Effects of extracellular matrix viscoelasticity on cellular behaviour.

Substantial research over the past two decades has established that extracellular matrix (ECM) elasticity, or stiffness, affects fundamental cellular processes, including spreading, growth, proliferation, migration, differentiation and organoid formation. Linearly elastic polyacrylamide hydrogels and polydimethylsiloxane (PDMS) elastomers coated with ECM proteins are widely used to assess the role of stiffness, and results from such experiments are often assumed to reproduce the effect of the mechanical environment experienced by cells in vivo. However, tissues and ECMs are not linearly elastic materials-they exhibit far more complex mechanical behaviours, including viscoelasticity (a time-dependent response to loading or deformation), as well as mechanical plasticity and nonlinear elasticity. Here we review the complex mechanical behaviours of tissues and ECMs, discuss the effect of ECM viscoelasticity on cells, and describe the potential use of viscoelastic biomaterials in regenerative medicine. Recent work has revealed that matrix viscoelasticity regulates these same fundamental cell processes, and can promote behaviours that are not observed with elastic hydrogels in both two- and three-dimensional culture microenvironments. These findings have provided insights into cell-matrix interactions and how these interactions differentially modulate mechano-sensitive molecular pathways in cells. Moreover, these results suggest design guidelines for the next generation of biomaterials, with the goal of matching tissue and ECM mechanics for in vitro tissue models and applications in regenerative medicine.

Machine learning aided single cell image analysis improves understanding of morphometric heterogeneity of human mesenchymal stem cells.

The multipotent stem cells of our body have been largely harnessed in biotherapeutics. However, as they are derived from multiple anatomical sources, from different tissues, human mesenchymal stem cells (hMSCs) are a heterogeneous population showing ambiguity in their in vitro behavior. Intra-clonal population heterogeneity has also been identified and pre-clinical mechanistic studies suggest that these cumulatively depreciate the therapeutic effects of hMSC transplantation. Although various biomarkers identify these specific stem cell populations, recent artificial intelligence-based methods have capitalized on the cellular morphologies of hMSCs, opening a new approach to understand their attributes. A robust and rapid platform is required to accommodate and eliminate the heterogeneity observed in the cell population, to standardize the quality of hMSC therapeutics globally. Here, we report our primary findings of morphological heterogeneity observed within and across two sources of hMSCs namely, stem cells from human exfoliated deciduous teeth (SHEDs) and human Wharton jelly mesenchymal stem cells (hWJ MSCs), using real-time single-cell images generated on immunophenotyping by imaging flow cytometry (IFC). We used the ImageJ software for identification and comparison between the two types of hMSCs using statistically significant morphometric descriptors that are biologically relevant. To expand on these insights, we have further applied deep learning methods and successfully report the development of a Convolutional Neural Network-based image classifier. In our research, we introduced a machine learning methodology to streamline the entire procedure, utilizing convolutional neural networks and transfer learning for binary classification, achieving an accuracy rate of 97.54%. We have also critically discussed the challenges, comparisons between solutions and future directions of machine learning in hMSC classification in biotherapeutics.

Human cytomegalovirus infection impairs neural differentiation via repressing sterol regulatory element binding protein 2-mediated cholesterol biosynthesis.

Congenital human cytomegalovirus (HCMV) infection is a major cause of abnormalities and disorders in the central nervous system (CNS) and/or the peripheral nervous system (PNS). However, the complete pathogenesis of neural differentiation disorders caused by HCMV infection remains to be fully elucidated. Stem cells from human exfoliated deciduous teeth (SHEDs) are mesenchymal stem cells (MSCs) with a high proliferation and neurogenic differentiation capacity. Since SHEDs originate from the neural crest of the early embryonic ectoderm, SHEDs were hypothesized to serve as a promising cell line for investigating the pathogenesis of neural differentiation disorders in the PNS caused by congenital HCMV infection. In this work, SHEDs were demonstrated to be fully permissive to HCMV infection and the virus was able to complete its life cycle in SHEDs. Under neurogenic inductive conditions, HCMV infection of SHEDs caused an abnormal neural morphology. The expression of stem/neural cell markers was also disturbed by HCMV infection. The impairment of neural differentiation was mainly due to a reduction of intracellular cholesterol levels caused by HCMV infection. Sterol regulatory element binding protein-2 (SREBP2) is a critical transcription regulator that guides cholesterol synthesis. HCMV infection was shown to hinder the migration of SREBP2 into nucleus and resulted in perinuclear aggregations of SREBP2 during neural differentiation. Our findings provide new insights into the prevention and treatment of nervous system diseases caused by congenital HCMV infection.

