Sublethal heat shock induces premature senescence rather than apoptosis in human mesenchymal stem cells

Therapeutic applications of mesenchymal/medicinal stem/signaling cells preconditioned with external factors: Are there more efficient approaches to utilize their regenerative potential?

Mesenchymal/medicinal stem/signaling cells (MSCs) have emerged as a promising treatment option for various disorders. However, the donor's age, advanced stage of disease, and prolonged in vitro expansion often diminish the innate regenerative potential of MSCs. Besides that, the absence of MSCs' comprehensive "pre-admission testing" can result in the injection of cells with reduced viability and function, which may negatively affect the overall outcome of MSC-based therapies. It is, therefore, essential to develop effective strategies to improve the impaired biological performance of MSCs. This review focuses on the comprehensive characterization of various methods of external MSCs stimulation (hypoxia, heat shock, caloric restriction, acidosis, 3D culture, and application of extracellular matrix) that augment their medicinal potential. To emphasize the significance of MSCs priming, we summarize the effects of individual and combined preconditioning approaches, highlighting their impact on MSCs' response to either physiological or pathological conditions. We further investigate the synergic action of exogenous factors to maximize MSCs' therapeutic potential. Not to omit the field of tissue engineering, the application of pretreated MSCs seeded on scaffolds is discussed as well.

Mild photothermal therapy assist in promoting bone repair: Related mechanism and materials

Achieving precision treatment in bone tissue engineering (BTE) remains a challenge. Photothermal therapy (PTT), as a form of precision therapy, has been extensively investigated for its safety and efficacy. It has demonstrated significant potential in the treatment of orthopedic diseases such as bone tumors, postoperative infections and osteoarthritis. However, the high temperatures associated with PTT can lead to certain limitations and drawbacks. In recent years, researchers have explored the use of biomaterials for mild photothermal therapy (MPT), which offers a promising approach for addressing these limitations. This review provides a comprehensive overview of the mechanisms underlying MPT and presents a compilation of photothermal agents and their utilization strategies for bone tissue repair. Additionally, the paper discusses the future prospects of MPT-assisted bone tissue regeneration, aiming to provide insights and recommendations for optimizing material design in this field.

Oncogene-Induced Senescence Is a Crucial Antitumor Defense Mechanism of Human Endometrial Stromal Cells

Being the major cellular component of highly dynamic tissue, endometrial stromal cells (EnSCs) are exposed to cycles of proliferation upon hormonal stimulation, which might pose risks for the accumulation of mutations and malignization. However, endometrial stromal tumors are rare and uncommon. The present study uncovered defense mechanisms that might underlie the resistance of EnSCs against oncogenic transformation. All experiments were performed in vitro using the following methods: FACS, WB, RT-PCR, IF, molecular cloning, lentiviral transduction, and CRISPR/Cas9 genome editing. We revealed that the expression of the mutant HRASG12V leads to EnSC senescence. We experimentally confirmed the inability of HRASG12V-expressing EnSCs to bypass senescence and resume proliferation, even upon estrogen stimulation. At the molecular level, the induction of oncogene-induced senescence (OIS) was accompanied by activation of the MEK/ERK, PI3K/AKT, p53/p21WAF/CIP/Rb, and p38/p16INK4a/Rb pathways; however, inhibiting either pathway did not prevent cell cycle arrest. PTEN loss was established as an additional feature of HRASG12V-induced senescence in EnSCs. Using CRISPR-Cas9-mediated PTEN knockout, we identified PTEN loss-induced senescence as a reserve molecular mechanism to prevent the transformation of HRASG12V-expressing EnSCs. The present study highlights oncogene-induced senescence as an antitumor defense mechanism of EnSCs controlled by multiple backup molecular pathways.

Rejuvenation of Senescent Mesenchymal Stem Cells to Prevent Age-Related Changes in Synovial Joints

Mesenchymal/medicinal stem/signaling cells (MSCs), well known for regenerative potential, have been involved in hundreds of clinical trials. Even if equipped with reparative properties, aging significantly decreases their biological activity, representing a major challenge for MSC-based therapies. Age-related joint diseases, such as osteoarthritis, are associated with the accumulation of senescent cells, including synovial MSCs. An impaired ability of MSCs to self-renew and differentiate is one of the main contributors to the human aging process. Moreover, senescent MSCs (sMSCs) are characterized by the senescence-messaging secretome (SMS), which is typically manifested by the release of molecules with an adverse effect. Many factors, from genetic and metabolic pathways to environmental stressors, participate in the regulation of the senescent phenotype of MSCs. To better understand cellular senescence in MSCs, this review discusses the characteristics of sMSCs, their role in cartilage and synovial joint aging, and current rejuvenation approaches to delay/reverse age-related pathological changes, providing evidence from in vivo experiments as well.

A novel feature for monitoring the enzymatic harvesting process of adherent cell cultures based on lens-free imaging

Adherent cell cultures are often dissociated from their culture vessel (and each other) through enzymatic harvesting, where the detachment response is monitored by an operator. However, this approach is lacking standardisation and reproducibility, and prolonged exposure or too high concentrations can affect the cell's viability and differentiation potential. Quantitative monitoring systems are required to characterise the cell detachment response and objectively determine the optimal time-point to inhibit the enzymatic reaction. State-of-the-art methodologies rely on bulky imaging systems and/or features (e.g. circularity) that lack robustness. In this study, lens-free imaging (LFI) technology was used to develop a novel cell detachment feature. Seven different donors were cultured and subsequently harvested with a (diluted) enzymatic harvesting solution after 3, 5 and 7 days of culture. Cell detachment was captured with the LFI set-up over a period of 20 min (every 20 s) and by optimising the reconstruction of the LFI intensity images, a new feature could be identified. Bright regions in the intensity image were identified as detaching cells and using image analysis, a method was developed to automatically extract this feature, defined as the percentage of detached cell regions. Next, the method was quantitatively and qualitatively validated on a diverse set of images. Average absolute error values of 1.49%, 1.34% and 1.97% were obtained for medium to high density and overconfluent cultures, respectively. The detachment response was quantified for all conditions and the optimal time for enzyme inhibition was reached when approximately 92.5% of the cells were detached. On average, inhibition times of 9.6-11.1 and 16.2-17.2 min were obtained for medium to high density and overconfluent cultures, respectively. In general, overconfluent cultures detached much slower, while their detachment rate was also decreased by the diluted harvesting solution. Moreover, several donors exhibited similar trends in cell detachment behaviour, with two clear outliers. Using the novel feature, measurements can be performed with an increased robustness, while the compact LFI design could pave the way for in situ monitoring in a variety of culture vessels, including bioreactors.

