Deer antler stem cell niche: An interesting perspective

In recent years,there has been considerable exploration into methods aimed at enhancing the regenerative capacity of transplanted and/or tissue-resident cells.Biomaterials,in particular,have garnered significant interest for their potential to serve as natural scaffolds for cells.In this editorial,we provide commentary on the study by Wang et al,in a recently published issue of World J Stem Cells,which investigates the use of a decellularized xenogeneic extracellular matrix(ECM)derived from antler stem cells for repairing osteochondral defects in rat knee joints.Our focus lies specifically on the crucial role of biological scaffolds as a strategy for augmenting stem cell potential and regenerative capabilities,thanks to the establishment of a favorable microenvironment(niche).Stem cell differen-tiation heavily depends on exposure to intrinsic properties of the ECM,including its chemical and protein composition,as well as the mechanical forces it can generate.Collectively,these physicochemical cues contribute to a bio-instructive signaling environment that offers tissue-specific guidance for achieving effective repair and regeneration.The interest in mechanobiology,often conceptualized as a form of“structural memory”,is steadily gaining more validation and momen-tum,especially in light of findings such as these.

Cerebrospinal fluid and neural stem cell niche control

Neurogenesis from inner brain neural stem cells （NSCs） is a process which takes place continuously in mammals through- out their life. However, the main ontogenic difference is the intensity of neurogenesis, which commences as a very intensive and global activity in the early embryonic brain （neural tube）, persists in fetal and newborn stages, and declines significantly in adulthood, becoming restricted to specific places with low neurogenic activity such as the subventricular zone （SVZ） and the subgranular zone （SGZ） in the dentate gyrus （DG） of the hippocampus.

Current knowledge on the multiform reconstitution of intestinal stem cell niche

The development of“mini-guts”organoid originates from the identification of Lgr5+intestinal stem cells(ISCs)and circumambient signalings within their specific niche at the crypt bottom.These in vitro self-renewing“mini-guts”,also named enteroids or colonoids,undergo perpetual proliferation and regulated differentiation,which results in a high-performance,self-assembling and physiological organoid platform in diverse areas of intestinal research and therapy.The triumphant reconstitution of ISC niche in vitro also relies on Matrigel,a heterogeneous sarcoma extract.Despite the promising prospect of organoids research,their expanding applications are hampered by the canonical culture pattern,which reveals limitations such as inaccessible lumen,confine scale,batch to batch variation and low reproducibility.The tumor-origin of Matrigel also raises biosafety concerns in clinical treatment.However,the convergence of breakthroughs in cellular biology and bioengineering contribute to multiform reconstitution of the ISC niche.Herein,we review the recent advances in the microfabrication of intestinal organoids on hydrogel systems.

Metabolic and proteostatic differences in quiescent and active neural stem cells

Adult neural stem cells are neurogenesis progenitor cells that play an important role in neurogenesis.Therefore,neural regeneration may be a promising target for treatment of many neurological illnesses.The regenerative capacity of adult neural stem cells can be chara cterized by two states:quiescent and active.Quiescent adult neural stem cells are more stable and guarantee the quantity and quality of the adult neural stem cell pool.Active adult neural stem cells are chara cterized by rapid proliferation and differentiation into neurons which allow for integration into neural circuits.This review focuses on diffe rences between quiescent and active adult neural stem cells in nutrition metabolism and protein homeostasis.Furthermore,we discuss the physiological significance and underlying advantages of these diffe rences.Due to the limited number of adult neural stem cells studies,we refe rred to studies of embryonic adult neural stem cells or non-mammalian adult neural stem cells to evaluate specific mechanisms.

Stem Cell Niche,the Microenvironment and Immunological Crosstalk

The concept of stem cells, their physiological existence, the intricate anatomical localization, the known and the unknown functions, and their exclusive utility for the purpose of regenerative medicine, are all now encompassed within an emergent question, ＇how compatible these cells are immunologically？＇ Indeed, the medical aspects of stem cells are dependent on a large number of queries based on the basic properties of the cells. It has greatly been emphasized to probe into the basic research on stem cells before any successful therapeutic attempts are made. One of the intricate aspects of the adult stem cells is its immunological behavior in relation to the microenvironmental associates, the stromal cells in the presence of a suitable target. Cellular ＆ Molecular Immunology.