Synergistic Influence of Fibrous Pattern Orientation and Modulus on Cellular Mechanoresponse.

The fibrous extracellular matrix (ECM) is vital for tissue regeneration and impacts implanted device treatments. Previous research on fibrous biomaterials shows varying cellular reactions to surface orientation, often due to unclear interactions between surface topography and substrate elasticity. Our study addresses this gap by achieving the rapid creation of hydrogels with diverse fibrous topographies and varying substrate moduli through a surface printing strategy. Cells exhibit heightened traction force on nanopatterned soft hydrogels, particularly with randomly distributed patterns compared with regular soft hydrogels. Meanwhile, on stiff hydrogels featuring an aligned topography, optimal cellular mechanosensing is observed compared to random topography. Mechanistic investigations highlight that cellular force-sensing and adhesion are influenced by the interplay of pattern deformability and focal adhesion orientation, subsequently mediating stem cell differentiation. Our findings highlight the importance of combining substrate modulus and topography to guide cellular behavior in designing advanced tissue engineering biomaterials.

Comparative evaluation of bone marrow and dental pulp mesenchymal stem cells for motor functional recovery in rat sciatic nerve injury.

This study delves into the impact of mesenchymal stem cells derived from bone marrow (BM-MSCs) and those sourced from dental pulp (DP-MSCs) on the recovery of motor function and morphological aspects of the rat's sciatic nerve after crush injuries. The findings highlight that the groups treated with BM-MSCs, DP-MSCs or a combination of both (BM + DP-MSCs) displayed enhanced sciatic functional index values when juxtaposed with the sham group. This points to bettered motor functionalities. A deeper morphological analysis showed that all the groups had retained perineurium structure and fascicular arrangement. Notably, the sham and BM-MSCs groups had very few inconsistencies. All groups showed standard vascular density. Remarkably, the combined treatment group (BM + DP-MSCs) presented diminished oedema and a lower count of inflammatory cells. Through immunohistochemical methods, the presence of S100 expression was noted in the groups that underwent treatment. In summation, the study suggests that both BM-MSCs and DP-MSCs, whether used singly or in combination, can significantly aid in motor function restoration and morphological enhancements. An interesting observation from our research and earlier studies is that stem cells from dental pulp, which are sourced with less discomfort from milk and wisdom teeth, show a heightened propensity to evolve into nerve cells. This is in contrast to the more uncomfortably acquired BM-MSCs.

Conditioned medium of human mesenchymal stem cells affects stem cell senescence in osteoporosis.

Systemic transplantation of mesenchymal stem cells (MSCs) and conditioned medium derived from MSCs have been reported to recover bone loss in animal models of osteoporosis; however, the underlying mechanisms remain unclear. We recently reported that extracellular vesicles released from human mesenchymal stem cells (hMSCs) prevent senescence of stem cells in bisphosphonate-related osteonecrosis of the jaw model. In this study, we aimed to compare the effects of conditioned medium (hMSCs-CM) from early and late passage hMSCs on cellular senescence and to verify the benefits of CM from early passage hMSCs in mitigating the progression of osteoporosis through the prevention of cellular senescence. We investigated the distinct endocrine effects of early (P5) and late (P17) passage hMSCs in vitro, as well as the preventive benefits of early passage hMSCs-CM in osteoporosis model triggered by ovariectomy. Our results indicate that long-term cultured hMSCs contributed to the progression of inflammatory transcriptional programs in P5 hMSCs, ultimately impairing their functionality and enhancing senescence-related characteristics. Conversely, early passage hMSCs reversed these alterations. Moreover, early passage hMSCs-CM infused intravenously in a postmenopausal osteoporosis mouse model suppressed bone degeneration and prevented osteoporosis by reducing ovariectomy-induced senescence in bone marrow MSCs and reducing the expression of senescence-associated secretory phenotype-related cytokines. Our findings highlight the high translational value of early passage hMSCs-CM in antiaging intervention and osteoporosis prevention.

