Regulation of hematopoietic niches by sympathetic innervation

Interactions of B-lymphocytes and bone cells in health and disease

Bone remodeling occurs through the interactions of three major cell lineages, osteoblasts, which mediate bone formation, osteocytes, which derive from osteoblasts, sense mechanical force and direct bone turnover, and osteoclasts, which mediate bone resorption. However, multiple additional cell types within the bone marrow, including macrophages, T lymphocytes and B lymphocytes influence the process. The bone marrow microenvironment, which is supported, in part, by bone cells, forms a nurturing network for B lymphopoiesis. In turn, developing B lymphocytes influence bone cells. Bone health during homeostasis depends on the normal interactions of bone cells with other lineages in the bone marrow. In disease state these interactions become pathologic and can cause abnormal function of bone cells and inadequate repair of bone after a fracture. This review summarizes what is known about the development of B lymphocytes and the interactions of B lymphocytes with bone cells in both health and disease.

Sympathetic activity is correlated with satellite cell aging and myogenesis via β2-adrenoceptor

Background and objective

Sympathetic activity plays an important role in the proliferation and differentiation of stem cells, and it changes over time, thereby exerting differential effects on various stem cell types. Aging causes sympathetic hyperactivity in aged tissues and blunts sympathetic nerves regulation, and sympathetic abnormalities play a role in aging-related diseases. Currently, the effect of sympathetic activity on skeletal muscle stem cells, namely satellite cells (SCs), is unclear. This study aimed to investigate the effects of skeletal muscle sympathetic activity on SC aging and skeletal muscle repair.

Materials and methods

To evaluate skeletal muscle and fibrotic areas, numbers of SCs and myonuclei per muscle fiber, β2-adrenoceptor (β2-ADR) expression, muscle repair, and sympathetic innervation in skeletal muscle, aged mice, young mice that underwent chemical sympathectomy (CS) were utilized. Mice with a tibialis anterior muscle injury were treated by barium chloride (BaCl₂) and clenbuterol (CLB) in vivo. SCs or C2C12 cells were differentiated into myotubes and treated with or without CLB. Immunofluorescence, western blot, sirius red, and hematoxylin–eosin were used to evaluate SCs, myogenic repair and differentiation.

Results

The number of SCs, sympathetic activity, and reparability of muscle injury in aged mice were significantly decreased, compared with those in young mice. The above characteristics of young mice that underwent CS were similar to those of aged mice. While CLB promoted the repair of muscle injury in aged and CS mice and ameliorated the reduction in the SC number and sympathetic activity, the effects of CLB on the SCs and sympathetic nerves in young mice were not significant. CLB inhibited the myogenic differentiation of C2C12 cells in vitro. We further found that NF-κB and ERK1/2 signaling pathways were activated during myogenic differentiation, and this process could be inhibited by CLB.

Conclusion

Normal sympathetic activity promoted the stemness of SCs to thereby maintain a steady state. It also could maintain total and self-renewing number of SCs and maintain a quiescent state, which was correlated with skeletal SCs via β2-ADR. Normal sympathetic activity was also beneficial for the myogenic repair of injured skeletal muscle.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02571-8.

Endothelial progenitor cell dysfunction in acute exacerbation of chronic obstructive pulmonary disease

Endothelial progenitor cells (EPCs) are decreased in cardiac dysfunction morbidity associated with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Therefore, the present study aimed to assess the role of EPCs in AECOPD. Patients with AECOPD (n=27) or stable COPD (n=26) were enrolled. Systemic inflammatory markers (high-sensitivity C-reactive protein) were measured. In addition, EPCs were counted, isolated and cultured, and their proliferative, migratory, adhesive and tube-forming capabilities were determined, in cells from patients with AECOPD and stable COPD. EPC number was lower in patients with AECOPD (5.1±2.6×10³/ml) compared with patients with stable COPD (6.0±3.2×10³/ml). Migration assay indicated that the early-EPCs isolated from patients with AECOPD were significantly less mobile than EPCs derived from stable COPD subjects, at a stromal-cell derived factor-1α concentration of 100 ng/ml (3,550/30,000 vs. 7,853/30,000, P<0.05). C-X-C chemokine receptor-4 positivity was significantly reduced in AECOPD patients (16.1±9.9 vs. 56.33±6.3%, P<0.05). Furthermore, fewer early-EPC clusters were formed by EPCs derived from AECOPD, compared with those derived from stable COPD (8.2±0.86 vs. 14.4±1.36, P=0.027). Stable COPD late-EPCs were markedly deficient in intact tubule formation, however AECOPD late-EPCs formed no tubules. The number of AECOPD- and stable COPD-derived late-EPCs adhering to Matrigel-induced tubules was 36.8±1.85 and 20.6±1.36 (P<0.05) respectively, and the cluster of differentiation 31 positivity in late-EPCs was 79.69±1.3 and 29.1±2.47%, in AECOPD and stable COPD patients, respectively (P<0.001). The findings demonstrated that early-EPCs are decreased and dysfunctional in AECOPD patients, which may contribute to the altered vascular endothelium in this patient population.

