Recipient Glycemic Micro-environments Govern Therapeutic Effects of Mesenchymal Stem Cell Infusion on Osteopenia

Roles of Microenvironment on Mesenchymal Stem Cells Therapy for Osteoarthritis

Osteoarthritis (OA) induced microenvironmental alterations are a common and unavoidable phenomenon that greatly exacerbate the pathologic process of OA. Imbalances in the synthesis and degradation of cartilage extracellular matrix (ECM) have been reported to be associated with an adverse microenvironment. Stem cell therapy is a promising treatment for OA, and mesenchymal stem cells (MSCs) are the main cell sources for this therapy. With multispectral differentiation and immunomodulation, MSCs can effectively regulate the microenvironment of articular cartilage, ameliorate inflammation, promote regeneration of damaged cartilage, and ultimately alleviate OA symptoms. However, the efficacy of MSCs in the treatment of OA is greatly influenced by articular cavity microenvironments. This article reviews the five microenvironments of OA articular cavity, including inflammatory microenvironment, senescence microenvironment, hypoxic microenvironment, high glucose microenvironment and high lipid environment, focus on the positive and negative effects of OA microenvironments on the fate of MSCs. In this regard, we emphasize the mechanisms of the current use of MSCs in OA treatment, as well as its limitations and challenges.

AMPK, a hub for the microenvironmental regulation of bone homeostasis and diseases

AMP-activated protein kinase (AMPK), a crucial regulatory kinase, monitors energy levels, conserving ATP and boosting synthesis in low-nutrition, low-energy states. Its sensitivity links microenvironmental changes to cellular responses. As the primary support structure and endocrine organ, the maintenance, and repair of bones are closely associated with the microenvironment. While a series of studies have explored the effects of specific microenvironments on bone, there is lack of angles to comprehensively evaluate the interactions between microenvironment and bone cells, especially for bone marrow mesenchymal stem cells (BMMSCs) which mediate the differentiation of osteogenic lineage. It is noteworthy that accumulating evidence has indicated that AMPK may serve as a hub between BMMSCs and microenvironment factors, thus providing a new perspective for us to understand the biology and pathophysiology of stem cells and bone. In this review, we emphasize AMPK's pivotal role in bone microenvironment modulation via ATP, inflammation, reactive oxygen species (ROS), calcium, and glucose, particularly in BMMSCs. We further explore the use of AMPK-activating drugs in the context of osteoarthritis and osteoporosis. Moreover, building upon the foundation of AMPK, we elucidate a viewpoint that facilitates a comprehensive understanding of the dynamic relationship between the microenvironment and bone homeostasis, offering valuable insights for prospective investigations into stem cell biology and the treatment of bone diseases.

Scaffold Application for Bone Regeneration with Stem Cells in Dentistry: Literature Review

Bone tissue injuries within oral and dental contexts often present considerable challenges because traditional treatments may not be able to fully restore lost or damaged bone tissue. Novel approaches involving stem cells and targeted 3D scaffolds have been investigated in the search for workable solutions. The use of scaffolds in stem cell-assisted bone regeneration is a crucial component of tissue engineering techniques designed to overcome the drawbacks of traditional bone grafts. This study provides a detailed review of scaffold applications for bone regeneration with stem cells in dentistry. This review focuses on scaffolds and stem cells while covering a broad range of studies explaining bone regeneration in dentistry through the presentation of studies conducted in this field. The role of different stem cells in regenerative medicine is covered in great detail in the reviewed literature. These studies have addressed a wide range of subjects, including the effects of platelet concentrates during dental surgery or specific combinations, such as human dental pulp stem cells with scaffolds for animal model bone regeneration, to promote bone regeneration in animal models. Noting developments, research works consider methods to improve vascularization and explore the use of 3D-printed scaffolds, secretome applications, mesenchymal stem cells, and biomaterials for oral bone tissue regeneration. This thorough assessment outlines possible developments within these crucial regenerative dentistry cycles and provides insights and suggestions for additional study. Furthermore, alternative creative methods for regenerating bone tissue include biophysical stimuli, mechanical stimulation, magnetic field therapy, laser therapy, nutritional supplements and diet, gene therapy, and biomimetic materials. These innovative approaches offer promising avenues for future research and development in the field of bone tissue regeneration in dentistry.

Effects of Ibuprofen and Diclofenac Pre-Treatment on Viability and Apoptosis Processes in Human Dental Pulp Stem Cells

Background and Objectives: Stem cell-based regeneration strategies have shown therapeutic efficacy in various fields of regenerative medicine. These include bone healing after bone augmentation, often complicated by pain, which is managed by using nonsteroidal anti-inflammatory drugs (NSAIDs). However, information is limited about how NSAIDs affect the therapeutic potential of stem cells. Materials and Methods: We investigated the effects of ibuprofen and diclofenac on the characteristics, morphology, and immunophenotype of human mesenchymal stromal cells isolated from the dental pulp (DPSCs) and cultured in vitro, as well as their effects on the expression of angiogenic growth factors (VEGFA and HGF) and selected genes in apoptosis signalling pathways (BAX, BAK, CASP3, CASP9, and BCL2). Results: Ibuprofen and diclofenac significantly reduced the viability of DPSCs, while the expression of mesenchymal stem cell surface markers was unaffected. Both ibuprofen and diclofenac treatment significantly upregulated the expression of HGF, while the expression of VEGFA remained unchanged. Ibuprofen significantly altered the expression of several apoptosis-related genes, including the upregulation of CASP9 and BCL2, with decreased CASP3 expression. BAK, CASP3, CASP9, and BCL2 expressions were significantly increased in the diclofenac-treated DPSCs, while no difference was demonstrated in BAX expression. Conclusions: Our results suggest that concomitant use of the NSAIDs ibuprofen or diclofenac with stem cell therapy may negatively impact cell viability and alter the expression of apoptosis-related genes, affecting the efficacy of stem cell therapy.

Chitosan modified with PAP as a promising delivery system for melatonin in the treatment of osteoporosis: targeting the divalent metal transporter 1

The demands for novel and efficient therapies have gradually increased with the rising concerns of osteoporosis (OP). The most popular method in promoting bone regeneration during osteoporotic conditions consists of loading bioactive materials with different drugs to treat osteoporotic bones by either promoting the process of osteogenesis, or by inhibiting the activity of osteoclasts. By analyzing single cell sequencing results, we found that divalent metal transporter 1 (DMT1) played a role in OP. Based on our previous results, we found that melatonin (MT) suppressed expression of DMT1 induced by high glucose during OP, so we determined the efficacy of MT for the treatment of OP. However, the clinical effects of MT on OP were unsatisfactory. To enhance its biological efficacy, we combined MT with porous gelatin chitosan (chitosan) and the conductive material, PLA-b-AP-b-PLA (PAP), then determined how MT incorporation in chitosan@PAP nanoparticles affected the ability to promote MC3T3-E1 osteogenesis and mineralization, both in vitro and in vivo. The results confirmed the effect of MT on DMT1. We then prepared and characterized composites prepared as nanofibers, and determined the efficacy of MT combined with chitosan-PAP modified hydrogels as a slow-release system in a femur model of osteoporosis mice, with associated properties suitable for bone tissue engineering. The results indicated that MT-loaded chitosan@PAP nanospheres showed favorable osteogenic functions, both in vivo and in vitro, providing a practical solution for bone regeneration for OP patients.