Heat-Induced Proteotoxic Stress Response in Placenta-Derived Stem Cells (PDSCs) Is Mediated through HSPA1A and HSPA1B with a Potential Higher Role for HSPA1B

Placenta-derived stem cells (PDSCs), due to unique traits such as mesenchymal and embryonic characteristics and the absence of ethical constraints, are in a clinically and therapeutically advantageous position. To aid in stemness maintenance, counter pathophysiological stresses, and withstand post-differentiation challenges, stem cells require elevated protein synthesis and consequently augmented proteostasis. Stem cells exhibit source-specific proteostasis traits, making it imperative to study them individually from different sources. These studies have implications for understanding stem cell biology and exploitation in the augmentation of therapeutic applications. Here, we aim to identify the primary determinants of proteotoxic stress response in PDSCs. We generated heat-induced dose-responsive proteotoxic stress models of three stem cell types: placental origin cells, the placenta-derived mesenchymal stem cells (pMSCs), maternal origin cells, the decidua parietalis mesenchymal stem cells (DPMSCs), and the maternal–fetal interface cells, decidua basalis mesenchymal stem cells (DBMSCs), and measured stress induction through biochemical and cell proliferation assays. RT-PCR array analysis of 84 genes involved in protein folding and protein quality control led to the identification of Hsp70 members HSPA1A and HSPA1B as the prominent ones among 17 significantly expressed genes and with further analysis at the protein level through Western blotting. A kinetic analysis of HSPA1A and HSPA1B gene and protein expression allowed a time series evaluation of stress response. As identified by protein expression, an active stress response is in play even at 24 h. More prominent differences in expression between the two homologs are detected at the translational level, alluding to a potential higher requirement for HSPA1B during proteotoxic stress response in PDSCs.

Monovalent ions and stress-induced senescence in human mesenchymal endometrial stem/stromal cells

Monovalent ions are involved in growth, proliferation, differentiation of cells as well as in their death. This work concerns the ion homeostasis during senescence induction in human mesenchymal endometrium stem/stromal cells (hMESCs): hMESCs subjected to oxidative stress (sublethal pulse of H₂O₂) enter the premature senescence accompanied by persistent DNA damage, irreversible cell cycle arrest, increased expression of the cell cycle inhibitors (p53, p21) cell hypertrophy, enhanced β-galactosidase activity. Using flame photometry to estimate K⁺, Na⁺ content and Rb⁺ (K⁺) fluxes we found that during the senescence development in stress-induced hMESCs, Na⁺/K⁺pump-mediated K⁺ fluxes are enhanced due to the increased Na⁺ content in senescent cells, while ouabain-resistant K⁺ fluxes remain unchanged. Senescence progression is accompanied by a peculiar decrease in the K⁺ content in cells from 800-900 to 500-600 µmol/g. Since cardiac glycosides are offered as selective agents for eliminating senescent cells, we investigated the effect of ouabain on ion homeostasis and viability of hMESCs and found that in both proliferating and senescent hMESCs, ouabain (1 nM-1 µM) inhibited pump-mediated K⁺ transport (ID₅₀ 5 × 10^-8 M), decreased cell K⁺/Na⁺ ratio to 0.1-0.2, however did not induce apoptosis. Comparison of the effect of ouabain on hMESCs with the literature data on the selective cytotoxic effect of cardiac glycosides on senescent or cancer cells suggests the ion pump blockade and intracellular K⁺ depletion should be synergized with target apoptotic signal to induce the cell death.

Antioxidants Attenuate Heat Shock Induced Premature Senescence of Bovine Mesenchymal Stem Cells

Mesenchymal stem cells (MSC) have many roles that are important for the body's proper functioning. When the MSC pool is damaged, it is often correlated with impaired development or health of the organism. MSC are known for their anti-inflammatory, immunomodulatory and trophic characteristics that play an important role in the physiological homeostasis of many tissues. Heat shock impairs MSC capacity by inducing the generation of reactive oxygen species and mitochondrial dysfunction, which, in turn, send the cells into a state of premature senescence. Here, we pre-exposed MSC to melatonin, resveratrol, or curcumin, which are natural antioxidative compounds, and tested the protective effects of these substances from oxidative stress and aging. Our data showed that pre-exposure of MSC to antioxidants decreased reactive oxygen species while mitochondrial damage remained high. Additionally, although the proliferation of the cells was slow, antioxidants protected the cells from premature senescence, and subsequent cytokine release was prevented. We conclude that while elevated temperatures directly cause mitochondrial damage, senescence is induced by elevated ROS levels. We suggest that heat shock alters cell and tissue homeostasis by several independent mechanisms; however, reducing tissue senescence will reduce damage and provide a pathway to overcome physiological challenges in animals.

The involvement of ERK1/2 and p38 MAPK in the premature senescence of melanocytes induced by H2O2 through a p53-independent p21 pathway

BACKGROUND

The pathogenesis of vitiligo is still unknown and oxidative stress is an important factor that can damage or incapacitate melanocytes.

OBJECTIVE

To investigate the role of oxidative stress in the premature senescence of melanocytes and their transfer of melanosomes.

METHODS

Cultured human melanocytes were treated with H₂O₂ after which cell viability and apoptosis were assessed. We investigated whether exposure to H₂O₂ induces premature senescence. RNA sequencing was used to screen aging-related signaling pathways. The expression of dendritic regulatory proteins, adhesion molecules and cell cytoskeletal proteins, as well as melanosome distribution were characterized. The ROS scavenger NAC was used to study the role of ROS in cell senescence and in melanosome transfer.

