Biomechanical, biophysical and biochemical modulators of cytoskeletal remodelling and emergent stem cell lineage commitment

Chondroitin sulfate/hyaluronic acid/carboxymethylcellulose macroporous cryogels for controlled delivery of TGF-β1 and IGF-1 to induce chondrogenic differentiation of adipose-derived stem cells in cartilage tissue engineering

To repair articular cartilage defects using adipose-derived stem cells (ASCs), we aim to fabricate macroporous cryogel scaffolds from chondroitin sulfate (CS) and hyaluronic acid (HA), two of the most abundant glycosaminoglycans in cartilage extracellular matrix. Carboxymethylcellulose was blended with HA and CS and crosslinked with 1,4-butanediol diglycidyl ether to prepare a supramacroporous chondroitin sulfate/hyaluronic acid/carboxymethylcellulose (CHC) cryogel. The cryogel is biodegradable and has unique mechanical properties for use as a scaffold for cartilage tissue engineering. The transforming growth factor-β1 (TGF-β1) and insulin-like growth factor-1 (IGF-1) were bound to CS for prolonged presentation of these growth factors in the scaffolds, with controlled release extended to >21 days. The TGF-β1 and IGF-1 can act in combination to regulate chondrogenic differentiation of seeded ASCs. The CHC/TGF-β1/IGF-1 cryogel scaffold promotes the chondrogenesis over CHC/TGF-β1 from cell morphology, matrix and type II collagen production. From qRT-PCR analysis, it also upregulated the gene expression of SRY-box transcription factor 9 (SOX9), type II collagen (COL2A1), aggrecan (ACAN), and proteoglycan 4 (PRG4) while downregulated the gene expression of type X collagen (COL10A1) After in vitro culture ASCs in CHC/TGF-β1/IGF-1 cryogel for 14 days, the cell/scaffold constructs were implanted in rabbit knees to repair full-thickness articular cartilage defects. The regenerated neocartilage tissue on the surface of defect in the cellular group demonstrates similar morphological and histological features and comparable mechanical properties as the native cartilage. The CHC/TGF-β1/IGF-1 cryogel is an excellent scaffold for preparing tissue-engineered cartilage from ASCs in treating articular cartilage defects.

Sex differences in physical activity dose-response effects on site-specific bone mineral density during childhood and adolescence

Physical activity (PA) serves as a modifiable determinant of bone mineral density (BMD). However, sex- and site-specific dose-response relationships remain poorly defined. Leveraging data from the National Health and Nutrition Examination Survey (NHANES 2011-2014), this cross-sectional study investigated sex-specific associations between accelerometer-derived PA (volume and intensity) and site-specific BMD in 2,659 children and adolescents aged 8-19 years. BMD assessment was conducted via dual-energy X-ray absorptiometry, and PA was quantified using monitor-independent movement summary units (MIMS). Linear and nonlinear analyses revealed distinct patterns: boys exhibited stronger linear associations between PA volume and BMD at weight-bearing sites (e.g., pelvis, arms, and legs; β = 0.003-0.004, P < 0.05), and girls demonstrated nonlinear thresholds (e.g., volume threshold: 15.0 × 103 MIMS/day). Both sexes had intensity-driven thresholds (~ 45-49 MIMS/min), with diminishing returns above these values (β = 0.010 in boys; stagnation in girls). Directional trends suggest the greater BMD gains per standard deviation (SD) increase in PA for boys compared with that for girls across most skeletal regions (e.g., total body less head: 0.131 SD vs. 0.106 SD for intensity). However, statistical significance (P < 0.05) was observed only for arm BMD responses. Mechanistic analyses highlighted the corresponding biomechanical principles, with weight-bearing regions showing stronger PA-BMD links than nonweight-bearing sites (e.g., spine). These findings underscore the importance of prioritizing high-intensity, weight-bearing activities, particularly for girls, to optimize skeletal health during growth. Public health strategies should focus on achieving, rather than exceeding, the identified daily 60 min intensity thresholds (~ 45-49 MIMS/min) through school- and community-based interventions.

Substrate Stiffness Modulates TGF-β1-Induced Lineage Specification in Multipotent Vascular Stem Cells

Multipotent vascular stem cells (MVSCs) are found in the vascular wall and surrounding tissues and possess the ability to differentiate into mesenchymal lineages. Previous studies have shown that MVSCs can be activated in response to vascular injury and differentiate into vascular smooth muscle cells (SMCs), contributing to vascular remodeling and microvessel formation. However, it remains unclear as to whether and how microenvironmental changes in the extracellular matrix, such as substrate stiffness, modulates MVSC differentiation under pathological conditions. This study demonstrated that MVSCs cultured on stiff substrates exhibited increased cell spreading, stronger cell adhesion, and a higher expression of SMC markers, including myosin heavy chain (MHC), myocardin (MYCD), calponin 1 (CNN1), and smooth muscle α-actin (SMA). In contrast, MVSCs on soft substrates showed an elevated expression of the chondrogenic markers aggrecan 1 (AGC1) and collagen-II (COL2A1). The presence of TGF-β1 further increased the expression of SMC markers on stiff substrates and chondrogenic markers on the soft substrates. Collectively, these results establish substrate stiffness as a key regulator of MVSC lineage commitment through cytoskeletal reorganization, with TGF-β1 acting as a biochemical amplifier. Our findings highlight the substrate-stiffness-dependent differentiation of MVSCs and provide mechanistic insights into the role of MVSCs in vascular remodeling during atherosclerosis development and blood vessel regeneration.

Study of Cytotoxicity of 3-Azabicyclo[3.1.0]hexanes and Cyclopropa[a]pyrrolizidines Spiro-Fused to Acenaphthylene-1(2H)-one and Aceanthrylene-1(2H)-one Fragments Against Tumor Cell Lines

A series of 3-azabicyclo[3.1.0]hexanes and cyclopropa[a]pyrrolizidines spiro-fused to acenaphthylene-1(2H)-one and aceanthrylene-1(2H)-one frameworks have been studied for their in vitro antiproliferative activity against human erythroleukemia (K562), cervical carcinoma (HeLa), melanoma (Sk-mel-2), osteosarcoma (U2OS), as well as murine melanoma (B16) cell lines. Using confocal microscopy, it was found that cultivation with the tested spiro-fused compounds led to the disappearance of stress fibers (granular actin was distributed diffusely in the cytoplasm in up to 56% of treated cells) and decrease in filopodia-like deformations (up to 69% after cultivation), which indirectly suggests a decrease in cell motility. The human melanoma cell line scratch test showed that these cells lose their ability to move after cultivation with the tested spiro-fused compounds and do not fill the scratched strip. This was also supported by docking simulations with actin-related targets (PDB ID: 8DNH, 2Q1N). Using flow cytometry, the impact on the mitochondrial membrane potential showed that the tested compounds led to a significant increase in the number of cells with decreased mitochondrial membrane potential from 10% for the control up to 55-80% for the cyclopropa[a]pyrrolizidine adducts. The obtained results support the antitumor effect of the tested spiro-compounds and encourage the extension of the study in order to improve their anticancer activity as well as reduce their toxicological risks.

