Directional migration of mesenchymal stem cells under an SDF-1α gradient on a microfluidic device

Decellularized Tissue-Induced Cellular Recruitment for Tissue Engineering and Regenerative Medicine

Biomaterials that recapitulate the native in vivo microenvironment are promising to facilitate tissue repair and regeneration when used in combination with relevant growth factors (GFs), chemokines, cytokines, and other small molecules and cell sources. However, limitations with the use of exogenous factors and ex vivo cell expansion has prompted cell-/GF-free tissue engineering strategies. Additionally, conventional chemotaxis assays for studying cell migration behavior provide limited information, lack long-term stability, and fail to recapitulate physiologically relevant conditions. In this study, articular cartilage tissue-based biomaterials were developed via a rapid tissue decellularization protocol. The decellularized tissue was further processed into a hydrogel through solubilization and self-assembly. Chemotactic activity of the tissue-derived gel was investigated using sophisticated cellular migration assays. These tissue-derived extracellular matrix (ECM) biomaterials retain biochemical cues of native tissue and stimulate the chemotactic migration of hBMSCs in 2D and 3D cell migration models using a real-time chemotaxis assay. This strategy, in a way, developed a new paradigm in tissue engineering where cartilage tissue repair and regeneration can be approached with decellularized cartilage tissue in the place of an engineered matrix. This strategy can be further expanded for other tissue-based ECMs to develop cell-/GF-free tissue engineering and regenerative medicine strategies for recruiting endogenous cell populations to facilitate tissue repair and regeneration.

Neural regeneration in the human central nervous system-from understanding the underlying mechanisms to developing treatments. Where do we stand today?

Mature neurons in the human central nervous system (CNS) fail to regenerate after injuries. This is a common denominator across different aetiologies, including multiple sclerosis, spinal cord injury and ischemic stroke. The lack of regeneration leads to permanent functional deficits with a substantial impact on patient quality of life, representing a significant socioeconomic burden worldwide. Great efforts have been made to decipher the responsible mechanisms and we now know that potent intra- and extracellular barriers prevent axonal repair. This knowledge has resulted in numerous clinical trials, aiming to promote neuroregeneration through different approaches. Here, we summarize the current understanding of the causes to the poor regeneration within the human CNS. We also review the results of the treatment attempts that have been translated into clinical trials so far.

Human Mesenchymal Stem Cells and Innovative Scaffolds for Bone Tissue Engineering Applications

Stem cell-based therapy is a significant topic in regenerative medicine, with a predominant role being played by human mesenchymal stem cells (hMSCs). The hMSCs have been shown to be suitable in regenerative medicine for the treatment of bone tissue. In the last few years, the average lifespan of our population has gradually increased. The need of biocompatible materials, which exhibit high performances, such as efficiency in bone regeneration, has been highlighted by aging. Current studies emphasize the benefit of using biomimetic biomaterials, also known as scaffolds, for bone grafts to speed up bone repair at the fracture site. For the healing of injured bone and bone regeneration, regenerative medicine techniques utilizing a combination of these biomaterials, together with cells and bioactive substances, have drawn a great interest. Cell therapy, based on the use of hMSCs, alongside materials for the healing of damaged bone, has obtained promising results. In this work, several aspects of cell biology, tissue engineering, and biomaterials applied to bone healing/regrowth will be considered. In addition, the role of hMSCs in these fields and recent progress in clinical applications are discussed. Impact Statement The restoration of large bone defects is both a challenging clinical issue and a socioeconomic problem on a global scale. Different therapeutic approaches have been proposed for human mesenchymal stem cells (hMSCs), considering their paracrine effect and potential differentiation into osteoblasts. However, different limitations are still to be overcome in using hMSCs as a therapeutic opportunity in bone fracture repair, including hMSC administration methods. To identify a suitable hMSC delivery system, new strategies have been proposed using innovative biomaterials. This review provides an update of the literature on hMSC/scaffold clinical applications for the management of bone fractures.

Microfluidic evidence of synergistic effects between mesenchymal stromal cell-derived biochemical factors and biomechanical forces to control endothelial cell function

A functional vascular system is a prerequisite for bone repair as disturbed angiogenesis often causes non-union. Paracrine factors released from human bone marrow derived mesenchymal stromal cells (BMSCs) have angiogenic effects on endothelial cells. However, whether these paracrine factors participate in blood flow dynamics within bone capillaries remains poorly understood. Here, we used two different microfluidic designs to investigate critical steps during angiogenesis and found pronounced effects of endothelial cell proliferation as well as chemotactic and mechanotactic migration induced by BMSC conditioned medium (CM). The application of BMSC-CM in dynamic cultures demonstrates that bioactive factors in combination with fluidic flow-induced biomechanical signals significantly enhanced endothelial cell migration. Transcriptional analyses of endothelial cells demonstrate the induction of a unique gene expression profile related to tricarboxylic acid cycle and energy metabolism by the combination of BMSC-CM factors and shear stress, which opens an interesting avenue to explore during fracture healing. Our results stress the importance of in vivo - like microenvironments simultaneously including biochemical, biomechanical and oxygen levels when investigating key events during vessel repair. STATEMENT OF SIGNIFICANCE: Our results demonstrate the importance of recapitulating in vivo - like microenvironments when investigating key events during vessel repair. Endothelial cells exhibit enhanced angiogenesis characteristics when simultaneous exposing them to hMSC-CM, mechanical forces and biochemical signals simultaneously. The improved angiogenesis may not only result from the direct effect of growth factors, but also by reprogramming of endothelial cell metabolism. Moreover, with this model we demonstrated a synergistic impact of mechanical forces and biochemical factors on endothelial cell behavior and the expression of genes involved in the TCA cycle and energy metabolism, which opens an interesting new avenue to stimulate angiogenesis during fracture healing.

