Efficient Differentiation of Bone Marrow Mesenchymal Stem Cells into Endothelial Cells in Vitro

Neovascularization: The Main Mechanism of MSCs in Ischemic Heart Disease Therapy

Mesenchymal stem cell (MSC) transplantation after myocardial infarction (MI) has been shown to effectively limit the infarct area in numerous clinical and preclinical studies. However, the primary mechanism associated with this activity in MSC transplantation therapy remains unclear. Blood supply is fundamental for the survival of myocardial tissue, and the formation of an efficient vascular network is a prerequisite for blood flow. The paracrine function of MSCs, which is throughout the neovascularization process, including MSC mobilization, migration, homing, adhesion and retention, regulates angiogenesis and vasculogenesis through existing endothelial cells (ECs) and endothelial progenitor cells (EPCs). Additionally, MSCs have the ability to differentiate into multiple cell lineages and can be mobilized and migrate to ischemic tissue to differentiate into ECs, pericytes and smooth muscle cells in some degree, which are necessary components of blood vessels. These characteristics of MSCs support the view that these cells improve ischemic myocardium through angiogenesis and vasculogenesis. In this review, the results of recent clinical and preclinical studies are discussed to illustrate the processes and mechanisms of neovascularization in ischemic heart disease.

Biophysical phenotyping of mesenchymal stem cells along the osteogenic differentiation pathway

Mesenchymal stem cells represent an important resource, for bone regenerative medicine and therapeutic applications. This review focuses on new advancements and biophysical tools which exploit different physical and chemical markers of mesenchymal stem cell populations, to finely characterize phenotype changes along their osteogenic differentiation process. Special attention is paid to recently developed label-free methods, which allow monitoring cell populations with minimal invasiveness. Among them, quantitative phase imaging, suitable for single-cell morphometric analysis, and nanoindentation, functional to cellular biomechanics investigation. Moreover, the pool of ion channels expressed in cells during differentiation is discussed, with particular interest for calcium homoeostasis.Altogether, a biophysical perspective of osteogenesis is proposed, offering a valuable tool for the assessment of the cell stage, but also suggesting potential physiological links between apparently independent phenomena.

Human endometrial perivascular stem cells exhibit a limited potential to regenerate endometrium after xenotransplantation

STUDY QUESTION

What are the localization, characteristics and potential for tissue regeneration of two perivascular stem cells, namely CD34+ adventitial cells and CD146+ pericytes, in human endometrium?

SUMMARY ANSWER

Human endometrial CD34+ adventitial cells (located in the outermost layer of blood vessels and mainly in the basal layer) and CD146+ pericytes showed mesenchymal stem cell (MSC) phenotypes in in vitro culture, but presented limited potential to regenerate endometrium.

WHAT IS KNOWN ALREADY

Periodic endometrial regeneration is considered to be maintained by MSCs. Blood vessel wall, regarded as stem cell niche, harbors a large reserve of progenitor cells that may be integral to the origin of MSCs. However, a lack of validated markers has hampered the isolation of putative endometrial MSCs. Currently, CD146+ pericytes and Sushi Domain Containing 2 (SUSD2) positive cells have been identified in the endometrial perivascular region as sharing MSCs characteristics.

STUDY DESIGN, SIZE, DURATION

The locations of adventitial cells and pericytes in the human endometrium were identified by immunofluorescence staining (n = 4). After CD34+CD146-CD45-CD56-CD144- adventitial cells and CD146+CD34-CD45-CD56-CD144- pericytes were isolated from the endometrium of normal women (n = 6) by fluorescence-activated cell sorting, their characteristics were investigated in culture. Adventitial cells and pericytes were induced to differentiate, respectively, into vascular endothelial-like cells or endometrial stromal-like cells in vitro, with their potential explored by in vivo xenotransplantation (n = 2 in each group) and eutopic transplantation (n = 2 in each group).

PARTICIPANTS/MATERIALS, SETTING, METHODS

CD34+ adventitial cells and CD146+ pericytes were cultured in the inducing medium to differentiate into endothelial-like cells in vitro, and then analyzed for CD31, von Willebrand factor immunofluorescent staining and tube formation. They were also cultured to differentiate into endometrial stromal cells in vitro, with the expression of vimentin and CD13 being detected by western blot before and after induction, and the expression of prolactin and insulin-like growth factor-binding protein 1 being determined as well. Single dispersed CD34+ adventitial cells and CD146+ pericytes were respectively transplanted under the kidney capsule of NOG mice to investigate their differentiation potential in vivo. A eutopic transplantation model was constructed by grafting recellularized uterine matrix loaded up with CM-Dil labeled adventitial cells or pericytes into the injury region of nude rat's uterus.

MAIN RESULTS AND THE ROLE OF CHANCE

CD34+ adventitial cells were mainly located at the outmost layer of endometrial large vessels, while CD146+ pericytes were found surrounding the inner endothelial cells of microvessels. A small proportion of CD34+ adventitial cells expressed SUSD2. The number of adventitial cells was ∼40 times higher than that of pericytes in the endometrium. Both adventitial cells and pericytes showed MSC phenotypes after in vitro culture. After in vitro induction into endometrial endothelial-like cells and stromal-like cells, adventitial cells showed higher plasticity than pericytes and a closer correlation with stromal-like cells. In the mouse xenotransplantation model, vimentin+ cells, CD31+ endothelial-like cells and CD146+ pericyte-like cells could be observed after adventitial cells were transplanted. CM-Dil-labeled adventitial cells or pericytes could survive in the immunocompromised nude rats after eutopic transplantation, and vimentin+ cells were detected. In addition, CM-Dil-labeled adventitial cells or pericytes did not express α-smooth muscle actin or E-cadherin after transplantation.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

CD34 was chosen as a novel marker to isolate adventitial cells from human endometrium according to previous literature. The association of endometrial CD34+ adventitial cells and SUSD2+ MSCs should be further investigated.

WIDER IMPLICATIONS OF THE FINDINGS

The decellularized uterine matrix model might be useful in endometrial stem cell therapy.

STUDY FUNDING/COMPETING INTEREST(S)

L.D. is supported by grants from National Key Research and Development Program of China (2018YFC1004700), Nature Science Foundation of China (81871128, 81571391) and Nanjing Medical Science Development Project (ZKX16042). H.S. is supported by a grant from Jiangsu Province Social Development Project (BE2018602). X.Z. was supported by grants from the Postgraduate Innovative Project of Jiangsu Province (KYCX19-1177). The authors declare no conflict of interest.