Autonomic neural regulation in mediating the brain-bone axis: mechanisms and implications for regeneration under psychological stress

Efficient regeneration of bone defects caused by disease or significant trauma is a major challenge in current medicine, which is particularly difficult yet significant under the emerging psychological stress in the modern society. Notably, the brain-bone axis has been proposed as a prominent new concept in recent years, among which autonomic nerves act as an essential and emerging skeletal pathophysiological factor related to psychological stress. Studies have established that sympathetic cues lead to impairment of bone homeostasis mainly through acting on mesenchymal stem cells (MSCs) and their derivatives with also affecting the hematopoietic stem cell (HSC)-lineage osteoclasts, and the autonomic neural regulation of stem cell lineages in bone is increasingly recognized to contribute to the bone degenerative disease, osteoporosis. This review summarizes the distribution characteristics of autonomic nerves in bone, introduces the regulatory effects and mechanisms of autonomic nerves on MSC and HSC lineages, and expounds the crucial role of autonomic neural regulation on bone physiology and pathology, which acts as a bridge between the brain and the bone. With the translational perspective, we further highlight the autonomic neural basis of psychological stress-induced bone loss and a series of pharmaceutical therapeutic strategies and implications toward bone regeneration. The summary of research progress in this field will add knowledge to the current landscape of inter-organ crosstalk and provide a medicinal basis for the achievement of clinical bone regeneration in the future.

Hyperoside alleviates photoreceptor degeneration by preventing cell senescence through AMPK-ULK1 signaling

Vision loss and blindness are frequently caused by photoreceptor degeneration, for example in age-related macular degeneration and retinitis pigmentosa. However, there is no effective medicine to treat these photoreceptor degeneration-related diseases. Cell senescence is a common phenotype in many diseases; however, few studies have reported whether it occurs in photoreceptor degeneration diseases. Herein, we identified that cell senescence is associated with photoreceptor degeneration induced by N-methyl-N-nitrosourea (MNU, a commonly used photoreceptor degeneration model), presented as increased senescence-associated β-galactosidase activity, DNA damage, oxidative stress and inflammation-related cytokine Interleukin 6 (IL6), and upregulation of cyclin p21 or p16. These results suggested that visual function might be protected using anti-aging treatment. Furthermore, Hyperoside is reported to help prevent aging in various organs. In this study, we showed that Hyperoside, delivered intravitreally, alleviated photoreceptor cell senescence and ameliorated the functional and morphological degeneration of the retina in vivo and in vitro. Importantly, Hyperoside attenuated the MNU-induced injury and aging of photoreceptors via AMPK-ULK1 signaling inhibition. Taken together, our results demonstrated that Hyperoside can prevent MNU-induced photoreceptor degeneration by inhibiting cell senescence via the AMPK-ULK1 pathway.

Region-specific sympatho-adrenergic regulation of specialized vasculature in bone homeostasis and regeneration

Type H vessels couple angiogenesis with osteogenesis, while sympathetic cues regulate vascular and skeletal function. The crosstalk between sympathetic nerves and type H vessels in bone remains unclear. Here, we first identify close spatial connections between sympathetic nerves and type H vessels in bone, particularly in metaphysis. Sympathoexcitation, mimicked by isoproterenol (ISO) injection, reduces type H vessels and bone mass. Conversely, beta-2-adrenergic receptor (ADRB2) deficiency maintains type H vessels and bone mass in the physiological condition. In vitro experiments reveal indirect sympathetic modulation of angiogenesis via paracrine effects of mesenchymal stem cells (MSCs), which alter the transcription of multiple angiogenic genes in endothelial cells (ECs). Furthermore, Notch signaling in ECs underlies sympathoexcitation-regulated type H vessel formation, impacting osteogenesis and bone mass. Finally, propranolol (PRO) inhibits beta-adrenergic activity and protects type H vessels and bone mass against estrogen deficiency. These findings unravel the specialized neurovascular coupling in bone homeostasis and regeneration.

Engineering a Pro-Osteogenic Secretome through the Transient Silencing of the Gene Encoding Secreted Frizzled Related Protein 1

The evidence sustaining the regenerative properties of mesenchymal stem cells' (MSCs) secretome has prompted a paradigm change, where MSCs have shifted from being considered direct contributors to tissue regeneration toward being seen as cell factories for producing biotech medicines. We have previously designed a method to prime MSCs towards osteogenic differentiation by silencing the Wnt/β-Catenin inhibitor Sfpr1. This approach produces a significant increase in bone formation in osteoporotic mice. In this current work, we set to investigate the contribution of the secretome from the MSCs where Sfrp1 has been silenced, to the positive effect seen on bone regeneration in vivo. The conditioned media (CM) of the murine MSCs line C3H10T1/2, where Sfrp1 has been transiently silenced (CM-Sfrp1), was found to induce, in vitro, an increase in the osteogenic differentiation of this same cell line, as well as a decrease of the expression of the Wnt inhibitor Dkk1 in murine osteocytes ex vivo. A reduction in the RANKL/OPG ratio was also detected ex vivo, suggesting a negative effect of CM-Sfrp1 on osteoclastogenesis. Moreover, this CM significantly increases the mineralization of human primary MSCs isolated from osteoportotic patients in vitro. Proteomic analysis identified enrichment of proteins involved in osteogenesis within the soluble and vesicular fractions of this secretome. Altogether, we demonstrate the pro-osteogenic potential of the secretome of MSCs primmed in this fashion, suggesting that this is a valid approach to enhance the osteo-regenerative properties of MSCs' secretome.

Mesenchymal condensation in tooth development and regeneration: a focus on translational aspects of organogenesis

The teeth are vertebrate-specific, highly specialized organs performing fundamental functions of mastication and speech, the maintenance of which is crucial for orofacial homeostasis and is further linked to systemic health and human psychosocial well-being. However, with limited ability for self-repair, the teeth can often be impaired by traumatic, inflammatory, and progressive insults, leading to high prevalence of tooth loss and defects worldwide. Regenerative medicine holds the promise to achieve physiological restoration of lost or damaged organs, and in particular an evolving framework of developmental engineering has pioneered functional tooth regeneration by harnessing the odontogenic program. As a key event of tooth morphogenesis, mesenchymal condensation dictates dental tissue formation and patterning through cellular self-organization and signaling interaction with the epithelium, which provides a representative to decipher organogenetic mechanisms and can be leveraged for regenerative purposes. In this review, we summarize how mesenchymal condensation spatiotemporally assembles from dental stem cells (DSCs) and sequentially mediates tooth development. We highlight condensation-mimetic engineering efforts and mechanisms based on ex vivo aggregation of DSCs, which have achieved functionally robust and physiologically relevant tooth regeneration after implantation in animals and in humans. The discussion of this aspect will add to the knowledge of development-inspired tissue engineering strategies and will offer benefits to propel clinical organ regeneration.

