Harnessing Sphingosine-1-Phosphate Signaling and Nanotopographical Cues To Regulate Skeletal Muscle Maturation and Vascularization

Selective Induction of Molecular Assembly to Tissue-Level Anisotropy on Peptide-Based Optoelectronic Cardiac Biointerfaces

The conduction efficiency of ions in excitable tissues and of charged species in organic conjugated materials both benefit from having ordered domains and anisotropic pathways. In this study, a photocurrent-generating cardiac biointerface is presented, particularly for investigating the sensitivity of cardiomyocytes to geometrically comply to biomacromolecular cues differentially assembled on a conductive nanogrooved substrate. Through a polymeric surface-templated approach, photoconductive substrates with symmetric peptide-quaterthiophene (4T)-peptide units assembled as 1D nanostructures on nanoimprinted polyalkylthiophene (P3HT) surface are developed. The 4T-based peptides studied here can form 1D nanostructures on prepatterned polyalkylthiophene substrates, as directed by hydrogen bonding, aromatic interactions between 4T and P3HT, and physical confinement on the nanogrooves. It is observed that smaller 4T-peptide units that can achieve a higher degree of assembly order within the polymeric templates serve as a more efficient driver of cardiac cytoskeletal anisotropy than merely presenting aligned -RGD bioadhesive epitopes on a nanotopographic surface. These results unravel some insights on how cardiomyocytes perceive submicrometer dimensionality, local molecular order, and characteristics of surface cues in their immediate environment. Overall, the work offers a cardiac patterning platform that presents the possibility of a gene modification-free cardiac photostimulation approach while controlling the conduction directionality of the biotic and abiotic components.

Emerging Therapeutic Strategies in Sarcopenia: An Updated Review on Pathogenesis and Treatment Advances

Sarcopenia is a prevalent degenerative skeletal muscle condition in the elderly population, posing a tremendous burden on diseased individuals and healthcare systems worldwide. Conventionally, sarcopenia is currently managed through nutritional interventions, physical therapy, and lifestyle modification, with no pharmaceutical agents being approved for specific use in this disease. As the pathogenesis of sarcopenia is still poorly understood and there is no treatment recognized as universally effective, recent research efforts have been directed at better comprehending this illness and diversifying treatment strategies. In this respect, this paper overviews the new advances in sarcopenia treatment in correlation with its underlying mechanisms. Specifically, this review creates an updated framework for sarcopenia, describing its etiology, pathogenesis, risk factors, and conventional treatments, further discussing emerging therapeutic approaches like new drug formulations, drug delivery systems, stem cell therapies, and tissue-engineered scaffolds in more detail.

NanoIEA: A Nanopatterned Interdigitated Electrode Array-Based Impedance Assay for Real-Time Measurement of Aligned Endothelial Cell Barrier Functions

A nanopatterned interdigitated electrode array (nanoIEA)-based impedance assay is developed for quantitative real-time measurement of aligned endothelial cell (EC) barrier functions in vitro. A bioinspired poly(3,4-dihydroxy-L-phenylalanine) (poly (l-DOPA)) coating is applied to improve the human brain EC adhesion onto the Nafion nanopatterned surfaces. It is found that a poly (l-DOPA)-coated Nafion grooved nanopattern makes the human brain ECs orient along the nanopattern direction. Aligned human brain ECs on Nafion nanopatterns exhibit increased expression of genes encoding tight and adherens junction proteins. Aligned human brain ECs also have enhanced impedance and resistance versus unaligned ones. Treatment with a glycogen synthase kinase-3 inhibitor (GSK3i) further increases impedance and resistance, suggesting synergistic effects occur on the cell-cell tightness of in vitro human brain ECs via a combination of anisotropic matrix nanotopography and GSK3i treatment. It is found that this enhanced cell-cell tightness of the combined approach is accompanied by increased expression of claudin protein. These data demonstrate that the proposed nanoIEA assay integrated with poly (l-DOPA)-coated Nafion nanopatterns and interdigitated electrode arrays can make not only biomimetic aligned ECs, but also enable real-time measurement of the enhanced barrier functions of aligned ECs via tighter cell-cell junctions.

