Lentiviral CRISPR/Cas9-Mediated Genome Editing for the Study of Hematopoietic Cells in Disease Models

Manipulating genes in hematopoietic stem cells using conventional transgenesis approaches can be time-consuming, expensive, and challenging. Benefiting from advances in genome editing technology and lentivirus-mediated transgene delivery systems, an efficient and economical method is described here that establishes mice in which genes are manipulated specifically in hematopoietic stem cells. Lentiviruses are used to transduce Cas9-expressing lineage-negative bone marrow cells with a guide RNA (gRNA) targeting specific genes and a red fluorescence reporter gene (RFP), then these cells are transplanted into lethally-irradiated C57BL/6 mice. Mice transplanted with lentivirus expressing non-targeting gRNA are used as controls. Engraftment of transduced hematopoietic stem cells are evaluated by flow cytometric analysis of RFP-positive leukocytes of peripheral blood. Using this method, ~90% transduction of myeloid cells and ~70% of lymphoid cells at 4 weeks after transplantation can be achieved. Genomic DNA is isolated from RFP-positive blood cells, and portions of the targeted site DNA are amplified by PCR to validate the genome editing. This protocol provides a high-throughput evaluation of hematopoiesis-regulatory genes and can be extended to a variety of mouse disease models with hematopoietic cell involvement.

Dynamic Continuum of Molecular Assemblies for Controlling Cell Fates

Biological systems have evolved to create a structural and dynamic continuum of bio-macromolecular assemblies for the purpose of optimizing the system's functions. The formation of these dynamic higher-order assemblies is precisely controlled by biological cues. However, controlling the self-assembly of synthetic molecules spatiotemporally in or on live cells is still a big challenge, especially for performing functions. This concept article introduces the use of in situ reactions as a spatiotemporal control to form assemblies of small molecules that induce cell morphogenesis or apoptosis. After briefly introducing a representative example of a natural dynamic continuum of the higher-order assemblies, we describe enzyme-instructed self-assembly (EISA) for constructing dynamic assemblies of small molecules, then discuss the use of EISA for controlling cell morphogenesis and apoptosis. Finally, we provide a brief outlook to discuss the future perspective of this exciting new research direction.

Soluble Signals and Remodeling in a Synthetic Gelatin-Based Hematopoietic Stem Cell Niche

Hematopoietic stem cells (HSCs) reside in the bone marrow within niches that provide microenvironmental signals in the form of biophysical cues, bound and diffusible biomolecules, and heterotypic cell-cell interactions that influence HSC fate decisions. This study seeks to inform the development of a synthetic culture platform that promotes ex vivo HSC expansion without exhaustion. A library of methacrylamide-functionalized gelatin (GelMA) hydrogels is used to explore remodeling and crosstalk from mesenchymal stromal cells (MSCs) on the expansion and quiescence of murine HSCs. The use of a degradable GelMA hydrogel enables MSC-mediated remodeling, yielding dynamic shifts in the matrix environment over time. An initially low-diffusivity hydrogel for co-culture of hematopoietic stem and progenitor cells to MSCs facilitates maintenance of an early progenitor cell population over 7 days. Excitingly, this platform promotes retention of a quiescent HSC population compared to HSC monocultures. These studies reveal MSC-density-dependent upregulation of MMP-9 and changes in hydrogel mechanical properties (ΔE = 2.61 ± 0.72) suggesting MSC-mediated matrix remodeling may contribute to a dynamic culture environment. Herein, a 3D hydrogel is reported for ex vivo HSC culture, in which HSC expansion and quiescence is sensitive to hydrogel properties, MSC co-culture, and MSC-mediated hydrogel remodeling.

Long non-coding RNA GAS5 promotes osteogenic differentiation of bone marrow mesenchymal stem cells by regulating the miR-135a-5p/FOXO1 pathway

Studies have shown that promoting the differentiation of bone marrow mesenchymal stem cells (BMSCs) into osteoblasts could protect against osteoporosis. Increasing evidence demonstrates that long non-coding RNAs (lncRNAs) participate in BMSC osteogenic differentiation. This study aimed to investigate the role and underlying mechanism of growth arrest-specific transcript 5 (GAS5) in osteogenic differentiation. The mechanism was mainly focused on miR-135a-5p/FOXO1 pathway by gain- and loss-of function tests. GAS5 and FOXO1 expression was decreased, whereas miR-135a-5p expression was increased, in the BMSCs from osteoporotic mice. Levels of GAS5 and FOXO1 were increased and miR-135a-5p expression was decreased during osteogenic differentiation of BMSCs. Overexpression of GAS5 promoted, whereas knockdown of GAS5 suppressed, BMSC osteogenic differentiation. As for the mechanism, GAS5 functioned as a competing endogenous RNA for miR-135a-5p to regulate FOXO1 expression. In conclusion, GAS5 promoted osteogenesis of BMSCs by regulating the miR-135a-5p/FOXO1 axis. This finding suggests that targeting GAS5 may be a useful therapy for treating postmenopausal osteoporosis.

The effect of biomimetic calcium deficient hydroxyapatite and sintered β-tricalcium phosphate on osteoimmune reaction and osteogenesis

Biomaterial implantation triggers inflammatory reactions. Understanding the effect of physicochemical features of biomaterials on the release of inflammatory cytokines from immune cells would be of great interest in view of designing bone graft materials to enhance the healing of bone defects. The present work investigated the interactions of two chemically and texturally different calcium phosphate (CaPs) substrates with macrophages, one of the main innate immune cells, and its further impact on osteogenic differentiation of bone forming cells. The behaviour of macrophages seeded on biomimetic calcium deficient hydroxyapatite (CDHA) and sintered β-tricalcium phosphate (β-TCP) was assessed in terms of the release of inflammatory cytokines and osteoclastogenic factors. The osteogenic differentiation of bone progenitor cells (bone marrow stromal cells (BMSCs) and osteoblastic cell line (SaOS-2)) were subsequently studied by incubating with the conditioned medium induced by macrophage-CaPs interaction in order to reveal the effect of immune cell reaction to CaPs on osteogenic differentiation. It was found that the incubation of macrophages with CaPs substrates caused a decrease of pro-inflammatory cytokines, more pronounced for β-TCP compared with CDHA showing significantly decreased IL-6, TNF-a, and iNOS. However, the macrophage-CDHA interaction resulted in a more favourable environment for osteogenic differentiation of osteoblasts with more collagen type I production and osteogenic genes (Runx2, BSP) expression, suggesting that osteogenic differentiation of bone cells is not only determined by the nature of biomaterials, but also significantly influenced by the inflammatory environment generated by the interaction of immune cells and biomaterials. STATEMENT OF SIGNIFICANCE: The field of osteoimmunology highlights the importance of the cross-talk between immune and bone cells for effective bone regeneration. This tight interaction opens the door to new strategies that encompass the development of smart cell-instructive biomaterials which performance covers the events from early inflammation to osteogenesis. The present work links the anti-inflammatory and osteoimmunomodulatory features of synthetic bone grafts to their chemistry and texture, focussing on the cross-talk between macrophages and two major orchestrators of bone healing, namely primary mesenchymal stem cells and osteoblasts. The results emphasize the importance of the microenvironment created through the interaction between the substrate and the immune cells as it can stimulate osteogenic events and subsequently foster bone healing.

Biological functions of mesenchymal stem cells and clinical implications

Mesenchymal stem cells (MSCs) are isolated from multiple biological tissues-adult bone marrow and adipose tissues and neonatal tissues such as umbilical cord and placenta. In vitro, MSCs show biological features of extensive proliferation ability and multipotency. Moreover, MSCs have trophic, homing/migration and immunosuppression functions that have been demonstrated both in vitro and in vivo. A number of clinical trials are using MSCs for therapeutic interventions in severe degenerative and/or inflammatory diseases, including Crohn's disease and graft-versus-host disease, alone or in combination with other drugs. MSCs are promising for therapeutic applications given the ease in obtaining them, their genetic stability, their poor immunogenicity and their curative properties for tissue repair and immunomodulation. The success of MSC therapy in degenerative and/or inflammatory diseases might depend on the robustness of the biological functions of MSCs, which should be linked to their therapeutic potency. Here, we outline the fundamental and advanced concepts of MSC biological features and underline the biological functions of MSCs in their basic and translational aspects in therapy for degenerative and/or inflammatory diseases.

Canine Bone Marrow-derived Mesenchymal Stem Cells: Genomics, Proteomics and Functional Analyses of Paracrine Factors

Adult stem cells have become prominent candidates for treating various diseases in veterinary practice. The main goal of our study was therefore to provide a comprehensive study of canine bone marrow-derived mesenchymal stem cells (BMMSC) and conditioned media, isolated from healthy adult dogs of different breeds. Under well-defined standardized isolation protocols, the multipotent differentiation and specific surface markers of BMMSC were supplemented with their gene expression, proteomic profile, and their biological function. The presented data confirm that canine BMMSC express important genes for differentiation toward osteo-, chondro-, and tendo-genic directions, but also genes associated with angiogenic, neurotrophic, and immunomodulatory properties. Furthermore, using proteome profiling, we identify for the first time the dynamic release of various bioactive molecules, such as transcription and translation factors and osteogenic, growth, angiogenic, and neurotrophic factors from canine BMMSC conditioned medium. Importantly, the relevant genes were linked to their proteins as detected in the conditioned medium and further associated with angiogenic activity in chorioallantoic membrane (CAM) assay. In this way, we show that the canine BMMSC release a variety of bioactive molecules, revealing a strong paracrine component that may possess therapeutic potential in various pathologies. However, extensive experimental or preclinical trials testing canine sources need to be performed in order to better understand their paracrine action, which may lead to novel therapeutic strategies in veterinary medicine.

