Stress as a fundamental theme in cell plasticity

The landscape of cell lineage tracing

Cell fate changes play a crucial role in the processes of natural development, disease progression, and the efficacy of therapeutic interventions. The definition of the various types of cell fate changes, including cell expansion, differentiation, transdifferentiation, dedifferentiation, reprogramming, and state transitions, represents a complex and evolving field of research known as cell lineage tracing. This review will systematically introduce the research history and progress in this field, which can be broadly divided into two parts: prospective tracing and retrospective tracing. The initial section encompasses an array of methodologies pertaining to isotope labeling, transient fluorescent tracers, non-fluorescent transient tracers, non-fluorescent genetic markers, fluorescent protein, genetic marker delivery, genetic recombination, exogenous DNA barcodes, CRISPR-Cas9 mediated DNA barcodes, and base editor-mediated DNA barcodes. The second part of the review covers genetic mosaicism, genomic DNA alteration, TCR/BCR, DNA methylation, and mitochondrial DNA mutation. In the final section, we will address the principal challenges and prospective avenues of enquiry in the field of cell lineage tracing, with a particular focus on the sequencing techniques and mathematical models pertinent to single-cell genetic lineage tracing, and the value of pursuing a more comprehensive investigation at both the spatial and temporal levels in the study of cell lineage tracing.

Cluster-Assembled Zirconia Substrates Accelerate the Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells

Due to their high mechanical strength and good biocompatibility, nanostructured zirconia surfaces (ns-ZrOx) are widely used for bio-applications. Through supersonic cluster beam deposition, we produced ZrOx films with controllable roughness at the nanoscale, mimicking the morphological and topographical properties of the extracellular matrix. We show that a 20 nm ns-ZrOx surface accelerates the osteogenic differentiation of human bone marrow-derived MSCs (bMSCs) by increasing the deposition of calcium in the extracellular matrix and upregulating some osteogenic differentiation markers. bMSCs seeded on 20 nm ns-ZrOx show randomly oriented actin fibers, changes in nuclear morphology, and a reduction in mitochondrial transmembrane potential when compared to the cells cultured on flat zirconia (flat-ZrO₂) substrates and glass coverslips used as controls. Additionally, an increase in ROS, known to promote osteogenesis, was detected after 24 h of culture on 20 nm ns-ZrOx. All the modifications induced by the ns-ZrOx surface are rescued after the first hours of culture. We propose that ns-ZrOx-induced cytoskeletal remodeling transmits signals generated by the extracellular environment to the nucleus, with the consequent modulation of the expression of genes controlling cell fate.

Human Obesity Attenuates Cardioprotection Conferred by Adipose Tissue-Derived Mesenchymal Stem/Stromal Cells

To explore the impact of obesity on reparative potency of adipose tissue-derived mesenchymal stromal/stem cells (A-MSC) in hypertensive cardiomyopathy, A-MSC were harvested from subcutaneous fat of obese and age-matched non-obese human subjects during bariatric or kidney donation surgeries, and then injected into mice 2 weeks after inducing renovascular hypertension (RVH) or sham surgery. Two weeks later, left ventricular (LV) function and deformation were estimated in vivo by micro-magnetic resonance imaging and myocardial damage ex vivo. Blood pressure and myocardial wall thickening were elevated in RVH + Vehicle and normalized only by lean-A-MSC. Both A-MSC types reduced LV mass and normalized the reduced LV peak strain radial in RVH, yet obese-A-MSC also impaired LV systolic function. A-MSC alleviated myocardial tissue damage in RVH, but lean-A-MSC decreased oxidative stress more effectively. Obese-A-MSC also showed increased cellular inflammation in vitro. Therefore, obese-A-MSC are less effective than lean-A-MSC in blunting hypertensive cardiomyopathy in mice with RVH.