Supramolecular Additive Screening to Engineer Microfibrous Rafts for Expansion of Pluripotent Stem Cells in Dynamic Suspension

Human induced pluripotent stem cells (hiPSCs) hold the potential to generate any human tissue for transplantation in regenerative therapies. These complex cell therapies require billions of cells, which is challenging to acquire in planar adherent cultures. Transitioning hiPSCs to 3D suspension culture on microcarrier materials, often bead-shaped, improves the total surface area accessible to cells, thereby enabling culture scale-up. However, bead-shaped microcarriers do not have the optimal shape configuration, because it is the lowest surface-to-volume ratio of all geometrical shapes, and it also induces uncontrolled cell clumping. Application of synthetic, microfibrous rafts as a replacement for bead-shaped microcarriers potentially solves these issues. Here, microfibrous rafts are engineered by first screening a supramolecular biomaterial library composed of bisurea (BU)-peptide conjugate additives for its ability to induce hiPSC adhesion and maintenance of its pluripotent state, followed by electrospinning the screening-hit into raft-like structures. The resulting rafts contain cylinder-like microfibers, which have a higher surface-to-volume ratio compared to conventional bead-shaped microcarriers, and the flat configuration of the rafts prevents clumping.

The transcriptional landscape of the developing chick trigeminal ganglion

The trigeminal ganglion is a critical structure in the peripheral nervous system, responsible for transmitting sensations of touch, pain, and temperature from craniofacial regions to the brain. Trigeminal ganglion development depends upon intrinsic cellular programming as well as extrinsic signals exchanged by diverse cell populations. With its complex anatomy and dual cellular origin from cranial placodes and neural crest cells, the trigeminal ganglion offers a rich context for examining diverse biological processes, including cell migration, fate determination, adhesion, and axon guidance. Avian models have, so far, enabled key insights into craniofacial and peripheral nervous system development. Yet the molecular mechanisms driving trigeminal ganglion formation and subsequent nerve growth remain elusive. In this study, we performed RNA-sequencing at multiple stages of chick trigeminal ganglion development and generated a novel transcriptomic dataset that has been curated to illustrate temporally dynamic gene expression patterns. This publicly available resource identifies major pathways involved in trigeminal gangliogenesis, particularly with respect to the condensation and maturation of placode-derived neurons, thus inviting new lines of research into the essential processes governing trigeminal ganglion development.

3D bioprinted dynamic bioactive living construct enhances mechanotransduction-assisted rapid neural network self-organization for spinal cord injury repair

Biomimetic neural substitutes, constructed through the bottom-up assembly of cell-matrix modulus via 3D bioprinting, hold great promise for neural regeneration. However, achieving precise control over the fate of neural stem cells (NSCs) to ensure biological functionality remains challenging. Cell behaviors are closely linked to cellular dynamics and cell-matrix mechanotransduction within a 3D microenvironment. To address this, a dynamic bioactive bioink is designed to provide adaptable biomechanics and instructive biochemical cues, specifically tailored for the fate commitment of NSCs, through incorporating reversible Schiff-base bonds and bioactive motifs, N-cadherin-mimicking and BDNF-mimicking peptides. We demonstrate that the dynamic properties of 3D bioprinted living fibers alleviate the mechanical confinement on NSCs and significantly enhance their mechanosensing, spreading, migration, and matrix remodeling within the 3D matrix. Additionally, the inclusion of N-cadherin-mimicking and BDNF-mimicking peptides further enhances cells' ability to sense and respond to mechanical and neurotrophic cues provided by the surrounding matrix, which accelerates the self-organization of a functional neural network within the 3D bioprinted construct, leading to significant motor and sensory function recovery in a rat complete spinal cord injury model. This work underscores the critical role of precisely designing cell-instructive bioinks for the advanced functionality of 3D bioprinted living constructs in neural regeneration.

Targeting the mosquito prefoldin-chaperonin complex blocks Plasmodium transmission

The Plasmodium infection cycle in mosquitoes relies on numerous host factors in the vector midgut, which can be targeted with therapeutics. The mosquito prefoldin complex is needed to fold proteins and macromolecular complexes properly. Here we show that the conserved Anopheles mosquito prefoldin (PFDN)-chaperonin system is a potent transmission-blocking target for multiple Plasmodium species. Silencing any prefoldin subunit or its CCT/TRiC partner via RNA interference reduces Plasmodium falciparum oocyst loads in the mosquito midgut, as does co-feeding mosquitoes with PFDN6-specific antibody and gametocytes. Inhibition of the PFDN-CCT/TRiC chaperonin complex results in the loss of epithelial and extracellular matrix integrity, which triggers microorganism-mediated anti-Plasmodium immune priming and compromises the parasite's laminin-based immune evasion. Mouse malaria transmission-blocking vaccine and antibody co-feeding assays support its potential as a multispecies transmission-blocking target for P. falciparum and Plasmodium vivax. Further study is needed to determine the potential of this system as a transmission-blocking vaccine target.

Role of the cytoskeleton in cellular reprogramming: effects of biophysical and biochemical factors

The cytoskeleton plays a crucial role in regulating cellular behavior, acting as both a structural framework and a mediator of mechanical and biochemical signals that influence cell fate. In the context of cellular reprogramming, modifications to the cytoskeleton can have profound effects on lineage commitment and differentiation efficiency. This review explores the impact of mechanical forces such as substrate stiffness, topography, extracellular fluid viscosity, and cell seeding density on cytoskeletal organization and mechanotransduction pathways, including Rho/ROCK and YAP/TAZ signaling. Additionally, we examine the influence of biochemical agents that modulate cytoskeletal dynamics, such as actin and microtubule polymerization inhibitors, and their effects on stem cell differentiation. By understanding how cytoskeletal remodeling governs cellular identity, this review highlights potential strategies for improving reprogramming efficiency and directing cell fate by manipulating mechanical and biochemical cues.

