Clonal growth of hamster free alveolar cells in soft agar

Differentiation of neonate mouse spermatogonial stem cells on three-dimensional agar/polyvinyl alcohol nanofiber scaffold

Electrospun nanofiber matrices sufficiently mimic the structural morphology of natural extracellular matrix. In this study, we aimed to examine the effects of agar/polyvinyl alcohol nanofiber (PVA) scaffold on the proliferation efficiency and differentiation potential of neonate mouse spermatogonial stem cells (SCCs). Testicular cells were isolated from testes of 40 mouse pups and were seeded in: 1) 2D cell culture plates in the absence (2D/-GF) or presence (2D/+GF) of growth factors and 2) onto agar/PVA scaffold in the absence (3D/-GF) or presence (3D/+GF) of growth factors. The cells were subsequently cultured for 4 weeks. First 2 weeks were dedicated to proliferative phase, whereas the next 2 weeks emphasized the differentiation phase. The identity of the SCCs was investigated at different time-points by flow cytometry and quantitative reverse transcription PCR (qRT-PCR) analyses against the germ cell markers, including PLZF, Id-4, Gfrα-1, Tekt-1, and Sycp-3. After 2 weeks of culture, the 3D/+GF group showed the highest percentage of PLZF-positive cells among culture systems (P < 0.05). The expression levels of pre-meiotic markers (Id-4 and Gfrα-1) decreased significantly in all groups, particularly in 3D/+GF group after 28 days of culture. Additionally, the cells in the 3D/+GF group displayed the highest expression of meiotic (Sycp-3) and post-meiotic markers (Tekt-1) 14 days after differentiation induction. Seemingly, the combination of the agar/PVA scaffold and growth factor-supplemented medium synergistically increased the differentiation rate of mouse SSCs into meiotic and post-meiotic cells. Thus, agar/PVA nanofiber scaffolds may have the potential for applications in the restoration of infertility, especially in azoospermic males.

ABBREVIATIONS

2D: two dimentional; 3D: three dimentional; bFGF: basic fibroblast growth factor; BMP-4: bone morphogenetic protein 4; DMEM: Dulbecco's modified Eagle's medium; ECM: extracellular matrix; FCS: fetal calf serum; FTIR: Fourier-transform infrared spectroscopy; GDNF: glial cell line-derived neurotrophic factor; GF: growth factors; Gfrα-1, GDNF family co-receptor α1; Id-4, Inhibitor of DNA Binding 4; MTT: methylthiazoltetrazolium; PLZF: promyelocytic leukemia zinc finger; PVA: polyvinyl alcohol; qRT-PCR: quantitative reverse transcription PCR; RA: retinoic acid; SACS: soft agar culture system; SD: standard deviation; SEM: scanning electron microscope; SSCs: spermatogonial stem cells; Sycp-3, Synaptonemal complex protein 3; Tekt-1, Tektin 1.

The effects of melatonin on colonization of neonate spermatogonial mouse stem cells in a three-dimensional soft agar culture system

BACKGROUND

Melatonin is a pleiotropic hormone with powerful antioxidant activity both in vivo and in vitro. The present study aimed to investigate the effects of melatonin on the proliferation efficiency of neonatal mouse spermatogonial stem cells (SSCs) using a three-dimensional soft agar culture system (SACS) which has the capacity to induce development of SSCs similar to in vivo conditions.

METHODS

SSCs were isolated from testes of neonate mice and their purities were assessed by flow cytometry using PLZF antibody. Isolated testicular cells were cultured in the upper layer of the SACS in αMEM medium in the absence or presence of melatonin extract for 4 weeks.

RESULTS

The identity of colonies was confirmed by alkaline phosphatase staining and immunocytochemistry using PLZF and α6 integrin antibodies. The number and diameter of colonies of SSCs in the upper layer were evaluated at days 14 and 28 of culture. The number and diameter of colonies of SSCs were significantly higher in the melatonin group compared with the control group. The levels of expression of ID-4 and Plzf, unlike c-kit, were significantly higher in the melatonin group than in the control group.

CONCLUSIONS

Results of the present study show that supplementation of the culture medium (SACS) with 100 μM melatonin significantly decreased reactive oxygen species (ROS) production in the treated group compared with the control group, and increased SSC proliferation.

Fact or fiction: In vitro spermatogenesis

Many previous studies have aimed at spermatogenesis of male murine germ cells in vitro, but no efficient system has been established yet that covers the entire process of mammalian spermatogenesis in a culture dish permanently. In this review, we report on the requirements of spermatogenesis and the current state of different culture methods using testicular tissue fragments, single cell suspensions or three-dimensional culture environments.

