NOTCH Signaling Is Activated through Mechanical Strain in Human Bone Marrow-Derived Mesenchymal Stromal Cells

Regulation and mechanistic insights into tensile strain in mesenchymal stem cell osteogenic differentiation

Bone marrow mesenchymal stem cells (BMSCs) are integral to bone remodeling and homeostasis, as they are capable of differentiating into osteogenic and adipogenic lineages. This differentiation is substantially influenced by mechanosensitivity, particularly to tensile strain, which is a prevalent mechanical stimulus known to enhance osteogenic differentiation. This review specifically examines the effects of various cyclic tensile stress (CTS) conditions on BMSC osteogenesis. It delves into the effects of different loading devices, magnitudes, frequencies, elongation levels, dimensionalities, and coculture conditions, providing a comparative analysis that aids identification of the most conducive parameters for the osteogenic differentiation of BMSCs. Subsequently, this review delineates the signaling pathways activated by CTS, such as Wnt/β-catenin, BMP, Notch, MAPK, PI3K/Akt, and Hedgehog, which are instrumental in mediating the osteogenic differentiation of BMSCs. Through a detailed examination of these pathways, this study elucidates the intricate mechanisms whereby tensile strain promotes osteogenic differentiation, offering valuable guidance for optimizing therapeutic strategies aimed at enhancing bone regeneration.

Regulation of Notch1 Signalling by Long Non-Coding RNAs in Cancers and Other Health Disorders

Notch1 signalling plays a multifaceted role in tissue development and homeostasis. Currently, due to the pivotal role of Notch1 signalling, the relationship between NOTCH1 expression and the development of health disorders is being intensively studied. Nevertheless, Notch1 signalling is not only controlled at the transcriptional level but also by a variety of post-translational events. First is the ligand-dependent mechanical activation of NOTCH receptors and then the intracellular crosstalk with other signalling molecules-among those are long non-coding RNAs (lncRNAs). In this review, we provide a detailed overview of the specific role of lncRNAs in the modulation of Notch1 signalling, from expression to activity, and their connection with the development of health disorders, especially cancers.

Integrating physicomechanical and biological strategies for BTE: biomaterials-induced osteogenic differentiation of MSCs

Large bone defects are a major global health concern. Bone tissue engineering (BTE) is the most promising alternative to avoid the drawbacks of autograft and allograft bone. Nevertheless, how to precisely control stem cell osteogenic differentiation has been a long-standing puzzle. Compared with biochemical cues, physicomechanical stimuli have been widely studied for their biosafety and stability. The mechanical properties of various biomaterials (polymers, bioceramics, metal and alloys) become the main source of physicomechanical stimuli. By altering the stiffness, viscoelasticity, and topography of materials, mechanical stimuli with different strengths transmit into precise signals that mediate osteogenic differentiation. In addition, externally mechanical forces also play a critical role in promoting osteogenesis, such as compression stress, tensile stress, fluid shear stress and vibration, etc. When exposed to mechanical forces, mesenchymal stem cells (MSCs) differentiate into osteogenic lineages by sensing mechanical stimuli through mechanical sensors, including integrin and focal adhesions (FAs), cytoskeleton, primary cilium, ions channels, gap junction, and activating osteogenic-related mechanotransduction pathways, such as yes associated proteins (YAP)/TAZ, MAPK, Rho-GTPases, Wnt/β-catenin, TGFβ superfamily, Notch signaling. This review summarizes various biomaterials that transmit mechanical signals, physicomechanical stimuli that directly regulate MSCs differentiation, and the mechanical transduction mechanisms of MSCs. This review provides a deep and broad understanding of mechanical transduction mechanisms and discusses the challenges that remained in clinical translocation as well as the outlook for the future improvements.

Role of mechano-sensitive non-coding RNAs in bone remodeling of orthodontic tooth movement: recent advances

Orthodontic tooth movement relies on bone remodeling and periodontal tissue regeneration in response to the complicated mechanical cues on the compressive and tensive side. In general, mechanical stimulus regulates the expression of mechano-sensitive coding and non-coding genes, which in turn affects how cells are involved in bone remodeling. Growing numbers of non-coding RNAs, particularly mechano-sensitive non-coding RNA, have been verified to be essential for the regulation of osteogenesis and osteoclastogenesis and have revealed how they interact with signaling molecules to do so. This review summarizes recent findings of non-coding RNAs, including microRNAs and long non-coding RNAs, as crucial regulators of gene expression responding to mechanical stimulation, and outlines their roles in bone deposition and resorption. We focused on multiple mechano-sensitive miRNAs such as miR-21, - 29, -34, -103, -494-3p, -1246, -138-5p, -503-5p, and -3198 that play a critical role in osteogenesis function and bone resorption. The emerging roles of force-dependent regulation of lncRNAs in bone remodeling are also discussed extensively. We summarized mechano-sensitive lncRNA XIST, H19, and MALAT1 along with other lncRNAs involved in osteogenesis and osteoclastogenesis. Ultimately, we look forward to the prospects of the novel application of non-coding RNAs as potential therapeutics for tooth movement and periodontal tissue regeneration.