Nanotopographical Cues Tune the Therapeutic Potential of Extracellular Vesicles for the Treatment of Aged Skeletal Muscle Injuries

Skeletal muscle regeneration relies on the tightly temporally regulated lineage progression of muscle stem/progenitor cells (MPCs) from activation to proliferation and, finally, differentiation. However, with aging, MPC lineage progression is disrupted and delayed, ultimately causing impaired muscle regeneration. Extracellular vesicles (EVs) have attracted broad attention as next-generation therapeutics for promoting tissue regeneration. As a next step toward clinical translation, strategies to manipulate EV effects on downstream cellular targets are needed. Here, we developed an engineering strategy to tune the therapeutic potential of EVs using nanotopographical cues. We found that EVs released by young MPCs cultured on flat substrates (fEVs) promoted the proliferation of aged MPCs while EVs released by MPCs cultured on nanogratings (nEVs) promoted myogenic differentiation. We then employed a bioengineered 3D muscle aging model to optimize the administration protocol and test the therapeutic potential of fEVs and nEVs in a high-throughput manner. We found that the sequential administration first of fEVs during the phase of MPC proliferative expansion (i.e., 1 day after injury) followed by nEV administration at the stage of MPC differentiation (i.e., 3 days after injury) enhanced aged muscle regeneration to a significantly greater extent than fEVs and nEVs delivered either in isolation or mixed. The beneficial effects of the sequential EV treatment strategy were further validated in vivo, as evidenced by increased myofiber size and improved functional recovery. Collectively, our study demonstrates the ability of topographical cues to tune EV therapeutic potential and highlights the importance of optimizing the EV administration strategy to accelerate aged skeletal muscle regeneration.

Weight and skeletal muscle loss with cabozantinib in metastatic renal cell carcinoma

BACKGROUND

Cabozantinib, a standard of care metastatic renal cell carcinoma (mRCC), may be associated with weight and muscle loss. These effects of new generation VEGFR tyrosine kinase inhibitor on muscle mass loss are poorly described.

METHODS

All cabozantinib-treated mRCC patients from January 2014 to February 2019 in our institution were included. Clinical data including weight were collected during therapy. Computed tomography images were centrally reviewed for response assessment, and axial sections at the third lumbar vertebrae were used to measure the total muscle area. Toxicities and cabozantinib outcomes were evaluated. Co-primary endpoints included skeletal muscle loss and weight loss (WL), longitudinally evaluated during treatment. WL has been classified according to CTCAEv5.0: Grade 1 (loss of 5 to <10% of baseline body weight), Grade 2 (loss of 10% to <20% of baseline body weight), and Grades 3-4 (loss >20% of baseline body weight).

RESULTS

Patients were mostly men (70.3%), median age was 59.2 (range: 22.0-78.0) years, and median baseline body mass index was 25.0 (range: 16.4-49.3) kg/cm² . Prognosis according to International Metastatic RCC Database Consortium score was good, intermediate, and poor for 13 (13.0%), 63 (63.0%), and 24 (24.0%) patients, respectively. Out of a total of 120 patients, 101 patients with a median follow-up of 22.3 months (range: 4.5-62.2) were eligible for analysis; 85 experienced muscle loss and muscle loss >10% increased during cabozantinib exposition, especially after 6 months of treatment. At cabozantinib baseline, 71 patients (70.3%) had sarcopenia, and 16/30 (53.3%) non-sarcopenic patients developed sarcopenia during treatment. Baseline sarcopenia was associated with lower response rates (P = 0.031) and higher grades 3-4 toxicities (P = 0.001). Out of 92 patients included in the WL analysis, 44 (47.8%) and 12 (13.0%) experienced grades 2 and 3 WL, respectively.

CONCLUSIONS

We report a high incidence of grades 3-4 WL, fourth times higher than reported in prior pivotal trials, and half of the patients developed sarcopenia while on cabozantinib treatment. Weight and muscle mass loss with cabozantinib are underreported and may require further investigations and early management.

