Empowering the immune fate of bone marrow mesenchymal stromal cells: gene and protein changes

The immunogenic profile and immunomodulatory function of mesenchymal stromal / stem cells in the presence of Ptychotis verticillata

Mesenchymal stromal/stem cells (MSCs) are considered to be a promising immunotherapeutic tool due to their easy accessibility, culture expansion possibilities, safety profile, and immunomodulatory properties. Although several studies have demonstrated the therapeutic effects of MSCs, their efficacy needs to be improved while also preserving their safety. It has been suggested that cell homeostasis may be particularly sensitive to plant extracts. The impact of natural compounds on immunity is thus a fascinating and growing field. Ptychotis verticillata and its bioactive molecules, carvacrol and thymol, are potential candidates for improving MSC therapeutic effects. They can be used as immunotherapeutic agents to regulate MSC functions and behavior during immunomodulation. Depending on their concentrations and incubation time, these compounds strengthened the immunomodulatory functions of MSCs while maintaining their immune-evasive profile. Incubating MSCs with carvacrol and thymol does not alter their hypoimmunogenicity, as no induction of the allogeneic immune response was observed. MSCs also showed enhanced abilities to reduce the proliferation of activated T cells. Thus, MSCs are immunologically responsive to bioactive molecules derived from PV. The bioactivity may depend on the whole phyto-complex of the oil. These findings may contribute to the development of safe and efficient immunotherapeutic MSCs by using medicinal plant-derived active molecules.

Influence of Bone Substitutes on Mesenchymal Stromal Cells in an Inflammatory Microenvironment

Bone regeneration is driven by mesenchymal stromal cells (MSCs) via their interactions with immune cells, such as macrophages (MPs). Bone substitutes, e.g., bi-calcium phosphates (BCPs), are commonly used to treat bone defects. However, little research has focused on MSC responses to BCPs in the context of inflammation. The objective of this study was to investigate whether BCPs influence MSC responses and MSC-MP interactions, at the gene and protein levels, in an inflammatory microenvironment. In setup A, human bone marrow MSCs combined with two different BCP granules (BCP 60/40 or BCP 20/80) were cultured with or without cytokine stimulation (IL1β + TNFα) to mimic acute inflammation. In setup B, U937 cell-line-derived MPs were introduced via transwell cocultures to setup A. Monolayer MSCs with and without cytokine stimulation served as controls. After 72 h, the expressions of genes related to osteogenesis, healing, inflammation and remodeling were assessed in the MSCs via quantitative polymerase chain reactions. Additionally, MSC-secreted cytokines related to healing, inflammation and chemotaxis were assessed via multiplex immunoassays. Overall, the results indicate that, under both inflammatory and non-inflammatory conditions, the BCP granules significantly regulated the MSC gene expressions towards a pro-healing genotype but had relatively little effect on the MSC secretory profiles. In the presence of the MPs (coculture), the BCPs positively regulated both the gene expression and cytokine secretion of the MSCs. Overall, similar trends in MSC responses were observed with BCP 60/40 and BCP 20/80. In summary, within the limits of in vitro models, these findings suggest that the presence of BCP granules at a surgical site may not necessarily have a detrimental effect on MSC-mediated wound healing, even in the event of inflammation.

Differential immunomodulation of human Mesenchymal Stromal Cells from various sources in an inflammation mimetic milieu

Mesenchymal stromal cells (MSCs) are very advantageous in the field of regenerative medicine because of their immunomodulatory properties. However, reports show that these properties vary from source to source. Hence, understanding the source-dependent specificity of MSCs and their immunomodulatory abilities will enable optimal use of MSCs in cell-based therapies. Here, we studied human MSCs from three different sources, adipose tissue (AT), bone marrow (BM) and Wharton's jelly (WJ), with respect to phenotypic responses of human peripheral blood mononuclear immune cells (hPBMCs/MNCs) and the concurrent changes in cytokine expression in MSCs, under mitogen-stimulated co-culture conditions. We used cytometric analysis to study the immunoregulatory properties of MSCs on MNCs and cytokine profiling of MSCs using a customized PCR array and solid-phase sandwich enzyme-linked immunosorbent assay. Our results reveal differential modulation of immune cells as well as MSCs upon activation by the mitogen phytohemagglutinin, independently and in co-culture. Notably, we observed source-specific MSC-cytokine signatures under stimulated conditions. Our results show that AT-MSCs up-regulate VEGF, BM-MSCs up-regulate PTGS-2 and WJ-MSCs increase expression of IDO considerably compared with controls. This remarkable modulation in source-specific cytokine expression was also validated at a functional level by quantitative protein expression studies. In our hands, even though MSCs from AT, BM and WJ sources exhibit characteristic immunomodulatory properties, our results highlight that MSCs sourced from different tissues may exhibit unique cytokine signatures and thus may be suitable for specific regenerative applications.

