IGFBP3 deposited in the human umbilical cord mesenchymal stem cell-secreted extracellular matrix promotes bone formation

Treatment of critical bone defects using calcium phosphate cement and mesoporous bioactive glass providing spatiotemporal drug delivery

Calcium phosphate cements (CPC) are currently widely used bone replacement materials with excellent bioactivity, but have considerable disadvantages like slow degradation. For critical-sized defects, however, an improved degradation is essential to match the tissue regeneration, especially in younger patients who are still growing. We demonstrate that a combination of CPC with mesoporous bioactive glass (MBG) particles led to an enhanced degradation in vitro and in a critical alveolar cleft defect in rats. Additionally, to support new bone formation the MBG was functionalized with hypoxia conditioned medium (HCM) derived from rat bone marrow stromal cells. HCM-functionalized scaffolds showed an improved cell proliferation and the highest formation of new bone volume. This highly flexible material system together with the drug delivery capacity is adaptable to patient specific needs and has great potential for clinical translation.

The role of insulin-like growth factor-1 in bone remodeling: A review

Insulin-like growth factor (IGF)-1 is a polypeptide hormone with vital biological functions in bone cells. The abnormal expression of IGF-1 has a serious effect on bone growth, particularly bone remodeling. Evidence from animal models and human disease suggested that both IGF-1 deficiency and excess cause changes in bone remodeling equilibrium, resulting in profound alterations in bone mass and development. Here, we first introduced the functions and mechanisms of the members of IGFs in bone. Subsequently, the critical role of IGF-1 in the process of bone remodeling were emphasized from the aspects of bone resorption and bone formation respectively. This review explains the mechanism of IGF-1 in maintaining bone mass and bone homeostasis to a certain extent and provides a theoretical basis for further research.

Skeletal stem/progenitor cells provide the niche for extramedullary hematopoiesis in spleen

In bone marrow, the niche which supports hematopoiesis and nurtures hematopoietic stem cells (HSCs) contains perivascular reticular cells representing a subset of skeletal stem/progenitor cells (SSPCs). These stromal cells which provide the niche are lost or become inadequate during stress, disease or ageing, such that HSCs leave bone marrow and enter spleen and other peripheral sites to initiate extramedullary hematopoiesis and particularly myelopoiesis. Spleen also maintains niches for HSCs under steady-state conditions, evident since neonatal and adult spleen contain HSCs in low number and provide low-level hematopoiesis. In spleen, HSCs are found in the sinusoidal-rich red pulp region also in the vicinity of perivascular reticular cells. These cells resemble to some extent the known stromal elements reflecting HSC niches in bone marrow, and are investigated here for their characteristics as a subset of SSPCs. The isolation of spleen stromal subsets and the generation of cell lines which support HSCs and myelopoiesis in vitro has led to the identification of perivascular reticular cells which are unique to spleen. Analysis of gene and marker expression, as well as differentiative potential, identifies an osteoprogenitor cell type, reflective of one of several subsets of SSPCs described previously in bone, bone marrow and adipose tissue. The combined information supports a model for HSC niches in spleen involving perivascular reticular cells as SSPCs having osteogenic, stroma-forming capacity. These associate with sinusoids in red pulp to form niches for HSCs and to support the differentiation of hematopoietic progenitors during extramedullary hematopoiesis.

Intrauterine botulinum toxin A administration promotes endometrial regeneration mediated by IGFBP3-dependent OPN proteolytic cleavage in thin endometrium