Molecular mechanisms of exercise contributing to tissue regeneration

Physical activity has been known as an essential element to promote human health for centuries. Thus, exercise intervention is encouraged to battle against sedentary lifestyle. Recent rapid advances in molecular biotechnology have demonstrated that both endurance and resistance exercise training, two traditional types of exercise, trigger a series of physiological responses, unraveling the mechanisms of exercise regulating on the human body. Therefore, exercise has been expected as a candidate approach of alleviating a wide range of diseases, such as metabolic diseases, neurodegenerative disorders, tumors, and cardiovascular diseases. In particular, the capacity of exercise to promote tissue regeneration has attracted the attention of many researchers in recent decades. Since most adult human organs have a weak regenerative capacity, it is currently a key challenge in regenerative medicine to improve the efficiency of tissue regeneration. As research progresses, exercise-induced tissue regeneration seems to provide a novel approach for fighting against injury or senescence, establishing strong theoretical basis for more and more "exercise mimetics." These drugs are acting as the pharmaceutical alternatives of those individuals who cannot experience the benefits of exercise. Here, we comprehensively provide a description of the benefits of exercise on tissue regeneration in diverse organs, mainly focusing on musculoskeletal system, cardiovascular system, and nervous system. We also discuss the underlying molecular mechanisms associated with the regenerative effects of exercise and emerging therapeutic exercise mimetics for regeneration, as well as the associated opportunities and challenges. We aim to describe an integrated perspective on the current advances of distinct physiological mechanisms associated with exercise-induced tissue regeneration on various organs and facilitate the development of drugs that mimics the benefits of exercise.

Delineating cooperative effects of Notch and biomechanical signals on patterned liver differentiation

Controlled in vitro multicellular culture systems with defined biophysical microenvironment have been used to elucidate the role of Notch signaling in the spatiotemporal regulation of stem and progenitor cell differentiation. In addition, computational models incorporating features of Notch ligand-receptor interactions have provided important insights into Notch pathway signaling dynamics. However, the mechanistic relationship between Notch-mediated intercellular signaling and cooperative microenvironmental cues is less clear. Here, liver progenitor cell differentiation patterning was used as a model to systematically evaluate the complex interplay of cellular mechanics and Notch signaling along with identifying combinatorial mechanisms guiding progenitor fate. We present an integrated approach that pairs a computational intercellular signaling model with defined microscale culture configurations provided within a cell microarray platform. Specifically, the cell microarray-based experiments were used to validate and optimize parameters of the intercellular Notch signaling model. This model incorporated the experimentally established multicellular dimensions of the cellular microarray domains, mechanical stress-related activation parameters, and distinct Notch receptor-ligand interactions based on the roles of the Notch ligands Jagged-1 and Delta-like-1. Overall, these studies demonstrate the spatial control of mechanotransduction-associated components, key growth factor and Notch signaling interactions, and point towards a possible role of E-Cadherin in translating intercellular mechanical gradients to downstream Notch signaling.

Optogenetic control of NOTCH1 signaling

The Notch signaling pathway is a crucial regulator of cell differentiation as well as tissue organization, whose deregulation is linked to the pathogenesis of different diseases. NOTCH1 plays a key role in breast cancer progression by increasing proliferation, maintenance of cancer stem cells, and impairment of cell death. NOTCH1 is a mechanosensitive receptor, where mechanical force is required to activate the proteolytic cleavage and release of the Notch intracellular domain (NICD). We circumvent this limitation by regulating Notch activity by light. To achieve this, we have engineered an optogenetic NOTCH1 receptor (optoNotch) to control the activation of NOTCH1 intracellular domain (N1ICD) and its downstream transcriptional activities. Using optoNotch we confirm that NOTCH1 activation increases cell proliferation in MCF7 and MDA-MB-468 breast cancer cells in 2D and spheroid 3D cultures, although causing distinct cell-type specific migratory phenotypes. Additionally, optoNotch activation induced chemoresistance on the same cell lines. OptoNotch allows the fine-tuning, ligand-independent, regulation of N1ICD activity and thus a better understanding of the spatiotemporal complexity of Notch signaling. Video Abstract.