Induction of Nanog in neural progenitor cells for adaptive regeneration of ischemic brain

NANOG plays a key role in cellular plasticity and the acquisition of the stem cell state during reprogramming, but its role in the regenerative process remains unclear. Here, we show that the induction of NANOG in neuronal cells is necessary for the physiological initiation of neuronal regeneration in response to ischemic stress. Specifically, we found that NANOG was preferentially expressed in undifferentiated neuronal cells, and forced expression of Nanog in neural progenitor cells (NPCs) promoted their self-renewing expansion both in ex-vivo slice cultures and in vitro limiting dilution analysis. Notably, the upstream region of the Nanog gene contains sequence motifs for hypoxia-inducible factor-1 alpha (HIF-1α). Therefore, cerebral neurons exposed to hypoxia significantly upregulated NANOG expression selectively in primitive (CD133⁺) cells, but not in mature cells, leading to the expansion of NPCs. Notably, up to 80% of the neuronal expansion induced by hypoxia was attributed to NANOG-expressing neuronal cells, whereas knockdown during hypoxia abolished this expansion and was accompanied by the downregulation of other pluripotency-related genes. Moreover, the number of NANOG-expressing neuronal cells were transiently increased in response to ischemic insult, predominantly in the infarct area of brain regions undergoing neurogenesis, but not in non-neurogenic loci. Together, these findings reveal a functional effect of NANOG-induction for the initiation of adaptive neuronal regeneration among heterogeneous NPC subsets, pointing to cellular plasticity as a potential link between regeneration and reprogramming processes.

Human Organ-on-a-Chip Microphysiological Systems to Model Musculoskeletal Pathologies and Accelerate Therapeutic Discovery

Human Microphysiological Systems (hMPS), otherwise known as organ- and tissue-on-a-chip models, are an emerging technology with the potential to replace in vivo animal studies with in vitro models that emulate human physiology at basic levels. hMPS platforms are designed to overcome limitations of two-dimensional (2D) cell culture systems by mimicking 3D tissue organization and microenvironmental cues that are physiologically and clinically relevant. Unlike animal studies, hMPS models can be configured for high content or high throughput screening in preclinical drug development. Applications in modeling acute and chronic injuries in the musculoskeletal system are slowly developing. However, the complexity and load bearing nature of musculoskeletal tissues and joints present unique challenges related to our limited understanding of disease mechanisms and the lack of consensus biomarkers to guide biological therapy development. With emphasis on examples of modeling musculoskeletal tissues, joints on chips, and organoids, this review highlights current trends of microphysiological systems technology. The review surveys state-of-the-art design and fabrication considerations inspired by lessons from bioreactors and biological variables emphasizing the role of induced pluripotent stem cells and genetic engineering in creating isogenic, patient-specific multicellular hMPS. The major challenges in modeling musculoskeletal tissues using hMPS chips are identified, including incorporating biological barriers, simulating joint compartments and heterogenous tissue interfaces, simulating immune interactions and inflammatory factors, simulating effects of in vivo loading, recording nociceptors responses as surrogates for pain outcomes, modeling the dynamic injury and healing responses by monitoring secreted proteins in real time, and creating arrayed formats for robotic high throughput screens. Overcoming these barriers will revolutionize musculoskeletal research by enabling physiologically relevant, predictive models of human tissues and joint diseases to accelerate and de-risk therapeutic discovery and translation to the clinic.

Can the aging influence cold environment mediated cancer risk in the USA female population?