Mesenchymal stem cells isolated from both distal femurs of patients with unilateral trauma or osteoarthritis of the knee exhibit similar in-vitro ability of bone formation

BACKGROUND

Bone fractures are a common cause of hospital admission. Currently, treatment consists of conservative regimens or operation. However, regenerative medicine introduces a possible new addition to established treatments. Evidence suggests that application of autologous mesenchymal stem cells can enhance bone regeneration, by differentiating into osteoblasts. This study investigates whether mesenchymal stem cells, isolated from bone marrow in sites of trauma or osteoarthritis, exhibit reduced proliferation and osteogenic differentiation in-vitro, compared to stem cells isolated from non-traumatic and non-osteoarthritic sites. If these pathologies are detrimental to the quality, clinicians should prioritize bone marrow from unafflicted sites.

METHODS

17 patients were enrolled. 7 had recent unilateral trauma to the knee, requiring arthroscopy. 10 had x-ray verified unilateral osteoarthritis of the knee and were scheduled for arthroplasty. Stem cells were isolated from bone marrow aspirated perioperatively from both distal femurs. In-vitro osteogenic activity was assessed through alkaline phosphatase measurement, RNA-expression and alizarin red staining. Proliferation was measured using a growth curve.

RESULTS

29 out of 34 primary cultures were successful, forming colonies with characteristic stem cell-morphology. There was no difference in mononuclear cell yield of aspirates or stem cell-yield from primary culture between non-osteoarthritic and arthritic knees or non-traumatic and traumatic knees. There was no significant difference in in-vitro osteogenic capability or proliferation.

CONCLUSION

Our findings suggest that stem cells from sites afflicted by osteoarthritis or trauma can be utilized for bone regeneration with identical results as MSCs isolated from non-traumatic and non-osteoarthritic sites. However, clinical studies are needed to confirm this assumption.

Properties of an alginate-gelatin-based bioink and its potential impact on cell migration, proliferation, and differentiation

Three-dimensional (3D) bioprinting allows embedding of cells within a bioink, creating cell-based 3D structures to promote tissue regeneration and repair. The bioink should be biocompatible with the cells and its effect on cell behavior should be determined. Alginate-gelatin (Alg-Gel) blends with mouse planta dermis (PD) induced epidermal progenitors for sweat gland regeneration, confirming the role of 3D support during the process. The present study aimed to investigate the chemical and physical properties of the Alg-Gel-PD bioink, and its effect on embedded mouse mesenchymal stem cells (MSCs). MSCs showed increased proliferation and migration in 2D culture with an Alg-Gel-based bioink extract. Gene expression analysis confirmed MSC differentiation towards sweat gland cells. The extract had no effect on protein expression in differentiated cells. Mixing MSCs with the Alg-Gel-based bioink for 3D bioprinting resulted in gene and protein expression characteristic of differentiation, including YAP1 activation. The mechanical strength of the bioink was similar to that of mouse dermal tissue and scanning electron microscopy showed that PD induced a more regular pore structure, suggesting advantages for the physical properties of the embedded cells. This study determined the influence of bioink on cellular behavior, thereby promoting therapeutic stem cell function via 3D cell printing processes.

The synergistic effect of electroacupuncture and bone mesenchymal stem cell transplantation on repairing thin endometrial injury in rats

BACKGROUND

Tissue regeneration disorder after endometrial injury is an important cause of intrauterine adhesions, amenorrhea, and infertility in women. Both bone marrow mesenchymal stem cell (BMSC) transplantation and electroacupuncture (EA) are promising therapeutic applications for endometrial injury. This study examined their combined effects on thin endometrium in rats and the possible mechanisms underlying these effects.

METHODS

A thin endometrial model was established in Sprague-Dawley (SD) rats by perfusing 95% ethanol into the right side of the uterus. The wounds were randomly treated with PBS (model group), BMSCs only (BMSC group), EA only (EA group), and BMSCs combined with EA (BMSC + EA group). Endometrial morphological alterations were observed by hematoxylin and eosin (H&E) staining. Changes in markers of epithelial and stromal endometrium cells, endometrial receptivity-related chemokines, and paracrine factors were detected using immunohistochemistry, western blotting, and quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Finally, the functional recovery of the uterus was evaluated by determining the rate of embryo implantation.

RESULTS

As shown by endometrial morphology, the damaged uteri in all the treatment groups recovered to some extent, with the best effects observed in the BMSC + EA group. Further studies showed that EA promoted the migration of transplanted BMSCs to damaged uteri by activating the stromal cell-derived factor-1/C-X-C chemokine receptor type 4 (SDF-1/CXCR4) axis. As compared with the other groups, upregulated expression of endometrial cytokeratin and vimentin, increased secretion of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in endometrial lesions, and improved embryo implantation rates on the 8th day of pregnancy were found in the BMSC + EA group.

CONCLUSIONS

EA plays an important role in supporting BMSCs in the repair of thin endometrium, most likely by promoting the migration of BMSCs and enhancing the paracrine effect of BMSCs.

Reparative macrophage transplantation for myocardial repair: a refinement of bone marrow mononuclear cell-based therapy

Reparative macrophages play an important role in cardiac repair post-myocardial infarction (MI). Bone marrow mononuclear cells (BM-MNCs) have been investigated as a donor for cell therapy but with limited clinical success. These cells, however, may be utilized as a source for reparative macrophages. This translational study aimed to establish a robust in vitro protocol to produce functional reparative macrophages from BM-MNCs and to establish pre-clinical evidence of the efficacy of reparative macrophage transplantation for the treatment of MI. Mouse BM-MNCs were treated with M-CSF plus IL-4, IL-10, TGF-β1 or combinations of these in vitro. The concomitant administration of M-CSF and IL-4 produced the highest rate and largest number of CD11b+F4/80+CD206+ reparative macrophages. Expression and secretion of tissue repair-related factors including IGF-1, TGF-β1, VEGF and IL1-ra were remarkably enhanced in reparative macrophages compared to BM-MNCs. These cells were transplanted in a mouse MI model, resulting in evident improvement in cardiac function recovery, compared to BM-MNC transplantation. Histological studies showed that reparative macrophage transplantation enhanced myocardial tissue repair including augmented microvascular formation, reduced cardiomyocyte hypertrophy and attenuated interstitial fibrosis. Moreover, survival of reparative macrophages in the heart post-transplantation was increased compared to BM-MNCs. Reparative macrophage transplantation also increased host-derived reparative macrophages in part through TGF-β secretion. In conclusion, concomitant M-CSF + IL-4 treatment effectively produced reparative macrophages from BM-MNCs in vitro. Transplantation of produced reparative macrophage achieved a superior therapeutic efficacy, compared to BM-MNC transplantation, through the enhanced quantity and quality of donor cell engraftment. Further development of this advanced cell-based therapy is warranted.

Ablation of Stabilin-1 Enhances Bone-Resorbing Activity in Osteoclasts In Vitro

Stabilin-1 is a transmembrane receptor that regulates molecule recycling and cell homeostasis by controlling the intracellular trafficking and participates in cell-cell adhesion and transmigration. Stabilin-1 expression is observed in various organs, including bones; however, its function and regulatory mechanisms in the bone remain unclear. In this study, we evaluated the physiological function of stabilin-1 in bone cells and tissue using a stabilin-1 knockout (Stab1 KO) mouse model. In wild-type (WT) mice, stabilin-1 was expressed in osteoblasts and osteoclasts, and its expression was maintained during osteoblast differentiation but significantly decreased after osteoclast differentiation. There was no difference in osteoblast differentiation and function, or the expression of osteoblast differentiation markers between mesenchymal stem cells isolated from Stab1 KO and WT mice. However, osteoclast differentiation marker levels demonstrated a non-significant increase and bone-resorbing activity was significantly increased in vitro in RANKL-induced osteoclasts from Stab1-deficient bone marrow macrophages (BMMs) compared with those of WT BMMs. Microcomputed tomography showed a negligible difference between WT and Stab1 KO mice in bone volume and trabecular thickness and number. Moreover, no in vivo functional defect in bone formation by osteoblasts was observed in the Stab1 KO mice. The osteoclast surface and number showed an increased tendency in Stab1 KO mice compared to WT mice in vivo, but this difference was not statistically significant. Overall, these results indicate that Stab1 does not play an essential role in in vivo bone development and bone cell function, but it does affect in vitro osteoclast maturation and function for bone resorption.