Adequate endometrial growth is a critical factor for successful embryo implantation and pregnancy maintenance. We previously reported the efficacy of intrauterine administration of botulinum toxin A (BoTA) in improving the endometrial angiogenesis and the rates of embryo implantation. Here, we further evaluated its potent therapeutic effects on the uterine structural and functional repair and elucidated underlying molecular regulatory mechanisms. This study demonstrated that a murine model of thin endometrium was successfully established by displaying dramatically decreased endometrial thickness and the rates of embryo implantation compared to normal endometrium. Interestingly, the expressions of insulin-like growth factor binding protein-3 (IGFBP3) and an active 35 kDa-form of osteopontin (OPN) were significantly reduced in thin endometrium, which were almost fully restored by intrauterine BoTA administration. Neutralization of BoTA-induced IGFBP3 subsequently suppressed proteolytic cleavage of OPN, exhibiting un-recovered endometrial thickness even in the presence of BoTA administration, suggesting that BoTA-induced endometrial regeneration might be mediated by IGFBP3-dependent OPN proteolytic cleavage. Our findings suggest that intrauterine BoTA administration improves the endometrial environment in our murine model with thin endometrium by increasing endometrial receptivity and angiogenesis in a manner dependent on the regulatory effect of IGFBP3 on OPN proteolytic cleavage, proposing BoTA as an efficient therapeutic strategy for the patients with thin endometrium.

Synergistically Promoting Bone Regeneration by Icariin-Incorporated Porous Microcarriers and Decellularized Extracellular Matrix Derived From Bone Marrow Mesenchymal Stem Cells

Multifunctionality has becoming essential for bone tissue engineering materials, such as drug release. In this study, icariin (ICA)-incorporated poly(glycolide-co-caprolactone) (PGCL) porous microcarriers were fabricated and then coated with decellularized extracellular matrix (dECM) which was derived from bone marrow mesenchymal stem cells (BMSC). The porous structure was generated due to the soluble gelatin within the microcarriers. The initial released ICA in microcarriers regulated osteogenic ECM production by BMSCs during ECM formation. The dECM could further synergistically enhance the migration and osteogenic differentiation of BMSCs together with ICA as indicated by the transwell migration assay, ALP and ARS staining, as well as gene and protein expression. Furthermore, in vivo results also showed that dECM and ICA exhibited excellent synergistic effects in repairing rat calvarial defects. These findings suggest that the porous microcarriers loaded with ICA and dECM coatings have great potential in the field of bone tissue engineering.

Integrative Single-Cell RNA-Seq and ATAC-Seq Analysis of Mesenchymal Stem/Stromal Cells Derived from Human Placenta

Mesenchymal stem/stromal cells derived from placenta (PMSCs) are an attractive source for regenerative medicine because of their multidifferentiation potential and immunomodulatory capabilities. However, the cellular and molecular heterogeneity of PMSCs has not been fully characterized. Here, we applied single-cell RNA sequencing (scRNA-seq) and assay for transposase-accessible chromatin sequencing (scATAC-seq) techniques to cultured PMSCs from human full-term placenta. Based on the inferred characteristics of cell clusters, we identify several distinct subsets of PMSCs with specific characteristics, including immunomodulatory-potential and highly proliferative cell states. Furthermore, integrative analysis of gene expression and chromatin accessibility showed a clearer chromatin accessibility signature than those at the transcriptional level on immunomodulatory-related genes. Cell cycle gene-related heterogeneity can be more easily distinguished at the transcriptional than the chromatin accessibility level in PMSCs. We further reveal putative subset-specific cis-regulatory elements regulating the expression of immunomodulatory- and proliferation-related genes in the immunomodulatory-potential and proliferative subpopulations, respectively. Moreover, we infer a novel transcription factor PRDM1, which might play a crucial role in maintaining immunomodulatory capability by activating PRDM1-regulon loop. Collectively, our study first provides a comprehensive and integrative view of the transcriptomic and epigenomic features of PMSCs, which paves the way for a deeper understanding of cellular heterogeneity and offers fundamental biological insight of PMSC subset-based cell therapy.

Insulin growth factor binding protein-3 enhances dental implant osseointegration against methylglyoxal-induced bone deterioration in a rat model

PURPOSE

The aim of this study was to determine the effect of insulin growth factor binding protein-3 (IGFBP-3) on the inhibition of glucose oxidative stress and promotion of bone formation near the implant site in a rat model of methylglyoxal (MGO)-induced bone loss.

METHODS

An in vitro study was performed in MC3T3 E1 cells treated with chitosan gold nanoparticles (Ch-GNPs) conjugated with IGFBP-3 cDNA followed by MGO. An in vivo study was conducted in a rat model induced by MGO administration after the insertion of a dental implant coated with IGFBP-3.

