBP-4 or the blockers. It was shown that addition of IGFBP-4 inhibited BMSC proliferation and immunodepletion of IGFBP-4 increased the proliferation. The blockade of IGF-IR with AG1024 increased BMSC proliferation and reversed IGFBP-4-induced proliferation inhibition; however, blocking of β-catenin with FH535 did not. p-Erk was significantly decreased in IGFBP-4-treated BMSCs. IGFBP-4 promoted the growth of neurospheres derived from BMSCs, as manifested by the increases in the number and the size of the derived neurospheres. Both AG1024 and FH535 inhibited the formation of NeuroCult-induced neurospheres, but FH535 significantly inhibited the growth of neurospheres in NeuroCult medium with EGF, bFGF, and IGFBP-4. The data suggested that IGFBP-4 inhibits BMSC proliferation through IGF-IR pathway and promotes growth of BMSC-derived neurospheres via stabilizing β-catenin.

IGF-binding proteins

Insulin-like growth factor-binding proteins (IGFBPs) 1-6 bind IGFs but not insulin with high affinity. They were initially identified as serum carriers and passive inhibitors of IGF actions. However, subsequent studies showed that, although IGFBPs inhibit IGF actions in many circumstances, they may also potentiate these actions. IGFBPs are widely expressed in most tissues, and they are flexible endocrine and autocrine/paracrine regulators of IGF activity, which is essential for this important physiological system. More recently, individual IGFBPs have been shown to have IGF-independent actions. Mechanisms underlying these actions include (i) interaction with non-IGF proteins in compartments including the extracellular space and matrix, the cell surface and intracellular space, (ii) interaction with and modulation of other growth factor pathways including EGF, TGF-β and VEGF, and (iii) direct or indirect transcriptional effects following nuclear entry of IGFBPs. Through these IGF-dependent and IGF-independent actions, IGFBPs modulate essential cellular processes including proliferation, survival, migration, senescence, autophagy and angiogenesis. They have been implicated in a range of disorders including malignant, metabolic, neurological and immune diseases. A more complete understanding of their cellular roles may lead to the development of novel IGFBP-based therapeutic opportunities.

GATA4-dependent regulation of the secretory phenotype via MCP-1 underlies lamin A-mediated human mesenchymal stem cell aging

Defects in the nuclear lamina occur during physiological aging and as a result of premature aging disorders. Aging is also accompanied by an increase in transcription of genes encoding cytokines and chemokines, a phenomenon known as the senescence-associated secretory phenotype (SASP). Progerin and prelamin A trigger premature senescence and loss of function of human mesenchymal stem cells (hMSCs), but little is known about how defects in nuclear lamin A regulate SASP. Here, we show that both progerin overexpression and ZMPSTE24 depletion induce paracrine senescence, especially through the expression of monocyte chemoattractant protein-1 (MCP-1), in hMSCs. Importantly, we identified that GATA4 is a mediator regulating MCP-1 expression in response to prelamin A or progerin in hMSCs. Co-immunoprecipitation revealed that GATA4 expression is maintained due to impaired p62-mediated degradation in progerin-expressing hMSCs. Furthermore, depletion of GATA4 abrogated SASP-dependent senescence through suppression of NF-ĸB and MCP-1 in hMSCs with progerin or prelamin A. Thus, our findings indicate that abnormal lamin A proteins trigger paracrine senescence through a GATA4-dependent pathway in hMSCs. This molecular link between defective lamin A and GATA4 can provide insights into physiological aging and pathological aging disorders.

Abnormal versions of proteins that support the structure and function of the membrane of the cell nucleus are implicated in premature aging disorders, and also in normal aging. Researchers in South Korea led by Kyung-Sun Kang at Seoul National University investigated the protein network known as the nuclear lamina. They studied a specific type of human stem cell that gives rise to bone, cartilage, muscle and fat. They found that altering the levels of proteins produced by specific key genes promotes cell aging, and the alterations led to abnormalities in the proteins of the nuclear lamina. The researchers suggest that their work provides new insights into the molecular and cellular causes of premature and normal aging. Understanding the molecular triggers of aging could lead to treatments to delay both its normal and disease-linked forms.