Effects of Mechanical Stress Stimulation on Function and Expression Mechanism of Osteoblasts

Osteoclasts and osteoblasts play a major role in bone tissue homeostasis. The homeostasis and integrity of bone tissue are maintained by ensuring a balance between osteoclastic and osteogenic activities. The remodeling of bone tissue is a continuous ongoing process. Osteoclasts mainly play a role in bone resorption, whereas osteoblasts are mainly involved in bone remodeling processes, such as bone cell formation, mineralization, and secretion. These cell types balance and restrict each other to maintain bone tissue metabolism. Bone tissue is very sensitive to mechanical stress stimulation. Unloading and loading of mechanical stress are closely related to the differentiation and formation of osteoclasts and bone resorption function as well as the differentiation and formation of osteoblasts and bone formation function. Consequently, mechanical stress exerts an important influence on the bone microenvironment and bone metabolism. This review focuses on the effects of different forms of mechanical stress stimulation (including gravity, continuously compressive pressure, tensile strain, and fluid shear stress) on osteoclast and osteoblast function and expression mechanism. This article highlights the involvement of osteoclasts and osteoblasts in activating different mechanical transduction pathways and reports changings in their differentiation, formation, and functional mechanism induced by the application of different types of mechanical stress to bone tissue. This review could provide new ideas for further microscopic studies of bone health, disease, and tissue damage reconstruction.

Identification osteogenic signaling pathways following mechanical stimulation: A systematic review

INTRODUCTION

It has been shown that mechanical forces can induce or promote osteogenic differentiation as well as remodeling of the new created bone tissues. To apply this characteristic in bone tissue engineering, it is important to know which mechanical stimuli through which signaling pathway has a more significant impact on osteogenesis.

METHODS

In this systematic study, an electronic search was conducted using PubMed and Google Scholar databases. This study has been prepared and organized according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Included studies were first categorized according to the in vivo and in vitro studies.

RESULTS

Six types of mechanical stresses were used in these articles and the most commonly used mechanical force and cell source were tension and bone marrow-derived mesenchymal stem cells (BMMSCs), respectively. These forces were able to trigger twelve signaling pathways in which Wnt pathway was so prominent.

CONCLUSION

1) Although specific signaling pathways are induced through specific mechanical forces, Wnt signaling pathways are predominantly activated by almost all types of force/stimulation, 2) All signaling pathways regulate expression of RUNX2, which is known as a master regulator of osteogenesis, 3) In Tension force, the mode of force administration, i.e, continuous or non-continuous tension is more important than the percentage of elongation.

Novel approaches to target the microenvironment of bone metastasis

Bone metastases are a frequent and severe complication of advanced-stage cancers. Breast and prostate cancers, the most common malignancies in women and men, respectively, have a particularly high propensity to metastasize to bone. Conceptually, circulating tumour cells (CTCs) in the bloodstream and disseminated tumour cells (DTCs) in the bone marrow provide a snapshot of the dissemination and colonization process en route to clinically apparent bone metastases. Many cell types that constitute the bone microenvironment, including osteoblasts, osteocytes, osteoclasts, adipocytes, endothelial cells, haematopoietic stem cells and immune cells, engage in a dialogue with tumour cells. Some of these cells modify tumour biology, while others are disrupted and out-competed by tumour cells, thus leading to distinct phases of tumour cell migration, dormancy and latency, and therapy resistance and progression to overt bone metastases. Several current bone-protective therapies act by interrupting these interactions, mainly by targeting tumour cell-osteoclast interactions. In this Review, we describe the functional roles of the bone microenvironment and its components in the initiation and propagation of skeletal metastases, outline the biology and clinical relevance of CTCs and DTCs, and discuss established and future therapeutic approaches that specifically target defined components of the bone microenvironment to prevent or treat skeletal metastases.