RESULTS

Cell viability decreased progressively and cell apoptosis increased after treatment with H₂O₂. H₂O₂ treatment tended to induce premature senescence in melanocytes through a p53-independent p21 pathway. RNA sequencing analysis showed that H₂O₂ treatment induced the differential expression of MAPK signaling pathway components. Western blotting and qRT-PCR confirmed that H₂O₂ treatment increased the phosphorylation of ERK1/2 and p38 MAPK, which are involved in inducing the senescence of melanocytes, but not JNK. The expression of cell cytoskeleton and adhesion molecules decreased after H₂O₂ treatment. p21 siRNA treatment reversed these changes. Treatment with NAC improved the premature senescence and the impaired melanosome transfer induced by H₂O₂.

CONCLUSION

H₂O₂ increases ROS levels, which activates the ERK1/2 and p38 MAPK pathways to induce the premature senescence of melanocytes through p21 via a p53-independent pathway and consequently disrupts melanosome transfer.

Outcomes of Deferoxamine Action on H2O2-Induced Growth Inhibition and Senescence Progression of Human Endometrial Stem Cells

Mesenchymal stem cells (MSCs) are broadly applied in regenerative therapy to replace cells that are lost or impaired during disease. The low survival rate of MSCs after transplantation is one of the major limitations heavily influencing the success of the therapy. Unfavorable microenvironments with inflammation and oxidative stress in the damaged regions contribute to MSCs loss. Most of the strategies developed to overcome this obstacle are aimed to prevent stress-induced apoptosis, with little attention paid to senescence-another common stress reaction of MSCs. Here, we proposed the strategy to prevent oxidative stress-induced senescence of human endometrial stem cells (hMESCs) based on deferoxamine (DFO) application. DFO prevented DNA damage and stress-induced senescence of hMESCs, as evidenced by reduced levels of reactive oxygen species, lipofuscin, cyclin D1, decreased SA-β-Gal activity, and improved mitochondrial function. Additionally, DFO caused accumulation of HIF-1α, which may contribute to the survival of H2O2-treated cells. Importantly, cells that escaped senescence due to DFO preconditioning preserved all the properties of the initial hMESCs. Therefore, once protecting cells from oxidative damage, DFO did not alter further hMESCs functioning. The data obtained may become the important prerequisite for development of a new strategy in regenerative therapy based on MSCs preconditioning using DFO.

Hyperthermia induced disruption of mechanical balance leads to G1 arrest and senescence in cells

Human body temperature limits below 40°C during heat stroke or fever. The implications of prolonged exposure to the physiologically relevant temperature (40°C) on cellular mechanobiology is poorly understood. Here, we have examined the effects of heat stress (40°C for 72 h incubation) in human lung adenocarcinoma (A549), mouse melanoma (B16F10), and non-cancerous mouse origin adipose tissue cells (L929). Hyperthermia increased the level of ROS, γ-H2AX and HSP70 and decreased mitochondrial membrane potential in the cells. Heat stress impaired cell division, caused G1 arrest, induced cellular senescence, and apoptosis in all the tested cell lines. The cells incubated at 40°C for 72 h displayed a significant decrease in the f-actin level and cellular traction as compared with cells incubated at 37°C. Also, the cells showed a larger focal adhesion area and stronger adhesion at 40°C than at 37°C. The mitotic cells at 40°C were unable to round up properly and displayed retracting actin stress fibers. Hyperthermia down-regulated HDAC6, increased the acetylation level of microtubules, and perturbed the chromosome alignment in the mitotic cells at 40°C. Overexpression of HDAC6 rescued the cells from the G1 arrest and reduced the delay in cell rounding at 40°C suggesting a crucial role of HDAC6 in hyperthermia mediated responses. This study elucidates the significant role of cellular traction, focal adhesions, and cytoskeletal networks in mitotic cell rounding and chromosomal misalignment. It also highlights the significance of HDAC6 in heat-evoked senile cellular responses.

Tuning Thermal Dosage to Facilitate Mesenchymal Stem Cell Osteogenesis in Pro-Inflammatory Environment

Mesenchymal stem cells (MSCs) are multipotent cells that can replicate and differentiate to different lineages, potentiating their use as integral components in regenerated mesenchymal tissues. Our previous work and other studies have indicated that mild heat shock enhances osteogenesis. However, the influence of pro-inflammatory cytokines on osteogenic differentiation during mildly elevated temperature conditions remains to be fully explored. In this study, human MSCs (hMSCs) were cultured with tumor necrosis factor-alpha (TNF-α), an important mediator of the acute phase response, and interleukin-6 (IL-6) which plays a role in damaging chronic inflammation, then heat shocked at 39 °C in varying frequencies-1 h per week (low), 1 h every other day (mild), and 1 h intervals three times per day every other day (high). DNA data showed that periodic mild heating inhibited suppression of cell growth caused by cytokines and induced maximal proliferation of hMSCs while high heating had the opposite effect. Quantitative osteogenesis assays show significantly higher levels of alkaline phosphatase (ALP) activity and calcium precipitation in osteogenic cultures following mild heating compared to low heating or nonheated controls. These results demonstrate that periodic mild hyperthermia may be used to facilitate bone regeneration using hMSCs, and therefore may influence the design of heat-based therapies in vivo.

Regional Hyperthermia Enhances Mesenchymal Stem Cell Recruitment to Tumor Stroma: Implications for Mesenchymal Stem Cell-Based Tumor Therapy

The tropism of mesenchymal stem cells (MSCs) for tumors forms the basis for their use as delivery vehicles for the tumor-specific transport of therapeutic genes, such as the theranostic sodium iodide symporter (NIS). Hyperthermia is used as an adjuvant for various tumor therapies and has been proposed to enhance leukocyte recruitment. Here, we describe the enhanced recruitment of adoptively applied NIS-expressing MSCs to tumors in response to regional hyperthermia. Hyperthermia (41°C, 1 h) of human hepatocellular carcinoma cells (HuH7) led to transiently increased production of immunomodulatory factors. MSCs showed enhanced chemotaxis to supernatants derived from heat-treated cells in a 3D live-cell tracking assay and was validated in vivo in subcutaneous HuH7 mouse xenografts. Cytomegalovirus (CMV)-NIS-MSCs were applied 6-48 h after or 24-48 h before hyperthermia treatment. Using ¹²³I-scintigraphy, thermo-stimulation (41°C, 1 h) 24 h after CMV-NIS-MSC injection resulted in a significantly increased uptake of ¹²³I in heat-treated tumors compared with controls. Immunohistochemical staining and real-time PCR confirmed tumor-selective, temperature-dependent MSC migration. Therapeutic efficacy was significantly enhanced by combining CMV-NIS-MSC-mediated ¹³¹I therapy with regional hyperthermia. We demonstrate here for the first time that hyperthermia can significantly boost tumoral MSC recruitment, thereby significantly enhancing therapeutic efficacy of MSC-mediated NIS gene therapy.

