Mesenchymal stem cells promote engraftment of human umbilical cord blood-derived CD34(+) cells in NOD/SCID mice

Effect of fibrin on the expression of adhesion molecules (ICAM-1, ITGAV, and ITGB3) in unrestricted somatic stem cells

BACKGROUND

Hematopoietic stem cell expansion relies on direct cell-cell interactions mediated by adhesion molecules, integrins, and cytokines. Unrestricted somatic stem cells have emerged as novel stromal cells supporting hematopoietic stem cell expansion in co-culture conditions via secretion of hematopoiesis-related cytokines and the expression of adhesion molecules. Previous research showed fibrin increased hematopoiesis-related gene expression in these cells. This study focused on the adhesive characteristics of unrestricted somatic stem cells on 3D fibrin scaffolds.

METHODS

Unrestricted somatic stem cells were isolated from umbilical cord blood and characterized using flow cytometry and multilineage differentiation assays. Scanning electron microscopy and DAPI staining were employed to analyze cell attachment to fibrin. Viability on fibrin was assessed through MTT assays. Quantitative polymerase chain reaction was conducted to evaluate the expression of intercellular adhesion molecule 1 (ICAM-1), integrin subunit αv (ITGAV), and integrin subunit β3 (ITGB3) in cells cultured on 3D fibrin scaffolds.

RESULTS

Cells were positive for CD73, CD105, and CD166 but negative for CD45. Alizarin red and Oil red O stains confirmed calcium deposition and lipid vacuoles. MTT assays revealed that fibrin positively impacts viability. ITGAV expression was significantly increased in cells cultured on fibrin compared to those cultured on plastic tissue culture plates (Control Group). Furthermore, ITGB3 expression showed no significant change in both groups, while ICAM-1 expression was downregulated in cells cultured on fibrin.

CONCLUSIONS

Our study revealed that fibrin has a positive impact on the expression of ITGAV, which plays a crucial role in direct cell-cell interactions affecting hematopoietic stem cell expansion.

Priming human bone marrow-derived mesenchymal stromal cells with signaling modifiers boosts their functionality: Potential application in regenerative therapies

Mesenchymal stromal cells (MSCs) isolated from tissues such as bone marrow, cord, cord blood, etc., are frequently used as feeder layers to expand hematopoietic stem/ progenitor cells (HSCs/HSPCs) in vitro. They are also co-infused with the HSCs to improve the efficacy of transplantation. However, the MSCs sourced from non-hematopoietic tissues could have suboptimal hematopoiesis-supportive ability. Likewise, the functionality of the MSCs is known to decline after continuous in vitro culture - an unavoidable manipulation to get clinically relevant cell numbers. Hence, it may be necessary to boost the hematopoiesis-supportive ability of the long-term cultured MSCs so that they can, in turn, be used to prime the HSCs before their clinical applications. Here, I show that priming human bone marrow-derived MSCs (BMSCs) with appropriately selected signaling modifiers and integrin-activating bioactive peptides boosts their hematopoiesis-supportive ability, as seen by the formation of a significantly higher number of colonies from the bone marrow-derived mononuclear cells (MNCs) and extensive proliferation of CD34+ HSCS briefly interacted with them. Priming the BMSCs with signaling modifiers is a cost-effective and time-efficient process as synthesizing these small molecule compounds is relatively inexpensive - an advantage in clinical settings. The approach of briefly interacting the donor HSCs/HSPCs with the primed BMSCs just before their infusion into the recipients' bodies could save the cost of long-term ex vivo expansion of HSCs. This concept could also find applications in other regenerative medicine protocols after identifying suitable pharmacological modulators that have the desired effects on the target cells.

Asperuloside alleviates osteoporosis by promoting autophagy and regulating Nrf2 activation

BACKGROUND

Osteoporosis is a metabolic bone disease that has a common occurrence in postmenopausal women. Asperuloside (ASP) has been reported to exert anti-inflammatory and anti-oxidative effects in numerous diseases, such as rheumatoid arthritis and acute lung injury. However, whether ASP plays a role in osteoporosis has not been addressed.

METHODS

In vivo, ovariectomy (OVX) was used to induce mouse osteoporosis. Then, the mice were treated with 20 and 40 mg/kg ASP. In vitro, MC3T3-E1 cells were treated with 0, 1, 10, 20, 40 and 80 µM ASP. We chose 20 and 40 µM for further experiments due to no significant effects on cell viability.

RESULTS

The data indicated that ASP reduced osteoporosis in OVX mice and promoted osteogenic differentiation and mineralization in MC3T3-E1 cells. In addition, we explored that ASP protected against osteoporosis via inducing autophagy and activating Nrf2.

CONCLUSION

ASP alleviates OVX-induced osteoporosis by promoting autophagy and regulating Nrf2 activation.

Intravenous infusions of mesenchymal stromal cells have cumulative beneficial effects in a porcine model of chronic ischaemic cardiomyopathy

AIMS

The development of cell therapy as a widely available clinical option for ischaemic cardiomyopathy is hindered by the invasive nature of current cell delivery methods. Furthermore, the rapid disappearance of cells after transplantation provides a cogent rationale for using repeated cell doses, which, however, has not been done thus far in clinical trials because it is not feasible with invasive approaches. The goal of this translational study was to test the therapeutic utility of the intravenous route for cell delivery.

METHODS AND RESULTS

Pigs with chronic ischaemic cardiomyopathy induced by myocardial infarction received one or three intravenous doses of allogeneic bone marrow mesenchymal stromal cells (MSCs) or placebo 35 days apart. Rigour guidelines, including blinding and randomization, were strictly followed. A comprehensive assessment of left ventricular (LV) function was conducted with three independent methods (echocardiography, magnetic resonance imaging, and haemodynamic studies). The results demonstrate that three doses of MSCs improved both load-dependent and independent indices of LV function and reduced myocardial hypertrophy and fibrosis; in contrast, one dose failed to produce most of these benefits.

CONCLUSIONS

To our knowledge, this is the first study to show that intravenous infusion of a cell product improves LV function and structure in a large animal model of chronic ischaemic cardiomyopathy and that repeated infusions are necessary to produce robust effects. This study, conducted in a clinically relevant model, supports a new therapeutic strategy based on repeated intravenous infusions of allogeneic MSCs and provides a foundation for a first-in-human trial testing this strategy in patients with chronic ischaemic cardiomyopathy.

The Evaluation of Mass/DNA Copy Number of Mitochondria in Umbilical Cord Blood-derived Hematopoietic Stem Cells Cocultured with MSCs

Over recent decades, UCB has been widely used as an excellent alternative source of HSCs for treating many hematologic disorders. Recent studies suggest using mesenchymal stroma cell co-cultures to increase the number of HSCs prior to transplantation. Considering the critical role of mitochondria in the cell's fate and the importance of the self-renewal capacity of HSCs in HSCT, we decided to investigate the mass/DNA copy number of mitochondria in HSCs while co-cultured with MSCs and alone after seven days. UCB units were collected from full-term deliveries. MSCs and HSCs were isolated from UCB and the purity of cells was confirmed by flow cytometry. The mtDNA-Copy Number of HSCs was calculated using prob-based real-time PCR. Furthermore, Mito Tracker Green dye measured the mass of mitochondria of HSCs. HSCs from MSC co-culture group showed significantly fewer mtDNA-CN compared to HSCs alone after seven days (p < 0.001). Besides, by comparing the two groups on day seven to HSCs on day zero, we observed a mild increase in the mitochondrial mass of HSCs alone compared to the MSC-HSC co-culture group (p < 0.05). Concerning previous studies that have proved the association between lower mass/DNA-copy number of mitochondria in CD34 + HSCs and lower metabolic activity along with higher quiescence maintenance, and by considering the results of this experiment, it seems that the MSC-HSC co-cultures might be associated with a higher expansion of HSCs as well as stemness maintenance leading to the improvement in engraftment. Nevertheless, further investigations are required to clarify the exact connection between lower mass/DNA-copy number of mitochondria and stemness maintenance in HSCs.

Hematopoietic and leukemic stem cells homeostasis: the role of bone marrow niche

The bone marrow microenvironment (BMM) has highly specialized anatomical characteristics that provide a sanctuary place for hematopoietic stem cells (HSCs) that allow appropriate proliferation, maintenance, and self-renewal capacity. Several cell types contribute to the constitution and function of the bone marrow niche. Interestingly, uncovering the secrets of BMM and its interaction with HSCs in health paved the road for research aiming at better understanding the concept of leukemic stem cells (LSCs) and their altered niche. In fact, they share many signals that are responsible for interactions between LSCs and the bone marrow niche, due to several biological similarities between LSCs and HSCs. On the other hand, LSCs differ from HSCs in their abnormal activation of important signaling pathways that regulate survival, proliferation, drug resistance, invasion, and spread. Targeting these altered niches can help in better treatment choices for hematological malignancies and bone marrow disorders in general and acute myeloid leukemia (AML) in particular. Moreover, targeting those niches may help in decreasing the emergence of drug resistance and lower the relapse rate. In this article, the authors reviewed the most recent literature on bone marrow niches and their relations with either normal HSCs and AML cells/LSC, by focusing on pathogenetic and therapeutic implications.

