Structure and function of bone marrow environment

Bone marrow and spleen are the major hematopoietic tissue in adult mice. However, little is known about the specific mechanism regulating hematopoiesis within these tissues. Since Dexter et al. first described conditions to maintain bone marrow hematopoiesis, long term bone marrow culture (LTBMC) has been developed in order to analyze the mechanism of the maintenance of proliferation and differentiation of hematopoietic stem cells in vitro. Furthermore, several stromal cell lines which are able to support the growth and differentiation of hematopoietic lineage, has been established from LTBMC. Although it is well known that bone marrow stromal cell lines are able to produce colony stimulating factors, it has been suggested that the stromal cell factors which involve membrane bound moieties must have a key role in the regulation of hematopoiesis. We expect that monoclonal antibodies to the surface of bone marrow stromal cells could detect such a critical stroma-associated protein that bounds the cell surface of the bone marrow stroma.     

Basic and 'special' stains for plastic sections in bone marrow histopathology, with special reference to May-Grünwald Giemsa and enzyme histochemistry

A battery of morphological, histochemical, and enzyme histochemical stains have been experimented on semithin sections of glycol-methacrylate-embedded bone marrow biopsies. We have been able to reproduce on sections the typical 'Romanowsky effect' which characterizes May-Grünwald Giemsa-stained smears of bone marrow or peripheral blood. This appears to be of critical importance for proper routine morphological evaluation of bone marrow biopsies. Conventional histochemical stains, and the enzyme histochemistry reactions that are most useful and widely used in the study of marrow aspiration smears have been successfully applied to plastic sections: in this way the evaluation of the cytochemical profiles of marrow diseases, especially leukemias, may be included in the histopathologist's diagnostic approach, with the additional advantage of preserving the architecture of the tissue and the relationship between haemapoietic cells and stromal components.     

Oxygen metabolism in rabbit bone marrow and liver.

Oxygen metabolism has been quantified in rabbit bone marrow and liver. NADPH-Cytochrome $\text{c}$ reductase activity in bone marrow microsomal and cytosol fractions was about 40% of that found in liver. Superoxide anion and peroxide generation were found to be present in both liver and bone marrow. Catalase and superoxide dismutase activity were measured in liver and in marrow preparations free of erythrocytes; while liver catalase activity was approximately twice that of bone marrow, very low superoxide dismutase activity was observed in erythrocyte free bone marrow homogenates.     

Bone marrow transplantation--an expanding approach to treatment of many diseases

Thus, we can conclude that marrow transplantation has already influenced medical practice greatly. It has offered a treatment which often cures patients of more than 20 otherwise lethal diseases. The treatment so horrendously difficult and dangerous at first has already been greatly improved, simplified, and made much safer. The availability of a suitable donor has been much extended and real progress has been made in prevention and perhaps even in treatment of graft-versus-host disease. This has made possible the option of marrow transplantation for every patient in whom we think the treatment may be beneficial. The problem underlying many cases of interstitial pneumonia has been identified and patients are already benefitting clinically from this progress. Progress has also been made which promises antiviral therapy which could reduce, prevent, and ultimately eliminate the intercurrent virus infections which limit the applicability of marrow transplantation, especially for children with severe immunodeficiencies. I do not know how far this line of investigation can be taken. However, just as we have learned stepwise to use marrow transplants from matched siblings to treat many diseases, to use fetal liver in place of bone marrow, to employ matched relative donors when a matched sibling is not available, and, finally, even to use parental donors to achieve correction of SCID, we now have good reason to believe that, ultimately, we can use marrow transplantation without fear of GVHD to address many additional genetically determined and acquired diseases; certainly, for those diseases that involve any of the cells that are derived from bone marrow cells, and perhaps for those attributable even to cells of other organs and tissues, the functions of which are, in whole or in part, a consequence of interactions of marrow-derived cells and cells of ectodermal or endodermal origin, marrow transplantation may be useful. To us, the future of marrow transplantation as a major modality of treatment or prevention of many diseases, including hemoglobinopathesis, immunodeficiencies, hematologic abnormalities, abnormalities of function of marrow-derived cells, and even inborn errors of function of cells of organs and tissues not of marrow origin, seems bright, indeed. Further, with the capacity to introduce resistance genes against viruses and malignancies, autoimmune diseases, and diseases dependent on anomalies of immune response genes, marrow transplantation for many other diseases seems a more remote possibility.(ABSTRACT TRUNCATED AT 400 WORDS)     