A comparative study on the cellular stressors in mesenchymal stem cells (MSCs) and pancreatic β-cells under hyperglycemic milieu

β-cell dysfunction is a critical determinant for both type 1 diabetes and type 2 diabetes and β-cells are shown to be highly susceptible to cellular stressors. Mesenchymal stem cells (MSCs) on the other hand are known to have immunomodulatory potential and preferred in clinical applications. However, there is paucity of a comparative study on these cells in relation to several cellular stressors in response to hyperglycemia and this forms the rationale for the present study. INS1 β-cells and MSCs were subjected to high-glucose treatment without and with Metformin, Lactoferrin, or TUDCA and assessed for stress signaling alterations using gene expression, protein expression, as well as functional read-outs. Compared to the untreated control cells, INS1 β-cells or MSCs treated with high glucose showed significant increase in mRNA expressions of ER stress, senescence, and proinflammation. This was accompanied by increased miR146a target genes and decreased levels of SIRT1, NRF2, and miR146a in both the cell types. Consistent with the mRNA results, protein expression levels do reflect the same alterations. Notably, the alterations are relatively less extent in MSCs compared to INS1 β-cells. Interestingly, three different agents, viz., Metformin, Lactoferrin, or TUDCA, were found to overcome the high glucose-induced cellular stresses in a concerted and inter-linked way and restored the proliferation and migration capacity in MSCs as well as normalized the glucose-stimulated insulin secretion in INS1 β-cells. While our study gives a directionality for potential supplementation of metformin/lactoferrin/TUDCA in optimization protocols of MSCs, we suggest that in vitro preconditioning of MSCs with such factors should be further explored with in-depth investigations to harness and enhance the therapeutic capacity/potential of MSCs.

Heat Shock Alters Mesenchymal Stem Cell Identity and Induces Premature Senescence

Heat stress can have a serious impact on the health of both humans and animals. A major question is how heat stress affects normal development and differentiation at both the cellular and the organism levels. Here we use an in vitro experimental system to address how heat shock treatment influences the properties of bovine mesenchymal stem cells (MSCs)—multipotent progenitor cells—which are found in most tissues. Because cattle are sensitive to harsh external temperatures, studying the effects of heat shock on MSCs provides a unique platform to address cellular stress in a physiologically relevant model organism. Following isolation and characterization of MSCs from the cow’s umbilical cord, heat shock was induced either as a pulse (1 h) or continuously (3 days), and consequent effects on MSCs were characterized. Heat shock induced extensive phenotypic changes in MSCs and dramatically curtailed their capacity to proliferate and differentiate. These changes were associated with a partial arrest in the G1/S or G2/M checkpoints. Furthermore, MSCs lost their ability to resolve the inflammatory response of RAW macrophages in coculture. A possible explanation for this loss of function is the accumulation of reactive oxygen species and malfunction of the mitochondria in the treated cells. Heat shock treatments resulted in stress-induced premature senescence, affecting the MSCs’ ability to proliferate properly for many cell passages to follow. Exposure to elevated external temperatures leads to mitochondrial damage and oxidative stress, which in turn conveys critical changes in the proliferation, differentiation, and immunomodulatory phenotype of heat-stressed MSCs. A better understanding of the effect of heat shock on humans and animals may result in important health and economic benefits.

Three-Dimensional Compaction Switches Stress Response Programs and Enhances Therapeutic Efficacy of Endometrial Mesenchymal Stem/Stromal Cells

Mesenchymal stem cells are currently tested as a promising tool for the treatment of a wide range of human diseases. Enhanced therapeutic potential of spheroids formed from these cells has been proved in numerous studies, however, the fundamental basics of this effect are still being discussed. In this work, we showed that endometrial mesenchymal stem/stromal cells (eMSCs) assembled in spheroids possess a higher therapeutic efficacy compared to cells grown in monolayer in the treatment of the defects that are non-specific for eMSC tissue origin – skin wounds. With the purpose to elucidate the possible causes of superior spheroid potency, we compared the tolerance of eMSC cultivated in spheres and monolayer to the stress insults. Using genetically encoded hydrogen peroxide biosensor HyPer, we showed that three-dimensional configuration (3D) helped to shield the inner cell layers of spheroid from the external H₂O₂-induced oxidative stress. However, the viability of oxidatively damaged eMSCs in spheroids appeared to be much lower than that of monolayer cells. An extensive analysis, which included administration of heat shock and irradiation stress, revealed that cells in spheroids damaged by stress factors activate the apoptosis program, while in monolayer cells stress-induced premature senescence is developed. We found that basal down-regulation of anti-apoptotic and autophagy-related genes provides the possible molecular basis of the high commitment of eMSCs cultured in 3D to apoptosis. We conclude that predisposition to apoptosis provides the programmed elimination of damaged cells and contributes to the transplant safety of spheroids. In addition, to investigate the role of paracrine secretion in the wound healing potency of spheroids, we exploited the in vitro wound model (scratch assay) and found that culture medium conditioned by eMSC spheroids accelerates the migration of adherent cells. We showed that 3D eMSCs upregulate transcriptional activator, hypoxia-inducible factor (HIF)-1, and secret ten-fold more HIF-1-inducible pro-angiogenic factor VEGF (vascular endothelial growth factor) than monolayer cells. Taken together, these findings indicate that enhanced secretory activity can promote wound healing potential of eMSC spheroids and that cultivation in the 3D cell environment alters eMSC vital programs and therapeutic efficacy.