Efficacy of Engraftment and Safety of Human Umbilical Di-Chimeric Cell (HUDC) Therapy after Systemic Intraosseous Administration in an Experimental Model

Cell-based therapies hold promise for novel therapeutic strategies in regenerative medicine. We previously characterized in vitro human umbilical di-chimeric cells (HUDCs) created via the ex vivo fusion of human umbilical cord blood (UCB) cells derived from two unrelated donors. In this in vivo study, we assessed HUDC safety and biodistribution in the NOD SCID mouse model at 90 days following the systemic intraosseous administration of HUDCs. Twelve NOD SCID mice (n = 6/group) received intraosseous injection of donor UCB cells (3.0 × 106) in Group 1, or HUDCs (3.0 × 106) in Group 2, without immunosuppression. Flow cytometry assessed hematopoietic cell surface markers in peripheral blood and the presence of HLA-ABC class I antigens in lymphoid and non-lymphoid organs. HUDC safety was assessed by weekly evaluations, magnetic resonance imaging (MRI), and at autopsy for tumorigenicity. At 90 days after intraosseous cell administration, the comparable expression of HLA-ABC class I antigens in selected organs was found in UCB control and HUDC therapy groups. MRI and autopsy confirmed safety by no signs of tumor growth. This study confirmed HUDC biodistribution to selected lymphoid organs following intraosseous administration, without immunosuppression. These data introduce HUDCs as a novel promising approach for immunomodulation in transplantation.

Influential factors for optimizing and strengthening mesenchymal stem cells and hematopoietic stem cells co-culture

Mesenchymal stem cells (MSCs) and Hematopoietic stem cells (HSCs) are two types of bone marrow stem cells that can proliferate and differentiate into different cell lineages. HSCs interact with MSCs under protective conditions, called niche. Numerous studies have indicated supportive effects of MSCs on HSCs proliferation and differentiation. Furthermore, HSCs have many clinical applications and could treat different hematologic and non-hematologic diseases. For this purpose, there is a need to perform in vitro studies to optimize their expansion. Therefore, various methods including co-culture with MSCs are used to address the limitations of HSCs culture. Some parameters that might be effective for improving the MSC/ HSC co-culture systems. Manipulating culture condition to enhance MSC paracrine activity, scaffolds, hypoxia, culture medium additives, and the use of various MSC sources, have been examined in different studies. In this article, we investigated the potential factors for optimizing HSCs/ MSCs co-culture. It might be helpful to apply a suitable approach for providing high-quality HSCs and improving their therapeutic applications.

Production of alginate macrocapsule device for long-term normoglycaemia in the treatment of type 1 diabetes mellitus with pancreatic cell sheet engineering

Type 1 diabetes-mellitus (T1DM) is characterized by damage of beta cells in pancreatic islets. Cell-sheet engineering, one of the newest therapeutic approaches, has also been used to create functional islet systems by creating islet/beta cell-sheets and transferring these systems to areas that require minimally invasive intervention, such as extrahepatic areas. Since islets, beta cells, and pancreas transplants are allogeneic, immune problems such as tissue rejection occur after treatment, and patients become insulin dependent again. In this study, we aimed to design the most suitable cell-sheet treatment method and macrocapsule-device that could provide long-term normoglycemia in rats. Firstly, mesenchymal stem cells (MSCs) and beta cells were co-cultured in a temperature-responsive culture dish to obtain a cell-sheet and then the cell-sheets macroencapsulated using different concentrations of alginate. The mechanical properties and pore sizes of the macrocapsule-device were characterized. The viability and activity of cell-sheets in the macrocapsule were evaluatedin vitroandin vivo. Fasting blood glucose levels, body weight, and serum insulin & C-peptide levels were evaluated after transplantation in diabetic-rats. After the transplantation, the blood glucose level at 225 mg dl-1on the 10th day dropped to 168 mg dl-1on the 15th day, and remained at the normoglycemic level for 210 days. In this study, an alginate macrocapsule-device was successfully developed to protect cell-sheets from immune attacks after transplantation. The results of our study provide the basis for future animal and human studies in which this method can be used to provide long-term cellular therapy in T1DM patients.

Mesenchymal stromal cells, metabolism, and mitochondrial transfer in bone marrow normal and malignant hematopoiesis

Hematopoietic stem cell (HSC) transplantation-based treatments are in different phases of clinical development, ranging from current therapies to a promise in the repair and regeneration of diseased tissues and organs. Mesenchymal stromal/stem cells (MSCs), which are fibroblast-like heterogeneous progenitors with multilineage differentiation (osteogenic, chondrogenic, and adipogenic) and self-renewal potential, and exist in the bone marrow (BM), adipose, and synovium, among other tissues, represent one of the most widely used sources of stem cells in regenerative medicine. MSCs derived from bone marrow (BM-MSCs) exhibit a variety of traits, including the potential to drive HSC fate and anti-inflammatory and immunosuppressive capabilities via paracrine activities and interactions with the innate and adaptive immune systems. The role of BM-MSC-derived adipocytes is more controversial and may act as positive or negative regulators of benign or malignant hematopoiesis based on their anatomical location and functional crosstalk with surrounding cells in the BM microenvironment. This review highlights the most recent clinical and pre-clinical findings on how BM-MSCs interact with the surrounding HSCs, progenitors, and immune cells, and address some recent insights on the mechanisms that mediate MSCs and adipocyte metabolic control through a metabolic crosstalk between BM microenvironment cells and intercellular mitochondrial transfer in normal and malignant hematopoiesis.

Stem cells in treatment of crohn's disease: Recent advances and future directions

BACKGROUND AND AIM

Crohn's disease (CD) is an inflammatory bowel disease that can affect any part of the intestine. There is currently no recognized cure for CD because its cause is unknown. One of the modern approaches that have been suggested for the treatment of CD and other inflammatory-based disorders is cell therapy.

METHODS

Search terms were stem cell therapy, CD, adipose-derived stem cells, mesenchymal stem cells, and fistula. Of 302 related studies, we removed duplicate and irrelevant papers and identified the ones with proper information related to our scope of the research by reviewing all the abstracts and categorizing each study into the proper section.

RESULTS AND CONCLUSION

Nowadays, stem cell therapy is widely implied in treating CD. Although mesenchymal and adipose-derived tissue stem cells proved to be safe in treating Crohn's-associated fistula, there are still debates on an optimal protocol to use. Additionally, there is still a lack of evidence on the efficacy of stem cell therapy for intestinal involvement of CD. Future investigations should focus on preparing a standard protocol as well as luminal stem cell therapy in patients.

Expanding hematopoietic stem cell ex vivo: recent advances and technical considerations

Hematopoietic stem cells (HSCs) are the most primitive cell type in the hematopoietic hierarchy, which are responsible for sustaining the lifelong production of mature blood and immune cells. Due to their superior long-term regenerative capacity, HSC therapies such as stem cell transplantation have been used in a broad range of hematologic disorders. However, the rarity of this population in vivo considerably limits its clinical applications and large-scale analyses such as screening and safety studies. Therefore, ex vivo culture methods that allow long-term expansion and maintenance of functional HSCs are instrumental in overcoming the difficulties in studying HSC biology and improving HSC therapies. In this perspective, we discuss recent advances and technical considerations for three ex vivo HSC expansion methods including 1) polyvinyl alcohol-based HSC expansion, 2) mesenchymal stromal cell-HSC co-culture, and 3) two-/three-dimensional hydrogel HSC culture. This review summarizes the presentations and discussions from the 2022 International Society for Experimental Hematology (ISEH) Annual Meeting New Investigator Technology Session.

Safety and efficacy of mesenchymal stromal cell therapy for multi-drug-resistant acute and late-acute graft-versus-host disease following allogeneic hematopoietic stem cell transplantation

Graft versus host disease (GvHD) remains a significant risk for mortality and morbidity following allogeneic hematopoietic stem cell transplantation (HSCT). A growing literature supports successful applications of mesenchymal stromal cells (MSCs) for the treatment of steroid-refractory acute GvHD (aGvHD). However, there is limited knowledge about the effects of MSC treatment on late-acute GvHD (late aGvHD). In this article, we present our multicenter study on the safety and efficacy of MSC therapy for patients with steroid-refractory late aGvHD in comparison to those with aGvHD. The outcome measures include non-relapse mortality (NRM) and survival probability over a 2-year follow-up. The study includes a total of 76 patients with grades III-IV aGvHD (n = 46) or late aGvHD (n = 30), who had been treated with at least two lines of steroid-containing immunosuppressive therapy. Patients received weekly adipose or umbilical cord-derived MSC infusions at a dose of median 1.55 (ranging from 0.84 to 2.56) × 106/kg in the aGvHD group, and 1.64 (ranging from 0.85 to 2.58) × 106/kg in the late aGvHD group. This was an add-on treatment to ongoing conventional pharmaceutical management. In the aGvHD group, 23 patients received one or two infusions, 20 patients had 3-4, and three had ≥ 5. Likewise, in the late aGvHD group, 20 patients received one or two infusions, nine patients had 3-4, and one had ≥ 5. MSC was safe without acute or late adverse effects in 76 patients receiving over 190 infusions. In aGvHD group, 10.9% of the patients had a complete response (CR), 23.9% had a partial response (PR), and 65.2% had no response (NR). On the other hand, in the late aGvHD group, 23.3% of the patients had CR, 36.7% had PR, and the remaining 40% had NR. These findings were statistically significant (p = 0.031). Also, at the 2-year follow-up, the cumulative incidence of NRM was significantly lower in patients with late aGvHD than in patients with aGvHD at 40% (95% CI, 25-62%) versus 71% (95% CI, 59-86%), respectively (p = 0.032). In addition, the probability of survival at 2 years was significantly higher in patients with late aGvHD than in the aGvHD group at 59% (95% CI, 37-74%) versus 28% (95% CI, 13-40%), respectively (p = 0.002). To our knowledge, our study is the first to compare the safety and efficacy of MSC infusion(s) for the treatment of steroid-resistant late aGVHD and aGVHD. There were no infusion-related adverse effects in either group. The response rate to MSC therapy was significantly higher in the late aGvHD group than in the aGvHD group. In addition, at the 2-year follow-up, the survival and NRM rates were more favorable in patients with late aGVHD than in those with aGVHD. Thus, the results are encouraging and warrant further studies to optimize MSC-based treatment for late aGVHD.

