Structure and Function of the Bone Marrow and Hematopoiesis

Immune Tolerance vs. Immune Resistance: The Interaction Between Host and Pathogens in Infectious Diseases

The immune system is most likely developed to reduce the harmful impact of infections on the host homeostasis. This defense approach is based on the coordinated activity of innate and adaptive immune system components, which detect and target infections for containment, killing, or expulsion by the body's defense mechanisms. These immunological processes are responsible for decreasing the pathogen burden of an infected host to maintain homeostasis that is considered to be infection resistance. Immune-driven resistance to infection is connected with a second, and probably more important, defensive mechanism: it helps to minimize the amount of dysfunction imposed on host parenchymal tissues during infection without having a direct adverse effect on pathogens. Disease tolerance is a defensive approach that relies on tissue damage control systems to prevent infections from causing harm to the host. It also uncouples immune-driven resistance mechanisms from immunopathology and disease, allowing the body to fight infection more effectively. This review discussed the cellular and molecular processes that build disease tolerance to infection and the implications of innate immunity on those systems. In addition, we discuss how symbiotic relationships with microbes and their control by particular components of innate and adaptive immunity alter disease tolerance to infection.

Describing the evolution of myeloid-derived leucocytes in treated B-lineage paediatric acute lymphoblastic leukaemia with a data-driven granulocyte-monocyte-blast model

Acute lymphoblastic leukaemia (ALL) is associated with a compromised myeloid system. Understanding the state of granulopoiesis in a patient during treatment, places the clinician in an advantageous position. Mathematical models are aids able to present the clinician with insight into the behaviour of myeloid-derived leucocytes. The main objective of this investigation was to determine whether a proposed model of ALL during induction therapy would be a usable descriptor of the system. The model assumes the co-occurrence of the independent leukaemic and normal marrow populations. It is comprised of four delay-differential equations, capturing the fundamental characteristics of the blood and bone marrow myeloid leucocytes and B-lineage lymphoblasts. The effect of treatment was presumed to amplify cell loss within both populations. Clinical data was used to inform the construction, calibration and examination of the model. The model is promising-presenting a good foundation for the development of a clinical supportive tool. The predicted parameters and forecasts aligned with clinical expectations. The starting assumptions were also found to be sound. A comparative investigation highlighted the differing responses of similarly diagnosed patients during treatment and further testing on patient data emphasized patient specificity. Model examination recommended the explicit consideration of the suppressive effects of treatment on the normal population production. Additionally, patient-related factors that could have resulted in such different responses between patients need to be considered. The parameter estimates require refinement to incorporate the action of treatment. Furthermore, the myeloid populations require separate consideration. Despite the model providing explanation, incorporating these recommendations would enhance both model usability and predictive capacity.

Safety and Clinical Impact of a Single Red Light Irradiation on Breast Tumor-Bearing Mice

Low-level light therapy has been used in health care as a therapeutic strategy for different diseases. However, its effects on cancer are controversial. This work evaluated the effects of three energies on breast cancer-bearing mice after a single red light-emitting diode (LED) irradiation. 4T1 cells were inoculated into the mammary fat pad of female BALB/c mice. When tumor volume reached 100 mm³ , animals were irradiated by a LED irradiator (660 ± 11 nm) with energies of 1.2, 3.6, and 6.0 J. Control without irradiation and healthy animals were also evaluated. Mice were monitored regarding tumor volume and total blood count. After euthanasia, their organs were examined. We observed that a single irradiation does not increase tumor volume. All irradiated groups exhibited better clinical conditions than control, which presented a significant decrease in platelet and red blood cell levels compared with healthy mice. The energy of 3.6 J arrested neutrophil-lymphocyte rate besides promoting longer survival and a lower number of metastatic nodules in the lungs. These findings suggest that a single red LED irradiation causes no impact on the course of the disease. Besides, the intermediary dose-effect should be further investigated since it seems to promote better outcomes on breast cancer-bearing mice.