Stem cell mechanoadaptation. I. Effect of microtubule stabilization and volume changing stresses on cytoskeletal remodeling

Here, we report on the first part of a two-part experimental series to elucidate spatiotemporal cytoskeletal remodeling, which underpins the evolution of stem cell shape and fate, and the emergence of tissue structure and function. In Part I of these studies, we first develop protocols to stabilize microtubules exogenously using paclitaxel (PAX) in a standardized model murine embryonic stem cell line (C3H/10T1/2) to maximize comparability with previously published studies. We then probe native and microtubule-stabilized stem cells' capacity to adapt to volume changing stresses effected by seeding at increasing cell densities, which emulates local compression and tissue template formation during development. Within the concentration range of 1-100 nM, microtubule-stabilized stem cells maintain viability and reduce proliferation. PAX stabilization of microtubules is associated with increased cell volume as well as flattening of the cell and nucleus. Compared to control cells, microtubule-stabilized cells exhibit thick, bundled microtubules and highly aligned, thicker and longer F-actin fibers, corresponding to an increase in the Young's modulus of the cell. Both F-actin and microtubule concentration increase with increasing PAX concentration, whereby the increase in F-actin is more prominent in the basal region of the cell. The corresponding increase in microtubule is observed more globally across the apical and basal region of the cell. Seeding at increasing target densities induces local compression on cells. This increase in local compression modulates cell volume and concomitant increases in F-actin and microtubule concentration to a greater degree than microtubule stabilization via PAX. Cells seeded at high density exhibit higher bulk modulus than corresponding cells seeded at low density. These data demonstrate the capacity of stem cells to adapt to an interplay of mechanical and chemical cues, i.e., respective compression and exogenous microtubule stabilization; the resulting cytoskeletal remodeling manifests as evolution of mechanical properties relevant to development of multicellular tissue constructs.

Investigating the interplay between environmental conditioning and nanotopographical cueing on the response of human MG63 osteoblastic cells to titanium nanotubes

Titanium nanotubular surfaces have been extensively studied for their potential use in biomedical implants due to their ability to promote relevant phenomena associated with osseointegration, among other functions. However, despite the large body of literature on the subject, potential synergistic/antagonistic effects resulting from the combined influence of environmental variables and nanotopographical cues remain poorly investigated. Specifically, it is still unclear whether the nanotube-induced variations in cellular activity are preserved across different biochemical contexts. To bridge this gap, this study systematically evaluates the combined influence of nanotopographical cues and environmental factors on human MG63 osteoblastic cells. To this end, we capitalized on a triphasic anodization protocol to create nanostructured surfaces characterized by an average nanotube inner diameter of 25 nm (NT1) and 82 nm (NT2), as well as a two-tiered honeycomb (HC) architecture. A variable glucose content was chosen as the environmental modifier due to its well-known ability to affect specific functions of MG63 cells. Alkaline phosphatase (ALP), viability/metabolic activity and proliferation were quantified to identify the suitable preconditioning window required for dictating a change in behaviour without significantly damaging cells. Successively, a combination of immunofluorescence, colorimetric assays, live cell imaging and western blots quantified viability/metabolic activity and cell proliferation, migration and differentiation as a function of the combined effects exerted by the nanostructured substrates and the glucose content. To achieve a thorough understanding of MG63 cell adaptation and response, a comparative analysis table that includes and systematically cross-analyzes all variables from this study was used for interpretation and discussion of the results. Taken together, we have demonstrated that all surfaces mitigate the negative effects of high glucose. However, nanotubular topographies, particularly NT2, elicit a more beneficial outcome in high glucose in respect to untreated titanium. In addition, while NT1 surfaces are associated with the most stable cellular response across varying glucose levels, the NT2 and HC substrates exhibit the strongest enhancement of cell migration, viability/metabolism and differentiation. Moreover, shorter-term processes such as adhesion and proliferation are favored on untreated titanium, while anodized samples support later-term events. Lastly, the role of anodized surfaces is dominant over the effects of environmental glucose, underscoring the importance of carefully considering nanoscale surface features in the design and development of cell-instructive titanium surfaces.

Shape-Directed Dynamic Assembly of Active Colloidal Metamachines

Modularly organizing active micromachines into high-grade metamachines makes a great leap for operating the microscopic world in a biomimetic way. However, modulating the nonreciprocal interactions among different colloidal motors through chemical reactions to achieve the controllable construction of active colloidal metamachines with specific dynamic properties remains challenging. Here, we report the phototactic active colloidal metamachines constructed by shape-directed dynamic self-assembly of chemically driven peanut-shaped TiO2 colloidal motors and Janus spherical Pt/SiO2 colloidal motors. The long-range diffusiophoretic attraction generated by the photocatalytic reaction dominates the sensing and collision of peanut TiO2 motors with Janus Pt/SiO2 motors. The coupling of local chemical concentration gradient fields between the two types of motors generates short-range site-selective interactions, promoting the shape-directed assembly toward active colloidal metamachines with well-defined spatial configurations. Metamachines, made of colloidal motors, exhibit configuration-dependent kinematics. The colloidal metamachines can be reversibly reconstructed by adjusting lighting conditions and can move phototactically along a predetermined path under the structured light field. Such chemically driven colloidal metamachines that integrate multiple active agents provide a significant avenue for fabricating active soft matter materials and intelligent robotic systems with advanced applications.

Chromatin-site-specific accessibility: A microtopography-regulated door into the stem cell fate

Biomaterials that mimic extracellular matrix topography are crucial in tissue engineering. Previous research indicates that certain biomimetic topography can guide stem cells toward multiple specific lineages. However, the mechanisms by which topographic cues direct stem cell differentiation remain unclear. Here, we demonstrate that microtopography influences nuclear tension in mesenchymal stem cells (MSCs), shaping chromatin accessibility and determining lineage commitment. On aligned substrates, MSCs exhibit high cytoskeletal tension along the fiber direction, creating anisotropic nuclear stress that opens chromatin sites for neurogenic, myogenic, and tenogenic genes via transcription factors like Nuclear receptor TLX (TLX). In contrast, random substrates induce isotropic nuclear stress, promoting chromatin accessibility for osteogenic and chondrogenic genes through Runt-related transcription factors (RUNX). Our findings reveal that aligned and random microtopographies direct site-specific chromatin stretch and lineage-specific gene expression, priming MSCs for distinct lineages. This study introduces a novel framework for understanding how topographic cues govern cell fate in tissue repair and regeneration.

Engineering Nanoclusters of Cell Adhesive Ligands on Biomaterial Surfaces: Superior Cell Proliferation and Myotube Formation for Skeletal Muscle Tissue Regeneration

Engineering biointerfaces with nanoscale clustering of integrin-binding cell adhesive peptides is critical for promoting receptor redistribution into signaling complexes. Skeletal muscle cells are exquisitely sensitive to integrin-mediated signaling, yet biomaterials supporting myogenesis through control of the density and nanodistribution of ligands have not been developed. Here, materials are developed with tailorable cell adhesive ligands distribution at the interface by independently controlling their global and local density to enhance myogenesis, by promoting myoblast growth and myotube formation. To this end, RGD-functionalized low-fouling polymer surfaces with global ligand densities (G) from 0-7 µg peptide/mg polymer and average local ligand densities (L) from 1-6.3 ligands/cluster, are generated and characterized. Cell studies demonstrate improvements in cell adhesion, spreading, growth, and myotube formation up to a density of 7 µg peptide/mg polymer with 4 ligands/cluster. Optimizing ligand density and distribution also promotes early myofiber maturation, identified by increased MF20 marker protein expression and sarcomere-forming myotubes. At higher ligand densities, these cell properties are decreased, indicating that ligand multivalency is a critical parameter for tailoring cell-material interactions, to a certain threshold. The findings provide new insights for designing next-generation biomaterials and hold promise for improved engineering of skeletal muscle.