Bone Marrow Microenvironment in Light-Chain Amyloidosis: In Vitro Expansion and Characterization of Mesenchymal Stromal Cells

Immunoglobulin light-chain amyloidosis (AL) is caused by misfolded light chains produced by a small B cell clone. Mesenchymal stromal cells (MSCs) have been reported to affect plasma cell behavior. We aimed to characterize bone marrow (BM)-MSCs from AL patients, considering functional aspects, such as proliferation, differentiation, and immunomodulatory capacities. MSCs were in vitro expanded from the BM of 57 AL patients and 14 healthy donors (HDs). MSC surface markers were analyzed by flow cytometry, osteogenic and adipogenic differentiation capacities were in vitro evaluated, and co-culture experiments were performed in order to investigate MSC immunomodulatory properties towards the ALMC-2 cell line and HD peripheral blood mononuclear cells (PBMCs). AL-MSCs were comparable to HD-MSCs for morphology, immune-phenotype, and differentiation capacities. AL-MSCs showed a reduced proliferation rate, entering senescence at earlier passages than HD-MSCs. The AL-MSC modulatory effect on the plasma-cell line or circulating plasma cells was comparable to that of HD-MSCs. To our knowledge, this is the first study providing a comprehensive characterization of AL-MSCs. It remains to be defined if the observed abnormalities are the consequence of or are involved in the disease pathogenesis. BM microenvironment components in AL may represent the targets for the prevention/treatment of the disease in personalized therapies.

The Therapeutic Potential of Mesenchymal Stromal Cells for Regenerative Medicine: Current Knowledge and Future Understandings

In recent decades, research on the therapeutic potential of progenitor cells has advanced considerably. Among progenitor cells, mesenchymal stromal cells (MSCs) have attracted significant interest and have proven to be a promising tool for regenerative medicine. MSCs are isolated from various anatomical sites, including bone marrow, adipose tissue, and umbilical cord. Advances in separation, culture, and expansion techniques for MSCs have enabled their large-scale therapeutic application. This progress accompanied by the rapid improvement of transplantation practices has enhanced the utilization of MSCs in regenerative medicine. During tissue healing, MSCs may exhibit several therapeutic functions to support the repair and regeneration of injured tissue. The process underlying these effects likely involves the migration and homing of MSCs, as well as their immunotropic functions. The direct differentiation of MSCs as a cell replacement therapeutic mechanism is discussed. The fate and behavior of MSCs are further regulated by their microenvironment, which may consequently influence their repair potential. A paracrine pathway based on the release of different messengers, including regulatory factors, chemokines, cytokines, growth factors, and nucleic acids that can be secreted or packaged into extracellular vesicles, is also implicated in the therapeutic properties of MSCs. In this review, we will discuss relevant outcomes regarding the properties and roles of MSCs during tissue repair and regeneration. We will critically examine the influence of the local microenvironment, especially immunological and inflammatory signals, as well as the mechanisms underlying these therapeutic effects. Importantly, we will describe the interactions of local progenitor and immune cells with MSCs and their modulation during tissue injury. We will also highlight the crucial role of paracrine pathways, including the role of extracellular vesicles, in this healing process. Moreover, we will discuss the therapeutic potential of MSCs and MSC-derived extracellular vesicles in the treatment of COVID-19 (coronavirus disease 2019) patients. Overall, this review will provide a better understanding of MSC-based therapies as a novel immunoregenerative strategy.

Translational Animal Models Provide Insight Into Mesenchymal Stromal Cell (MSC) Secretome Therapy

The therapeutic potential of the mesenchymal stromal cell (MSC) secretome, consisting of all molecules secreted by MSCs, is intensively studied. MSCs can be readily isolated, expanded, and manipulated in culture, and few people argue with the ethics of their collection. Despite promising pre-clinical studies, most MSC secretome-based therapies have not been implemented in human medicine, in part because the complexity of bioactive factors secreted by MSCs is not completely understood. In addition, the MSC secretome is variable, influenced by individual donor, tissue source of origin, culture conditions, and passage. An increased understanding of the factors that make up the secretome and the ability to manipulate MSCs to consistently secrete factors of biologic importance will improve MSC therapy. To aid in this goal, we can draw from the wealth of information available on secreted factors from MSC isolated from veterinary species. These translational animal models will inspire efforts to move human MSC secretome therapy from bench to bedside.

Aging of Bone Marrow Mesenchymal Stromal Cells: Hematopoiesis Disturbances and Potential Role in the Development of Hematologic Cancers

Simple Summary

As for many other cancers, the risk of developing hematologic malignancies increases considerably as people age. In recent years, a growing number of studies have highlighted the influence of the aging microenvironment on hematopoiesis and tumor progression. Mesenchymal stromal cells are a major player in intercellular communication inside the bone marrow microenvironment involved in hematopoiesis support. With aging, their functions may be altered, leading to hematopoiesis disturbances which can lead to hematologic cancers. A good understanding of the mechanisms involved in mesenchymal stem cell aging and the consequences on hematopoiesis and tumor progression is therefore necessary for a better comprehension of hematologic malignancies and for the development of therapeutic approaches.