Construction of tissue engineering bone with the co‑culture system of ADSCs and VECs on partially deproteinized biologic bone in vitro: A preliminary study

Scaffold‑based bone tissue engineering has therapeutic potential in the regeneration of osseous defects. The present study aimed to explore the adhesion and cell viability of a co‑culture system composed of vascular endothelial cells PI‑/Annexin V+ represents early apoptotic cells, and PI+/Annexin V+ represents late apoptotic cells (VECs) and adipose‑derived stem cells (ADSCs) on partially deproteinized biologic bone (PDPBB) in vitro, and determine the optimum time period for maximum cell viability that could possibly be used for standardizing the scaffold transplant into the in vivo system. VECs and ADSCs were isolated from pregnant Sprague‑Dawley rats and confirmed by immunostaining with von Willebrand factor and CD90, respectively. PDPBB was prepared using standardized protocols involving coating partially deproteinized bone with fibronectin. PDPBB was incubated in a mono‑culture with VECs or ADSCs, or in a co‑culture with both of these cells at a ratio of 1:1. An MTT assay was used to assess the adhesion and cell viability of VECs and ADSCs on PDPBB in the three different cultures. Scanning electron microscopy was used to observe the adhesion, cell viability and morphology of the different types of cells on PDPBB. It was observed that the absorbance of each group increased gradually and peaked on the 10th day; the highest absorbance was found for the co‑cultured cells group. The difference of cell viability between each cell group was statistically significant. On the 10th day, in the co‑cultured cells group, several cells adhered on the PDPBB material and a nest‑like distribution morphology was observed. Therefore, the adhesion and cell viability of the co‑cultured cells was higher compared with the mono‑cultures of VECs or ADSCs. As cell viability was highest on the 10th day, this could be the optimal length of time for incubation and therefore could be used for in vivo experiments.

Intrinsic Angiogenic Potential and Migration Capacity of Human Mesenchymal Stromal Cells Derived from Menstrual Blood and Bone Marrow

Several therapies are being developed to increase blood circulation in ischemic tissues. Despite bone marrow-derived mesenchymal stromal cells (bmMSC) are still the most studied, an interesting and less invasive MSC source is the menstrual blood, which has shown great angiogenic capabilities. Therefore, the aim of this study was to evaluate the angiogenic properties of menstrual blood-derived mesenchymal stromal cells (mbMSC) in vitro and in vivo and compared to bmMSC. MSC’s intrinsic angiogenic capacity was assessed by sprouting and migration assays. mbMSC presented higher invasion and longer sprouts in 3D culture. Additionally, both MSC-spheroids showed cells expressing CD31. mbMSC and bmMSC were able to migrate after scratch wound in vitro, nonetheless, only mbMSC demonstrated ability to engraft in the chick embryo, migrating to perivascular, perineural, and chondrogenic regions. In order to study the paracrine effects, mbMSC and bmMSC conditioned mediums were capable of stimulating HUVEC’s tube-like formation and migration. Both cells expressed VEGF-A and FGF2. Meanwhile, PDGF-B was expressed exclusively in mbMSC. Our results indicated that mbMSC and bmMSC presented a promising angiogenic potential. However, mbMSC seems to have additional advantages since it can be obtained by non-invasive procedure and expresses PDGF-B, an important molecule for vascular formation and remodeling.

The application of bone marrow mesenchymal stem cells and biomaterials in skeletal muscle regeneration

Skeletal muscle injuries have bothered doctors and caused great burdens to the public medical insurance system for a long time. Once injured, skeletal muscles usually go through the processes of inflammation, repairing and remodeling. If repairing and remodeling stages are out of balance, scars will be formed to replace injured skeletal muscles. At present, clinicians usually use conventional methods to restore the injured skeletal muscles, such as flap transplantation. However, flap transplantation sometimes needs to sacrifice healthy autologous tissues and will bring extra harm to patients. In recent years, stem cells-based tissue engineering provides us new treatment ideas for skeletal muscle injuries. Stem cells are cells with multiple differentiation potential and have ability to differentiate into adult cells under special condition. Skeletal muscle tissues also have stem cells, called satellite cells, but they are in small amount and new muscle fibers that derived from them may not be enough to replace injured fibers. Bone marrow mesenchymal stem cells (BM-MSCs) could promote musculoskeletal tissue regeneration and activate the myogenic differentiation of satellite cells. Biomaterial is another important factor to promote tissue regeneration and greatly enhance physiological activities of stem cells in vivo. The combined use of stem cells and biomaterials will gradually become a mainstream to restore injured skeletal muscles in the future. This review article mainly focuses on the review of research about the application of BM-MSCs and several major biomaterials in skeletal muscle regeneration over the past decades.

De novo Vessel Formation Through Cross-Talk of Blood-Derived Cells and Mesenchymal Stromal Cells in the Absence of Pre-existing Vascular Structures

BACKGROUND

The generation of functional blood vessels remains a key challenge for regenerative medicine. Optimized in vitro culture set-ups mimicking the in vivo perivascular niche environment during tissue repair may provide information about the biological function and contribution of progenitor cells to postnatal vasculogenesis, thereby enhancing their therapeutic potential.

AIM

We established a fibrin-based xeno-free human 3D in vitro vascular niche model to study the interaction of mesenchymal stromal cells (MSC) with peripheral blood mononuclear cells (PBMC) including circulating progenitor cells in the absence of endothelial cells (EC), and to investigate the contribution of this cross-talk to neo-vessel formation.

MATERIALS AND METHODS

Bone marrow-derived MSC were co-cultured with whole PBMC, enriched monocytes (Mo), enriched T cells, and Mo together with T cells, respectively, obtained from leukocyte reduction chambers generated during the process of single-donor platelet apheresis. Cells were embedded in 3D fibrin matrices, using exclusively human-derived culture components without external growth factors. Cytokine secretion was analyzed in supernatants of 3D cultures by cytokine array, vascular endothelial growth factor (VEGF) secretion was quantified by ELISA. Cellular and structural re-arrangements were characterized by immunofluorescence and confocal laser-scanning microscopy of topographically intact 3D fibrin gels.