Morphological changes after large-field irradiation of dogs and autologous bone marrow transplantation

The effect of an automyelotransplant taken from a nonirradiated area of bone marrow has been studied after large fields irradiation in dogs. Certain changes occurring in the hemopoietic organs and in some other vitally important organs have been revealed. The automyelotransplantation contributes to a quicker repopulation of the bone marrow and stimulates lymphoid hemopoiesis in the spleen; that plays a positive role in overcoming the bone marrow syndrome at radiation illness. In other organs (gastrointestinal tract, kidneys, lungs, heart) given various doses of irradiation, in the control and test (with automyelotransplantation) groups similar morphological changes have been revealed.     

Erythropoietic bone marrow in the pigeon: development of its distribution and volume during growth and pneumatization of bones

During postnatal development of the pigeon, a large portion of the skeleton becomes pneumatized, displacing the hemopoietic bone marrow. The consequences of pneumatization on distribution and quantity of bone marrow as well as the availability of other sites for hemopoiesis have been investigated. Hemopoietic marrow of differently aged pigeons divided into five groups from 1 week posthatching (p.h.) up to 6 months p.h. was labeled with Fe-59 and examined by serial whole-body sections. Autoradiography and morphometry as well as scintillation counts of single bones and organs were also carried out. No sign of a reactivation of embryonic sites of erythropoiesis was found. Bone marrow weight and its proportion of whole-body weight increased during the first 4 weeks p.h. from 0.54% to 2.44% and decreased in the following months to about 1.0%. The developing bone marrow showed a progressive distribution during the first months of life, eventually being distributed proportionally over the entire skeleton, except for the skull. At the age of 6 months p.h. bone marrow had been displaced, its volume decreasing in correlation to increasing pneumaticity and conversion to fatty marrow. This generates the characteristic pattern of bone marrow distribution in adult pigeons, which shows hemopoietic bone marrow in ulna, radius, femur, tibiotarsus, scapula, furcula, and the caudal vertebrae.     

Transfer and expression of the human multiple drug resistance gene as potential human gene therapy

The human multiple drug resistance (MDR) gene has been used as a model for human gene transfer which could lead to human gene therapy. MDR is a transmembrane protein which pumps a number of toxic substances out of cells including several drugs used in cancer chemotherapy. Normal bone marrow cells express low levels of MDR and are particularly sensitive to the toxic effects of these drugs. There are two general applications of MDR gene therapy: (1) to provide drug-resistance to the marrow of cancer patients receiving chemotherapy, and (2) as a selectable marker which when co-transferred with a non-selectable gene such as the human beta globin gene can be used to enrich the marrow for cells containing both genes. We demonstrate efficient transfer and expression of the human MDR gene in a retroviral vector into live mice and human marrow cells including CD34⁺ cells isolated from marrow and containing the bulk of human hematopoietic progenitors. MDR gene transduction corrects the sensitivity of CD34⁺ cells to taxol, an MDR drug substrate, and enriches the marrow for MDR-transduced cells. The MDR gene-containing retroviral supernatant used has been shown to be safe and free of replication-competent retrovirus. Because of the safety of the MDR retroviral supernatant, and efficient gene transfer into mouse and human marrow cells, a phase 1 clinical protocol for MDR gene transfer into cancer patients has been approved to evaluate MDR gene transfer and expression in human marrow.     

Purification of a colony-stimulating factor from cultured pancreatic carcinoma cells.

Serum-free conditioned medium prepared from an established line of human pancreatic carcinoma (MIA PaCa-2) provides a rich source of colony-stimulating factor (CSF). Two activities distinctly separable by isoelectrofocusing have been identified: a high molecular weight CSF exhibiting greater activity in mouse bone marrow and a low molecular weight CSF more active in human bone marrow. The high molecular weight CSF has been purified 1000-fold to apparent homogeneity by a two-step procedure including isoelectrofocusing and gel filtration chromatography. The purified CSF has a molecular weight of 50,000 and an isoelectric point of 3.7 to 4.6. It is a glycoprotein as shown by periodic acid-Schiff stain and exhibits greater activity in mouse marrow than in human marrow.     