Epigenetic Inheritance From Normal Origin Cells Can Determine the Aggressive Biology of Tumor-Initiating Cells and Tumor Heterogeneity

The acquisition of genetic- and epigenetic-abnormalities during transformation has been recognized as the two fundamental factors that lead to tumorigenesis and determine the aggressive biology of tumor cells. However, there is a regularity that tumors derived from less-differentiated normal origin cells (NOCs) usually have a higher risk of vascular involvement, lymphatic and distant metastasis, which can be observed in both lymphohematopoietic malignancies and somatic cancers. Obviously, the hypothesis of genetic- and epigenetic-abnormalities is not sufficient to explain how the linear relationship between the cellular origin and the biological behavior of tumors is formed, because the cell origin of tumor is an independent factor related to tumor biology. In a given system, tumors can originate from multiple cell types, and tumor-initiating cells (TICs) can be mapped to different differentiation hierarchies of normal stem cells, suggesting that the heterogeneity of the origin of TICs is not completely chaotic. TIC’s epigenome includes not only genetic- and epigenetic-abnormalities, but also established epigenetic status of genes inherited from NOCs. In reviewing previous studies, we found much evidence supporting that the status of many tumor-related “epigenetic abnormalities” in TICs is consistent with that of the corresponding NOC of the same differentiation hierarchy, suggesting that they may not be true epigenetic abnormalities. So, we speculate that the established statuses of genes that control NOC’s migration, adhesion and colonization capabilities, cell-cycle quiescence, expression of drug transporters, induction of mesenchymal formation, overexpression of telomerase, and preference for glycolysis can be inherited to TICs through epigenetic memory and be manifested as their aggressive biology. TICs of different origins can maintain different degrees of innate stemness from NOC, which may explain why malignancies with stem cell phenotypes are usually more aggressive.

Emerging Trends in Mesenchymal Stem Cells Applications for Cardiac Regenerative Therapy: Current Status and Advances

Irreversible myocardium infarction is one of the leading causes of cardiovascular disease (CVD) related death and its quantum is expected to grow in coming years. Pharmacological intervention has been at the forefront to ameliorate injury-related morbidity and mortality. However, its outcomes are highly skewed. As an alternative, stem cell-based tissue engineering/regenerative medicine has been explored quite extensively to regenerate the damaged myocardium. The therapeutic modality that has been most widely studied both preclinically and clinically is based on adult multipotent mesenchymal stem cells (MSC) delivered to the injured heart. However, there is debate over the mechanistic therapeutic role of MSC in generating functional beating cardiomyocytes. This review intends to emphasize the role and use of MSC in cardiac regenerative therapy (CRT). We have elucidated in detail, the various aspects related to the history and progress of MSC use in cardiac tissue engineering and its multiple strategies to drive cardiomyogenesis. We have further discussed with a focus on the various therapeutic mechanism uncovered in recent times that has a significant role in ameliorating heart-related problems. We reviewed recent and advanced technologies using MSC to develop/create tissue construct for use in cardiac regenerative therapy. Finally, we have provided the latest update on the usage of MSC in clinical trials and discussed the outcome of such studies in realizing the full potential of MSC use in clinical management of cardiac injury as a cellular therapy module.

Human Platelet Lysate-Loaded Poly(ethylene glycol) Hydrogels Induce Stem Cell Chemotaxis In Vitro

Platelet lysates (PL) contain a selection of proteins and growth factors (GFs) that are known to mediate cell activity. Many of these biomolecules have been identified as chemoattractants with the capacity to induce cell migration. In order to effectively deliver and retain these biomolecules to the site of injury, a scaffold containing PL could be an option. We use poly(ethylene glycol) (PEG) hydrogels consisting of 90 vol % PL to investigate their migratory potential on human mesenchymal stem cells (hMSCs). Cells exposed to these hydrogels were tracked, resulting in cell trajectories and detailed migratory parameters (velocity, Euclidean distance, directness, and forward migration index). Volumetric swelling ratios, hydrogel mechanical properties, and the release kinetics of proteins and GFs from hydrogels were also assessed. Furthermore, hMSC spheroids were encapsulated within the hydrogels to qualitatively assess cell invasion by means of sprouting and disintegration of the spheroid. Cell spheroids encapsulated within the PL-PEG gels exhibited initial outgrowths and eventually colonized the 3D matrix successfully. Results from this study confirmed that hMSCs exhibit directional migration toward the PL-loaded hydrogel with increased velocity and directness, compared to the controls. Overall, the incorporation of PL renders the PEG hydrogel bioactive. This study demonstrates the capacity of PL-loaded hydrogel constructs to attract stem cells for endogenous tissue engineering purposes.