RESULTS

3D co-cultures of MSC with PBMC, and enriched Mo together with enriched T cells, respectively, generated, within 2 weeks, complex CD31+/CD34+ vascular structures, surrounded by basement membrane collagen type-IV+ cells and matrix, in association with increased VEGF secretion. PBMC contained CD31+CD34+CD45dimCD14- progenitor-type cells, and EC of neo-vessels were PBMC-derived. Vascular structures showed intraluminal CD45+ cells that underwent apoptosis thereby creating a lumen. Cross-talk of MSC with enriched Mo provided a pro-angiogenic paracrine environment. MSC co-cultured with enriched T cells formed "cell-in-cell" structures generated through internalization of T cells by CD31+CD45 dim⁣/ - cells. No vascular structures were detected in co-cultures of MSC with either Mo or T cells.

CONCLUSION

Our xeno-free 3D in vitro vascular niche model demonstrates that a complex synergistic network of cellular, extracellular and paracrine cross-talk can contribute to de novo vascular development through self-organization via co-operation of immune cells with blood-derived progenitor cells and MSC, and thereby may open a new perspective for advanced vascular tissue engineering in regenerative medicine.

Mesenchymal Stem Cell-Derived Exosomes: Hope for Spinal Cord Injury Repair

Spinal cord injury (SCI) is a devastating medical condition with profound social and economic impacts. Although research is ongoing, current treatment options are limited and do little to restore functionality. However, recent studies suggest that mesenchymal stem cell-derived exosomes (MSC-exosomes) may hold the key to exciting new treatment options for SCI patients. MSCs are self-renewing multipotent stem cells with multi-directional differentiation and can secrete a large number of exosomes (vesicles secreted into the extracellular environment through endocytosis, called MSC-exosomes). These MSC-exosomes play a critical role in repairing SCI through promoting angiogenesis and axonal growth, regulating inflammation and the immune response, inhibiting apoptosis, and maintaining the integrity of the blood-spinal cord barrier. Furthermore, they can be utilized to transport genetic material or drugs to target cells, and their relatively small size makes them able to permeate the blood-brain barrier. In this review, we summarize recent advances in MSC-exosome themed SCI treatments and cell-free therapies to better understand this newly emerging methodology.

Mesenchymal Stem Cells as a Promising Cell Source for Integration in Novel In Vitro Models

The human-relevance of an in vitro model is dependent on two main factors-(i) an appropriate human cell source and (ii) a modeling platform that recapitulates human in vivo conditions. Recent years have brought substantial advancements in both these aspects. In particular, mesenchymal stem cells (MSCs) have emerged as a promising cell source, as these cells can differentiate into multiple cell types, yet do not raise the ethical and practical concerns associated with other types of stem cells. In turn, advanced bioengineered in vitro models such as microfluidics, Organs-on-a-Chip, scaffolds, bioprinting and organoids are bringing researchers ever closer to mimicking complex in vivo environments, thereby overcoming some of the limitations of traditional 2D cell cultures. This review covers each of these advancements separately and discusses how the integration of MSCs into novel in vitro platforms may contribute enormously to clinical and fundamental research.

Mesenchymal Stem Cell Therapy and Alzheimer's Disease: Current Status and Future Perspectives

Alzheimer's disease (AD) is the most common progressive neurodegenerative disease worldwide, but its cause remains unclear. Although a few drugs can provide temporary and partial relief of symptoms in some patients, no curative treatment is available. Therefore, attention has been focused on research using stem cells to treat AD. Among stem cells, mesenchymal stem cells (MSCs) have been used to treat the related pathologies in animal models of AD, and other neurodegenerative disease. This review describes latest research trends on the use of MSC-based therapies in AD and its action of mechanism. MSCs have several beneficial effects. They would be specified as the reduction of neuroinflammation, the elimination of amyloid-β, neurofibrillary tangles, and abnormal protein degradation, the promotion of autophagy-associated and blood-brain barrier recoveries, the upregulation of acetylcholine levels, improved cognition, and the recovery of mitochondrial transport. Therefore, this review describes the latest research trends in MSC-based therapy for AD by demonstrating the importance of MSC-based therapy and understanding of its mechanisms in AD and discusses the limitations and perspectives of stem cell therapy in AD.

Bone marrow mesenchymal stem cell-derived endothelial cells increase capillary density and accelerate angiogenesis in mouse hindlimb ischemia model

Background

Mesenchymal stem cells (MSCs) can improve limb perfusion and increase vessel density in a murine model of hindlimb ischemia. But low engraftment rate of those cells limited their therapeutic effect. Endothelial cells (ECs) play an important role in neovascularization. And MSCs can differentiate into ECs in vitro. The aim of this study is to investigate if EC differentiation of MSCs in vitro before transplantation is effective in improving therapeutic outcomes in the treatment of ischemic disease in a murine ischemia animal model.

Methods

MSCs were isolated from the bone marrow of EGFP-transgenic mice by density gradient centrifugation. The identity of the MSCs was determined by their cluster of differentiation (CD) marker profile by flow cytometry. Inducing medium containing a few cytokines was applied to induce the MSCs to differentiate into ECs. Endothelial differentiation was quantitatively evaluated using flow cytometry, quantitative real-time PCR (qRT-PCR), immunofluorescence, Matrigel tube formation assay, and Dil-labeled acetylated low-density lipoprotein uptake assay. Mouse hindlimb ischemia model was made by excision of the femoral artery. Uninduced EGFP+ MSCs, induced EGFP+ MSCs, and PBS were intramuscularly injected into the gastrocnemius following ischemia no later than 24 h after operation. Restoration of blood flow and muscle function was evaluated by laser Doppler perfusion imaging. Immunofluorescence was conducted to evaluate the engraftment of transplanted MSCs. Histological analysis was performed to evaluate blood vessel formation.

Results

Induced EGFP+ MSCs expressed endothelial markers and exhibited tube formation capacity. Mice in the induced EGFP+ MSCs group had a better blood perfusion recovery, enhanced vessel densities, higher engraftment, and improved function of the ischemic limb than those in the uninduced EGFP+ MSCs or PBS groups.

Conclusions

This study reveals that after short-term pre-treatment in the EC-inducing medium, induced MSCs acquire stronger vessel formation capability and enhanced angiogenic therapeutic effect in the murine hindlimb ischemia model.