Secretome analysis of in vitro aged human mesenchymal stem cells reveals IGFBP7 as a putative factor for promoting osteogenesis

Aging is a complex biological process, which involves multiple mechanisms with different levels of regulation. Senescent cells are known to secrete senescence-associated proteins, which exert negative influences on surrounding cells. Mesenchymal stem cells (MSCs), the common progenitors for bone, cartilage and adipose tissue (which are especially affected tissues in aging), are known to secrete a broad spectrum of biologically active proteins with both paracrine and autocrine functions in many biological processes. In this report, we have studied the secreted factors (secretome) from human MSCs (hMSCs) and hMSCs-derived adipocytes which were induced to accumulate prelamin A, the immature form of the nuclear lamina protein called Lamin A, known to induce premature aging syndromes in humans and in murine models. Proteomic analysis from two different techniques, antibody arrays and LS-MS, showed that prelamin A accumulation in hMSCs promotes the differential secretion of factors previously identified as secreted by hMSCs undergoing osteogenesis. Moreover, this secretome was able to modulate osteogenesis of normal hMSCs in vitro. Finally, we found that one of the overexpressed secreted factors of this human aging in vitro stem cell model, IGFBP-7, is an osteogenic factor, essential for the viability of hMSCs during osteogenesis.

Patient-derived ovarian cancer xenografts re-growing after a cisplatinum treatment are less responsive to a second drug re-challenge: a new experimental setting to study response to therapy

Even if ovarian cancer patients are very responsive to a cisplatinum-based therapy, most will relapse with a resistant disease. New experimental animal models are needed to explore the mechanisms of resistance, to better tailor treatment and improve patient prognosis. To address these aims, seven patient-derived high-grade serous/endometrioid ovarian cancer xenografts were characterized for the antitumor response after one and two cycles of cisplatinum and classified as Very Responsive, Responsive, and Low Responsive to drug treatment. Xenografts re-growing after the first drug cycle were much less responsive to the second one. The expression of epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs) genes was investigated in cisplatinum-treated and not-treated tumors. We found that different EMT (TCF3, CAMK2N1, EGFR, and IGFBP4) and CSCs (SMO, DLL1, STAT3, and ITGA6) genes were expressed at higher levels in Low Responsive than in Responsive and Very Responsive xenografts. The expression of STAT3 was found to be associated with lower survival (HR = 13.7; p = 0.013) in the TCGA patient data set. MMP9, CD44, DLL4, FOXP1, MERTK, and PTPRC genes were found more expressed in tumors re-growing after cisplatinum treatment than in untreated tumors. We here describe a new in vivo ovarian carcinoma experimental setting that will be instrumental for specific trials of combination therapy to counteract cisplatinum resistance in order to improve the prognosis of ovarian patients.

What Happened to the IGF Binding Proteins?

Insulinlike growth factor (IGF) binding proteins (IGFBPs) 1 to 6 are high-affinity regulators of IGF activity. They generally inhibit IGF actions by preventing binding to the IGF-I receptor but can also enhance their actions under some conditions. Posttranslational modifications such as glycosylation and phosphorylation modulate IGFBP properties, and IGFBP proteolysis results in IGF release. IGFBPs have more recently been shown to have IGF-independent actions. A number of mechanisms are involved, including modulation of other growth factor pathways, nuclear localization and transcriptional regulation, interaction with the sphingolipid pathway, and binding to non-IGF biomolecules in the extracellular space and matrix, on the cell surface and intracellularly. IGFBPs modulate important biological processes, including cell proliferation, survival, migration, senescence, autophagy, and angiogenesis. Their actions have been implicated in growth, metabolism, cancer, stem cell maintenance and differentiation, and immune regulation. Recent studies have shown that epigenetic mechanisms are involved in the regulation of IGFBP abundance. A more complete understanding of IGFBP biology is necessary to further define their cellular roles and determine their therapeutic potential.

Senescence-messaging secretome factors trigger premature senescence in human endometrium-derived stem cells

Accumulating evidence suggests that the senescence-messaging secretome (SMS) factors released by senescent cells play a key role in cellular senescence and physiological aging. Phenomenon of the senescence induction in human endometrium-derived mesenchymal stem cells (MESCs) in response to SMS factors has not yet been described. In present study, we examine a hypothesis whether the conditioned medium from senescent cells (CM-old) may promote premature senescence of young MESCs. In this case, we assume that SMS factors, containing in CM-old are capable to trigger senescence mechanism in a paracrine manner. A long-term cultivation MESCs in the presence of CM-old caused deceleration of cell proliferation along with emerging senescence phenotype, including increase in both the cell size and SA-β-Gal activity. The phosphorylation of p53 and MAPKAPK-2, a direct target of p38MAPK, as well as the expression of p21Cip1 and p16Ink4a were increased in CM-old treated cells with senescence developing whereas the Rb phosphorylation was diminished. The senescence progression was accompanied by both enhanced ROS generation and persistent activation of DNA damage response, comprising protein kinase ATM, histone H2A.X, and adapter protein 53BP1. Thus, we suggest that a senescence inducing signal is transmitted through p16/MAPKAPK-2/Rb and DDR-mediated p53/p21/Rb signaling pathways. This study is the first to demonstrate that the SMS factors secreted in conditioned medium of senescent MESCs trigger a paracrine mechanism of premature senescence in young cells.