Cancer is one of the most debilitating diseases worldwide. Cancer incidence and/or death depends on several intrinsic and extrinsic factors (e.g., dietary habits, socio-behavioral activities, physical inactivity, smoking, alcohol consumption, gender, races/ethnicities and age). Various studies have found that an inverse relationship subsists between environmental temperature and cancer risk. Furthermore, this negative relationship was found to be more consistent in the USA female population. This research mainly focuses on influence of aging on cold environment mediated cancer risk for overall and various anatomical site-specific cancers. Age-specific county-wise data of cancer incidence rate (CIR) in the USA female population was selected in this study. Statistical analysis found a negative correlation between the average annual temperature (AAT) and CIR in all anatomical sites (AAS; overall) as well as different anatomical site-specific cancers (e.g., breast, melanoma, leukaemia, pancreas, bladder, uterus, thyroid and non-Hodgkin's lymphoma (NHL), except for cervical cancer) in different age groups (e.g., less than 50 years, 50 plus years, less than 65 years and 65 plus years). In addition, an inverse relationship between the AAT and CIR was found in case of paediatric cancer. However, all the results obtained from the linear model based statistical analysis proposed that the older age-group of females particularly above 65 years seems to be more prone to cold temperature linked cancer risk. For example, age-specific cold linked cancer incidence appears to be more inclined in case of breast cancer in the age-group of 65 plus years. This study, for first time, proposes that aging may have a positive influence on the relationship between cancer incidence and environment temperature.

Human adult pluripotency: Facts and questions

Cellular reprogramming and induced pluripotent stem cell (IPSC) technology demonstrated the plasticity of adult cell fate, opening a new era of cellular modelling and introducing a versatile therapeutic tool for regenerative medicine. While IPSCs are already involved in clinical trials for various regenerative purposes, critical questions concerning their medium- and long-term genetic and epigenetic stability still need to be answered. Pluripotent stem cells have been described in the last decades in various mammalian and human tissues (such as bone marrow, blood and adipose tissue). We briefly describe the characteristics of human-derived adult stem cells displaying in vitro and/or in vivo pluripotency while highlighting that the common denominators of their isolation or occurrence within tissue are represented by extreme cellular stress. Spontaneous cellular reprogramming as a survival mechanism favoured by senescence and cellular scarcity could represent an adaptative mechanism. Reprogrammed cells could initiate tissue regeneration or tumour formation dependent on the microenvironment characteristics. Systems biology approaches and lineage tracing within living tissues can be used to clarify the origin of adult pluripotent stem cells and their significance for regeneration and disease.

Deficient primary cilia in obese adipose-derived mesenchymal stem cells: obesity, a secondary ciliopathy?

Obesity alters the composition, structure and function of adipose tissue, characterized by chronic inflammation, insulin resistance and metabolic dysfunction. Adipose-derived mesenchymal stem cells (ASCs) are responsible for cell renewal, spontaneous repair and immunomodulation in adipose tissue. Increasing evidence highlights that ASCs are deficient in obesity, and the underlying mechanisms are not well understood. We have recently shown that obese ASCs have defective primary cilia, which are shortened and unable to properly respond to stimuli. Impaired cilia compromise ASC functions. This work suggests an intertwined connection of obesity, defective cilia and dysfunctional ASCs. We have here discussed the current data regarding defective cilia in various cell types in obesity. Based on these observations, we hypothesize that obesity, a systemic chronic metainflammation, could impair cilia in diverse ciliated cells, like pancreatic islet cells, stem cells and hypothalamic neurons, making these critical cells dysfunctional by shutting down their signal sensors and transducers. In this context, obesity may represent a secondary form of ciliopathy induced by obesity-related inflammation and metabolic dysfunction. Reactivation of ciliated cells might be an alternative strategy to combat obesity and its associated diseases.

Insight into the development of obesity: functional alterations of adipose-derived mesenchymal stem cells

Obesity is associated with a variety of disorders including cardiovascular diseases, diabetes mellitus and cancer. Obesity changes the composition and structure of adipose tissue, linked to pro-inflammatory environment, endocrine/metabolic dysfunction, insulin resistance and oxidative stress. Adipose-derived mesenchymal stem cells (ASCs) have multiple functions like cell renewal, spontaneous repair and homeostasis in adipose tissue. In this review article, we have summarized the recent data highlighting that ASCs in obesity are defective in various functionalities and properties including differentiation, angiogenesis, motility, multipotent state, metabolism and immunomodulation. Inflammatory milieu, hypoxia and abnormal metabolites in obese tissue are crucial for impairing the functions of ASCs. Further work is required to explore the precise molecular mechanisms underlying its alterations and impairments. Based on these data, we suggest that deregulated ASCs, possibly also other mesenchymal stem cells, are important in promoting the development of obesity. Restoration of ASCs/mesenchymal stem cells might be an additional strategy to combat obesity and its associated diseases.

