Effective macrophage delivery using RAFT copolymer derived nanoparticles

We use reversible addition fragmentation chain transfer (RAFT) polymerisation to prepare block copolymers that are subsequently assembled into nanoparticles. The prepared nanoparticles were extensively taken up by primary murine macrophages and are effective in the delivery of a cell impenetrable cargo.

Effects of six APOA5 variants, identified in patients with severe hypertriglyceridemia, on in vitro lipoprotein lipase activity and receptor binding

OBJECTIVE

The purpose of this study was to identify rare APOA5 variants in 130 severe hypertriglyceridemic patients by sequencing, and to test their functionality, since no patient recall was possible.

METHODS AND RESULTS

We studied the impact in vitro on LPL activity and receptor binding of 3 novel heterozygous variants, apoAV-E255G, -G271C, and -H321L, together with the previously reported -G185C, -Q139X, -Q148X, and a novel construct -Delta139 to 147. Using VLDL as a TG-source, compared to wild type, apoAV-G255, -L321 and -C185 showed reduced LPL activation (-25% [P=0.005], -36% [P<0.0001], and -23% [P=0.02]), respectively). ApoAV-C271, -X139, -X148, and Delta139 to 147 had little affect on LPL activity, but apoAV-X139, -X148, and -C271 showed no binding to LDL-family receptors, LR8 or LRP1. Although the G271C proband carried no LPL and APOC2 mutations, the H321L carrier was heterozygous for LPL P207L. The E255G carrier was homozygous for LPL W86G, yet only experienced severe hypertriglyceridemia when pregnant.

CONCLUSIONS

The in vitro determined function of these apoAV variants only partly explains the high TG levels seen in carriers. Their occurrence in the homozygous state, coinheritance of LPL variants or common APOA5 TG-raising variant in trans, appears to be essential for their phenotypic expression.

Recent Australian experience with hemopoietic stem and progenitor cell expansion

This review provides insight into two clinical trials conducted with ex vivo manipulated CD34+ cells. The first was an attempt to deliver a gene therapy for treatment of HIV and the second an attempt to improve rates of hemopoietic recovery with ex vivo generated myeloid cells.

Periwound dopaminergic sprouting is dependent on numbers of wound macrophages

Injury to many regions of the central nervous system, including the striatum, results in a periwound or 'abortive' sprouting response. In order to directly evaluate whether macrophages play an important role in stimulating periwound sprouting, osteopetrotic (op/op) mice, which when young are deficient in a variety of macrophage subtypes, were given striatal wounds and the degree of dopaminergic sprouting subsequently assessed. Two weeks postinjury, significantly fewer wound macrophages were present in the striata of op/op mice compared with controls (144 +/- 30.1 in op/op mice vs. 416.6 +/- 82.3 in controls, P < 0.005, analysis performed on a section transecting the middle of the wound). Dopamine transporter immunohistochemistry revealed a marked decrease in the intensity of periwound sprouting in the op/op group of animals. Quantification of this effect using [H3]-mazindol autoradiography confirmed that periwound sprouting was reduced significantly in the op/op mice compared with controls (71.4 +/- 21.7 fmol/mg protein in op/op mice vs. 210.7 +/- 27.1 fmol/mg protein in controls, P < 0.0005). In the two groups of animals the magnitude of the sprouting response in individuals was closely correlated with the number of wound macrophages (R = 0.83, R2 = 0.69). Our findings provide strong support for the crucial involvement of macrophages in inducing dopaminergic sprouting after striatal injury.

Vascular cell adhesion molecule-1 (CD106) is cleaved by neutrophil proteases in the bone marrow following hematopoietic progenitor cell mobilization by granulocyte colony-stimulating factor

Mobilized progenitor cells currently represent the most commonly used source of hematopoietic progenitor cells (HPCs) to effect hematopoietic reconstitution following myeloablative chemotherapies. Despite their widespread use, the molecular mechanisms responsible for the enforced egress of HPCs from the bone marrow (BM) into the circulation in response to mobilizing agents such as cytokines remain to be determined. Results of this study indicate that expression of vascular cell adhesion molecule-1 (VCAM-1) is strongly reduced in vivo in the BM during HPC mobilization by granulocyte colony-stimulating factor (G-CSF) and stem cell factor. Two serine proteases, namely, neutrophil elastase and cathepsin G, were identified, which cleave VCAM-1 and are released by neutrophils accumulating in the BM during the course of immobilization induced by G-CSF. The proposal is made that an essential step contributing to the mobilization of HPCs is the proteolytic cleavage of VCAM-1 expressed by BM stromal cells, an event triggered by the degranulation of neutrophils accumulating in the BM in response to the administration of G-CSF.