A study on location of synthetic site which mainly synthesizes and delivers fifth component of complement system in vivo

Tissue sites for synthesis of the fifth component of complement (C5) in vivo have been investigated by using allogeneic bone marrow chimeras and bone marrow chimeras which were transplanted in addition with hepatocytes. Our prior studies have demonstrated that bone marrow chimeras which had been prepared by transplanting marrow cells from C5-sufficient donor mice into irradiated C5-deficient recipients lacked detectable levels of C5 in the sera. However, when such potentially C5-deficient [C5(+)---C5(-)] chimeras were introduced into their spleens by means of injections of fully dispersed single cell suspensions of hepatocytes isolated from the C5-sufficient donor strain, they accepted the transplantation of hepatocytes for prolonged periods and developed a measurable amount of C5 in the sera. These results indicate that C5 protein in sera is not synthesized in significant amount by cells that are descendants of bone marrow cells but rather that this complement component is synthesized and delivered to the blood in vivo by somatic cells including liver cells that are not derivatives of the bone marrow.     

Macrophages and stromal cells phagocytose apoptotic bone marrow-derived B lineage cells

It has been hypothesized that B cell precursors that undergo programmed cell death due to nonproductive Ig gene rearrangements are cleared from the bone marrow by macrophages. However, a role for macrophages in this process is supported only by micrographs showing their association with apoptotic-appearing, B lineage cells. Functional data demonstrating phagocytosis of apoptotic, bone marrow lymphocytes by macrophages have not been presented, nor have receptors potentially involved in that process been identified. The data in this report demonstrate that macrophages isolated from murine bone marrow efficiently phagocytose apoptotic murine B lineage cells using multiple receptors that include CD14, integrins, class A scavenger receptor, and CD31 (PECAM-1). In addition, the results further reveal a new role for the hemopoietic microenvironment in B cell development in view of data demonstrating that murine bone marrow stromal cells are also capable of clearing apoptotic cells via an integrin-dependent mechanism.     

The non-equivalence of mouse and human marrow culture in the assay of granulopoietic stimulatory factors

Mouse bone marrow forms colonies of granulocytes and monocytic phagocytes when cultured in the presence of human plasma, urine or “feeder layers” prepared from human leukocytes. By contrast, human marrow produces colonies in the presence of leukocyte feeder layers but not in the presence of plasma or urine. It has been tacitly assumed that the response of mouse marrow to human blood leukocyte feeder layers is a measure of physiological substances released by those leukocytes which might control human granulopoiesis. This assumption however, has never been put to the test by comparing the response of mouse and human marrow to stimulation by leukocytes from the same individual. This has been done in the present study by using leukocytes from normal and leukemic subjects. Different human marrows responded similarly to stimulation by the same normal feeder layers, but there was no quantitative or qualitative correlation between the response of human and mouse marrows. Feeder layers from patients with acute granulocytic leukemia did not stimulate colony growth in normal human marrow but were as potent in stimulating mouse marrow colony growth as were feeder layers of normal leukocytes. We conclude that different factors may stimulate human and mouse marrows and that assays of granulopoietic factors of human origin should in future be carried out in human rather than mouse marrows.     

Bone marrow-derived hematopoietic cells generate cardiomyocytes at a low frequency through cell fusion, but not transdifferentiation

Recent studies have suggested that bone marrow cells might possess a much broader differentiation potential than previously appreciated. In most cases, the reported efficiency of such plasticity has been rather low and, at least in some instances, is a consequence of cell fusion. After myocardial infarction, however, bone marrow cells have been suggested to extensively regenerate cardiomyocytes through transdifferentiation. Although bone marrow-derived cells are already being used in clinical trials, the exact identity, longevity and fate of these cells in infarcted myocardium have yet to be investigated in detail. Here we use various approaches to induce acute myocardial injury and deliver transgenically marked bone marrow cells to the injured myocardium. We show that unfractionated bone marrow cells and a purified population of hematopoietic stem and progenitor cells efficiently engraft within the infarcted myocardium. Engraftment was transient, however, and hematopoietic in nature. In contrast, bone marrow-derived cardiomyocytes were observed outside the infarcted myocardium at a low frequency and were derived exclusively through cell fusion.     