Supercritical CO2 foamed composite scaffolds incorporating bioactive lipids promote vascularized bone regeneration via Hif-1α upregulation and enhanced type H vessel formation

Bone tissue engineering has substantial potential for the treatment of massive bone defects; however, efficient vascularization coupled with bone regeneration still remains a challenge in this field. In the current study, supercritical carbon dioxide (scCO₂) foaming technique was adopted to fabricate mesoporous bioactive glasses (MBGs) particle-poly (lactic-co-glycolic acid) (PLGA) composite scaffolds with appropriate mechanical and degradation properties as well as in vitro bioactivity. The MBG-PLGA scaffolds incorporating the bioactive lipid FTY720 (designated as FTY/MBG-PLGA) exhibited simultaneously sustained release of the bioactive lipid and ions. In addition to providing a favorable microenvironment for cellular adhesion and proliferation, FTY/MBG-PLGA scaffolds significantly facilitated the in vitro osteogenic differentiation of rBMSCs and also markedly stimulated the upregulation of Hif-1α expression via the activation of the Erk1/2 pathway, which mediated the osteogenic and pro-angiogenic effects on rBMSCs. Furthermore, FTY/MBG-PLGA extracts induced superior in vitro angiogenic performance of HUVECs. In vivo evaluation of critical-sized rat calvarial bone defects indicated that FTY/MBG-PLGA scaffolds potently promoted vascularized bone regeneration. Notably, the significantly enhanced formation of type H vessels (CD31^hiEmcn^hi neo-vessels) was observed in newly formed bone tissue in FTY/MBG-PLGA group, strongly suggesting that FTY720 and therapeutic ions released from the scaffolds synergistically induced more type H vessel formation, which indicated the coupling of angiogenesis and osteogenesis to achieve efficiently vascularized bone regeneration. Overall, the results indicated that the foamed porous MBG-PLGA scaffolds incorporating bioactive lipids achieved desirable vascularization-coupled bone formation and could be a promising strategy for bone regenerative medicine. STATEMENT OF SIGNIFICANCE: Efficacious coupling of vascularizationandbone formation is critical for the restoration of large bone defects. Anoveltechnique was used to fabricate composite scaffolds incorporating bioactive lipids which possessedsynergistic cues of bioactive lipids and therapeutic ions to potently promotebone regenerationas well as vascularization. The underlying molecular mechanism for the osteogenic and pro-angiogenic effects of the compositescaffolds was unveiled. Interestingly, the scaffolds were furtherfoundto enhance the formation oftype H capillarieswithin the bone healing microenvironment to couple angiogenesis to osteogenesis to achieve satisfyingvascularizedbone regeneration.These findings provide a novel strategy to develop efficiently vascularized engineering constructs to treat massive bone defects.

Short-chain fatty acids and FFAR2 as suppressors of bone resorption

Short-chain fatty acids (SCFAs) exert a variety of immune and metabolic functions by binding to G-protein-coupled receptors, mainly free fatty acid receptor 2 (FFAR2). However, the effects of SCFAs and FFARs on bone remodeling, especially in alveolar bone, have been less explored. In this study, we investigated the influence of the SCFA/FFAR2 axis on alveolar bone. Bone samples from wild-type (WT) and FFAR2-deficient mice (FFAR2-/-) were analyzed using micro-CT, histology and qPCR. WT and FFAR2-/- animals received a high-fiber diet (HFD) reported to increase circulating levels of SCFAs. Additionally, we analyzed the effects of SCFAs and a synthetic FFAR2 agonist, phenylacetamide-1 (CTMB), on bone cell differentiation. The participation of histone deacetylase inhibitors (iHDACs) in the effects of SCFAs was further assessed in vitro. CTMB treatment was also evaluated in vivo during orthodontic tooth movement (OTM). FFAR2-/- mice exhibited deterioration of maxillary bone parameters. Consistent with this, FFAR2-/- mice exhibited a significant increase of OTM and changes in bone cell numbers and in the expression of remodeling markers. The HFD partially reversed bone loss in the maxillae of FFAR2-/- mice. In WT mice, the HFD induced changes in the bone markers apparently favoring a bone formation scenario. In vitro, bone marrow cells from FFAR2-/- mice exhibited increased differentiation into osteoclasts, while no changes in osteoblasts were observed. In line with this, differentiation of osteoclasts was diminished by SCFAs and CTMB. Moreover, CTMB treatment significantly reduced OTM. Pretreatment of osteoclasts with iHDACs did not modify the effects of SCFAs on these cells. In conclusion, SCFAs function as regulators of bone resorption. The effects of SCFAs on osteoclasts are dependent on FFAR2 activation and are independent of the inhibition of HDACs. FFAR2 agonists may be useful to control bone osteolysis.

Downregulation of microRNA-214 improves therapeutic potential of allogeneic bone marrow-derived mesenchymal stem cell by targeting PIM-1 in rats with acute liver failure

Acute liver failure (ALF) is a disease resulted from diverse etiology, which generally leads to a rapid degenerated hepatic function. However, transplantation bone marrow-derived mesenchymal stem cells (BMSCs) transplantation has been suggested to relieve ALF. Interestingly, microRNA-214 (miR-214) could potentially regulate differentiation and migration of BMSCs. The present study aims to inquire whether miR-214 affects therapeutic potential of BMSCs transplantation by targeting PIM-1 in ALF. 120 male Wistar rats were induced as ALF model rats and transplanted with BMSCs post-alteration of miR-214 or PIM-1 expression. Further experiments were performed to detect biochemical index (alanine aminotransferase [ALT], aspartate transaminase [AST], total bilirubin [TBiL]), and expression of miR-214, PIM-1, hepatocyte growth factor (HGF), caspase 3, tumor necrosis factor-α (TNF-α), and interleukin-10 (IL-10) in rat serum. Apart from the above detection, apoptosis of hepatocytes and Ki67 protein expression in hepatic tissues of rats were additionally assessed. After BMSCs transplantation with miR-214 inhibition, a decreased expression of ALT, AST, and TBiL yet an increased expression of HGF was shown, coupled with a decline in the expression of caspase 3, TNF-α, and IL-10. Meanwhile, alleviated hepatic injury and decreased apoptotic index of hepatic cells were observed and the positive rate of Ki67 protein expression was significantly increased. Moreover, miR-214 and caspase 3, TNF-α, and IL-10 decreased notably, while PIM-1 was upregulated in response to miR-214 inhibition. Strikingly, the inhibition of PIM-1 reversed effects triggered by miR-214 inhibition. These findings indicated that downregulation of miR-214 improves therapeutic potential of BMSCs transplantation by upregulating PIM-1 for ALF.

Derivation of Macrophages from Mouse Bone Marrow

Macrophages are cellular components of the immune system that are essential for responding to pathogens, initiating inflammation and maintaining tissue homeostasis. Isolation, culture, and functional characterization of bone marrow-derived macrophages from mice are exceptionally powerful in vitro techniques used to examine aspects of macrophage biology, including effector functions, such as phagocytosis, cytokine secretion, oxidative burst, migration, and antigen processing and presentation. These studies can be carried out using wild-type, gene-ablated, and/or transgenic mice. The quantity, purity, and ease of culture of these cells enhance their utility for primary cell cultures to understand macrophage biology. Mouse macrophages have become a cognate animal model for the study of human macrophage biology and disease. This chapter outlines protocols used to generate, polarize, quantitate, and functionally evaluate macrophages derived from bone marrow precursor cells.

Enhanced osteogenesis of bone marrow stem cells cultured on hydroxyapatite/collagen I scaffold in the presence of low-frequency magnetic field

As a non-invasive biophysical therapy, electromagnetic fields (EMF) have been widely used to promote the healing of fractures. In the present study, hydroxyapatite/collagen I (HAC) loaded with rabbit bone marrow mesenchymal stem cells (MSCs) were cultured in a dynamic perfusion bioreactor and exposed to EMF of 15 Hz/1mT. Osteogenic differentiation of the seeded cells was analyzed through the evaluation of ALP activity and osteogenesis-related genes expression in vitro. The in vivo osteogenesis efficacy of the cell laden HAC constructs treated with/without EMF was evaluated through a rabbit femur condyle defect model. The results showed that EMF of 15 Hz/1mT could enhance the osteogenic differentiation of the cells seeded on HAC scaffold. Furthermore, the in vivo experiments demonstrated that EMF exposure could promote bone regeneration within the defect and bone integration between the graft and host bone. Taking together, the MSCs seeded HAC scaffold combined with EMF exposure could be a promising approach for bone tissue engineering.

Infusing Mesenchymal Stromal Cells into Porcine Kidneys during Normothermic Machine Perfusion: Intact MSCs Can Be Traced and Localised to Glomeruli

Normothermic machine perfusion (NMP) of kidneys offers the opportunity to perform active interventions, such as the addition of mesenchymal stromal cells (MSCs), to an isolated organ prior to transplantation. The purpose of this study was to determine whether administering MSCs to kidneys during NMP is feasible, what the effect of NMP is on MSCs and whether intact MSCs are retained in the kidney and to which structures they home. Viable porcine kidneys were obtained from a slaughterhouse. Kidneys were machine perfused during 7 h at 37 °C. After 1 h of perfusion either 0, 10⁵, 10⁶ or 10⁷ human adipose tissue derived MSCs were added. Additional ex vivo perfusions were conducted with fluorescent pre-labelled bone-marrow derived MSCs to assess localisation and survival of MSCs during NMP. After NMP, intact MSCs were detected by immunohistochemistry in the lumen of glomerular capillaries, but only in the 10⁷ MSC group. The experiments with fluorescent pre-labelled MSCs showed that only a minority of glomeruli were positive for infused MSCs and most of these glomeruli contained multiple MSCs. Flow cytometry showed that the number of infused MSCs in the perfusion circuit steeply declined during NMP to approximately 10%. In conclusion, the number of circulating MSCs in the perfusate decreases rapidly in time and after NMP only a small portion of the MSCs are intact and these appear to be clustered in a minority of glomeruli.