Beyond stem cells: self-renewal of differentiated macrophages

In many mammalian tissues, mature differentiated cells are replaced by self-renewing stem cells, either continuously during homeostasis or in response to challenge and injury. For example, hematopoietic stem cells generate all mature blood cells, including monocytes, which have long been thought to be the major source of tissue macrophages. Recently, however, major macrophage populations were found to be derived from embryonic progenitors and to renew independently of hematopoietic stem cells. This process may not require progenitors, as mature macrophages can proliferate in response to specific stimuli indefinitely and without transformation or loss of functional differentiation. These findings suggest that macrophages are mature differentiated cells that may have a self-renewal potential similar to that of stem cells.

Concise review: Spermatogenesis in an artificial three-dimensional system

Culture of spermatogonial stem cells has been performed under a variety of conditions. Most featured two-dimensional systems, with different types of sera, conditioned media, feeder layers, and growth factors. Some have used three-dimensional (3D) matrices produced from gelatin, collagen, or other material. In spite of their increasingly sophisticated composition, however, complete spermatogenesis in vitro has not yet been achieved. In the seminiferous tubules, spermatogenesis occurs in an environment where cells are embedded in a 3D structure with specific niches regulating each stage of germ cell maturation mediated by hormones and paracrine/autocrine factors. We have recently reported achievement of complete in vitro spermatogenesis of mouse testicular germ cells in a 3D culture system featuring a soft agar matrix. This review discusses the advantages of the 3D culture system for studying the spermatogenic process in its entirety. Also discussed are the steps necessary to expand the applicability of the 3D culture system to human germ cell development and determine the functionality of culture-produced spermatozoa for generating offspring.

Measurement of macrophage growth and differentiation

This unit provides protocols for measuring the abundance and growth of macrophage precursors in agar cultures and the proliferation of isolated mature macrophages in vitro, by either direct cell counting or by DNA measurement. Methods for the immunohistochemical identification of macrophages and the determination of their proliferative status in vivo by immunofluorescence are also included. It also describes methods for characterization of macrophage differentiation through the immunofluorescence analysis of cell-surface expression of CSF-1 receptor.

Macrophage development: IV. Effects of blood factors on macrophages from prenatal rat lung cultures

Effects of colony-stimulating factors M-CSF, GM-CSF, G-CSF, and IL-3 were assessed on cells of macrophage lineage present in organ cultured 14-day prenatal rat lungs. Treatment groups were compared between one another and against control lungs grown on standard medium containing 40% fetal bovine serum without added factors, where a monoculture of macrophages rapidly develops from precursors present at explantation, leading to appearance of a large mature population on the pleural surface outside the lungs. Studies were carried out in living cultures and by light and electron microscopy using peroxidase-coupled isolectin B4 of Griffonia simplicifolia to identify macrophages and their precursors. In the first experiment, 14-day prenatal lung explants (14 + 0 days) containing macrophage precursors but not matured cells were exposed to individual CSFs for 7 days in an attempt to determine whether precursors are committed irrevocably to the macrophage line or can be altered by exposure to factors promoting significant granulocyte development. In succeeding experiments, 4- and 7-day-old cultures (14 + 4, 14 + 7 days) containing matured macrophages were targeted to see whether macrophage survival can be extended beyond expectations in controls and whether mitotic activity is stimulated. Recombinant CSFs were used at dosage levels known to promote colony formation in vitro (200-1,000 CFU/ml). Cultures exposed from prenatal day 14 to M-, GM-, G-CSF, or IL-3 yielded a monoculture of macrophages without exception. Populations developed in the presence of M- or GM-CSF were much larger than in controls or cultures grown with the other blood factors. GM-CSF-exposed cultures produced by far the largest macrophages, among them many multinucleate giant cells. Macrophages developed in the presence of G-CSF were also significantly larger than controls. Growth of the mature macrophage population was greatly stimulated by exposure to M-CSF or GM-CSF but not by IL-3 or G-CSF. Mitotic figures were noted in the coronas of emerged cells surrounding stimulated cultures, compared to none in the controls. Ultrastructurally, macrophages stimulated by M-CSF retained a mature appearance like macrophages in control, IL-3, and G-CSF treatment groups, whereas many in the GM-CSF group became less differentiated. As to long-term survival, a single 14-day explant was grown for 8 days on standard medium (the equivalent date for birth), then placed in a soft agar medium containing M-CSF.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth inhibitory factor of human alveolar macrophage

The effect of human lung conditioned medium (HLCM) on the DNA synthesis in cultured human alveolar macrophages (HAM) was evaluated. The medium from human lung cultured for 3 days (3d-HLCM) promoted the DNA synthesis as well as the recombinant human GM-CSF does. On the other hand, that cultured for six days (6d-HLCM) did not promote the DNA synthesis but strongly suppressed GM-CSF induced DNA synthesis in HAM. This growth inhibitory effect was also observed when several macrophage like cell lines were cultured with 6d-HLCM. Partial purification of an inhibitory factor on gel permeation HPLC revealed two distinct peaks of activity with molecular weights of 38 kd and 110 kd.