Residual periodontal ligament in the extraction socket promotes the dentin regeneration potential of DPSCs in the rabbit jaw

BACKGROUND

Because of the low regeneration efficiency and unclear underlying molecular mechanism, tooth regeneration applications are limited. In this study, we explored the influence of residual periodontal ligament on the dentin regeneration potential of dental pulp stem cells (DPSCs) in the jaw.

METHODS

To establish a tooth regeneration model, the incisors of New Zealand white rabbits were extracted while preserving residual periodontal ligament, followed by the implantation of DPSCs. After 3 months, micro-computed tomography (micro-CT), stereomicroscopy and scanning electron microscopy (SEM) were used to observe the volume, morphology and microstructure of regenerated tissue. Histological staining and immunostaining analyses were used to observe the morphological characteristics and expression of the dentin-specific proteins DMP1 and DSPP. To explore the mechanism, DPSCs and periodontal ligament stem cells (PDLSCs) were cocultured in vitro, and RNA was collected from the DPSCs for RNA-seq and bioinformatic analysis.

RESULTS

The results of micro-CT and stereomicroscopy showed that the number of sites with regeneration and the volume of regenerated tissue in the DPSCs/PDL group (6/8, 1.07 ± 0.93 cm³) were larger than those in the DPSCs group (3/8, 0.23 ± 0.41 cm³). The results of SEM showed that the regenerated dentin-like tissue in the DPSCs and DPSCs/PDL groups contained dentin tubules. Haematoxylin and eosin staining and immunohistochemical staining indicated that compared with the DPSCs group, the DPSCs/PDL group showed more regular regenerated tissue and higher expression levels of the dentin-specific proteins DMP1 and DSPP (DMP1: P = 0.02, DSPP: P = 0.01). RNA-seq showed that the coculture of DPSCs with PDLSCs resulted in the DPSCs differentially expressing 427 mRNAs (285 upregulated and 142 downregulated), 41 lncRNAs (26 upregulated and 15 downregulated), 411 circRNAs (224 upregulated and 187 downregulated), and 19 miRNAs (13 upregulated and 5 downregulated). Bioinformatic analysis revealed related Gene Ontology function and signalling pathways, including extracellular matrix (ECM), tumour necrosis factor (TNF) signalling and chemokine signalling pathways.

CONCLUSIONS

Residual periodontal ligament in the extraction socket promotes the dentin regeneration potential of DPSCs in the jaw. RNA-seq and bioinformatic analysis revealed that ECM, TNF signalling and chemokine signalling pathways may represent the key factors and signalling pathways.

Mesenchymal stem cells: Emerging concepts and recent advances in their roles in organismal homeostasis and therapy

Stem cells play a crucial role in re-establishing homeostasis in the body, and the search for mechanisms by which they interact with the host to exert their therapeutic effects remains a key question currently being addressed. Considering their significant regenerative/therapeutic potential, research on mesenchymal stem cells (MSCs) has experienced an unprecedented advance in recent years, becoming the focus of extensive works worldwide to develop cell-based approaches for a variety of diseases. Initial evidence for the effectiveness of MSCs therapy comes from the restoration of dynamic microenvironmental homeostasis and endogenous stem cell function in recipient tissues by systemically delivered MSCs. The specific mechanisms by which the effects are exerted remain to be investigated in depth. Importantly, the profound cell-host interplay leaves persistent therapeutic benefits that remain detectable long after the disappearance of transplanted MSCs. In this review, we summarize recent advances on the role of MSCs in multiple disease models, provide insights into the mechanisms by which MSCs interact with endogenous stem cells to exert therapeutic effects, and refine the interconnections between MSCs and cells fused to damaged sites or differentiated into functional cells early in therapy.

Clinical Potential of Dental Pulp Stem Cells in Pulp Regeneration: Current Endodontic Progress and Future Perspectives

Dental caries is a common disease that not only destroys the rigid structure of the teeth but also causes pulp necrosis in severe cases. Once pulp necrosis has occurred, the most common treatment is to remove the damaged pulp tissue, leading to a loss of tooth vitality and increased tooth fragility. Dental pulp stem cells (DPSCs) isolated from pulp tissue exhibit mesenchymal stem cell-like characteristics and are considered ideal candidates for regenerating damaged dental pulp tissue owing to their multipotency, high proliferation rate, and viability after cryopreservation. Importantly, DPSCs do not elicit an allogeneic immune response because they are non-immunogenic and exhibit potent immunosuppressive properties. Here, we provide an up-to-date review of the clinical applicability and potential of DPSCs, as well as emerging trends in the regeneration of damaged pulp tissue. In addition, we suggest the possibility of using DPSCs as a resource for allogeneic transplantation and provide a perspective for their clinical application in pulp regeneration.

Sympathetic Neurostress Drives Osteoblastic Exosomal MiR-21 Transfer to Disrupt Bone Homeostasis and Promote Osteopenia

Innervation and extracellular vesicle secretion co-exist in the local tissue microenvironment for message transfer, but whether they are interconnected to regulate organ homeostasis remains unknown. Sympatho-adrenergic activation is implicated in stress-induced depression and leads to bone loss, but the mechanisms and therapeutics are incompletely elucidated. Here, it is revealed that sympathetic neurostress through the β_1/2 -adrenergic receptor (β1/2-AR) signaling triggers the transcription response of a microRNA, miR-21, in osteoblasts, which is transferred to osteoclast progenitors via exosomes for dictating osteoclastogenesis. After confirming that miR-21 deficiency retards the β1/2-AR agonist isoproterenol (ISO)-induced osteopenia, it is shown that the pharmacological inhibition of exosome release by two clinically-relevant drugs, dimethyl amiloride and omeprazole, suppresses osteoblastic miR-21 transfer and ameliorates bone loss under both ISO and chronic variable stress (CVS)-induced depression conditions. A targeted delivery approach to specifically silence osteoblastic miR-21 is further applied, which is effective in rescuing the bone remodeling balance and ameliorating ISO- and CVS-induced osteopenias. These results decipher a previously unrecognized paradigm that neural cues drive exosomal microRNA communication to regulate organ homeostasis and help to establish feasible strategies to counteract bone loss under psychological stresses.