IGF Binding Protein-5 Induces Cell Senescence

Cellular senescence is the complex process of deterioration that drives the aging of an organism, resulting in the progressive loss of organ function and eventually phenotypic aging. Senescent cells undergo irreversible growth arrest, usually by inducing telomere shortening. Alternatively, senescence may also occur prematurely in response to various stress stimuli, such as oxidative stress, DNA damage, or activated oncogenes. Recently, it has been shown that IGF binding protein-5 (IGFBP-5) with the induction of the tumor suppressor p53 is upregulated during cellular senescence. This mechanism mediates interleukin-6/gp130-induced premature senescence in human fibroblasts, irradiation-induced premature senescence in human endothelial cells (ECs), and replicative senescence in human ECs independent of insulin-like growth factor I (IGF-I) and IGF-II. Additionally, a link between IGFBP-5, hyper-coagulation, and inflammation, which occur with age, has been implicated. Thus, IGFBP-5 seems to play decisive roles in controlling cell senescence and cell inflammation. In this review, we describe the accumulating evidence for this role of IGFBP-5 including our new finding.

"Social Life" of Senescent Cells: What Is SASP and Why Study It?

Cellular senescence was first described as a failure of normal human cells to divide indefinitely in culture. Until recently, the emphasis in the study of cell senescence has been focused on the accompanying intracellular processes. The focus of the attention has been on the irreversible growth arrest and two important physiological functions that rely on it: suppression of carcinogenesis due to the proliferation loss of damaged cells, and the acceleration of organism aging due to the deterioration of the tissue repair mechanism with age. However, the advances of the past years have revealed that senescent cells can impact the surrounding tissue microenvironment, and, thus, that the main consequences of senescence are not solely mediated by intracellular alterations. Recent studies have provided evidence that a pool of molecules secreted by senescent cells, including cytokines, chemokines, proteases and growth factors, termed the senescence-associated secretory phenotype (SASP), via autocrine/paracrine pathways can affect neighboring cells. Today it is clear that SASP functionally links cell senescence to various biological processes, such as tissue regeneration and remodeling, embryonic development, inflammation, and tumorigenesis. The present article aims to describe the "social" life of senescent cells: basically, SASP constitution, molecular mechanisms of its regulation, and its functional role.

Impact of lysosomal storage disorders on biology of mesenchymal stem cells: Evidences from in vitro silencing of glucocerebrosidase (GBA) and alpha-galactosidase A (GLA) enzymes

Lysosomal storage disorders (LDS) comprise a group of rare multisystemic diseases resulting from inherited gene mutations that impair lysosomal homeostasis. The most common LSDs, Gaucher disease (GD), and Fabry disease (FD) are caused by deficiencies in the lysosomal glucocerebrosidase (GBA) and alpha-galactosidase A (GLA) enzymes, respectively. Given the systemic nature of enzyme deficiency, we hypothesized that the stem cell compartment of GD and FD patients might be also affected. Among stem cells, mesenchymal stem cells (MSCs) are a commonly investigated population given their role in hematopoiesis and the homeostatic maintenance of many organs and tissues. Since the impairment of MSC functions could pose profound consequences on body physiology, we evaluated whether GBA and GLA silencing could affect the biology of MSCs isolated from bone marrow and amniotic fluid. Those cell populations were chosen given the former's key role in organ physiology and the latter's intriguing potential as an alternative stem cell model for human genetic disease. Our results revealed that GBA and GLA deficiencies prompted cell cycle arrest along with the impairment of autophagic flux and an increase of apoptotic and senescent cell percentages. Moreover, an increase in ataxia-telangiectasia-mutated staining 1 hr after oxidative stress induction and a return to basal level at 48 hr, along with persistent gamma-H2AX staining, indicated that MSCs properly activated DNA repair signaling, though some damages remained unrepaired. Our data therefore suggest that MSCs with reduced GBA or GLA activity are prone to apoptosis and senescence due to impaired autophagy and DNA repair capacity.

Material-induced Senescence (MIS): Fluidity Induces Senescent Type Cell Death of Lung Cancer Cells via Insulin-Like Growth Factor Binding Protein 5