Evening the playing field: microenvironmental control over stem cell competition during fate programming

Recent advancements in cellular engineering, including reprogramming of somatic cells into pluripotent stem cells, have opened the door to a new era of regenerative medicine. Given that cellular decisions are guided by microenvironmental cues, such as secreted factors and interactions with neighbouring cells, reproducible cell manufacturing requires robust control over cell-cell interactions. Cell competition has recently emerged as a previously unknown interaction that plays a significant role in shaping the growth and death dynamics of multicellular stem cell populations, both in vivo and in vitro. Although recent studies have largely focused on exploring how the differential expression of key genes mediate the competitive elimination of some cells, little is known about the impact of the microenvironment on cell competition, despite its critical role in shaping cell fate outcomes. Here, we explore recent findings that have brought cell competition into the spotlight, while dissecting the role of microenvironmental factors for controlling competition in cell fate programming applications.

Enhanced Osteogenic Differentiation of Pluripotent Stem Cells via γ-Secretase Inhibition

Bone healing is a complex, well-organized process. Multiple factors regulate this process, including growth factors, hormones, cytokines, mechanical stimulation, and aging. One of the most important signaling pathways that affect bone healing is the Notch signaling pathway. It has a significant role in controlling the differentiation of bone mesenchymal stem cells and forming new bone. Interventions to enhance the healing of critical-sized bone defects are of great importance, and stem cell transplantations are eminent candidates for treating such defects. Understanding how Notch signaling impacts pluripotent stem cell differentiation can significantly enhance osteogenesis and improve the overall healing process upon transplantation. In Rancourt’s lab, mouse embryonic stem cells (ESC) have been successfully differentiated to the osteogenic cell lineage. This study investigates the role of Notch signaling inhibition in the osteogenic differentiation of mouse embryonic and induced pluripotent stem cells (iPS). Our data showed that Notch inhibition greatly enhanced the differentiation of both mouse embryonic and induced pluripotent stem cells.

Tissue Engineering Strategies to Increase Osteochondral Regeneration of Stem Cells; a Close Look at Different Modalities

The homeostasis of osteochondral tissue is tightly controlled by articular cartilage chondrocytes and underlying subchondral bone osteoblasts via different internal and external clues. As a correlate, the osteochondral region is frequently exposed to physical forces and mechanical pressure. On this basis, distinct sets of substrates and physicochemical properties of the surrounding matrix affect the regeneration capacity of chondrocytes and osteoblasts. Stem cells are touted as an alternative cell source for the alleviation of osteochondral diseases. These cells appropriately respond to the physicochemical properties of different biomaterials. This review aimed to address some of the essential factors which participate in the chondrogenic and osteogenic capacity of stem cells. Elements consisted of biomechanical forces, electrical fields, and biochemical and physical properties of the extracellular matrix are the major determinant of stem cell differentiation capacity. It is suggested that an additional certain mechanism related to signal-transduction pathways could also mediate the chondro-osteogenic differentiation of stem cells. The discovery of these clues can enable us to modulate the regeneration capacity of stem cells in osteochondral injuries and lead to the improvement of more operative approaches using tissue engineering modalities.

Designing Biomaterials to Modulate Notch Signaling in Tissue Engineering and Regenerative Medicine

The design of cell-instructive biomaterials for tissue engineering and regenerative medicine is at a crossroads. Although the conventional tissue engineering approach is top-down (cells seeded to macroporous scaffolds and mature to form tissues), bottom-up tissue engineering strategies are becoming appealing. With such developments, we can study cell signaling events, thus enabling functional tissue assembly in physiologic and diseased models. Among many important signaling pathways, the Notch signaling pathway is the most diverse in its influence during tissue morphogenesis and repair following injury. Although Notch signaling is extensively studied in developmental biology and cancer biology, our knowledge of designing biomaterial-based Notch signaling platforms and incorporating Notch signaling components into engineered tissue systems is limited. By incorporating Notch signaling to tissue engineering scaffolds, we can direct cell-specific responses and improve engineered tissue maturation. This review will discuss recent progress in the development of Notch signaling biomaterials as a promising target to control cellular fate decisions, including the influences of ligand identity, biophysical material cues, ligand presentation strategies, and mechanotransduction. Notch signaling is consequently of interest to direct, control, and reprogram cellular behavior on a biomaterial surface. We anticipate that discussions in this article will allow for enhanced knowledge and insight into designing Notch targeted biomaterials for various tissue engineering and cell fate determinations. Impact statement Notch signaling is recognized as an important pathway in tissue engineering and regenerative medicine; however, there is no systematic review on this topic. The comprehensive review and perspectives presented here provide an in-depth discussion on ligand presentation strategies both in 2D and in 3D cell culture environments involving biomaterials/scaffolds. In addition, this review article provides insight into the challenges in designing cell surrogate biomaterials capable of providing Notch signals. To the best of the authors' knowledge, this is the first review relevant to the fields of tissue engineering.