Is there a place for mesenchymal stromal cell-based therapies in the therapeutic armamentarium against COVID-19?

The COVID-19 pandemic, caused by the rapid global spread of the novel coronavirus (SARS-CoV-2), has caused healthcare systems to collapse and led to hundreds of thousands of deaths. The clinical spectrum of COVID-19 is not only limited to local pneumonia but also represents multiple organ involvement, with potential for systemic complications. One year after the pandemic, pathophysiological knowledge has evolved, and many therapeutic advances have occurred, but mortality rates are still elevated in severe/critical COVID-19 cases. Mesenchymal stromal cells (MSCs) can exert immunomodulatory, antiviral, and pro-regenerative paracrine/endocrine actions and are therefore promising candidates for MSC-based therapies. In this review, we discuss the rationale for MSC-based therapies based on currently available preclinical and clinical evidence of safety, potential efficacy, and mechanisms of action. Finally, we present a critical analysis of the risks, limitations, challenges, and opportunities that place MSC-based products as a therapeutic strategy that may complement the current arsenal against COVID-19 and reduce the pandemic's unmet medical needs.

Bone marrow mononuclear cells for joint therapy: The role of macrophages in inflammation resolution and tissue repair

Osteoarthritis (OA) is the most prevalent joint disease causing major disability and medical expenditures. Synovitis is a central feature of OA and is primarily driven by macrophages. Synovial macrophages not only drive inflammation but also its resolution, through a coordinated, simultaneous expression of pro- and anti-inflammatory mechanisms that are essential to counteract damage and recover homeostasis. Current OA therapies are largely based on anti-inflammatory principles and therefore block pro-inflammatory mechanisms such as prostaglandin E₂ and Nuclear factor-kappa B signaling pathways. However, such mechanisms are also innately required for mounting a pro-resolving response, and their blockage often results in chronic low-grade inflammation. Following minor injury, macrophages shield the damaged area and drive tissue repair. If the damage is more extensive, macrophages incite inflammation recruiting more macrophages from the bone marrow to maximize tissue repair and ultimately resolve inflammation. However, sustained damage and inflammation often overwhelms pro-resolving mechanisms of synovial macrophages leading to the chronic inflammation and related tissue degeneration observed in OA. Recently, experimental and clinical studies have shown that joint injection with autologous bone marrow mononuclear cells replenishes inflamed joints with macrophage and hematopoietic progenitors, enhancing mechanisms of inflammation resolution, providing remarkable and long-lasting effects. Besides creating an ideal environment for resolution with high concentrations of interleukin-10 and anabolic growth factors, macrophage progenitors also have a direct role in tissue repair. Macrophages constitute a large part of the early granulation tissue, and further transdifferentiate from myeloid into a mesenchymal phenotype. These cells, characterized as fibrocytes, are essential for repairing osteochondral defects. Ongoing “omics” studies focused on identifying key drivers of macrophage-mediated resolution of joint inflammation and those required for efficient osteochondral repair, have the potential to uncover ways for developing engineered macrophages or off-the-shelf pro-resolving therapies that can benefit patients suffering from many types of arthropaties, not only OA.

Enhancement of Migration and Tenogenic Differentiation of Macaca Mulatta Tendon-Derived Stem Cells by Decellularized Tendon Hydrogel

Decellularized tendon hydrogel from human or porcine tendon has been manufactured and found to be capable of augmenting tendon repair in vivo. However, no studies have clarified the effect of decellularized tendon hydrogel upon stem cell behavior. In the present study, we developed a new decellularized tendon hydrogel (T-gel) from Macaca mulatta, and investigated the effect of T-gel on the proliferation, migration and tenogenic differentiation of Macaca mulatta tendon-derived stem cells (mTDSCs). The mTDSCs were first identified to have universal stem cell characteristics, including clonogenicity, expression of mesenchymal stem cell and embryonic stem cell markers, and multilineage differentiation potential. Decellularization of Macaca mulatta Achilles tendons was confirmed to be effective by histological staining and DNA quantification. The resultant T-gel exhibited highly porous structure or similar nanofibrous structure and approximately swelling ratio compared to the collagen gel (C-gel). Interestingly, stromal cell-derived factor-1 (SDF-1) and fibromodulin (Fmod) inherent in the native tendon extracellular matrix (ECM) microenvironment were retained and the values of SDF-1 and Fmod in the T-gel were significantly higher than those found in the C-gel. Compared with the C-gel, the T-gel was found to be cytocompatible with NIH-3T3 fibroblasts and displayed good histocompatibility when implanted into rat subcutaneous tissue. More importantly, it was demonstrated that the T-gel supported the proliferation of mTDSCs and significantly promoted the migration and tenogenic differentiation of mTDSCs compared to the C-gel. These findings indicated that the T-gel, with its retained nanofibrous structure and some bioactive factors of native tendon ECM microenvironment, represents a promising hydrogel for tendon regeneration.

