CSF-1 treatment promotes angiogenesis in the metaphysis of osteopetrotic (toothless, tl) rats

The influence of M-CSF on fracture healing in a mouse model

Macrophage colony-stimulating factor 1 (M-CSF) is known to play a critical role during fracture repair e.g. by recruiting stem cells to the fracture site and impacting hard callus formation by stimulating osteoclastogenesis. The aim of this experiment was to study the impact of systemic M-CSF application and its effect on bony healing in a mouse model of femoral osteotomy. Doing so, we studied 61 wild type (wt) mice (18-week-old female C57BL/6) which were divided into three groups: (1) femoral osteotomy, (2) femoral osteotomy + stabilization with external fixator and (3) femoral osteotomy + stabilization with external fixator + systemic M-CSF application. Further, 12 op/op mice underwent femoral osteotomy and served as proof of concept. After being sacrificed at 28 days bony bridging was evaluated ex vivo with µCT, histological and biomechanical testing. Systemic M-CSF application impacted osteoclasts numbers, which were almost as low as found in op/op mice. Regarding callus size, the application of M-CSF in wt mice resulted in significantly larger calluses compared to wt mice without systemic M-CSF treatment. We further observed an anabolic effect of M-CSF application resulting in increased trabecular thickness compared to wt animals without additional M-CSF application. Systemic M-CSF application did not alter biomechanical properties in WT mice. The impact of M-CSF application in a mouse model of femoral osteotomy was oppositional to what we were expecting. While M-CSF application had a distinct anabolic effect on callus size as well as trabecular thickness, this on bottom line did not improve biomechanical properties. We hypothesize that in addition to the well-recognized negative effects of M-CSF on osteoclast numbers this seems to further downstream cause a lack of feedback on osteoblasts. Ultimately, continuous M-CSF application in the absence of co-stimulatory signals (e.g. RANKL) might overstimulate the hematopoietic linage in favor of tissue macrophages instead of osteoclasts.

Treatment with a long-acting chimeric CSF1 molecule enhances fracture healing of healthy and osteoporotic bones

Macrophage-targeted therapies, including macrophage colony-stimulating factor 1 (CSF1), have been shown to have pro-repair impacts post-fracture. Preclinical/clinical applications of CSF1 have been expedited by development of chimeric CSF1-Fc which has extended circulating half-life. Here, we used mouse models to investigate the bone regenerative potential of CSF1-Fc in healthy and osteoporotic fracture. We also explored whether combination of CSF1-Fc with interleukin (IL)-4 provided additional fracture healing benefit in osteopenic bone. Micro-computed tomography, in situ histomorphometry, and bone mechanical parameters were used to assess systemic impacts of CSF1-Fc therapy in naive mice (male and female young, adult and geriatric). An intermittent CSF1-Fc regimen was optimized to mitigate undesirable impacts on bone resorption and hepatosplenomegaly, irrespective of age or gender. The intermittent CSF1-Fc regimen was tested in a mid-diaphyseal femoral fracture model in healthy bones with treatment initiated 1-day post-fracture. Weekly CSF1-Fc did not impact osteoclasts but increased osteal macrophages and improved fracture strength. Importantly, this treatment regimen also improved fracture union and strength in an ovariectomy-model of delayed fracture repair. Combining CSF1-Fc with IL-4 initiated 1-week post-fracture reduced the efficacy of CSF1-Fc. This study describes a novel strategy to specifically achieve bone regenerative actions of CSF1-Fc that has the potential to alleviate fragility fracture morbidity and mortality.

Pleiotropic Impacts of Macrophage and Microglial Deficiency on Development in Rats with Targeted Mutation of the Csf1r Locus

We have produced Csf1r-deficient rats by homologous recombination in embryonic stem cells. Consistent with the role of Csf1r in macrophage differentiation, there was a loss of peripheral blood monocytes, microglia in the brain, epidermal Langerhans cells, splenic marginal zone macrophages, bone-associated macrophages and osteoclasts, and peritoneal macrophages. Macrophages of splenic red pulp, liver, lung, and gut were less affected. The pleiotropic impacts of the loss of macrophages on development of multiple organ systems in rats were distinct from those reported in mice. Csf1r^-/- rats survived well into adulthood with postnatal growth retardation, distinct skeletal and bone marrow abnormalities, infertility, and loss of visceral adipose tissue. Gene expression analysis in spleen revealed selective loss of transcripts associated with the marginal zone and, in brain regions, the loss of known and candidate novel microglia-associated transcripts. Despite the complete absence of microglia, there was little overt phenotype in brain, aside from reduced myelination and increased expression of dopamine receptor-associated transcripts in striatum. The results highlight the redundant and nonredundant functions of CSF1R signaling and of macrophages in development, organogenesis, and homeostasis.