Involvement of CDKN1A (p21) in cellular senescence in response to heat and irradiation stress during preimplantation development

This study examined the role of cyclin-dependent kinase inhibitor 1a (CDK1A, p21) in response to exogenous stressors during mouse preimplantation embryo development. CDKN1A knockdown (KD) one-cell zygotes were exposed to 39 °C heat stress (HS) for 4 days or irradiated by 1 (1-Gy) or 3 (3-Gy) Gy X-rays, and their developmental competence and gene expression were compared with control embryos. CDKN1A KD and HS did not influence early cleavage or subsequent embryonic development; however, HS delayed cavitation and induced elevated Cdkn1a expression in control embryos. Exposure to 1- or 3-Gy had no effect on development to the morula stage; however, a significant number of morulae failed to develop to the blastocyst stage. Interestingly, under the 1-Gy condition, the blastocyst rate of CDKN1A KD embryos (77.7%) was significantly higher than that of the controls (44.4%). In summary, exposure to cellular stressors resulted in the upregulation of Cdkn1a in embryos exposed to HS or X-ray irradiation, particularly in response to heat stress or low-dose X-ray irradiation, and depleting Cdkn1a mRNA alleviated cell cycle arrest. These findings suggest that CDKN1A plays a vital role in cellular senescence during preimplantation embryo development.

Dual Role of Autophagy in Regulation of Mesenchymal Stem Cell Senescence

During their development and overall life, mesenchymal stem cells (MSCs) encounter a plethora of internal and external stress signals and therefore, they need to put in action homeostatic changes in order to face these stresses. To this aim, similar to other mammalian cells, MSCs are endowed with two crucial biological responses, autophagy and senescence. Sharing of a number of stimuli like shrinkage of telomeres, oncogenic and oxidative stress, and DNA damage, suggest an intriguingly close relationship between autophagy and senescence. Autophagy is at first reported to suppress MSC senescence by clearing injured cytoplasmic organelles and impaired macromolecules, yet recent investigations also showed that autophagy can promote MSC senescence by inducing the production of senescence-associated secretory proteins (SASP). These apparently contrary contributions of autophagy may mirror an intricate image of autophagic regulation on MSC senescence. We here tackle the pro-senescence and anti-senescence roles of autophagy in MSCs while concentrating on some possible mechanistic explanations of such an intricate liaison. Clarifying the autophagy/senescence relationship in MSCs will help the development of more effective and safer therapeutic strategies.

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.

Optimization of lentiviral transduction parameters and its application for CRISPR-based secretome modification of human endometrial mesenchymal stem cells

Mesenchymal stem cells (MSCs) hold a great promise for successful development of regenerative medicine. Among the plenty of uncovered MSCs sources, desquamated endometrium collected from the menstrual blood probably remains the most accessible. Though numerous studies have been published on human endometrium-derived mesenchymal stem cells (hMESCs) properties in the past years, there are only a few data regarding their genetic modulation. Moreover, there is a lack of information about the fate of the transduced hMESCs. The present study aimed to optimize hMESCs transduction parameters and apply Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technology for genome and secretome modification. The fate of hMESCs transduced either in presence of polybrene (Pb) or protamine sulfate (Ps) was assessed by alterations in CD expression profile, growth rate, cell size, migration capability, osteogenic, adipogenic, and decidual differential potentials. Here, we postulated that the use of Ps for hMESCs genetic manipulations is preferable, as it has no impact on the stem-cell properties, whereas Pb application is undesirable, as it induces cellular senescence. Plasminogen activator inhibitor-1 was selected for further targeted hMESCs genome and secretome modification using CRISPR/Cas9 systems. The obtained data provide optimized transduction scheme for hMESCs and verification of its effectiveness by successful hMESCs genome editing via CRISPR/Cas9 technology.

High doses of synthetic antioxidants induce premature senescence in cultivated mesenchymal stem cells

Stress-induced premature senescence program is known to be activated in cells by various genotoxic stressors, and oxidative stress is considered to be the main of those. To this end, many studies discover antioxidants as protective anti-aging agents. In the current study, we examined the effects of different antioxidants (Tempol, resveratrol, NAC, DPI) on the mesenchymal stem cells maintained in normal physiological conditions. We used high, but non-cytotoxic antioxidant doses which are widely used in laboratory practice to protect cells from oxidative damage. We show that these substances induce reversible block of cell proliferation and do not cause any genotoxic effects when applied to the quiescent cells. However, the same doses of the same substances, when applied to the proliferating cells, can induce irreversible cell cycle arrest, DNA strand breaks accumulation and DNA damage response activation. As a consequence, antioxidant-induced DNA damage results in the stress-induced premature senescence program activation. We conclude that high doses of antioxidants, when applied to the proliferating cells that maintain physiological levels of reactive oxygen species, can cause DNA damage and induce premature senescence which suggests to re-estimate believed unconditional anti-aging antioxidant properties.

Quiescent Human Mesenchymal Stem Cells Are More Resistant to Heat Stress than Cycling Cells

Quiescence is the prevailing state of many cell types under homeostatic conditions. Yet, surprisingly, little is known about how quiescent cells respond to environmental challenges. The aim of the present study is to compare stress responses of cycling and quiescent mesenchymal stem cells (MSC). Human endometrial mesenchymal cells (eMSС) were employed as adult stem cells. eMSC quiescence was modeled by serum starvation. Sublethal heat shock (HS) was used as a stress factor. Both quiescent and cycling cells were heated at 45°C for 30 min and then returned to standard culture conditions for their recovery. HS response was monitored by DNA damage response, stress-induced premature senescence (SIPS), cell proliferation activity, and oxidative metabolism. It has been found that quiescent cells repair DNA more rapidly, resume proliferation, and undergo SIPS less than proliferating cells. HS-enforced ROS production in heated cycling cells was accompanied with increased expression of genes regulating redox-active proteins. Quiescent cells exposed to HS did not intensify the ROS production, and genes involved in antioxidant defense were mostly silent. Altogether, the results have shown that quiescent cells are more resistant to heat stress than cycling cells. Next-generation sequencing (NGS) demonstrates that HS-survived cells retain differentiation capacity and do not exhibit signs of spontaneous transformation.