Mesenchymal Stem Cells in Acquired Aplastic Anemia: The Spectrum from Basic to Clinical Utility

Aplastic anemia (AA), a rare but potentially life-threatening disease, is a paradigm of bone marrow failure syndromes characterized by pancytopenia in the peripheral blood and hypocellularity in the bone marrow. The pathophysiology of acquired idiopathic AA is quite complex. Mesenchymal stem cells (MSCs), an important component of the bone marrow, are crucial in providing the specialized microenvironment for hematopoiesis. MSC dysfunction may result in an insufficient bone marrow and may be associated with the development of AA. In this comprehensive review, we summarized the current understanding about the involvement of MSCs in the pathogenesis of acquired idiopathic AA, along with the clinical application of MSCs for patients with the disease. The pathophysiology of AA, the major properties of MSCs, and results of MSC therapy in preclinical animal models of AA are also described. Several important issues regarding the clinical use of MSCs are discussed finally. With evolving knowledge from basic studies and clinical applications, we anticipate that more patients with the disease can benefit from the therapeutic effects of MSCs in the near future.

Mesenchymal stromal cells improve the transplantation outcome of CRISPR-Cas9 gene-edited human HSPCs

Mesenchymal stromal cells (MSCs) have been employed in vitro to support hematopoietic stem and progenitor cell (HSPC) expansion and in vivo to promote HSPC engraftment. Based on these studies, we developed an MSC-based co-culture system to optimize the transplantation outcome of clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 gene-edited (GE) human HSPCs. We show that bone marrow (BM)-MSCs produce several hematopoietic supportive and anti-inflammatory factors capable of alleviating the proliferation arrest and mitigating the apoptotic and inflammatory programs activated in GE-HSPCs, improving their expansion and clonogenic potential in vitro. The use of BM-MSCs resulted in superior human engraftment and increased clonal output of GE-HSPCs contributing to the early phase of hematological reconstitution in the peripheral blood of transplanted mice. In conclusion, our work poses the biological bases for a novel clinical use of BM-MSCs to promote engraftment of GE-HSPCs and improve their transplantation outcome.

Research trends of mesenchymal stem cells application in orthopedics: A bibliometric analysis of the past 2 decades

Background

Bibliometric analysis and visualization tools were used to determine the development trend of mesenchymal stem cells (MSCs) in orthopedics in the past 20 years, so as to guide researchers to explore new directions and hotspots in the field in the future.

Methods

In the Web of Science Core Collection, all articles about the application of MSCs in orthopedics from 2002 to 2021 were searched. The qualitative and quantitative analysis was performed based on Web of Science and CiteSpace software.

Results

A total of 2,207 articles were retrieved. After excluding non-article articles such as review and letter and non-English language articles, 1,489 articles were finally included. Over the past 2 decades, the number of publications on the application of MSCs in orthopedic diseases increased. Among them, the United States, China, Japan and the United Kingdom have made significant contributions in this field. The most productive institution was Shanghai Jiao Tong University. Journal of Orthopedic Research published the largest number of publications. The journal with the highest citation frequency was Experimental Hematology. The authors with the highest output and the highest citation frequency on average were Rochy S. Tuan and Scott A. Rodeo, respectively. "Mesenchymal stem cell", "in vitro" and "Differentiation" were the top three keywords that appeared. From the keyword analysis, the current research trend indicates that the primary research hotspots of MSCs in orthopedics are the source of MSCs, in vitro experiments and the differentiation of MSCs into bone and cartilage. The frontiers of this field are the combination of MSCs and platelet-rich plasma (PRP), the treatment of knee diseases such as osteoarthritis, osteogenic differentiation, and the application of biological scaffolds combined with MSCs.

Conclusion

Over the past 2 decades, the application of MSCs in orthopedic diseases has received increasing attention. Our bibliometric analysis results provide valuable information and research trends for researchers in the field to understand the basic knowledge of the field, identify current research hotspots, potential collaborators, and future research frontiers.

How mesenchymal stem cell cotransplantation with hematopoietic stem cells can improve engraftment in animal models

BACKGROUND

Bone marrow transplantation (BMT) can be applied to both hematopoietic and nonhematopoietic diseases; nonetheless, it still comes with a number of challenges and limitations that contribute to treatment failure. Bearing this in mind, a possible way to increase the success rate of BMT would be cotransplantation of mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) to improve the bone marrow niche and secrete molecules that enhance the hematopoietic engraftment.

AIM

To analyze HSC and MSC characteristics and their interactions through cotransplantation in murine models.

METHODS

We searched for original articles indexed in PubMed and Scopus during the last decade that used HSC and MSC cotransplantation and in vivo BMT in animal models while evaluating cell engraftment. We excluded in vitro studies or studies that involved graft versus host disease or other hematological diseases and publications in languages other than English. In PubMed, we initially identified 555 articles and after selection, only 12 were chosen. In Scopus, 2010 were identified, and six were left after the screening and eligibility process.

RESULTS

Of the 2565 articles found in the databases, only 18 original studies met the eligibility criteria. HSC distribution by source showed similar ratios, with human umbilical cord blood or animal bone marrow being administered mainly with a dose of 1 × 10⁷ cells by intravenous or intrabone routes. However, MSCs had a high prevalence of human donors with a variety of sources (umbilical cord blood, bone marrow, tonsil, adipose tissue or fetal lung), using a lower dose, mainly 10⁶ cells and ranging 10⁴ to 1.5 × 10⁷ cells, utilizing the same routes. MSCs were characterized prior to administration in almost every experiment. The recipient used was mostly immunodeficient mice submitted to low-dose irradiation or chemotherapy. The main technique of engraftment for HSC and MSC cotransplantation evaluation was chimerism, followed by hematopoietic reconstitution and survival analysis. Besides the engraftment, homing and cellularity were also evaluated in some studies.

CONCLUSION

The preclinical findings validate the potential of MSCs to enable HSC engraftment in vivo in both xenogeneic and allogeneic hematopoietic cell transplantation animal models, in the absence of toxicity.

Transcription regulators differentiate mesenchymal stem cells into chondroprogenitors, and their in vivo implantation regenerated the intervertebral disc degeneration

BACKGROUND

Intervertebral disc degeneration (IVDD) is the leading cause of lower back pain. Disc degeneration is characterized by reduced cellularity and decreased production of extracellular matrix (ECM). Mesenchymal stem cells (MSCs) have been envisioned as a promising treatment for degenerative illnesses. Cell-based therapy using ECM-producing chondrogenic derivatives of MSCs has the potential to restore the functionality of the intervertebral disc (IVD).

AIM

To investigate the potential of chondrogenic transcription factors to promote differentiation of human umbilical cord MSCs into chondrocytes, and to assess their therapeutic potential in IVD regeneration.

METHODS

MSCs were isolated and characterized morphologically and immunologically by the expression of specific markers. MSCs were then transfected with Sox-9 and Six-1 transcription factors to direct differentiation and were assessed for chondrogenic lineage based on the expression of specific markers. These differentiated MSCs were implanted in the rat model of IVDD. The regenerative potential of transplanted cells was investigated using histochemical and molecular analyses of IVDs.

RESULTS

Isolated cells showed fibroblast-like morphology and expressed CD105, CD90, CD73, CD29, and Vimentin but not CD45 antigens. Overexpression of Sox-9 and Six-1 greatly enhanced the gene expression of transforming growth factor beta-1 gene, BMP, Sox-9, Six-1, and Aggrecan, and protein expression of Sox-9 and Six-1. The implanted cells integrated, survived, and homed in the degenerated intervertebral disc. Histological grading showed that the transfected MSCs regenerated the IVD and restored normal architecture.

CONCLUSION

Genetically modified MSCs accelerate cartilage regeneration, providing a unique opportunity and impetus for stem cell-based therapeutic approach for degenerative disc diseases.

