The influence of protein malnutrition on biological and immunomodulatory aspects of bone marrow mesenchymal stem cells

Semaphorins and the bone marrow microenvironment: New candidates that influence the hematopoietic system

The bone marrow is a haven for hematopoietic and non-hematopoietic cells, creating complex micro-anatomical regions called niches. These distinct niches all participate in an intricate orchestra of cellular interactions that regulates the hematopoietic stem cell and its progenies. In this review, we provide a detailed description of the three most well-known bone marrow niches and their participation in hematopoiesis. We use pre-clinical data, including different in vitro and in vivo studies to discuss how a group of proteins called Semaphorins could potentially modulate both hematopoietic and non-hematopoietic cells, establishing links between the niches, semaphorins, and hematopoietic regulation. Thus, here we provide a deep dive into the inner functioning of the bone marrow and discuss the overarching implications that semaphorins might have on blood formation.

The influence of association between aging and reduced protein intake on some immunomodulatory aspects of bone marrow mesenchymal stem cells: an experimental study

PURPOSE

Dietary protein deficiency is common in the elderly, compromising hematopoiesis and the immune response, and may cause a greater susceptibility to infections. Mesenchymal stem cells (MSCs) have immunomodulatory properties and are essential to hematopoiesis. Therefore, this study aimed to investigate, in an aging model subjected to malnutrition due a reduced protein intake, aspects related to the immunomodulatory capacity of MSCs.

METHODS

Male C57BL/6 mice from young and elderly groups were fed with normoproteic or hypoproteic diets (12% and 2% of protein, respectively) and nutritional, biochemical and hematological parameters were evaluated. MSCs from bone marrow were isolated, characterized and their secretory parameters evaluated, along with gene expression. Additionally, the effects of aging and protein malnutrition on MSC immunomodulatory properties were assessed.

RESULTS

Malnourished mice lost weight and demonstrated anemia, leukopenia, and bone marrow hypoplasia. MSCs from elderly animals from both groups showed reduced CD73 expression and higher senescence rate; also, the malnourished state affected CD73 expression in young animals. The production of IL-1β and IL-6 by MSCs was affected by aging and malnutrition, but the IL-10 production not. Aging also increased the expression of NFκB, reducing the expression of STAT-3. However, MSCs from malnourished groups, regardless of age, showed decreased TGF-β and PGE₂ production. Evaluation of the immunomodulatory capacity of MSCs revealed that aging and malnutrition affected, mainly in lymphocytes, the production of IFN-γ and IL-10.

CONCLUSION

Aging and reduced protein intake are factors that, alone or together, influence the immunomodulatory properties of MSCs and provide basic knowledge that can be further investigated to explore whether MSCs' therapeutic potential may be affected.

The relationship between the degree of malnutrition and changes in selected parameters of the immune response in critically ill patients

Patients treated in intensive care units (ICUs) are at high risk of malnutrition and the resulting homeostasis, metabolic, histological and immunological disorders, especially leading to organ failure and increased susceptibility to infection. In 163 patients with malnutrition [mild in 33 (19.6%), moderate in 69 (42.9%), severe in 61 (37.4%)] treated in the ICU, changes in the concentration of selected proteins [interleukin (IL)-1Ra, tumor necrosis factor α (TNF-α), soluble tumour necrosis factor receptor-1 (sTNFR1), IL-6, IL-10, sTLR4, MyD88, A20, HSP70, HMGB1] were examined. In the whole group of malnourished patients, median values of sTNFR1, TNF-α, IL-6, TLR4, IL-1Ra were significantly increased, while the levels of MyD88 and A20 proteins were significantly reduced (in comparison to the well-nourished healthy group). Only the sTNFR1 protein showed a significant difference between mild, moderate and severe malnutrition, and increased concentrations as the severity of malnutrition increased (the correlation study found that as the degree of malnutrition increased, the sTNFR1 concentrations increased; p = 0.0000, R = 0.5442). It was observed that death was significantly more frequent in the group of patients who on the first day of hospitalization in the ICU scored 5 or more points on the NRS 2002 scale (p = 0.0004). In the patients who died significantly higher concentrations of sTNFR1, IL-6, IL-10, HSP70 were observed in comparison to the patients who survived. The present results are encouraging and indicate the desirability of undertaking multicentre clinical trials including monitoring of sTNFR1 in assessing the severity of malnutrition and immune disorders in the first hours after admission to the ICU, because it can be assumed that without early diagnosis of innate immunity disorders any attempts at their modulation may be ineffective.