Novel features of Drosophila hematopoiesis uncovered by long-term live imaging

Stem cells are subject to continuous regulation to ensure that the correct balance between stem cell differentiation and self-renewal is maintained. The dynamic and ongoing nature of stem cell regulation, as well as the complex signaling microenvironment in which stem cells are typically found, means that studying them in their endogenous environment in real time has multiple advantages over static fixed-sample approaches. We recently described a method for long-term, ex-vivo, live imaging of the blood progenitors in the Drosophila larval hematopoietic organ, the Lymph Gland (LG). This methodology has allowed us to analyze multiple aspects of fly hematopoiesis, in real time, in a manner that could not be carried out previously. Here, we describe novel insights derived from our quantitative live imaging approach. These insights include: the identification of extensive filopodia in the progenitors and description of their morphology and dynamics; visualization and quantitative analysis of JAK/STAT signaling in progenitors by the simultaneous tracking of thousands of vesicles containing internalized Domeless receptors; quantitative analysis of the location, morphology, and dynamics of mitochondria in blood progenitors; long-term tracking of patterns of cell division and migration of mature blood cell in the LG; long-term tracking of multiple cell behaviors in the distal committed progenitors; analysis of Ca2+ signaling of blood progenitors in the secondary lobes of the LG. Together, these observations illustrate the power of imaging fly hematopoiesis in real time and identify many previously undescribed processes and behaviors in the LG that are likely to play important roles in the regulation of progenitor differentiation and self-renewal.

The transcriptional landscape of the developing chick trigeminal ganglion

The trigeminal ganglion is a critical structure in the peripheral nervous system, responsible for transmitting sensations of touch, pain, and temperature from craniofacial regions to the brain. Trigeminal ganglion development depends upon intrinsic cellular programming as well as extrinsic signals exchanged by diverse cell populations. With its complex anatomy and dual cellular origin from cranial placodes and neural crest cells, the trigeminal ganglion offers a rich context for examining diverse biological processes, including cell migration, fate determination, adhesion, and axon guidance. Avian models have, so far, enabled key insights into craniofacial and peripheral nervous system development. Yet, the molecular mechanisms driving trigeminal ganglion formation and subsequent nerve growth remain elusive. In this study, we performed RNA-sequencing at multiple stages of chick trigeminal ganglion development and generated a novel transcriptomic dataset that has been curated to illustrate temporally dynamic gene expression patterns. This publicly available resource identifies major pathways involved in trigeminal gangliogenesis, particularly with respect to the condensation and maturation of placode-derived neurons, thus inviting new lines of research into the essential processes governing trigeminal ganglion development.

Recent advances in layer-by-layer assembly scaffolds for co-delivery of bioactive molecules for bone regeneration: an updated review

Orthopedic implants have faced challenges in treating bone defects due to various factors, including inadequate osseointegration, oxidative stress, bacterial infection, immunological rejection, and poor individualized treatment. These challenges profoundly affect both the results of treatment and patients' daily lives. There is great promise for the layer-by-layer (LbL) assembly method in tissue engineering. The method primarily relies on electrostatic attraction and entails the consecutive deposition of electrolyte complexes with opposite charges onto a substrate, leading to the formation of homogeneous single layers that can be quickly deposited to produce nanolayer films. LbL has attracted considerable interest as a coating technology because of its ease of production, cost-effectiveness, and capability to apply diverse biomaterial coatings without compromising the primary bio-functional properties of the substrate materials. This review will look into the fundamentals and evolution of LbL in orthopedics, provide an analysis of the chemical strategy used to prepare bone implants with LbL and introduce the application of LbL bone implants in orthopedics over recent years. Among the many potential uses of LbL, such as the implementation of sustained-release and programmed drug delivery, which in turn promotes the osseointegration and the development of new blood vessels, as well as antibacterial, antioxidant, and other similar applications. In addition, we offer a thorough examination of cell behavior and biomaterial interaction to facilitate the advancement of next-generation LbL films for tissue engineering.

Slow H2S-Releasing Donors and 3D Printable Arrays Cellular Models in Osteo-Differentiation of Mesenchymal Stem Cells for Personalized Therapies

The effects of the hydrogen sulfide (H2S) slow-releasing donor, named GSGa, a glutathione-conjugate water-soluble garlic extract, on human mesenchymal stem cells (hMSCs) in both bidimensional (2D) and three-dimensional (3D) cultures were investigated, demonstrating increased expression of the antioxidant enzyme HO-1 and decreased expression of the pro-inflammatory cytokine interleukin-6 (IL-6). The administration of the H2S donor can therefore increase the expression of antioxidant enzymes, which may have potential therapeutic applications in osteoarthritis (OA). Moreover, GSGa was able to promote the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), but not of cardiac mesenchymal stem cells (cMSCs) in a 2D culture system. This result highlights the varying sensitivity of hMSCs to the H2S donor GSGa, suggesting that the induction of osteogenic differentiation in stem cells by chemical factors is dependent on the tissue of origin. Additionally, a 3D-printable mesenchymal stem cells-bone matrix array (MSCBM), designed to closely mimic the stiffness of bone tissue, was developed to serve as a versatile tool for evaluating the effects of drugs and stem cells on bone repair in chronic diseases, such as OA. We demonstrated that the osteogenic differentiation process in cMSCs can be induced just by simulating bone stiffness in a 3D system. The expression of osteocalcin, RUNX2, and antioxidant enzymes was also assessed after treating MSCs with GSGa and/or increasing the stiffness of the culture environment. The printability of the array may enable better customization of the cavities, enabling an accurate replication of real bone defects. This could optimize the BM array to mimic bone defects not only in terms of stiffness, but also in terms of shape. This culture system may enable a rapid screening of antioxidant and anti-inflammatory compounds, facilitating a more personalized approach to regenerative therapy.

Arp2/3 complex activity enables nuclear YAP for naïve pluripotency of human embryonic stem cells

Our understanding of the transitions of human embryonic stem cells (hESCs) between distinct stages of pluripotency relies predominantly on regulation by transcriptional and epigenetic programs with limited insight on the role of established morphological changes. We report remodeling of the actin cytoskeleton of hESCs as they transition from primed to naïve pluripotency which includes assembly of a ring of contractile actin filaments encapsulating colonies of naïve hESCs. Activity of the Arp2/3 complex is required for formation of the actin ring, to establish uniform cell mechanics within naïve colonies, to promote nuclear translocation of the Hippo pathway effectors YAP and TAZ, and for effective transition to naïve pluripotency. RNA-sequencing analysis confirms that Arp2/3 complex activity regulates Hippo signaling in hESCs, and impaired naïve pluripotency with inhibited Arp2/3 complex activity is rescued by expressing a constitutively active, nuclear-localized YAP-S127A. Moreover, expression of YAP-S127A partially restores the actin filament fence with Arp2/3 complex inhibition, suggesting that actin filament remodeling is both upstream and downstream of YAP activity. These new findings on the cell biology of hESCs reveal a mechanism for cytoskeletal dynamics coordinating cell mechanics to regulate gene expression and facilitate transitions between pluripotency states.