Allogeneic Stem Cell Transplantation Combined With Transfusion of Mesenchymal Stem Cells in Primary Myelofibrosis: A Multicenter Retrospective Study

BACKGROUND

Allogeneic stem cell transplantation (allo-SCT) remains the only effective curative therapy for primary myelofibrosis. Utilization and efficacy of allo-SCT are limited by lethal complications, including engraftment failure, and acute (aGVHD) and chronic graft-versus-host disease (cGVHD). Several clinical trials have explored the use of mesenchymal stem cells (MSCs) in allo-SCT to prevent hematopoietic stem cell (HSC) engraftment failure and control GVHD.

METHODS

Clinical data of 17 patients with primary myelofibrosis who underwent allo-SCT combined with ex vivo expanded MSC transfusion in four centers from February 2011 to December 2018 were retrospectively analyzed.

RESULTS

All patients received myeloablative conditioning regimen. The median number of transplanted nucleated cells (NCs) per kilogram body weight was 11.18 × 108 (range: 2.63-16.75 × 108), and the median number of CD34+ cells was 4.72 × 106 (range: 1.32-8.4 × 106). MSCs were transfused on the day of transplant or on day 7 after transplant. The median MSC infusion number was 6.5 × 106 (range: 0.011-65 × 106). None of the patients experienced primary or secondary graft failure in the study. The median time to neutrophil engraftment was 13 days (range: 11-22 days), and the median time to platelet engraftment was 21 days (range: 12-184 days). The median follow-up time was 40.3 months (range: 1.8-127.8 months). The estimated relapse-free survival (RFS) at 5 years was 79.1%, and overall survival (OS) at 5 years was 64.7%. Analysis showed that the cumulative incidence of aGVHD grade II to IV was 36% (95% CI: 8%-55%) and that of grade III to IV was 26% (95% CI: 0%-45%) at day 100. The cumulative incidence of overall cGVHD at 2 years for the entire study population was 63% (95% CI: 26%-81%). The cumulative incidence of moderate to severe cGVHD at 2 years was 17% (95% CI: 0%-42%). Seven patients died during the study, with 5 patients succumbing from non-relapse causes and 2 from disease relapse.

CONCLUSION

The findings of the study indicate that allo-SCT combined with MSC transfusion may represent an effective treatment option for primary myelofibrosis.

Promotion of Platelet Production by Co-Transplantation of Mesenchymal Stem Cells in Bone Marrow Transplantation

BACKGROUND

Therapeutic strategies that can promote platelet production are in demand to enhance clinical outcomes of bone marrow transplantation (BMT). Our research group has studied human tonsil-derived mesenchymal stem cells (T-MSCs) and their effectiveness in promoting bone marrow (BM) engraftment. Here, we analyzed the effects of T-MSCs on platelet production and hemostasis.

METHODS

Donor BM cells (BMCs) were isolated from C57BL/6 mice and transplanted with or without T-MSCs to BALB/c recipient mice. Mice were sacrificed and blood cells were counted using an Auto Hematology Analyzer. Femur sections were stained with CD41 antibody to analyze megakaryocytes in the BM. Growth factor secretion from MSCs was analyzed using the Quantibody Array. Effects of T-MSC conditioned medium (CM) on megakaryopoiesis were investigated using the MegaCult assay. In a mouse model of BMT, T-MSC CM was injected with or without anti-placental growth factor (α-PlGF) blocking antibody, and blood cell numbers and coagulation were analyzed.

RESULTS

T-MSC co-transplantation increased percent survival of BMT mice. Platelet numbers were significantly lower in the BMC-only group, whereas T-MSC co-transplantation restored circulating platelets to levels similar to those of the control group. Significantly reduced numbers of CD41 + megakaryocytes in Bu-Cy and BMC groups were increased by T-MSC co-transplantation. PlGF secretion from T-MSCs were detected and enhanced megakaryopoiesis, platelet production, and coagulation by T-MCS CM were disrupted in the presence of the α-PlGF blocking antibody.

CONCLUSION

We demonstrated the effectiveness of T-MSC co-transplantation in promoting platelet production and coagulation after BMT. These findings highlight the potential therapeutic relevance of T-MSCs for preventing thrombocytopenia after BMT.

Highlighting the interaction between immunomodulatory properties of mesenchymal stem cells and signaling pathways contribute to Graft Versus Host Disease management

Background Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) has been increasingly used as a therapeutic approach for hematological malignancies. Several potential strategies have been developed for treating or preventing allo-HSCT complications, specifically graft-versus-host disease (GVHD). GVHD could significantly affect the morbidity and mortality of patients after allo-HSCT. Curative treatment and prophylaxis regimens for GVHD could reduce GVHD incidence and improve survival rate. Among these therapeutic strategies, mesenchymal stem cell (MSCs) mediated immunomodulation has been explored widely in clinical trials. MSCs immunomodulation ability in GVHD correlates with the interactions of MSCs with innate and adaptive immune cells. However, signaling pathways responsible for MSCs' impact on GVHD regulation, like JAK/STAT, NOTCH, MAPK/ERK, and NFκβ signaling pathways, have not been clearly described yet. This review aims to illuminate the effect of MSCs-mediated immunomodulation in GVHD management after allo-HSCT representing the role of MSCs therapy on signaling pathways in GVHD. Conclusion MSCs could potentially modulate immune responses, prevent GVHD, and improve survival after allo-HSCT. Previous studies have investigated different signaling pathways' contributions to MSCs immunoregulatory ability. Accordingly, targeting signaling pathways components involved in MSCs related GVHD regulation is proven to be beneficial.

The Implications of Bone Marrow Adipose Tissue on Inflammaging

Once considered an inert filler of the bone cavity, bone marrow adipose tissue (BMAT) is now regarded as a metabolically active organ that plays versatile roles in endocrine function, hematopoiesis, bone homeostasis and metabolism, and, potentially, energy conservation. While the regulation of BMAT is inadequately understood, it is recognized as a unique and dynamic fat depot that is distinct from peripheral fat. As we age, bone marrow adipocytes (BMAds) accumulate throughout the bone marrow (BM) milieu to influence the microenvironment. This process is conceivably signaled by the secretion of adipocyte-derived factors including pro-inflammatory cytokines and adipokines. Adipokines participate in the development of a chronic state of low-grade systemic inflammation (inflammaging), which trigger changes in the immune system that are characterized by declining fidelity and efficiency and cause an imbalance between pro-inflammatory and anti-inflammatory networks. In this review, we discuss the local effects of BMAT on bone homeostasis and the hematopoietic niche, age-related inflammatory changes associated with BMAT accrual, and the downstream effect on endocrine function, energy expenditure, and metabolism. Furthermore, we address therapeutic strategies to prevent BMAT accumulation and associated dysfunction during aging. In sum, BMAT is emerging as a critical player in aging and its explicit characterization still requires further research.

Humanized Mice as a Valuable Pre-Clinical Model for Cancer Immunotherapy Research

Immunotherapy with checkpoint inhibitors opened new horizons in cancer treatment. Clinical trials for novel immunotherapies or unexplored combination regimens either need years of development or are simply impossible to perform like is the case in cancer patients with limited life expectancy. Thus, the need for preclinical models that rapidly and safely allow for a better understanding of underlying mechanisms, drug kinetics and toxicity leading to the selection of the best regimen to be translated into the clinic, is of high importance. Humanized mice that can bear both human immune system and human tumors, are increasingly used in recent preclinical immunotherapy studies and represent a remarkably unprecedented tool in this field. In this review, we describe, summarize, and discuss the recent advances of humanized mouse models used for cancer immunotherapy research and the challenges faced during their establishment. We also highlight the lack of preclinical studies using this model for radiotherapy-based research and argue that it can be a great asset to understand and answer many open questions around radiation therapy such as its presumed associated "abscopal effect".

Rebuilding the hematopoietic stem cell niche: Recent developments and future prospects

Hematopoietic stem cells (HSCs) have proven their clinical relevance in stem cell transplantation to cure patients with hematological disorders. Key to their regenerative potential is their natural microenvironment - their niche - in the bone marrow (BM). Developments in the field of biomaterials enable the recreation of such environments with increasing preciseness in the laboratory. Such artificial niches help to gain a fundamental understanding of the biophysical and biochemical processes underlying the interaction of HSCs with the materials in their environment and the disturbance of this interplay during diseases affecting the BM. Artificial niches also have the potential to multiply HSCs in vitro, to enable the targeted differentiation of HSCs into mature blood cells or to serve as drug-testing platforms. In this review, we will introduce the importance of artificial niches followed by the biology and biophysics of the natural archetype. We will outline how 2D biomaterials can be used to dissect the complexity of the natural niche into individual parameters for fundamental research and how 3D systems evolved from them. We will present commonly used biomaterials for HSC research and their applications. Finally, we will highlight two areas in the field of HSC research, which just started to unlock the possibilities provided by novel biomaterials, in vitro blood production and studying the pathophysiology of the niche in vitro. With these contents, the review aims to give a broad overview of the different biomaterials applied for HSC research and to discuss their potentials, challenges and future directions in the field. STATEMENT OF SIGNIFICANCE: Hematopoietic stem cells (HSCs) are multipotent cells responsible for maintaining the turnover of all blood cells. They are routinely applied to treat patients with hematological diseases. This high clinical relevance explains the necessity of multiplication or differentiation of HSCs in the laboratory, which is hampered by the missing natural microenvironment - the so called niche. Biomaterials offer the possibility to mimic the niche and thus overcome this hurdle. The review introduces the HSC niche in the bone marrow and discusses the utility of biomaterials in creating artificial niches. It outlines how 2D systems evolved into sophisticated 3D platforms, which opened the gateway to applications such as, expansion of clinically relevant HSCs, in vitro blood production, studying niche pathologies and drug testing.