p53-NF-κB Crosstalk in Febrile Temperature-Treated Human Umbilical Cord-Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are successful for their therapeutic application in immune and inflammatory contexts due to their anti-inflammatory, trophic, and immunomodulatory roles. However, though MSCs have the potential to provide regenerative treatment toward a wide range of devastating diseases, massive cell death of transplanted MSCs remains an obstacle to overcome. The relation between MSCs and inflammation is multifactorial and challenging to comprehend. Fever is a critical component of the inflamed microenvironment. Also, the choice of MSC source could be critical in determining the fate of transplanted cells under stress conditions. Here we investigated the thermosensitivity of Wharton's jelly MSCs (WJ-MSCs) to elevated temperature in the physiological fever range. We explored the effect of febrile range temperature on morphology, viability, proliferation kinetics, and cell cycle status of WJ-MSCs. WJ-MSCs adopted a flattened morphology at 40°C, and our data from proliferation kinetics study using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and apoptosis assays showed that WJ-MSCs had reduced proliferation and viability at 40°C compared with control cultures. There was also a G0/G1 cell cycle arrest, which was further confirmed by messenger RNA (mRNA) levels of genes specific for different stages of cell cycle. On evaluating p53 status, we observed an increase in p53 protein expression and its nuclear localization in WJ-MSCs exposed to 40°C. Its downstream effector p21 too was upregulated. Moreover, this temperature-induced p53 induction was inhibited on exposure to 40°C in the presence of NF-κB pathway inhibitor, pyrrolidinedithiocarbamate (PDTC) or endonuclease-prepared small interfering RNA (esiRNA) targeting p65. Febrile temperature exposure did not affect the senescence status of WJ-MSCs. The MSC-specific surface antigen profile at 40°C was similar to control WJ-MSCs. Our findings suggest that under febrile temperature stress conditions, WJ-MSCs exhibit G0/G1 cell cycle arrest and reduction in viable cell count, while retaining their basic characteristics, with an underlying interplay of p53 and NF-κB pathway.

Cytogenetic and Transcriptomic Analysis of Human Endometrial MSC Retaining Proliferative Activity after Sublethal Heat Shock

Temperature is an important exogenous factor capable of leading to irreversible processes in the vital activity of cells. However, the long-term effects of heat shock (HS) on mesenchymal stromal cells (MSC) remain unstudied. We investigated the karyotype and DNA repair drivers and pathways in the human endometrium MSC (eMSC) survived progeny at passage 6 after sublethal heat stress (sublethal heat stress survived progeny (SHS-SP)). G-banding revealed an outbreak of random karyotype instability caused by chromosome breakages and aneuploidy. Molecular karyotyping confirmed the random nature of this instability. Transcriptome analysis found homologous recombination (HR) deficiency that most likely originated from the low thermostability of the AT-rich HR driving genes. SHS-SP protection from transformation is provided presumably by low oncogene expression maintained by tight co-regulation between thermosensitive HR drivers BRCA, ATM, ATR, and RAD51 (decreasing expression after SHS), and oncogenes mTOR, MDM2, KRAS, and EGFR. The cancer-related transcriptomic features previously identified in hTERT transformed MSC in culture were not found in SHS-SP, suggesting no traits of malignancy in them. The entrance of SHS-SP into replicative senescence after 25 passages confirms their mortality and absence of transformation features. Overall, our data indicate that SHS may trigger non-tumorigenic karyotypic instability due to HR deficiency and decrease of oncogene expression in progeny of SHS-survived MSC. These data can be helpful for the development of new therapeutic approaches in personalized medicine.

Molecular Genetic Analysis of Human Endometrial Mesenchymal Stem Cells That Survived Sublethal Heat Shock

High temperature is a critical environmental and personal factor. Although heat shock is a well-studied biological phenomenon, hyperthermia response of stem cells is poorly understood. Previously, we demonstrated that sublethal heat shock induced premature senescence in human endometrial mesenchymal stem cells (eMSC). This study aimed to investigate the fate of eMSC-survived sublethal heat shock (SHS) with special emphasis on their genetic stability and possible malignant transformation using methods of classic and molecular karyotyping, next-generation sequencing, and transcriptome functional analysis. G-banding revealed random chromosome breakages and aneuploidy in the SHS-treated eMSC. Molecular karyotyping found no genomic imbalance in these cells. Gene module and protein interaction network analysis of mRNA sequencing data showed that compared to untreated cells, SHS-survived progeny revealed some difference in gene expression. However, no hallmarks of cancer were found. Our data identified downregulation of oncogenic signaling, upregulation of tumor-suppressing and prosenescence signaling, induction of mismatch, and excision DNA repair. The common feature of heated eMSC is the silence of MYC, AKT1/PKB oncogenes, and hTERT telomerase. Overall, our data indicate that despite genetic instability, SHS-survived eMSC do not undergo transformation. After long-term cultivation, these cells like their unheated counterparts enter replicative senescence and die.

Therapeutic doses of doxorubicin induce premature senescence of human mesenchymal stem cells derived from menstrual blood, bone marrow and adipose tissue

Doxorubicin (Dox) is an effective anticancer drug with known activity against a wide spectrum of malignancies, hematologic malignancies in particular. Despite extensive clinical use, the mechanisms of its side effects and negative action on normal cells remain under study. The aim of this study was to investigate the effect of Dox on cultured human mesenchymal stem cells (MSCs) derived from menstrual blood (eMSCs), bone marrow (BMSCs) and adipose tissue (AMSCs). Dox treatment in high doses decreased the survival of MSCs in a dose-dependent manner. Clinically relevant low doses of Dox induced premature senescence of eMSCs, BMSCs and AMSCs, but did not kill the cells. Dox caused cell cycle arrest and formation of γ-H2AX foci, and increased the number of SA-β-gal-positive cells. BMSCs entered premature senescence earlier than other MSCs. It has been reported that neural-like cells differentiated from MSCs of various origins are more sensitive to Dox than their parent cells. Dox-treated differentiated MSCs exhibited lower viability and earlier generation of γ-H2AX foci. Dox administration inhibited secretory activity in neural-like cells. These findings suggest that a clinically relevant Dox dose damages cultured MSCs, inducing their premature senescence. MSCs are more resistant to this damage than differentiated cells.

Effects of sulfur mustard on mesenchymal stem cells

Chronic wound healing disorders that occur as a result of a sulfur mustard (SM) exposure present a particular challenge. These chronic wounds are similar to other chronic wounds. In the past, it has been shown that mesenchymal stem cells (MSC) play an important role in the healing of chronic wounds. An important property to support wound healing is their ability to migrate. However, we were able to show that SM leads to a reduction in MSC migration even at low concentrations. Currently, exposed MSCs are still able to differentiate. Further alterations are not known. The current investigation therefore focused onto the question how SM affects MSC.