Hormonal control of stem cell systems

Many organs respond to physiological challenges by changing tissue size or composition. Such changes may originate from tissue-specific stem cells and their supportive environment (niche). The endocrine system is a major effector and conveyor of physiological changes and as such could alter stem cell behavior in various ways. In this review, we examine how hormones affect stem cell biology in four different organs: the ovary, intestine, hematopoietic system, and mammary gland. Hormones control every stage of stem cell life, including establishment, expansion, maintenance, and differentiation. The effects can be cell autonomous or non-cell autonomous through the niche. Moreover, a single hormone can affect different stem cells in different ways or affect the same stem cell differently at various developmental times. The vast complexity and diversity of stem cell responses to hormonal cues allow hormones to coordinate the body's reaction to physiological challenges.

Hematological parameters are associated with metabolic syndrome in Japanese community-dwelling persons

Hematological parameters including red blood cell (RBC) count, hematocrit (Hct), and hemoglobin (Hgb) are independently associated with insulin resistance. The aim of this study was to determine whether hematological parameters are associated with metabolic syndrome (MetS), and its components, independent of gender, body mass index (BMI) and other confounders of cardiovascular disease. A total of 692 men [60 ± 14 (mean ± standard deviation); 20-89 (range) years] and 1,004 women (63 ± 12; 21-88 years) participants without diabetes were recruited from a single community at the time of their annual health examination. We examined the relationship between hematological parameters and insulin resistance assessed by Homeostasis model assessment of insulin resistance (HOMA-IR), MetS, and its components. RBC count, Hct, and Hgb were all significantly associated with measures of HOMA-IR. Multiple linear regression analyses for HOMA-IR showed that RBC count, Hct, and Hgb were all shown to be independently and significantly associated with HOMA-IR as well as gender, BMI, alcohol consumption, current smoking status, γ-glutamyltransferase, high molecular weight adiponectin, and uric acid. Inclusion of hematological parameters into the model further increased the coefficient of determination (R (2)). Compared to participants with the lowest quartile of Hct, multivariate-adjusted odds ratio for insulin resistance (HOMA-IR ≥ 1.74) was 2.27 [95 % confidence interval (CI), 1.55-3.31] for the third quartile, and 3.78 (95 % CI, 2.38-5.99) for the highest quartile. Hct was significantly and strongly associated with increased HOMA-IR levels. Hematological parameters were positively associated with insulin resistance and prevalence of MetS in Japanese dwelling-community persons.

The role of the β2 adrenergic receptor on endothelial progenitor cells dysfunction of proliferation and migration in chronic obstructive pulmonary disease patients

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in patients with moderate-to-severe chronic obstructive pulmonary disease (COPD), with > 44% of these patients presenting with generalized atherosclerosis at autopsy. It is accepted that endothelial progenitor cells (EPCs) participate in the repair of dysfunctional endothelium, thereby, protecting against atherosclerosis. The β2 adrenergic receptor (β2AR) expressed on mononuclear cells in peripheral blood and CD34(+) cells in bone has been shown to regulate T-cell traffic and proliferation. At present, there have been few systematic studies evaluating β2AR expression on EPCs in the peripheral blood of COPD patients and its role in EPCs migration and proliferation. Therefore, the objective of this study was to determine the role of β2ARs in EPCs function and, if this role is altered, in the COPD population.

METHODS

EPCs from 25 COPD and 16 control patients were isolated by Ficoll density-gradient centrifugation and identified using fluorescence-activated cell sorting. β2AR expression on EPCs was determined by western blotting and real-time PCR. The transwell migration assay was performed to determine the migration capacity of EPCs treated with a β2AR agonist, antagonist and β2AR monoclonal antibody. EPCs proliferation was assayed throughout the cell cycle. Following arterial damage in NOD/SCID mice, the number of EPCs treated with siRNA-β2AR incorporated at the injured vascular site was determined by fluorescence microscopy.