A mitochondrial prolyl aminopeptidase PAP2 releases N-terminal proline and regulates proline homeostasis during stress response

Most mitochondrial proteins are synthesised in the cytosol and targeted into the organelle via N-terminal targeting peptides that are cleaved upon import. The free targeting peptide is subsequently processed in a stepwise manner, with single amino acids released as final products. Here, we have characterised a proline-cleaving aminopeptidase in Arabidopsis thaliana, prolyl aminopeptidase-2 (PAP2, At3g61540). Activity assays show that PAP2 has a preferred activity to hydrolyse N-terminal proline. Protein localisation studies revealed that PAP2 is exclusively targeted to mitochondria. Characterisation of pap2 mutants show defective pollen, enhanced dark-induced senescence and increased susceptibility to abiotic stresses, which are likely attributed to a reduced level of accumulated free proline. Taken together, these results demonstrate the role of PAP2 in proline cleavage from mitochondrial peptides and proline homeostasis, which is required for the development of male gametophyte, tolerance to abiotic stresses, and leaf senescence.

[In vitro study on promoting migration ability of rat adipose derived stem cells modified by stromal cell-derived factor 1α]

Objective

To explored the effect of stromal cell-derived factor 1α (SDF-1α) on promoting the migration ability of rat adipose derived stem cells (rADSCs) by constructed the rADSCs overexpression SDF-1α via adenovirus transfection.

Methods

rADSCs were isolated from adipose tissue of 6-week-old SPF Sprague Dawley rats. Morphological observation, multi-directional differentiations (osteogenic, adipogenic, and chondrogenic inductions), and flow cytometry identification were performed. Transwell cell migration experiment was used to observe and screen the optimal concentration of exogenous SDF-1α to optimize the migration ability of rADSCs; the optimal multiplicity of infection (MOI) of rADSCs was screened by observing the cell status and fluorescence expression after transfection. Then the third generation of rADSCs were divided into 4 groups: group A was pure rADSCs; group B was rADSCs co-cultured with SDF-1α at the best concentration; group C was rADSCs infected with recombinant adenovirus-mediated green fluorescent protein (Adv-GFP) with the best MOI; group D was rADSCs infected with Adv-GFP-SDF-1α overexpression adenovirus with the best MOI. Cell counting kit 8 (CCK-8) and Transwell cell migration experiment were preformed to detect and compare the effect of exogenous SDF-1α and SDF-1α overexpression on the proliferation and migration ability of rADSCs.

Results

The cell morphology, multi-directional differentiations, and flow cytometry identification showed that the cultured cells were rADSCs. After screening, the optimal stimulating concentration of exogenous SDF-1α was 12.5 nmol/L; the optimal MOI of Adv-GFP adenovirus was 200; the optimal MOI of Adv-GFP-SDF-1α overexpression adenovirus was 400. CCK-8 method and Transwell cell migration experiment showed that compared with groups A and C, groups B and D could significantly improve the proliferation and migration of rADSCs ( P<0.05); the effect of group D on enhancing the migration of rADSCs was weaker than that of group B, but the effect of promoting the proliferation of rADSCs was stronger than that of group D ( P<0.05).

Conclusion

SDF-1α overexpression modification on rADSCs can significantly promote the proliferation and migration ability, which may be a potential method to optimize the application of ADSCs in tissue regeneration and wound repair.

Mesenchymal stem cells as a multimodal treatment for nervous system diseases

Neurological disorders are a massive challenge for modern medicine. Apart from the fact that this group of diseases is the second leading cause of death worldwide, the majority of patients have no access to any possible effective and standardized treatment after being diagnosed, leaving them and their families helpless. This is the reason why such great emphasis is being placed on the development of new, more effective methods to treat neurological patients. Regenerative medicine opens new therapeutic approaches in neurology, including the use of cell-based therapies. In this review, we focus on summarizing one of the cell sources that can be applied as a multimodal treatment tool to overcome the complex issue of neurodegeneration-mesenchymal stem cells (MSCs). Apart from the highly proven safety of this approach, beneficial effects connected to this type of treatment have been observed. This review presents modes of action of MSCs, explained on the basis of data from vast in vitro and preclinical studies, and we summarize the effects of using these cells in clinical trial settings. Finally, we stress what improvements have already been made to clarify the exact mechanism of MSCs action, and we discuss potential ways to improve the introduction of MSC-based therapies in clinics. In summary, we propose that more insightful and methodical optimization, by combining careful preparation and administration, can enable use of multimodal MSCs as an effective, tailored cell therapy suited to specific neurological disorders.