Compression-induced apoptosis of fibroblasts and myofibroblasts in an in vitro model of pulmonary fibrosis by alginate/gelatin scaffold

Pulmonary fibrosis leads to increased mortality but is poorly understood. Fibrotic progression is associated with abnormal wound repair and an increase in myofibroblast cell populations. Here we investigate how the myofibroblast population is impacted by unique compression-induced apoptosis derived from mechanical strain characteristic of asthma. Using a mechanical device, both static and dynamic mechanical strains were applied to alginate/gelatin/CaCl2 scaffolds containing fibroblasts and myofibroblasts. As cell groups were stimulated with 30 % static strain for 12 h, fibroblast and myofibroblast cell groups showed increased cell apoptosis by 5.55 % and 19.56 %, respectively, compared to control groups. Additionally, myofibroblasts exhibited higher susceptibility to apoptosis induction than did fibroblasts. Comparing dynamic and static loading modes, dynamic loading resulted in a higher apoptosis rate of fibroblast and myofibroblast cells, indicating its potential to induce apoptosis effectively. These findings suggest that mechanical stimulation can be considered a promising approach to induce apoptosis in myofibroblasts, thus offering the potential for future approaches to treating pulmonary fibrosis. Moreover, mechanical loads can be designed for other diseases, selectively reducing or increasing apoptosis in either hard or soft cell groups, based on specific application needs.

Early heart development: examining the dynamics of function-form emergence

During early embryonic development, the heart undergoes a remarkable and complex transformation, acquiring its iconic four-chamber structure whilst concomitantly contracting to maintain its essential function. The emergence of cardiac form and function involves intricate interplays between molecular, cellular, and biomechanical events, unfolding with precision in both space and time. The dynamic morphological remodelling of the developing heart renders it particularly vulnerable to congenital defects, with heart malformations being the most common type of congenital birth defect (∼35% of all congenital birth defects). This mini-review aims to give an overview of the morphogenetic processes which govern early heart formation as well as the dynamics and mechanisms of early cardiac function. Moreover, we aim to highlight some of the interplay between these two processes and discuss how recent findings and emerging techniques/models offer promising avenues for future exploration. In summary, the developing heart is an exciting model to gain fundamental insight into the dynamic relationship between form and function, which will augment our understanding of cardiac congenital defects and provide a blueprint for potential therapeutic strategies to treat disease.

Differentiation of Spiral Ganglion Neurons from Human Dental Pulp Stem Cells: A Further Step towards Autologous Auditory Nerve Recovery

The degeneration of spiral ganglion neurons (SGNs), which convey auditory signals from hair cells to the brain, can be a primary cause of sensorineural hearing loss (SNHL) or can occur secondary to hair cell loss. Emerging therapies for SNHL include the replacement of damaged SGNs using stem cell-derived otic neuronal progenitors (ONPs). However, the availability of renewable, accessible, and patient-matched sources of human stem cells is a prerequisite for successful replacement of the auditory nerve. In this study, we derived ONP and SGN-like cells by a reliable and reproducible stepwise guidance differentiation procedure of self-renewing human dental pulp stem cells (hDPSCs). This in vitro differentiation protocol relies on the modulation of BMP and TGFβ pathways using a free-floating 3D neurosphere method, followed by differentiation on a Geltrex-coated surface using two culture paradigms to modulate the major factors and pathways involved in early otic neurogenesis. Gene and protein expression analyses revealed efficient induction of a comprehensive panel of known ONP and SGN-like cell markers during the time course of hDPSCs differentiation. Atomic force microscopy revealed that hDPSC-derived SGN-like cells exhibit similar nanomechanical properties as their in vivo SGN counterparts. Furthermore, spiral ganglion neurons from newborn rats come in close contact with hDPSC-derived ONPs 5 days after co-culturing. Our data demonstrate the capability of hDPSCs to generate SGN-like neurons with specific lineage marker expression, bipolar morphology, and the nanomechanical characteristics of SGNs, suggesting that the neurons could be used for next-generation cochlear implants and/or inner ear cell-based strategies for SNHL.

Recent Advances in Nanomaterials for Modulation of Stem Cell Differentiation and Its Therapeutic Applications

Challenges in directed differentiation and survival limit the clinical use of stem cells despite their promising therapeutic potential in regenerative medicine. Nanotechnology has emerged as a powerful tool to address these challenges and enable precise control over stem cell fate. In particular, nanomaterials can mimic an extracellular matrix and provide specific cues to guide stem cell differentiation and proliferation in the field of nanotechnology. For instance, recent studies have demonstrated that nanostructured surfaces and scaffolds can enhance stem cell lineage commitment modulated by intracellular regulation and external stimulation, such as reactive oxygen species (ROS) scavenging, autophagy, or electrical stimulation. Furthermore, nanoframework-based and upconversion nanoparticles can be used to deliver bioactive molecules, growth factors, and genetic materials to facilitate stem cell differentiation and tissue regeneration. The increasing use of nanostructures in stem cell research has led to the development of new therapeutic approaches. Therefore, this review provides an overview of recent advances in nanomaterials for modulating stem cell differentiation, including metal-, carbon-, and peptide-based strategies. In addition, we highlight the potential of these nano-enabled technologies for clinical applications of stem cell therapy by focusing on improving the differentiation efficiency and therapeutics. We believe that this review will inspire researchers to intensify their efforts and deepen their understanding, thereby accelerating the development of stem cell differentiation modulation, therapeutic applications in the pharmaceutical industry, and stem cell therapeutics.

Enhanced Piezoelectric Performance of PVDF-TrFE Nanofibers through Annealing for Tissue Engineering Applications

This study investigates bioelectric stimulation's role in tissue regeneration by enhancing the piezoelectric properties of tissue-engineered grafts using annealed poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) scaffolds. Annealing at temperatures of 80°C, 100°C, 120°C, and 140°C was assessed for its impact on material properties and physiological utility. Analytical techniques such as Differential Scanning Calorimetry (DSC), Fourier-Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) revealed increased crystallinity with higher annealing temperatures, peaking in β-phase content and crystallinity at 140°C. Scanning Electron Microscopy (SEM) showed that 140°C annealed scaffolds had enhanced lamellar structures, increased porosity, and maximum piezoelectric response. Mechanical tests indicated that 140°C annealing improved elastic modulus, tensile strength, and substrate stiffness, aligning these properties with physiological soft tissues. In vitro assessments in Schwann cells demonstrated favorable responses, with increased cell proliferation, contraction, and extracellular matrix attachment. Additionally, genes linked to extracellular matrix production, vascularization, and calcium signaling were upregulated. The foreign body response in C57BL/6 mice, evaluated through Hematoxylin and Eosin (H&E) and Picrosirius Red staining, showed no differences between scaffold groups, supporting the potential for future functional evaluation of the annealed group in tissue repair.