RESULTS

MGO treatment downregulated molecules involved in osteogenic differentiation and bone formation in MC3T3 E1 cells and influenced the bone mineral density and bone volume of the femur and alveolar bone. In contrast, IGFBP-3 inhibited oxidative stress and inflammation and enhanced osteogenesis in MGO-treated MC3T3 E1 cells. In addition, IGFBP-3 promoted bone formation by reducing inflammatory proteins in MGO-administered rats. The application of Ch-GNPs conjugated with IGFBP-3 as a coating of titanium implants enhanced osteogenesis and the osseointegration of dental implants.

CONCLUSIONS

This study demonstrated that IGFBP-3 could be applied as a therapeutic component in dental implants to promote the osseointegration of dental implants in patients with diabetes, which affects MGO levels.

Regeneration enhanced in critical-sized bone defects using bone-specific extracellular matrix protein

Extracellular matrix (ECM) products have the potential to improve cellular attachment and promote tissue-specific development by mimicking the native cellular niche. In this study, the therapeutic efficacy of an ECM substratum produced by bone marrow stem cells (BM-MSCs) to promote bone regeneration in vitro and in vivo were evaluated. Fluorescence-activated cell sorting analysis and phenotypic expression were employed to characterize the in vitro BM-MSC response to bone marrow specific ECM (BM-ECM). BM-ECM encouraged cell proliferation and stemness maintenance. The efficacy of BM-ECM as an adjuvant in promoting bone regeneration was evaluated in an orthotopic, segmental critical-sized bone defect in the rat femur over 8 weeks. The groups evaluated were either untreated (negative control); packed with calcium phosphate granules or granules+BM-ECM free protein and stabilized by collagenous membrane. Bone regeneration in vivo was analyzed using microcomputed tomography and histology. in vivo results demonstrated improvements in mineralization, osteogenesis, and tissue infiltration (114 ± 15% increase) in the BM-ECM complex group from 4 to 8 weeks compared to mineral granules only (45 ± 21% increase). Histological observations suggested direct apposition of early bone after 4 weeks and mineral consolidation after 8 weeks implantation for the group supplemented with BM-ECM. Significant osteoid formation and greater functional bone formation (polar moment of inertia was 71 ± 0.2 mm4 with BM-ECM supplementation compared to 48 ± 0.2 mm4 in untreated defects) validated in vivo indicated support of osteoconductivity and increased defect site cellularity. In conclusion, these results suggest that BM-ECM free protein is potentially a therapeutic supplement for stemness maintenance and sustaining osteogenesis.

Mesenchymal stem cell-derived extracellular matrix (mECM): a bioactive and versatile scaffold for musculoskeletal tissue engineering

Mesenchymal stem cell-derived extracellular matrix (mECM) has received increased attention in the fields of tissue engineering and scaffold-assisted regeneration. mECM exhibits many unique characteristics, such as robust bioactivity, biocompatibility, ease of use, and the potential for autologous tissue engineering. As the use of mECM has increased in musculoskeletal tissue engineering, it should be noted that mECM generated from current methods has inherited insufficiencies, such as low mechanical properties and lack of internal architecture. In this review, we first summarize the development and use of mECM as a scaffold for musculoskeletal tissue regeneration and highlight our current progress on moving this technology toward clinical application. Then we review recent methods to improve the properties of mECM that will overcome current weaknesses. Lastly, we propose future studies that will pave the road for mECM application in regenerating tissues in humans.