Implantation of a Poly-L-Lactide GCSF-Functionalized Scaffold in a Model of Chronic Myocardial Infarction

A previously developed poly-l-lactide scaffold releasing granulocyte colony-stimulating factor (PLLA/GCSF) was tested in a rabbit chronic model of myocardial infarction (MI) as a ventricular patch. Control groups were constituted by healthy, chronic MI and nonfunctionalized PLLA scaffold. PLLA-based electrospun scaffold efficiently integrated into a chronic infarcted myocardium. Functionalization of the biopolymer with GCSF led to increased fibroblast-like vimentin-positive cellular colonization and reduced inflammatory cell infiltration within the micrometric fiber mesh in comparison to nonfunctionalized scaffold; PLLA/GCSF polymer induced an angiogenetic process with a statistically significant increase in the number of neovessels compared to the nonfunctionalized scaffold; PLLA/GCSF implanted at the infarcted zone induced a reorganization of the ECM architecture leading to connective tissue deposition and scar remodeling. These findings were coupled with a reduction in end-systolic and end-diastolic volumes, indicating a preventive effect of the scaffold on ventricular dilation, and an improvement in cardiac performance.

Transcriptome sequencing reveals differences between primary and secondary hair follicle-derived dermal papilla cells of the Cashmere goat (Capra hircus)

The dermal papilla is thought to establish the character and control the size of hair follicles. Inner Mongolia Cashmere goats (Capra hircus) have a double coat comprising the primary and secondary hair follicles, which have dramatically different sizes and textures. The Cashmere goat is rapidly becoming a potent model for hair follicle morphogenesis research. In this study, we established two dermal papilla cell lines during the anagen phase of the hair growth cycle from the primary and secondary hair follicles and clarified the similarities and differences in their morphology and growth characteristics. High-throughput transcriptome sequencing was used to identify gene expression differences between the two dermal papilla cell lines. Many of the differentially expressed genes are involved in vascularization, ECM-receptor interaction and Wnt/β-catenin/Lef1 signaling pathways, which intimately associated with hair follicle morphogenesis. These findings provide valuable information for research on postnatal morphogenesis of hair follicles.

Meox2Cre-mediated disruption of CSF-1 leads to osteopetrosis and osteocyte defects

CSF-1, a key regulator of mononuclear phagocyte production, is highly expressed in the skeleton by osteoblasts/osteocytes and in a number of nonskeletal tissues such as uterus, kidney and brain. The spontaneous mutant op/op mouse has been the conventional model of CSF-1 deficiency and exhibits a pleiotropic phenotype characterized by osteopetrosis, and defects in hematopoiesis, fertility and neural function. Studies to further delineate the biologic effect of CSF-1 within various tissues have been hampered by the lack of suitable models. To address this issue, we generated CSF-1 floxed/floxed mice and demonstrate that Cre-mediated recombination using Meox2Cre, a Cre line expressed in epiblast during early embryogenesis, results in mice with ubiquitous CSF-1 deficiency (CSF-1KO). Homozygous CSF-1KO mice lacked CSF-1 in all tissues and displayed, in part, a similar phenotype to op/op mice that included: failure of tooth eruption, osteopetrosis, reduced macrophage densities in reproductive and other organs and altered hematopoiesis with decreased marrow cellularity, circulating monocytes and B cell lymphopoiesis. In contrast to op/op mice, CSF-1KO mice showed elevated circulating and splenic T cells. A striking feature in CSF-1KO mice was defective osteocyte maturation, bone mineralization and osteocyte-lacunar system that was associated with reduced dentin matrix protein 1 (DMP1) expression in osteocytes. CSF-1KO mice also showed a dramatic reduction in osteomacs along the endosteal surface that may have contributed to the hematopoietic and cortical bone defects. Thus, our findings show that ubiquitous CSF-1 gene deletion using a Cre-based system recapitulates the expected osteopetrotic phenotype. Moreover, results point to a novel link between CSF-1 and osteocyte survival/function that is essential for maintaining bone mass and strength during skeletal development.