Osteoinductive activity of bisdemethoxycurcumin and its synergistic protective effect with human amniotic mesenchymal stem cells against ovariectomy-induced osteoporosis mouse model

Osteoporosis is a common disease characterized by skeletal fragility and microarchitectural deterioration. However, existing conventional drugs exhibit limited efficacy and can elicit severe adverse effects; moreover, and novel stem cell-based therapies have not exhibited sufficient therapeutic efficacy. Our hypothesis is that an appropriate osteogenic inducer may improve their therapeutic efficacy. In this study, we found that bisdemethoxycurcumin (BDMC) stimulates the differentiation of human amniotic mesenchymal stem cells (hAMSCs) into osteoblasts without inducing cytotoxicity. Here BDMC enhances calcium deposition in hAMSCs, while promoting the expression of early and late markers of osteoblast differentiation, including ALP, runt-related transcription factor 2, osterix, COL1-α1, osteocalcin, and osteopontin at the transcriptional and translational levels. Mechanistically, BDMC was found to activate the JAK2/STAT3 pathway; whereas AG490 (JAK2/STAT3 pathway inhibitor) inhibited BDMC functioning. Subsequently, we found that the combinatorial therapy of BDMC and hAMSC had a positive synergistic effect on osteoporotic mouse model induced by bilateral ovariectomy, including inhibiting bone loss and bone resorption and improving bone micro-architecture. Moreover, BDMC inhibited production of the bone resorption markers C-terminal telopeptide of type I collagen, and tartrate resistant acid phosphatase, while promoting serum levels of bone formation markers OCN, and procollagen I N-terminal propeptide. BDMC also improved liver and kidney function in osteoporotic mouse model. Collectively, BDMC improved osteoporosis by enhancing hAMSC osteogenesis and exhibited a protective effect on liver and kidney function in an osteoporotic mouse model. Hence, BDMC may serve as an effective adjuvant, and combined therapy with hAMSCs is a promising new approach toward osteoporosis treatment.

Sex Differences in Mesenchymal Stem Cell Therapy With Gelatin-Based Microribbon Hydrogels in a Murine Long Bone Critical-Size Defect Model

Mesenchymal stem cell (MSC)-based therapy and novel biomaterials are promising strategies for healing of long bone critical size defects. Interleukin-4 (IL-4) over-expressing MSCs within a gelatin microribbon (µRB) scaffold was previously shown to enhance the bridging of bone within a critical size femoral bone defect in male Balb/c mice. Whether sex differences affect the healing of this bone defect in conjunction with different treatments is unknown. In this study, we generated 2-mm critical-sized femoral diaphyseal bone defects in 10–12-week-old female and male Balb/c mice. Scaffolds without cells and with unmodified MSCs were implanted immediately after the primary surgery that created the bone defect; scaffolds with IL-4 over-expressing MSCs were implanted 3 days after the primary surgery, to avoid the adverse effects of IL-4 on the initial inflammatory phase of fracture healing. Mice were euthanized 6 weeks after the primary surgery and femurs were collected. MicroCT (µCT), histochemical and immunohistochemical analyses were subsequently performed of the defect site. µRB scaffolds with IL-4 over-expressing MSCs enhanced bone healing in both female and male mice. Male mice showed higher measures of bone bridging and increased alkaline phosphatase (ALP) positive areas, total macrophages and M2 macrophages compared with female mice after receiving scaffolds with IL-4 over-expressing MSCs. Female mice showed higher Tartrate-Resistant Acid Phosphatase (TRAP) positive osteoclast numbers compared with male mice. These results demonstrated that sex differences should be considered during the application of MSC-based studies of bone healing.

Apoptotic vesicles restore liver macrophage homeostasis to counteract type 2 diabetes

Apoptosis is a naturally occurring process generating plenty of apoptotic vesicles (apoVs), but the feature, fate and function of apoVs remain largely unknown. Notably, as an appealing source for cell therapy, mesenchymal stem cells (MSCs) undergo necessary apoptosis and release apoVs during therapeutic application. In this study, we characterized and used MSC‐derived apoVs to treat type 2 diabetes (T2D) mice, and we found that apoVs were efferocytosed by macrophages and functionally modulated liver macrophage homeostasis to counteract T2D. We showed that apoVs can induce macrophage reprogramming at the transcription level in an efferocytosis‐dependent manner, leading to inhibition of macrophage accumulation and transformation of macrophages towards an anti‐inflammation phenotype in T2D liver. At the molecular level, we discovered that calreticulin (CRT) was exposed on the surface of apoVs to act as a critical ‘eat‐me’ signal mediating apoV efferocytosis and macrophage regulatory effects. Importantly, we demonstrated that CRT‐mediated efferocytosis of MSC‐derived apoVs contributes to T2D therapy with alleviation of T2D phenotypes including glucose intolerance and insulin resistance. These findings uncover that functional efferocytosis of apoVs restores liver macrophage homeostasis and ameliorates T2D.

LRRc17 controls BMSC senescence via mitophagy and inhibits the therapeutic effect of BMSCs on ovariectomy-induced bone loss

Senescence of bone marrow-derived mesenchymal stem cells (BMSCs) has been widely reported to be closely correlated with aging-related diseases, including osteoporosis (OP). Moreover, the beneficial functions of BMSCs decline with age, limiting their therapeutic efficacy in OP. In the present study, using RNA sequencing (RNA-Seq), we found that leucine-rich repeat containing 17 (LRRc17) expression in BMSCs was highly positively correlated with age. Therefore, we investigated whether LRRc17 knockdown could rejuvenate aged MSCs and increase their therapeutic efficacy in OP. Consistent with the RNA-Seq results, the protein expression of LRRc17 in senescent BMSCs was significantly increased, whereas LRRc17 knockdown inhibited cell apoptosis and reduced the expression of age-related proteins and G2 and S phase quiescence. Furthermore, LRRc17 knockdown shifted BMSCs from adipogenic to osteogenic differentiation, indicating the critical role of LRRc17 in BMSC senescence and differentiation. Additionally, similar to rapamycin (RAPA) treatment, LRRc17 knockdown activated mitophagy via inhibition of the mTOR/PI3K pathway, which consequently reduced mitochondrial dysfunction and inhibited BMSC senescence. However, the effects of LRRc17 knockdown were significantly blocked by the autophagy inhibitor hydroxychloroquine (HCQ), demonstrating that LRRc17 knockdown prevented BMSC senescence by activating mitophagy. In vivo, compared with untransfected aged mouse-derived BMSCs (O-BMSCs), O-BMSCs transfected with sh-LRRc17 showed effective amelioration of ovariectomy (OVX)-induced bone loss. Collectively, these results indicated that LRRc17 knockdown rejuvenated senescent BMSCs and thus enhanced their therapeutic efficacy in OP by activating autophagy.

Targeting reactive oxygen species in stem cells for bone therapy

Reactive oxygen species (ROS) have emerged as key players in regulating the fate and function of stem cells from both non-hematopoietic and hematopoietic lineages in bone marrow, and thus affect the osteoblastogenesis-osteoclastogenesis balance and bone homeostasis. Accumulating evidence has linked ROS and associated oxidative stress with the progression of bone disorders, and ROS-based therapeutic strategies have appeared to achieve favorable outcomes in bone. We review current knowledge of the multifactorial roles and mechanisms of ROS as a target in bone pathology. In addition, we discuss emerging ROS-based therapeutic strategies that show potential for bone therapy. Finally, we highlight the opportunities and challenges facing ROS-targeted stem cell therapeutics for improving bone health.