Biomaterials-based Approaches for Cardiac Regeneration

Cardiovascular disease is a prevalent cause of mortality and morbidity, largely due to the limited ability of cardiomyocytes to proliferate. Existing therapies for cardiac regeneration include cell-based therapies and bioactive molecules. However, delivery remains one of the major challenges impeding such therapies from having significant clinical impact. Recent advancements in biomaterials-based approaches for cardiac regeneration have shown promise in improving cardiac function, promoting angiogenesis, and reducing adverse immune response in both human clinical trials and animal studies. These advances in therapeutic delivery via extracellular vesicles, cardiac patches, and hydrogels have the potential to enable clinical impact of cardiac regeneration therapies.

The limited ability of cardiomyocytes to proliferate is a major cause of mortality and morbidity in cardiovascular diseases. There exist therapies for cardiac regeneration that are cell-based as well as that involve bioactive molecules. However, delivery remains one of the major challenges impeding such therapies from having clinical impact. Recent advancements in biomaterials-based approaches for cardiac regeneration have shown promise in clinical trials and animal studies in improving cardiac function, promoting angiogenesis, and reducing adverse immune response. This review will focus on current clinical studies of three contemporary biomaterials-based approaches for cardiac regeneration (extracellular vesicles, injectable hydrogels, and cardiac patches), remaining challenges and shortcomings to be overcome, and future directions for the use of biomaterials to promote cardiac regeneration.

Nanostructured Architectures Promote the Mesenchymal-Epithelial Transition for Invasive Cells

Dynamic modulation of cellular phenotypes between the epithelial and mesenchymal states-the epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET)-plays an important role in cancer progression. Nanoscale topography of culture substrates is known to affect the migration and EMT of cancer cells. However, existing platforms heavily rely on simple geometries such as grooved lines or cylindrical post arrays, which may oversimplify the complex interaction between cells and nanotopography in vivo. Here, we use electrodeposition to construct finely controlled surfaces with biomimetic fractal nanostructures as a means of examining the roles of nanotopography during the EMT/MET process. We found that nanostructures in the size range of 100 to 500 nm significantly promote MET for invasive breast and prostate cancer cells. The "METed" cells acquired distinct expression of epithelial and mesenchymal markers, displayed perturbed morphologies, and exhibited diminished migration and invasion, even after the removal of a nanotopographical stimulus. The phosphorylation of GSK-3 was decreased, which further tuned the expression of Snail and modulated the EMT/MET process. Our findings suggest that invasive cancer cells respond to the geometries and dimensions of complex nanostructured architectures.

Functional nanoarrays for investigating stem cell fate and function

Stem cells show excellent potential in the field of tissue engineering and regenerative medicine based on their excellent capability to not only self-renew but also differentiate into a specialized cell type of interest. However, the lack of a non-destructive monitoring system makes it challenging to identify and characterize differentiated cells before their transplantation without compromising cell viability. Thus, the development of a non-destructive monitoring method for analyzing cell function is highly desired and can significantly benefit stem cell-based therapies. Recently, nanomaterial-based scaffolds (e.g., nanoarrays) have made possible considerable advances in controlling the differentiation of stem cells and characterization of the differentiation status sensitively in real time. This review provides a selective overview of the recent progress in the synthesis methods of nanoarrays and their applications in controlling stem cell fate and monitoring live cell functions electrochemically. We believe that the topics discussed in this review can provide brief and concise guidelines for the development of novel nanoarrays and promote the interest in live cell study applications. A method which can not only control but also monitor stem cell fate and function will be a promising technology that can accelerate stem cell therapies.

Injectable hydrogel systems with multiple biophysical and biochemical cues for bone regeneration

Bone regeneration is a complex process in which angiogenesis and osteogenesis are crucial. Introducing multiple angiogenic and osteogenic cues simultaneously into a single system and tuning these cues to optimize the niche remains a challenge for bone tissue engineering. Herein, based on our injectable biomimetic hydrogels composed of silk nanofibers (SNF) and hydroxyapatite nanoparticles (HA), deferoxamine (DFO) and bone morphogenetic protein-2 (BMP-2) were loaded on SNF and HA to introduce more angiogenic and osteogenic cues. The angiogenesis and osteogenesis capacity of injectable hydrogels could be regulated by tuning the delivery of DFO and BMP-2 independently, resulting in vascularization and bone regeneration in cranial defects. The angiogenesis and osteogenesis outcomes accelerated the regeneration of vascularized bones toward similar composition and structure to natural bones. Therefore, the multiple biophysical and chemical cues provided by the nanofibrous structures, organic-inorganic compositions, and chemical and biochemical angiogenic and osteogenic inducing cues suggest the potential for clinical applicability of these hydrogels in bone tissue engineering.