Activated alveolar macrophages express the insulin-like growth factor-I receptor

Alveolar macrophages (AM) recovered from the lower respiratory tract of individuals with interstitial lung disease (ILD) proliferate at a 2- to 15-fold increased rate (P.B. Bitterman et al. 1984. J. Clin. Invest. 74:460-469). Normal AM stimulated with immune complexes or asbestos release platelet-derived growth factor and insulin-like growth factor-I (IGF-I), and AM activated in vivo in ILD release these growth factors. We evaluated normal unstimulated and activated AM for the receptor for IGF-I to determine if macrophage IGF-I could be involved in the enhanced macrophage proliferation. Although normal AM did not have specific 125I-labeled recombinant IGF-I binding, AM activated by chrysotile asbestos or lipopolysaccharide in vitro or from individuals with ILD had detectable binding that could be inhibited by an anti-IGF-I receptor monoclonal antibody in a dose-dependent fashion. Autoradiography with 125I-labeled recombinant IGF-I revealed binding to the IGF-I receptor on the surface of activated AM, and the percentage of labeled cells was reduced with anti-IGF-I receptor monoclonal antibody or excess unlabeled recombinant IGF-I. Hybridization of total AM RNA to a 32P-labeled IGF-I receptor riboprobe using solution hybridization demonstrated IGF-I receptor mRNA transcripts in AM from an individual with asbestosis, consistent with active expression of the IGF-I receptor gene. In the context of the known role of IGF-I as a growth factor for many cells, these data are consistent with the concept that IGF-I and its receptor may play an important role in the proliferation of AM in the inflamed lower respiratory tract.

A sandwich enzyme-linked immunoadsorbent assay for detection of murine macrophage colony-stimulating factor (CSF-1)

A simple three-layer sandwich enzyme-linked immunoadsorbent assay (sandwich-ELISA) has been developed for murine macrophage colony-stimulating factor-1 (CSF-1) using the two monoclonal antibodies on which we recently reported (J. Immunol. (1988) 141, 483). The anti-CSF-1 monoclonal antibodies used in this assay recognize different epitopes of the same antigen, thereby permitting the detection of low amounts of CSF-1. This assay is specific to murine CSF-1. Recombinant human macrophage colony-stimulating factor, murine GM-CSF, or IL-3, either alone or together with CSF-1, does not interfere with the assay. The advantage of this assay over other reported immunoassays for CSF-1 is that radiolabeled or large quantities of purified CSF-1 are not required. This sandwich-ELISA compares favorably with other assays in its rapidity, simplicity, and sensitivity.

Response of rat alveolar macrophages to ozone: quantitative assessment of population size, morphology, and proliferation following acute exposure

The purpose of this study was to evaluate the in vivo effects of an acute exposure to low levels of ozone on rat pulmonary alveolar macrophages (PAM). Fisher 344 rats exposed to 0.0, 0.12, 0.8, or 1.5 ppm O3 for 6 h were killed immediately after and 3, 18, 42, or 66 h after ozone exposure and their lungs were lavaged. Compared to sham-exposed (control) rats, exposure to 0.12 ppm O3 had no measurable effect on the total number, labeling index (LI), mitotic index (MI), or morphology of rat alveolar macrophages. The number of neutrophils was significantly (p less than or equal to 0.001) greater than in controls at 3, 18, and 42 h after exposure to 1.5 ppm O3 and 42 h after exposure to 0.8 ppm O3. The number of PAM was approximately twice that of controls 42 and 66 h after exposure to 0.8 and 1.5 ppm O3. There was a significant (p less than or equal to 0.001) increase in PAM MI 42 and 66 h after exposure to 1.5 ppm O3 and 42 h after 0.8 ppm O3. The increase in the number of PAM in mitosis was preceded by an increase in PAM LI. The PAM LI was significantly (p less than or equal to 0.001) greater than controls 18 and 42 h after exposure but returned to near normal levels by 66 h after exposure. There was a transient decrease in the mean nuclear/cytoplasmic ratio of PAM from rats exposed to 1.5 ppm O3 18 and 42 h after exposure due to an increase in the mean PAM cytoplasmic area. Comparison of the PAM population doubling time (Dt) and cell cycle time (Ct) suggest that PAM proliferation played a significant role in the observed increase in PAM following exposure to 0.8 and 1.5 ppm O3. These results highlight the dynamic response of PAM to an acute exposure to ozone and suggest that the proliferative response of pulmonary alveolar macrophages may be a useful indicator of pulmonary damage following inhalation of an irritant oxidant.