Ultrasound-triggered three dimensional hyaluronic acid hydrogel promotes in vitro and in vivo reprogramming into induced pluripotent stem cells

Cellular reprogramming technologies have been developed with different physicochemical factors to improve the reprogramming efficiencies of induced pluripotent stem cells (iPSCs). Ultrasound is a clinically applied noncontact biophysical factor known for regulating various cellular behaviors but remains uninvestigated for cellular reprogramming. Here, we present a new reprogramming strategy using low-intensity ultrasound (LIUS) to improve cellular reprogramming of iPSCs in vitro and in vivo. Under 3D microenvironment conditions, increased LIUS stimulation shows enhanced cellular reprogramming of the iPSCs. The cellular reprogramming process facilitated by LIUS is accompanied by increased mesenchymal to epithelial transition and histone modification. LIUS stimulation transiently modulates the cytoskeletal rearrangement, along with increased membrane fluidity and mobility to increase HA/CD44 interactions. Furthermore, LIUS stimulation with HA hydrogel can be utilized in application of both human cells and in vivo environment, for enhanced reprogrammed cells into iPSCs. Thus, LIUS stimulation with a combinatorial 3D microenvironment system can improve cellular reprogramming in vitro and in vivo environments, which can be applied in various biomedical fields.

Advances in 3D tissue models for neural engineering: self-assembled versus engineered tissue models

Neural tissue engineering has emerged as a promising field that aims to create functional neural tissue for therapeutic applications, drug screening, and disease modelling. It is becoming evident in the literature that this goal requires development of three-dimensional (3D) constructs that can mimic the complex microenvironment of native neural tissue, including its biochemical, mechanical, physical, and electrical properties. These 3D models can be broadly classified as self-assembled models, which include spheroids, organoids, and assembloids, and engineered models, such as those based on decellularized or polymeric scaffolds. Self-assembled models offer advantages such as the ability to recapitulate neural development and disease processes in vitro, and the capacity to study the behaviour and interactions of different cell types in a more realistic environment. However, self-assembled constructs have limitations such as lack of standardised protocols, inability to control the cellular microenvironment, difficulty in controlling structural characteristics, reproducibility, scalability, and lengthy developmental timeframes. Integrating biomimetic materials and advanced manufacturing approaches to present cells with relevant biochemical, mechanical, physical, and electrical cues in a controlled tissue architecture requires alternate engineering approaches. Engineered scaffolds, and specifically 3D hydrogel-based constructs, have desirable properties, lower cost, higher reproducibility, long-term stability, and they can be rapidly tailored to mimic the native microenvironment and structure. This review explores 3D models in neural tissue engineering, with a particular focus on analysing the benefits and limitations of self-assembled organoids compared with hydrogel-based engineered 3D models. Moreover, this paper will focus on hydrogel based engineered models and probe their biomaterial components, tuneable properties, and fabrication techniques that allow them to mimic native neural tissue structures and environment. Finally, the current challenges and future research prospects of 3D neural models for both self-assembled and engineered models in neural tissue engineering will be discussed.

Building better habitats: Spatiotemporal signaling cues in 3D biointerfaces for tailored cellular functionality

A promising research direction in the field of biological engineering is the design and functional programming of three-dimensional (3D) biointerfaces designed to support living cell functionality and growth in vitro, offering a route to precisely regulate cellular behaviors and phenotypes for addressing therapeutic challenges. While traditional two-dimensional (2D) biointerfaces have provided valuable insights, incorporating specific signaling cues into a 3D biointeractive microenvironment at the right locations and time is now recognized as crucial for accurately programming cellular decision-making and communication processes. This approach aims to engineer cell-centric microenvironments with the potential to recapitulate complex biological functions into a finite set of growing cellular organizations. Additionally, they provide insights into the hierarchical logic governing the relationship between molecular components and higher-order multicellular functionality. The functional live cell-based microenvironment engineered through such innovative biointerfaces has the potential to be used as an in vitro model system for expanding our understanding of cellular behaviors or as a therapeutic habitat where cellular functions can be reprogrammed.

Adipose-derived mesenchymal stem cells' adipogenesis chemistry analyzed by FTIR and Raman metrics

The full understanding of molecular mechanisms of cell differentiation requires a holistic view. Here we combine label-free FTIR and Raman hyperspectral imaging with data mining to detect the molecular cell composition enabling noninvasive monitoring of cell differentiation and identifying biochemical heterogeneity. Mouse adipose-derived mesenchymal stem cells (AD-MSCs) undergoing adipogenesis were followed by Raman and FT-IR imaging, Oil Red, and immunofluorescence. A workflow of the data analysis (IRRSmetrics4stem) was designed to identify spectral predictors of adipogenesis and test machine-learning (ML) methods (hierarchical clustering, PCA, PLSR) for the control of the AD-MSCs differentiation degree. IRRSmetrics4stem provided insights into the chemism of adipogenesis. With single-cell tracking, we established IRRS metrics for lipids, proteins, and DNA variations during AD-MSCs differentiation. The over 90% predictive efficiency of the selected ML methods proved the high sensitivity of the IRRS metrics. Importantly, the IRRS metrics unequivocally recognize a switch from proliferation to differentiation. This study introduced a new bioassay identifying molecular markers indicating molecular transformations and delivering rapid and machine learning-based monitoring of adipogenesis that can be relevant to other differentiation processes. Thus, we introduce a novel, rapid, machine learning-based bioassay to identify molecular markers of adipogenesis. It can be relevant to identification of differentiation-related molecular processes in other cell types, and beyond the cell differentiation including progression of different cellular pathophysiologies reconstituted in vitro.

Effects of the MCF-7 Exhausted Medium on hADSC Behaviour

Stem cells possess the ability to differentiate into different lineages and the ability to self-renew, thus representing an excellent tool for regenerative medicine. They can be isolated from different tissues, including the adipose tissue. Adipose tissue and human adipose-derived stem cells (hADSCs) are privileged candidates for regenerative medicine procedures or other plastic reconstructive surgeries. The cellular environment is able to influence the fate of stem cells residing in the tissue. In a previous study, we exposed hADSCs to an exhausted medium of a breast cancer cell line (MCF-7) recovered at different days (4, 7, and 10 days). In the same paper, we inferred that the medium was able to influence the behaviour of stem cells. Considering these results, in the present study, we evaluated the expression of the major genes related to adipogenic and osteogenic differentiation. To confirm the gene expression data, oil red and alizarin red colorimetric assays were performed. Lastly, we evaluated the expression of miRNAs influencing the differentiation process and the proliferation rate, maintaining a proliferative state. The data obtained confirmed that cells exposed to the medium maintained a stem and proliferative state that could lead to a risky proliferative phenotype.