Proteomic analysis of extracellular vesicles and conditioned medium from human adipose-derived stem/stromal cells and dermal fibroblasts

Conditioned medium (CM) and extracellular vesicles (EV) from Adipose-derived Stem/stromal cells (ASC) and Dermal fibroblasts (DF) represent promising tools for therapeutic applications. Which one should be preferred is still under debate and no direct comparison of their proteome has been reported yet. Here, we apply quantitative proteomics to explore the protein composition of CM and EV from the two cell types. Data are available via ProteomeXchange (identifier PXD020219). We identified 1977 proteins by LC-MS/MS proteomic analysis. Unsupervised clustering analysis and PCA recognized CM and EV as separate groups. We identified 68 and 201 CM and EV specific factors. CM were enriched in proteins of endoplasmic reticulum, Golgi apparatus and lysosomes, whereas EV contained a large amount of GTPases, ribosome and translation factors. The analysis of ASC and DF secretomes revealed the presence of cell type-specific proteins. ASC-CM and -EV carried factors involved in ECM organization and immunological regulation, respectively. Conversely, DF-CM and -EV were enriched in epithelium development associated factors and -EV in Wnt signaling factors. In conclusion, this analysis provides evidence of a different protein composition between CM and EV and of the presence of cell type-specific bioactive mediators suggesting their specific future use as advanced therapy medicinal products. SIGNIFICANCE: The use of cell secretome presents several advantages over cell therapy such as the lower risks associated to the administration step and the avoidance of any potential risk of malignant transformation. The main secretome preparations consist in concentrated conditioned medium (CM) and extracellular vesicles (EV). Both of them showed well-documented therapeutic potentials. However, it is still not clear in which case it should be better to use one preparation over the other and an exhaustive comparison between their proteome has not been performed yet. The choice of the cell source is another relevant aspect that still needs to be addressed. In order to shed light on these questions we explored the protein composition of CM and EV obtained from Adipose-derived Stem/stromal Cells (ASC) and Dermal Fibroblasts (DF), by a comprehensive quantitative proteomics approach. The analysis showed a clear distinction between CM and EV proteome. CM were enriched in proteins of endoplasmic reticulum, Golgi apparatus and lysosomes, whereas EV contained a large amount of GTPases, ribosome and translation-related factors. Furthermore, the analysis of ASC and DF secretomes revealed specific biological processes for the different cell products. ASC secretome presented factors involved in ECM organization (hyaluronan and glycosaminoglycan metabolism) and immunological regulation (e.g. macrophage and IkB/NFkB signaling regulation), respectively. On the other hand, DF-CM and -EV were both enriched in epithelium development associated factors, whilst DF-CM in proteins involved in cellular processes regulation and -EV in Wnt signaling factors. In conclusion, our study shed a light on the different protein composition of CM and EV of two promising cell types, spanning from basic processes involved in secretion to specific pathways supporting their therapeutic potential and their possible future use as advanced therapy medicinal products.

A selected small molecule prevents inflammatory osteolysis through restraining osteoclastogenesis by modulating PTEN activity

BACKGROUND

Inflammatory osteolysis is a severe infectious bone disorder that occurs during orthopaedic surgery and is caused by disruptions in the dynamic balance of bone matrix homeostasis, which makes this condition a burden on surgical procedures. Developing novel therapeutic drugs about inhibiting excessive osteoclastogenesis acts as an efficient approach to preventing inflammatory bone destruction.

METHODS

To study this, we explored the potential effects and mechanisms of compound 17 on inflammatory osteolysis in vitro. Meanwhile, a lipopolysaccharide (LPS)-induced calvarial osteolysis mouse model was used to evaluate the protective effect of compound 17 on inflammatory bone destruction in vivo.

RESULTS

In our study, we found that compound 17 could inhibit osteoclast (OC) differentiation and bone resorption during RANKL and LPS stimulation in a time- and dose-dependent manner, while compounds 5 and 13 did not have the same effects. Mechanistically, compound 17 promoted phosphatase and tensin homologue (PTEN) activity by reducing PTEN ubiquitination, thereby restraining the RANKL-induced NF-κB pathway, resulting in the inhibition of the expression of osteoclastogenesis-related genes and the formation of the NLRP3 inflammasome. Additionally, we also investigated whether compound 17 could negatively modulate macrophage polarization and repolarization due to its anti-inflammatory effects. Moreover, compound 17 also plays an important role in osteoblast differentiation and mineralization. In vivo experiments showed that compound 17 could effectively protect mice from LPS-induced inflammatory bone destruction by inhibiting osteoclastogenesis and inflammation.