MATERIAL & METHODS

The effect of SM on MSC was investigated. Here, the alkylation of DNA was considered, and DNA adducts were quantified over a period of 48h. The modification of the nuclei under the influence of SM was analyzed as well as proliferation of the cells by immunohistochemical staining with Ki-67 and quantification. For the quantification of the apoptosis rate, antibodies against cleaved Caspase-3, 8, and apoptosis inducing factor (AIF) were used. The senescence analysis was performed after histological staining against β-galactosidase. Quantifications were carried out by using the TissueQuest System and the software TissueFAX.

RESULTS

SM exposure of MSC results in a dose dependent formation of nuclear DNA adducts. 4h after exposure the cells display a decreasing concentration of DNA adducts. This process is accompanied by a change of nuclei shape but without an increase of apoptosis induction. In parallel the number of cells undergoing senescence increases as a function of the SM concentration.

DISCUSSION

SM exposure of MSC leads to adduct formation on chromosomal DNA. These DNA adducts can be reduced without MSC are undergoing apoptosis. This indicates an active DNA damage response (DDR) pathway in combination with the formation of persistent nuclear DNA damage foci. This process is accompanied by a reduced capability of proliferation and a transition into the senescent state.

SIPS as a model to study age-related changes in proteolysis and aggregate formation

Aging is accompanied by the accumulation of cellular damage over time in response to stress, lifestyle and environmental factors ultimately leading to age-related diseases and death. Additionally, the number of senescent cells increases with age. Senescence is most likely not a static endpoint, it represents a series of hallmarks including morphological changes, alterations in protein turnover and accumulation of protein aggregates. The importance of protein oxidation and aggregate accumulation in the progression of aging is not yet fully understood and research to what extent the accumulation of oxidized proteins has an effect on senescence and the aging process is still ongoing. To study the mechanisms of aging, the impact of senescence and the role of protein aggregates on the aging process, cell culture models are useful tools. Most notably stress induced premature senescence (SIPS) models have contributed to the identification of mechanisms involved in the aging process and helped unravel the age-related changes in proteolysis and the importance of protein aggregation. Here we review characteristics of replicative and premature senescence, how to induce most frequently used senescence models and gained knowledge on age-related changes in the major proteolytic systems.

Magnolol pretreatment attenuates heat stress-induced IEC-6 cell injury

OBJECTIVE

Heat stress (HS) is an important environmental stressor that adversely influences livestock during the summer. The aim of this study was to investigate whether magnolol protects against HS-induced intestinal epithelial cell injury.

MATERIALS AND METHODS

An intestinal epithelial cell line (IEC-6) was subjected to HS at 42 °C, with and without magnolol pretreatment. Cell injury was detected by monitoring lactate dehydrogenase (LDH) release. MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay was used to assess cell proliferation and viability, including identifying effective concentrations of magnolol. Flow cytometry confirmed G1-phase cell-cycle arrest and its alleviation by magnolol. Active DNA synthesis was measured by incorporation of nucleic acid 5-ethynyl-2'-deoxyuridine (EdU). G1-phase cell-cycle-related gene expression was assessed by real-time reverse transcription polymerase chain reaction (RT-PCR) and levels of G1-phase-related proteins by Western blotting.

RESULTS

HS induced IEC-6 cell injury and decreased cell viability, as demonstrated by data from LDH and MTS assays, respectively. Based on a number of criteria, IEC-6 cells subjected to HS were arrested in the G1 phase of the cell cycle. Magnolol pretreatment decreased HS-induced cell injury through relief of this cell-cycle arrest.

CONCLUSIONS

Magnolol pretreatment attenuates HS-induced injury in IEC-6 cells. Magnolol is potentially promising as a protective strategy for HS in livestock.

Senescence in Human Mesenchymal Stem Cells: Functional Changes and Implications in Stem Cell-Based Therapy

Regenerative medicine is extensively interested in developing cell therapies using mesenchymal stem cells (MSCs), with applications to several aging-associated diseases. For successful therapies, a substantial number of cells are needed, requiring extensive ex vivo cell expansion. However, MSC proliferation is limited and it is quite likely that long-term culture evokes continuous changes in MSCs. Therefore, a substantial proportion of cells may undergo senescence. In the present review, we will first present the phenotypic characterization of senescent human MSCs (hMSCs) and their possible consequent functional alterations. The accumulation of oxidative stress and dysregulation of key differentiation regulatory factors determine decreased differentiation potential of senescent hMSCs. Senescent hMSCs also show a marked impairment in their migratory and homing ability. Finally, many factors present in the secretome of senescent hMSCs are able to exacerbate the inflammatory response at a systemic level, decreasing the immune modulation activity of hMSCs and promoting either proliferation or migration of cancer cells. Considering the deleterious effects that these changes could evoke, it would appear of primary importance to monitor the occurrence of senescent phenotype in clinically expanded hMSCs and to evaluate possible ways to prevent in vitro MSC senescence. An updated critical presentation of the possible strategies for in vitro senescence monitoring and prevention constitutes the second part of this review. Understanding the mechanisms that drive toward hMSC growth arrest and evaluating how to counteract these for preserving a functional stem cell pool is of fundamental importance for the development of efficient cell-based therapeutic approaches.

Cryopreserved Mesenchymal Stromal Cells Are Susceptible to T-Cell Mediated Apoptosis Which Is Partly Rescued by IFNγ Licensing