Spatial localization of transplanted hemopoietic stem cells: inferences for the localization of stem cell niches

The spatial distribution of subpopulations of hemopoietic progenitor cells following syngeneic transplantation was investigated at the single-cell level. The location of infused hemopoietic progenitor cells within the femoral bone marrow of nonablated recipients was determined by 5-(and-6)-carboxyfluorescein diacetate succinimidyl ester labeling of cells and in situ fixation by perfusion. Analysis performed over 15 hours after infusion demonstrated that the spatial distribution of transplanted marrow cells is not a random process. Although the majority of cells enter the bone marrow from the central marrow vessels, the subsequent localization within the bone marrow varied according to their phenotype. Candidate "stem cells" demonstrated selective redistribution and were significantly enriched within the endosteal region, whereas mature terminally differentiated and lineage-committed cells selectively redistributed away from the endosteal region and were predominantly in the central marrow region. Together, these data strongly support historical evidence of the presence of endosteal hemopoietic stem cell niches.

Osteoblast-specific gene expression after transplantation of marrow cells: implications for skeletal gene therapy

Somatic gene therapies require targeted transfer of the therapeutic gene(s) into stem cells that proliferate and then differentiate and express the gene in a tissue-restricted manner. We have developed an approach for gene therapy using marrow cells that takes advantage of the osteoblast specificity of the osteocalcin promoter to confine expression of chimeric genes to bone. Adherent marrow cells, carrying a reporter gene [chloramphenicol acetyltransferase (CAT)] under the control of a 1.7-kilobase rat osteocalcin gene promoter, were expanded ex vivo. After transplantation by intravenous infusion, engrafted donor cells in recipient mice were detected by the presence of the transgene in a broad spectrum of tissues. However, expression of the transgene was restricted to osteoblasts and osteocytes, as established by biochemical analysis of CAT activity and immunohistochemical analysis of CAT expression at the single cell level. Our data indicate that donor cells achieved long-term engraftment in various tissues of the recipients and that the CAT gene under control of the osteocalcin promoter is expressed specifically in bone. Thus, transplantation of multipotential marrow cells containing the osteocalcin promoter-controlled transgene provides an efficacious approach to deliver therapeutic gene expression to osteoblasts for treatment of bone disorders or tumor metastasis to the skeleton.

Adhesion receptor expression by hematopoietic cell lines and murine progenitors: modulation by cytokines and cell cycle status

Hematopoietic progenitor cells are incubated with cytokine combinations for in vitro expansion of stem cells and to enhance retrovirus-mediated gene transfer. Optimization of the engraftment of these treated cells would be critical to the success of stem cell transplantation or gene therapy. Previous studies demonstrated that a 48-hour incubation of donor BALB/c bone marrow with a mixture of four cytokines (IL-3, IL-6, IL-11, and SCF), resulted in expansion of primitive progenitor/stem cells but a loss of long-term engraftment in nonmyeloablated or myeloablated recipients. We have established the expression pattern for a number of adhesion receptors by normal hematopoietic progenitors and cell lines and the modulation in expression induced by cytokines or cell cycle progression to ascertain the molecular basis for such defective engraftment. Northern blot analysis demonstrated that the cytokine combination of IL-3, IL-6, IL-11, and SCF dramatically down-regulated alpha 4 integrin receptor expression in HL-60 cells. Synchronized FDC-P1 cells exhibited modulation of alpha 4 expression through cell cycle progression, both by quantitative RT-PCR and flow cytometry. Normal murine bone marrow lineage-depleted, Sca+ cells expressed a number of adhesion receptors, including alpha L, alpha 1, alpha 3, alpha 4, alpha 5, alpha 6, beta 1, L-selectin, CD44, and PECAM as assessed by flow cytometry, immunofluorescence, and RT-PCR. There was modulation of the expression of several of these receptors after incubation in the four cytokines for 24 and/or 48 hours: the proportion of cells expressing alpha L, alpha 5, alpha 6, and PECAM increased, whereas the proportion of cells expressing alpha 4 and beta 1 decreased, after cytokine incubation. There was a demonstrable concomitant decline in adhesion of these cells to fibronectin after the cytokine incubation, a finding that correlates with the decrease in expression of alpha 4. These changes in adhesion receptor expression and function with cytokines and during cell cycle transit may be critical to stem cell homing and engraftment after transplantation, as multiple receptors could be involved in the process of rolling, attachment to endothelium, endothelial transmigration, and migration within the marrow space.