Mesenchymal stromal cell-mediated immune regulation: A promising remedy in the therapy of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a major threat to global public health, with increasing prevalence as well as high morbidity and mortality, to which immune dysfunction has been recognized as a crucial contributor. Mesenchymal stromal cells (MSCs), obtained from various sources and possessing potent immunomodulatory abilities, have displayed great therapeutic potential for T2DM. Interestingly, the immunomodulatory capabilities of MSCs are endowed and plastic. Among the multiple mechanisms involved in MSC-mediated immune regulation, the paracrine effects of MSCs have attracted much attention. Of note, extracellular vesicles (EVs), an important component of MSC secretome, have emerged as pivotal mediators of their immunoregulatory effects. Particularly, the necrobiology of MSCs, especially apoptosis, has recently been revealed to affect their immunomodulatory functions in vivo. In specific, a variety of preclinical studies have demonstrated the beneficial effects of MSCs on improving islet function and ameliorating insulin resistance. More importantly, clinical trials have further uncovered the therapeutic potential of MSCs for T2DM. In this review, we outline current knowledge regarding the plasticity and underlying mechanisms of MSC-mediated immune modulation, focusing on the paracrine effects. We also summarize the applications of MSC-based therapies for T2DM in both preclinical studies and clinical trials, with particular emphasis on the modulation of immune system.

Photoreceptor protection by mesenchymal stem cell transplantation identifies exosomal MiR-21 as a therapeutic for retinal degeneration

Photoreceptor apoptosis is recognized as one key pathogenesis of retinal degeneration, the counteraction of which represents a promising approach to safeguard visual function. Recently, mesenchymal stem cell transplantation (MSCT) has demonstrated immense potential to treat ocular disorders, in which extracellular vesicles (EVs), particularly exosomes, have emerged as effective ophthalmological therapeutics. However, whether and how MSCT protects photoreceptors against apoptotic injuries remains largely unknown. Here, we discovered that intravitreal MSCT counteracted photoreceptor apoptosis and alleviated retinal morphological and functional degeneration in a mouse model of photoreceptor loss induced by N-methyl-N-nitrosourea (MNU). Interestingly, effects of MSCT were inhibited after blockade of exosomal generation by GW4869 preconditioning. Furthermore, MSC-derived exosomal transplantation (EXOT) effectively suppressed MNU-provoked photoreceptor injury. Notably, therapeutic efficacy of MSCT and EXOT on MNU-induced retinal degeneration was long-lasting as photoreceptor preservance and retinal maintenance were detected even after 1–2 months post to injection for only once. More importantly, using a natural occurring retinal degeneration model caused by a nonsense mutation of Phosphodiesterase 6b gene (Pde6b^mut), we confirmed that MSCT and EXOT prevented photoreceptor loss and protected long-term retinal function. In deciphering therapeutic mechanisms regarding potential exosome-mediated communications, we identified that miR-21 critically maintained photoreceptor viability against MNU injury by targeting programmed cell death 4 (Pdcd4) and was transferred from MSC-derived exosomes in vivo for functional regulation. Moreover, miR-21 deficiency aggravated MNU-driven retinal injury and was restrained by EXOT. Further experiments revealed that miR-21 mediated therapeutic effects of EXOT on MNU-induced photoreceptor apoptosis and retinal dysfunction. These findings uncovered the efficacy and mechanism of MSCT-based photoreceptor protection, indicating exosomal miR-21 as a therapeutic for retinal degeneration.

Advancing application of mesenchymal stem cell-based bone tissue regeneration

Reconstruction of bone defects, especially the critical-sized defects, with mechanical integrity to the skeleton is important for a patient's rehabilitation, however, it still remains challenge. Utilizing biomaterials of human origin bone tissue for therapeutic purposes has provided a facilitated approach that closely mimics the critical aspects of natural bone tissue with regard to its properties. However, not only efficacious and safe but also cost-effective and convenient are important for regenerative biomaterials to achieve clinical translation and commercial success. Advances in our understanding of regenerative biomaterials and their roles in new bone formation potentially opened a new frontier in the fast-growing field of regenerative medicine. Taking inspiration from the role and multicomponent construction of native extracellular matrix (ECM) for cell accommodation, the ECM-mimicking biomaterials and the naturally decellularized ECM scaffolds were used to create new tissues for bone restoration. On the other hand, with the going deep in understanding of mesenchymal stem cells (MSCs), they have shown great promise to jumpstart and facilitate bone healing even in diseased microenvironments with pharmacology-based endogenous MSCs rescue/mobilization, systemic/local infusion of MSCs for cytotherapy, biomaterials-based approaches, cell-sheets/-aggregates technology and usage of subcellular vesicles of MSCs to achieve scaffolds-free or cell-free delivery system, all of them have been shown can improve MSCs-mediated regeneration in preclinical studies and several clinical trials. Here, following an overview discussed autogenous/allogenic and ECM-based bone biomaterials for reconstructive surgery and applications of MSCs-mediated bone healing and tissue engineering to further offer principles and effective strategies to optimize MSCs-based bone regeneration.

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Focusing on MSCs based bone regeneration.

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Discussed cytotherapy, cell-free therapies and cell-aggregates technology in detail.

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Stating the approaches of MSCs in diseased microenvironments.

Bone progeria diminished the therapeutic effects of bone marrow mesenchymal stem cells on retinal degeneration

Senescence is closely related to the occurrence of retinal degeneration. Recent studies have shown that bone marrow mesenchymal stem cells (BMMSCs) have significant therapeutic effects on retinal degeneration, While BMMSCs suffer from functional decline in bone aging. Whether senescence affects BMMSCs therapy on retinal degeneration remains unknown. Here, we applied the previously established bone progeria animal model, the senescence-accelerated mice-prone 6 (SAMP6) strain, and surprisingly discovered that SAMP6 mice demonstrated retinal degeneration at 6 months old. Furthermore, BMMSCs derived from SAMP6 mice failed to prevent MNU-induced retinal degeneration in vivo. As expected, BMMSCs from SAMP6 mice exhibited impairment in the differentiation capacities, compared to those from the age-matched senescence-accelerated mice-resistant 1 (SAMR1) strain. Moreover, BMMSCs from SAMR1 mice counteracted MNU-induced retinal degeneration, with increased expression of the retina survival hallmark, N-myc downstream regulated gene 2 (NDRG2). Taken together, these findings reveal that bone progeria diminished the therapeutic effects of BMMSC on retinal degeneration.

Local SDF-1α application enhances the therapeutic efficacy of BMSCs transplantation in osteoporotic bone healing

Bone defect healing is markedly impaired in osteoporotic patient due to poor bone regeneration ability. Stromal cell derived factor-1α (SDF-1α) plays a pivotal role in the repair of various injured tissues including bone. Here, we definite that SDF-1α hydrogels potentiates in vivo osteogenesis of bone marrow-derived stromal stem cells (BMSCs) in osteoporosis. The characteristics of rat primary BMSCs including superficial markers by flow cytometry and multi-lineage differentiation by induction were determined. At different time intervals, the release media from the SDF-1α-releasing hydrogels were collected to identificate SDF-1α exhibited a sustained release profile and maintained its bioactivity after release from the hydrogels to stimulate chemotaxis of BMSCs in a time dependent manner. Bilateral alveolar defects were operated in ovariectomized (OVX) rats and repaired with systemic BMSCs transplantation with or without the hydrogels. Local administration of SDF-1α significantly enhanced BMSCs recruitment and promoted more bone regeneration as well as the expression of OCN and Runx2 compared with the effect of BMSCs transplantation alone. Moreover, after BMSCs transplantation with SDF-1α delivery, macrophage polarization was promoted toward the M2 phenotype, that is identified as an important symbol in tissue regeneration process. Taken together, local SDF-1α application enhances the efficacy of BMSCs transplantation therapy in osteoporotic bone healing, suggesting clinical potential of SDF-1α to serve as a therapeutic drug target for osteoporosis treatment.