From growth factor dependence to growth factor responsiveness: the genesis of an alveolar macrophage cell line

A rat pulmonary alveolar macrophage (PAM) cell line (NR8383) was initiated in culture in the presence of a gerbil lung cell conditioned medium (GLCM), and has been propagated continuously for over 36 mo. When examined at different times throughout this in vitro period, NR8383 exhibited characteristics typical of macrophages: (a) Zymosan ingestion was seen in 90 to 98% of the cells examined; (b) Pseudomonas aeruginosa phagocytosis in 50 to 80%; (c) Nonspecific esterase activity in greater than 95%. During the first 6 mo., the PAM replicated with doubling times approximating 15 to 20 d. Throughout this period, GLCM dependence was evident. After 27 wk in vitro, NR8383 replication increased markedly, and within 2 wk, the doubling time was less than 48 h. NR8383 was readily monitored by [3H]thymidine (TdR) blastogenesis assay. In the presence of GLCM uptake of [3H]TdR was fivefold greater than in control cultures. Adherence and growth kinetics were effectively controlled by modulation of GLCM or serum content in culture medium. It was demonstrated that PAM growth factor(s) is ubiquitous, not species-specific, and under certain conditions may be derived from "endogenous" sources of persisting non-PAM populations within the parent, uncloned line NR8383. Cloned progeny remain devoid of non-PAM "feeder" cells, but retain macrophage properties, including interleukin-1 secretion, Fc receptors, and H2O2 production.

Tumorigenicity testing of primate cell lines in nude mice, muscle organ culture and for colony formation in soft agarose

Primate neoplastic and finite cell lines were tested in one in vivo and two in vitro test systems: adult nude mice, muscle organ culture (MOC) and soft agarose (SA). Comparison of the sensitivity of the systems indicated that nude mice were inferior to either in vitro system: WI-38 VA13 (an SV40 transformed cell line) did not cause tumours in these animals yet it behaved as if it were neoplastic in MOC and formed colonies in SA. There was complete correlation between results obtained in MOC and SA. All cell lines which produced tumors in vivo were positive in both in vitro test systems. None of the lines which showed normal patterns in MOC and in SA was tumorigenic in nude mice. Since testing in vitro is simpler, faster, and is thought to be reliable, we recommend SA followed by MOC as the initial assays for determining tumorigenicity of cells.

Alveolar macrophage replication. One mechanism for the expansion of the mononuclear phagocyte population in the chronically inflamed lung

Within any chronically inflamed tissue, there is an increased number of macrophages, pluripotential phagocytic cells that, while critical to host defenses, are also able to profoundly damage parenchymal structure and function. Because of their central role in the inflammatory response, considerable attention has been focused on the mechanisms resulting in an expansion of the macrophage population within an inflamed tissue. Although recruitment of precursor monocytes from the circulation into inflamed tissues clearly plays an important role in macrophage accumulation, it is also possible that replication of tissue macrophages contributes to the expansion of macrophage numbers in inflammation. Because of the accessibility of tissue macrophages with the technique of bronchoalveolar lavage, the lung provides an ideal opportunity to test this hypothesis in humans. To accomplish this, bronchoalveolar lavage was performed to obtain alveolar macrophages from normals (n = 5) and individuals with chronic lung inflammation (normal smokers [n = 5], idiopathic pulmonary fibrosis [n = 13], sarcoidosis [n = 18], and other chronic interstitial lung disorders [n = 11]). Alveolar macrophage replication was quantified by three independent methods: (a) DNA synthesis, assessed by autoradiographic analysis of macrophages cultured for 16 h in the presence of [3H]thymidine; (b) DNA content, assessed by flow cytometric analysis of macrophages fixed immediately after recovery from the lower respiratory tract; and (c) cell division, assessed by cluster formation in semisolid medium. While the proportion of replicating macrophages in normals was very low, there was a 2- to 15-fold increase in this proportion in patients with chronic lung inflammation. In addition, morphologic evaluation demonstrated that individuals with chronic lung inflammation had alveolar macrophages undergoing mitosis. These results suggest that local tissue macrophage replication may play a role in the expansion of the macrophage population in chronic inflammation.