Strategies to Improve the Quality and Freshness of Human Bone Marrow-Derived Mesenchymal Stem Cells for Neurological Diseases

Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) have been studied for their application to manage various neurological diseases, owing to their anti-inflammatory, immunomodulatory, paracrine, and antiapoptotic ability, as well as their homing capacity to specific regions of brain injury. Among mesenchymal stem cells, such as BM-MSCs, adipose-derived MSCs, and umbilical cord MSCs, BM-MSCs have many merits as cell therapeutic agents based on their widespread availability and relatively easy attainability and in vitro handling. For stem cell-based therapy with BM-MSCs, it is essential to perform ex vivo expansion as low numbers of MSCs are obtained in bone marrow aspirates. Depending on timing, before hBM-MSC transplantation into patients, after detaching them from the culture dish, cell viability, deformability, cell size, and membrane fluidity are decreased, whereas reactive oxygen species generation, lipid peroxidation, and cytosolic vacuoles are increased. Thus, the quality and freshness of hBM-MSCs decrease over time after detachment from the culture dish. Especially, for neurological disease cell therapy, the deformability of BM-MSCs is particularly important in the brain for the development of microvessels. As studies on the traditional characteristics of hBM-MSCs before transplantation into the brain are very limited, omics and machine learning approaches are needed to evaluate cell conditions with indepth and comprehensive analyses. Here, we provide an overview of hBM-MSCs, the application of these cells to various neurological diseases, and improvements in their quality and freshness based on integrated omics after detachment from the culture dish for successful cell therapy.

Intracellular density is a novel indicator of differentiation stages of murine osteoblast lineage cells

Osteoblasts are primary bone-making cells originating from mesenchymal stem cells (MSCs) in the bone marrow. The differentiation of MSCs to mature osteoblasts involves an intermediate stage called preosteoblasts, but the details of this process remain unclear. This study focused on the intracellular density of immature osteoblast lineage cells and hypothesized that the density might vary during differentiation and might be associated with the differentiation stages of osteoblast lineage cells. This study aimed to clarify the relationship between intracellular density and differentiation stages using density gradient centrifugation. Primary murine bone marrow stromal cell cultures were prepared in an osteogenic induction medium, and cells were separated into three fractions (low, intermediate, and high-density). The high-density fraction showed elevated expression of osteoblast differentiation markers (Sp7, Col1a1, Spp1, and Bglap) and low expression of MSC surface markers (Sca-1, CD73, CD105, and CD106). In contrast, the low-density fraction showed a high expression of MSC surface markers. These results indicated that intracellular density increased during differentiation from preosteoblasts to committed osteoblasts. Intracellular density may be a novel indicator for osteoblast differentiation stages. Density gradient centrifugation is a novel technique to study the process by which preosteoblasts transform into bone-forming cells.

Culture Substrates for Improved Manufacture of Mesenchymal Stromal Cell Therapies

Recent developments in mesenchymal stromal cell (MSC) therapies have increased the demand for tools to improve their manufacture, including the selection of optimal culture substrate materials. While many clinical manufacturers use planar tissue culture plastic (TCP) surfaces for MSC production, others have begun exploring the use of alternative culture substrates that present a variety of spatial, mechanical, and biochemical cues that influence cell expansion and resulting cell quality. In this review, the effects of culture and material properties distinct from traditional planar TCP surfaces on MSC proliferation, surface marker expression, and commonly used indications for therapeutic potency are examined. The different properties summarized include the use of alternative culture formats such as cellular aggregates or 3D scaffolds, as well as the effects of culture substrate stiffness and presentation of specific adhesive ligands and topographical cues. Specific substrate properties can be related to greater cell expansion and improvement in specific therapeutic functionalities, demonstrating the utility of culture materials in further improving the clinical-scale manufacture of highly secretory MSC products.

Human delta like 1-expressing human mesenchymal stromal cells promote human T cell development and antigen-specific response in humanized NOD/SCID/IL-2R[Formula: see text]null (NSG) mice

Human delta-like 1 (hDlk1) is known to be able to regulate cell fate decisions during hematopoiesis. Mesenchymal stromal cells (MSCs) are known to exhibit potent immunomodulatory roles in a variety of diseases. Herein, we investigated in vivo functions of hDlk1-hMSCs and hDlk1+hMSCs in T cell development and T cell response to viral infection in humanized NOD/SCID/IL-2Rγnull (NSG) mice. Co-injection of hDlk1-hMSC with hCD34+ cord blood (CB) cells into the liver of NSG mice markedly suppressed the development of human T cells. In contrast, co-injection of hDlk1+hMSC with hCD34+ CB cells into the liver of NSG dramatically promoted the development of human T cells. Human T cells developed in humanized NSG mice represent markedly diverse, functionally active, TCR V[Formula: see text] usages, and the restriction to human MHC molecules. Upon challenge with Epstein-Barr virus (EBV), EBV-specific hCD8+ T cells in humanized NSG mice were effectively mounted with phenotypically activated T cells presented as hCD45+hCD3+hCD8+hCD45RO+hHLA-DR+ T cells, suggesting that antigen-specific T cell response was induced in the humanized NSG mice. Taken together, our data suggest that the hDlk1-expressing MSCs can effectively promote the development of human T cells and immune response to exogenous antigen in humanized NSG mice. Thus, the humanized NSG model might have potential advantages for the development of therapeutics targeting infectious diseases in the future.

Mesenchymal stromal cells in hematopoietic cell transplantation

Mesenchymal stromal cells (MSCs) are widely recognized to possess potent immunomodulatory activity, as well as to stimulate repair and regeneration of diseased or damaged tissue. These fundamental properties suggest important applications in hematopoietic cell transplantation. Although the mechanisms of therapeutic activity in vivo are yet to be fully elucidated, MSCs seem to suppress lymphocytes by paracrine mechanisms, including secreted mediators and metabolic modulators. Most recently, host macrophage engulfment of apoptotic MSCs has emerged as an important contributor to the immune suppressive microenvironment. Although bone marrow-derived MSCs are the most commonly studied, the tissue source of MSCs may be a critical determinant of immunomodulatory function. The key application of MSC therapy in hematopoietic cell transplantation is to prevent or treat graft-versus-host disease (GVHD). The pathogenesis of GVHD reveals multiple potential targets. Moreover, the recently proposed concept of tissue tolerance suggests a new possible mechanism of MSC therapy for GVHD. Beyond GVHD, MSCs may facilitate hematopoietic stem cell engraftment, which could gain greater importance with increasing use of haploidentical transplantation. Despite many challenges and much doubt, commercial MSC products for pediatric steroid-refractory GVHD have been licensed in Japan, conditionally licensed in Canada and New Zealand, and have been recommended for approval by an FDA Advisory Committee in the United States. Here, we review key historical data in the context of the most salient recent findings to present the current state of MSCs as adjunct cell therapy in hematopoietic cell transplantation.

Role of ex vivo Expanded Mesenchymal Stromal Cells in Determining Hematopoietic Stem Cell Transplantation Outcome

Overall, the human organism requires the production of ∼1 trillion new blood cells per day. Such goal is achieved via hematopoiesis occurring within the bone marrow (BM) under the tight regulation of hematopoietic stem and progenitor cell (HSPC) homeostasis made by the BM microenvironment. The BM niche is defined by the close interactions of HSPCs and non-hematopoietic cells of different origin, which control the maintenance of HSPCs and orchestrate hematopoiesis in response to the body’s requirements. The activity of the BM niche is regulated by specific signaling pathways in physiological conditions and in case of stress, including the one induced by the HSPC transplantation (HSCT) procedures. HSCT is the curative option for several hematological and non-hematological diseases, despite being associated with early and late complications, mainly due to a low level of HSPC engraftment, impaired hematopoietic recovery, immune-mediated graft rejection, and graft-versus-host disease (GvHD) in case of allogenic transplant. Mesenchymal stromal cells (MSCs) are key elements of the BM niche, regulating HSPC homeostasis by direct contact and secreting several paracrine factors. In this review, we will explore the several mechanisms through which MSCs impact on the supportive activity of the BM niche and regulate HSPC homeostasis. We will further discuss how the growing understanding of such mechanisms have impacted, under a clinical point of view, on the transplantation field. In more recent years, these results have instructed the design of clinical trials to ameliorate the outcome of HSCT, especially in the allogenic setting, and when low doses of HSPCs were available for transplantation.