Diagnostic Value of Flow Cytometry Standardized Using the European LeukemiaNet for Myelodysplastic Syndrome

BACKGROUND

Myelodysplastic syndromes (MDS) and idiopathic cytopenia of undetermined significance (ICUS) are heterogeneous hematological disorders characterized by hematopoietic dysplasia and/or chromosomal aberrancy.

OBJECTIVES

This study aimed to evaluate the diagnostic value of flow cytometry standardized using the European LeukemiaNet (ELN) for MDS and ICUS by analyzing samples obtained from patients with cytopenia based on morphological examination, cytogenetic analysis, and flow cytometry.

METHODS

We retrospectively analyzed bone marrow samples aspirated from 253 consecutive patients (median age: 66 years [range: 1-92]) to identify the cause of cytopenia.

RESULTS

Sixty patients presented with MDS, and 16 with ICUS. MDS subtypes were distributed as follows: MDS with single-lineage dysplasia (n = 10); MDS with multi-lineage dysplasia (n = 10); MDS with ringed sideroblasts (n = 4); MDS with excess blasts-1 (n = 9); MDS with excess blasts-2 (n = 13), MDS unclassified (n = 5); 5q-syndrome (n = 6); and MDS/myeloproliferative neoplasms (n = 3). Four representative ELN indexes were used. Two or more ELN MDS indexes were in the abnormal range in 35 MDS cases (58.3%) and 4 ICUS cases (25.0%).

CONCLUSIONS

Morphological examination remains the standard for MDS diagnosis. Considering the low incidence of genetically proven ICUS (20.2-27.5%), the low sensitivity of ELN MDS indexes for ICUS is considered a valuable alternative.

Osteogenic potential of sol-gel bioactive glasses containing manganese

Bioactive glasses (BGs) are widely used for bone regeneration, and allow the incorporation of different ions with therapeutic properties into the glass network. Amongst the different ions with therapeutic benefits, manganese (Mn) has been shown to influence bone metabolism and activate human osteoblasts integrins, improving cell adhesion, proliferation and spreading. Mn has also been incorporated into bioceramics as a therapeutic ion for improved osteogenesis. Here, up to 4.4 mol% MnO was substituted for CaO in the 58S composition (60 mol% SiO₂, 36 mol% CaO, 4 mol% P₂O₅) and its effects on the glass properties and capability to influence the osteogenic differentiation were evaluated. Mn-containing BGs with amorphous structure, high specific surface area and nanoporosity were obtained. The presence of Mn²⁺ species was confirmed by X-ray photoelectron spectroscopy (XPS). Mn-containing BGs presented no cytotoxic effect on human mesenchymal stem cells (hMSCs) and enabled sustained ion release in culture medium. hMSCs osteogenic differentiation stimulation and influence on the mineralisation process was also confirmed through the alkaline phosphatase (ALP) activity, and expression of osteogenic differentiation markers, such as collagen type I, osteopontin and osteocalcin, which presented higher expression in the presence of Mn-containing samples compared to control. Results show that the release of manganese ions from bioactive glass provoked human mesenchymal stem cell (hMSC) differentiation down a bone pathway, whereas hMSCs exposed to the Mn-free glass did not differentiate. Mn incorporation offers great promise for obtaining glasses with superior properties for bone tissue regeneration.

Expression and Functional Role of TRPV4 in Bone Marrow-Derived CD11c+ Cells

The increase in cytosolic Ca²⁺ is essential in key effector functions of dendritic cells (DCs), including differentiation, maturation, cytokine expression, and phagocytosis. Although several Ca²⁺-permeable ion channels have been described in DCs, the contribution of transient receptor potential (TRP) channels remains poorly understood. Here, we investigated whether TRPV4 plays a role in the differentiation, maturation, and phagocytosis of granulocyte-macrophage colony-stimulating factor (GM-CSF)-induced mouse bone marrow-derived cells (BMDCs). Using intracellular Ca²⁺ imaging experiments, we found that TRPV4 was functionally expressed in the plasma membrane of immature CD11c⁺ BMDCs and that its activity and expression were downregulated in CD11c⁺ BMDCs matured with lipopolysaccharide (LPS). Comparative analysis of the GM-CSF-stimulated cells showed that Trpv4 knockout and wild-type bone marrow cultures had a similar distribution of differentiated cells, generating a heterogenous culture population rich in CD11c⁺, CD11b⁺ cells, and low levels of F4/80⁺ cells. The lack of TRPV4 did not prevent the LPS-induced nuclear translocation of NF-κB, the upregulation of the proinflammatory cytokines IL-6 and IL-12, or the upregulation of the maturation markers CD40, CD80, and CD86. In contrast, TRPV4-deficient CD11c⁺ BMDCs exhibited a significantly reduced endocytic capacity of IgG-coated beads, but the internalization of uncoated beads in the absence of TRPV4 was not affected. Taken together, our results demonstrate that TRPV4 was dispensable in the differentiation and maturation of mouse CD11c⁺ BMDCs but contributed to the mechanism underlying Fc receptor-mediated phagocytosis. Overall, our results further strengthen the role of TRPV4 in immune-related processes.

SPIO nanoparticle-labeled bone marrow mesenchymal stem cells inhibit pulmonary EndoMT induced by SiO2

Endothelial-mesenchymal transition (EndoMT) is a key step during lung fibrosis. Studies have shown that bone marrow mesenchymal stem cells (BMSCs) may act as therapeutic candidates for lung fibrosis. However, the effects of BMSCs on EndoMT induced by SiO₂ have not been elucidated, and means to label and track grafted cells have been lacking. The current study explored whether BMSCs prevented pulmonary fibrosis by targeting EndoMT, as well as analyzed the distribution of BMSCs labeled with superparamagnetic iron oxide (SPIO) nanoparticles during treatment. TIE2-GFP mice, human umbilical vein endothelial cells (HUVECs), and BMSCs labeled with SPIO nanoparticles were used to explore the distributions and therapeutic effects of BMSCs in vivo and in vitro. We found that BMSCs reversed lung fibrosis by targeting EndoMT in vivo. Furthermore, we show that BMSCs labeled with SPIO nanoparticles could be used to track stem cells reliably in the lungs for 14 days. Conditioned medium from BMSCs attenuated the increased functional changes and reversed the SiO₂-induced upregulation of ER stress and autophagy markers irrespective of whether they were nanoparticle labeled or not. Our findings identify novel methods to track labeled BMSCs with therapeutic potential.

SLIT2 inhibits osteoclastogenesis and bone resorption by suppression of Cdc42 activity

Axon guidance molecules, originally found to mediate the positioning of axons during nerve development, have been receiving great attention due to their critical roles in regulating bone metabolism. Recently, SLITs, another group of neuronal guidance proteins, were found to be significantly expressed in bone cells. Furthermore, we had provided experimental evidence that SLIT3 is an osteoclast-secreted coupling factor playing an osteoprotective role. Therefore, we hypothesized that SLIT2, a member of the SLIT family, may also affect bone homeostasis. SLIT2 suppressed osteoclast differentiation in a dose-dependent manner and in vitro bone resorption by more than 80%. Consistently, the expression of osteoclast differentiation markers, such as tartrate-resistant acid phosphatase (Trap) and calcitonin receptor (Ctr), was decreased by SLIT2. The migration and fusion of preosteoclasts were markedly reduced in the presence of SLIT2, suggesting that SLIT2 mainly functions in the early stage of osteoclastogenesis. SLIT2 suppressed Cdc42 activity among small GTPases, whereas Cdc42 overexpression almost completely reversed the SLIT2-mediated suppression of osteoclast differentiation. Among ROBO1-4, the SLIT receptors, ROBO1 and ROBO3 were known to be predominantly expressed in osteoclast lineages. A binding ELISA experiment in mouse bone marrow-derived macrophages showed that ROBO1, rather than ROBO3, was directly associated with SLIT2, and gene silencing with Robo1 siRNA blocked the SLIT2-mediated suppression of osteoclastogenesis. Taken together, our results indicated that SLIT2 inhibits osteoclastogenesis and the resultant bone resorption by decreasing Cdc42 activity, suggesting that this was a potential therapeutic target in metabolic bone diseases related to high bone turnover states.