RESULTS

Data showed a significant increase in the total number of β2ARs in addition to an increased expression on early EPCs in COPD patients. COPD EPCs treated with β2AR antagonist (ICI 118551) increased migration to SDF-1α when compared to treatment with the β2AR agonist, norepinephrine. These changes were directly correlated to increase CXCR4 on EPCs. The proliferation of early EPCs treated with β2AR antagonist was improved and was correlated to an intercellular decrease in reactive oxygen species.

CONCLUSION

Changes in β2AR in COPD patients alter EPCs migration and proliferation, contributing to altered EPC repair capacity in this patient population.

Adult stem cell mobilization enhances intramembranous bone regeneration: a pilot study

BACKGROUND

Stem cell mobilization, which is defined as the forced egress of stem cells from the bone marrow to the peripheral blood (PB) using chemokine receptor agonists, is an emerging concept for enhancing tissue regeneration. However, the effect of stem cell mobilization by a single injection of the C-X-C chemokine receptor type 4 (CXCR4) antagonist AMD3100 on intramembranous bone regeneration is unclear.

QUESTIONS/PURPOSES

We therefore asked: Does AMD3100 mobilize adult stem cells in C57BL/6 mice? Are stem cells mobilized to the PB after marrow ablation? And does AMD3100 enhance bone regeneration?

METHODS

Female C57BL/6 mice underwent femoral marrow ablation surgery alone (n = 25), systemic injection of AMD3100 alone (n = 15), or surgery plus AMD3100 (n = 57). We used colony-forming unit assays, flow cytometry, and micro-CT to investigate mobilization of mesenchymal stem cells, endothelial progenitor cells, and hematopoietic stem cells to the PB and bone regeneration.

RESULTS

AMD3100 induced mobilization of stem cells to the PB, resulting in a 40-fold increase in mesenchymal stem cells. The marrow ablation injury mobilized all three cell types to the PB over time. Administration of AMD3100 led to a 60% increase in bone regeneration at Day 21.

CONCLUSIONS

A single injection of a CXCR4 antagonist lead to stem cell mobilization and enhanced bone volume in the mouse marrow ablation model of intramembranous bone regeneration.

Human endothelial progenitor cells isolated from COPD patients are dysfunctional

Cardiovascular disease is the leading cause of morbidity and mortality in patients with moderate-to-severe chronic obstructive pulmonary disease (COPD). More than 44% of these patients present with generalized atherosclerosis at autopsy. It is accepted that endothelial progenitor cells (EPCs) participate in the repair of dysfunctional endothelium and thus protects against atherosclerosis. However, whether COPD affects the repairing capacity of EPCs is unknown. Therefore, the objective of this study was to determine whether and how EPCs are involved in the vascular repair process in patients with COPD. In our study, EPCs from 25 COPD and 16 control patients were isolated by Ficoll density-gradient centrifugation and identified using fluorescence activated cell sorting. Transwell Migratory Assay was performed to determine the number of EPC colony-forming units and the adherent capacity late-EPCs to human umbilical vein endothelial cells. Following arterial damage in NOD/SCID mice, the number of EPCs incorporated at the injured vascular site was determined using a fluorescence microscope. We found that the number of EPC clusters and cell migration, as well as the expression of CXCR4, was significantly decreased in patients with COPD. Additionally, the number of late-EPCs adherent to HUVEC tubules was significantly reduced, and fewer VEGFR2(+)-staining cells were incorporated into the injured site in COPD patients. Our study demonstrates that EPC capacity of repair was affected in COPD patients, which may contribute to altered vascular endothelium in this patient population.

Deconstructing the hematopoietic stem cell niche: revealing the therapeutic potential

Development of the hematopoietic system is a stage-specific process where the bone marrow eventually becomes the principal source of hematopoiesis in the adult mammalian organism. Sustained hematopoiesis in the bone marrow, however, depends on the self-renewal of the resident hematopoietic stem cells (HSCs). The region where these HSCs are hypothesized to self renew is called the stem cell ‘niche.’ Recent studies have identified components of the HSC niche in the bone marrow, including cells of the osteoblastic lineage, extracellular matrix molecules and molecular signaling interactions between the stem cells and niche cells. Specific pharmacological targeting of these niche components has led to beneficial HSC effects, demonstrating a new therapeutic approach where stem cell function is altered through targeting of the niche.