Cells capable of bone production engraft from whole bone marrow transplants in nonablated mice

Allogeneic and autologous marrow transplants are routinely used to correct a wide variety of diseases. In addition, autologous marrow transplants potentially provide opportune means of delivering genes in transfected, engrafting stem cells. However, relatively little is known about the mechanisms of engraftment in transplant recipients, especially in the nonablated setting and with regard to cells not of hemopoietic origin. In particular, this includes stromal cells and progenitors of the osteoblastic lineage. We have demonstrated for the first time that a whole bone marrow transplant contains cells that engraft and become competent osteoblasts capable of producing bone matrix. This was done at the individual cell level in situ, with significant numbers of donor cells being detected by fluorescence in situ hybridization in whole femoral sections. Engrafted cells were functionally active as osteoblasts producing bone before being encapsulated within the bone lacunae and terminally differentiating into osteocytes. Transplanted cells were also detected as flattened bone lining cells on the periosteal bone surface.

Lymphohematopoietic engraftment in minimally myeloablated hosts

The concept that myeloablation to open space was a prerequisite for marrow stem cell engraftment has been challenged by studies showing high rates of engraftment in nonmyeloablated mice (Stewart et al, Blood 81:2566, 1993; Quesenberry et al, Blood Cells 20:97, 1994; Brecher et al, Blood Cells 5:237, 1979; Saxe et al, Exp Hematol 12:277, 1984; and Wu et al, Exp Hematol 21:251, 1993). However, relatively large numbers of marrow cells were necessary to achieve high long-term donor percentages. We have demonstrated, using a BALB/c male/female marrow transplant model and detecting male DNA in host tissues by Southern blot or fluorescent in situ hybridization, that exposure to doses of irradiation that cause minimal myeloablation (50 to 100 cGy) leads to very high levels of donor chimerism, such that relatively small numbers of marrow cells (10 to 40 million) can give donor chimerism in the 40% to 100% range. Studies of radiation sensitivity of long-term engrafting cells have shown that 100 cGy, although not myelotoxic, is stem cell toxic, and indicate that the final host:donor ratios are determined by competition between host and donor stem cells. These data indicate that low levels of irradiation should be an effective approach to nontoxic marrow transplantation in gene therapy or in attempts to create allochimerism to treat such diseases as cancer, sickle cell anemia, or thalassemia.

Immunofluorescence characterization of key extracellular matrix proteins in murine bone marrow in situ

The mechanism of hemopoietic stem cell homing to the bone marrow involves molecular interactions that mediate the recognition and interaction of these cells with the marrow microenvironment, including the extracellular matrix. On selective binding, this environment, in combination with soluble cytokines, regulates stem cell proliferation and differentiation. Using immunofluorescence labeling, we analyzed the location of the prominent extracellular matrix proteins fibronectin, collagen Types I, III, and IV, and laminin in sections of murine femoral bone marrow. Collagen Types I, IV, and fibronectin were localized to the endosteum, the region of the femoral microenvironment for which homing stem cells have a high affinity. The results further demonstrated a strong spatial association of collagen Type IV and laminin with the bone marrow vessels, including arterioles, veins, and sinuses. Fibronectin was distributed throughout the central marrow region, and all the proteins analyzed except collagen Type III were present in the bone, although at different levels. Fibronectin, collagen Types III and IV, and laminin were also present in the periosteum. The distinct locations of particular extracellular matrix proteins support the notion that they may play an important mechanistic role in the homing of engrafting cells.