The alveolar macrophage

The pulmonary macrophagic system is critical to the defense of the lung, keeping the alveoli clean and sterile and responding on demand with an adaptive outpouring of new cells into the air sacs. Under basal conditions alveolar macrophages, in common with other mononuclear phagocytes, are derived from the bone marrow. A population of macrophage precursors within the pulmonary interstitium provides a reserve pool capable of proliferation and delivery of phagocytes in response to unusually heavy loads of inhaled particles. This reserve system also produces macrophages when monocytic precursors in the bone marrow are depleted by diseases such as leukemia. The alveolar macrophage is destined to ingest particulate matter and to be eliminated along the mucociliary pathway; clearance by lymphatics is of minor importance and macrophages probably do not recross the alveolar epithelium to reach the pulmonary interstitial compartment. Although the protective role of the macrophage is dominant, this cell may participate, directly or indirectly, in the genesis of two major groups of chronic pulmonary disease, interstitial fibrosis and emphysema. Such inappropriate responses involve interactions with fibroblastic cells and tissue injury initiated by proteases secreted by the macrophage.

Enzyme-linked immunoadsorbent assay for detection of colony-stimulating factor (CSF-1)

An enzyme-linked immunoadsorbent assay (ELISA) has been developed for the quantitative measurement of L-cell colony-stimulating factor (CSF-1). According to this method, purified antigen (CSF-1) was allowed to adsorb to polystyrene or polyvinyl microtiter wells, which were then incubated with specific rat anti-CSF-1 antiserum with or without standard antigen or unknown test samples. The amount of antibody bound to the solid phase was then quantitated by enzyme (horseradish peroxidase)-conjugated rabbit anti-rat immunoglobulin antibody. This assay has a sensitivity comparable to that of the bioassay (approximately 5 U) and can be carried out in a single day.

Binding, internalization and degradation of colony-stimulating factor by peritoneal exudate macrophages

Iodinated colony-stimulating factor produced by L-cells (125I-CSF-1) binds specifically to murine peritoneal exudate macrophages. At 37 degrees C, the cell-bound 125I-CSF-1 was internalized and degraded very rapidly, with the appearance of radioactive iodotyrosine in the medium. At 0 degree C, the cell-bound 125I-CSF-1 was not internalized and degraded, nor did it dissociate from the membrane. The internalization and degradation at 37 degrees C could be blocked or reduced by the presence of phenylglyoxal, methylamine and NH4Cl. The chemical nature of the CSF-1 binding site is polypeptide as judged by its sensitivity to trypsin treatment. After the binding and degradation of unlabeled CSF-1, the exudate cells were no longer able to rebind freshly added 125I-CSF-1, indicating the removal of CSF-1 binding site. The binding capacity of these cells, however, could be restored by prolonged incubation at 37 degrees C but not at 0 degrees C in culture medium containing fetal calf serum.

Clonal proliferation of peritoneal exudate cells from New Zealand black mice: age-related changes

Proliferation and differentiation of peritoneal exudate colony-forming cells (PE-CFC) were examined in BALB/c, C57BL/6, and NZB mice; NZB mice provided an experimental animal model for studies of autoimmunity. At 1 and 12 months of age, the number of PE-CFC from NZB mice was significantly less than the number of PE-CFC for other tested strains, whereas the number of clusters formed was reduced only in the older NZB mice. In contrast, 1- to 12-month-old BALB/c and C57BL/6 mice showed no significant age or strain-dependent alterations in PE-CFC. Although the latency period preceding colony growth remained constant for all strains and ages, significant variation in colony size was observed for NZB mice; the largest colonies were noted in the oldest group. We also observed age-associated variations in colony morphology; therefore, age- and strain-dependent differences may exist in the differentiation or functional attributes of PE-CFC subpopulations. The results specifically indicate that NZB mice have age-related alterations in PEC proliferative and differentiation capacities.

Distribution of cells bearing receptors for a colony-stimulating factor (CSF-1) in murine tissues

CSF-1 is a subclass of the colony-stimulating factors that specifically stimulates the growth of mononuclear phagocytes. We used the binding of 125I-CSF-1 at 0 degrees C by single cell suspensions from various murine tissues, in conjunction with radioautography, to determine the frequency of binding cells, their identity, and the number of binding sites per binding cell. For all tissues examined, saturation of binding sites was achieved within 2 h at 2--3 x 10(-10) M 125I-CSF-1. The binding was irreversible and almost completely blocked by a 2 h preincubation with 5 x 10(-10) M CSF-1. 125I-CSF-1 binding was exhibited by 4.3% of bone marrow cells, 7.5% of blood mononuclear cells, 2.4% of spleen cells, 20.5% of peritoneal cells, 11.8% of pulmonary alveolar cells and 0.4% of lymph node cells. Four morphologically distinguishable cell types bound 125I-CSF-1: blast cells; mononuclear cells with a ratio of nuclear to cytoplasmic area (N/C) greater than 1; cells with indented nuclei; and mononuclear cells with N/C less than or equal to 1. No CSF-1 binding cells were detected among blood granulocytes or thymus cells. Bone marrow promyelocytes, myelocytes, neutrophilic granulocytes, eosinophilic granulocytes, nucleated erythroid cells, enucleated erythrocytes, and megakaryocytes also failed to bind. The frequency distribution of grain counts per cell for blood mononuclear cells was homogenous. In contrast, those for bone marrow, spleen, alveolar, and peritoneal cells were heterogeneous. The monocytes in blood or bone marrow (small cells, with either indented nuclei or with N/C greater than 1) were relatively uniformly labeled, possessing approximately 3,000 binding sites per cell. Larger binding cells (e.g., alveolar cells) may possess higher numbers of receptors. It is concluded that CSF-1 binding is restricted to mononuclear phagocytic cells and their precursors and that it can be used to identify both mature and immature cells of this series.