Bone marrow vs Wharton's jelly mesenchymal stem cells in experimental sepsis: a comparative study

BACKGROUND

The use of mesenchymal stem cells (MSCs) is being extensively studied in clinical trials in the setting of various diseases including diabetes, stroke, and progressive multiple sclerosis. The unique immunomodulatory properties of MSCs also point them as a possible therapeutic tool during sepsis and septic shock, a devastating syndrome associated with 30-35% mortality. However, MSCs are not equal regarding their activity, depending on their tissue origin. Here, we aimed at comparing the in vivo properties of MSCs according to their tissue source (bone marrow (BM) versus Wharton's jelly (WJ)) in a murine cecal ligation and puncture (CLP) model of sepsis that mimics a human peritonitis. We hypothesized that MSC properties may vary depending on their tissue source in the setting of sepsis.

METHODS

CLP, adult, male, C57BL/6 mice were randomized in 3 groups receiving respectively 0.25 × 106 BM-MSCs, 0.25 × 106 WJ-MSCs, or 150 μL phosphate-buffered saline (PBS) intravenously 24 h after the CLP procedure.

RESULTS

We observed that both types of MSCs regulated leukocyte trafficking and reduced organ dysfunction, while only WJ-MSCs were able to improve bacterial clearance and survival.

CONCLUSION

This study highlights the importance to determine the most appropriate source of MSCs for a given therapeutic indication and suggests a better profile for WJ-MSCs during sepsis.

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.

Study of the Osteoindictive Properties of Protein-Modified Polylactide Scaffolds

Bone marrow mesenchymal stromal cells are multipotent and can differentiate into cells of various tissues, which determines their high importance for clinical application. We performed an in vitro study of the osteogenic potential of mesenchymal stromal cells cultured on intact polylactide scaffolds or scaffolds modified with collagen I or fibrin. Scanning electron microscopy showed that the cells formed osteogenic nodules or osteogenic nodules on both intact and fibrin-modified polylactide scaffolds. Spectrophotometric detection of alkaline phosphatase activity on days 7 and 11 showed that mesenchymal stromal cell grown on intact polylactide scaffolds and on scaffolds modified with collagen type I or fibrin more intensively synthesized alkaline phosphatase than in the control (culture plastic). This dependence increases in the presence of osteogenic differentiation factors in the medium. After long-term culturing (4 weeks), the presence of calcium deposits detected by alizarin red staining confirmed the osteoinductive properties of intact and protein-modified polylactide scaffolds. These findings suggest that polylactide scaffolds and collagen I increase the osteogenic differentiation potential of mesenchymal stromal cells.

Enhancing osseointegration of titanium implants through large-grit sandblasting combined with micro-arc oxidation surface modification

PURPOSE

The demand for titanium dental implants has risen sharply. However, the clinical success rate of implant surgery needs to be improved. In this paper, we report a novel surface modification strategy, large-grit sandblasting combined with micro-arc oxidation (SL-MAO), aiming to promote peri-implant bone formation and osseointegration of titanium implants.

MATERIALS AND METHODS

Modified titanium samples were prepared by large-grit sandblasting and acid etching (SLA), micro-arc oxidation (MAO), and SL-MAO. The resulting topographical changes and chemical composition of the samples were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively, and the biocompatibility and bioactivity were analyzed by bone-marrow mesenchymal stem cells (BMMSC) adhesion tests. Modified titanium implants were also inserted into the femurs of beagle dogs, and their competence of osseointegration was appraised by quantitative histomorphometry and micro-computed-tomography (micro-CT) analyses.

RESULTS

Compared to SLA and MAO techniques, SL-MAO surface modification further enhanced titanium surfaces by creating a topographic morphology characterized by both micron-sized craters and sub-micron-scale pits, and resulted in superior chemical composition, which promoted cell adhesion, proliferation, and osteogenic differentiation. SL-MAO-modified titanium implants osseointegrated more efficiently than SLA or MAO controls, with significantly higher bone-area (BA) ratio and bone-implant contact (BIC) in the peri-implant region.

CONCLUSIONS

The SL-MAO surface modification technique optimized the surface properties of titanium implants and enhanced peri-implant bone formation and osseointegration.

Mesenchymal Stem Cells from Mouse Adipose Tissue Stimulate Tumor Growth

We studied the effect of mesenchymal stem cells from the bone marrow and adipose tissue on the growth rate of melanoma B16 and mammary adenocarcinoma Ca755 tumors after their co-administration with tumor cells to syngeneic mice. Stimulation of tumor growth and formation of melanoma metastases in the lungs was found under the influence of adipose tissue-derived, but not bone marrow-derived stem cells. At delayed terms after irradiation in sublethal doses, the adipose tissue-derived mesenchymal stem cells also stimulated the tumor growth. Stimulation of the tumor growth by adipose tissue-derived mesenchymal stem cells was caused by factors secreted by these cells. Transplantation of mesenchymal stem cells to humans is possible only after accurate exclusion of malignant tumors.

Anti-Osteoporotic Effects of Kukoamine B Isolated from Lycii Radicis Cortex Extract on Osteoblast and Osteoclast Cells and Ovariectomized Osteoporosis Model Mice

Osteoporosis is an abnormal bone remodeling condition characterized by decreased bone density, which leads to high risks of fracture. Previous study has demonstrated that Lycii Radicis Cortex (LRC) extract inhibits bone loss in ovariectomized (OVX) mice by enhancing osteoblast differentiation. A bioactive compound, kukoamine B (KB), was identified from fractionation of an LRC extract as a candidate component responsible for an anti-osteoporotic effect. This study investigated the anti-osteoporotic effects of KB using in vitro and in vivo osteoporosis models. KB treatment significantly increased the osteoblastic differentiation and mineralized nodule formation of osteoblastic MC3T3-E1 cells, while it significantly decreased the osteoclast differentiation of primary-cultured monocytes derived from mouse bone marrow. The effects of KB on osteoblastic and osteoclastic differentiations under more physiological conditions were also examined. In the co-culture of MC3T3-E1 cells and monocytes, KB promoted osteoblast differentiation but did not affect osteoclast differentiation. In vivo experiments revealed that KB significantly inhibited OVX-induced bone mineral density loss and restored the impaired bone structural properties in osteoporosis model mice. These results suggest that KB may be a potential therapeutic candidate for the treatment of osteoporosis.

Molecular Profiling and Functional Analysis of Macrophage-Derived Tumor Extracellular Vesicles

Extracellular vesicles (EVs), including exosomes, modulate multiple aspects of cancer biology. Tumor-associated macrophages (TAMs) secrete EVs, but their molecular features and functions are poorly characterized. Here, we report methodology for the enrichment, quantification, and proteomic and lipidomic analysis of EVs released from mouse TAMs (TAM-EVs). Compared to source TAMs, TAM-EVs present molecular profiles associated with a Th1/M1 polarization signature, enhanced inflammation and immune response, and a more favorable patient prognosis. Accordingly, enriched TAM-EV preparations promote T cell proliferation and activation ex vivo. TAM-EVs also contain bioactive lipids and biosynthetic enzymes, which may alter pro-inflammatory signaling in the cancer cells. Thus, whereas TAMs are largely immunosuppressive, their EVs may have the potential to stimulate, rather than limit, anti-tumor immunity.

[Cytoskeleton remodeling of rat bone marrow mesenchymal stem cells induced by fibroblast growth factor 2]

Objective To investigate the effects of fibroblast growth factor 2 (FGF-2) on the cytoskeleton and morphology of rat bone marrow mesenchymal stem cells (BMSCs). Methods Morphological and cytoskeleton changes of BMSCs were observed by scanning electron microscopy and rhodamine-phalloidin staining in Transwell^TM co-culture system of rat vascular endothelial cells (RAECs) and BMSCs. The content of FGF-2 in cell supernatants were detected by ELISA, and the mRNA expression of FGF-2 in both conventional and co-cultured cells were evaluated by real-time quantitative PCR. NVP-BGJ398, an inhibitor of FGF-2 receptor was added into the co-culture system to block FGF-2 signal and its effect on BMSCs skeleton was observed. Recombinant FGF-2 was supplemented into the conventional medium of BMSCs to further verify the effect of exogenous FGF-2. Results After co-cultured with RAECs, BMSCs gradually stretched, contracted and formed a large number of filopodia. The content of FGF-2 increased in the co-culture system and was mainly secreted by RAECs. Cytoskeleton remodeling of BMSCs was significantly blocked by the inhibitor of FGF-2 receptor and the cells were mostly short spindle-shaped and arranged in a spiral pattern. Exogenous FGF-2 promoted the contraction and edge stretching of BMSCs, forming filopodia with staggered distribution. Conclusion FGF-2 secreted by RAECs induces cytoskeletal remodeling of BMSCs.

A Mussel-Inspired Persistent ROS-Scavenging, Electroactive, and Osteoinductive Scaffold Based on Electrochemical-Driven In Situ Nanoassembly

Conductive polymers are promising for bone regeneration because they can regulate cell behavior through electrical stimulation; moreover, they are antioxidative agents that can be used to protect cells and tissues from damage originating from reactive oxygen species (ROS). However, conductive polymers lack affinity to cells and osteoinductivity, which limits their application in tissue engineering. Herein, an electroactive, cell affinitive, persistent ROS-scavenging, and osteoinductive porous Ti scaffold is prepared by the on-surface in situ assembly of a polypyrrole-polydopamine-hydroxyapatite (PPy-PDA-HA) film through a layer-by-layer pulse electrodeposition (LBL-PED) method. During LBL-PED, the PPy-PDA nanoparticles (NPs) and HA NPs are in situ synthesized and uniformly coated on a porous scaffold from inside to outside. PDA is entangled with and doped into PPy to enhance the ROS scavenging rate of the scaffold and realize repeatable, efficient ROS scavenging over a long period of time. HA and electrical stimulation synergistically promote osteogenic cell differentiation on PPy-PDA-HA films. Ultimately, the PPy-PDA-HA porous scaffold provides excellent bone regeneration through the synergistic effects of electroactivity, cell affinity, and antioxidative activity of the PPy-PDA NPs and the osteoinductivity of HA NPs. This study provides a new strategy for functionalizing porous scaffolds that show great promise as implants for tissue regeneration.