Sulfur nutrient availability regulates root elongation by affecting root indole-3-acetic acid levels and the stem cell niche

Sulfur is an essential macronutrient for plants with numerous biological functions. However, the influence of sulfur nutrient availability on the regulation of root development remains largely unknown. Here, we report the response of Arabidopsis thaliana L. root development and growth to different levels of sulfate, demonstrating that low sulfate levels promote the primary root elongation. By using various reporter lines, we examined in vivo IAA level and distribution, cell division,and root meristem in response to different sulfate levels.Meanwhile the dynamic changes of in vivo cysteine, glutathione,and IAA levels were measured. Root cysteine, glutathione, and IAA levels are positively correlated with external sulfate levels in the physiological range, which eventually affect root system architecture. Low sulfate levels also downregulate the genes involved in auxin biosynthesis and transport, and elevate the accumulation of PLT1 and PLT2. This study suggests that sulfate level affects the primary root elongation by regulating the endogenous auxin level and root stem cell niche maintenance.

Stem cell niches and endogenous electric fields in tissue repair

Adult stem cells are responsible for homeostasis and repair of many tissues.Endogenous adult stem cells reside in certain regions of organs,known as the stem cell niche,which is recognized to have an important role in regulating tissue maintenance and repair.In wound healing and tissue repair,stem cells are mobilized and recruited to the site of wound,and participate in the repair process.Many regulatory factors are involved in the stem cell-based repair process,including stem cell niches and endogenous wound electric fields,which are present at wound tissues and proved to be important in guiding wound healing.Here we briefly review the role of stem cell niches and endogenous electric fields in tissue repair,and hypothesize that endogenous electric fields become part of stem cell niche in the wound site.

Enhanced homing of mesenchymal stem cells for in situ niche remodeling and bone regeneration

Mesenchymal stem cells(MSCs)transplantation is a promising strategy for osteoporosis treatment.However,limited sources and poor tissue-homing efficiency limit their clinical capabilities.In this study,we isolated a kind of MSCs from women’s menstrual blood(MenSCs)noninvasively and established a novel MSCs bone marrow-targeted delivery system by utilizing waterin-oil-in-water droplet microfluidics.MenSCs were encapsulated withinβ-cyclodextrin-functionalized alginate microcapsules loaded with zoledronates,which has a high affinity for bone.With this delivery system,MenSCs could be preferentially delivered to the bone marrow tissues via intravenous infusion,and restored bone mass by remodeling the bone marrow niche in situ in ovariectomized mouse models.Moreover,scRNA-seq analysis demonstrated that those MenSCs homed to the bone marrow recruited CD4^(+)FOXP3^(+)natural regulatory T(nT_(reg))cells by secreting CCL28.The recruited nTreg promoted CD8^(+)T cells to secret Wnt family member 10B(WNT10B),activating the Wnt signaling in osteoblasts and thus promoting bone formation in situ in the bone marrow.This study reveals a promising application of MenSCs in postmenopausal osteoporosis treatment and highlights the clinical value of MenSCs by encouraging women to reserve autologous MenSCs before menopause to prevent and alleviate postmenopausal osteoporosis.

Adult neural stem cells in the mammalian central nervous system

Neural stem cells （NSCs） are present not only during the embryonic development but also in the adult brain of all mammalian species, including humans. Stem cell niche architecture in vivo enables adult NSCs to continuously generate functional neurons in specific brain regions throughout life. The adult neurogenesis process is subject to dynamic regulation by various physiological, pathological and pharmacological stimuli. Multipotent adult NSCs also appear to be intrinsically plastic, amenable to genetic programing during normal differentiation, and to epigenetic reprograming during de-differentiation into pluripotency. Increasing evidence suggests that adult NSCs significantly contribute to specialized neural functions under physiological and pathological conditions. Fully understanding the biology of adult NSCs will provide crucial insights into both the etiology and potential therapeutic interventions of major brain disorders. Here, we review recent progress on adult NSCs of the mammalian central nervous system, including topics on their identity, niche, function, plasticity, and emerging roles in cancer and regenerative medicine.

Heterogeneous populations of neural stem cells contribute to myelin repair

As ingenious as nature＇s invention of myelin sheaths within the mammalian nervous system is, as fatal can be damage to this specialized lipid structure. Long-term loss of electrical insulation and of further supportive functions myelin provides to axons, as seen in demyelinating diseases such as multiple sclerosis （MS）, leads to neurodegeneration and results in progressive disabilities. Multiple lines of evidence have demon-strated the increasing inability of oligodendrocyte precursor cells （OPCs） to replace lost oligodendrocytes （OLs） in order to restore lost myelin. Much research has been dedicated to reveal potential reasons for this regeneration deficit but despite promising approaches no remyelination-promoting drugs have successfully been developed yet. In addition to OPCs neural stem cells of the adult central nervous system also hold a high potential to generate myelinating OLs. There are at least two neural stem cell niches in the brain, the subventricular zone lining the lateral ventricles and the subgranular zone of the dentate gyrus, and an additional source of neural stem cells has been located in the central canal of the spinal cord. While a substantial body of literature has described their neurogenic capacity, still little is known about the oligodendrogenic potential of these cells, even if some animal studies have provided proof of their contribution to remyelination. In this review, we summarize and discuss these studies, taking into account the different niches, the heterogeneity within and between stem cell niches and present current strategies of how to promote stem cell-mediated myelin repair.