Enhancement of the growth of blood monocytes in agar cultures by haemolysates

Mouse blood monocytes grow well in liquid but poorly in agar medium. In this study the effect of haemolysate on the clonal growth of blood monocytes in agar cultures was investigated. The results suggested that haemolysate from mouse or rat red blood cells contains a factor(s) that can render the murine blood monocytes able to grow well in agar culture (anchorage-independent growth). The mechanism of action of the enhancing factor(s) is discussed.

Relationship of prostaglandin secretion by rabbit alveolar macrophages to phagocytosis and lysosomal enzyme release

The phospholipids of rabbit alveolar macrophages were pulse-labelled with [(14)C]-arachidonic acid, and the subsequent release of labelled prostaglandins was measured. Resting macrophages released measurable amounts of arachidonic acid, the prostaglandins E(2), D(2) and F(2alpha) and 6-oxoprostaglandin F(1alpha). Phagocytosis of zymosan increased the release of arachidonic acid and prostaglandins to 2.5 times the control value. In contrast, phagocytosis of inert latex particles had no effect on prostaglandin release. Indomethacin inhibited the release of prostaglandin, and, at high doses (20mug/ml), increased arachidonic acid release. Analysis of the cellular lipids showed that after zymosan stimulation the proportion of label was decreased in phosphatidylcholine, but not in other phospholipids or neutral lipids. Cytochalasin B, at a dose of 2mug/ml, inhibited the phagocytosis induced by zymosan but increased prostaglandin synthesis to 3.4 times the control. These data suggest that the stimulation of prostaglandin synthesis by zymosan is not dependent on phagocytosis. Exposure to zymosan also resulted in the release of the lysosomal enzyme, acid phosphatase. Furthermore, cytochalasin B augmented the zymosan-stimulated release of acid phosphatase at the same dose that stimulated prostaglandin synthesis. However, indomethacin, at a dose that completely inhibited prostaglandin synthesis, failed to block the lysosomal enzyme release. Thus despite some parallels between the release of prostaglandins and lysosomal enzymes, endogenous prostaglandins do not appear to mediate the release of lysosomal enzymes. The prostaglandins released from the macrophages may function as humoral substances affecting other cells.

Secretion of plasminogen activator by bone marrow-derived mononuclear phagocytes and its enhancement by colony-stimulating factor

We have studied the production of plasminogen activator (PA) by mononuclear phagocytes derived from mouse bone marrow precursor cells (CFU-C) in culture. Bone marrow-derived macrophages (BMDM) obtained after 6-8-d cultivation in a liquid medium containing L-cell-conditioned medium (LCM), a source of colony stimulating factor (CSF), showed a high level of fibrinolytic activity comparable to that of thioglycollate medium-induced peritoneal macrophages (TPM) and at least 20-fold higher than that of resident peritoneal macrophages (RPM). Fibrinolysis was a result of active secretion of PA into the culture medium and plaques of caseinolysis could be detected by an overlay assay over all macrophage colonies formed after cloning of bone marrow cells in culture. When the fibrinolytic activity of BMDM harvested at different times was investigated, it was found that the level of PA activity of a given BMDM population correlated well with the incidence of cells (5-15 percent) able to proliferate and form colonies in agar after 7-14 d, somewhat more slowly than CFU-C. This correlation between the level of PA secretion and the incidence of agar colony-forming cells was also found with other mononuclear phagocyte populations. Active fibrinolysis and slow growing colony-forming cells were observed at the same time as adherent macrophages appeared, 2-3 d after the start of bone marrow culture, they persisted for 10 d before declining. Some of the factors which influenced PA production by BMDM were examined. Fibrinolysis could be enhanced two- to fourfold by exposing the cells for 4 h to concanavalin A (Con A), to medium conditioned by Con A-stimulated spleen cells and to LCM, but not by phagocytosis of latex particles. The substance in LCM that stimulated PA production appeared to be identical to CSF. Mononuclear phagocyte targets differed in their response to LCM, which stimulated fibrinolysis readily in BMDM, to a lesser extent in TPM and not at all in RPM. We conclude that CSF stimulates both proliferation and fibrinolytic activity in BMDM and that the level of macrophage activation, as defined by PA production, can be further enhanced by lymphokines. Induction of PA in BMDM provides a rapid and sensitive assay for measuring the activity of CSF and defining its role in macrophage activation.