3D bioprinting of dense cellular structures within hydrogels with spatially controlled heterogeneity

Embedded bioprinting is an emerging technology for precise deposition of cell-laden or cell-only bioinks to construct tissue like structures. Bioink is extruded or transferred into a yield stress hydrogel or a microgel support bath allowing print needle motion during printing and providing temporal support for the printed construct. Although this technology has enabled creation of complex tissue structures, it remains a challenge to develop a support bath with user-defined extracellular mimetic cues and their spatial and temporal control. This is crucial to mimic the dynamic nature of the native tissue to better regenerate tissues and organs. To address this, we present a bioprinting approach involving printing of a photocurable viscous support layer and bioprinting of a cell-only or cell-laden bioink within this viscous layer followed by brief exposure to light to partially crosslink the support layer. This approach does not require shear thinning behavior and is suitable for a wide range of photocurable hydrogels to be used as a support. It enables multi-material printing to spatially control support hydrogel heterogeneity including temporal delivery of bioactive cues (e.g. growth factors), and precise patterning of dense multi-cellular structures within these hydrogel supports. Here, dense stem cell aggregates are printed within methacrylated hyaluronic acid-based hydrogels with patterned heterogeneity to spatially modulate human mesenchymal stem cell osteogenesis. This study has significant impactions on creating tissue interfaces (e.g. osteochondral tissue) in which spatial control of extracellular matrix properties for patterned stem cell differentiation is crucial.

Can repetitive mechanical motion cause structural damage to axons?

Biological structures have evolved to very efficiently generate, transmit, and withstand mechanical forces. These biological examples have inspired mechanical engineers for centuries and led to the development of critical insights and concepts. However, progress in mechanical engineering also raises new questions about biological structures. The past decades have seen the increasing study of failure of engineered structures due to repetitive loading, and its origin in processes such as materials fatigue. Repetitive loading is also experienced by some neurons, for example in the peripheral nervous system. This perspective, after briefly introducing the engineering concept of mechanical fatigue, aims to discuss the potential effects based on our knowledge of cellular responses to mechanical stresses. A particular focus of our discussion are the effects of mechanical stress on axons and their cytoskeletal structures. Furthermore, we highlight the difficulty of imaging these structures and the promise of new microscopy techniques. The identification of repair mechanisms and paradigms underlying long-term stability is an exciting and emerging topic in biology as well as a potential source of inspiration for engineers.

Effects of mitochondrial transplantation on chronic pressure wound healing in a human patient

BACKGROUND AIMS

Wound healing is a multistage process that requires a concerted effort of various cell types. The intricate processes involved in the healing of wounds result in high energy requirements. Furthermore, mitochondria play a crucial role in the healing process because of their involvement in neo angiogenesis, growth factor synthesis, and cell differentiation. It is unclear how mitochondria transplantation, a promising new approach, influences wound healing.

METHODS

In this study, healthy autologous mitochondria obtained from skeletal muscle were injected into chronic pressure wounds as an intervention to promote wound healing.

RESULTS

Mitochondrial transplantation accelerated wound healing by reducing wound size, increasing granulation tissue, and hastening epithelialization.

CONCLUSIONS

This study is the first to demonstrate the therapeutic efficacy of mitochondrial transplantation in wound healing.

Advanced 3D imaging and organoid bioprinting for biomedical research and therapeutic applications

Organoid cultures offer a valuable platform for studying organ-level biology, allowing for a closer mimicry of human physiology compared to traditional two-dimensional cell culture systems or non-primate animal models. While many organoid cultures use cell aggregates or decellularized extracellular matrices as scaffolds, they often lack precise biochemical and biophysical microenvironments. In contrast, three-dimensional (3D) bioprinting allows precise placement of organoids or spheroids, providing enhanced spatial control and facilitating the direct fusion for the formation of large-scale functional tissues in vitro. In addition, 3D bioprinting enables fine tuning of biochemical and biophysical cues to support organoid development and maturation. With advances in the organoid technology and its potential applications across diverse research fields such as cell biology, developmental biology, disease pathology, precision medicine, drug toxicology, and tissue engineering, organoid imaging has become a crucial aspect of physiological and pathological studies. This review highlights the recent advancements in imaging technologies that have significantly contributed to organoid research. Additionally, we discuss various bioprinting techniques, emphasizing their applications in organoid bioprinting. Integrating 3D imaging tools into a bioprinting platform allows real-time visualization while facilitating quality control, optimization, and comprehensive bioprinting assessment. Similarly, combining imaging technologies with organoid bioprinting can provide valuable insights into tissue formation, maturation, functions, and therapeutic responses. This approach not only improves the reproducibility of physiologically relevant tissues but also enhances understanding of complex biological processes. Thus, careful selection of bioprinting modalities, coupled with appropriate imaging techniques, holds the potential to create a versatile platform capable of addressing existing challenges and harnessing opportunities in these rapidly evolving fields.

Mechanical guidance to self-organization and pattern formation of stem cells

The self-organization of stem cells (SCs) constitutes the fundamental basis of the development of biological organs and structures. SC-driven patterns are essential for tissue engineering, yet unguided SCs tend to form chaotic patterns, impeding progress in biomedical engineering. Here, we show that simple geometric constraints can be used as an effective mechanical modulation approach that promotes the development of controlled self-organization and pattern formation of SCs. Using the applied SC guidance with geometric constraints, we experimentally uncover a remarkable deviation in cell aggregate orientation from a random direction to a specific orientation. Subsequently, we propose a dynamic mechanical framework, including cells, the extracellular matrix (ECM), and the culture environment, to characterize the specific orientation deflection of guided cell aggregates relative to initial geometric constraints, which agrees well with experimental observation. Based on this framework, we further devise various theoretical strategies to realize complex biological patterns, such as radial and concentric structures. Our study highlights the key role of mechanical factors and geometric constraints in governing SCs' self-organization. These findings yield critical insights into the regulation of SC-driven pattern formation and hold great promise for advancements in tissue engineering and bioactive material design for regenerative application.

SRRM2 splicing factor modulates cell fate in early development

Embryo development is an orchestrated process that relies on tight regulation of gene expression to guide cell differentiation and fate decisions. The Srrm2 splicing factor has recently been implicated in developmental disorders and diseases, but its role in early mammalian development remains unexplored. Here, we show that Srrm2 dosage is critical for maintaining embryonic stem cell pluripotency and cell identity. Srrm2 heterozygosity promotes loss of stemness, characterised by the coexistence of cells expressing naive and formative pluripotency markers, together with extensive changes in gene expression, including genes regulated by serum-response transcription factor (SRF) and differentiation-related genes. Depletion of Srrm2 by RNA interference in embryonic stem cells shows that the earliest effects of Srrm2 heterozygosity are specific alternative splicing events on a small number of genes, followed by expression changes in metabolism and differentiation-related genes. Our findings unveil molecular and cellular roles of Srrm2 in stemness and lineage commitment, shedding light on the roles of splicing regulators in early embryogenesis, developmental diseases and tumorigenesis.