MiR-1908/EXO1 and MiR-203a/FOS, regulated by scd1, are associated with fracture risk and bone health in postmenopausal diabetic women

BACKGROUND

Stearoyl-coenzyme A desaturase-1 (SCD1) can inhibit the development of diabetic bone disease by promoting osteogenesis. In this study, we examined whether this regulation by SCD1 is achieved by regulating the expression of related miRNAs.

METHODS

SCD1 expression levels were observed in human bone-marrow mesenchymal stem cells (BM-MSCs) of patients with type 2 diabetes mellitus (T2DM), and the effect of SCD1 on osteogenesis was observed in human adipose-derived MSCs transfected with the SCD1 lentiviral system. We designed a bioinformatics prediction model to select important differentially expressed miRNAs, and established protein-protein interaction and miRNA-mRNA networks. miRNAs and mRNAs were extracted and their differential expression was detected. The SCD1-miRNA-mRNA network was validated.

FINDINGS

SCD1 expression in bone marrow was downregulated in patients with T2DM and low-energy fracture, and SCD1 expression promotes BM-MSC osteogenic differentiation. The predictors in the nomogram were seven microRNAs, including hsa-miR-1908 and hsa-miR-203a. SCD1 inhibited the expression of CDKN1A and FOS, but promoted the expression of EXO1 and PLS1. miR-1908 was a regulator of EXO1 expression, and miR-203a was a regulator of FOS expression.

INTERPRETATION

The regulation of BM-MSCs by SCD1 is a necessary condition for osteogenesis through the miR-203a/FOS and miR-1908/EXO1 regulatory pathways.

Functional variations between Mesenchymal Stem Cells of different tissue origins: A comparative gene expression profiling

BACKGROUND

Mesenchymal Stem Cells (MSCs), regardless of the tissue sources, are considered as excellent candidates for cellular therapy as they are immune-privileged cells containing a multitude of therapeutic functions that aid in tissue regeneration and repair. For the effective application of these cells in cell therapy, it is important to understand and characterize their biological functions.

OBJECTIVES

The present study attempts to characterize the variations in multipotent function such as cell surface antigen levels, proliferation, differentiation and stemness (pluripotency) potential of MSCs isolated from foetal [wharton's jelly (WJ), foetal and maternal side of placenta (PF and PM)] and adult tissue sources [bone marrow (BM) and adipose tissue (AT)] using gene expression by real time PCR (qRT-PCR).

RESULTS

Amongst the different tissue sources, PM, PF and AT-MSCs exhibited significant increase (p < 0.001, p < 0.001 and p < 0.01 respectively) in CD 73 expression and therefore could have a role in immunomodulation. WJ-MSCs exhibited superior proliferation potential based on growth curve, PCNA and Wnt gene expression. BM-MSCs were superior in exhibiting trilineage differentiation. Enhanced stemness potential (Oct 4 and Nanog) was observed for both BM and WJ-MSCs. In addition, BM and WJ-MSCs expressed high levels of CD 90 making them suitable in bone repair and regeneration.

CONCLUSION

Thus to conclude, out of the five different sources tested, BM an adult source and WJ-MSCs a foetal source were superior in exhibiting most of the biological functions indicating that these sources may be suitable candidates for cell repair and regeneration studies.

Expression and functional regulation of gap junction protein connexin 43 in dermal mesenchymal stem cells from psoriasis patients

BACKGROUND

Psoriasis is a chronic recurrent inflammatory disease. Mesenchymal stem cells (MSCs) can regulate the inflammatory microenvironment, thereby controlling the proliferation, differentiation, and migration of immune cells. Connexin 43(Cx43), a key gap junction protein, has been shown to form gap junctions for communication between neighboring cells.

OBJECTIVE

We investigated the expression of Cx43 in dermal mesenchymal stem cells (DMSCs) derived from psoriasis patients and explored the relationship between the Cx43-mediated gap junction intercellular communication (GJIC) and DMSCs.

METHODS

Human DMSCs were isolated and propagated in adherent culture. Quantitative real-time reverse transcription PCR and western blot and immunofluorescence were used to detect the expression and localization of Cx43 in DMSCs. Fluorescence redistribution after photobleaching was performed to assess adjacent DMSCs GJIC. CCK8 was used to detect the proliferation of DMSCs before and after gap junction blocker (18α-glycyrrhetinic acid; AGA) treatment. Cell energy metabolism was analyzed with an energy metabolism analyzer.

RESULTS

Cx43 was located in the cytoplasm and cytomembrane, as well as partially in the nucleus of DMSCs. The expression of Cx43 in psoriasis DMSCs was higher than that in control samples and the gap junction function was enhanced. In addition, the glycolysis and mitochondrial respiration of psoriasis DMSCs were also enhanced. However, AGA inhibited the expression of Cx43, attenuated GJIC function, and inhibited the proliferation of DMSCs.

CONCLUSIONS

Our results indicated that the expression of Cx43 in DMSCs from psoriasis lesions is increased and that the inhibition of Cx43 leads to the inhibition of both GJIC and DMSCs proliferation.

Prevascularized Tissue-Engineered Human Vaginal Mucosa: In Vitro Optimization and In Vivo Validation

Tissue engineering offers novel therapies for vaginal reconstruction in patients with congenital vaginal agenesis such as Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome. This study aims to reconstruct a prevascularized tissue-engineered model of human vaginal mucosa (HVM) using the self-assembly approach, free of exogenous materials. In this study, a new cell culture method was used to enhance microcapillary network formation while maintaining sufficient biomechanical properties for surgical manipulation. Human vaginal fibroblasts were coseeded with human umbilical vein endothelial cells (HUVECs). Transduction of HUVEC with a vector that allows the expression of both green fluorescent protein (GFP) and luciferase allowed the monitoring of the formation of a microvascular network in vitro and the assessment of the viability and stability of HUVEC in vivo. Two reconstructed vaginal mucosa grafts, a prevascularized, and a nonvascularized control were implanted subcutaneously on the back of 12 female nude mice and monitored for up to 21 days. Prevascularized grafts demonstrated signs of earlier vascularization compared with controls. However, there were no differences in graft survival outcomes in both groups. The finding of mouse red blood cells within GFP-positive capillaries 1 week after implantation demonstrates the capacity of the reconstructed capillary-like network to connect to the host circulation and sustain blood perfusion in vivo. Furthermore, sites of inosculation between GFP-positive HUVEC and mouse endothelial cells were observed within prevascularized grafts. Our results demonstrate that the addition of endothelial cells using a hybrid approach of self-assembly and reseeding generates a mature capillary-like network that has the potential to become functional in vivo, offering an optimized prevascularized HVM model for further translational research. Impact statement This study introduces a prevascularized tissue-engineered model of human vaginal mucosa (HVM), which is adapted for surgical applications. The prevascularization of tissue-engineered grafts aims to enhance graft survival and is an interesting feature for sexual function. Various scaffold-free cell culture methods were tested to reconstruct a mature microcapillary network within HVM grafts while meeting biomechanical needs for surgery. Moreover, this animal study assesses the vascular functionality of prevascularized grafts in vivo, serving as a proof of concept for further translational applications. This research underlines the continuous efforts to optimize current models to closely mimic native tissues and further improve surgical outcomes.