Update on acute myeloid leukemia stem cells:New discoveries and therapeutic opportunities

The existence of cancer stem cells has been wellestablished in acute myeloid leukemia. Initial proof of the existence of leukemia stem cells(LSCs) was accomplished by functional studies in xenograft models making use of the key features shared with normal hematopoietic stem cells(HSCs) such as the capacity of self-renewal and the ability to initiate and sustain growth of progenitors in vivo. Significant progress has also been made in identifying the phenotype and signaling pathways specific for LSCs. Therapeutically, a multitude of drugs targeting LSCs are in different phases of preclinical and clinical development. This review focuses on recent discoveries which have advanced our understanding of LSC biology and provided rational targets for development of novel therapeutic agents. One of the major challenges is how to target the selfrenewal pathways of LSCs without affecting normal HSCs significantly therefore providing an acceptable therapeutic window. Important issues pertinent to the successful design and conduct of clinical trials evaluating drugs targeting LSCs will be discussed as well.

Intestinal stem cells and the colorectal cancer microenvironment

Colorectal cancer (CRC) remains a highly fatal condition in part due to its resilience to treatment and its propensity to spread beyond the site of primary occurrence. One possible avenue for cancer to escape eradication is via stem-like cancer cells that, through phenotypic heterogeneity, are more resilient than other tumor constituents and are key contributors to cancer growth and metastasis. These proliferative tumor cells are theorized to possess many properties akin to normal intestinal stem cells. Not only do these CRC “stem” cells demonstrate similar restorative ability, they also share many cell pathways and surface markers in common, as well as respond to the same key niche stimuli. With the improvement of techniques for epithelial stem cell identification, our understanding of CRC behavior is also evolving. Emerging evidence about cellular plasticity and epithelial mesenchymal transition are shedding light onto metastatic CRC processes and are also challenging fundamental concepts about unidirectional epithelial proliferation. This review aims to reappraise evidence supporting the existence and behavior of CRC stem cells, their relationship to normal stem cells, and their possible dependence on the stem cell niche.

Cardiac stem cells: Current knowledge and future prospects

Regenerative medicine is the field concerned with the repair and restoration of the integrity of damaged human tissues as well as whole organs.Since the inception of the field several decades ago,regenerative medicine therapies,namely stem cells,have received significant attention in preclinical studies and clinical trials.Apart from their known potential for differentiation into the various body cells,stem cells enhance the organ's intrinsic regenerative capacity by altering its environment,whether by exogenous injection or introducing their products that modulate endogenous stem cell function and fate for the sake of regeneration.Recently,research in cardiology has highlighted the evidence for the existence of cardiac stem and progenitor cells(CSCs/CPCs).The global burden of cardiovascular diseases’morbidity and mortality has demanded an in-depth understanding of the biology of CSCs/CPCs aiming at improving the outcome for an innovative therapeutic strategy.This review will discuss the nature of each of the CSCs/CPCs,their environment,their interplay with other cells,and their metabolism.In addition,important issues are tackled concerning the potency of CSCs/CPCs in relation to their secretome for mediating the ability to influence other cells.Moreover,the review will throw the light on the clinical trials and the preclinical studies using CSCs/CPCs and combined therapy for cardiac regeneration.Finally,the novel role of nanotechnology in cardiac regeneration will be explored.

Applications of scaffolds:Tools for enhancing the immunomodulation of mesenchymal stromal cells

Exogenously delivered mesenchymal stromal cells(MSCs)are therapeutically beneficial owing to their paracrine effect;they secrete various cytokines,nucleic acids,and proteins.Multiple bioengineering techniques can help MSC cultures to release secretomes by providing stem cell niche-like conditions(both structurally and functionally).Various scaffolds mimic the natural extracellular matrix(ECM)using both natural and synthetic polymers,providing favorable environments for MSC proliferation and differentiation.Depending on material properties,either topographically or elastically structured scaffolds can be fabricated.Three-dimensional scaffolds have tunable substrate rigidities and structures,aiding MSC cultivation.Decellularized ECM-derived hydrogels are similar to the natural ECM,thus improving the paracrine effects of MSCs.Here,we discuss recent research on the application of scaffolds to maximize the immunomodulatory function of MSCs.