CONCLUSIONS

Taken together, these results show that compound 17 might play protective role in inflammatory bone destruction through inhibiting osteoclastogenesis and inflammation. These findings imply a possible role of compound 17 in inflammatory osteolysis-related diseases.

Remodeling of aligned fibrous extracellular matrix by encapsulated cells under mechanical stretching

Extracellular matrix (ECM) remodeling is essential for the development and functions of connective tissues (e.g., heart, muscle and the periodontal ligament), and entails the highly anisotropic response of cells and their organized ECM molecules to mechanical stimulation. However, the nature of how cells remodel their surrounding ECM under mechanical stimulation remains elusive. Here, we encapsulated human periodontal ligament stem cells (hPDLSCs) within an aligned rat collagen scaffold labeled with fluorescein isothiocyanate (FITC) and applied mechanical stimulation on the scaffold using magnetic stretching. Through tracking the FITC-labeled rat collagen scaffold and the newly secreted human type I collagen, we studied the effect of magnetic stretching on the mechanism of aligned ECM remodeling by the encapsulated cells. We found that the aligned topography combined with magnetic stretching could significantly promote initial ECM degradation and new ECM secretion: expression of matrix metalloproteinases 1 and 9 is increased markedly, and the elastic modulus of the stretched scaffold (75 kPa) is significantly higher than that of the random scaffold (50 kPa). The data support a model whereby the cells remodel their surrounding ECM under continuous stretching through degradation and then secretion of new ECM to integrate with the aligned ECM and maintain tissue function. Our study offers a valuable basis for future optimized design of biomaterial scaffolds for clinical translation. STATEMENT OF SIGNIFICANCE: Extracellular matrix (ECM) remodeling is essential for the development and functions of connective tissues. However, the nature of how cells remodel their surrounding aligned ECM under mechanical stimulation remains elusive. Herein, we developed a method to reveal the remodeling of aligned rat collagen scaffold by the encapsulated human periodontal ligament stem cells (hPDLSCs) using fluorescence imaging. We found that the aligned topography combined with magnetic stretching could significantly promote initial ECM degradation and new ECM secretion: the expression of matrix metalloproteinase 1 and 9 are significantly higher, and the elastic modulus increases from 50 kPa to 75 kPa as compared to the random collagen scaffold encapsulating hPDLSCs. Our study holds great potential in optimization of bio-scaffold design for clinical translation.

Modification of PLGA Scaffold by MSC-Derived Extracellular Matrix Combats Macrophage Inflammation to Initiate Bone Regeneration via TGF-β-Induced Protein

The immunologic response toward chronic inflammation or bone regeneration via the accumulation of M1 or M2 macrophages after injury could determine the fate of biomaterial. Human umbilical cord mesenchymal stem cells (hUCMSCs) have a pivotal immunomodulatory property on directing macrophage behaviors. Herein, for the first time, 3D-printed poly(lactide-co-glycolide) (PLGA) scaffolds modified with hUCMSC-derived extracellular matrix (PLGA-ECM) are prepared by a facile tissue engineering technique with physical decellularization and 2.44 ± 0.29 mg cm^-3 proteins immobilized on the PLGA-ECM contain multiple soluble cytokines with a sustainable release profile. The PLGA-ECM not only attenuates the foreign body response, but also improves bone regeneration by increasing the accumulation of M2 macrophages in an improved heterotopic transplantation model of SCID mice. Furthermore, the PLGA-ECM scaffolds with the knockdown of transforming growth factor-β-induced protein (TGFβI/βig-H3) demonstrate that M2 macrophage accumulation improved by the PLGA-ECM could be attributed to increasing the migration of M2 macrophages and the repolarization of M1 macrophages to M2 phenotype, which are mediated by multiple integrin signaling pathways involving in integrin β7, integrin α9, and integrin β1 in a TGFβI-dependent manner. This study presents an effective surface modification strategy of polymeric scaffolds to initiate tissue regeneration and combat inflammatory response by increasing M2 macrophage accumulation.