Differentiation of Adipose Tissue-Derived CD34+/CD31- Cells into Endothelial Cells In Vitro

In this study, CD34+/CD31- progenitor cells were isolated from the stromal vascular fraction (SVF) of adipose tissue using magnetic activated cell sorting. The endothelial differentiation capability of these cells in vitro was evaluated by culturing them in vascular endothelial growth factor (VEGF) induced medium for 14 days. Viability, proliferation, differentiation and tube formation of these cells were evaluated. Cell viability study revealed that both undifferentiated and endothelial differentiated cells remained healthy for 14 days. However, the proliferation rate was higher in undifferentiated cells compared to endothelial differentiated ones. Upregulation of endothelial characteristic genes (Von Willebrand Factor (vWF) and VE Cadherin) was observed in 2D culture. However, PECAM (CD31) was only found to be upregulated after the cells had formed tube-like structures in 3D Matrigel culture. These results indicate that adipose derived CD34+/CD31- cells when cultured in VEGF induced medium, are capable differentiation into endothelial-like lineages. Tube formation of the cells started 3h after seeding the cells on Matrigel and formed more stable and connected network 24 h post seeding in presence of VEGF.

Potential therapeutic effects of endothelial cells trans-differentiated from Wharton's Jelly-derived mesenchymal stem cells on altered vascular functions in aged diabetic rat model

BACKGROUND

Diabetes mellitus in elderly represents an exceptional subset in the population vulnerable to cardiovascular events. As aging, diabetes mellitus and hypertension share common pathways, an ideal treatment should possess the ability to counter more than one of, if not all, the underlying mechanisms. Stem cells emerged as a potential approach for complicated medical problems. We tested here the possible role of trans-differentiated endothelial cells (ECs) in the treatment of diabetes mellitus in old rats.

METHODS

Mesenchymal stem cells where isolated from umbilical cord Wharton's Jelly and induced to differentiate into endothelial like-cells using vascular endothelial growth factor-enriched media. Thirty aged male Wistar albino rats were used in the present study. Rats were divided (10/group) into: control group (18-20 months old, weighing 350-400 g, received single intraperitoneal injection as well as single intravenous injection via tail vein of the vehicles), aged diabetic group (18-20 months old, weighing 350-400 g, received single intraperitoneal injection of 50 mg/kg streptozotocin, and also received single intravenous injection of saline via tail vein), and aged diabetic + ECs group (18-20 months old, weighing 350-400 g, received single intraperitoneal injection of 50 mg/kg streptozotocin, and also received single intravenous injection of 2*10⁶ MSC-derived ECs in 0.5 ml saline via tail vein) groups. Assessment of SBP, aortic PWV, and renal artery resistance was performed. Serum levels of ET1, ANG II, IL-6, TNF-α, MDA, ROS, and VEGF were evaluated, as well as the aortic NO tissue level and eNOS gene expression. Histopathological and immunostaining assessments of small and large vessels were also performed.

RESULTS

Induction of diabetes in old rats resulted in significant increase in SBP, aortic PWV, renal artery resistance, and serum levels of ET1, ANG II, IL-6, TNF-α, MDA, ROS, and VEGF. While there was significant decrease in aortic NO tissue level and eNOS gene expression in the aged diabetic group when compared to aged control group. ECs treatment resulted in significant improvement of endothelial dysfunction, inflammation and oxidative stress.

CONCLUSION

We report here the potential therapeutic role of trans-differentiated ECs in aged diabetics. ECs demonstrated anti-inflammatory, antioxidant, gene modifying properties, significantly countered endothelial dysfunction, and improved vascular insult.

The combinatory effect of sinusoidal electromagnetic field and VEGF promotes osteogenesis and angiogenesis of mesenchymal stem cell-laden PCL/HA implants in a rat subcritical cranial defect

BACKGROUND

Restoration of massive bone defects remains a huge challenge for orthopedic surgeons. Insufficient vascularization and slow bone regeneration limited the application of tissue engineering in bone defect. The effect of electromagnetic field (EMF) on bone defect has been reported for many years. However, sinusoidal EMF (SEMF) combined with tissue engineering in bone regeneration remains poorly investigated.

METHODS

In the present study, we investigated the effect of SEMF and vascular endothelial growth factor (VEGF) on osteogenic and vasculogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs). Furthermore, pretreated rBMSC- laden polycaprolactone-hydroxyapatite (PCL/HA) scaffold was constructed and implanted into the subcritical cranial defect of rats. The bone formation and vascularization were evaluated 4 and 12 weeks after implantation.

RESULTS

It was shown that SEMF and VEGF could enhance the protein and mRNA expression levels of osteoblast- and endothelial cell-related markers, respectively. The combinatory effect of SEMF and VEGF slightly promoted the angiogenic differentiation of rBMSCs. The proteins of Wnt1, low-density lipoprotein receptor-related protein 6 (LRP-6), and β-catenin increased in all inducted groups, especially in SEMF + VEGF group. The results indicated that Wnt/β-catenin pathway might participate in the osteogenic and angiogenic differentiation of rBMSCs. Histological evaluation and reconstructed 3D graphs revealed that tissue-engineered constructs significantly promoted the new bone formation and angiogenesis compared to other groups.

CONCLUSION

The combinatory effect of SEMF and VEGF raised an efficient approach to enhance the osteogenesis and vascularization of tissue-engineered constructs, which provided a useful guide for regeneration of bone defects.