Phosphodiesterase 10A Is a Mediator of Osteogenic Differentiation and Mechanotransduction in Bone Marrow-Derived Mesenchymal Stromal Cells

Bone marrow-derived mesenchymal stromal cells (hMSCs) are capable of differentiating into the osteogenic lineage, and for osteogenic differentiation, mechanical loading is a relevant stimulus. Mechanotransduction leads to the formation of second messengers such as cAMP, cGMP, or Ca²⁺ influx resulting in the activation of transcription factors mediating gene regulation. The second messengers cAMP and cGMP are degraded by phosphodiesterase isoenzymes (PDE), but the role of these enzymes during osteogenic differentiation or mechanotransduction remains unclear. Here, we focused on the isoenzyme phosphodiesterase 10A (PDE10A) and its role during osteogenic commitment and mechanotransduction. We observed a time-dependent decrease of PDE10A expression in hMSC undergoing differentiation towards the osteogenic lineage. PDE10A inhibition by papaverine diminished osteogenic differentiation. While applying mechanical strain via cyclic stretching of hMSCs led to an upregulation of PDE10A gene expression, inhibition of PDE10A using the drug papaverine repressed expression of mechanoresponsive genes. We conclude that PDE10A is a modulator of osteogenic differentiation as well as mechanotransduction in hMSCs. Our data further suggests that the relative increase of cAMP, rather than the absolute cAMP level, is a key driver of the observed effects.

Interactions between Muscle and Bone-Where Physics Meets Biology

Muscle and bone interact via physical forces and secreted osteokines and myokines. Physical forces are generated through gravity, locomotion, exercise, and external devices. Cells sense mechanical strain via adhesion molecules and translate it into biochemical responses, modulating the basic mechanisms of cellular biology such as lineage commitment, tissue formation, and maturation. This may result in the initiation of bone formation, muscle hypertrophy, and the enhanced production of extracellular matrix constituents, adhesion molecules, and cytoskeletal elements. Bone and muscle mass, resistance to strain, and the stiffness of matrix, cells, and tissues are enhanced, influencing fracture resistance and muscle power. This propagates a dynamic and continuous reciprocity of physicochemical interaction. Secreted growth and differentiation factors are important effectors of mutual interaction. The acute effects of exercise induce the secretion of exosomes with cargo molecules that are capable of mediating the endocrine effects between muscle, bone, and the organism. Long-term changes induce adaptations of the respective tissue secretome that maintain adequate homeostatic conditions. Lessons from unloading, microgravity, and disuse teach us that gratuitous tissue is removed or reorganized while immobility and inflammation trigger muscle and bone marrow fatty infiltration and propagate degenerative diseases such as sarcopenia and osteoporosis. Ongoing research will certainly find new therapeutic targets for prevention and treatment.

Exercise Promotes the Osteoinduction of HA/β-TCP Biomaterials via the Wnt Signaling Pathway

To investigate the osteoinductive mechanism triggered by hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) biomaterials in mice which keep exercising. Methods: The HA/β-TCP biomaterials were implanted in the muscle of bilateral thighs (non-osseous sites) of eighty Balb/C mice. All animals were then randomly divided into 4 groups (n = 20). In group 1 (negative control group), the mice were fed routinely. In group 2 (running group), all mice were put on a treadmill which was set to a 60-degree incline. The mice ran 20 min thrice each day. A 5-minute break was included in the routine from day three onwards. In group 3 (weight-bearing group), all mice underwent weight-bearing running. The mice in this group performed the same routine as group 2 while carrying 5 g rubber weights. In group 4 (positive control group), dexamethasone was injected in the implanted sites of the biomaterials from the day of the operation. All mice were injected once per week and received a total of 8 injections. One and eight weeks after surgery, the blood serum was collected to detect inflammatory and immunological factors by ELISA. In addition to this, biomaterial specimens were obtained to observe inflammatory and osteogenic levels via histological staining and to facilitate analysis of the osteogenic mechanism by Western Blot. Results: The inflammation indexes caused by surgery were alleviated through running or weight-bearing running: The tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels were significantly reduced in groups 2 and 3 at week 8. Exercise also enhanced the secretion of interferon-γ (IFN-γ) in mice; this can strengthen their immunity. The new bone tissues were observed in all groups; however, the area percentage of new bone tissues and the number of osteoblasts were highest in the weight-bearing group. Furthermore, the key proteins of wingless/integrated (Wnt) signaling pathway, Wnt1, Wnt3a, and β-catenin, were up-regulated during osteoinduction. This up-regulation activated runt-related transcription factor-2 (Runx2), increased the expression of osteopontin (OPN) and osteocalcin (OCN). Conclusion: Weight-bearing exercise can promote the bone and bone marrow formation through the Wnt signaling pathway: Observations documented here suggest that the proper exercise is beneficial to the recovery of bone damage.