Current and future uses of skeletal stem cells for bone regeneration

The postnatal skeleton undergoes growth, modeling, and remodeling. The human skeleton is a composite of diverse tissue types, including bone, cartilage, fat, fibroblasts, nerves, blood vessels, and hematopoietic cells. Fracture nonunion and bone defects are among the most challenging clinical problems in orthopedic trauma. The incidence of nonunion or bone defects following fractures is increasing. Stem and progenitor cells mediate homeostasis and regeneration in postnatal tissue, including bone tissue. As multipotent stem cells, skeletal stem cells (SSCs) have a strong effect on the growth, differentiation, and repair of bone regeneration. In recent years, a number of important studies have characterized the hierarchy, differential potential, and bone formation of SSCs. Here, we describe studies on and applications of SSCs and/or mesenchymal stem cells for bone regeneration.

Paracrine senescence of human endometrial mesenchymal stem cells: a role for the insulin-like growth factor binding protein 3

Stress-induced premature cell senescence is well recognized to be accompanied by emerging the senescence-associated secretory phenotype (SASP). Secreted SASP factors can promote the senescence of normal neighboring cells through autocrine/paracrine pathways and regulate the senescence response, as well. Regarding human endometrium-derived mesenchymal stem cells (MESCs), the SASP regulation mechanisms as well as paracrine activity of senescent cells have not been studied yet. Here, we examined the role of insulin-like growth factor binding protein 3 (IGFBP3) in the paracrine senescence induction in young MESCs. The H₂O₂-induced premature senescence of MESCs led to increased IGFBP3 in conditioned media (CM). The inhibitory analysis of both MAPK and PI3K signaling pathways showed that IGFBP3 releasing from senescent cells is mainly regulated by PI3K/Akt pathway activity. IGFBP3 appears to be an important senescence-mediating factor as its immunodepletion from the senescent CM weakened the pro-senescent effect of CM on young MESCs and promoted their growth. In contrast, young MESCs acquired the senescence phenotype in response to simultaneous addition of recombinant IGFBP3 (rIGFBP3). The mechanism of extracellular IGFBP3 internalization was also revealed. The present study is the first to demonstrate a significant role of extracellular IGFBP3 in paracrine senescence induction of young MESCs.

In Vitro Evaluation of a Novel Osteo-Inductive Scaffold for Osteogenic Differentiation of Bone-Marrow Mesenchymal Stem Cells

BACKGROUND

Demineralized bone matrices (DBMs) were demonstrated to be a promising candidate for bone regeneration by previous studies. However, the limited osteoinductivity of DBMs was insufficient for a better repairing of bone defect. Osteoblasts (OBs), the major cellular component of bone tissues, play an important role in the formation of new bone. The extracellular matrix (ECM) of OB is one of the main components of bone formation niche.

OBJECTIVE

To combine the DBMs with the ECM of OBs to construct a novel scaffold that could be used for bone reconstruction.

METHODS

In this study, OBs were cultured on the surface of DBMs for 10 days and removed by Triton X-100 and ammonium hydroxide to prepare the OBs-ECM-DBMs (OEDBMs). A series of material features such as residues of OBs and ECM, cytotoxity, and osteoinductive capability of OEDBMs were evaluated.

RESULTS

Low cell residues and low content of DNA were observed in OEDBMs. Compared with DBMs, OEDBMs possessed more bone tissues organic matrix proteins, such as osteocalcin, osteopontin, and collagen I. Rat bone marrow mesenchymal stem cells (rBMSCs) presented a good viability when cultured on both 2 materials. The significant upregulations of osteogenic genes and proteins of rBMSCs were observed in OEDBMs group compared with DBMs group.

CONCLUSION

Taken together, these findings suggested that the OB-secreted ECM may be qualified as an ideal modification method for enhancing the performance of engineered bone scaffold.

Exosomes derived from miR-375-overexpressing human adipose mesenchymal stem cells promote bone regeneration

Objectives

The present study aimed to investigate whether exosomes derived from miR‐375‐overexpressing human adipose mesenchymal stem cells (hASCs) could enhance bone regeneration.