Fabrication and Characterization of Pectin Hydrogel Nanofiber Scaffolds for Differentiation of Mesenchymal Stem Cells into Vascular Cells

Despite significant progress over the past few decades, creating a tissue-engineered vascular graft with replicated functions of native blood vessels remains a challenge due to the mismatch in mechanical properties, low biological function, and rapid occlusion caused by restenosis of small diameter vessel grafts (<6 mm diameter). A scaffold with similar mechanical properties and biocompatibility to the host tissue is ideally needed for the attachment and proliferation of cells to support the building of engineered tissue. In this study, pectin hydrogel nanofiber scaffolds with two different oxidation degrees (25 and 50%) were prepared by a multistep methodology including periodate oxidation, electrospinning, and adipic acid dihydrazide crosslinking. Scanning electron microscopy (SEM) images showed that the obtained pectin nanofiber mats have a nano-sized fibrous structure with 300-400 nm fiber diameter. Physicochemical property testing using Fourier transform infrared (FTIR) spectra, atomic force microscopy (AFM) nanoindentations, and contact angle measurements demonstrated that the stiffness and hydrophobicity of the fiber mat could be manipulated by adjusting the oxidation and crosslinking levels of the pectin hydrogels. Live/Dead staining showed high viability of the mesenchymal stem cells (MSCs) cultured on the pectin hydrogel fiber scaffold for 14 days. In addition, the potential application of pectin hydrogel nanofiber scaffolds of different stiffness in stem cell differentiation into vascular cells was assessed by gene expression analysis. Real-time polymerase chain reaction (RT-PCR) results showed that the stiffer scaffold facilitated the differentiation of MSCs into vascular smooth muscle cells, while the softer fiber mat promoted MSC differentiation into endothelial cells. Altogether, our results indicate that the pectin hydrogel nanofibers have the capability of providing mechanical cues that induce MSC differentiation into vascular cells and can be potentially applied in stem cell-based tissue engineering.

Fabrication of vascularized and scaffold-free bone tissue using endothelial and osteogenic cells differentiated from bone marrow derived mesenchymal stem cells

Over-dependence on existing synthetic scaffolds and insufficient vascularization limit the development of tissue engineered bone (TEB). The purpose of this study is to fabricate vascularized and scaffold-free bone tissue using cell sheet technology and to assess its feasibility to repair critical-sized calvarial defects in rats. Firstly, the pre-vascularized cell sheet was formed by seeding BMSC-derived endothelial cells (ECs) on an undifferentiated BMSCs cell sheet layer in vitro. After 3 days of co-culture, ECs migrated and rearranged to form lumens on the BMSC sheet. Secondly, osteogenic cell sheet was formed by inducing osteogenic differentiation of high density BMSCs. Then, the pre-vascularized cell sheet was stacked on BMSC-derived osteogenic cell sheet to fabricate a scaffold-free construct for bone regeneration. Finally, the scaffold-free construct with both angiogenic and osteogenic potential was implanted into critical-sized calvarial defects in adult Wistar rats. Results showed that more functional perfused blood vessels and new bone tissue formed in the pre-vascularized group than that in the controls (both empty and non-pre-vascularized cell sheet group). This study indicates a new promising strategy for bone tissue regeneration.

Substantial Overview on Mesenchymal Stem Cell Biological and Physical Properties as an Opportunity in Translational Medicine

Mesenchymal stem cells (MSC) have piqued worldwide interest for their extensive potential to treat a large array of clinical indications, their unique and controversial immunogenic and immune modulatory properties allowing ample discussions and debates for their possible applications. Emerging data demonstrating that the interaction of biomaterials and physical cues with MSC can guide their differentiation into specific cell lineages also provide new interesting insights for further MSC manipulation in different clinical applications. Moreover, recent discoveries of some regulatory molecules and signaling pathways in MSC niche that may regulate cell fate to distinct lineage herald breakthroughs in regenerative medicine. Although the advancement and success in the MSC field had led to an enormous increase in the amount of ongoing clinical trials, we still lack defined clinical therapeutic protocols. This review will explore the exciting opportunities offered by human and animal MSC, describing relevant biological properties of these cells in the light of the novel emerging evidence mentioned above while addressing the limitations and challenges MSC are still facing.

Knitted Silk-Collagen Scaffold Incorporated with Ligament Stem/Progenitor Cells Sheet for Anterior Cruciate Ligament Reconstruction and Osteoarthritis Prevention

Current surgical management of anterior cruciate ligament (ACL) rupture still remains an intractable challenge in ACL regeneration due to the weak self-healing capability of ACL. Inadequate cell numbers and vascularization within the articular cavity contribute mainly to the poor prognosis. This time, we fabricated a new tissue engineering scaffold by adding ligament stem/progenitor cell (LSPC) sheets to our previous knitted silk-collagen sponge scaffold, which overcame these limitations by providing sufficient numbers of seed cells and a natural extracellular matrix to facilitate regeneration. LSPCs display excellent proliferation and multilineage differentiation capacity. Upon ectopic implantation, the knitted silk-collagen sponge scaffold incorporated with an LSPC sheet exhibited less immune cells but more fibroblast-like cells, deposited ECM and neovascularization, and better tissue ingrowth. In a rabbit model, we excised the ACL and performed a reconstructive surgery with our scaffold. Increased expression of ligament-specific genes and better collagen fibril formation could be observed after orthotopic transplantation. After 6 months, the LSPC sheet group showed better results on ligament regeneration and ligament-bone healing. Furthermore, no obvious cartilage and meniscus degeneration were observed at 6 months postoperation. In conclusion, these results indicated that the new tissue engineering scaffold can promote ACL regeneration and slow down the progression of osteoarthritis, thus suggesting its high clinical potential as an ideal graft in ACL reconstruction.

In vivo efficacy of endothelial growth medium stimulated mesenchymal stem cells derived from patients with critical limb ischemia

Background

Cell therapy has been proposed for patients with critical limb ischemia (CLI). Autologous bone marrow derived cells (BMCs) have been mostly used, mesenchymal stem cells (MSCs) being an alternative. The aim of this study was to characterize two types of MSCs and evaluate their efficacy.

Methods

MSCs were obtained from CLI-patients BMCs. Stimulated- (S-) MSCs were cultured in endothelial growth medium. Cells were characterized by the expression of cell surface markers, the relative expression of 6 genes, the secretion of 10 cytokines and the ability to form vessel-like structures. The cell proangiogenic properties was analysed in vivo, in a hindlimb ischemia model. Perfusion of lower limbs and functional tests were assessed for 28 days after cell infusion. Muscle histological analysis (neoangiogenesis, arteriogenesis and muscle repair) was performed.