MSCs and Inflammatory Cells Crosstalk in Regenerative Medicine: Concerted Actions for Optimized Resolution Driven by Energy Metabolism

Mesenchymal stromal cells (MSCs) are currently widely used in cell based therapy regarding to their remarkable efficacy in controlling the inflammatory status in patients. Despite recent progress and encouraging results, inconstant therapeutic benefits are reported suggesting that significant breakthroughs in the understanding of MSCs immunomodulatory mechanisms of action remains to be investigated and certainly apprehended from original point of view. This review will focus on the recent findings regarding MSCs close relationship with the innate immune compartment, i.e. granulocytes and myeloid cells. The review will also consider the intercellular mechanism of communication involved, such as factor secretion, cell-cell contact, extracellular vesicles, mitochondria transfer and efferocytosis. Immune-like-properties of MSCs supporting part of their therapeutic effect in the clinical setting will be discussed, as well as their potentials (immunomodulatory, anti-bacterial, anti-inflammatory, anti-oxidant defenses and metabolic adaptation…) and effects mediated, such as cell polarization, differentiation, death and survival on various immune and tissue cell targets determinant in triggering tissue regeneration. Their metabolic properties in term of sensing, reacting and producing metabolites influencing tissue inflammation will be highlighted. The review will finally open to discussion how ongoing scientific advances on MSCs could be efficiently translated to clinic in chronic and age-related inflammatory diseases and the current limits and gaps that remain to be overcome to achieving tissue regeneration and rejuvenation.

Nasal Turbinate Mesenchymal Stromal Cells Preserve Characteristics of Their Neural Crest Origin and Exert Distinct Paracrine Activity

The sources of mesenchymal stromal cells (MSCs) for cell therapy trials are expanding, increasing the need for their characterization. Here, we characterized multi-donor, turbinate-derived MSCs (TB-MSCs) that develop from the neural crest, and compared them to bone marrow-derived MSCs (BM-MSCs). TB-MSCs had higher proliferation potential and higher self-renewal of colony forming cells, but lower potential for multi-lineage differentiation than BM-MSCs. TB-MSCs expressed higher levels of neural crest markers and lower levels of pericyte-specific markers. These neural crest-like properties of TB-MSCs were reflected by their propensity to differentiate into neuronal cells and proliferative response to nerve growth factors. Proteomics (LC-MS/MS) analysis revealed a distinct secretome profile of TB-MSCs compared to BM and adipose tissue-derived MSCs, exhibiting enrichments of factors for cell-extracellular matrix interaction and neurogenic signaling. However, TB-MSCs and BM-MSCs exhibited comparable suppressive effects on the allo-immune response and comparable stimulatory effects on hematopoietic stem cell self-renewal. In contrast, TB-MSCs stimulated growth and metastasis of breast cancer cells more than BM-MSCs. Altogether, our multi-donor characterization of TB-MSCs reveals distinct cell autonomous and paracrine properties, reflecting their unique developmental origin. These findings support using TB-MSCs as an alternative source of MSCs with distinct biological characteristics for optimal applications in cell therapy.

Potential Use of Mesenchymal Multipotent Cells for Hemopoietic Stem Cell Transplantation: Pro and Contra

The potential of mesenchymal multipotent (stem) cells (MSC) to modify immune reactions and mediate hematopoiesis boosted great interest for their use in allogeneic hemopoietic stem cell transplantation. Because of MSC production of a wide range of cytokines and growth factors, these cells are included in the therapy of graft-versus-host disease (GVHD). A number of clinical studies have demonstrated safety and efficacy of MSC-based therapy in acute GVHD. Japan and some other countries approved biomedical cell products on the base of allogeneic bone marrow (BM) MSCs as medical agents for acute GVHD treatment. Besides, MSCs may form BM stroma and improve hematopoiesis. Simultaneous transplantation of hematopoietic stem cells and MSCs effectively improved engraftment and prevented GVHD in transplantation of umbilical cord blood and human leukocyte antigens-incompatible BM stem cells. The review presents the analysis of clinical studies of MSCs in allogeneic hematopoietic stem cell transplantation and discusses different approaches for improvement of MSC-based GVHD treatment and prophylaxis.

Leonurine Promotes the Osteoblast Differentiation of Rat BMSCs by Activation of Autophagy via the PI3K/Akt/mTOR Pathway

Background

Leonurine, a major bioactive component from Herba leonuri, has been shown to exhibit anti-inflammatory and antioxidant effects. The aim of this study was to investigate the effect of leonurine on bone marrow-derived mesenchymal stem cells (BMSCs) as a therapeutic approach for treating osteoporosis.

Materials and Methods

Rat bone marrow-derived mesenchymal stem cells (rBMSCs) were isolated from 4-weeks-old Sprague–Dawley rats. The cytocompatibility of leonurine on rBMSCs was tested via CCK-8 assays and flow cytometric analyses. The effects of leonurine on rBMSC osteogenic differentiation were analyzed via ALP staining, Alizarin red staining, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blot. Additionally, autophagy-related markers were examined via qRT-PCR and Western blot analyses of rBMSCs during osteogenic differentiation with leonurine and with or without 3-methyladenine (3-MA) as an autophagic inhibitor. Finally, the PI3K/Akt/mTOR signaling pathway was evaluated during rBMSC osteogenesis.

Results

Leonurine at 2–100 μM promoted the proliferation of rBMSCs. ALP and Alizarin red staining results showed that 10 μM leonurine promoted rBMSC osteoblastic differentiation, which was consistent with the qRT-PCR and Western blot results. Compared with those of the control group, the mRNA and protein levels of Atg5, Atg7, and LC3 were upregulated in the rBMSCs upon leonurine treatment. Furthermore, leonurine rescued rBMSC autophagy after inhibition by 3-MA. Additionally, the PI3K/AKT/mTOR pathway was activated in rBMSCs upon leonurine treatment.

Conclusion

Leonurine promotes the osteoblast differentiation of rBMSCs by activating autophagy, which depends on the PI3K/Akt/mTOR pathway. Our results suggest that leonurine may be a potential treatment for osteoporosis.

The Potential of Mesenchymal Stromal Cells in Neuroblastoma Therapy for Delivery of Anti-Cancer Agents and Hematopoietic Recovery

Neuroblastoma is one of the most common pediatric cancers and a major cause of cancer-related death in infancy. Conventional therapies including high-dose chemotherapy, stem cell transplantation, and immunotherapy approach a limit in the treatment of high-risk neuroblastoma and prevention of relapse. In the last two decades, research unraveled a potential use of mesenchymal stromal cells in tumor therapy, as tumor-selective delivery vehicles for therapeutic compounds and oncolytic viruses and by means of supporting hematopoietic stem cell transplantation. Based on pre-clinical and clinical advances in neuroblastoma and other malignancies, we assess both the strong potential and the associated risks of using mesenchymal stromal cells in the therapy for neuroblastoma. Furthermore, we examine feasibility and safety aspects and discuss future directions for harnessing the advantageous properties of mesenchymal stromal cells for the advancement of therapy success.

Metabolism and chromatin: A dynamic duo that regulates development and ageing: Elucidating the metabolism-chromatin axis in bone-marrow mesenchymal stem cell fate decisions

Bone-marrow mesenchymal stem cell (BM-MSC) proliferation and lineage commitment are under the coordinated control of metabolism and epigenetics; the MSC niche contains low oxygen, which is an important determinant of the cellular metabolic state. In turn, metabolism drives stem cell fate decisions via alterations of the chromatin landscape. Due to the fundamental role of BM-MSCs in the development of adipose tissue, bones and cartilage, age-associated changes in metabolism and the epigenome perturb the balance between stem cell proliferation and differentiation leading to stem cell depletion, fat accumulation and bone-quality related diseases. Therefore, understanding the dynamics of the metabolism-chromatin interplay is crucial for maintaining the stem cell pool and delaying the development and progression of ageing. This review summarizes the current knowledge on the role of metabolism in stem cell identity and highlights the impact of the metabolic inputs on the epigenome, with regards to stemness and pluripotency.

Advances in mesenchymal stem cell transplantation for the treatment of osteoporosis

Osteoporosis is a systemic metabolic bone disease with characteristics of bone loss and microstructural degeneration. The personal and societal costs of osteoporosis are increasing year by year as the ageing of population, posing challenges to public health care. Homing disorders, impaired capability of osteogenic differentiation, senescence of mesenchymal stem cells (MSCs), an imbalanced microenvironment, and disordered immunoregulation play important roles during the pathogenesis of osteoporosis. The MSC transplantation promises to increase osteoblast differentiation and block osteoclast activation, and to rebalance bone formation and resorption. Preclinical investigations on MSC transplantation in the osteoporosis treatment provide evidences of enhancing osteogenic differentiation, increasing bone mineral density, and halting the deterioration of osteoporosis. Meanwhile, the latest techniques, such as gene modification, targeted modification and co-transplantation, are promising approaches to enhance the therapeutic effect and efficacy of MSCs. In addition, clinical trials of MSC therapy to treat osteoporosis are underway, which will fill the gap of clinical data. Although MSCs tend to be effective to treat osteoporosis, the urgent issues of safety, transplant efficiency and standardization of the manufacturing process have to be settled. Moreover, a comprehensive evaluation of clinical trials, including safety and efficacy, is still needed as an important basis for clinical translation.