The neural system regulates bone homeostasis via mesenchymal stem cells: a translational approach

Large bone reconstruction is a major clinical issue associated with several challenges, and autograft is the main method for reconstructing large defects of maxillofacial bone. However, postoperative osteoporosis of the bone graft, even with sufficient vascularization, remains a primary problem. Therefore, better understanding of the mechanisms and clinical translation of bone homeostasis is required. Neuronal innervation of the bone is an emerging research topic, especially with regards to the role of peripheral nerves in regulating bone homeostasis. Moreover, sensory and autonomic nerves regulate this process via different types of neurotransmitters, but the specific mechanism is still elusive. In this review article, the current understanding of the interaction between the peripheral nerve and the skeleton system is summarized, with a particular focus on bone marrow mesenchymal stem cells (BMMSCs), except for osteoblasts and osteoclasts. The novel application of nerve-based bone regeneration via BMMSCs may provide a new strategy in tissue engineering and clinical treatment of osteoporosis and bone disorders.

Diabetes-Induced NF-κB Dysregulation in Skeletal Stem Cells Prevents Resolution of Inflammation

Type 1 diabetes (T1D) imposes a significant health burden by negatively affecting tissue regeneration during wound healing. The adverse effect of diabetes is attributed to high levels of inflammation, but the cellular mechanisms responsible remain elusive. In this study, we show that intrinsic skeletal stem cells (SSCs), a subset of mesenchymal stem cells, are essential for resolution of inflammation to occur during osseous healing by using genetic approaches to selectively ablate SSCs. T1D caused aberrant nuclear factor-κB (NF-κB) activation in SSCs and substantially enhanced inflammation in vivo. Constitutive or tamoxifen-induced inhibition of NF-κB in SSCs rescued the impact of diabetes on inflammation, SSC expansion, and tissue formation. In contrast, NF-κB inhibition in chondrocytes failed to reverse the effect of T1D. Mechanistically, diabetes caused defective proresolving macrophage (M2) polarization by reducing TGF-β1 expression by SSCs, which was recovered by NF-κB inhibition or exogenous TGF-β1 treatment. These data identify an underlying mechanism for altered healing in T1D and demonstrate that diabetes induces NF-κB hyperactivation in SSCs to disrupt their ability to modulate M2 polarization and resolve inflammation.

Synergistic Improvement in Children with Cerebral Palsy Who Underwent Double-Course Human Wharton's Jelly Stem Cell Transplantation

Background

Our previous studies confirmed that human Wharton's Jelly stem cell (hWJSC) transplantation improved motor function in children with spastic cerebral palsy (CP). This study investigated the dose-effect relationship between the transplanted cell dosage and efficacy in CP children.

Methods

CP children who received one- or two-course (four or eight times lumbar puncture, 4 or 8 × 10⁷ hWJSCs) cell therapy were recruited into this study. Assessments of motor function were performed according to scales for gross motor function measurement (GMFM) and fine motor function measurement (FMFM). The measurement data obtained in the two different groups were analyzed by t-test. Univariate repeated measures analysis of variance was used to compare the data obtained at baseline and 6 or 12 months posttransplantation and met the conditions for Mauchly's sphericity test.

Results

The results for fifty-seven pediatric CP patients (including 35 male and 22 female patients) who completed follow-up showed that gross and fine motor functions improved after cell therapy. Interestingly, the GMFM and FMFM scores in patients who received one course of transplantation were significantly increased at 6 months after treatment. Moreover, another course of transplantation further improved gross and fine motor function in children. The scores for GMFM and FMFM were significantly higher at 6 months posttransplantation than at baseline and showed a linear upward trend. There was no gender difference in GMFM. Interestingly, there was a significant difference between male and female patients in the B and C dimensions of FMFM. These results reveal a gender-related susceptibility to stem cell therapy, especially for movement capability of the upper extremity joint and grasping ability. Similarly, in the group aged ≤3 years old, the improvement observed in dimension A (lying and rolling) of GMFM was nearly exponential and showed a quadratic trend. The results for FMFM were similar to those for GMFM. Moreover, the improvement in motor function was not age dependent.

Conclusions

In this study, our data collectively reveal that CP children display sex- or age-dependent responses to hWJSC therapy; these results shed light on the clinical utility of this approach in specific populations.

Stem cell-based bone and dental regeneration: a view of microenvironmental modulation

In modern medicine, bone and dental loss and defects are common and widespread morbidities, for which regenerative therapy has shown great promise. Mesenchymal stem cells, obtained from various sources and playing an essential role in organ development and postnatal repair, have exhibited enormous potential for regenerating bone and dental tissue. Currently, mesenchymal stem cells (MSCs)-based bone and dental regeneration mainly includes two strategies: the rescue or mobilization of endogenous MSCs and the application of exogenous MSCs in cytotherapy or tissue engineering. Nevertheless, the efficacy of MSC-based regeneration is not always fulfilled, especially in diseased microenvironments. Specifically, the diseased microenvironment not only impairs the regenerative potential of resident MSCs but also controls the therapeutic efficacy of exogenous MSCs, both as donors and recipients. Accordingly, approaches targeting a diseased microenvironment have been established, including improving the diseased niche to restore endogenous MSCs, enhancing MSC resistance to a diseased microenvironment and renormalizing the microenvironment to guarantee MSC-mediated therapies. Moreover, the application of extracellular vesicles (EVs) as cell-free therapy has emerged as a promising therapeutic strategy. In this review, we summarize current knowledge regarding the tactics of MSC-based bone and dental regeneration and the decisive role of the microenvironment, emphasizing the therapeutic potential of microenvironment-targeting strategies in bone and dental regenerative medicine.