Engineering the vasculature for islet transplantation

The microvasculature in the pancreatic islet is highly specialized for glucose sensing and insulin secretion. Although pancreatic islet transplantation is a potentially life-changing treatment for patients with insulin-dependent diabetes, a lack of blood perfusion reduces viability and function of newly transplanted tissues. Functional vasculature around an implant is not only necessary for the supply of oxygen and nutrients but also required for rapid insulin release kinetics and removal of metabolic waste. Inadequate vascularization is particularly a challenge in islet encapsulation. Selectively permeable membranes increase the barrier to diffusion and often elicit a foreign body reaction including a fibrotic capsule that is not well vascularized. Therefore, approaches that aid in the rapid formation of a mature and robust vasculature in close proximity to the transplanted cells are crucial for successful islet transplantation or other cellular therapies. In this paper, we review various strategies to engineer vasculature for islet transplantation. We consider properties of materials (both synthetic and naturally derived), prevascularization, local release of proangiogenic factors, and co-transplantation of vascular cells that have all been harnessed to increase vasculature. We then discuss the various other challenges in engineering mature, long-term functional and clinically viable vasculature as well as some emerging technologies developed to address them. The benefits of physiological glucose control for patients and the healthcare system demand vigorous pursuit of solutions to cell transplant challenges. STATEMENT OF SIGNIFICANCE: Insulin-dependent diabetes affects more than 1.25 million people in the United States alone. Pancreatic islets secrete insulin and other endocrine hormones that control glucose to normal levels. During preparation for transplantation, the specialized islet blood vessel supply is lost. Furthermore, in the case of cell encapsulation, cells are protected within a device, further limiting delivery of nutrients and absorption of hormones. To overcome these issues, this review considers methods to rapidly vascularize sites and implants through material properties, pre-vascularization, delivery of growth factors, or co-transplantation of vessel supporting cells. Other challenges and emerging technologies are also discussed. Proper vascular growth is a significant component of successful islet transplantation, a treatment that can provide life-changing benefits to patients.

iPSCs: A powerful tool for skeletal muscle tissue engineering

Both volumetric muscle loss (VML) and muscle degenerative diseases lead to an important decrease in skeletal muscle mass, condition that nowadays lacks an optimal treatment. This issue has driven towards an increasing interest in new strategies in tissue engineering, an emerging field that can offer very promising approaches. In addition, the discovery of induced pluripotent stem cells (iPSCs) has completely revolutionized the actual view of personalized medicine, and their utilization in skeletal muscle tissue engineering could, undoubtedly, add myriad benefits. In this review, we want to provide a general vision of the basic aspects to consider when engineering skeletal muscle tissue using iPSCs. Specifically, we will focus on the three main pillars of tissue engineering: the scaffold designing, the selection of the ideal cell source and the addition of factors that can enhance the resemblance with the native tissue.

Uniaxially crumpled graphene as a platform for guided myotube formation

Graphene, owing to its inherent chemical inertness, biocompatibility, and mechanical flexibility, has great potential in guiding cell behaviors such as adhesion and differentiation. However, due to the two-dimensional (2D) nature of graphene, the microfabrication of graphene into micro/nanoscale patterns has been widely adopted for guiding cellular assembly. In this study, we report crumpled graphene, i.e., monolithically defined graphene with a nanoscale wavy surface texture, as a tissue engineering platform that can efficiently promote aligned C2C12 mouse myoblast cell differentiation. We imparted out-of-plane, nanoscale crumpled morphologies to flat graphene via compressive strain-induced deformation. When C2C12 mouse myoblast cells were seeded on the uniaxially crumpled graphene, not only were the alignment and elongation promoted at a single-cell level but also the differentiation and maturation of myotubes were enhanced compared to that on flat graphene. These results demonstrate the utility of the crumpled graphene platform for tissue engineering and regenerative medicine for skeletal muscle tissues.