Results

S-MSCs can be obtained from CLI-patients BMCs. They do not express endothelial specific markers but can be distinguished from MSCs by their secretome. S-MSCs have the ability to form tube-like structures and, in vivo, to induce blood flow recovery. No amputation was observed in S-MSCs treated mice. Functional tests showed improvement in treated groups with a superiority of MSCs and S-MSCs. In muscles, CD31+ and αSMA+ labelling were the highest in S-MSCs treated mice. S-MSCs induced the highest muscle repair.

Conclusions

S-MSCs exert angiogenic potential probably mediated by a paracrine mechanism. Their administration is associated with flow recovery, limb salvage and muscle repair. The secretome from S-MSCs or secretome-derived products may have a strong potential in vessel regeneration and muscle repair.

Trial registration NCT00533104

Electronic supplementary material

The online version of this article (10.1186/s12967-019-2003-3) contains supplementary material, which is available to authorized users.

Reseeding endothelial cells with fibroblasts to improve the re-endothelialization of pancreatic acellular scaffolds

Pancreatic transplantation remains the only cure for diabetes, but the shortage of donors limits its clinical application. Whole organ decellularized scaffolds offer a new opportunity for pancreatic organ regeneration; however inadequate endothelialization and vascularization can prevent sufficient transport of oxygen and nutrient supplies to the transplanted organ, as well as leading unwanted thrombotic events. In the present study, we explored the re-endothelialization of rat pancreatic acellular scaffolds via circulation perfusion using human skin fibroblasts (FBs) and human umbilical vein endothelial cells (HUVECs). Our results revealed that the cell adhesion rate when these cells were co-cultured was higher than under control conditions, and this increase was associated with increased release of growth factors including VEGF, FGFb, EGF, and IGF-1 as measured by ELISA. When these recellularized organs were implanted in vivo for 28 days in rat dorsal subcutaneous pockets, we found that de novo vasculature formation in the co-culture samples was superior to the control samples. Together these results suggest that endothelial cell and FB co-culture enhances the re-endothelialization and vascularization of pancreatic acellular scaffolds.

Isogenic-induced endothelial cells enhance osteogenic differentiation of mesenchymal stem cells on silk fibroin scaffold

Aim: We investigated the role of induced endothelial cells (iECs) in mesenchymal stem cells (MSCs)/iECs co-culture and assessed their osteogenic ability on silk fibroin nanofiber scaffolds. Methods: The osteogenic differentiation was assessed by the ALP assay, calcium assay and gene expression studies. Results: The osteogenic differentiation of the iECs co-cultures was found to be higher than the MSCs group and proximal to endothelial cells (ECs) co-cultures. Furthermore, the usage of isogenic iECs for co-culture increased the osteogenic and endothelial gene expression. Conclusion: These findings suggest that iECs mimic endothelial cells when co-cultured with MSCs and that one MSCs source can be used to give rise to both MSCs and iECs. The isogenic MSCs/iECs co-culture provides a new option for bone tissue engineering applications.

Cell-Based Therapies for Stroke: Are We There Yet?

Stroke is the second leading cause of death and physical disability, with a global lifetime incidence rate of 1 in 6. Currently, the only FDA approved treatment for ischemic stroke is the administration of tissue plasminogen activator (tPA). Stem cell clinical trials for stroke have been underway for close to two decades, with data suggesting that cell therapies are safe, feasible, and potentially efficacious. However, clinical trials for stroke account for <1% of all stem cell trials. Nevertheless, the resources devoted to clinical research to identify new treatments for stroke is still significant (53–64 million US$, Phase 1–4). Notably, a quarter of cell therapy clinical trials for stroke have been withdrawn (15.2%) or terminated (6.8%) to date. This review discusses the bottlenecks in delivering a successful cell therapy for stroke, and the cost-to-benefit ratio necessary to justify these expensive trials. Further, this review will critically assess the currently available data from completed stroke trials, the importance of standardization in outcome reporting, and the role of industry-led research in the development of cell therapies for stroke.

An injectable scaffold based on temperature-responsive hydrogel and factor-loaded nanoparticles for application in vascularization in tissue engineering

Controlled release of functional factors contributes to target migration of therapeutic cells and plays a crucial role in the in situ vascularization of tissue repair and regeneration. A biomedical application requires the selective release of multiple factors which will guide the synergy of the cells. Here, we developed an injectable system based on a temperature-responsive hydrogel and stromal cell-derived factor-1 (SDF-1)/vascular endothelial growth factor (VEGF) loaded into two types of nanoparticles to induce migration and rapid proliferation of mesenchymal stem cells (MSCs) and endothelial cells (ECs) via selective SDF-1/VEGF release. Series of in vitro and in vivo experiments demonstrate that our composited system can accurately guide MSCs and ECs for vascularization. In addition, the properties of the nanoparticles and hydrogel, including micro/nanoscales, characteristic of charge, and biocompatibility, played crucial roles for the selective release and cells behavior (target migration and rapid proliferation).

Vessel graft fabricated by the on-site differentiation of human mesenchymal stem cells towards vascular cells on vascular extracellular matrix scaffold under mechanical stimulation in a rotary bioreactor

Although a significant number of studies on vascular tissue engineering have been reported, the current availability of vessel substitutes in the clinic remains limited mainly due to the mismatch of their mechanical properties and biological functions with native vessels. In this study, a novel approach to fabricating a vessel graft for vascular tissue engineering was developed by promoting differentiation of human bone marrow mesenchymal stem cells (MSCs) into endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) on a native vascular extracellular matrix (ECM) scaffold in a rotary bioreactor. The expression levels of CD31 and vWF, and the LDL uptake capacity as well as the angiogenesis capability of the EC-like cells in the dynamic culture system were significantly enhanced compared to the static system. In addition, α-actin and smoothelin expression, and contractility of VSMC-like cells harvested from the dynamic model were much higher than those in a static culture system. The combination of on-site differentiation of stem cells towards vascular cells in the natural vessel ECM scaffold and maturation of the resulting vessel construct in a dynamic cell culture environment provides a promising approach to fabricating a clinically applicable vessel graft with similar mechanical properties and physiological functions to those of native blood vessels.