Generation and characterization of IL-2-activated bone marrow cells as a potent graft vs tumor effector in transplantation

The potential of bone marrow transplantation as an immunotherapeutic modality, using biomodulation of the marrow cells has been ignored in autologous transplantation. Furthermore, many common cancers such as lung, colon, prostate, and pancreas are resistant to even transplant doses of conventional agents and hence require novel approaches such as biomodulation. This study shows that we can generate cytotoxic killer cells similar to lymphokine-activated killer cells capable of lysing NK-resistant tumor cells in vitro if we incubate human or murine bone marrow in IL-2. This was accomplished without affecting the ability of the bone marrow to fully reconstitute mice similar to that of fresh nonactivated bone marrow. Studies evaluating the IL-2 activated human bone marrow in vitro also indicated that these activated bone marrow have similar CFU to that of fresh human marrow. Furthermore, in murine in vivo studies, the activated bone marrow (ABM) caused significant tumor regression in tumor-bearing mice. Also, these ABM cells had similar or higher tumoricidal activity and longer kinetics than spleen lymphokine-activated killer cells in vitro. Also, the ABM had purging ability in vitro. Therefore this IL-2 ABM could be used as an active therapeutic tool and not just as a passive rescue element in the autologous bone marrow transplantation setting.     

Allogeneic bone marrow transplantation with co-stimulatory blockade induces macrochimerism and tolerance without cytoreductive host treatment

Allogeneic bone marrow transplantation (in immunocompetent adults) has always required cytoreductive treatment of recipients with irradiation or cytotoxic drugs to achieve lasting engraftment at levels detectable by non-PCR-based techniques ('macrochimerism' or 'mixed chimerism'). Only syngeneic marrow engraftment at such levels has been achieved in unconditioned hosts. This requirement for potentially toxic myelosuppressive host pre-conditioning has precluded the clinical use of allogeneic bone marrow transplantation for many indications other than malignancies, including tolerance induction. We demonstrate here that treatment of naive mice with a high dose of fully major histocompatibility complex-mismatched allogeneic bone marrow, followed by one injection each of monoclonal antibody against CD154 and cytotoxic T-lymphocyte antigen 4 immunoglobulin, resulted in multi-lineage hematopoietic macrochimerism (of about 15%) that persisted for up to 34 weeks. Long-term chimeras developed donor-specific tolerance (donor skin graft survival of more than 145 days) and demonstrated ongoing intrathymic deletion of donor-reactive T cells. A protocol of high-dose bone marrow transplantation and co-stimulatory blockade can thus achieve allogeneic bone marrow engraftment without cytoreduction or T-cell depletion of the host, and eliminates a principal barrier to the more widespread use of allogeneic bone marrow transplantation. Although efforts have been made to minimize host pre-treatment for allogeneic bone marrow transplantation for tolerance induction, so far none have succeeded in eliminating pre-treatment completely. Our demonstration that this can be achieved provides the rationale for a safe approach for inducing robust transplantation tolerance in large animals and humans.     

Impact of parathyroid hormone on bone marrow-derived stem cell mobilization and migration

Parathyroid hormone (PTH) is well-known as the principal regulator of calcium homeostasis in the human body and controls bone metabolism via actions on the survival and activation of osteoblasts. The intermittent administration of PTH has been shown to stimulate bone production in mice and men and therefore PTH administration has been recently approved for the treatment of osteoporosis. Besides to its physiological role in bone remodelling PTH has been demonstrated to influence and expand the bone marrow stem cell niche where hematopoietic stem cells, capable of both self-renewal and differentiation, reside. Moreover, intermittent PTH treatment is capable to induce mobilization of progenitor cells from the bone marrow into the bloodstream. This novel function of PTH on modulating the activity of the stem cell niche in the bone marrow as well as on mobilization and regeneration of bone marrow-derived stem cells offers new therapeutic options in bone marrow and stem cell transplantation as well as in the field of ischemic disorders.     