The potential role of mechanotransduction in the management of pediatric calvarial bone flap repair

Pediatric patients suffering traumatic brain injuries may require a decompressive craniectomy to accommodate brain swelling by removing a portion of the skull. Once the brain swelling subsides, the preserved calvarial bone flap is ideally replaced as an autograft during a cranioplasty to restore protection of the brain, as it can reintegrate and grow with the patient during immature skeletal development. However, pediatric patients exhibit a high prevalence of calvarial bone flap resorption post-cranioplasty, causing functional and cosmetic morbidity. This review examines possible solutions for mitigating pediatric calvarial bone flap resorption by delineating methods of stimulating mechanosensitive cell populations with mechanical forces. Mechanotransduction plays a critical role in three main cell types involved with calvarial bone repair, including mesenchymal stem cells, osteoblasts, and dural cells, through mechanisms that could be exploited to promote osteogenesis. In particular, physiologically relevant mechanical forces, including substrate deformation, external forces, and ultrasound, can be used as tools to stimulate bone repair in both in vitro and in vivo systems. Ultimately, combating pediatric calvarial flap resorption may require a combinatorial approach using both cell therapy and bioengineering strategies.

Spatial Control of Arp2/3-Induced Actin Polymerization on Phase-Separated Giant Unilamellar Vesicles

Deciphering the physical mechanisms underlying cell shape changes, while avoiding the cellular interior's complexity, involves the development of controlled basic biomimetic systems that imitate cell functions. In particular, the reconstruction of cytoskeletal dynamics on cell-sized giant unilamellar vesicles (GUVs) has allowed for the reconstituting of some cell-like processes in vitro. In fact, such a bottom-up strategy could be the basis for forming protocells able to reorganize or even move autonomously. However, reconstituting the subtle and controlled dynamics of the cytoskeleton-membrane interface in vitro remains an experimental challenge. Taking advantage of the lipid-induced segregation of an actin polymerization activator, we present a system that targets actin polymerization in specific domains of phase-separated GUVs. We observe actin networks localized on Lo, Ld, or on both types of domains and the actin-induced deformation or reorganization of these domains. These results suggest that the system we have developed here could pave the way for future experiments further detailing the interplay between actin dynamics and membrane heterogeneities.

How Hydrogel Stiffness Affects Adipogenic Differentiation of Mesenchymal Stem Cells under Controlled Morphology

Matrix stiffness has been disclosed as an essential regulator of cell fate. However, it is barely studied how the matrix stiffness affects stem cell functions when cell morphology changes. Thus, in this study, the effect of hydrogel stiffness on adipogenic differentiation of human bone-marrow-derived mesenchymal stem cells (hMSCs) with controlled morphology was investigated. Micropatterns of different size and elongation were prepared by a photolithographical micropatterning technique. The hMSCs were cultured on the micropatterns and showed a different spreading area and elongation following the geometry of the underlying micropatterns. The cells with controlled morphology were embedded in agarose hydrogels of different stiffnesses. The cells showed a different level of adipogenic differentiation that was dependent on both hydrogel stiffness and cell morphology. Adipogenic differentiation became strong when the cell spreading area decreased and hydrogel stiffness increased. Adipogenic differentiation did not change with cell elongation. Therefore, cell spreading area and hydrogel stiffness could synergistically affect adipogenic differentiation of hMSCs, while cell elongation did not affect adipogenic differentiation. A change of cell morphology and hydrogel stiffness was accompanied by actin filament alignment that was strongly related to adipogenic differentiation. The results indicated that cell morphology could affect cellular sensitivity to hydrogel stiffness. The results will provide useful information for the elucidation of the interaction of stem cells and their microenvironmental biomechanical cues.

Controlling differentiation of stem cells via bioactive disordered cues

Ideal bone tissue engineering is to induce bone regeneration through the synergistic integration of biomaterial scaffolds, bone progenitor cells, and bone-forming factors. Biomimetic scaffolds imitate the native extracellular matrix (ECM) and are often utilized in vitro as analogues of the natural ECM to facilitate investigations of cell-ECM interactions and processes. In vivo, the cellular microenvironment has a crucial impact on regulating cell behavior and functions. A PET surface was activated and then functionalized with mimetic peptides to promote human mesenchymal stem cell (hMSC) adhesion and differentiation into an osteogenic lineage. Spray technology was used to randomly micropattern peptides (RGD and BMP-2 mimetic peptides) on the PET surface. The distribution of the peptides grafted on the surface, the roughness of the surfaces and the chemistry of the surfaces in each step of the treatment were ascertained by atomic force microscopy, fluorescence microscopy, time-of-flight secondary ion mass spectrometry, Toluidine Blue O assay, and X-ray photoelectron spectroscopy. Subsequently, cell lineage differentiation was evaluated by quantifying the expression of immunofluorescence markers: osteoblast markers (Runx-2, OPN) and osteocyte markers (E11, DMP1, and SOST). In this article, we hypothesized that a unique combination of bioactive micro/nanopatterns on a polymer surface improves the rate of morphology change and enhances hMSC differentiation. In DMEM, after 14 days, disordered micropatterned surfaces with RGD and BMP-2 led to a higher osteoblast marker expression than surfaces with a homogeneous dual peptide conjugation. Finally, hMSCs cultured in osteogenic differentiation medium (ODM) showed accelerated cell differentiation. In ODM, our results highlighted the expression of osteocyte markers when hMSCs were seeded on PET surfaces with random micropatterns.

Glioblastoma Microenvironment and Invasiveness: New Insights and Therapeutic Targets

Glioblastoma (GBM) is the most common and malignant primary brain cancer in adults. Without treatment the mean patient survival is approximately 6 months, which can be extended to 15 months with the use of multimodal therapies. The low effectiveness of GBM therapies is mainly due to the tumor infiltration into the healthy brain tissue, which depends on GBM cells' interaction with the tumor microenvironment (TME). The interaction of GBM cells with the TME involves cellular components such as stem-like cells, glia, endothelial cells, and non-cellular components such as the extracellular matrix, enhanced hypoxia, and soluble factors such as adenosine, which promote GBM's invasiveness. However, here we highlight the role of 3D patient-derived glioblastoma organoids cultures as a new platform for study of the modeling of TME and invasiveness. In this review, the mechanisms involved in GBM-microenvironment interaction are described and discussed, proposing potential prognosis biomarkers and new therapeutic targets.