Combination of Ligusticum Chuanxiong and Radix Paeonia Promotes Angiogenesis in Ischemic Myocardium through Notch Signalling and Mobilization of Stem Cells

Objective

To study the cardioprotective mechanism by which the combination of Chuanxiong (CX) and Chishao (CS) promotes angiogenesis.

Methods

Myocardial infarction (MI) mouse models were induced by ligation of the left anterior descending coronary artery. The effects on cardiac function were evaluated in the perindopril tert-butylamine group (PB group) (3 mg/kg/d), CX group (55 mg/kg/d), CS group (55 mg/kg/d), and CX and CS combination (CX-CS) group (27.5 mg/kg/d CX plus 27.5 mg/kg/d CS). RO4929097, an inhibitor of Notch γ secretase, was used (10 mg/kg/d) to explore the role of Notch signalling in the CX-CS-induced promotion of angiogenesis in the myocardial infarcted border zone (IBZ). The left ventricular ejection fraction (LVEF) and percentage of MI area were evaluated with animal ultrasound and Masson staining. The average optical densities (AODs) of CD31 and vWF in the myocardial IBZ were detected by immunofluorescence. Angiogenesis-related proteins including hypoxia-inducible factor 1-alpha (HIF-1α), fibroblast growth factor receptor 1 (FGFR-1), Notch1 and Notch intracellular domain (NICD), and stem cell mobilization-related proteins including stromal cell-derived factor 1 (SDF-1), C-X-C chemokine receptor type 4 (CXCR-4), and cardiotrophin1 were detected by western blot analysis.

Results

Compared with the model group, the CX-CS and PB groups both showed markedly improved LVEF and decreased percentage of MI area after 21 days of treatment. Although the CX group and CS group showed increased LVEF and decreased MI areas compared with the model group, the difference was not significant. The AOD of CD31 in the IBZ in both the model and the CX-CS-I group was markedly reduced compared with that in the sham group. CX-CS significantly increased the CD31 AOD in the IBZ and decreased the AODs of CD31 and vWF in the infarct zone compared with those in the model group. The expression of HIF-1α in both the model group and the CX-CS group was higher than that in the sham group. Compared with the model group, the expression of FGFR-1, SDF-1, cardiotrophin1, Notch1, and NICD was increased in the CX-CS group. Notch1 and NICD expression in the CX-CS-I group was reduced compared with that in the CX-CS group.

Conclusions

The combination of CX and CS protected cardiomyocytes in the IBZ better than CX or CS alone. The mechanism by which CX-CS protects ischemic myocardium may be related to the proangiogenesis effect of CX-CS exerted through Notch signalling and the mobilization of stem cells to the IBZ.

TRIP-1 Promotes the Assembly of an ECM That Contains Extracellular Vesicles and Factors That Modulate Angiogenesis

Transforming growth factor beta receptor II interacting protein-1 (TRIP-1) was recently localized in the mineralized matrices of bone and dentin. The function of TRIP-1 in the ECM is enigmatic, as it is known to function as an intracellular endoplasmic reticulum protein during protein synthesis. Based on its localization pattern in bones and teeth, we posited that TRIP-1 must function as a regulatory protein with multiple functions during mineralization. In this study, we determined the in vivo function of TRIP-1 by an implantation assay performed using recombinant TRIP-1 and TRIP-1 overexpressing and knocked down cells embedded in a 3D biomimetic scaffold. After 4 weeks, the subcutaneous tissues from TRIP-1 overexpressing cells and scaffolds containing recombinant TRIP-1 showed higher expression levels of several ECM proteins such as fibronectin and collagen I. Picrosirius red and polarized microscopy was used to identify the birefringence of the collagen fibrils in the extracellular matrix (ECM). Interestingly, knockdown of TRIP-1 resulted in lower fibronectin and downregulation of the activation of the ERK MAP kinase. We further demonstrate that TRIP-1 overexpression leads to higher expression of pro-angiogenic marker VEGF and downregulation of anti-angiogenic factors such as pigment epithelium-derived factor and thrombospondin. Field emission scanning electron microscope results demonstrated that TRIP-1 overexpressing cells released large amount of extracellular microvesicles which were localized on the fibrillar matrix in the ECM. Overall, this study demonstrates that TRIP-1 can promote secretion of extracellular vesicles, synthesis of key osteogenic ECM matrix proteins and promote angiogenesis.

In Vitro Expression of Cytokeratin 19 in Adipose-Derived Stem Cells Is Induced by Epidermal Growth Factor

BACKGROUND Cytokeratin 19 (CK19) is a typical epithelial marker. In this study, we determined whether epidermal growth factor (EGF) or basic fibroblast growth factor (bFGF) could enhance CK19 expression in adipose-derived stem cells (ADSCs), thereby inducing the differentiation of ADSCs into epithelial-like cells. MATERIAL AND METHODS ADSCs were isolated from perinephric fat, and the expression of CD29, CD90, and CD105 was confirmed. Following isolation, ADSCs were cultured in static medium or medium containing EGF or bFGF. RESULTS Flow cytometry revealed that EGF and bFGF could alter mesenchymal stem cell markers as well as the cell cycle of ADSCs. Western blotting and immunofluorescence revealed that after 14 days, EGF treatment enhanced the expression of CK19 in ADSCs. CONCLUSIONS Our findings offer important insight for the clinical use of ADSCs in the generation of epithelial-like cells in the future.

Regenerative Medicine Applications of Mesenchymal Stem Cells

A major research challenge is to develop therapeutics that assist with healing damaged tissues and organs because the human body has limited ability to restore the majority of these tissues and organs to their original state. Tissue engineering (TE) and regenerative medicine (RM) promises to offer efficient therapeutic biological strategies that use mesenchymal stem cells (MSCs). MSCs possess the capability for self-renewal, multilineage differentiation, and immunomodulatory properties that make them attractive for clinical applications. They have been extensively investigated in numerous preclinical and clinical settings in an attempt to overcome their challenges and promote tissue regeneration and repair. This review explores the exciting opportunities afforded by MSCs, their desirable properties as cellular therapeutics in RM, and implicates their potential use in clinical practice. Here, we attempt to identify challenges and issues that determine the clinical efficacy of MSCs as treatment for skeletal and non-skeletal tissues.