Extracellular vesicles deviced from hypoxia-3D-GMSCs rescue the mitochondrial dysfunction of aging-GMSCs.

Mesenchymal stem cells (MSCs) are ubiquitous multipotent cells exhibiting significant therapeutic potential for various diseases. It is generally accepted that clinical application requires massive expansion of MSCs, which is often accompanied by the occurrence of replicative senescence. Additionally, senescent MSCs exhibit significantly reduced proliferation, differentiation, and therapeutic potential. The scale-up of MSCs production and cellular senescence are major challenges for translational applications. This study first collected extracellular vesicles (EVs) from gingival MSCs (GMSCs) under hypoxia preconditioning combined with 3D dynamic culture (obtained EVs designed as H-3D-EVs). Subsequently, we further explored the effects and mechanisms of H-3D-EVs on aging-GMSCs. The results showed that H-3D-EVs improved the proliferation ability and cell activity of aging-GMSCs, and ameliorated their senescence. mRNA sequencing reveals transcriptomic changes in aging-GMSCs. It was found that H-3D-EVs up-regulated genes related to mitochondrial dynamics, cell cycle, and DNA repair, while down-regulated aging-related genes. Furthermore, we verified that H-3D-EVs corrected the mitochondrial dysfunction of aging-GMSCs by improving mitochondrial dynamics. In summary, this study provides a promising strategy for improving the culture methods of GMSCs and avoiding its senescence in large-scale production.

Activating the healing process: three-dimensional culture of stem cells in Matrigel for tissue repair.

BACKGROUND: To establish a strategy for stem cell-related tissue regeneration therapy, human gingival mesenchymal stem cells (hGMSCs) were loaded with three-dimensional (3D) bioengineered Matrigel matrix scaffolds in high-cell density microtissues to promote local tissue restoration. METHODS: The biological performance and stemness of hGMSCs under 3D culture conditions were investigated by viability and multidirectional differentiation analyses. A Sprague‒Dawley (SD) rat full-thickness buccal mucosa wound model was established, and hGMSCs/Matrigel were injected into the submucosa of the wound. Autologous stem cell proliferation and wound repair in local tissue were assessed by histomorphometry and immunohistochemical staining. RESULTS: Three-dimensional suspension culture can provide a more natural environment for extensions and contacts between hGMSCs, and the viability and adipogenic differentiation capacity of hGMSCs were significantly enhanced. An animal study showed that hGMSCs/Matrigel significantly accelerated soft tissue repair by promoting autologous stem cell proliferation and enhancing the generation of collagen fibers in local tissue. CONCLUSION: Three-dimensional cell culture with hydrogel scaffolds, such as Matrigel, can effectively improve the biological function and maintain the stemness of stem cells. The therapeutic efficacy of hGMSCs/Matrigel was confirmed, as these cells could effectively stimulate soft tissue repair to promote the healing process by activating the host microenvironment and autologous stem cells.

A Zinc Oxide Nanowire-Modified Mineralized Collagen Scaffold Promotes Infectious Bone Regeneration.

Bone infection poses a major clinical challenge that can hinder patient recovery and exacerbate postoperative complications. This study has developed a bioactive composite scaffold through the co-assembly and intrafibrillar mineralization of collagen fibrils and zinc oxide (ZnO) nanowires (IMC/ZnO). The IMC/ZnO exhibits bone-like hierarchical structures and enhances capabilities for osteogenesis, antibacterial activity, and bacteria-infected bone healing. During co-cultivation with human bone marrow mesenchymal stem cells (BMMSCs), the IMC/ZnO improves BMMSC adhesion, proliferation, and osteogenic differentiation even under inflammatory conditions. Moreover, it suppresses the activity of Gram-negative Porphyromonas gingivalis and Gram-positive Streptococcus mutans by releasing zinc ions within the acidic infectious microenvironment. In vivo, the IMC/ZnO enables near-complete healing of infected bone defects within the intricate oral bacterial milieu, which is attributed to IMC/ZnO orchestrating M2 macrophage polarization, and fostering an osteogenic and anti-inflammatory microenvironment. Overall, these findings demonstrate the promise of the bioactive scaffold IMC/ZnO for treating bacteria-infected bone defects.