Modifying MSC Phenotype to Facilitate Bone Healing: Biological Approaches

Healing of fractures and bone defects normally follows an orderly series of events including formation of a hematoma and an initial stage of inflammation, development of soft callus, formation of hard callus, and finally the stage of bone remodeling. In cases of severe musculoskeletal injury due to trauma, infection, irradiation and other adverse stimuli, deficient healing may lead to delayed or non-union; this results in a residual bone defect with instability, pain and loss of function. Modern methods of mechanical stabilization and autologous bone grafting are often successful in achieving fracture union and healing of bone defects; however, in some cases, this treatment is unsuccessful because of inadequate biological factors. Specifically, the systemic and local microenvironment may not be conducive to bone healing because of a loss of the progenitor cell population for bone and vascular lineage cells. Autologous bone grafting can provide the necessary scaffold, progenitor and differentiated lineage cells, and biological cues for bone reconstruction, however, autologous bone graft may be limited in quantity or quality. These unfavorable circumstances are magnified in systemic conditions with chronic inflammation, including obesity, diabetes, chronic renal disease, aging and others. Recently, strategies have been devised to both mitigate the necessity for, and complications from, open procedures for harvesting of autologous bone by using minimally invasive aspiration techniques and concentration of iliac crest bone cells, followed by local injection into the defect site. More elaborate strategies (not yet approved by the U.S. Food and Drug Administration-FDA) include isolation and expansion of subpopulations of the harvested cells, preconditioning of these cells or inserting specific genes to modulate or facilitate bone healing. We review the literature pertinent to the subject of modifying autologous harvested cells including MSCs to facilitate bone healing. Although many of these techniques and technologies are still in the preclinical stage and not yet approved for use in humans by the FDA, novel approaches to accelerate bone healing by modifying cells has great potential to mitigate the physical, economic and social burden of non-healing fractures and bone defects.

Magnetic targeted delivery of the SPIONs-labeled mesenchymal stem cells derived from human Wharton's jelly in Alzheimer's rat models

Alzheimer's disease (AD) as a progressive neurodegenerative disorder is one of the leading causes of death globally. Among all treatment approaches, mesenchymal stem cells (MSCs)-based therapy is a promising modality for neurological disorders including the AD. This study aimed to magnetically deliver human Wharton's jelly-derived MSCs (WJ-MSCs) toward the hippocampal area within the AD rat's brain and determine the effects of them in cognitive improvement. Rats were randomly divided into five groups as follow: vehicle-treated control, AD model (injection of 8 μg/kg of amyloid β 1-42), IV-NTC (treated with IV-injected Non-Targeted Cells), IV-TC (treated with IV-injected Targeted Cells), and ICV-NTC (treated with Intracerebroventricular-injected Non-Targeted Cells). WJ-MSCs were labeled with dextran-coated superparamagnetic iron oxide nanoparticles (dex-SPIONs, 50 μg/ml), by bio-mimicry method. SPIONs-labeled MSCs were highly prussian blue positive with an intracellular iron concentration of 2.9 ± 0.08 pg/cell, which were successfully targeted into the hippocampus of AD rats by a halbach magnet array as magnetic targeted cell delivery (MTCD) technique. Presence of SPIONs-labeled cells in hippocampal area was proved by magnetic resonance imaging (MRI) in which signal intensity was reduced by increasing the number of these cells. Behavioral examinations showed that WJ-MSCs caused memory and cognitive improvement. Also, histological assessments showed functional improvement of hippocampal cells by expression of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). Overall, this study indicates MTCD approach as an alternative in MSC-based regenerative medicine because it approximately has the same results as invasive directly ICV-injection method has.

The Secretome of Hypoxia Conditioned hMSC Loaded in a Central Depot Induces Chemotaxis and Angiogenesis in a Biomimetic Mineralized Collagen Bone Replacement Material

The development of biomaterials with intrinsic potential to stimulate endogenous tissue regeneration at the site of injury is a main demand on future implants in regenerative medicine. For critical-sized bone defects, an in situ tissue engineering concept is devised based on biomimetic mineralized collagen scaffolds. These scaffolds are functionalized with a central depot loaded with a signaling factor cocktail, obtained from secretome of hypoxia-conditioned human mesenchymal stem cells (MSC). Therefore, hypoxia-conditioned medium (HCM)-production is standardized and adapted to achieve high signaling factor-yields; a concentration protocol based on dialysis and freeze-drying is established to enable the integration of sufficient and defined amounts into the depot. In humid milieu-as after implantation-signaling factors are released by forming a chemotactic gradient, inducing a directed migration of human bone marrow stroma cells (hBMSC) into the scaffold. Angiogenic potential, determined by coculturing human umbilical vein endothelial cells (HUVEC) with osteogenically induced hBMSC shows prevascular structures, which sprout throughout the interconnected pores in a HCM-concentration-dependent manner. Retarded release by alginate-based (1 vol%) depots, significantly improves sprouting-depth and morphology of tubular structures. With the intrinsic potential to supply attracted cells with oxygen and nutrients, this bioactive material system has great potential for clinical translation.