Abstract

Aging of bone marrow is a complex process that is involved in the development of many diseases, including hematologic cancers. The results obtained in this field of research, year after year, underline the important role of cross-talk between hematopoietic stem cells and their close environment. In bone marrow, mesenchymal stromal cells (MSCs) are a major player in cell-to-cell communication, presenting a wide range of functionalities, sometimes opposite, depending on the environmental conditions. Although these cells are actively studied for their therapeutic properties, their role in tumor progression remains unclear. One of the reasons for this is that the aging of MSCs has a direct impact on their behavior and on hematopoiesis. In addition, tumor progression is accompanied by dynamic remodeling of the bone marrow niche that may interfere with MSC functions. The present review presents the main features of MSC senescence in bone marrow and their implications in hematologic cancer progression.

Novel insights for improving the therapeutic safety and efficiency of mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have attracted great interest in the field of regenerative medicine. They can home to damaged tissue, where they can exert pro-regenerative and anti-inflammatory properties. These therapeutic effects involve the secretion of growth factors, cytokines, and chemokines. Moreover, the functions of MSCs could be mediated by extracellular vesicles (EVs) that shuttle various signaling messengers. Although preclinical studies and clinical trials have demonstrated promising therapeutic results, the efficiency and the safety of MSCs need to be improved. After transplantation, MSCs face harsh environmental conditions, which likely dampen their therapeutic efficacy. A possible strategy aiming to improve the survival and therapeutic functions of MSCs needs to be developed. The preconditioning of MSCs ex vivo would strength their capacities by preparing them to survive and to better function in this hostile environment. In this review, we will discuss several preconditioning approaches that may improve the therapeutic capacity of MSCs. As stated above, EVs can recapitulate the beneficial effects of MSCs and may help avoid many risks associated with cell transplantation. As a result, this novel type of cell-free therapy may be safer and more efficient than the whole cell product. We will, therefore, also discuss current knowledge regarding the therapeutic properties of MSC-derived EVs.

Single-cell profiles of human bone marrow-derived mesenchymal stromal cells after IFN-γ and TNF-α licensing

BACKGROUND

Pre-licensing mesenchymal stromal cells (MSCs) with IFN-γ and TNF-α can empower their immune fate and induce a more effective immune regulation. However, the cellular heterogeneity of MSCs limits our understanding of this inflammatory licensing.

METHODS

The publicly available Gene Expression Omnibus single-cell RNA sequencing (scRNA-seq) data of human bone marrow-derived MSCs with or without IFN-γ and TNF-α licensing were analyzed. Based on the scRNA-seq data and related marker genes, the cell-cycle, stemness, differentiative potencies, and immunomodulate capability of unlicensed and licensed MSCs were compared.

RESULTS

After removing low-quality cells and regressing out the ribosomal gene effects, high-quality data reflecting IFN-γ and TNF-α effect on MSCs were chosen for further analysis. Despite the heterogeneity, pre-licensing didn't influence the cell-cycle and stemness of human bone marrow-derived MSCs. The osteogenesis potencies were decreased, the chondrogenesis potencies were increased while the adipogenesis potencies were stable in licensed MSCs. Licensed MSCs also showed more effective immunomodulate capability including expression of related chemokines, cytokines, surface molecules, and receptors.

CONCLUSION

Collectively, our study showed the expression profiles of human bone marrow-derived unlicensed and licensed MSCs about the cell cycle, stemness, differentiative potencies, and immunomodulate capability at single-cell resolution, which may help the comprehensive understanding about the inflammatory licensing of human bone marrow-derived MSCs and their further clinical application.

The biological response of mesenchymal stromal cells to thymol and carvacrol in comparison to their essential oil: An innovative new study

Mesenchymal stromal cells (MSCs) represent a progenitor cell population with several biological properties. MSCs are thus of therapeutic interest for cell-based therapy but great efforts are needed to enhance their efficiency and safety. Herbal remedies and in particular their bioactive molecules, are potential candidates for improving human health. The novelty and originality of this study is to develop an efficient cell-therapeutic product by combining MSCs with medicinal plant derived bioactive molecules. Thus, the impact of Essential Oil, Thymol and Carvacrol from Ptychotis verticillata on several BM-MSC biological features were studied. These compounds have shown positive effects on MSCs by preserving their morphology, sustaining their viability, promoting their proliferation, protecting them from cytotoxicity and oxidative stress. Accordingly, the combined administration of P. verticillata extract and MSCs may represent a new approach to enhance the therapeutic issue. Further investigations should greatly improve the manufacturing of these compounds as well as our understanding of the therapeutic effects of these bioactive molecules on the biology and functions of MSCs.