Continuous microfluidic encapsulation of single mesenchymal stem cells using alginate microgels as injectable fillers for bone regeneration

The encapsulation of cells in microscale hydrogels can provide a mimic of a three-dimensional (3D) microenvironment to support cell viability and functions and to protect cells from the environmental stress, which have been widely used in tissue regeneration and cell therapies. Here, a microfluidics-based approach is developed for continuous encapsulation of mesenchymal stem cells (MSCs) at the single-cell level using alginate microgels. This microfluidic technique integrated on-chip encapsulation, gelation, and de-emulsification into a one-step fabrication process, which enables scalable cell encapsulation while retaining the viability and functionality of loaded cells. Remarkably, we observed MSCs encapsulated in Ca-alginate microgels at the single-cell level showed significantly enhanced osteogenesis and accelerated mineralization of the microgels which occurred only after 7 days of induction. Furthermore, MSCs laden in alginate microgels displayed significantly enhanced bone formation compared to MSCs mixed with microgels and acellular microgels in a rat tibial ablation model. To conclude, the current microfluidic technique represents a significant step toward continuous single cell encapsulation, fabrication, and purification. These microgels can boost bone regeneration by providing a controlled osteogenic microenvironment for encapsulated MSCs and facilitate stem cell therapy in the treatment of bone defects in a minimally invasive delivery way. STATEMENT OF SIGNIFICANCE: The biological functions and therapeutic activities of single cells laden in microgels for tissue engineering remains less investigated. Here, we reported a microfluidic-based method for continuous encapsulation of single MSCs with high viability and functionality by integrating on-chip encapsulation, gelation, and de-emulsification into a one-step fabrication process. More importantly, MSCs encapsulated in alginate microgels at the single-cell level showed significantly enhanced osteogenesis, remarkably accelerated mineralization in vitro and bone formation capacity in vivo. Therefore, this single-cell encapsulation technique can facilitate stem cell therapy for bone regeneration and be potentially used in a variety of tissue engineering applications.

Isolation and Preparation of Bone Marrow-Derived Immune Cells for Metabolic Analysis

The isolation of immune cells from the bone marrow is important for obtaining sufficient numbers for downstream analysis. Immune cells derived from the bone marrow may be subjected to metabolic assays for analysis or used to test the effect of infectious agents on immune cells. Here, we describe a process for the isolation of macrophages, dendritic cells, and neutrophils from mice. Using the methods described herein, specific immune cells with purity above 85-90% can be obtained from the bone marrow of mice.

Cell-based liver therapies: past, present and future

Liver transplantation represents the standard treatment for people with an end-stage liver disease and some liver-based metabolic disorders; however, shortage of liver donor tissues limits its availability. Furthermore, whole liver replacement eliminates the possibility of using native liver as a possible target for future gene therapy in case of liver-based metabolic defects. Cell therapy has emerged as a potential alternative, as cells can provide the hepatic functions and engraft in the liver parenchyma. Various options have been proposed, including human or other species hepatocytes, hepatocyte-like cells derived from stem cells or more futuristic alternatives, such as combination therapies with different cell types, organoids and cell-biomaterial combinations. In this review, we aim to give an overview of the cell therapies developed so far, highlighting preclinical and/or clinical achievements as well as the limitations that need to be overcome to make them fully effective and safe for clinical applications.This article is part of the theme issue 'Designer human tissue: coming to a lab near you'.

Antineoplastic Agents and the Associated Myelosuppressive Effects

Bone marrow is a complex organ responsible for the regulation of hematopoietic cell distribution throughout the human body. Patients receiving antineoplastic agents as a therapeutic intervention for hematologic malignancy often experience varying degrees of myelotoxicity. Antineoplastic agents cause hypocellularity in marrow resulting in a reduction in hematopoietic tissue activity and a corresponding decline in cell production. Quantifying the adverse effects on hematopoiesis is based on the properties of a single agent, the use of individual drugs within a combination chemotherapy regimen, and the course, or courses, of chemotherapy designed to treat cancer. The direct or indirect suppression of erythrocytes, granulocytes, and megakaryocytes has potential for multiple negative clinical consequences ranging from increased monitoring of blood counts to life-threatening infection and death. This review will provide an overview of the structure and function of competent adult bone marrow, describe the process of hematopoiesis, and characterize the myelotoxicities associated with common antineoplastic agents currently used in the treatment of cancer.