Enhanced Migration of Bone Marrow-Derived Mesenchymal Stem Cells with Tetramethylpyrazine and Its Synergistic Effect on Angiogenesis and Neurogenesis After Cerebral Ischemia in Rats

Bone marrow-derived mesenchymal stem cells (BMSCs) hold great promise for treating ischemic stroke owing to their capacity to secrete various trophic factors with potent angiogenic and neurogenic potentials. However, the relatively poor migratory capacity of BMSCs toward infarcted regions limits effective therapies for the treatment of stroke. The combination of BMSCs and pharmacological agent can promote the migration of BMSCs toward infarcted regions and improve the therapeutic effects after stroke. In this study, we aimed to investigate whether BMSCs combined with tetramethylpyrazine (TMP) enhanced BMSC migration into the ischemic brain, which had better therapeutic effect in the treatment of stroke. In a rat stroke model, we found that combination treatment significantly upregulated ischemic brain stromal-derived factor-1 (SDF-1) and CXC chemokine receptor 4 (CXCR4) expressions, and promoted BMSCs homing toward the ischemic regions than BMSC monotherapy. Moreover, BMSCs combined with TMP synergistically increased the expression of vascular endothelial growth factor and brain-derived neurotrophic factor, promoted angiogenesis and neurogenesis, and improved functional outcome after stroke. These results suggest that combination treatment could not only enhance the migration of BMSCs into the ischemic brain but also act in a synergistic way to potentiate endogenous repair processes and functional recovery after ischemic stroke.

Traction microscopy with integrated microfluidics: responses of the multi-cellular island to gradients of HGF

Collective cellular migration plays a central role in development, regeneration, and metastasis. In these processes, mechanical interactions between cells are fundamental but measurement of these interactions is often hampered by technical limitations. To overcome some of these limitations, here we describe a system that integrates microfluidics with traction microscopy (TM). Using this system we can measure simultaneously, and in real time, migration speeds, tractions, and intercellular tension throughout an island of confluent Madin-Darby canine kidney (MDCK) cells. The cell island is exposed to hepatocyte growth factor (HGF) at a controlled gradient of concentrations; HGF is known to elicit epithelial-to-mesenchymal transition (EMT) and cell scattering. As expected, the rate of expansion of the cell island was dependent on the concentration of HGF. Higher concentrations of HGF reduced intercellular tensions, as expected during EMT. A novel finding, however, is that the effects of HGF concentration and its gradient were seen within an island. This integrated experimental system thus provides an integrated tool to better understand cellular forces during collective cellular migration under chemical gradients.

A simple layer-stacking technique to generate biomolecular and mechanical gradients in photocrosslinkable hydrogels

Physicochemical and biological gradients are desirable features for hydrogels to enhance their relevance to biological environments for three-dimensional (3D) cell culture. Therefore, simple and efficient techniques to generate chemical, physical and biological gradients within hydrogels are highly desirable. This work demonstrates a technique to generate biomolecular and mechanical gradients in photocrosslinkable hydrogels by stacking and crosslinking prehydrogel solution in a layer by layer manner. Partial crosslinking of the hydrogel allows mixing of prehydrogel solution with the previous hydrogel layer, which makes a smooth gradient profile, rather than discrete layers. This technique enables the generation of concentration gradients of bovine serum albumin in both gelatin methacryloyl (GelMA) and poly(ethylene glycol) diacrylate hydrogels, as well as mechanical gradients across a hydrogel containing varying gel concentrations. Fluorescence microscopy, mechanical testing, and scanning electron microscopy show that the gradient profiles can be controlled by changing both the volume and concentration of each layer as well as intensity of UV exposure. GelMA hydrogel gradients with different Young's moduli were successfully used to culture human fibroblasts. The fibroblasts migrated along the gradient axis and showed different morphologies. In general, the proposed technique provides a rapid and simple approach to design and fabricate 3D hydrogel gradients for in vitro biological studies and potentially for in vivo tissue engineering applications.

Engineered Mesenchymal Stem Cell/Nanomedicine Spheroid as an Active Drug Delivery Platform for Combinational Glioblastoma Therapy

Mesenchymal stem cell (MSC) has been increasingly applied to cancer therapy because of its tumor-tropic capability. However, short retention at target tissue and limited payload option hinder the progress of MSC-based cancer therapy. Herein, we proposed a hybrid spheroid/nanomedicine system, comprising MSC spheroid entrapping drug-loaded nanocomposite, to address these limitations. Spheroid formulation enhanced MSC's tumor tropism and facilitated loading of different types of therapeutic payloads. This system acted as an active drug delivery platform seeking and specifically targeting glioblastoma cells. It enabled effective delivery of combinational protein and chemotherapeutic drugs by engineered MSC and nanocomposite, respectively. In an in vivo migration model, the hybrid spheroid showed higher nanocomposite retention in the tumor tissue compared with the single MSC approach, leading to enhanced tumor inhibition in a heterotopic glioblastoma murine model. Taken together, this system integrates the merits of cell- and nanoparticle- mediated drug delivery with the tumor-homing characteristics of MSC to advance targeted combinational cancer therapy.

