Functional and Immune Modulatory Characteristics of Bone Marrow Mesenchymal Stromal Cells in Patients With Aplastic Anemia: A Systematic Review

Background

In most patients with aplastic anemia (AA), the diagnosis is limited to a description of the symptoms. Lack of understanding of the underlying pathophysiological mechanisms causing bone marrow failure (BMF), hampers tailored treatment. In these patients, auto-immune cell-mediated destruction of the bone marrow is often presumed to be the causative mechanism. The status of the bone marrow microenvironment, particularly the mesenchymal stromal cell (MSC) component, was recently suggested as a potential player in the pathophysiology of AA. Therefore, functional, and immune modulatory characteristics of bone marrow MSCs might represent important parameters for AA.

Objective

To conduct a systematic review to evaluate in vitro functional properties of MSCs derived from patients with AA compared to healthy controls.

Methods

According to PRISMA guidelines, a comprehensive search strategy was performed by using online databases (Pubmed, ISI Web of Science, Embase, and the Cochrane Library). Studies reporting on phenotypical characterization, proliferation potential, differentiation capacity, immunomodulatory potential, and ability to support hematopoiesis were identified and screened using the Rayyan software tool.

Results

23 articles were included in this systematic review, describing a total of 324 patients with AA and 285 controls. None of the studies identified a significant difference in expression of any MSC surface marker between both groups. However, AA-MSCs showed a decreased proliferation potential, an increased tendency to differentiate into the adipogenic lineage and decreased propensity towards osteogenic differentiation. Importantly, AA-MSCs show reduced capacity of immunosuppression and hematopoietic support in comparison to healthy controls.

Conclusion

We conclude that there are indications for a contribution of MSCs in the pathophysiology of AA. However, the current evidence is of poor quality and requires better defined study populations in addition to a more robust methodology to study MSC biology at a cellular and molecular level. Future studies on bone marrow microenvironment should aim at elucidating the interaction between MSCs, hematopoietic stem cells (HSCs) and immune cells to identify impairments associated with/causing BMF in patients with AA.

Menstrual blood-derived stromal stem cells from women with and without endometriosis reveal different phenotypic and functional characteristics

Retrograde flow of menstrual blood cells during menstruation is considered as the dominant theory for the development of endometriosis. Moreover, current evidence suggests that endometrial-derived stem cells are key players in the pathogenesis of endometriosis. In particular, endometrial stromal stem cells have been suggested to be involved in the pathogenesis of this disease. Here, we aimed to use menstrual blood, as a novel source of endometrial stem cells, to investigate whether stromal stem cells from endometriosis (E-MenSCs) and non-endometriosis (NE-MenSCs) women differed regarding their morphology, CD marker expression pattern, proliferation, invasion and adhesion capacities and their ability to express certain immunomodulatory molecules. E-MenSCs were morphologically different from NE-MenSCs and showed higher expression of CD9, CD10 and CD29. Furthermore, E-MenSCs had higher proliferation and invasion potentials compared with NE-MenSCs. The amount of indoleamine 2,3-dioxygenase-1 (IDO1) and cyclooxygenase-2 (COX-2) in E-MenSCs co-cultured with allogenic peripheral blood mononuclear cells (PBMCs) was shown to be higher both at the gene and protein levels, and higher IDO1 activity was detected in the endometriosis group. However, NE-MenSCs revealed increased concentrations of forkhead transcription factor-3 (FOXP3) when compared with E-MenSCs. Nonetheless, interferon (IFN)-γ, Interleukin (IL)-10 and monocyte chemoattractant protein-1 (MCP-1) levels were higher in the supernatant of E-MenSCs-PBMC co-cultures. Here, we showed that there are inherent differences between E-MenSCs and NE-MenSCs. These findings propose the key role MenSCs could play in the pathogenesis of endometriosis and further support the retrograde and stem cell theories of endometriosis. Hence, considering its renewable and easily available nature, menstrual blood could be viewed as a reliable and inexpensive material for studies addressing the cellular and molecular aspects of endometriosis.

Aflatoxin B1 modulates the expression of phenotypic markers and cytokines by splenic lymphocytes of male F344 rats

Aflatoxin B1 (AFB1) is immunotoxic to animals and a suspected immunosuppressant in humans. In this study, we investigated the effects of AFB1 on splenic lymphocyte phenotypes and the inflammatory cytokine expression in male F344 rats. Exposure of animals to AFB1 [5-75 µg kg(-1) body weight (BW)] for 1 week showed dose-dependent decreases in the percentage of splenic CD8(+) T cells and CD3(-) CD8a(+) NK cells. A general inhibition of the expression of interleukin (IL)-4 and interferon (IFN)-γ by CD4(+) T cells, IL-4 and IFN-γ by CD8a(+) cells, and tumor necrosis factor (TNF)-α expression by natural killer (NK) cells was also found; however, no concurrent histological changes in spleen tissue were present, suggesting acute immunosuppression without overt toxicity. Five-week exposure with AFB1 significantly increased the percentages of CD3(+) and CD8(+) T cells, especially at low doses (≤ 25 µg kg(-1)). AFB1 treatment significantly decreased the anti-inflammatory cytokine IL-4 expression by CD4(+) T cells and significantly increased the pro-inflammatory cytokine IFN-γ expression by CD4(+) T cells and TNF-α expression by NK cells. These results indicated that repeated AFB1 exposure promotes inflammatory responses by regulating cytokine expression. Our data provides novel insights into the mechanisms by which AFB1 exposure differentially modulates the cell-mediated immune responses and suggests the involvement of an inflammatory response upon repeated exposure.