Materials and Methods

Exosomes enriched with miR‐375 (Exo [miR‐375]) were generated from hASCs stably overexpressing miR‐375 after lentiviral transfection and identified with transmission electron microscopy, nanosight and western blotting. The construction efficiency of Exo (miR‐375) was evaluated with qRT‐PCR and incubated with human bone marrow mesenchymal stem cells (hBMSCs) to optimize the effective dosage. Then, the osteogenic capability of Exo (miR‐375) was investigated with ALP and ARS assays. Furthermore, dual‐luciferase reporter assay and western blotting were conducted to reveal the underlying mechanism of miR‐375 in osteogenic regulation. Finally, Exo (miR‐375) were embedded with hydrogel and applied to a rat model of calvarial defect, and μ‐CT analysis and histological examination were conducted to evaluate the therapeutic effects of Exo (miR‐375) in bone regeneration.

Results

miR‐375 could be enriched in exosomes by overexpressing in the parent cells. Administration of Exo (miR‐375) at 50 μg/mL improved the osteogenic differentiation of hBMSCs. With miR‐375 absorbed by hBMSCs, insulin‐like growth factor binding protein 3 (IGFBP3) was inhibited by binding to its 3′UTR, and recombinant IGFBP3 protein reduced the osteogenic effects triggered by Exo (miR‐375). After incorporated with hydrogel, Exo (miR‐375) displayed a slow and controlled release, and further in vivo analysis demonstrated that Exo (miR‐375) enhanced the bone regenerative capacity in a rat model of calvarial defect.

Conclusions

Taken together, our study demonstrated that exosomes derived from miR‐375‐overexpressing hASCs promoted bone regeneration.

IGF2 enhanced the osteo-/dentinogenic and neurogenic differentiation potentials of stem cells from apical papilla

OBJECTIVES

In dental tissue engineering, niche is important for maintaining stem cell function and regenerating the dental tissues. However, there is limited knowledge for the growth factors in niche to maintain the function of stem cells. In this study, we investigated the effect of IGF2, a growth factor in stem cells from apical papilla (SCAPs) niche, on differentiation and proliferation potentials of SCAPs.

MATERIALS AND METHODS

Recombinant human IGF2 protein (rhIGF2) was used. Cell counting kit-8 assay, Carboxyfluorescein succinimidyl ester assay, alkaline phosphatase (ALP) activity, Alizarin Red staining, quantitative calcium analysis, immunofluorescence staining and real-time RT-PCR were performed to investigate the cell proliferation and differentiation potentials of SCAPs. And proteomic analysis was used to identify the differential secreted proteins.

RESULTS

By ALP activity assay, we found that 5 ng/mL rhIGF2 might be the optimal concentration for treatment. Then, Alizarin Red staining, quantitative calcium analysis and osteogenesis-related gene expression results showed that 5 ng/mL rhIGF2 could enhance the osteo-/dentinogenic differentiation potentials in SCAPs. Immunofluorescence staining and real-time RT-PCR results showed that neurogenic markers were significantly induced by 5 ng/mL rhIGF2 in SCAPs. Then, CCK-8 assay and CFSE assay results showed that 5 ng/mL rhIGF2 could enhance the cell proliferation in SCAPs. Furthermore, proteomic analysis showed that IGF2 could induce some secreted proteins which function related to the osteogenesis, neurogenesis and cell proliferation.

CONCLUSIONS

Our results identified that IGF2 might be the potential mediator in niche to promote SCAP function and dental tissue regeneration.