Gender-independent efficacy of mesenchymal stem cell therapy in sex hormone-deficient bone loss via immunosuppression and resident stem cell recovery

Osteoporosis develops with high prevalence in both postmenopausal women and hypogonadal men. Osteoporosis results in significant morbidity, but no cure has been established. Mesenchymal stem cells (MSCs) critically contribute to bone homeostasis and possess potent immunomodulatory/anti-inflammatory capability. Here, we investigated the therapeutic efficacy of using an infusion of MSCs to treat sex hormone-deficient bone loss and its underlying mechanisms. In particular, we compared the impacts of MSC cytotherapy in the two genders with the aim of examining potential gender differences. Using the gonadectomy (GNX) model, we confirmed that the osteoporotic phenotypes were substantially consistent between female and male mice. Importantly, systemic MSC transplantation (MSCT) not only rescued trabecular bone loss in GNX mice but also restored cortical bone mass and bone quality. Unexpectedly, no differences were detected between the genders. Furthermore, MSCT demonstrated an equal efficiency in rectifying the bone remodeling balance in both genders of GNX animals, as proven by the comparable recovery of bone formation and parallel normalization of bone resorption. Mechanistically, using green fluorescent protein (GFP)-based cell-tracing, we demonstrated rapid engraftment but poor inhabitation of donor MSCs in the GNX recipient bone marrow of each gender. Alternatively, MSCT uniformly reduced the CD3⁺T-cell population and suppressed the serum levels of inflammatory cytokines in reversing female and male GNX osteoporosis, which was attributed to the ability of the MSC to induce T-cell apoptosis. Immunosuppression in the microenvironment eventually led to functional recovery of endogenous MSCs, which resulted in restored osteogenesis and normalized behavior to modulate osteoclastogenesis. Collectively, these data revealed recipient sexually monomorphic responses to MSC therapy in gonadal steroid deficiency-induced osteoporosis via immunosuppression/anti-inflammation and resident stem cell recovery.

NDRG2 suppression as a molecular hallmark of photoreceptor-specific cell death in the mouse retina

Photoreceptor cell death is recognized as the key pathogenesis of retinal degeneration, but the molecular basis underlying photoreceptor-specific cell loss in retinal damaging conditions is virtually unknown. The N-myc downstream regulated gene (NDRG) family has recently been reported to regulate cell viability, in particular NDRG1 has been uncovered expression in photoreceptor cells. Accordingly, we herein examined the potential roles of NDRGs in mediating photoreceptor-specific cell loss in retinal damages. By using mouse models of retinal degeneration and the 661 W photoreceptor cell line, we showed that photoreceptor cells are indeed highly sensitive to light exposure and the related oxidative stress, and that photoreceptor cells are even selectively diminished by phototoxins of the alkylating agent N-Methyl-N-nitrosourea (MNU). Unexpectedly, we discovered that of all the NDRG family members, NDRG2, but not the originally hypothesized NDRG1 or other NDRG subtypes, was selectively expressed and specifically responded to retinal damaging conditions in photoreceptor cells. Furthermore, functional experiments proved that NDRG2 was essential for photoreceptor cell viability, which could be attributed to NDRG2 control of the photo-oxidative stress, and that it was the suppression of NDRG2 which led to photoreceptor cell loss in damaging conditions. More importantly, NDRG2 preservation contributed to photoreceptor-specific cell maintenance and retinal protection both in vitro and in vivo. Our findings revealed a previously unrecognized role of NDRG2 in mediating photoreceptor cell homeostasis and established for the first time the molecular hallmark of photoreceptor-specific cell death as NDRG2 suppression, shedding light on improved understanding and therapy of retinal degeneration.

Resveratrol enhances the functionality and improves the regeneration of mesenchymal stem cell aggregates

Mesenchymal stem cell (MSC)-based regeneration, specifically cell aggregate or cell sheet engineering, is a promising approach for tissue reconstruction. Considering the advantages of ease of harvest and lack of immune rejection, the application of autologous MSCs (i.e., patients' own MSCs) in regenerative medicine has developed considerable interest. However, the impaired cell viability and regenerative potential following MSCs impacted by disease remain a major challenge. Resveratrol (RSV) exhibits reliable and extensive rejuvenative activities that have received increasing clinical attention. Here, we uncovered that resveratrol enhances the functionality and improves the regeneration of mesenchymal stem cell aggregates. Periodontal ligament MSCs (PDLSCs) from normal control subjects (N-PDLSCs) and periodontitis patients (P-PDLSCs) were investigated. Compared to N-PDLSCs, P-PDLSCs were less capable of forming cell aggregates, and P-PDLSC aggregates showed impaired osteogenesis and regeneration. These functional declines could be mimicked in N-PDLSCs by tumor necrosis factor alpha (TNF-α) treatment. Notably, a TNF-α-induced functional decline in N-PDLSC aggregates was rescued by RSV application. More importantly, in both N-PDLSCs and P-PDLSCs, RSV promoted cell aggregate formation and improved their osteogenic potential. Furthermore, as proven ectopically in vivo, the tissue regenerative capability of P-PDLSC aggregates was also enhanced after RSV treatment during aggregate formation in vitro. Finally, in a rat in situ regeneration model, we successfully applied both N-PDLSC aggregates and P-PDLSC aggregates to repair periodontal defects upon long-term functional improvements by RSV preconditioning. Together, our data unravel a novel methodology for using pharmacology (i.e., RSV)-based cell aggregate engineering to improve the functionality and facilitate the regeneration of MSCs from both healthy and inflammatory microenvironments, shedding light on improving the application of autologous MSC-mediated regenerative medicine.

Adipose mesenchymal stem cells from osteoporotic donors preserve functionality and modulate systemic inflammatory microenvironment in osteoporotic cytotherapy

Maintenance of bone homeostasis against diseased microenvironments remains as a major challenge. Recently, mesenchymal stem cells (MSCs) have been unravelled as potent microenvironmental modulators, the systemic infusion of which in cytotherapy can prevent or rescue extensive bone loss via anti-inflammation. However, MSCs also accept microenvironmental regulations; particularly, MSCs from bone marrow (BMMSCs) are prone to pathological microenvironmental factors of bone. In this study, we discovered that BMMSCs from osteoporotic donors of ovariectomized (OVX) mice lost their anti-inflammatory capability and failed to prevent bone loss when infused back into OVX recipients. Nevertheless, MSCs from adipose tissues (ADMSCs) preserved their anti-inflammatory capacity, despite diseased microenvironments of OVX donors, and continued to show protective effects on bone in OVX recipients. In the cellular level, the anti-inflammatory superiority of osteoporotic donor-derived ADMSCs over BMMSCs existed in their distinctive capability to induce T-cell apoptosis, which was molecularly attributed to retained expression levels of critical immunomodulatory genes. Furthermore, these functional discrepancies of BMMSCs and ADMSCs were due to differential stemness, energy metabolism and anti-oxidative defence system, underlying general disparity in their cellular states. Collectively, our findings optimize osteoporotic cytotherapy by using ADMSCs in resistance to and in modulation of diseased microenvironments.

Resveratrol counteracts bone loss via mitofilin-mediated osteogenic improvement of mesenchymal stem cells in senescence-accelerated mice

Rational: Senescence of mesenchymal stem cells (MSCs) and the related functional decline of osteogenesis have emerged as the critical pathogenesis of osteoporosis in aging. Resveratrol (RESV), a small molecular compound that safely mimics the effects of dietary restriction, has been well documented to extend lifespan in lower organisms and improve health in aging rodents. However, whether RESV promotes function of senescent stem cells in alleviating age-related phenotypes remains largely unknown. Here, we intend to investigate whether RESV counteracts senescence-associated bone loss via osteogenic improvement of MSCs and the underlying mechanism.