Participation of bone marrow derived cells in cutaneous wound healing

Bone marrow has long been known to be a source of stem cells capable of regeneration of the hematopoeitic system. Recent reports, however, have indicated that bone marrow might also contain early stem cells that can differentiate into other organ tissues such as skin. While these studies have illustrated that bone marrow stem cells could find their way to the skin, they have not addressed the dynamics of how bone marrow stem cells might participate in the homeostatis and regeneration of skin. In this report we followed green fluorescent protein (GFP) labeled bone marrow transplanted into non-GFP mice in order to determine the participation of bone marrow stem cells in cutaneous wounds. Our results indicate that there are a significant number of bone marrow cells that traffic through both wounded and non-wounded skin. Wounding stimulated the engraftment of bone marrow cells to the skin and induced bone marrow derived cells to incorporate into and differentiate into non-hematopoietic skin structures. This report thus illustrates that bone marrow might be a valuable source of stem cells for the skin and possibly other organs. Wounding could be a stimulus for bone marrow derived stem cells to travel to organs and aid in the regeneration of damaged tissue.     

Heterogeneity of globin protein synthesis in bone marrow cells of patients with homozygous beta-thalassemia from Tadzhikistan

The synthesis of globin proteins in blood reticulocytes of homozygous beta-thalassemic patients from Tadzhikistan has been previously studied. beta-thalassemia with sharp repression of beta-globin protein synthesis (alpha/beta greater than 10) has been shown to be most representative for the region. In this work, the synthesis of globin proteins has been studied in bone marrow cells of homozygous beta-thalassemic patients. Comparison of data on globin synthesis in bone marrow cells and in blood reticulocytes of the patients has revealed that in some cases the disbalance of chain synthesis in both cell types is equal. In other cases the disbalance in bone marrow cells is less than in blood cells, indicating the instability of beta-globin mRNA that is partially degrading in the process of cell maturation. Homozygous beta-thalassemic cases with low content of Hb F in blood cells (5-10%), with substantial disbalance of alpha and beta-globin synthesis and marked production of gamma-globins in bone marrow cells and in blood reticulocytes are of special interest. It has been assumed that parallel to beta-thalassemia some instability of gamma-globin proteins takes place in these patients.     

Differentiation of human stromal bone marrow cell precursors in monolayer culture

The colonies of human bone marrow fibroblasts in monolayer culture have been studied. It has been shown that there are two types of colonies in the cultures: monolayer and multilayer ones, both having alkaline phosphatase-positive cells. In monolayer colonies one can observe calcium deposition indicative of osteogenic differentiation of human bone marrow stromal cells.     

THE ROLE OF THE SPLEEN IN THE REPOPULATION OF THE HAEMOPOIETIC SYSTEM OF HEAVILY-IRRADIATED MICE

The respective role of the spleen or of the bone marrow in the regeneration of the haemopoietic progenitor compartment of heavily-irradiated mice has been investigated. Splenectomy was used to this end in animals injected with exogenous isogenic cells or regenerating from endogenous spleen or marrow cells. Analysis of the data as a function of time shows that the presence of the spleen affects marrow CFU repopulation only at the early post-irradiation stages. The expansion of the marrow progenitor pool proceeds, however, rather independently of the spleen and marrow CFU remain eventually as the main source of haemopoietic cells in the surviving mice. Thus the reaction of the spleen may be envisaged as a fast, important but transient contribution to the overall haemopoietic function of heavily-irradiated animals.     

NZB mice exhibit a primary T cell defect in fetal thymic organ culture

Defects in T cell development have been suggested to be a factor in the development of systemic autoimmunity in NZB mice. However, the suggestion of a primary T cell defect has often been by extrapolation, and few direct observations of T cell precursors in NZB mice have been performed. Moreover, the capacity of NZB bone marrow T cell precursors to colonize the thymus and the ability of the NZB thymic microenvironment to support T lymphopoiesis have not been analyzed. To address this important issue, we employed the fetal thymic organ culture system to examine NZB T cell development. Our data demonstrated that NZB bone marrow cells were less efficient at colonizing fetal thymic lobes than those of control BALB/c or C57BL/6 mice. In addition, NZB bone marrow cells did not differentiate into mature T cells as efficiently as bone marrow cells from BALB/c or C57BL/6 mice. Further analysis revealed that this defect resulted from an intrinsic deficiency in the NZB Lin-Sca-1+c-kit+ bone marrow stem cell pool to differentiate into T cells in fetal thymic organ culture. Taken together, the data document heretofore unappreciated deficiencies in T cell development that may contribute to the development of the autoimmune phenotype in NZB mice.