Bone marrow aspirate and biopsy: a pathologist's perspective. II. interpretation of the bone marrow aspirate and biopsy

Bone marrow examination has become increasingly important for the diagnosis and treatment of hematologic and other illnesses. Morphologic evaluation of the bone marrow aspirate and biopsy has recently been supplemented by increasingly sophisticated ancillary assays, including immunocytochemistry, cytogenetic analysis, flow cytometry, and molecular assays. With our rapidly expanding knowledge of the clinical and biologic diversity of leukemia and other hematologic neoplasms, and an increasing variety of therapeutic options, the bone marrow examination has became more critical for therapeutic monitoring and planning optimal therapy. Sensitive molecular techniques, in vitro drug sensitivity testing, and a number of other special assays are available to provide valuable data to assist these endeavors. Fortunately, improvements in bone marrow aspirate and needle technology has made the procurement of adequate specimens more reliable and efficient, while the use of conscious sedation has improved patient comfort. The procurement of bone marrow specimens was reviewed in the first part of this series. This paper specifically addresses the diagnostic interpretation of bone marrow specimens and the use of ancillary techniques.

Bone marrow-based homeostatic proliferation of mature T cells in nonhuman primates: implications for AIDS pathogenesis

Bone marrow (BM) is the key hematopoietic organ in mammals and is involved in the homeostatic proliferation of memory CD8(+) T cells. Here we expanded on our previous observation that BM is a preferential site for T-cell proliferation in simian immunodeficiency virus (SIV)-infected sooty mangabeys (SMs) that do not progress to AIDS despite high viremia. We found high levels of mature T-cell proliferation, involving both naive and memory cells, in healthy SMs and rhesus macaques (RMs). In addition, we observed in both species that lineage-specific, BM-based T-cell proliferation follows antibody-mediated in vivo CD4(+) or CD8(+) T-cell depletion, thus indicating a role for the BM in maintaining T-cell homeostasis under depleting circumstances. We also observed that, in SIV-infected SMs, but not RMs, the level of proliferation of BM-based CD4(+) T cells is higher than that of circulating CD4(+) T cells. Interestingly, limited BM-based CD4(+) T-cell proliferation was found in SIV-infected SMs with low CD4(+) T-cell counts, suggesting a regenerative failure in these animals. Collectively, these results indicate that BM is involved in maintaining T-cell homeostasis in primates and suggest a role for BM-based CD4(+) T-cell proliferation in determining the benign nature of natural SIV infection of SMs.

How do normal and leukemic white blood cells egress from the bone marrow? Morphological facts and biochemical riddles

Under normal circumstances only mature granulocytes and monocytes cross the bone marrow sinus wall, a trilaminar structure consisting of endothelial cells, a discontinuous basal membrane and an adventitial cell layer in order to get access to the blood circulation. In leukemia, however, immature white blood cells are able to traverse the barrier and to appear in the blood stream. Very little is known about the regulatory processes which govern the egress of white blood cells in healthy individuals and their malignant counterparts in patients with leukemia. The results of the few studies performed to address this question in animal and human leukemias all agree that the extent to which adventitial cells (fibroblasts) cover the endothelium in bone marrow is drastically reduced. This implies altered interactions between the leukemic and adventitial cells and their extracellular matrix. We propose here a model to explain the egress of normal cells and their leukemic counterparts. It is based upon our own experimental data and the general at present limited knowledge of the subject. It is hoped that this model will stimulate further research into this important aspect of leukemogenesis.