Macrophages in renal development, injury, and repair

Macrophages have long been regarded as classic mediators of innate immunity because of their production of proinflammatory cytokines and their ability to induce apoptotic cell death. As a result of such activities and the detrimental long-term effect of kidney inflammation, macrophages principally have been regarded as mediators of glomerular damage, tubular cell death, and the downstream fibrotic events leading to chronic kidney disease. Although this has been the accepted consequence of macrophage infiltration in kidney disease, macrophages also play a critical role in normal organ development, cell turnover, and recovery from injury in many organs, including the kidney. There is also a growing awareness that there is considerable heterogeneity of phenotype and function within the macrophage population and that a greater understanding of these different states of activation may result in the development of therapies specifically designed to capitalize on this variation in phenotype and cellular responses. In this review, we discuss the current understanding of induction and consequences of classic versus alternative macrophage activation and highlight what additional therapeutic options this may provide for the management of both acute and chronic kidney disease as well as renal cancer.

A G-CSF functionalized scaffold for stem cells seeding: a differentiating device for cardiac purposes

Myocardial infarction and its consequences represent one of the most demanding challenges in cell therapy and regenerative medicine. Transfer of skeletal myoblasts into decompensated hearts has been performed through intramyocardial injection. However, the achievements of both cardiomyocyte differentiation and precise integration of the injected cells into the myocardial wall, in order to augment synchronized contractility and avoid potentially life-threatening alterations in the electrical conduction of the heart, still remain a major target to be pursued. Recently, granulocytes colony-stimulating factor (G-CSF) fuelled the interest of researchers for its direct effect on cardiomyocytes, inhibiting both apoptosis and remodelling in the failing heart and protecting from ventricular arrhythmias through the up-regulation of connexin 43 (Cx43). We propose a tissue engineering approach concerning the fabrication of an electrospun cardiac graft functionalized with G-CSF, in order to provide the correct signalling sequence to orientate myoblast differentiation and exert important systemic and local effects, positively modulating the infarction microenvironment. Poly-(L-lactide) electrospun scaffolds were seeded with C2C12 murine skeletal myoblast for 48 hrs. Biological assays demonstrated the induction of Cx43 expression along with morphostructural changes resulting in cell elongation and appearance of cellular junctions resembling the usual cardiomyocyte arrangement at the ultrastructural level. The possibility of fabricating extracellular matrix-mimicking scaffolds able to promote myoblast pre-commitment towards myocardiocyte lineage and mitigate the hazardous environment of the damaged myocardium represents an interesting strategy in cardiac tissue engineering.

Elevated levels of macrophage colony-stimulating factor in human fracture healing

Macrophage colony-stimulating factor (M-CSF) plays a unique role in bone remodeling. However, to our knowledge, no data on the role of M-CSF in fracture healing in humans have been published so far. This study addressed this issue. One hundred and thirteen patients with long-bone fractures were included in the study and divided into two groups, according to their course of fracture healing. The first group contained 103 patients with normal fracture healing. Ten patients with impaired fracture healing formed the second group of the study. Volunteers donated blood samples as control. Serum samples were collected over a period of 6 months, following a standardized time schedule. In addition, M-CSF levels were measured in fracture hematoma and serum of 11 patients with bone fractures. M-CSF concentrations were measured by enzyme-linked immunosorbent assay (ELISA). Fracture hematoma contained significantly higher M-CSF concentrations compared to M-CSF concentrations in patient's serum. M-CSF levels in fracture hematoma and in patient's serum were both significantly higher than M-CSF concentrations measured in serum of healthy controls. Highly elevated M-CSF serum concentrations were found in patients with physiological fracture healing over the entire observation period. Significant differences in the M-CSF serum concentration between patients with normal fracture healing and patients with impaired fracture healing were not observed. This study indicates, for the first time, to our knowledge, a possible local and systemic involvement of M-CSF in humans during fracture healing.

Stromal cell-derived CSF-1 blockade prolongs xenograft survival of CSF-1-negative neuroblastoma