Regenerative Capacity of Adipose Derived Stem Cells (ADSCs), Comparison with Mesenchymal Stem Cells (MSCs)

Adipose tissue is now on the top one of stem cell sources regarding its accessibility, abundance, and less painful collection procedure when compared to other sources. The adipose derived stem cells (ADSCs) that it contains can be maintained and expanded in culture for long periods of time without losing their differentiation capacity, leading to large cell quantities being increasingly used in cell therapy purposes. Many reports showed that ADSCs-based cell therapy products demonstrated optimal efficacy and efficiency in some clinical indications for both autologous and allogeneic purposes, hence becoming considered as potential tools for replacing, repairing, and regenerating dead or damaged cells. In this review, we analyzed the therapeutic advancement of ADSCs in comparison to bone marrow (BM) and umbilical cord (UC)-mesenchymal stem cells (MSCs) and designed the specific requirements to their best clinical practices and safety. Our analysis was focused on the ADSCs, rather than the whole stromal vascular fraction (SVF) cell populations, to facilitate characterization that is related to their source of origins. Clinical outcomes improvement suggested that these cells hold great promise in stem cell-based therapies in neurodegenerative, cardiovascular, and auto-immunes diseases.

Regenerative Capacity of Adipose Derived Stem Cells (ADSCs), Comparison with Mesenchymal Stem Cells (MSCs)

Adipose tissue is now on the top one of stem cell sources regarding its accessibility, abundance, and less painful collection procedure when compared to other sources. The adipose derived stem cells (ADSCs) that it contains can be maintained and expanded in culture for long periods of time without losing their differentiation capacity, leading to large cell quantities being increasingly used in cell therapy purposes. Many reports showed that ADSCs-based cell therapy products demonstrated optimal efficacy and efficiency in some clinical indications for both autologous and allogeneic purposes, hence becoming considered as potential tools for replacing, repairing, and regenerating dead or damaged cells. In this review, we analyzed the therapeutic advancement of ADSCs in comparison to bone marrow (BM) and umbilical cord (UC)-mesenchymal stem cells (MSCs) and designed the specific requirements to their best clinical practices and safety. Our analysis was focused on the ADSCs, rather than the whole stromal vascular fraction (SVF) cell populations, to facilitate characterization that is related to their source of origins. Clinical outcomes improvement suggested that these cells hold great promise in stem cell-based therapies in neurodegenerative, cardiovascular, and auto-immunes diseases.

IGF-1 overexpression improves mesenchymal stem cell survival and promotes neurological recovery after spinal cord injury

BACKGROUND

Survival and therapeutic actions of bone marrow-derived mesenchymal stem cells (BMMSCs) can be limited by the hostile microenvironment present during acute spinal cord injury (SCI). Here, we investigated whether BMMSCs overexpressing insulin-like growth factor 1 (IGF-1), a cytokine involved in neural development and injury repair, improved the therapeutic effects of BMMSCs in SCI.

METHODS

Using a SCI contusion model in C57Bl/6 mice, we transplanted IGF-1 overexpressing or wild-type BMMSCs into the lesion site following SCI and evaluated cell survival, proliferation, immunomodulation, oxidative stress, myelination, and functional outcomes.

RESULTS

BMMSC-IGF1 transplantation was associated with increased cell survival and recruitment of endogenous neural progenitor cells compared to BMMSC- or saline-treated controls. Modulation of gene expression of pro- and anti-inflammatory mediators was observed after BMMSC-IGF1 and compared to saline- and BMMSC-treated mice. Treatment with BMMSC-IGF1 restored spinal cord redox homeostasis by upregulating antioxidant defense genes. BMMSC-IGF1 protected against SCI-induced myelin loss, showing more compact myelin 28 days after SCI. Functional analyses demonstrated significant gains in BMS score and gait analysis in BMMSC-IGF1, compared to BMMSC or saline treatment.

CONCLUSIONS

Overexpression of IGF-1 in BMMSC resulted in increased cell survival, immunomodulation, myelination, and functional improvements, suggesting that IGF-1 facilitates the regenerative actions of BMMSC in acute SCI.

Preconditioning in an Inflammatory Milieu Augments the Immunotherapeutic Function of Mesenchymal Stromal Cells

Multipotent mesenchymal stromal cells (MSCs) have emerged as potent therapeutic agents for multiple indications. However, recent evidence indicates that MSC function is compromised in the physiological post-injury milieu. In this study, bone marrow (BM)- and adipose-derived (AD)-MSCs were preconditioned in hypoxia with or without inflammatory mediators to potentiate their immunotherapeutic function in preparation for in vivo delivery. Human MSCs were cultured for 48 hours in either normoxia (21% O₂) or hypoxia (2% O₂) with or without the addition of Cytomix, thus creating 4 groups: 1) normoxia (21%); 2) Cytomix-normoxia (+21%); 3) hypoxia (2%); and 4) Cytomix-hypoxia (+2%). The 4 MSC groups were subjected to comprehensive evaluation of their characteristics and function. Preconditioning did not alter common MSC surface markers; nonetheless, Cytomix treatment triggered an increase in tissue factor (TF) expression. Moreover, the BM-MSCs and AD-MSCs from the +2% group were not able to differentiate to chondrocytes and osteoblasts, respectively. Following Cytomix preconditioning, the metabolism of MSCs was significantly increased while viability was decreased in AD-MSCs, but not in BM-MSCs. MSCs from both tissues showed a significant upregulation of key anti-inflammatory genes, increased secretion of IL-1 receptor antagonist (RA), and enhanced suppression of T-cell proliferation following the Cytomix treatment. Similarly, following a lipopolysaccharide challenge, the Cytomix-treated MSCs suppressed TNF-α secretion, while promoting the production of IL-10 and IL-1RA. These preconditioning approaches facilitate the production of MSCs with robust anti-inflammatory properties. AD-MSCs preconditioned with Cytomix under normoxia appear to be the most promising therapeutic candidates; however, safety concerns, such as thrombogenic disposition of cells due to TF expression, should be carefully considered prior to clinical translation.

Temporal and spatial profile of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) in ischemic stroke in mice

Although T cells play important roles in the pathophysiology of ischemic stroke, the dynamics of T cells remains unclear. In cancer, polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) contribute to the maintenance of the tumor microenvironment by suppressing T cells. However, the presence of these cells has never been examined in ischemic brain. Therefore, we examined the temporal and spatial profiles of PMN-MDSCs, which are defined as the CD11b⁺Ly6C^lowLy6G⁺ cells with higher expression levels of Nox2 and C/EBP Homologous Protein (CHOP) mRNA than normal neutrophil. Fluorescence-activated cell sorter (FACS) analysis showed that the count of CD11b⁺Ly6C^lowLy6G⁺ cells was increased in the ischemic hemisphere and bone marrow at 72 hours, as well as in the spleen 24 hours after transient middle cerebral artery occlusion in mice. In contrast, the contralateral hemisphere, normal bone marrow, and normal spleen contained few CD11b⁺Ly6C^lowLy6G⁺ cells. Real-time reverse transcription polymerase chain reaction revealed that CD11b⁺Ly6C^lowLy6G⁺ cells sorted from brain and spleen 72 hours after ischemia had greater expression of Nox2 and CHOP mRNA than neutrophils in bone marrow, suggesting that these cells constitute PMN-MDSCs. Immunohistochemistry showed that CD11b⁺Ly6G⁺ cells were located in the ischemic core and border zone, indicating that PMN-MDSCs might be endemic to these regions. Although neutrophils are believed to invade infarct regions 48–72 hours after ischemia, the present study suggested that some of these cells are in fact PMN-MDSCs. Further studies on the function of PMN-MDSCs might unveil the unknown mechanisms of T cell activation and recruitment in ischemic stroke.

Reversal of established liver fibrosis by IC-2-engineered mesenchymal stem cell sheets

Chronic hepatitis viral infection, alcoholic intoxication, and obesity cause liver fibrosis, which progresses to decompensated liver cirrhosis, a disease for which medical demands cannot be met. Since there are currently no approved anti-fibrotic therapies for established liver fibrosis, the development of novel modalities is required to improve patient prognosis. In this study, we clarified the anti-fibrotic effects of cell sheets produced from human bone marrow-derived mesenchymal stem cells (MSCs) incubated on a temperature-sensitive culture dish with the chemical compound IC-2. Orthotopic transplantation of IC-2-engineered MSC sheets (IC-2 sheets) remarkably reduced liver fibrosis induced by chronic CCl4 administration. Further, the marked production of fibrolytic enzymes such as matrix metalloproteinase (MMP)-1 and MMP-14, as well as thioredoxin, which suppresses hepatic stellate cell activation, was observed in IC-2 sheets. Moreover, the anti-fibrotic effect of IC-2 sheets was much better than that of MSC sheets. Finally, knockdown experiments revealed that MMP-14 was primarily responsible for the reduction of liver fibrosis. Here, we show that IC-2 sheets could be a promising therapeutic option for established liver fibrosis.