IGFBP3 deposited in the human umbilical cord mesenchymal stem cell-secreted extracellular matrix promotes bone formation

The extracellular matrix (ECM) contains rich biological cues for cell recruitment, proliferationm, and even differentiation. The osteoinductive potential of scaffolds could be enhanced through human bone marrow mesenchymal stem cell (hBMSC) directly depositing ECM on surface of scaffolds. However, the role and mechanism of human umbilical cord mesenchymal stem cells (hUCMSC)-secreted ECM in bone formation remain unknown. We tested the osteoinductive properties of a hUCMSC-secreted ECM construct (hUCMSC-ECM) in a large femur defect of a severe combined immunodeficiency (SCID) mouse model. The hUCMSC-ECM improved the colonization of endogenous MSCs and bone regeneration, similar to the hUCMSC-seeded scaffold and superior to the scaffold substrate. Besides, the hUCMSC-ECM enhanced the promigratory molecular expressions of the homing cells, including CCR2 and TβRI. Furthermore, the hUCMSC-ECM increased the number of migrated MSCs by nearly 3.3 ± 0.1-fold, relative to the scaffold substrate. As the most abundant cytokine deposited in the hUCMSC-ECM, insulin-like growth factor binding protein 3 (IGFBP3) promoted hBMSC migration in the TβRI/II- and CCR2-dependent mechanisms. The hUCMSC-ECM integrating shRNA-mediated silencing of Igfbp3 that down-regulated IGFBP3 expression by approximately 60%, reduced the number of migrated hBMSCs by 47%. In vivo, the hUCMSC-ECM recruited 10-fold more endogenous MSCs to initiate bone formation compared to the scaffold substrate. The knock-down of Igfbp3 in the hUCMSC-ECM inhibited nearly 60% of MSC homing and bone regeneration capacity. This research demonstrates that IGFBP3 is an important MSC homing molecule and the therapeutic potential of hUCMSC-ECM in bone regeneration is enhanced by improving MSC homing in an IGFBP3-dependent mechanism.

ISL1 overexpression enhances the survival of transplanted human mesenchymal stem cells in a murine myocardial infarction model

BACKGROUND

The LIM-homeobox transcription factor islet-1 (ISL1) has been proposed as a marker for cardiovascular progenitor cells. This study investigated whether forced expression of ISL1 in human mesenchymal stem cells (hMSCs) improves myocardial infarction (MI) treatment outcomes.

METHODS

The lentiviral vector containing the human elongation factor 1α promoter, which drives the expression of ISL1 (EF1α-ISL1), was constructed using the Multisite Gateway System and used to transduce hMSCs. Flow cytometry, immunofluorescence, Western blotting, TUNEL assay, and RNA sequencing were performed to evaluate the function of ISL1-overexpressing hMSCs (ISL1-hMSCs).

RESULTS

The in vivo results showed that transplantation of ISL1-hMSCs improved cardiac function in a rat model of MI. Left ventricle ejection fraction and fractional shortening were greater in post-MI hearts after 4 weeks of treatment with ISL1-hMSCs compared with control hMSCs or phosphate-buffered saline. We also found that ISL1 overexpression increased angiogenesis and decreased apoptosis and inflammation. The greater potential of ISL1-hMSCs may be attributable to an increased number of surviving cells after transplantation. Conditioned medium from ISL1-hMSCs decreased the apoptotic effect of H₂O₂ on the cardiomyocyte cell line H9c2. To clarify the molecular basis of this finding, we employed RNA sequencing to compare the apoptotic-related gene expression profiles of control hMSCs and ISL1-hMSCs. The results showed that insulin-like growth factor binding protein 3 (IGFBP3) was the only gene in ISL1-hMSCs with a RPKM value higher than 100 and that the difference fold-change between ISL1-hMSCs and control hMSCs was greater than 3, suggesting that IGFBP3 might play an important role in the anti-apoptosis effect of ISL1-hMSCs through paracrine effects. Furthermore, the expression of IGFBP3 in the conditioned medium from ISL1-hMSCs was almost fourfold greater than that in conditioned medium from control hMSCs. Moreover, the IGFBP3 neutralization antibody reversed the apoptotic effect of ISL1-hMSCs-CM.

CONCLUSIONS

These results suggest that overexpression of ISL1 in hMSCs promotes cell survival in a model of MI and enhances their paracrine function to protect cardiomyocytes, which may be mediated through IGFBP3. ISL1 overexpression in hMSCs may represent a novel strategy for enhancing the effectiveness of stem cell therapy after MI.