The role of sphingosine-1-phosphate in skeletal muscle: Physiology, mechanisms, and clinical perspectives

Sphingolipids were discovered more than a century ago and were simply considered as a class of cell membrane lipids for a long time. However, after the discovery of several intracellular functions and their role in the control of many physiological and pathophysiological conditions, these molecules have gained much attention. For instance, the sphingosine-1-phosphate (S1P) is a circulating bioactive sphingolipid capable of triggering strong intracellular reactions through the family of S1P receptors (S1PRs) spread in several cell types and tissues. Recently, the role of S1P in the control of skeletal muscle metabolism, atrophy, regeneration, and metabolic disorders has been widely investigated. In this review, we summarized the knowledge of S1P and its effects in skeletal muscle metabolism, highlighting the role of S1P/S1PRs axis in skeletal muscle regeneration, fatigue, ceramide accumulation, and insulin resistance. Finally, we discussed the physical exercise role in S1P/S1PRs signaling in skeletal muscle cells, and how this nonpharmacological strategy may be prospective for future investigations due to its ability to increase S1P levels.

Conductive Silk-Polypyrrole Composite Scaffolds with Bioinspired Nanotopographic Cues for Cardiac Tissue Engineering

We report on the development of bioinspired cardiac scaffolds made from electroconductive acid-modified silk fibroin-poly(pyrrole) (AMSF+PPy) substrates patterned with nanoscale ridges and grooves reminiscent of native myocardial extracellular matrix (ECM) topography to enhance the structural and functional properties of cultured human pluripotent stem cells (hPSC)-derived cardiomyocytes. Nanopattern fidelity was maintained throughout the fabrication and functionalization processes, and no loss in conductive behavior occurred due to the presence of the nanotopographical features. AMSF+PPy substrates were biocompatible and stable, maintaining high cell viability over a 21-day culture period while displaying no signs of PPy delamination. The presence of anisotropic topographical cues led to increased cellular organization and sarcomere development, and electroconductive cues promoted a significant improvement in the expression and polarization of connexin 43 (Cx43), a critical regulator of cell-cell electrical coupling. The combination of biomimetic topography and electroconductivity also increased the expression of genes that encode key proteins involved in regulating the contractile and electrophysiological function of mature human cardiac tissue.

Nanotopography-responsive myotube alignment and orientation as a sensitive phenotypic biomarker for Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is a fatal genetic disorder currently having no cure. Here we report that culture substrates patterned with nanogrooves and functionalized with Matrigel (or laminin) present an engineered cell microenvironment to allow myotubes derived from non-diseased, less-affected DMD, and severely-affected DMD human induced pluripotent stem cells (hiPSCs) to exhibit prominent differences in alignment and orientation, providing a sensitive phenotypic biomarker to potentially facilitate DMD drug development and early diagnosis. We discovered that myotubes differentiated from myogenic progenitors derived from non-diseased hiPSCs align nearly perpendicular to nanogrooves, a phenomenon not reported previously. We further found that myotubes derived from hiPSCs of a dystrophin-null DMD patient orient randomly, and those from hiPSCs of a patient carrying partially functional dystrophin align approximately 14° off the alignment direction of non-diseased myotubes. Substrates engineered with micron-scale grooves and/or cell adhesion molecules only interacting with integrins all guide parallel myotube alignment to grooves and lose the ability to distinguish different cell types. Disruption of the interaction between the Dystrophin-Associated-Protein-Complex (DAPC) and laminin by heparin or anti-α-dystroglycan antibody IIH6 disenables myotubes to align perpendicular to nanogrooves, suggesting that this phenotype is controlled by the DAPC-mediated cytoskeleton-extracellular matrix linkage.