Podoplanin regulates the migration of mesenchymal stromal cells and their interaction with platelets

Mesenchymal stromal cells (MSCs) upregulate podoplanin at sites of infection, chronic inflammation and cancer. Here, we investigated the functional consequences of podoplanin expression on the migratory potential of MSCs and their interactions with circulating platelets. Expression of podoplanin significantly enhanced the migration of MSCs compared to MSCs lacking podoplanin. Rac-1 inhibition altered the membrane localisation of podoplanin and in turn significantly reduced MSC migration. Blocking Rac-1 activity had no effect on the migration of MSCs lacking podoplanin, indicating that it was responsible for regulation of migration through podoplanin. When podoplanin-expressing MSCs were seeded on the basal surface of a porous filter, they were able to capture platelets perfused over the uncoated apical surface and induce platelet aggregation. Similar microthrombi were observed when endothelial cells (ECs) were co-cultured on the apical surface. Confocal imaging shows podoplanin-expressing MSCs extending processes into the EC layer, and these processes could interact with circulating platelets. In both models, platelet aggregation induced by podoplanin-expressing MSCs was inhibited by treatment with recombinant soluble C-type lectin-like receptor 2 (CLEC-2; encoded by the gene Clec1b). Thus, podoplanin may enhance the migratory capacity of tissue-resident MSCs and enable novel interactions with cells expressing CLEC-2.

Summary: Podoplanin enhances the migration of mesenchymal stromal cells in a Rac-1-dependent manner, enabling direct interactions of subendothelial stroma with circulating platelets.

Migration of mesenchymal stem cells tethered with carbon nanotubes under a chemotactic gradient

Carbon nanotubes (CNTs) have been extensively studied for photothermal ablation of malignant cells due to their ability to absorb near-infrared (NIR) laser light and convert it to thermal energy for the lysis of tumor cells. Functionalizing CNTs with tumor-targeting moieties can facilitate the delivery to tumor sites. Instead of using targeting moieties, mesenchymal stem cells (MSCs) have been considered as vehicles to deliver therapeutic agents to cancer cells. In this study, the effects of attaching CNTs to MSCs on cell migration in response to a chemotactic gradient were investigated. Multiwalled carbon nanotubes (MWCNTs) were functionalized with streptavidin–fluorescein isothiocyanate (SA–FITC). The surface of human MSCs was biotinylated by culturing MSCs with biotin–lipid containing medium. CNTs were then attached on the outer cell membrane of biotinylated MSCs through SA–biotin binding. Fluorescence microscopy confirmed CNTs were located on the surface of MSCs. Various amounts of CNTs anchored on the membrane of MSCs were used to examine the effects of CNTs on MSC proliferation and migration. Our transwell migration assay showed that 4.26 ng CNT per cell is the threshold value that would not affect the migration speed of CNT-tagged MSCs toward the established gradient of chemoattractant SDF-1α.

Chemotactic migration of biotinylated mesenchymal stem cells tethered with streptavidin-functionalized carbon nanotubes.

Distinct Dynamics of Stem and Progenitor Cells in Blood of Polytraumatized Patients

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Endogenously mobilized stem and progenitor cells (SPCs) or exogenously provided SPCs are thought to be beneficial for trauma therapy. However, still little is known about the synchronized dynamics of the number of SPCs in blood after severe injury and parameters like cytokine profiles that correlate with these numbers. We determined the number of hematopoietic stem cells, common myeloid progenitors, granulocyte-macrophage progenitors, and mesenchymal stem/stromal cells in peripheral blood (PB) 0 to 3, 8, 24, 48, and 120 h after polytrauma in individual patients (injury severity score ≥ 21). We found that the number of blood SPCs follows on average a synchronous, inverse bell-shaped distribution, with an increase at 0 to 3 h, followed by a strong decrease, with a nadir in SPC numbers in blood at 24 or 48 h. The change in numbers of SPCs in PB between 48 h and 120 h revealed two distinct patterns: Pattern 1 is characterized by an increase in the number of SPCs to a level higher than normal, pattern 2 is characterized by an almost absent increase in the number of SPCs compared to the nadir. Changes in the concentrations of the cytokines CK, MDC, IL-8, G-CSF Gro-α, VEGF, and MCP-1 correlated with changes in the number of SPCs in PB or were closely associated with Pattern 1 or Pattern 2. Our data provide novel rationale for investigations on the role of stem cell mobilization in polytraumatized patients and its likely positive impact on trauma outcome.

Quantification of focal adhesion dynamics of cell movement based on cell-induced collagen matrix deformation using second-harmonic generation microscopy

Mechanical interactions of living cells with the surrounding environment via focal adhesion (FA) in three dimensions (3-D) play a key role in dynamic biological events, such as tissue regeneration, wound healing, and cancer invasion. Recently, several methods for observing 3-D cell-extracellular matrix (ECM) interactions have been reported, lacking solid and quantitative analysis on the dynamics of the physical interaction between the cell and the ECM. We measured the submicron displacements of ECM deformation in 3-D due to protrusion-retraction dynamics during cell migration, using second-harmonic generation without labeling the matrix structures. We then quantitatively analyzed the mechanical deformation between the ECM and the cells based on spatiotemporal volumetric correlations. The greatest deformations within the collagen matrix were found to occur at sites of colocalization of the FA site-related proteins vinculin and actin, which confirms that FA sites play a critical role in living cells within the ECM as a point for adhesion, traction, and migration. We believe that this modality can be used in studies of cell-ECM interaction during angiogenesis, wound healing, and metastasis.