Synchronized cell-cycle induction of engrafting long-term repopulating stem cells

We have recently defined the window for marrow stem cell homing into nonablated hosts as the first 24 hours posttransplant. Within this homing window, donor cells rapidly cleared from the peripheral blood and lungs and plateaued in the marrow. We have now assessed the cell-cycle status of the engrafting cells capable of contributing to long-term hematopoiesis using administration of hydroxyurea (HU), a chemotherapy agent with S-phase cell-cycle specificity. HU was given at very short periods following a male bone marrow transplant (0, 3, 6, 12, and 15 hours) into female nonablated hosts, and donor cell engraftment was analyzed after 6 weeks. The data show that quickly after transplant (12 hours), greater than half of the engrafting cells capable of contributing long-term to all levels of the hematopoietic hierarchy are in S-phase. Analysis after 6 weeks included whole bone marrow, peripheral blood, primitive cells with high proliferative potential, and mature lineage-restricted marrow cells. These donor cells appear to be naturally synchronized. When HU was administered at any of the other time points, there was little evidence of cell death 6 weeks postengraftment.

Potential and distribution of transplanted hematopoietic stem cells in a nonablated mouse model

Increasingly, allogeneic and even more often autologous bone marrow transplants are being done to correct a wide variety of diseases. In addition, autologous marrow transplants potentially provide an opportune means of delivering genes in transfected, engrafting stem cells. However, despite its widespread clinical use and promising gene therapy applications, relatively little is known about the mechanisms of engraftment in marrow transplant recipients. This is especially so in the nonablated recipient setting. Our data show that purified lineage negative rhodamine 123/Hoechst 33342 dull transplanted hematopoietic stem cells engraft into the marrow of nonablated syngeneic recipients. These cells have multilineage potential, and maintain a distinct subpopulation with "stem cell" characteristics. The data also suggests a spatial localization of stem cell "niches" to the endosteal surface, with all donor cells having a high spatial affinity to this area. However, the level of stem cell engraftment observed following a transplant of "stem cells" was significantly lower than that expected following a transplant of the same number of unseparated marrow cells from which the purified cells were derived, suggesting the existence of a "nonstem cell facilitator population," which is required in a nonablated syngeneic transplant setting.

In situ detection of individual transplanted bone marrow cells using FISH on sections of paraffin-embedded whole murine femurs

Studies of transplantation biology rely on the detection of donor hemopoietic cells in transplant recipients. Traditionally this has been achieved through ex vivo techniques, including flow cytometric analysis of cell surface markers to detect cells expressing specific epitopes, histochemical detection of cytoplasmic proteins, and the detection of Y chromosome-specific sequences by DNA hybridization. Studies using congenic models, such as the Ly5.1/5.2 mouse, or the utilization of fluorescent dyes, such as PKH-26, have allowed more in-depth analysis of transplantation, beginning to address key issues such as cell homing through cell tracking and elucidation of the "stem cell niche." However, these methods are limited by labeling sensitivity, specificity, crossreactivity and, in the case of PKH-26 labeling, the number of cell divisions the transplanted cells can make before the signal disappears. We have developed a fluorescent in situ hybridization (FISH) technique that utilizes a murine Y chromosome-specific "painting" probe to identify in situ individual transplanted male cells in paraffin-embedded sections of female whole bone marrow while maintaining good morphological integrity. This method is highly sensitive and specific, labeling more than 99% of male cells and no female cells, allowing each transplant to be assessed at the individual cell level. The technique provides unique opportunities to follow the path taken by transplanted cells, both during homing into the marrow and through their maturation and differentiation into mature, functional hemopoietic cells.

Granulocyte-macrophage colony-stimulating factor is not responsible for the correction of hematopoietic deficiencies in the maturing op/op mouse