Objective: We propose here material-induced senescence (MIS) as a new therapeutic concept that limits cancer progression by stable cell cycle arrest. This study examined for the first time the effect of material fluidity on cellular senescence in lung carcinoma using poly(ε-caprolactone-co-D, L-lactide) (P(CL-co-DLLA)) with tunable elasticity and fluidity. Methods: The fluidity was varied by chemically crosslinking the polymer networks: the crosslinked P(CL-co-DLLA) shows solid-like properties with a stiffness of 260 kPa, while the non-crosslinked polymer exists in a quasi-liquid state with loss and storage moduli of 33 kPa and 11 kPa, respectively. Results: We found that cancer cells growing on the non-crosslinked, fluidic substrate undergo a non-apoptotic form of cell death and the cell cycle was accumulated in a G0/G1 phase. Next, we investigated the expression of biomarkers that are associated with cancer pathways. The cancer cells on the fluidic substrate expressed several biomarkers associated with senescence such as insulin-like growth factor binding protein 5 (IGFBP5). This result indicates that when cancer cells sense fluidity in their surroundings, the cells express IGFBP5, which in turn triggers the expression of tumor suppressor protein 53 and initiates cell cycle arrest at the G1 phase followed by cellular senescence. Furthermore, the cancer cells on the fluidic substrate maintained their epithelial phenotype, suggesting that the cancer cells do not undergo epithelial to mesenchymal transition. Conclusion: By considering these results as the fundamental information for MIS, our system could be applied to induce senescence in treatment-resistant cancers such as metastatic cancer or cancer stem cells.

Microvesicles as Potential Biomarkers for the Identification of Senescence in Human Mesenchymal Stem Cells

Senescence in human mesenchymal stem cells (MSCs) not only contributes to organism aging and the development of a variety of diseases but also severely impairs their therapeutic properties as a promising cell therapy. Studies searching for efficient biomarkers that represent cellular senescence have attracted much attention; however, no single marker currently provides an accurate cell-free representation of cellular senescence. Here, we studied characteristics of MSC-derived microvesicles (MSC-MVs) that may reflect the senescence in their parental MSCs. We found that senescent late passage (LP) MSCs secreted higher levels of MSC-MVs with smaller size than did early passage (EP) MSCs, and the level of CD105+ MSC-MVs decreased with senescence in the parental MSCs. Also, a substantially weaker ability to promote osteogenesis in MSCs was observed in LP than EP MSC-MVs. Comparative analysis of RNA sequencing showed the same trend of decreasing number of highly-expressed miRNAs with increasing number of passages in both MSCs and MSC-MVs. Most of the highly-expressed genes in LP MSCs and the corresponding MSC-MVs were involved in the regulation of senescence-related diseases, such as Alzheimer's disease. Furthermore, based on the miRNA profiling, transcription factors (TF) and genes regulatory networks of MSC senescence, and the datasets from GEO database, we confirmed that expression of miR-146a-5p in MSC-MVs resembled the senescent state of their parental MSCs. Our findings provide evidence that MSC-MVs are a key factor in the senescence-associated secretory phenotype of MSCs and demonstrate that their integrated characteristics can dynamically reflect the senescence state of MSCs representing a potential biomarker for monitoring MSC senescence.

Redox control of senescence and age-related disease

The signaling networks that drive the aging process, associated functional deterioration, and pathologies has captured the scientific community's attention for decades. While many theories exist to explain the aging process, the production of reactive oxygen species (ROS) provides a signaling link between engagement of cellular senescence and several age-associated pathologies. Cellular senescence has evolved to restrict tumor progression but the accompanying senescence-associated secretory phenotype (SASP) promotes pathogenic pathways. Here, we review known biological theories of aging and how ROS mechanistically control senescence and the aging process. We also describe the redox-regulated signaling networks controlling the SASP and its important role in driving age-related diseases. Finally, we discuss progress in designing therapeutic strategies that manipulate the cellular redox environment to restrict age-associated pathology.

Δ133p53 represses p53-inducible senescence genes and enhances the generation of human induced pluripotent stem cells

p53 functions to induce cellular senescence, which is incompatible with self-renewal of pluripotent stem cells such as induced pluripotent stem cells (iPSC) and embryonic stem cells (ESC). However, p53 also has essential roles in these cells through DNA damage repair for maintaining genomic integrity and high sensitivity to apoptosis for eliminating severely damaged cells. We hypothesized that Δ133p53, a physiological inhibitory p53 isoform, is involved in the balanced regulation of self-renewing capacity, DNA damage repair and apoptosis. We examined 12 lines of human iPSC and their original fibroblasts, as well as three ESC lines, for endogenous protein levels of Δ133p53 and full-length p53 (FL-p53), and mRNA levels of various p53 target genes. While FL-p53 levels in iPSC and ESC widely ranged from below to above those in the fibroblasts, all iPSC and ESC lines expressed elevated levels of Δ133p53. The p53-inducible genes that mediate cellular senescence (p21^WAF1, miR-34a, PAI-1 and IGFBP7), but not those for apoptosis (BAX and PUMA) and DNA damage repair (p53R2), were downregulated in iPSC and ESC. Consistent with these endogenous expression profiles, overexpression of Δ133p53 in human fibroblasts preferentially repressed the p53-inducible senescence mediators and significantly enhanced their reprogramming to iPSC. The iPSC lines derived from Δ133p53-overexpressing fibroblasts formed well-differentiated, benign teratomas in immunodeficient mice and had fewer numbers of somatic mutations than an iPSC derived from p53-knocked-down fibroblasts, suggesting that Δ133p53 overexpression is non- or less oncogenic and mutagenic than total inhibition of p53 activities. Overexpressed Δ133p53 prevented FL-p53 from binding to the regulatory regions of p21^WAF1 and miR-34a promoters, providing a mechanistic basis for its dominant-negative inhibition of a subset of p53 target genes. This study supports the hypothesis that upregulation of Δ133p53 is an endogenous mechanism that facilitates human somatic cells to become self-renewing pluripotent stem cells with maintained apoptotic and DNA repair activities.