Schistosoma mansoni Infection Is Impacted by Malnutrition

Schistosomiasis remains one of the most important neglected tropical diseases in the world. It mainly affects developing countries, where it often coexists with malnutrition. Despite this, few studies have investigated the relationship between schistosomiasis and malnutrition. Herein, we evaluate the impact of malnutrition on experimental S. mansoni infection. Mice were divided into 5 groups: Control (Ctrl) diet (14% protein and 10% lipids), low-protein 3% (LP 3%), low-protein 8% (LP 8%), low-fat 2.5% (LF 2.5%), and low-fat 5% (LF 5%). Mice were fed with their respective diets and were infected when a difference of approximately 20% in the body weight between mice from any experimental group and mice from the control group was achieved. Nutritional, parasitological, and immunological parameters were assessed either just before infection and/or approximately 50 days later before mice were perfused. Our results showed that the 3% low-protein diet was the only one capable of establishing malnutrition in mice. Mice fed with this diet showed: (i) significant reduction in body weight and serum albumin levels before infection, (ii) decreased levels of all biochemical parameters evaluated before perfusion, (iii) decreased numbers of schistosome eggs trapped in intestines and impaired parasite fecundity, (iv) a delay in the granuloma development with a smaller granuloma area, and (v) reduced levels of IL-4 and IFN-γ in the liver. Our findings demonstrate that low protein supply leads to malnutrition in mice and impacts the cytokine milieu in the liver and granuloma formation. Additionally, the establishment of our murine malnutrition model will enable future studies aiming to better understand the complex relationships between nutrition, immune responses, and infection outcome.

Effects of protein malnutrition on hematopoietic regulatory activity of bone marrow mesenchymal stem cells

Protein malnutrition causes anemia and leukopenia as it reduces hematopoietic precursors and impairs the production of mediators that regulate hematopoiesis. Hematopoiesis occurs in distinct bone marrow niches that modulate the processes of differentiation, proliferation and self-renewal of hematopoietic stem cells (HSCs). Mesenchymal stem cells (MSCs) contribute to the biochemical composition of bone marrow niches by the secretion of several growth factors and cytokines, and they play an important role in the regulation of HSCs and hematopoietic progenitors. In this study, we investigated the effect of protein malnutrition on the hematopoietic regulatory function of MSCs. C57BL/6NTaq mice were divided into control and protein malnutrition groups, which received, respectively, a normal protein diet (12% casein) and a low protein diet (2% casein). The results showed that protein malnutrition altered the synthesis of SCF, TFG-β, Angpt-1, CXCL-12, and G-CSF by MSCs. Additionally, MSCs from the protein malnutrition group were not able to maintain the lymphoid, granulocytic and megakaryocytic-erythroid differentiation capacity compared to the MSCs of the control group. In this way, the comprehension of the role of MSCs on the regulation of the hematopoietic cells, in protein malnutrition states, is for the first time showed. Therefore, we infer that hematopoietic alterations caused by protein malnutrition are due to multifactorial alterations and, at least in part, the MSCs' contribution to hematological impairment.

Malnutrition is associated with increased risk of hospital admission and death in the first 18 months of institutionalization

OBJECTIVES

This study aimed to investigate the association between different nutritional and anthropometric parameters with the risk of hospitalizations and death within 18 months from nursing home admission. Our hypothesis was that measures of malnutrition could be more strongly associated with worse clinical outcomes than measures of overweight/obesity.

METHODS

This prospective study involved 144 older adults newly admitted in nursing home and followed up over 18 months. A multidimensional assessment focusing on clinical, functional and cognitive status was performed at baseline. Assessment also included body mass index (BMI), waist circumference, calf circumference, MNA Short-Form (MNA-SF), and serum albumin and lymphocytes levels. Anthropometric measurements were repeated at 6 months. Data on hospitalizations and mortality over the study period, with their respective causes, were obtained from administrative data. The associations between baseline nutritional parameters and the risk of hospitalizations or death were analyzed through multinomial logistic regressions and Cox regressions, respectively.

RESULTS

During the follow-up, 64 individuals (44.4%) were hospitalized, and 52 (36.1%) died. Residents who reported low MNA-SF and calf circumference at nursing home admission had more than threefold-increased odds of hospitalizations compared with their healthier counterparts. Adults with low calf circumference also had the highest mortality (HR = 3.39, 95%CI:1.80-6.39), while more attenuated results were observed for low serum albumin, MNA-SF, and BMI (either when considering cut-offs of excess weight or malnutrition). When assessing the associations between 0 and 6 month changes in calf circumference and mortality in the following 12 months, we found that each 1 cm decrease in calf circumference increased the one-year mortality by 29% (95%CI 1.04-1.60).