Nondestructive Real-Time Monitoring of Enhanced Stem Cell Differentiation Using a Graphene-Au Hybrid Nanoelectrode Array

Stem cells have attracted increasing research interest in the field of regenerative medicine because of their unique ability to differentiate into multiple cell lineages. However, controlling stem cell differentiation efficiently and improving the current destructive characterization methods for monitoring stem cell differentiation are the critical issues. To this end, multifunctional graphene-gold (Au) hybrid nanoelectrode arrays (NEAs) to: (i) investigate the effects of combinatorial physicochemical cues on stem cell differentiation, (ii) enhance stem cell differentiation efficiency through biophysical cues, and (iii) characterize stem cell differentiation in a nondestructive real-time manner are developed. Through the synergistic effects of physiochemical properties of graphene and biophysical cues from nanoarrays, the graphene-Au hybrid NEAs facilitate highly enhanced cell adhesion and spreading behaviors. In addition, by varying the dimensions of the graphene-Au hybrid NEAs, improved stem cell differentiation efficiency, resulting from the increased focal adhesion signal, is shown. Furthermore, graphene-Au hybrid NEAs are utilized to monitor osteogenic differentiation of stem cells electrochemically in a nondestructive real-time manner. Collectively, it is believed the unique multifunctional graphene-Au hybrid NEAs can significantly advance stem-cell-based biomedical applications.

Surface functionalization of polyurethane scaffolds mimicking the myocardial microenvironment to support cardiac primitive cells

Scaffolds populated with human cardiac progenitor cells (CPCs) represent a therapeutic opportunity for heart regeneration after myocardial infarction. In this work, square-grid scaffolds are prepared by melt-extrusion additive manufacturing from a polyurethane (PU), further subjected to plasma treatment for acrylic acid surface grafting/polymerization and finally grafted with laminin-1 (PU-LN1) or gelatin (PU-G) by carbodiimide chemistry. LN1 is a cardiac niche extracellular matrix component and plays a key role in heart formation during embryogenesis, while G is a low-cost cell-adhesion protein, here used as a control functionalizing molecule. X-ray photoelectron spectroscopy analysis shows nitrogen percentage increase after functionalization. O1s and C1s core-level spectra and static contact angle measurements show changes associated with successful functionalization. ELISA assay confirms LN1 surface grafting. PU-G and PU-LN1 scaffolds both improve CPC adhesion, but LN1 functionalization is superior in promoting proliferation, protection from apoptosis and expression of differentiation markers for cardiomyocytes, endothelial and smooth muscle cells. PU-LN1 and PU scaffolds are biodegraded into non-cytotoxic residues. Scaffolds subcutaneously implanted in mice evoke weak inflammation and integrate with the host tissue, evidencing a significant blood vessel density around the scaffolds. PU-LN1 scaffolds show their superiority in driving CPC behavior, evidencing their promising role in myocardial regenerative medicine.

Gold and gold-silver alloy nanoparticles enhance the myogenic differentiation of myoblasts through p38 MAPK signaling pathway and promote in vivo skeletal muscle regeneration

Under the severe trauma condition, the skeletal muscles regeneration process is inhibited by forming fibrous scar tissues. Understanding the interaction between bioactive nanomaterials and myoblasts perhaps has important effect on the enhanced skeletal muscle tissue regeneration. Herein, we investigate the effect of monodispersed gold and gold-silver nanoparticles (AuNPs and Au-AgNPs) on the proliferation, myogenic differentiation and associated molecular mechanism of myoblasts (C2C12), as well as the in vivo skeletal muscle tissue regeneration. Our results showed that AuNPs and Au-AgNPs could support myoblast attachment and proliferation with negligible cytotoxicity. Under various incubation conditions (normal and differentiation medium), AuNPs and Au-AuNPs significantly enhanced the myogenic differentiation of myoblasts by upregulating the expressions of myosin heavy chain (MHC) protein and myogenic genes (MyoD, MyoG and Tnnt-1). The further analysis demonstrated that AuNPs and Au-AgNPs could activate the p38α mitogen-activated protein kinase pathway (p38α MAPK) signaling pathway and enhance the myogenic differentiation. Additionally, the AuNPs and Au-AgNPs significantly promote the in vivo skeletal muscle regeneration in a tibialis anterior muscle defect model of rat. This study may provide a nanomaterials-based strategy to improve the skeletal muscle repair and regeneration.

Manipulating cell fate: dynamic control of cell behaviors on functional platforms

We review the recent advances and new horizons in the dynamic control of cell behaviors on functional platforms and their applications.