Multifunctional Biodegradable Conductive Hydrogel Regulating Microenvironment for Stem Cell Therapy Enhances the Nerve Tissue Repair.

The nerve guidance conduits incorporated with stem cells, which can differentiate into the Schwann cells (SCs) to facilitate myelination, shows great promise for repairing the severe peripheral nerve injury. The innovation of advanced hydrogel materials encapsulating stem cells, is highly demanded for generating supportive scaffolds and adaptive microenvironment for nerve regeneration. Herein, this work demonstrates a novel strategy in regulating regenerative microenvironment for peripheral nerve repair with a biodegradable conductive hydrogel scaffold, which can offer multifunctional capabilities in immune regulation, enhancing angiogenesis, driving SCs differentiation, and promoting axon regrowth. The biodegradable conductive hydrogel is constructed by incorporation of polydopamine-modified silicon phosphorus (SiP@PDA) nanosheets into a mixture of methacryloyl gelatin and decellularized extracellular matrix (GelMA/ECM). The biomimetic electrical microenvironment performs an efficacious strategy to facilitate macrophage polarization toward a pro-healing phenotype (M2), meanwhile the conductive hydrogel supports vascularization in regenerated tissue through sustained Si element release. Furthermore, the MSCs 3D-cultured in GelMA/ECM-SiP@PDA conductive hydrogel exhibits significantly increased expression of genes associated with SC-like cell differentiation, thus facilitating the myelination and axonal regeneration. Collectively, both the in vitro and in vivo studies demonstrates that the rationally designed biodegradable multifunctional hydrogel significantly enhances nerve tissues repair.

Efficacy and safety of autologous or allogeneic mesenchymal stromal cells from adult adipose tissue expanded and combined with tricalcium phosphate biomaterial for the surgical treatment of atrophic nonunion of long bones: a phase II clinical trial.

BACKGROUND: Autologous bone grafting is the standard treatment for the surgical management of atrophic nonunion of long bones. Other solutions, such as bone marrow mesenchymal stem cells (BM-MSC) combined with phospho-calcium material, have also been used. Here we evaluate the safety and early efficacy of a novel procedure using autologous or allogenic adipose tissue mesenchymal stromal cells (AT-MSC) seeded in a patented tricalcium phosphate-based biomaterial for the treatment of bone regeneration in cases of atrophic nonunion. METHODS: This was a prospective, multicentric, open-label, phase 2 clinical trial of patients with atrophic nonunion of long bones. Biografts of autologous or allogenic AT-MSC combined with a phosphate substrate were manufactured prior to the surgical procedures. The primary efficacy was measured 6 months after surgery, but patients were followed for 12 months after surgery and a further year out of the scope of the study. All adverse events were recorded. This cohort was compared with a historical cohort of 14 cases treated by the same research team with autologous BM-MSC. RESULTS: A total of 12 patients with atrophic nonunion of long bones were included. The mean (SD) age was 41.2 (12.1) years and 66.7% were men. Bone healing was achieved in 10 of the 12 cases (83%) treated with the AT-MSC biografts, a percentage of healing similar (11 of the 14 cases, 79%) to that achieved in patients treated with autologous BM-MSC. Overall, two adverse events, in the same patient, were considered related to the procedure. CONCLUSIONS: The results of this study suggest that AT-MSC biografts are safe for the treatment of bone regeneration in cases of atrophic nonunion and reach high healing rates. TRIAL REGISTRATION: Study registered with EUDRA-CT (2013-000930-37) and ClinicalTrials.gov (NCT02483364).

Comparative analysis of uninduced and neuronally-induced human dental pulp stromal cells in a 6-OHDA model of Parkinson's disease.