CONCLUSIONS

Malnutrition, but not overweight/obesity, seems associated with a higher risk of hospitalization and mortality after nursing home admission. Monitoring calf circumference, in particular, may help in the early detection of individuals who are potentially vulnerable to adverse health-related outcomes after institutionalization.

Anorexia Nervosa and the Immune System-A Narrative Review

The pathogenesis of an increasing number of chronic diseases is being attributed to effects of the immune system. However, its role in the development and maintenance of anorexia nervosa is seemingly under-appreciated. Yet, in examining the available research on the immune system and genetic studies in anorexia nervosa, one becomes increasingly suspicious of the immune system’s potential role in the pathophysiology of anorexia nervosa. Specifically, research is suggestive of increased levels of various pro-inflammatory cytokines as well as the spontaneous production of tumor necrosis factor in anorexia nervosa; genetic studies further support a dysregulated immune system in this disorder. Potential contributors to this dysregulated immune system are discussed including increased oxidative stress, chronic physiological/psychological stress, changes in the intestinal microbiota, and an abnormal bone marrow microenvironment, all of which are present in anorexia nervosa.

Protein malnutrition impairs bone marrow endothelial cells affecting hematopoiesis

BACKGROUND & AIMS

Protein malnutrition (PM) affects hematopoiesis leading to bone marrow (BM) hypoplasia and arrests hematopoietic stem cells (HSC) in G₀/G₁ cell cycle phases, which cause anemia and leukopenia. Hematopoiesis is mainly regulated by BM niches where endothelial cells (EC) present a key regulatory role. Thus, our objective is to evaluate whether PM affects the modulatory capacity of EC on hematopoiesis.

METHODS

C57BL/6 male mice received for 5 weeks a normal protein diet (12% casein) or a low protein diet (2% casein). MSC were isolated and differentiated in vitro into EC and the synthesis of SCF, Ang-1, CXCL-12, IL-11, TGF-β and G-CSF were evaluated. The HSC and hematopoietic progenitors were quantified and the EC capacity to modulate the hematopoietic system was also evaluated. Moreover, the ability of PM bone marrow to support hematopoieisis was assessed by proliferation of infused leukemic myelo-monoblasts cells.

RESULTS

PM decreases HSC and hematopoietic progenitor pool and promotes cell cycle arrest and a lower proliferation rate of leukemic myelo-monoblasts. PM also committed hematopoietic regulatory characteristics from EC, resulting in the modification of both cell cycle pattern and hematopoietic differentiation.

CONCLUSION

BM microenvironment is compromised in PM, and since PM disturbs EC, it becomes one of the factors responsible for the hematopoietic cell cycle arrest and impairment of HSC differentiation.

L-Glutamine in vitro Modulates some Immunomodulatory Properties of Bone Marrow Mesenchymal Stem Cells

Glutamine (GLUT) is a nonessential amino acid that can become conditionally essential under stress conditions, being able to act in the modulation of the immune responses. Mesenchymal stem cells (MSCs) are known to their capability in the modulation of immune responses through cell-cell contact and by the secretion of soluble factors. Considering that GLUT is an immunonutrient and little is known about the influence of GLUT on the capability of MSCs to modulate immune cells, this work aims to investigate how variations in GLUT concentrations in vitro could affect some immunomodulatory properties of MSCs. In order to evaluate the effects of GLUT on MSCs immunomodulatory properties, cell proliferation rates, the expression of NFκB and STAT-3, and the production of IL-1β, IL-6, IL-10, TGF-β and TNF-α by MSCs were assessed. Based on our findings, GLUT at high doses (10 mM) augmented the proliferation of MSCs and modulated immune responses by decreasing levels of pro-inflammatory cytokines, such as IL-1β and IL-6, and by increasing levels of anti-inflammatory cytokines IL-10 and TGF-β. In addition, MSCs cultured in higher GLUT concentrations (10 mM) expressed lower levels of NF-κB and higher levels of STAT-3. Furthermore, conditioned media from MSCs cultured at higher GLUT concentrations (10 mM) reduced lymphocyte and macrophage proliferation, increased IL-10 production by both cells types, and decreased IFN-γ production by lymphocytes. Overall, this study showed that 10 mM of GLUT is able to modify immunomodulatory properties of MSCs.