Cellular tumorigenicity in nude mice. Test of associations among loss of cell-surface fibronectin, anchorage independence, and tumor-forming ability

Fibronectin (FN; also called large external transformation-sensitive [LETS] protein or cell-surface protein [CSP]) is a large cell-surface glycoprotein that is frequently observed to be either absent or greatly reduced on the surfaces of malignant cells grown in vitro. Because FN may be a useful molecular marker of cellular malignancy, we have carried out an extensive screening to test the specific association among the degree of expression of FN, anchorage-independent growth, and tumorigenicity in the athymic nude mouse. A variety of diploid cell strains and established cell lines were tested for the expression of surface FN by indirect immunofluorescence using rabbit antisera against human cold insoluble globulin, rodent plasma FN, or chicken cell-surface FN. Concomitantly, the cells were assayed for tumor formation in nude mice and for the ability to form colonies in methylcellulose. Tumorigenic cells often showed very low surface fluorescence, confirming earlier reports. However, many highly tumorigenic fibroblast lines from several species stained strongly with all three antisera. In contrast, the anchorage-independent phenotype was nearly always associated with tumorigenicity in approximately 35 cell lines examined in this study. In another series of experiments, FN-positive but anchorage-independent cells were grown as tumors in nude mice and then reintroduced into culture. In five of the six tumor-derived cell lines, cell-surface FN was not significantly reduced; one such cell line showed very little surface FN. Our data thus indicate that the loss of cell-surface FN is not a necessary step in the process of malignant transformation and that the growth of FN-positive cells as tumors does not require a prior selection in vivo for FN-negative subpopulations.

Pulmonary macrophage growth factor

Pulmonary macrophage growth factor (MCF) can be purified from the "used" serum-free medium of cultures of mouse lung cells by concentration and dialysis over a 30,000-dalton Amicon ultrafilter and subjecting the retentate to isoelectric focusing. This yields a protein fraction with an isolelectric point of pH 4.2, which contains all the MGF activity. Upon electrophoresis of this fraction in analytical gels, one large and four small bands could be visualized. All bands were biologically active. This same "heterogenous" fraction ran as one band (mol wt 68,000) in SDS analytical gel electrophoresis, suggesting the ordered aggregation of this monomer. This was confirmed by reelectrophoresis of the first (and largest) band demonstrating the same 5-banded pattern as the initial material.

Origin, Kinetics, and characteristics of pulmonary macrophages in the normal steady state

Pulmonary macrophages of mice in the steady state were isolated by lavage with PBS containing EDTA and subsequent enzymatic digestion of tissue with pronase and DNA-ase. By this method, the total pulmonary macrophage population was obtained in two cell suspensions, one with a pure population of pulmonary alveolar macrophages (PAM) and the other with a mixed population of pulmonary alveolar and pulmonary tissue macrophages (PTM). The morphological, cytochemical, and functional characteristics of both PAM and PTM were like those of mature tissue macrophages except for the presence of C3 receptors. These receptors were almost absent on PAM and present on a larger number of cells in the mixed population of PAM and PTM. The total pulmonary macrophage population of mice in the steady state is approximately equal to 2 x 10(6), of which about 93% are PAM and about 7% are PTM. In labeling experiments with 3H-thymidine, the low in vitro labeling indices (less than 3%) for both PAM and the mixture of PAM and PTM, showed that both are essentially nondividing cells. In vivo labeling studies showed an increase in the number of labeled macrophages that can only be attributed to labeled monocytes migrating into the lungs. Additional evidence was provided by a decrease in the labeling indices of pulmonary macrophages when mice were treated with hydrocortisone acetate, which causes a severe monocytopenia, thus preventing monocyte influx into the lungs. Confirmation of the bone marrow origin was obtained in mice labeled after x-irradiation with partial bone marrow shielding: labeled pulmonary macrophages were found in the exposed lungs. In all experiments, the labeling indices were identical in the two macrophage populations isolated. These results show that the influx of monocytes is the source of cell renewal for the pulmonary macrophages. No indications for an interstitial division or maturation compartment in the lung were found. Quantitation of the efflux of labeled monocytes from the blood, and the number of labeled pulmonary macrophages, showed that in the steady state about 15% of the monocytes leaving the circulation become pulmonary macrophages and that the turnover time of pulmonary macrophages is approximately equal to 27 d.