BACKGROUND: In recent years, dental pulp stromal cells (DPSCs) have emerged as a promising therapeutic approach for Parkinson's disease (PD), owing to their inherent neurogenic potential and the lack of neuroprotective treatments for this condition. However, uncertainties persist regarding the efficacy of these cells in an undifferentiated state versus a neuronally-induced state. This study aims to delineate the distinct therapeutic potential of uninduced and neuronally-induced DPSCs in a rodent model of PD induced by 6-Hydroxydopamine (6-OHDA). METHODS: DPSCs were isolated from human teeth, characterized as mesenchymal stromal cells, and induced to neuronal differentiation. Neuronal markers were assessed before and after induction. DPSCs were transplanted into the substantia nigra pars compacta (SNpc) of rats 7 days following the 6-OHDA lesion. In vivo tracking of the cells, evaluation of locomotor behavior, dopaminergic neuron survival, and the expression of essential proteins within the dopaminergic system were conducted 7 days postgrafting. RESULTS: Isolated DPSCs exhibited typical characteristics of mesenchymal stromal cells and maintained a normal karyotype. DPSCs consistently expressed neuronal markers, exhibiting elevated expression of ßIII-tubulin following neuronal induction. Results from the animal model showed that both DPSC types promoted substantial recovery in dopaminergic neurons, correlating with enhanced locomotion. Additionally, neuronally-induced DPSCs prevented GFAP elevation, while altering DARPP-32 phosphorylation states. Conversely, uninduced DPSCs reduced JUN levels. Both DPSC types mitigated the elevation of glycosylated DAT. CONCLUSIONS: Our results suggested that uninduced DPSCs and neuronally-induced DPSCs exhibit potential in reducing dopaminergic neuron loss and improving locomotor behavior, but their underlying mechanisms differ.

Functionalization of Alginate Hydrogels with a Multifunctional Peptide Supports Mesenchymal Stem Cell Adhesion and Reduces Bacterial Colonization.

Hydrogels with cell adhesive moieties stand out as promising materials to enhance tissue healing and regeneration. Nonetheless, bacterial infections of the implants represent an unmet major concern. In the present work, we developed an alginate hydrogel modified with a multifunctional peptide containing the RGD cell adhesive motif in combination with an antibacterial peptide derived from the 1-11 region of lactoferrin (LF). The RGD-LF branched peptide was successfully anchored to the alginate backbone by carbodiimide chemistry, as demonstrated by 1H NMR and fluorescence measurements. The functionalized hydrogel presented desirable physicochemical properties (porosity, swelling and rheological behavior) to develop biomaterials for tissue engineering. The viability of mesenchymal stem cells (MSCs) on the peptide-functionalized hydrogels was excellent, with values higher than 85 % at day 1, and higher than 95 % after 14 days in culture. Moreover, the biological characterization demonstrated the ability of the hydrogels to significantly enhance ALP activity of MSCs as well as to decrease bacterial colonization of both Gram-positive and Gram-negative models. Such results prove the potential of the functionalized hydrogels as novel biomaterials for tissue engineering, simultaneously displaying cell adhesive activity and the capacity to prevent bacterial contamination, a dual bioactivity commonly not found for these types of hydrogels.

Concave/Convex Curvature of Anisotropic Grooves Differentially Alters Cellular Morphology, Adhesion, and Proliferation.

Curvature is an integral part of the complex in vivo tissue architecture across various length scales. Therefore, several in vitro models with a patterned curvature in different length scales have been developed to understand the role of this in cellular behavior. At the subcellular scale, wavy patterns have been reported wherein concave and convex grooves are adjacently present. However, the independent effect of continuous subcellular concave and convex shapes has not been reported, mainly owing to the limitations in fabricating such patterns. In this study, we developed continuous concave and convex grooves on polydimethylsiloxane (PDMS) using a Dracaena sanderiana (bamboo) leaf as a template. The first (negative) replica from the abaxial side of the bamboo leaf, which imparted concave grooves on PDMS, was subsequently used as a template to fabricate a positive replica of the leaf, resulting in convex grooves of the same size and arrangement as the concave grooves. We examined the influence of the groove curvature on the morphology of bone marrow-derived human mesenchymal stem cells (BM-hMSCs) and skeletal muscle cells (C2C12). BM-hMSCs and C2C12 cells aligned on both concave and convex grooves as compared to the random orientation on a flat substrate. The significant difference was observed in the morphology of both cells, in terms of area, aspect ratio, number, and length of protrusions on concave and convex patterns. We found that the number of protrusions was also dependent on the ratio of cell to pattern length scale for convex-shaped grooves but independent of length scale for concave-shaped grooves. The proliferation of BM-hMSCs was also found to be different on concave and convex shapes. Therefore, this study shows the importance of (1) convex and concave curvatures of the subcellular length scale in cellular response, (2) dependence on the ratio of cell and curvature length scale, and (3) use of natural templates for overcoming fabrication challenges.