Therapeutic interventions for aging: the case of cellular senescence

Organismal aging is a multifactorial process characterized by the onset of degenerative conditions and cancer. One of the key drivers of aging is cellular senescence, a state of irreversible growth arrest induced by many pro-tumorigenic stresses. Senescent cells accumulate late in life and at sites of age-related pathologies, where they contribute to disease onset and progression through complex cell and non-cell autonomous effects. Here, we summarize the mechanisms by which cellular senescence can promote aging, and we offer an extensive description of current potential pharmacological interventions for senescent cells, highlighting limitations and suggesting alternatives.

Umbilical cord-derived mesenchymal stromal cell-conditioned medium exerts in vitro antiaging effects in human fibroblasts

BACKGROUND AIMS

Chronic wounds are a common complication of diabetes. Fibroblast-myofibroblast differentiation is important for wound repair, which is commonly impaired in non-healing wounds, and the underlying mechanisms need to be further elucidated.

METHODS

We used high glucose (HG) to simulated the diabetes microenvironment and explored its effects on the biological features of fibroblasts in vitro.

RESULTS

The results showed that prolonged HG induced senescence in fibroblasts through activation of p21 and p16 in a reactive oxygen species (ROS)-dependent manner, further delayed the viability and migration in fibroblasts and also depressed fibroblast differentiation through the TGF-β/Smad signaling pathway. However, mesenchymal stromal cell-conditioned medium (MSC-CM) counteracts the effects of HG. Treatment of fibroblasts with MSC-CM decreased HG-induced ROS overproduction, ameliorated HG-induced senescence in fibroblasts and reversed the defects in myofibroblast formation. Our results may provide clues for the pathogenesis of chronic wounds and a theoretical basis to develop MSC-CM as an alternative therapeutic method to treatment of chronic wounds.

The secretome of MUSE cells contains factors that may play a role in regulation of stemness, apoptosis and immunomodulation

Mesenchymal stromal cells (MSCs) are a heterogeneous population, which contain several cell phenotypes: mesenchymal stem cells, progenitor cells, fibroblasts and other type of cells. Previously, we identified unique stem cells that we named multilineage-differentiating stress enduring (Muse) cells as one to several percent of MSCs of the bone marrow, adipose tissue and dermis. Among different cell populations in MSCs, Muse cells, positive for pluripotent surface marker SSEA-3, may represent cells responsible for pluripotent-like property of MSCs, since they express pluripotency genes, able to differentiated into triploblastic cells from a single cells and are self-renewable. MSCs release biologically active factors that have profound effects on local cellular dynamics. A thorough examination of MSC secretome seems essential for understanding the physiological functions exerted by these cells in our organism and also for rational cellular therapy design. In this setting, studies on secretome of Muse cells may shed light on pathways that are associated with their specific features. Our findings evidenced that secretomes of MSCs and Muse cells contain factors that regulate extracellular matrix remodeling, ox-redox activities and immune system. Muse cells appear to secrete factors that may preserve their stem cell features, allow survival under stress conditions and may contribute to their immunomodulation capacity. In detail, the proteins belonging to protein kinase A signaling, FXR/RXR activation and LXR/RXR activation pathways may play a role in regulation of Muse stem cell features. These last 2 pathways together with proteins associated with antigen presentation pathway and coagulation system may play a role in immunomodulation.

Insulin-like growth factor binding protein 7 and tissue inhibitor of metalloproteinases-2: differential expression and secretion in human kidney tubule cells

We have characterized the expression and secretion of the acute kidney injury (AKI) biomarkers insulin-like growth factor binding protein 7 (IGFBP7) and tissue inhibitor of metalloproteinases-2 (TIMP-2) in human kidney epithelial cells in primary cell culture and tissue. We established cell culture model systems of primary kidney cells of proximal and distal tubule origin and observed that both proteins are indeed expressed and secreted in both tubule cell types in vitro. However, TIMP-2 is both expressed and secreted preferentially by cells of distal tubule origin, while IGFBP7 is equally expressed across tubule cell types yet preferentially secreted by cells of proximal tubule origin. In human kidney tissue, strong staining of IGFBP7 was seen in the luminal brush-border region of a subset of proximal tubule cells, and TIMP-2 stained intracellularly in distal tubules. Additionally, while some tubular colocalization of both biomarkers was identified with the injury markers kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin, both biomarkers could also be seen alone, suggesting the possibility for differential mechanistic and/or temporal profiles of regulation of these early AKI biomarkers from known markers of injury. Last, an in vitro model of ischemia-reperfusion demonstrated enhancement of secretion of both markers early after reperfusion. This work provides a rationale for further investigation of these markers for their potential role in the pathogenesis of acute kidney injury.