Magnesium Deprivation Potentiates Human Mesenchymal Stem Cell Transcriptional Remodeling

Magnesium plays a pivotal role in energy metabolism and in the control of cell growth. While magnesium deprivation clearly shapes the behavior of normal and neoplastic cells, little is known on the role of this element in cell differentiation. Here we show that magnesium deficiency increases the transcription of multipotency markers and tissue-specific transcription factors in human adipose-derived mesenchymal stem cells exposed to a mixture of natural molecules, i.e., hyaluronic, butyric and retinoid acids, which tunes differentiation. We also demonstrate that magnesium deficiency accelerates the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells. We argue that magnesium deprivation generates a stressful condition that modulates stem cell plasticity and differentiation potential. These studies indicate that it is possible to remodel transcription in mesenchymal stem cells by lowering extracellular magnesium without the need for genetic manipulation, thus offering new hints for regenerative medicine applications.

Evolution from genetics to phenotype: reinterpretation of NSCLC plasticity, heterogeneity, and drug resistance

Lung cancer is the leading cause of cancer-related deaths worldwide. Targeted therapy is beneficial in most cases, but the development of drug resistance stands as an obstacle to good prognosis. Multiple mechanisms were explored such as genetic alterations, activation of bypass signaling, and phenotypic transition. These intrinsic and/or extrinsic dynamic regulations facilitate tumor cell survival in meeting the demands of signaling under different stimulus. This review introduces lung cancer plasticity and heterogeneity and their correlation with drug resistance. While cancer plasticity and heterogeneity play an essential role in the development of drug resistance, the manipulation of them may bring some inspirations to cancer prognosis and treatment. That is to say, lung cancer plasticity and heterogeneity present us with not only challenges but also opportunities.

'Adipaging': ageing and obesity share biological hallmarks related to a dysfunctional adipose tissue

The increasing ageing of our societies is accompanied by a pandemic of obesity and related cardiometabolic disorders. Progressive dysfunction of the white adipose tissue is increasingly recognized as an important hallmark of the ageing process, which in turn contributes to metabolic alterations, multi-organ damage and a systemic pro-inflammatory state ('inflammageing'). On the other hand, obesity, the paradigm of adipose tissue dysfunction, shares numerous biological similarities with the normal ageing process such as chronic inflammation and multi-system alterations. Accordingly, understanding the interplay between accelerated ageing related to obesity and adipose tissue dysfunction is critical to gain insight into the ageing process in general as well as into the pathophysiology of obesity and other related conditions. Here we postulate the concept of 'adipaging' to illustrate the common links between ageing and obesity and the fact that, to a great extent, obese adults are prematurely aged individuals.

Reprogramming of human exocrine pancreas cells to beta cells

One of the key promises of regenerative medicine is providing a cure for diabetes. Cell-based therapies are proving their safety and efficiency, but donor beta cell shortages and immunological issues remain major hurdles. Reprogramming of human pancreatic exocrine cells towards beta cells would offer a major advantage by providing an abundant and autologous source of beta cells. Over the past decade our understanding of transdifferentiation processes greatly increased allowing us to design reprogramming protocols that fairly aim for clinical trials.

Opportunities and challenges of radiotherapy for treating cancer

The past 20 years have seen dramatic changes in the delivery of radiation therapy, but the impact of radiobiology on the clinic has been far less substantial. A major consideration in the use of radiotherapy has been on how best to exploit differences between the tumour and host tissue characteristics, which in the past has been achieved empirically by radiation-dose fractionation. New advances are uncovering some of the mechanistic processes that underlie this success story. In this Review, we focus on how these processes might be targeted to improve the outcome of radiotherapy at the individual patient level. This approach would seem a more productive avenue of treatment than simply trying to increase the radiation dose delivered to the tumour.