Methods: MSCs derived from bone marrow (BMMSCs) and the bone-specific, senescence-accelerated, osteoblastogenesis/osteogenesis-defective mice (the SAMP6 strain) were used as experimental models. In vivo application of RESV was performed at 100 mg/kg intraperitoneally once every other day for 2 months, and in vitro application of RESV was performed at 10 μM. Bone mass, bone formation rates and osteogenic differentiation of BMMSCs were primarily evaluated. Metabolic statuses of BMMSCs and the mitochondrial activity, transcription and morphology were also examined. Mitofilin expression was assessed at both mRNA and protein levels, and short hairpin RNA (shRNA)-based gene knockdown was applied for mechanistic experiments.

Results: Chronic intermittent application of RESV enhances bone formation and counteracts accelerated bone loss, with RESV improving osteogenic differentiation of senescent BMMSCs. Furthermore, in rescuing osteogenic decline under BMMSC senescence, RESV restores cellular metabolism through mitochondrial functional recovery via facilitating mitochondrial autonomous gene transcription. Molecularly, in alleviating senescence-associated mitochondrial disorders of BMMSCs, particularly the mitochondrial morphological alterations, RESV upregulates Mitofilin, also known as inner membrane protein of mitochondria (Immt) or Mic60, which is the core component of the mitochondrial contact site and cristae organizing system (MICOS). Moreover, Mitofilin is revealed to be indispensable for mitochondrial homeostasis and osteogenesis of BMMSCs, and that insufficiency of Mitofilin leads to BMMSC senescence and bone loss. More importantly, Mitofilin mediates resveratrol-induced mitochondrial and osteogenic improvements of BMMSCs in senescence.

Conclusion: Our findings uncover osteogenic functional improvements of senescent MSCs as critical impacts in anti-osteoporotic practice of RESV, and unravel Mitofilin as a novel mechanism mediating RESV promotion on mitochondrial function in stem cell senescence.

Lipopolysaccharide impairs permeability of pulmonary microvascular endothelial cells via Connexin40

The endotoxin lipopolysaccharide (LPS)-induced pulmonary endothelial barrier disruption is a key pathogenesis of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). However, the molecular mechanisms underlying LPS-impaired permeability of pulmonary microvascular endothelial cells (PMVECs) are not fully understood. Gap junctions, particularly Connexin40 (Cx40), are necessary for the maintenance of normal vascular function. In this study, we for the first time investigated the role of Cx40 in LPS-impaired permeability of PMVECs and provided potential therapeutic approaches based on mechanistic findings of Cx40 regulation by LPS stimuli. Rat PMVECs were isolated, cultured and identified with cell morphology, specific markers, ultrastructural characteristics and functional tests. Western blot analysis demonstrated that Cx40 is the major connexin highly expressed in PMVECs. Furthermore, by inhibiting Cx40 in a time-dependent manner, LPS impaired gap junction function and induced permeability injury of PMVECs. The key role of Cx40 decline in mediating detrimental effects of LPS was further confirmed in rescue experiments through Cx40 overexpression. Mechanistically, LPS stress on PMVECs inhibited the protein kinase C (PKC) pathway, which may synergize with the inflammatory nuclear factor kappaB (NFκB) signaling activation in suppressing Cx40 expression level and phosphorylation. Moreover, through pharmacological PKC activation or NFκB inhibition, Cx40 activity in PMVECs could be restored, leading to maintained barrier function under LPS stress. Our findings uncover a previously unrecognized role of Cx40 and its regulatory mechanisms in impaired endothelial integrity under endotoxin and inflammation, shedding light on intervention approaches to improve pulmonary endothelial barrier function in ALI and ARDS.

Reconstruction of Regenerative Stem Cell Niche by Cell Aggregate Engineering

The niche plays critical roles in regulating functionality and determining regenerative outcomes of stem cells, for which establishment of favorable microenvironments is in demand in translational medicine. In recent years, the cell aggregate technology has shown immense potential to reconstruct a beneficial topical niche for stem cell-mediated regeneration, which has been recognized as a promising concept for high-density stem cell delivery with preservation of the self-produced, tissue-specific extracellular matrix microenvironments. Here, we describe the basic methodology of stem cell aggregate-based niche engineering and quality check indexes prior to application.

Stem cell-based bone regeneration in diseased microenvironments: Challenges and solutions

Restoration of extensive bone loss and defects remain as an unfulfilled challenge in modern medicine. Given the critical contributions to bone homeostasis and diseases, mesenchymal stem cells (MSCs) have shown great promise to jumpstart and facilitate bone healing, with immense regenerative potential in both pharmacology-based endogenous MSC rescue/mobilization in skeletal diseases and emerging application of MSC transplantation in bone tissue engineering and cytotherapy. However, efficacy of MSC-based bone regeneration was not always achieved; particularly, fulfillment of MSC-mediated bone healing in diseased microenvironments of host comorbidities remains as a major challenge. Indeed, impacts of diseased microenvironments on MSC function rely not only on the dynamic regulation of resident MSCs by surrounding niche to convoy pathological signals of bone, but also on the profound interplay between transplanted MSCs and recipient components that mediates and modulates therapeutic effects on skeletal conditions. Accordingly, novel solutions have recently been developed, including improving resistance of MSCs to diseased microenvironments, recreating beneficial microenvironments to guarantee MSC-based regeneration, and usage of subcellular vesicles of MSCs in cell-free therapies. In this review, we summarize state-of-the-art knowledge regarding applications and challenges of MSC-mediated bone healing, further offering principles and effective strategies to optimize MSC-based bone regeneration in aging and diseases.

Anti-aging pharmacology in cutaneous wound healing: effects of metformin, resveratrol, and rapamycin by local application

Cutaneous wounds are among the most common soft tissue injuries and are particularly hard to heal in aging. Caloric restriction (CR) is well documented to extend longevity; pharmacologically, profound rejuvenative effects of CR mimetics have been uncovered, especially metformin (MET), resveratrol (RSV), and rapamycin (RAPA). However, locally applied impacts and functional differences of these agents on wound healing remain to be established. Here, we discovered that chronic topical administration of MET and RSV, but not RAPA, accelerated wound healing with improved epidermis, hair follicles, and collagen deposition in young rodents, and MET exerted more profound effects. Furthermore, locally applied MET and RSV improved vascularization of the wound beds, which were attributed to stimulation of adenosine monophosphate-activated protein kinase (AMPK) pathway, the key mediator of wound healing. Notably, in aged skin, AMPK pathway was inhibited, correlated with impaired vasculature and reduced healing ability. As therapeutic approaches, local treatments of MET and RSV prevented age-related AMPK suppression and angiogenic inhibition in wound beds. Moreover, in aged rats, rejuvenative effects of topically applied MET and RSV on cell viability of wound beds were confirmed, of which MET showed more prominent anti-aging effects. We further verified that only MET promoted wound healing and cutaneous integrity in aged skin. These findings clarified differential effects of CR-based anti-aging pharmacology in wound healing, identified critical angiogenic and rejuvenative mechanisms through AMPK pathway in both young and aged skin, and unraveled chronic local application of MET as the optimal and promising regenerative agent in treating cutaneous wound defects.