We have previously demonstrated that cryopreservation and thawing lead to altered Mesenchymal stromal cells (MSC) functionalities. Here, we further analyzed MSC's fitness post freeze-thaw. We have observed that thawed MSC can suppress T-cell proliferation when separated from them by transwell membrane and the effect is lost in a MSC:T-cell coculture system. Unlike actively growing MSCs, thawed MSCs were lysed upon coculture with activated autologous Peripheral Blood Mononuclear Cells (PBMCs) and the lysing effect was further enhanced with allogeneic PBMCs. The use of DMSO-free cryoprotectants or substitution of Human Serum Albumin (HSA) with human platelet lysate in freezing media and use of autophagy or caspase inhibitors did not prevent thaw defects. We tested the hypothesis that IFNγ prelicensing before cryobanking can enhance MSC fitness post thaw. Post thawing, IFNγ licensed MSCs inhibit T cell proliferation as well as fresh MSCs and this effect can be blocked by 1-methyl Tryptophan, an Indoleamine 2,3-dioxygenase (IDO) inhibitor. In addition, IFNγ prelicensed thawed MSCs inhibit the degranulation of cytotoxic T cells while IFNγ unlicensed thawed MSCs failed to do so. However, IFNγ prelicensed thawed MSCs do not deploy lung tropism in vivo following intravenous injection as well as fresh MSCs suggesting that IFNγ prelicensing does not fully rescue thaw-induced lung homing defect. We identified reversible and irreversible cryoinjury mechanisms that result in susceptibility to host T-cell cytolysis and affect MSC's cell survival and tissue distribution. The susceptibility of MSC to negative effects of cryopreservation and the potential to mitigate the effects with IFNγ prelicensing may inform strategies to enhance the therapeutic efficacy of MSC in clinical use. Stem Cells 2016;34:2429-2442.

Recombinant HSP70 and mild heat shock stimulate growth of aged mesenchymal stem cells

Heat shock proteins including the major stress protein HSP70 support intracellular homeostasis and prevent protein damage after a temperature increase and other stressful environmental stimuli, as well as during aging. We have shown earlier that prolonged administration of recombinant human HSP70 to mice exhibiting Alzheimer's-like neurodegeneration as well as during sepsis reduces the clinical manifestations of these pathologies. Herein, we studied the action of recombinant human HSP70 on young and aged mouse mesenchymal stem cells (MSCs) in culture. The results obtained indicate that HSP70 at concentrations of 2 μg/ml and higher significantly stimulates growth of aged but not young MSCs. A similar effect is produced by application of a mild heat shock (42 °C 5 min) to the cells. Importantly, responses of young and aged MSCs to heat shock treatment of various durations differed drastically, and aged MSCs were significantly more sensitive to higher heat stress exposures than the young cells. Western blotting and protein labeling experiments demonstrated that neither mild heat shock nor exogenous HSP70 administration resulted in significant endogenous HSP70 induction in young and aged MSCs, whereas mild heat shock increased HSC70 levels in aged MSCs. The results of this study suggest that the administration of exogenous HSP70 and the application of mild heat stress may produce a certain "rejuvenating" effect on MSCs and possibly other cell types in vivo, and these interventions may potentially be used for life extension by delaying various manifestations of aging at the molecular and cellular level.

Pelleted Bone Marrow Derived Mesenchymal Stem Cells Are Better Protected from the Deleterious Effects of Arthroscopic Heat Shock

Introduction: The impact of arthroscopic temperature on joint tissues is poorly understood and it is not known how mesenchymal stem cells (MSCs) respond to the effects of heat generated by the device during the process of arthroscopy assisted experimental cell-based therapy. In the present study, we isolated and phenotypically characterized human bone marrow mesenchymal stem cells (hBMMSCs) from osteoarthritis (OA) patients, and evaluated the effect of arthroscopic heat on cells in suspension and pellet cultures.

Methods: Primary cultures of hBMMSCs were isolated from bone marrow aspirates of OA patients and cultured using DMEM supplemented with 10% FBS and characterized for their stemness. hBMMSCs (1 × 10⁶ cells) cultured as single cell suspensions or cell pellets were exposed to an illuminated arthroscope for 10, 20, or 30 min. This was followed by analysis of cellular proliferation and heat shock related gene expression.

Results: hBMMSCs were viable and exhibited population doubling, short spindle morphology, MSC related CD surface markers expression and tri-lineage differentiation into adipocytes, chondrocytes and osteoblasts. Chondrogenic and osteogenic differentiation increased collagen production and alkaline phosphatase activity. Exposure of hBMMSCs to an illuminated arthroscope for 10, 20, or 30 min for 72 h decreased metabolic activity of the cells in suspensions (63.27% at 30 min) and increased metabolic activity in cell pellets (62.86% at 10 min and 68.57% at 20 min). hBMMSCs exposed to 37, 45, and 55°C for 120 s demonstrated significant upregulation of BAX, P53, Cyclin A2, Cyclin E1, TNF-α, and HSP70 in cell suspensions compared to cell pellets.

Conclusions: hBMMSC cell pellets are better protected from temperature alterations compared to cell suspensions. Transplantation of hBMMSCs as pellets rather than as cell suspensions to the cartilage defect site would therefore support their viability and may aid enhanced cartilage regeneration.

Senescence as a general cellular response to stress: A mini-review

Cellular senescence was initially described as the phenomenon of limited cell divisions that normal cells in culture can undergo during long-term-cultivation. Later it was found that senescence may be induced by various stress factors. The intriguing resemblance between stress-induced and replicative senescence makes questionable the distinction between both types and suggests that the cellular senescence is a common outcome of stress response. Growing evidences support the idea that stress-induced senescence is the cell-type specific.

Persistent DNA damage-induced premature senescence alters the functional features of human bone marrow mesenchymal stem cells

Human mesenchymal stem cells (hMSCs) are adult multipotent stem cells located in various tissues, including the bone marrow. In contrast to terminally differentiated somatic cells, adult stem cells must persist and function throughout life to ensure tissue homeostasis and repair. For this reason, they must be equipped with DNA damage responses able to maintain genomic integrity while ensuring their lifelong persistence. Evaluation of hMSC response to genotoxic insults is of great interest considering both their therapeutic potential and their physiological functions. This study aimed to investigate the response of human bone marrow MSCs to the genotoxic agent Actinomycin D (ActD), a well-known anti-tumour drug. We report that hMSCs react by undergoing premature senescence driven by a persistent DNA damage response activation, as hallmarked by inhibition of DNA synthesis, p21 and p16 protein expression, marked Senescent Associated β-galactosidase activity and enlarged γH2AX foci co-localizing with 53BP1 protein. Senescent hMSCs overexpress several senescence-associated secretory phenotype (SASP) genes and promote motility of lung tumour and osteosarcoma cell lines in vitro. Our findings disclose a multifaceted consequence of ActD treatment on hMSCs that on the one hand helps to preserve this stem cell pool and prevents damaged cells from undergoing neoplastic transformation, and on the other hand alters their functional effects on the surrounding tissue microenvironment in a way that might worsen their tumour-promoting behaviour.