Detection of in vitro macrophage colony-forming cells (M-CFC) in mouse bone marrow, spleen, and peripheral blood

In vitro macrophage colony-forming cells (M-CFC) have been detected in bone marrow (BM) (317/10(5) cells), spleen (SPL) (81/10(5)), and peripheral blood leukocytes (PBL) (242/10(5)) of the mouse. These M-CFCs were similar to those previously detected in thymus (T) (30/10(6)) and lymph node (LN) (22/10(6)) tissue in several respects. BM- and SPL-derived M-CFC required PMUE to consistently initiate colony formation, whereas PBL-derived M-CFC formed colonies with stimulation by either PMUE or L-cell-conditioned medium. All colonies formed showed a singular macrophage line of differentiation, a lag of 13 to 18 days prior to initiating colony formation, a marked ability to survive in culture in the absence of PMUE, and markedly slow rates of appearance in culture once colony formation was initiated. The macrophage progeny were identified on the basis of morphology, glass adherence, the phagocytosis of agar, bacteria and SRBC, and the presence of receptors for IgG. These characteristics are also shared by those macrophage CFCs observed within stimulated peritoneal exudate, pleural effusion, and alveolar space. These M-CFCs are most likely members of a large, heterogeneous population of macrophage progenitor cells distributed throughout the hemato-lymphopoietic organs, serosal cavities and surfaces, and inflammatory and alveolar tissue sites. The degree of heterogeneity may be determined in part by the influence of tissue-specific microenvironment.

Cytocidal activity and proliferative ability of macrophages infiltrating the EMT6 tumor

The EMT6 mouse tumor was selected for use in the study of cytocidal activity and proliferative ability of infiltrating macrophages because of its high plating efficiency when explanted to culture. The plating efficiency for cells directly plated in culture from the tumor was 28 +/- 9.3%, irrespective of the size of the tumor. Of the adherent cells derived from the tumor, the fraction that was macrophages increased from 27% at 7 days to 47% at 28 days after initial injection. Time-lapse cinemicrography was used to directly observe adherent cells derived from the tumor, and macrophages were found to be cytocidal. When grown in the presence of L-cell conditioned medium no macrophage colonies were found when cultures were established from untreated mice even though most tumor cell colonies contained macrophages. When mice were first treated with 0.8 mg BCNU prior to establishment of the cultures, in order to reduce the frequency of colony-forming tumor cells, approximately half the colonies found contained only macrophages. These results show that macrophages in this tumor are cytocidal and capable of proliferation.

Peritoneal exudate cells. V. Influence of age, sex, strain and species on the induction and the growth of macrophage colony forming cells

We investigated the effects of age, sex and strain in the induction of peritoneal exudate colony-forming cells (PE-CFC) in mice. Sex and age (ranging from 3 weeks to 12 months) had no significant effect on the induction of PE-CFC. However, we found significant difference between strains in terms of the number of nucleated cells and the proportion of PE-CFC in exudate cells. When we investigated the mechanisms behind this strain difference, we found that it was due to neither the type of colony-stimulating factor employed in culture, nor the type of stimulants used to induce the exudate, nor the difference in the kinetics of appearance of PE-CFC in the peritoneal cavity. We also studied the induction of PE-CFC in rats and hamsters and the growth of these cells in vitro. Unlike mouse cells, PE-CFC from rats and hamsters could also use media conditioned by cells from other species as a source of colony-stimulating factor.

The detection of in vitro monocyte-macrophage colony-forming cells in mouse thymus and lymph nodes

In vitro monocyte-macrophage colony-forming cells (CFC) have been detected in the thymus (30/10(6) cells) and in the cervical (22/10(6)) and mesenteric (20/10(6)) lymph nodes (LN) of the mouse. Thymus and LN derived CFC differed from bone marrow derived CFU-c in several characteristics parameters: (1) sole specificity of PMUE to induce colony formation (CF), (2) apparent singular line of monocyte-macrophage differentiation, (3) a marked 6- to 10-day lag period prior to initiation of CF, and (4) significantly slower rates of appearance of colonies in culture after initiation of CF. Two of these parameters are shared with those CFC detected within alveolar space, peritoneal exudate and pleural effusion. These are the delay prior to CF and the singular monocyte-macrophage differentiation. These similarities suggested that T-CFC and LN-CFC are probably of similar origin and represent, as suggested by Lin and Stewart ('74), a population of progenitor cells exclusively for monocyte-macrophages.