Quantitative and Qualitative Characterization of Phagocytic Activity of Macrophages of Bone Marrow and Fetal Origin

We compared phagocytic activity of macrophages of monocyte origin and Kupffer cells under the influence of M1 and M2 inducers and without activation. Cultures of monocyte-derived macrophages and Kupffer cells were characterized by intensive expression of CD68 that was not affected by activation factors. At the same time, these cultures demonstrated different dynamics of phagocytic activity. Monocyte-derived macrophages initially had more pronounced absorption capacity that gradually increased during the experiment. Kupffer cells were characterized by abrupt fluctuations of phagocytic activity: sharp growth and rapid saturation. Despite these differences, the endosomes produced by monocyte-derived macrophages and Kupffer cells had similar degrees of maturity.

Porous Phosphate-Based Glass Microspheres Show Biocompatibility, Tissue Infiltration, and Osteogenic Onset in an Ovine Bone Defect Model

Phosphate-based glasses (PBGs) are bioactive and fully degradable materials with tailorable degradation rates. PBGs can be produced as porous microspheres through a single-step process, using changes in their formulation and geometry to produce varying pore sizes and interconnectivity for use in a range of applications, including biomedical use. Calcium phosphate PBGs have recently been proposed as orthobiologics, based on their in vitro cytocompatibility and ion release profile. In this study, porous microspheres made of two PBG formulations either containing TiO₂ (P40Ti) or without (P40) were implanted in vivo in a large animal model of bone defect. The biocompatibility and osteogenic potential of these porous materials were assessed 13 weeks postimplantation in sheep and compared to empty defects and autologous bone grafts used as negative and positive controls. Histological analysis showed marked differences between the two formulations, as lower trabeculae-like interconnection and higher fatty bone marrow content were observed in the faster degrading P40-implanted defects, while the slower degrading P40Ti material promoted dense interconnected tissue. Autologous bone marrow concentrate (BMC) was also incorporated within the P40 and P40Ti microspheres in some defects; however, no significant differences were observed in comparison to microspheres implanted alone. Both formulations induced the formation of a collagen-enriched matrix, from 20 to 40% for P40 and P40Ti2.5 groups, suggesting commitment toward the bone lineage. With the faster degrading P40 formulation, mineralization of the tissue matrix was observed both with and without BMC. Some lymphocyte-like cells and foreign body multinucleated giant cells were observed with P40Ti2.5, suggesting that this more durable formulation might be linked to an inflammatory response. In conclusion, these first in vivo results indicate that PBG microspheres could be useful candidates for bone repair and regenerative medicine strategies and highlight the role of material degradation in the process of tissue formation and maturation.

Bone marrow mesenchymal stem cells: Aging and tissue engineering applications to enhance bone healing

Bone has well documented natural healing capacity that normally is sufficient to repair fractures and other common injuries. However, the properties of bone change throughout life, and aging is accompanied by increased incidence of bone diseases and compromised fracture healing capacity, which necessitate effective therapies capable of enhancing bone regeneration. The therapeutic potential of adult mesenchymal stem cells (MSCs) for bone repair has been long proposed and examined. Actions of MSCs may include direct differentiation to become bone cells, attraction and recruitment of other cells, or creation of a regenerative environment via production of trophic growth factors. With systemic aging, MSCs also undergo functional decline, which has been well investigated in a number of recent studies. In this review, we first describe the changes in MSCs during aging and discuss how these alterations can affect bone regeneration. We next review current research findings on bone tissue engineering, which is considered a promising and viable therapeutic solution for structural and functional restoration of bone. In particular, the importance of MSCs and bioscaffolds is highlighted. Finally, potential approaches for the prevention of MSC aging and the rejuvenation of aged MSC are discussed.

Defined Substrate by Aptamer Modification with the Balanced Properties of Selective Capture and Stemness Maintenance of Mesenchymal Stem Cells

The recruitment of endogenous mesenchymal stem cells (MSCs), as an alluring approach for in situ tissue regeneration, always accompanies with other types of cells. Therefore, it is of enormous value to bestow a substrate with the property of selective capture to MSCs. However, it was reported that when MSCs are cultured on a substrate with excessive affinity, their stemness diminished. Therefore, constructing a substrate with the balanced ability of selective capture and stemness maintenance becomes a big challenge. In this study, an Aptamer 19S (Apt19S)-modified substrate was fabricated by grafting Apt19S on a PEGylated glass substrate. The X-ray photoelectron spectroscopy results verified that the antifouling poly(ethylene glycol) (PEG) layer was created. Tracking by ellipsometry, the thicknesses of PEG layers were proved to increase with PEG concentration. The results of the quartz crystal microbalance also validated that the Apt19S densities could be modulated by the concentrations of the Apt19S solution. The results of the cell adhesion assay indicated that the modification of Apt19S caused a significant increase in the adhesion ratio and area of rBMSCs. Selective adhesion was confirmed by coculture of rBMSCs with macrophages and NIH3T3 cells, demonstrating that a higher proportion of rBMSCs adhered to the Apt19S-modified substrate. The results of specific capture were further confirmed by a flow model to simulate the body fluid flow. The comprehensive results of reverse transcription polymerase chain reaction, immunofluorescence staining, proliferation capacity, and differentiation assay showed that the stemness of rBMSCs was maintained better on a substrate with the appropriate Apt19S density. All of these results indicated that Apt19S modification is an effective strategy to endow a substrate with the specific capture ability of MSCs, and the balance between selective capture and stemness maintenance can be achieved by the precise regulation of the aptamer density.

Cell-secreted extracellular matrix influences cellular composition sequestered from unprocessed bone marrow aspirate for osteogenic grafts

Bone marrow aspirates provide a rich source of cells for use in tissue engineering of bone and other clinical indications. However, progenitor cells such as mesenchymal stem cells (MSCs) account for a small fraction of nucleated cells in bone marrow aspirate (BMA), requiring extensive culture expansion. Accessory cell populations such as endothelial or hematopoietic cells can potentiate the bone-forming potential of MSCs, and cell-secreted extracellular matrix (ECM) can increase cell seeding efficiency and osteogenic differentiation of heterogeneous cell populations. In this study, we hypothesized that cell-secreted ECM could be used to sequester MSCs and accessory cells from BMA for bone regeneration. To generate 3D implantable constructs, BMA was resuspended in media with or without type I collagen or ECM and injected into a perfusion bioreactor system. The addition of protein coatings increased cell seeding efficiency compared to uncoated scaffolds. Compared to fresh BMA, the culture of BMA on all scaffolds reduced the proportion of CD45+ myeloid cells and increased CD31+CD45- endothelial cells. Compared to uncoated scaffolds, we observed a 143- and 30-fold increase in MSCs when fresh BMA was cultured on ECM- or collagen-coated scaffolds, respectively. Upon subcutaneous implantation, ECM-coated scaffolds promoted cell survival and early vascularization. However, bone formation was comparable across all implant groups, suggesting additional osteogenic cues are necessary to increase the bone forming potential of fresh BMA. These results motivate further investigation into strategies which elicit more robust bone regeneration by tissue aspirates.

Cooperative impact of thiazolidinedione and fatty acid synthase on human osteogenesis

Previous, we found that the small molecules capable of inhibiting the expression and the pro-adipogenic activity of ZNF521 might improve the osteogenic performance of aging human bone marrow MSCs (bmMSCs), and that fatty acid synthase (FASN) was a critical effector of ZNF521's pro-adipogenic activity. Here, by characterizing the netoglitazone (MCC-555), one of the thiazolidinediones known as adipogenic enhancers, as an inhibitor of ZNF521 expression, we found that MCC-555 indeed also harbored pro-osteoblastic effect. Investigation revealed that MCC-555 might function as a GSK3β inhibitor to promote osteoblastogenesis and bone formation. Importantly, combination of MCC-555 with FASN knockdown, but not with GW9662 (a PPARγ2 antagonist), blocked the pro-adipogenic but retained the pro-osteoblastic effect of MCC-555. Using a 3-dimentional culture system, we showed that MCC-555 facilitated the FASN-knockdown of aging human bmMSCs to form cell clusters in scaffolds, and to promote osteoblastic differentiation and biomineralization in cell clusters. These data indicated that MCC-555 promoted bmMSCs to produce bone-like tissues. Our data narrate a thiazolidinedione-based novel strategy to improve the osteogenic performance of aging bmMSCs to support the application of autologous aging bmMSCs in cell therapy and in producing bone-like tissues for repairing bone injury in the elderly.