Bone marrow stromal cell therapy improves survival after radiation injury but does not restore endogenous hematopoiesis

The only available option to treat radiation-induced hematopoietic syndrome is allogeneic hematopoietic cell transplantation, a therapy unavailable to many patients undergoing treatment for malignancy, which would also be infeasible in a radiological disaster. Stromal cells serve as critical components of the hematopoietic stem cell niche and are thought to protect hematopoietic cells under stress. Prior studies that have transplanted mesenchymal stromal cells (MSCs) without co-administration of a hematopoietic graft have shown underwhelming rescue of endogenous hematopoiesis and have delivered the cells within 24 h of radiation exposure. Herein, we examine the efficacy of a human bone marrow-derived MSC therapy delivered at 3 h or 30 h in ameliorating radiation-induced hematopoietic syndrome and show that pancytopenia persists despite MSC therapy. Animals exposed to radiation had poorer survival and experienced loss of leukocytes, platelets, and red blood cells. Importantly, mice that received a therapeutic dose of MSCs were significantly less likely to die but experienced equivalent collapse of the hematopoietic system. The cause of the improved survival was unclear, as complete blood counts, splenic and marrow cellularity, numbers and function of hematopoietic stem and progenitor cells, and frequency of niche cells were not significantly improved by MSC therapy. Moreover, human MSCs were not detected in the bone marrow. MSC therapy reduced crypt dropout in the small intestine and promoted elevated expression of growth factors with established roles in gut development and regeneration, including PDGF-A, IGFBP-3, IGFBP-2, and IGF-1. We conclude that MSC therapy improves survival not through overt hematopoietic rescue but by positive impact on other radiosensitive tissues, such as the intestinal mucosa. Collectively, these data reveal that MSCs could be an effective countermeasure in cancer patients and victims of nuclear accidents but that MSCs alone do not significantly accelerate or contribute to recovery of the blood system.

New Insights on the Role of the Mesenchymal-Hematopoietic Stem Cell Axis in Autologous and Allogeneic Hematopoiesis

Cytoreductive protocols are integral both as conditioning regimens for bone marrow (BM) transplantation and as part of therapies for malignancies, but their associated comorbidities represent a long-standing clinical problem. In particular, they cause myeloablation that debilitates the physiological role of mesenchymal stem and precursor cells (MSPCs) in sustaining hematopoiesis. This review addresses the damaging impact of cytoreductive regimens on MSPCs. In addition, it discusses prospects for alleviating the resulting iatrogenic comorbidities. New insights into the structural and functional dynamics of hematopoietic stem cell (HSC) niches reveal the existence of "empty" niches and the ability of the donor-derived healthy HSCs to outcompete the defective HSCs in occupying these niches. These findings support the notion that conditioning regimens, conventionally used to ablate the recipient hematopoiesis to create space for engraftment of the donor-derived HSCs, may not be a necessity for allogeneic BM transplantation. In addition, the capacity of the MSPCs to cross-talk with HSCs, despite major histocompatibility complex disparity, and suppress graft versus host disease indicates the possibility for development of a conditioning-free, MSPCs-enhanced protocol for BM transplantation. The clinical advantage of supplementing cytoreductive protocols with MSPCs to improve autologous hematopoiesis reconstitution and alleviate cytopenia associated with chemo and radiation therapies for cancer is also discussed.

Phase I clinical trial of intra-bone marrow cotransplantation of mesenchymal stem cells in cord blood transplantation

Mesenchymal stem cells (MSCs) have immunomodulatory properties and support hematopoiesis in the bone marrow (BM). To develop a new strategy to not only prevent graft‐vs‐host disease (GVHD) but also to enhance engraftment, a phase I trial of cord blood transplantation (CBT) combined with intra‐BM injection of MSCs (MSC‐CBT) was designed. Third‐party BM‐derived MSCs were injected intra‐BM on the day of CBT. The conditioning regimen varied according to patient characteristics. GVHD prophylaxis was tacrolimus and methotrexate. The primary endpoint was toxicity related to intra‐BM injection of MSCs. Clinical outcomes were compared with those of six controls who received CBT alone. Five adult patients received MSC‐CBT, and no adverse events related to intra‐BM injection of MSCs were observed. All patients achieved neutrophil, reticulocyte, and platelet recoveries, with median times to recoveries of 21, 35, and 38 days, respectively, comparable with controls. Grade II‐IV acute GVHD developed in three controls but not in MSC‐CBT patients. No patients developed chronic GVHD in both groups. At 1 year after transplantation, all MSC‐CBT patients survived without relapse. This study shows the safety of MSC‐CBT, and the findings also suggest that cotransplantation of MSCs may prevent GVHD with no inhibition of engraftment. This trial was registered at the University Hospital Medical Information Network Clinical Trials Registry as number 000024291.

Allogeneic human umbilical cord Wharton's jelly stem cells increase several-fold the expansion of human cord blood CD34+ cells both in vitro and in vivo

Background

The transplantation of human umbilical cord blood (UCB) CD34+ cells has been successfully used to treat hematological disorders but one major limitation has been the low cell numbers available. Mesenchymal stem cells (MSCs) lying within the bone marrow in vivo behave like a scaffold on which CD34+ cells interact and proliferate. We therefore evaluated the use of allogeneic MSCs from the human UC Wharton’s jelly (hWJSCs) as stromal support for the ex vivo expansion of CD34+ cells.

Methods

We performed an in-depth evaluation of the primitiveness, migration, adhesion, maturation, mitochondrial behavior, and pathway mechanisms of this platform using conventional assays followed by the evaluation of engraftment potential of the expanded CD34+ cells in an in vivo murine model.

Results

We demonstrate that hWJSCs and its conditioned medium (hWJSC-CM) support the production of significantly high fold changes of CD34+, CD34+CD133+, CD34+CD90+, CD34+ALDH+, CD34+CD45+, and CD34+CD49f+ cells after 7 days of interaction when compared to controls. In the presence of hWJSCs or hWJSC-CM, the CD34+ cells produced significantly more primitive CFU-GEMM colonies, HoxB4, and HoxA9 gene expression and lower percentages of CD34+CXCR4+ cells. There were also significantly higher N-cadherin+ cell numbers and increased cell migration in transwell migration assays. The CD34+ cells expanded with hWJSCs had significantly lower mitochondrial mass, mitochondrial membrane potential, and oxidative stress. Green Mitotracker-tagged mitochondria from CD34+ cells were observed lying within red CellTracker-tagged hWJSCs under confocal microscopy indicating mitochondrial transfer via tunneling nanotubes. CD34+ cells expanded with hWJSCs and hWJSC-CM showed significantly reduced oxidative phosphorylation (ATP6VIH and NDUFA10) and increased glycolytic (HIF-1a and HK-1) pathway-related gene expression. CD34+ cells expanded with hWJSCs for 7 days showed significant greater CD45+ cell chimerism in the bone marrow of primary and secondary irradiated mice when transplanted intravenously.

Conclusions

In this report, we confirmed that allogeneic hWJSCs provide an attractive platform for the ex vivo expansion of high fold numbers of UCB CD34+ cells while keeping them primitive. Allogeneic hWJSCs are readily available in abundance from discarded UCs, can be easily frozen in cord blood banks, thawed, and then used as a platform for UCB-HSC expansion if numbers are inadequate.

Co-transplantation of mesenchymal stem cells makes haploidentical HSCT a potential comparable therapy with matched sibling donor HSCT for patients with severe aplastic anemia

The application of haploidentical hematopoietic stem cell transplantation (HSCT) with mesenchymal stem cell (MSC) infusion as a treatment regimen for severe aplastic anemia (SAA) has been reported to be efficacious in single-arm trials. However, it is difficult to assess without comparing the results with those from a first-line, matched-sibling HSCT. Herein, we retrospectively reviewed 91 patients with acquired SAA. They received HSCT from haploidentical donors combined with MSC transfer (HID group). We compared these patients with 103 others who received first-line matched-sibling HSCT (MSD group) to evaluate relative treatment efficacy. Compared with the patients in the MSD group, those in the HID group presented with higher incidences of grades II–IV and III–IV acute graft versus host disease (aGvHD) and chronic graft versus host disease (cGvHD) (p < 0.05). However, the incidence of myeloid and platelet engraftment, graft failure, poor graft function, and extensive cGvHD were comparable for both groups. The median follow-up was 36.6 months and the 3-year overall survival rate was similar for both groups (83.5% versus 79.1%). Univariate and multivariate analyses revealed that time intervals greater than 4 months from diagnosis to transplantation, experienced graft failure, poor graft function, or grade III–IV aGvHD were significantly associated with adverse outcomes. All HID patients received MSC co-transplantation with hematopoietic stem cells. However, the infused MSCs were derived from umbilical cord (UC-MSC group; 43 patients) or bone marrow (BM-MSC group; 48 patients) and were administered at different medical centers. We first compared the outcomes between the two groups and detected that the BM-MSC group exhibited lower incidences of grade III–IV aGvHD and cGvHD (p < 0.05). This study suggests that co-transplantation of hematopoietic and MSCs significantly reduces the risk and incidence of graft rejection and may effectively improve overall survival in patients with SAA even in the absence of closely related histocompatible donor material.