Osteopetrotic (op/op) mice are characterized by an autosomal recessive inactivating mutation resulting in the absence of biologically active colony-stimulating factor-1 (CSF-1). Consequently, young op/op mice have a severe deficiency of macrophages and osteoclasts resulting in excessive bone formation, occlusion of the marrow cavity, and reduced marrow hematopoietic activity. Recently, we showed that the osteopetrosis and hematopoietic deficiencies evident in young op/op mice are not permanent but are progressively corrected with age. There are increases in osteoclast activity; bone resorption; femoral marrow space; and marrow hematopoietic activity, cellularity, and macrophage content. In the present study we show that CSF-1-/- granulocyte-macrophage colony-stimulating factor (GM-CSF)(-/-)-deficient mice also undergo the same pattern of hematopoietic correction as the op/op mouse. Also, like the op/op mouse, the peritoneal cellularity and macrophage content of CSF-1/GM-CSF-deficient mice remains severely reduced. Our data show that the "knockout" of GM-CSF does not change the op/op phenotype, and that GM-CSF is not essential for the correction of the hematopoietic deficiencies in the op/op mouse. Importantly, the data also show that neither GM-CSF nor CSF-1 is an absolute requirement for the commitment of primitive hematopoietic stem cells to the macrophage lineage or for the differentiation of at least some classes of macrophages. This finding suggests that an alternate regulatory factor can be involved in macrophage and osteoclast commitment, differentiation, and function in vivo.

Haematopoietic radioprotection by Cremophor EL: a polyethoxylated castor oil

The polyethoxylated castor oil, Cremophor EL (Cremophor) is approved for human use as a vehicle for oral and intravenous administration of water-insoluble compounds. Cremophor has also previously been shown to reverse the multidrug resistance phenotype at clinically acceptable doses. This study demonstrates that doses of Cremophor in the range of 25-50 microliters/kg intravenously (i.v.) administered 1 day prior to near-lethal irradiation protected the regenerative capacity of the marrow, resulting in haematopoietic radioprotection and long-term survival of near-lethally-irradiated mice. In normal mice, Cremophor administration (1) markedly reduced the level of serum haematopoietic inhibitory activity 4-8 h following injection; (2) resulted in a transient decrease in femoral bone marrow cellularity and upregulated B220 (B cells), and 7/4 (neutrophils and activated macrophages), but not Thy-1 (T-cells) surface antigen expression in bone marrow cells within 24 h of injection; and (3) transiently elevated the incidence of both primitive and committed haematopoietic progenitor cells detected in clonal agar culture within 48 h of injection. Bone marrow progenitor cell content, and peripheral blood white cell, platelet and reticulocyte counts were unaffected. This suggests that the haematopoietic radioprotection and recovery observed in irradiated mice pretreated with Cremophor may be the result of accessory cell activation and/or modulation of accessory factors regulating haematopoietic progenitor cells. Our data suggest a potential clinical use of Cremophor as an adjunct to, or as a substitute for, cytokines to minimize myelosuppression following cytotoxic therapy.

The development and establishment of hemopoiesis in fetal and newborn osteopetrotic (op/op) mice

Previous studies of young CSF-1-less osteopetrotic (op/op) mice demonstrate a severe deficiency of both macrophages and osteoclasts, resulting in excessive bone formation, occlusion of the marrow cavity, and reduced hemopoietic activity. The accompanying splenomegaly and prolonged splenic hemopoiesis observed in these mice suggests that osteopetrosis may perturb the normal progression of fetal hemopoietic development and obstruct the seeding of hemopoietic precursors into the bone marrow. This study demonstrates that the absence of CSF-1 does not affect the progression of hemopoietic development in fetal op/op mice until after colonization of the bone marrow. Significant deficiencies in marrow cellularity and progenitor cell content in the long bones of op/op mice were not evident prior to Day 2 postnatal, suggesting that the altered hemopoietic state of young op/op mice is not a consequence of abnormal fetal hemopoietic development, but is primarily due to the lack of functional osteoclasts in op/op fetuses and hence, impaired remodeling of the marrow cavity after birth.

Age-related changes in extramedullary hematopoiesis in the spleen of normal and perturbed osteopetrotic (op/op) mice