Effect of Peptide-Polymer Host-Guest Electrostatic Interactions on Self-Assembling Peptide Hydrogels Structural and Mechanical Properties and Polymer Diffusivity.

Peptide-based supramolecular hydrogels are an attractive class of soft materials for biomedical applications when biocompatibility is a key requirement as they exploit the physical self-assembly of short self-assembling peptides avoiding the need for chemical cross-linking. Based on the knowledge developed through our previous work, we designed two novel peptides, E(FKFE)2 and K(FEFK)2, that form transparent hydrogels at pH 7. We characterized the phase behavior of these peptides and showed the clear link that exists between the charge carried by the peptides and the physical state of the samples. We subsequently demonstrate the cytocompatibility of the hydrogel and its suitability for 3D cell culture using 3T3 fibroblasts and human mesenchymal stem cells. We then loaded the hydrogels with two polymers, poly-l-lysine and dextran. When polymer and peptide fibers carry opposite charges, the size of the elemental fibril formed decreases, while the overall level of fiber aggregation and fiber bundle formation increases. This overall network topology change, and increase in cross-link stability and density, leads to an overall increase in the hydrogel mechanical properties and stability, i.e., resistance to swelling when placed in excess media. Finally, we investigate the diffusion of the polymers out of the hydrogels and show how electrostatic interactions can be used to control the release of large molecules. The work clearly shows how polymers can be used to tailor the properties of peptide hydrogels through guided intermolecular interactions and demonstrates the potential of these new soft hydrogels for use in the biomedical field in particular for delivery or large molecular payloads and cells as well as scaffolds for 3D cell culture.

A Biomimetic Fibrous Composite Scaffold with Nanotopography-Regulated Mineralization for Bone Defect Repair.

The effective regeneration of large bone defects via bone tissue engineering is challenging due to the difficulty in creating an osteogenic microenvironment. Inspired by the fibrillar architecture of the natural extracellular matrix, we developed a nanoscale bioengineering strategy to produce bone fibril-like composite scaffolds with enhanced osteogenic capability. To activate the surface for biofunctionalization, self-adaptive ridge-like nanolamellae were constructed on poly(ε-caprolactone) (PCL) electrospinning scaffolds via surface-directed epitaxial crystallization. This unique nanotopography with a markedly increased specific surface area offered abundant nucleation sites for Ca2+ recruitment, leading to a 5-fold greater deposition weight of hydroxyapatite than that of the pristine PCL scaffold under stimulated physiological conditions. Bone marrow mesenchymal stem cells (BMSCs) cultured on bone fibril-like scaffolds exhibited enhanced adhesion, proliferation, and osteogenic differentiation in vitro. In a rat calvarial defect model, the bone fibril-like scaffold significantly accelerated bone regeneration, as evidenced by micro-CT, histological histological and immunofluorescence staining. This work provides the way for recapitulating the osteogenic microenvironment in tissue-engineered scaffolds for bone repair.

Effect of bone-marrow-derived mesenchymal stem cells on the rate of orthodontic tooth movements in rabbits.

Mesenchymal stem cells from bone marrow, such as bone marrow aspirate concentrate (BMAC) and cultured and isolated bone marrow mesenchymal stem cells (BM-MSCs), have been used as therapeutic alternatives to enhance remodeling in the bone. OBJECTIVE: This study aimed to evaluate the effects of BMAC and BM-MSCs on orthodontic tooth movements in rabbits. METHODS: A100- gram nickel-titanium closed-coil springs were used to initiate orthodontic tooth movement of the lower first premolars in 35 male New Zealand rabbits for 21 days. Using a split-mouth design, autologous BMAC or BM-MSCs were submucosally injected into the right sides of the lower jaw, while the left sides served as the control. On days 7, 14, and 21, a three-dimensional digital model scan was used to measure the amount of tooth movement. The microfocus computed tomography (Micro-CT) and histological findings were examined on day 0 as the baseline measurement and on days 7, 14, and 21. RESULTS: Compared to the control group, the quadrant receiving BMAC and BM-MSCs had a considerably greater amount of tooth movement. Histomorphometric analysis revealed that both BMAC and BM-MSCs had significantly higher numbers of osteoclasts and active bone-resorptive lacunae. The resorptive changes were greater in the BMAC and BM-MSCs groups than in the control group. CONCLUSION: The submucosal injection of BMAC and BM-MSCs accelerates orthodontic tooth movement (OTM) by decreasing bone density and supplying more osteoclast progenitor cells.