Effect of the 3D Artificial Nichoid on the Morphology and Mechanobiological Response of Mesenchymal Stem Cells Cultured In Vitro

Stem cell fate and behavior are affected by the bidirectional communication of cells and their local microenvironment (the stem cell niche), which includes biochemical cues, as well as physical and mechanical factors. Stem cells are normally cultured in conventional two-dimensional monolayer, with a mechanical environment very different from the physiological one. Here, we compare culture of rat mesenchymal stem cells on flat culture supports and in the "Nichoid", an innovative three-dimensional substrate micro-engineered to recapitulate the architecture of the physiological niche in vitro. Two versions of the culture substrates Nichoid (single-layered or "2D Nichoid" and multi-layered or "3D Nichoid") were fabricated via two-photon laser polymerization in a biocompatible hybrid organic-inorganic photoresist (SZ2080). Mesenchymal stem cells, isolated from rat bone marrow, were seeded on flat substrates and on 2D and 3D Nichoid substrates and maintained in culture up to 2 weeks. During cell culture, we evaluated cell morphology, proliferation, cell motility and the expression of a panel of 89 mesenchymal stem cells' specific genes, as well as intracellular structures organization. Our results show that mesenchymal stem cells adhered and grew in the 3D Nichoid with a comparable proliferation rate as compared to flat substrates. After seeding on flat substrates, cells displayed large and spread nucleus and cytoplasm, while cells cultured in the 3D Nichoid were spatially organized in three dimensions, with smaller and spherical nuclei. Gene expression analysis revealed the upregulation of genes related to stemness and to mesenchymal stem cells' features in Nichoid-cultured cells, as compared to flat substrates. The observed changes in cytoskeletal organization of cells cultured on 3D Nichoids were also responsible for a different localization of the mechanotransducer transcription factor YAP, with an increase of the cytoplasmic retention in cells cultured in the 3D Nichoid. This difference could be explained by alterations in the import of transcription factors inside the nucleus due to the observed decrease of mean nuclear pore diameter, by transmission electron microscopy. Our data show that 3D distribution of cell volume has a profound effect on mesenchymal stem cells structure and on their mechanobiological response, and highlight the potential use of the 3D Nichoid substrate to strengthen the potential effects of MSC in vitro and in vivo.

The humanized mouse: Emerging translational potential

The humanized mouse (HM) has emerged as a valuable animal model in cancer research. Engrafted with components of a human immune system and subsequently implanted with tumor tissue from cell lines or in the form of patient-derived xenografts, the HM provides a unique platform in which the tumor microenvironment (TME) can be evaluated in vivo. This model may also be beneficial in the assessment of potential cancer treatments including immune checkpoint inhibitors. However, to maximize its utility, researchers need to understand the critical factors necessary to ensure that the tumor immune interactions in the HM are representative of those within cancer patients. In most current HM models, the human T cells residing in the HM are educated in a murine thymus, allogeneic to implanted tumor tissue, and/or alloreactive to mouse tissues, making their interaction and reactivity with tumor cells suspect. There are several strategies underway to harmonize the immune-tumor environment in the HM. Once the essential components of the HM-tumor TME interface have been identified and understood, the HM model will permit not only the discovery of effective immunotherapy treatments, but it can be used to predict patient responses to great clinical benefit.

Human adipose-derived stem cells support lymphangiogenesis in vitro by secretion of lymphangiogenic factors

Lymphedema is a chronic progressive disease ultimately resulting in severe, disfiguring swelling and permanent changes of the affected tissues. Presently, there is no causal treatment approach of lymphedema. Therefore, most therapies are purely symptomatic. However, the recent use of stem cell-based therapies has offered new prospects for alternative treatment options. The present study was performed to investigate the effects of human adipose-derived stem cells (ADSCs) on human dermal lymphatic endothelial cells (HDLECs) in terms of basic in vitro lymphangiogenic assays (WST-8 assay, scratch assay, transmigration assay, sprouting assay, tube formation assay). The influence of ADSC-conditioned medium (ADSC-CM) on HDLECs was compared to recombinant VEGF-C, bFGF and HGF. Further ADSC-CM was characterized by protein microarray and enzyme-linked immunosorbent assay (ELISA). Although key-lymphangiogenic growth factors - like VEGF-C - could only be detected in low concentrations within the conditioned medium (CM), HDLECs were potently stimulated to proliferate, migrate and to form tube like structures by ADSC-CM. Despite concentrations more than hundredfold higher than those found in the conditioned medium, stimulation with recombinant VEGF-C, bFGF and HGF was still weaker compared to ADSC-CM. These results highlight the effectiveness of growth factors secreted by ADSC to stimulate HDLEC, potentially providing a promising new therapeutic approach for the treatment of lymphedema.

Potential of mesenchymal- and cardiac progenitor cells for therapeutic targeting of B-cells and antibody responses in end-stage heart failure

Upon myocardial damage, the release of cardiac proteins induces a strong antibody-mediated immune response, which can lead to adverse cardiac remodeling and eventually heart failure (HF). Stem cell therapy using mesenchymal stromal cells (MSCs) or cardiomyocyte progenitor cells (CPCs) previously showed beneficial effects on cardiac function despite low engraftment in the heart. Paracrine mediators are likely of great importance, where, for example, MSC-derived extracellular vesicles (EVs) also show immunosuppressive properties in vitro. However, the limited capacity of MSCs to differentiate into cardiac cells and the sufficient scaling of MSC-derived EVs remain a challenge to clinical translation. Therefore, we investigated the immunosuppressive actions of endogenous CPCs and CPC-derived EVs on antibody production in vitro, using both healthy controls and end-stage HF patients. Both MSCs and CPCs strongly inhibit lymphocyte proliferation and antibody production in vitro. Furthermore, CPC-derived EVs significantly lowered the levels of IgG1, IgG4, and IgM, especially when administered for longer duration. In line with previous findings, plasma cells of end-stage HF patients showed high production of IgG3, which can be inhibited by MSCs in vitro. MSCs and CPCs inhibit in vitro antibody production of both healthy and end-stage HF-derived immune cells. CPC-derived paracrine factors, such as EVs, show similar effects, but do not provide the complete immunosuppressive capacity of CPCs. The strongest immunosuppressive effects were observed using MSCs, suggesting that MSCs might be the best candidates for therapeutic targeting of B-cell responses in HF.

Oxygen Disrupts Human Fetal Lung Mesenchymal Cells. Implications for Bronchopulmonary Dysplasia

Exogenous mesenchymal stromal cells (MSCs) ameliorate experimental bronchopulmonary dysplasia. Moreover, data from term-born animal models and human tracheal aspirate-derived cells suggest altered mesenchymal signaling in the pathophysiology of neonatal lung disease. We hypothesized that hyperoxia, a factor contributing to the development of bronchopulmonary dysplasia, perturbs human lung-resident MSC function. Mesenchymal cells were isolated from human fetal lung tissue (16-18 wk of gestation), characterized and cultured in conditions resembling either intrauterine (5% O₂) or extrauterine (21% and 60% O₂) atmospheres. Secretome data were compared with MSCs obtained from term umbilical cord tissues. The human fetal lung mesenchyme almost exclusively contains CD146^pos. MSCs expressing SOX-2 and OCT-4, which secrete elastin, fibroblast growth factors 7 and 10, vascular endothelial growth factor, angiogenin, and other lung cell-protecting/-maturing proteins. Exposure to extrauterine atmospheres in vitro leads to excessive proliferation, reduced colony-forming ability, alterations in the cell's surface marker profile, decreased elastin deposition, and impaired secretion of factors important for lung growth. Conversely, umbilical cord-derived MSCs abundantly secreted factors that impaired lung MSCs are unable to produce. Oxygen-impaired human fetal lung MSC function may contribute to disrupted repair capacity and arrested lung growth. Exogenous MSCs may act by triggering the signaling pathways lost by impaired endogenous lung mesenchymal cells.

Bone Marrow-Derived Mesenchymal Stromal Cells: A Novel Target to Optimize Hematopoietic Stem Cell Transplantation Protocols in Hematological Malignancies and Rare Genetic Disorders

: Mesenchymal stromal cells (MSCs) are crucial elements in the bone marrow (BM) niche where they provide physical support and secrete soluble factors to control and maintain hematopoietic stem progenitor cells (HSPCs). Given their role in the BM niche and HSPC support, MSCs have been employed in the clinical setting to expand ex-vivo HSPCs, as well as to facilitate HSPC engraftment in vivo. Specific alterations in the mesenchymal compartment have been described in hematological malignancies, as well as in rare genetic disorders, diseases that are amenable to allogeneic hematopoietic stem cell transplantation (HSCT), and ex-vivo HSPC-gene therapy (HSC-GT). Dissecting the in vivo function of human MSCs and studying their biological and functional properties in these diseases is a critical requirement to optimize transplantation outcomes. In this review, the role of MSCs in the orchestration of the BM niche will be revised, and alterations in the mesenchymal compartment in specific disorders will be discussed, focusing on the need to correct and restore a proper microenvironment to ameliorate transplantation procedures, and more in general disease outcomes.