Insulin-Like Growth Factor-Binding Protein-7 as a Biomarker of Diastolic Dysfunction and Functional Capacity in Heart Failure With Preserved Ejection Fraction: Results From the RELAX Trial

OBJECTIVES

This study sought to investigate relationships between insulin-like growth factor-binding protein-7 (IGFBP7) and parameters of diastolic function or functional capacity in patients with heart failure and preserved ejection fraction (HFpEF) who were randomized to receive sildenafil or placebo.

BACKGROUND

IGFBP7 was previously found to be associated with diastolic function in heart failure with reduced ejection fraction, but it is unclear whether these associations are present in HFpEF.

METHODS

At baseline and 24 weeks, IGFBP7, imaging studies, and peak oxygen consumption (Vo2max) were obtained and compared in 160 patients with HFpEF who were randomized to receive sildenafil or placebo.

RESULTS

Patients with supramedian baseline IGFBP7 concentrations were older, had signs of systemic congestion and worse renal function, and had higher concentrations of prognostic heart failure biomarkers including amino-terminal pro-B-type natriuretic peptide (p < 0.05). Higher baseline IGFBP7 was modestly correlated with worse diastolic function: higher E velocity (Spearman correlation [ρ] = 0.40), E/E' (ρ = 0.40), left atrial volume index (ρ = 0.39), and estimated right ventricular systolic pressure (ρ = 0.41; all p < 0.001) and weakly correlated with transmitral E/A (ρ = 0.26; p = 0.006). Notably, change in IGFBP7 was significantly correlated with change in E, E/A, E/E', and right ventricular systolic pressure. Elevated baseline IGFBP7 was associated with lower baseline Vo2max (13.2 vs. 11.1 ml/min/kg; p < 0.001), and change in IGFBP7 was weakly inversely correlated with change in Vo2max (ρ = -0.19; p = 0.01). Subjects receiving sildenafil had a decrease in IGFBP7 over 24 weeks, in contrast to placebo-treated patients (median change in IGFBP7 -1.5 vs. +13.6 ng/ml; p < 0.001).

CONCLUSIONS

In patients with HFpEF, IGFBP7 may be a novel biomarker of diastolic function and exercise capacity.

Secretome of Human Fetal Mesenchymal Stem Cell Ameliorates Replicative Senescen

Autologous mesenchymal stem cells (MSC) are widely used cell source for cell-based tissue repair and regeneration, but replicative senescence and the associated loss of cellular activity during in vitro expansion limit their therapeutic potential. How to preserve or even enhance the proliferation and differentiation ability of MSC from aged donors without genetic modification remains a challenge to meet clinical need. MSC isolated from human fetal tissues (hFMSC) exhibit higher proliferation and differentiation activities even in prolonged in vitro culture, which might be modulated by autocrine/paracrine action. In the present study, we hypothesized that the bioactive factors secreted by hFMSC, collectively named as hFMSC secretome (HFS), could possess beneficial effect on human adult MSC (hAMSC) undergoing replicative senescence, thus promoting their capability of proliferation and differentiation. HFS was prepared by centrifugation of hFMSC conditioned medium, followed by column-based concentration, and the total protein content of the HFS was quantified to standardize treatment concentration. When compared with hAMSC secretome (HAS), HFS treatment significantly reduced senescence associated-β-galactosidase expression and activity (senescence marker) and enhanced cell proliferation and osteogenic differentiation potential of hAMSC in prolonged in vitro culture. Cellular studies revealed concomitant activation of sirt1 and foxo3a in hAMSC after HFS treatment, which was associated with upregulation of p21 and downregulation of bax and p53. The changes of these senescence associated markers suggested that HFS, but not HAS, could ameliorate replicative senescence of hAMSC in vitro. In nude mice, HFS pretreatment restored the osteogenic ability of senescent hAMSC. Tumor xenograft model revealed that HFS did not promote tumor growth. In conclusion, this study suggests that HFS could be an effective and safe method to overcome replicative senescence and facilitate the therapeutic potential of hAMSC.