Occlusion of the marrow cavity by excessive bone formation in young osteopetrotic (op/op) mice results in a significant reduction in the space available for hematopoiesis. At this time, splenomegaly is evident, and the spleen is a site of significant extramedullary hematopoiesis. In vitro clonal assays of spleen cell suspensions in young op/op mice demonstrated a 22-fold elevation in the content of high proliferative potential colony-forming cells (HPP-CFC) (4 weeks of age) and a 14-fold elevation in the content of committed progenitors responsive to colony-stimulating factor-1 (CSF-1) (6 weeks of age). Flow-cytometric analysis also demonstrated a shift in the myeloid:lymphoid cell ratio in the spleens of young op/op mice, with a 35% reduction in the number of B220+ cells, and a two-fold increase in myeloid cells expressing the hematopoietic cell surface lineage antigens Mac-1 and Gr-1. However, the hematopoietic deficiencies of op/op mice are not permanent. An age-related progressive remodeling of the bone marrow cavity results in the correction of bone marrow parameters by 22 weeks of age. This correction in marrow hematopoietic activity is accompanied by a resolution of the splenomegaly, a progressive decrease in splenic hematopoietic activity at both the primitive and committed progenitor cell levels, and a correction of the lymphoid:myeloid cell ratio. Negative immunomagnetic selection of splenic hematopoietic progenitor cells from op/op and control littermate mice, followed by analysis of their expansion in liquid culture, demonstrated that primitive hematopoietic progenitor cells of high proliferative potential continued to reside in the spleen of old op/op mice. The response of these mice to a 5-fluorouracil (5-FU) cytotoxic challenge suggested that this pool of primitive progenitor cells acted as a hematopoietic reserve capable of rapidly responding to hematopoietic perturbation.

Delayed primary closure. Blood-flow in healing rat skin incisions

In an earlier study delayed primary closure (DPC) wounds were shown to develop higher biomechanical strength than primary closure (PC) wounds. In order to elucidate the underlying mechanism, local clearance of 133Xenon and thermography studies were undertaken. A paired comparison design with deposits of 133Xenon injected in the wound margins 3 and 4 days postoperatively, and directly into the wound tissue 10, 20 and 60 days postoperatively was used. Very pronounced differences, with higher blood-flows for DPC wounds, were found in the early measurements. In the later measurements there were significant but less obvious differences. With thermography no differences could be detected. It is concluded that DPC wound have a higher blood-flow, especially in the initial wound healing phase. This supports the hypothesis that an increased blood-flowing during early wound healing is beneficial for the development of mechanical strength in the maturing normal scar.

Calculation of skin temperature increase caused by subcutaneous veins perpendicular to the skin surface

A graphical solution of the temperature increase at the surface of a homogeneous solid due to a linear heat source perpendicular to the surface is given. The calculations correspond to clinical situations for studies of the skin temperature increase over vessels approaching the surface from deeper layers of tissue. Estimations have been made of the maximum distance from the skin surface at which a vein of given diameter may be positioned to be detected in a thermogram. The necessary heat source power to produce a detectable increase in skin temperature is presented graphically as a function of heat source depth. The results can be used for the analysis of the skin temperature pattern by infrared thermography.

Temperature gradients in low-flow vessels

A graphical representation of heat transfer measurements and a graphical solution of the heat transfer equation, describing the temperature changes in a fluid flowing in a pipe localised in a heated or cooled region, are given. The solution is applicable to the axial temperature distribution of the blood in a vessel passing a region of high or lower temperature. An experimental study of the temperature distribution in small pipes with various flow rates and pipe diameters is presented. The results add information on conductive heat distribution in vessels to available knowledge of conductive heat distribution in tissues. The results can be used for the analysis of temperature changes in the vicinity of pathological processes accompanied by vascular changes, e.g. primary venous or arterial disease, inflammatory conditions or neoplasia.

Skin temperature over an artificial heat source implanted in man

The medical application of infrared thermography makes use of the skin temperature as an indication of an underlying pathological process. In order to study the relation between the heat production from a source in living tissue and the overlying skin temperature, artificial heat sources were implanted subcutaneously in human volunteers. The experimental results show that a detectable surface temperature increase over the heat sources presupposes high power output or superficial implantation. The effect of forced convective heat loss from the skin surface and lowered ambient temperature was studied. Forced convection markedly decreased the temperature contrast. An implicit conclusion from experimental and theoretical work is that a localized 'hot spot' can only exceptionally be attributed to metabolic heat production conducted to the skin surface from a buried pathological process. The thermal pattern over a breast tumour, a septic or aseptic inflammation or a tissue injury mainly reflects the vascular reaction.

Analytical calculation of the skin temperature distribution due to subcutaneous heat production in a spherical heat source

An analytical solution of the thermal conductivity equation describing the surface temperature distribution over a buried heat source is given in tabular form. The solution is applicable to experimental models for studies of the surface temperature over an implanted artificial heat source. The results can also be used for the analysis of the skin temperature over biological heat sources such as breat tumours.