Modulation of microenvironment for controlling the fate of periodontal ligament cells: the role of Rho/ROCK signaling and cytoskeletal dynamics

Cells behave in a variety of ways when they perceive changes in their microenvironment; the behavior of cells is guided by their coordinated interactions with growth factors, niche cells, and extracellular matrix (ECM). Modulation of the microenvironment affects the cell morphology and multiple gene expressions. Rho/Rho-associated coiled-coil-containing protein kinase (ROCK) signaling is one of the key regulators of cytoskeletal dynamics and actively and/or passively determines the cell fate, such as proliferation, migration, differentiation, and apoptosis, by reciprocal communication with the microenvironment. During periodontal wound healing, it is important to recruit the residential stem cells into the defect site for regeneration and homeostasis of the periodontal tissue. Periodontal ligament (PDL) cells contain a heterogeneous fibroblast population, including mesenchymal stem cells, and contribute to the reconstruction of tooth-supporting tissues. Therefore, bio-regeneration of PDL cells has been the ultimate goal of periodontal therapy for decades. Recent stem cell researches have shed light on intrinsic ECM properties, providing paradigm shifts in cell fate determination. This review focuses on the role of ROCK activity and the effects of Y-27632, a specific inhibitor of ROCK, in the modulation of ECM-microenvironment. Further, it presents the current understanding of how Rho/ROCK signaling affects the fate determination of stem cells, especially PDL cells. In addition, we have also discussed in detail the underlying mechanisms behind the reciprocal response to the microenvironment.

Stem Cells from Human Extracted Deciduous Teeth Expanded in Foetal Bovine and Human Sera Express Different Paracrine Factors After Exposure to Freshly Prepared Human Serum

BACKGROUND

The response of stem cells to paracrine factors within the host's body plays an important role in the regeneration process after transplantation. The aim of this study was to determine the viability and paracrine factor profile of stem cells from human extracted deciduous teeth (SHED) pre-cultivated in media supplemented with either foetal bovine serum (FBS) or pooled human serum (pHS) in the presence of individual human sera (iHS).

METHODS

SHED (n = 3) from passage 4 were expanded in FBS (FBS-SHED) or pHS (pHS-SHED) supplemented media until passage 7. During expansion, the proliferation of SHED was determined. Cells at passage 7 were further expanded in human serum from four individual donors (iHS) for 120 h followed by assessment of cell viability and profiling of the secreted paracrine factors.

RESULTS

Proliferation of SHED was significantly higher (p < 0.05) in pHS supplemented media compared to FBS supplemented media. pHS-SHED also maintained their higher proliferation rate compared to FBS-SHED in the presence of iHS. In iHS supplemented media, FBS-SHED expressed significantly higher levels of SDF-1A (p < 0.05) after 24 h compared to pHS-SHED. Similar results were found for HGF (p < 0.01), LIF (p < 0.05), PDGF-BB (p < 0.05), SDF-1A (p < 0.01), and IL-10 (p < 0.05) when cell culture supernatants from FBS-SHED were profiled 120 h post-incubation.

CONCLUSION

SHED expanded in pHS instead of FBS have higher proliferative capacity and show an altered secretion profile. Further studies are needed to determine whether these differences could result in better engraftment and regeneration following transplantation.

Critical role of SDF-1/CXCR4 signaling pathway in stem cell homing in the deafened rat cochlea after acoustic trauma

Previous animal studies have shown that stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor-4 (CXCR4) signaling pathway plays an important role in the targeted migration of bone marrow-derived mesenchymal stem cells (BMSCs) to the injured area. In the present study, we aimed to investigate the potential role of chemotactic SDF-1/CXCR4 signaling pathway in the homing of transplanted BMSCs to the injured cochlea after noise-induced hearing loss (NIHL) in a rat model. White noise exposure (110 dB) paradigm was used for hearing loss induction in male rats for 6 hours in 5 days. Distortion-product otoacoustic emission (DPOAE) responses were recorded before the experiment and post noise exposure. Hoechst 33342-labeled BMSCs and CXCR4 antagonist (AMD3100)-treated BMSCs were injected into the rat cochlea through the round window. SDF-1 protein expression in the cochlear tissue was assayed using western blot assay. The number of labeled BMSCs reaching the endolymph was determined after 24 hours. SDF-1 was significantly increased in the cochlear tissue of rats in the noise exposure group than in the control group. The number of Hoechst 33342-labeled BMSCs reaching the endolymph of the cochlea was significantly smaller in the AMD3100-treated BMSCs group than in the normal BMSCs group. Our present findings suggest that the SDF-1/CXCR4 signaling pathway has a critical role in BMSCs migration to the injured cochlea in a rat model of noise-induced hearing loss.