Engineered Mesenchymal Stem Cells as an Anti-Cancer Trojan Horse

Cell-based gene therapy holds a great promise for the treatment of human malignancy. Among different cells, mesenchymal stem cells (MSCs) are emerging as valuable anti-cancer agents that have the potential to be used to treat a number of different cancer types. They have inherent migratory properties, which allow them to serve as vehicles for delivering effective therapy to isolated tumors and metastases. MSCs have been engineered to express anti-proliferative, pro-apoptotic, and anti-angiogenic agents that specifically target different cancers. Another field of interest is to modify MSCs with the cytokines that activate pro-tumorigenic immunity or to use them as carriers for the traditional chemical compounds that possess the properties of anti-cancer drugs. Although there is still controversy about the exact function of MSCs in the tumor settings, the encouraging results from the preclinical studies of MSC-based gene therapy for a large number of tumors support the initiation of clinical trials.

Positively charged polymers modulate the fate of human mesenchymal stromal cells via ephrinB2/EphB4 signaling

Understanding the mechanisms by which mesenchymal stromal cells (MSCs) interact with the physical properties (e.g. topography, charge, ζ-potential, and contact angle) of polymeric surfaces is essential to design new biomaterials capable of regulating stem cell behavior. The present study investigated the ability of two polymers (pHM1 and pHM3) with different positive surface charge densities to modulate the differentiation of MSCs into osteoblast-like phenotype via cell-cell ephrinB2/EphB4 signaling. Although pHM1 promoted the phosphorylation of EphB4, leading to cell differentiation, pHM3, characterized by a high positive surface charge density, had no significant effect on EphB4 activation or MSCs differentiation. When the MSCs were cultured on pHM1 in the presence of a forward signaling blocking peptide, the osteoblast differentiation was compromised. Our results demonstrated that the ephrinB2/EphB4 interaction was required for MSCs differentiation into an osteoblast-like phenotype and that the presence of a high positive surface charge density altered this interaction.

Senescent endothelial cells: Potential modulators of immunosenescence and ageing

Recent studies have demonstrated that the accumulation of senescent endothelial cells may be the primary cause of cardiovascular diseases. Because of their multifunctional properties, endothelial cells actively take part in stimulating the immune system and inflammation. In addition, ageing is characterized by the progressive deterioration of immune cells and a decline in the activation of the immune response. This results in a loss of the primary function of the immune system, which is eliminating damaged/senescent cells and neutralizing potential sources of harmful inflammatory reactions. In this review, we discuss cellular senescence and the senescence-associated secretory phenotype (SASP) of endothelial cells and summarize the link between endothelial cells and immunosenescence. We describe the possibility that age-related changes in Toll-like receptors (TLRs) and microRNAs can affect the phenotypes of senescent endothelial cells and immune cells via a negative feedback loop aimed at restraining the excessive pro-inflammatory response. This review also addresses the following questions: how do senescent endothelial cells influence ageing or age-related changes in the inflammatory burden; what is the connection between ECs and immunosenescence, and what are the crucial hypothetical pathways linking endothelial cells and the immune system during ageing.

Mesenchymal Stromal Cells Mitigate Experimental Colitis via Insulin-like Growth Factor Binding Protein 7-mediated Immunosuppression

Mesenchymal stromal cells (MSCs) have shown great potential for treating inflammatory bowel disease, which is ameliorated through paracrine cross talk between MSCs and T-cells. Members of the insulin-like growth factor binding protein (IGFBP) family have important immunomodulatory functions in MSCs, but the underlying mechanisms behind these functions have not yet been clearly elucidated. In this study, we investigate whether MSC-produced IGFBP7 is involved in immune modulation using a mouse experimental colitis model. Gene expression profiling revealed that IGFBP7 was highly expressed in MSCs. Consistent with this findings, IGFBP7 knockdown in MSCs significantly decreased their immunomodulatory properties, decreasing the antiproliferative functions of MSCs against T-cells, while also having an effect on the proinflammatory cytokine production of the T-cells. Furthermore, in the mouse experimental colitis model, MSC-derived IGFBP7 ameliorated the clinical and histopathological severity of induced colonic inflammation and also restored the injured gastrointestinal mucosal tissues. In conclusion, IGFBP7 contributes significantly to MSC-mediated immune modulation, as is shown by the ability of IGFBP7 knockdown in MSCs to restore proliferation and cytokine production in T-cells. These results suggest that IGFBP7 may act as a novel MSC-secreted immunomodulatory factor.

Extracellular Matrix Regulation of Stem Cell Behavior

Stem cells hold great promise in treating many diseases either through promoting endogenous cell repair or through direct cell transplants. In order to maximize their potential, understanding the fundamental signals and mechanisms that regulate their behavior is essential. The extracellular matrix (ECM) is one such component involved in mediating stem cell fate. Recent studies have made significant progress in understanding stem cell-ECM interactions. Technological developments have provided greater clarity in how cells may sense and respond to the ECM, in particular the physical properties of the matrix. This review summarizes recent developments, providing illustrative examples of the different modes with which the ECM controls both embryonic and adult stem cell behavior.