Systematic review of the osteogenic effect of rare earth nanomaterials and the underlying mechanisms.

Rare earth nanomaterials (RE NMs), which are based on rare earth elements, have emerged as remarkable biomaterials for use in bone regeneration. The effects of RE NMs on osteogenesis, such as promoting the osteogenic differentiation of mesenchymal stem cells, have been investigated. However, the contributions of the properties of RE NMs to bone regeneration and their interactions with various cell types during osteogenesis have not been reviewed. Here, we review the crucial roles of the physicochemical and biological properties of RE NMs and focus on their osteogenic mechanisms. RE NMs directly promote the proliferation, adhesion, migration, and osteogenic differentiation of mesenchymal stem cells. They also increase collagen secretion and mineralization to accelerate osteogenesis. Furthermore, RE NMs inhibit osteoclast formation and regulate the immune environment by modulating macrophages and promote angiogenesis by inducing hypoxia in endothelial cells. These effects create a microenvironment that is conducive to bone formation. This review will help researchers overcome current limitations to take full advantage of the osteogenic benefits of RE NMs and will suggest a potential approach for further osteogenesis research.

Pluronic F127 hydrogel-loaded extracellular vesicles from adipose-derived mesenchymal stem cells promote tracheal cartilage regeneration via SCNN1B delivery.

Extracellular vesicles (EVs) derived from adipose-derived mesenchymal stem cells (AMSC-EVs) have been highlighted as a cell-free therapy due to their regenerative capability to enhance tissue and organ regeneration. Herein, we aimed to examine the mechanism of PF127-hydrogel@AMSC-EVs in promoting tracheal cartilage defect repair. Based on bioinformatics methods, SCNN1B was identified as a key gene for the osteogenic differentiation of AMSCs induced by AMSC-EVs. EVs were isolated from rat AMSCs and then loaded onto thermo-sensitive PF-127 hydrogel to develop PF127-hydrogel@AMSC-EVs. It was established that PF127-hydrogel@AMSC-EVs could effectively deliver SCNN1B into AMSCs, where SCNN1B promoted AMSC osteogenic differentiation. The promotive effect was evidenced by enhanced ALP activity, extracellular matrix mineralization, and expression of s-glycosaminoglycan, RUNX2, OCN, collagen II, PERK, and ATF4. Furthermore, the in vivo experiments revealed that PF127-hydrogel@AMSC-SCNN1B-EVs stimulated tracheal cartilage regeneration in rats through PERK/ATF4 signaling axis activation. Therefore, PF127-hydrogel@AMSC-SCNN1B-EVs may be a novel cell-free biomaterial to facilitate tracheal cartilage regeneration and cartilage injury repair.

Lhx6 regulates canonical Wnt signaling to control the fate of mesenchymal progenitor cells during mouse molar root patterning.

Mammalian tooth crown formation has long served as a model for investigating how patterning and morphogenesis are orchestrated during development. However, the mechanism underlying root patterning and morphogenesis remains poorly understood. In this study, we find that Lhx6 labels a subpopulation of root progenitor cells in the apical dental mesenchyme, which is closely associated with furcation development. Loss of Lhx6 leads to furcation and root number defects, indicating that Lhx6 is a key root patterning regulator. Among the multiple cellular events regulated by Lhx6 is the odontoblast fate commitment of progenitor cells, which it controls in a cell-autonomous manner. Specifically, Lhx6 loss leads to elevated expression of the Wnt antagonist Sfrp2 and down-regulation of Wnt signaling in the furcation region, while overactivation of Wnt signaling in Lhx6+ progenitor cells partially restore the furcation defects in Lhx6-/- mice. Collectively, our findings have important implications for understanding organ morphogenesis and future strategies for tooth root regeneration.