DNMT and HDAC inhibitors modulate MMP-9-dependent H3 N-terminal tail proteolysis and osteoclastogenesis

BACKGROUND

MMP-9-dependent proteolysis of histone H3 N-terminal tail (H3NT) is an important mechanism for activation of gene expression during osteoclast differentiation. Like other enzymes targeting their substrates within chromatin structure, MMP-9 enzymatic activity toward H3NT is tightly controlled by histone modifications such as H3K18 acetylation (H3K18ac) and H3K27 monomethylation (H3K27me1). Growing evidence indicates that DNA methylation is another epigenetic mechanism controlling osteoclastogenesis, but whether DNA methylation is also critical for regulating MMP-9-dependent H3NT proteolysis and gene expression remains unknown.

RESULTS

We show here that treating RANKL-induced osteoclast progenitor (OCP) cells with the DNMT inhibitor 5-Aza-2'-deoxycytidine (5-Aza-CdR) induces CpG island hypomethylation and facilitates MMP-9 transcription. This increase in MMP-9 expression results in a significant enhancement of H3NT proteolysis and OCP cell differentiation. On the other hand, despite an increase in levels of H3K18ac, treatment with the HDAC inhibitor trichostatin A (TSA) leads to impairment of osteoclastogenic gene expression. Mechanistically, TSA treatment of OCP-induced cells stimulates H3K27ac with accompanying reduction in H3K27me1, which is a key modification to facilitate stable interaction of MMP-9 with nucleosomes for H3NT proteolysis. Moreover, hypomethylated osteoclastogenic genes in 5-Aza-CdR-treated cells remain transcriptionally inactive after TSA treatment, because H3K27 is highly acetylated and cannot be modified by G9a.

CONCLUSIONS

These findings clearly indicate that DNA methylation and histone modification are important mechanisms in regulating osteoclastogenic gene expression and that their inhibitors can be used as potential therapeutic tools for treating bone disorders.

A comparison of two protocols for optimal red blood cell depletion using Sepax-2 device for ABO-major incompatible transplantation in adults

PURPOSE OF THE STUDY

In ABO-incompatible bone marrow transplantation, an efficient depletion of red blood cells (RBC) within the graft is mandatory to avoid adverse events in transplanted patients. Using non therapeutic products, we evaluated the substitution of the standard density gradient-based separation (DGBS) over Ficoll-Paque with the use of an automated procedure intended for buffy coat only (SmartRedux software) introducing modifications within the settings to achieve a drastic reduction of the initial volume of the product. Both methods were conducted on the Sepax-2 device.

SAMPLES AND METHODS

RBC depletion rates and CD34+ cells recoveries from eight procedures with SmartRedux software using "in-house" settings (method A) were compared to those obtained from four procedures using NeatCell software, an automated DGBS over Ficoll-Paque (method B).

RESULTS

Median erythrocyte depletion of 95,4% (92,7%-99,0%) and 99,8% (99,0%-99,9%) were observed using methods A and B, respectively. Median residual RBC volumes in the final product were 19 mL (4,4 mL-31,2 mL) and 0,7 mL (0,4 mL-4,7 mL), respectively (p = 0,014). CD34+ cells recoveries of 90,9% (62,7%-102,1%) and 78,4% (64,1%-86,2%) were achieved for methods A and B. Median platelet depletion was 16,6% (10%-42,7%) and 89,8% (88,5%-92,4%) using methods A and B, respectively (p = 0,004). Processing duration was shorter using method A (168 ± 29 min) than method B (295 ± 21 min) (p = 0,004).

CONCLUSION

Both methods achieved satisfactory erythrocyte depletion and CD34+ recovery. The use of Sepax-2 device in association with SmartRedux software could be extended to efficiently deplete RBC from large-volume BM in a raw instead of DGBS.

Peripheral and systemic antigens elicit an expandable pool of resident memory CD8+ T cells in the bone marrow

BM has been put forward as a major reservoir for memory CD8⁺  T cells. In order to fulfill that function, BM should "store" memory CD8⁺ T cells, which in biological terms would require these "stored" memory cells to be in disequilibrium with the circulatory pool. This issue is a matter of ongoing debate. Here, we unequivocally demonstrate that murine and human BM harbors a population of tissue-resident memory CD8⁺ T (T_RM ) cells. These cells develop against various pathogens, independently of BM infection or local antigen recognition. BM CD8⁺ T_RM cells share a transcriptional program with resident lymphoid cells in other tissues; they are polyfunctional cytokine producers and dependent on IL-15, Blimp-1, and Hobit. CD8⁺ T_RM cells reside in the BM parenchyma, but are in close contact with the circulation. Moreover, this pool of resident T cells is not size-restricted and expands upon peripheral antigenic re-challenge. This works extends the role of the BM in the maintenance of CD8⁺ T cell memory to include the preservation of an expandable reservoir of functional, non-recirculating memory CD8⁺ T cells, which develop in response to a large variety of peripheral antigens.

[The transplantation of bone marrow mesenchymal stem cells pretreated with stromal cell-derived factor-1 alleviates the proliferation of endothelium and smooth muscle cells of carotid artery in rats]

Objective To investigating the effect of bone marrow mesenchymal stem cells (BMSCs) pretreated with stromal cell-derived factor-1 (SDF-1) on carotid stenosis in rats. Methods The plasmid carrying enhanced green fluorescent protein (EGFP) was transfected into BMSCs and then intravenously injected into rats. The rats were divided into carotid artery injury model control group, BMSCs transplantation group, and BMSCs pretreated with SDF-1 group. Two weeks after the cell transplantation, the injured vascular tissues were collected and EGFP expression was detected by immunofluorescence histochemistry to determine the homing of BMSCs. Four weeks after cell transplantation, the endothelialization of injured intima was observed by Evans blue staining, and CD31 expression in injured vessels was detected by the immunofluorescence technique. The neointimal hyperplasia of injured carotid arteries was observed by HE staining. The expression of proliferating cell nuclear antigen (PCNA) in injured vessels was detected by immunohistochemical staining. The protein level of vascular endothelial growth factor (VEGF) was tested by Western blot analysis. Results The transplantation of BMSCs pretreated with SDF-1 could effectively promote the homing of BMSCs to injured blood vessels, and promote the re-endothelialization of injured vessels. The neointimal area and neointimal area/medial area in the two BMSC-transplantation groups were both lower than those in the model control group, which were more significantly different from the BMSCs pretreated with SDF-1 group. The transplantation of BMSCs pretreated with SDF-1 could significantly increase the expression of CD31 and VEGF in injured intima and inhibit the expression of PCNA. Conclusion The transplantation of BMSCs pretreated with SDF-1 can inhibit the proliferation of smooth muscle cells in the media and reduce arterial stenosis by promoting the migration of BMSCs to the injured site and inducing the differentiation of BMSCs.

Characterization of Tendon-Specific Markers in Various Human Tissues, Tenocytes and Mesenchymal Stem Cells

Background

Unlike bone, cartilage, or muscle, tendon-specific markers are not well established. The purpose of the study was to investigate expression pattern and level of 6 well-known tendon-specific markers, in various human musculoskeletal tissues, tenocytes, and mesenchymal stem cells (MSCs).

Methods

Musculoskeletal tissue samples of tendon, bone, cartilage, nerve, muscle, and fat were obtained from patients undergoing orthopedic surgery. Tenocytes, MSCs from bone marrow, adipose tissue, and umbilical cord were isolated from each tissue and cultured. Six tendon-specific markers, scleraxis (Scx), tenomodulin (TNMD), thrombospondin-4 (TSP-4), tenascin-C (TNC), type I collagen (Col I), and type III collagen (Col III) were investigated in tendon tissue, tenocytes, and MSCs.

Results

mRNA levels of 6 tendon-specific markers were significantly higher in tendon tissue that in other connective tissues levels of Scx, TNMD, TSP-4, and Col III immediately decreased after plating tenocytes in culture dishes whereas those of TNC and Col I did not. In comparison with tendon tissue, mRNA levels pattern of Scx, TNMD, and TSP-4 in tenocytes were significantly higher than that in MSCs, but lower than in tendon tissue whereas expression pattern of TNC, Col I and III showed different pattern with each other.

Conclusion

This study demonstrated that 6 commonly used tendon-specific markers were mainly expressed in tendon tissue, but that expression level and pattern of the tendon-specific markers with respect to kinds of tissues, culture duration of tenocytes and sources of MSCs.

Characterization of cell fate probabilities in single-cell data with Palantir

Single-cell RNA sequencing studies of differentiating systems have raised fundamental questions regarding the discrete versus continuous nature of both differentiation and cell fate. Here we present Palantir, an algorithm that models trajectories of differentiating cells by treating cell fate as a probabilistic process and leverages entropy to measure cell plasticity along the trajectory. Palantir generates a high-resolution pseudo-time ordering of cells and, for each cell state, assigns a probability of differentiating into each terminal state. We apply our algorithm to human bone marrow single-cell RNA sequencing data and detect important landmarks of hematopoietic differentiation. Palantir's resolution enables the identification of key transcription factors that drive lineage fate choice and closely track when cells lose plasticity. We show that Palantir outperforms existing algorithms in identifying cell lineages and recapitulating gene expression trends during differentiation, is generalizable to diverse tissue types, and is well-suited to resolving less-studied differentiating systems.