Unbiased analysis of senescence associated secretory phenotype (SASP) to identify common components following different genotoxic stresses

Senescent cells secrete senescence-associated secretory phenotype (SASP) proteins to carry out several functions, such as sensitizing surrounding cells to senesce; immunomodulation; impairing or fostering cancer growth; and promoting tissue development. Identifying secreted factors that achieve such tasks is a challenging issue since the profile of secreted proteins depends on genotoxic stress and cell type. Currently, researchers are trying to identify common markers for SASP. The present investigation compared the secretome composition of five different senescent phenotypes in two different cell types: bone marrow and adipose mesenchymal stromal cells (MSC). We induced MSC senescence by oxidative stress, doxorubicin treatment, X-ray irradiation, and replicative exhaustion. We took advantage of LC-MS/MS proteome identification and subsequent gene ontology (GO) evaluation to perform an unbiased analysis (hypothesis free manner) of senescent secretomes. GO analysis allowed us to distribute SASP components into four classes: extracellular matrix/cytoskeleton/cell junctions; metabolic processes; ox-redox factors; and regulators of gene expression. We used Ingenuity Pathway Analysis (IPA) to determine common pathways among the different senescent phenotypes. This investigation, along with identification of eleven proteins that were exclusively expressed in all the analyzed senescent phenotypes, permitted the identification of three key signaling paths: MMP2 - TIMP2; IGFBP3 - PAI-1; and Peroxiredoxin 6 - ERP46 - PARK7 - Cathepsin D - Major vault protein. We suggest that these paths could be involved in the paracrine circuit that induces senescence in neighboring cells and may confer apoptosis resistance to senescent cells.

Secretome profiling of cytokines and growth factors reveals that neuro-glial differentiation is associated with the down-regulation of Chemokine Ligand 2 (MCP-1/CCL2) in amniotic fluid derived-mesenchymal progenitor cells

Secreted cytokines and growth factors play a key role in the modulation of stem cell proliferation, differentiation and survival. To investigate the interplay between the changes in their expression levels, we used the newly characterized human amniotic fluid derived-mesenchymal progenitor MePR-2B cell line differentiated to a neuro-glial phenotype and exploited the very high sensitivity and versatility of magnetic beads-based immunoassays. We found that a sub-set of proteins, including the cytokines IL-6, TNFα, IL-15, IFNγ, IL-8, IL-1ra, MCP-1/CCL2, RANTES and the growth factor PDGFbb, underwent a significant down-regulation following neuro-glial differentiation, whereas the expression levels of IL-12 p70, IL-5, IL-7, bFGF, VEGF and G-CSF were increased. The role of MCP-1/CCL2, previously identified as a regulator of neural progenitor stem cell differentiation, has been further investigated at transcriptional level, revealing that both the chemokine and its receptor are co-expressed in MePR-2B cells and that are regulated upon differentiation, suggesting the presence of an autocrine and paracrine loop in differentiating cells. Moreover, we demonstrated that exogenous CCL2 is capable to affect neuro-glial differentiation in MePR-2B cells, thus providing novel evidences for the potential involvement of chemokine-mediated signaling in progenitor/stem cells differentiation processes and fate specification.

Fibroblast growth factor-23 induces cellular senescence in human mesenchymal stem cells from skeletal muscle

Although muscle wasting and/or degeneration are prevalent in patients with chronic kidney disease, it remains unknown whether FGF-23 influences muscle homeostasis and regeneration. Mesenchymal stem cells (MSCs) in skeletal muscle are distinct from satellite cells and have a known association with muscle degeneration. In this study we sought to investigate the effects of FGF-23 on MSCs isolated from human skeletal muscle in vitro. The MSCs expressed FGF receptors (1 through 4) and angiotensin-II type 1 receptor, but no traces of the Klotho gene were detected. MSCs and satellite cells were treated with FGF-23 and angiotensin-II for 48 h. Treatment with FGF-23 significantly decreased the number of MSCs compared to controls, while treatment with angiotensin-II did not. FGF-23 and angiotensin-II both left the cell counts of the satellite cells unchanged. The FGF-23-treated MSCs exhibited the senescent phenotype, as judged by senescence-associated β-galactosidase assay, cell morphology, and increased expression of p53 and p21 in western blot analysis. FGF-23 also significantly altered the gene expression of oxidative stress regulators in the cells. In conclusion, FGF-23 induced premature senescence in MSCs from skeletal muscle via the p53/p21/oxidative-stress pathway. The interaction between the MSCs and FGF-23 may play a key role in the impaired muscle reparative mechanisms of chronic kidney disease.