Senescence Meets Dedifferentiation

Senescence represents the final stage of leaf development but is often induced prematurely following exposure to biotic and abiotic stresses. Leaf senescence is manifested by color change from green to yellow (due to chlorophyll degradation) or to red (due to de novo synthesis of anthocyanins coupled with chlorophyll degradation) and frequently culminates in programmed death of leaves. However, the breakdown of chlorophyll and macromolecules such as proteins and RNAs that occurs during leaf senescence does not necessarily represent a one-way road to death but rather a reversible process whereby senescing leaves can, under certain conditions, re-green and regain their photosynthetic capacity. This phenomenon essentially distinguishes senescence from programmed cell death, leading researchers to hypothesize that changes occurring during senescence might represent a process of trans-differentiation, that is the conversion of one cell type to another. In this review, we highlight attributes common to senescence and dedifferentiation including chromatin structure and activation of transposable elements and provide further support to the notion that senescence is not merely a deterioration process leading to death but rather a unique developmental state resembling dedifferentiation.

A link between cold environment and cancer

Many risk factors such as smoking and change of life style have been shown to promote genetic and adaptive epigenetic changes responsible for tumorigenesis. This study brings environmental temperature as a cancer causing factor to light. The cancer mortality rate (CMR) of a country was correlated with 17 different variables. Multivariate analysis of a total of 188 countries found that the average annual temperature (AAT) of a country might have a significant contribution to cancer death when compared with other factors such as alcohol and meat consumption. Univariate analysis found a negative correlation between AAT and CMR. All these countries were categorized into three temperature zones (zone I, -2 to 11.5 °C; number of countries, 38; zone II, 11.6 to 18.6 °C; number of countries, 32; and zone III, 18.7 to 30 °C; number of countries, 118). Out of the top-most 50 countries having the highest CMR, 26 (68.42 %), 10 (31.25 %), and 14 (11.66 %) belong to zone I, zone II, and zone III, respectively. Out of the least 50 countries having the lowest CMR, 1 (2.63 %), 4 (12.5 %), and 45 (37.5 %) belong to zone I, zone II, and zone III, respectively. CMR is low in those countries situated near to the Torrid zone (33(°) N to 23.5(°)S), but it is high for those countries situated away from these two latitudes. These data indicate that cold temperature may have a contribution in increasing tumorigenesis. High metabolic stress, which is the result of maintaining our body temperature against a cold environment, could be the possible cause for the higher cancer mortality.

Obesity and weight loss could alter the properties of adipose stem cells?

The discovery that adipose tissue represents an interesting source of multipotent stem cells has led to many studies exploring the clinical potential of these cells in cell-based therapies. Recent advances in understanding the secretory capacity of adipose tissue and the role of adipokines in the development of obesity and associated disorders have added a new dimension to the study of adipose tissue biology in normal and diseased states. Subcutaneous adipose tissue forms the interface between the clinical application of regenerative medicine and the establishment of the pathological condition of obesity. These two facets of adipose tissue should be understood as potentially related phenomena. Because of the functional characteristics of adipose stem cells, these cells represent a fundamental tool for understanding how these two facets are interconnected and could be important for therapeutic applications. In fact, adipose tissue stem cells have multiple functions in obesity related to adipogenic, angiogenic and secretory capacities. In addition, we have also previously described a predominance of larger blood vessels and an adipogenic memory in the subcutaneous adipose tissue after massive weight loss subsequent to bariatric surgery (ex-obese patients). Understanding the reversibility of the behavior of adipose stem cells in obeses and in weight loss is relevant to both physiological studies and the potential use of these cells in regenerative medicine.