Expression Profiles of MicroRNAs in Stem Cells Differentiation

Stem cells are undifferentiated cells and have a great potential in multilineage differentiation. These cells are classified into adult stem cells like Mesenchymal Stem Cells (MSCs) and Embryonic Stem Cells (ESCs). Stem cells also have potential therapeutic utility due to their pluripotency, self-renewal, and differentiation ability. These properties make them a suitable choice for regenerative medicine. Stem cells differentiation toward functional cells is governed by different signaling pathways and transcription factors. Recent studies have demonstrated the key role of microRNAs in the pathogenesis of various diseases, cell cycle regulation, apoptosis, aging, cell fate decisions. Several types of stem cells have different and unique miRNA expression profiles. Our review summarizes novel regulatory roles of miRNAs in the process of stem cell differentiation especially adult stem cells into a variety of functional cells through signaling pathways and transcription factors modulation. Understanding the mechanistic roles of miRNAs might be helpful in elaborating clinical therapies using stem cells and developing novel biomarkers for the early and effective diagnosis of pathologic conditions.

Notch Signaling in Skeletal Development, Homeostasis and Pathogenesis

Skeletal development is a complex process which requires the tight regulation of gene activation and suppression in response to local signaling pathways. Among these pathways, Notch signaling is implicated in governing cell fate determination, proliferation, differentiation and apoptosis of skeletal cells-osteoblasts, osteoclasts, osteocytes and chondrocytes. Moreover, human genetic mutations in Notch components emphasize the critical roles of Notch signaling in skeletal development and homeostasis. In this review, we focus on the physiological roles of Notch signaling in skeletogenesis, postnatal bone and cartilage homeostasis and fracture repair. We also discuss the pathological gain- and loss-of-function of Notch signaling in bone and cartilage, resulting in osteosarcoma and age-related degenerative diseases, such as osteoporosis and osteoarthritis. Understanding the physiological and pathological function of Notch signaling in skeletal tissues using animal models and human genetics will provide new insights into disease pathogenesis and offer novel approaches for the treatment of bone/cartilage diseases.

Usefulness of Mesenchymal Cell Lines for Bone and Cartilage Regeneration Research

The unavailability of sufficient numbers of human primary cells is a major roadblock for in vitro repair of bone and/or cartilage, and for performing disease modelling experiments. Immortalized mesenchymal stromal cells (iMSCs) may be employed as a research tool for avoiding these problems. The purpose of this review was to revise the available literature on the characteristics of the iMSC lines, paying special attention to the maintenance of the phenotype of the primary cells from which they were derived, and whether they are effectively useful for in vitro disease modeling and cell therapy purposes. This review was performed by searching on Web of Science, Scopus, and PubMed databases from 1 January 2015 to 30 September 2019. The keywords used were ALL = (mesenchymal AND ("cell line" OR immortal*) AND (cartilage OR chondrogenesis OR bone OR osteogenesis) AND human). Only original research studies in which a human iMSC line was employed for osteogenesis or chondrogenesis experiments were included. After describing the success of the immortalization protocol, we focused on the iMSCs maintenance of the parental phenotype and multipotency. According to the literature revised, it seems that the maintenance of these characteristics is not guaranteed by immortalization, and that careful selection and validation of clones with particular characteristics is necessary for taking advantage of the full potential of iMSC to be employed in bone and cartilage-related research.

Signaling pathways involved in colorectal cancer progression

Colorectal cancer (CRC) is the fourth leading cause of the worldwide cancer mortality. Different molecular mechanisms have been attributed to the development and progress of CRC. In this review, we will focus on the mitogen-activated protein kinase (MAPK) cascades downstream of the epidermal growth factor receptor (EGFR), Notch, PI3K/AKT pathway, transforming growth factor-β (TGF-β), and Wnt signaling pathways. Various mutations in the components of these signaling pathways have been linked to the development of CRC. Accordingly, numerous efforts have been carried out to target the signaling pathways to develop novel therapeutic approaches. Herein, we review the signaling pathways involved in the incidence and progression of CRC, and the strategies for the therapy targeting components of signaling pathways in CRC.