The cellular niche for intestinal stem cells: ateam effort

The rapidly self-renewing epithelium in the mammalian intestine is maintained by multipotent intestinal stem cells(ISCs) located at the bottom of the intestinal crypt that are interspersed with Paneth cells in the small intestine andPaneth-like cells in the colon. The ISC compartment is also closely associated with a sub-epithelial compartmentthat contains multiple types of mesenchymal stromal cells. With the advances in single cell and gene editingtechnologies, rapid progress has been made for the identification and characterization of the cellular componentsof the niche microenvironment that is essential for self-renewal and differentiation of ISCs. It has becomeincreasingly clear that a heterogeneous population of mesenchymal cells as well as the Paneth cells collectivelyprovide multiple secreted niche signals to promote ISC self-renewal. Here we review and summarize recentadvances in the regulation of ISCs with a main focus on the definition of niche cells that sustain ISCs.

The perivascular niche of endometrial mesenchymal stromal/stem-like cells

Human endometrium is a unique adult tissue that undergoes cyclical shedding,repair,and regeneration during a woman’s reproductive life.Over the past 2 decades,tremendous progress has been made towards the identification and characterization of endometrial stromal stem/progenitor cells.The substantial regeneration of vascularized stroma in the endometrium during the proliferative stages of each menstrual cycle is likely to be mediated by endometrial mesenchymal stromal/stem cells.This review focuses on the perivascular niche for CD140b^(+)CD146^(+)pericytes and SUSD2^(+)perivascular cells.The identity,characteristics,and underlying mechanisms of uterine regeneration are also discussed.

Cancer stem cells in glioblastoma—molecular signaling and therapeutic targeting

Glioblastomas(GBMs)are highly lethal primary brain tumors.Despite current therapeutic advances in other solid cancers,the treatment of these malignant gliomas remains essentially palliative.GBMs are extremely resistant to conventional radiation and chemotherapies.We and others have demonstrated that a highly tumorigenic subpopulation of cancer cells called GBM stem cells(GSCs)promotes therapeutic resistance.We also found that GSCs stimulate tumor angiogenesis by expressing elevated levels of VEGF and contribute to tumor growth,which has been translated into a useful therapeutic strategy in the treatment of recurrent or progressive GBMs.Furthermore,stem cell-like cancer cells(cancer stem cells)have been shown to promote metastasis.Although GBMs rarely metastasize beyond the central nervous system,these highly infiltrative cancers often invade into normal brain tissues preventing surgical resection,and GSCs display an aggressive invasive phenotype.These studies suggest that targeting GSCs may effectively reduce tumor recurrence and significantly improve GBM treatment.Recent studies indicate that cancer stem cells share core signaling pathways with normal somatic or embryonic stem cells,but also display critical distinctions that provide important clues into useful therapeutic targets.In this review,we summarize the current understanding and advances in glioma stem cell research,and discuss potential targeting strategies for future development of anti-GSC therapies.

Mapping bone marrow niches of disseminated tumor cells

Breast cancer cells may disseminate early, before tumor diagnosis. Disseminated tumor cells, or DTCs, reside in the bone marrow, and may persist for years or even decades. Some of these cells may be re-activated to resume aggressive growth, and eventually become overt bone metastases. Recent studies have begun to shed light on this complicated process and revealed multiple steps and intermediate states of colonizing DTCs. However, how cancer-host interactions evolve during this process needs to be further understood. Most of our current knowledge of the bone microenvironment is obtained through studies looking for the hematopoietic stem cell(HSC) niche. Although this long-standing question has not yet been resolved, our search for the HSC niche has resulted in a detailed map of various cell types in the bone marrow. Furthermore, various techniques used to find the HSC niche may also be adapted for finding the cancer cell niche. In this article, we will review the recent progress in both the DTC and HSC areas with a focus on their potential microenvironment niches. We will also discuss how to apply what we have learned from HSC studies to map DTCs in the bone context. We hope to stimulate thoughts and ideas to further elucidate the bone colonization process, and develop potential therapeutic interventions.

Towards a multiscale model of colorectal cancer

Colorectal cancer (CRC) is one of the best characterised cancers, with extensive data documenting the sequential gene mutations that underlie its development. Complementary datasets are also being generated describing changes in protein and RNA expression, tumour biology and clinical outcome. Both the quantity and the variety of information are inexorably increasing and there is now an accompanying need to integrate these highly disparate datasets. In this article we aim to explain why we believe that mathematical modelling represents a natural tool or language with which to integrate these data and, in so doing, to provide insight into CRC.

Function and regulation of muscle stem cells in skeletal muscle development and regeneration:a narrative review

Skeletal muscle plays an essential role in generating the mechanical force necessary to support the movement of our body and daily exercise. Compared with cardiac and smooth muscle, in mammals, skeletal muscle exhibits remarkable regenerative capacity in response to damage. Muscle stem cells, also known as satellite cells, directly contribute to regeneration. Here, we review primary and secondary myogenesis processes with a focus on muscle stem cells, as well as the function and regulation of muscle stem cells in adult muscle regeneration in mammals.