The molecular mechanisms of tumor-host interactions that render neuroblastoma (NB) cells highly invasive are unclear. Cancer cells upregulate host stromal cell colony-stimulating factor-1 (CSF-1) production to recruit tumor-associated macrophages (TAMs) and accelerate tumor growth by affecting extracellular matrix remodeling and angiogenesis. By coculturing NB with stromal cells in vitro, we showed the importance of host CSF-1 expression for macrophage recruitment to NB cells. To examine this interaction in NB in vivo, mice bearing human CSF-1-expressing SK-N-AS and CSF-1-negative SK-N-DZ NB xenografts were treated with intratumoral injections of small interfering RNAs directed against mouse CSF-1. Significant suppression of both SK-N-AS and SK-N-DZ NB growth by these treatments was associated with decreased TAM infiltration, matrix metalloprotease (MMP)-12 levels and angiogenesis compared to controls, while expression of tissue inhibitors of MMPs increased following mouse CSF-1 blockade. Furthermore, Tie-2-positive and -negative TAMs recruited by host CSF-1 were identified in NB tumor tissue by confocal microscopy and flow cytometry. However, host-CSF-1 blockade prolonged survival only in CSF-1-negative SK-N-DZ NB. These studies demonstrated that increased CSF-1 production by host cells enhances TAM recruitment and NB growth and that the CSF-1 phenotype of NB tumor cells adversely affects survival.

Septoclast deficiency accompanies postnatal growth plate chondrodysplasia in the toothless (tl) osteopetrotic, colony-stimulating factor-1 (CSF-1)-deficient rat and is partially responsive to CSF-1 injections

The septoclast is a specialized, cathepsin B-rich, perivascular cell type that accompanies invading capillaries on the metaphyseal side of the growth plate during endochondral bone growth. The putative role of septoclasts is to break down the terminal transverse septum of growth plate cartilage and permit capillaries to bud into the lower hypertrophic zone. This process fails in osteoclast-deficient, osteopetrotic animal models, resulting in a progressive growth plate dysplasia. The toothless rat is severely osteopetrotic because of a frameshift mutation in the colony-stimulating factor-1 (CSF-1) gene (Csf1(tl)). Whereas CSF-1 injections quickly restore endosteal osteoclast populations, they do not improve the chondrodysplasia. We therefore investigated septoclast populations in Csf1(tl)/Csf1(tl) rats and wild-type littermates, with and without CSF-1 treatment, at 2 weeks, before the dysplasia is pronounced, and at 4 weeks, by which time it is severe. Tibial sections were immunolabeled for cathepsin B and septoclasts were counted. Csf1(tl)/Csf1(tl) mutants had significant reductions in septoclasts at both times, although they were more pronounced at 4 weeks. CSF-1 injections increased counts in wild-type and mutant animals at both times, restoring mutants to normal levels at 2 weeks. In all of the mutants, septoclasts seemed misoriented and had abnormal ultrastructure. We conclude that CSF-1 promotes angiogenesis at the chondroosseous junction, but that, in Csf1(tl)/Csf1(tl) rats, septoclasts are unable to direct their degradative activity appropriately, implying a capillary guidance role for locally supplied CSF-1.

The impact of colony-stimulating factor-1 on fracture healing: an experimental study

The role of colony stimulating factor-1 (CSF-1) in the regulation of osteoclasts and bone remodeling suggests that CSF-1 may also be involved in regulation of bone healing. The ability of CSF-1 to promote healing of bone defects was tested in a rabbit model. Twenty-four New Zeeland rabbits were included in the study. Animals were assigned to two groups: the control group (n = 12) was treated by plate fixation. The animals in the second group (n = 12) were also stabilized by conventional plating and received additionally CSF-1 for 2 weeks systemically. Histologic, histomorphometric, and radiologic examinations were performed to evaluate the healing process at 4, 8, and 12 weeks following surgery. Animals that were treated by CSF-1 produced a significantly higher amount of mineralized bone over the first 8 weeks after fracture compared to the control animals. Furthermore, a higher number of osteoclasts was found in CSF-1-treated animals within the first 8 weeks, compared to the controls. The present data emphasize for the first time the importance of CSF-1 in the bone healing. The use of CSF-1 in addition to conventional fixation might be a novel approach for the treatment of bone defects.

Enhanced c-Fms/M-CSF receptor signaling and wound-healing process in bone marrow-derived macrophages of signal-transducing adaptor protein-2 (STAP-2) deficient mice

Signal-transducing adaptor protein-2 (STAP-2) is a recently identified adaptor protein as a c-Fms/M-CSF receptor-interacting protein and constitutively expressed in macrophages. In our previous study, we examined the role of STAP-2 in the c-Fms/M-CSF receptor signaling using a murine macrophage tumor cells line, Raw264.7. Overexpression of STAP-2 in Raw264.7 cells markedly suppressed M-CSF-induced activation of extracellular signal regulated kinase and Akt. In addition, Raw264.7 overexpressing STAP-2 affected cell migration in wound-healing process. These results suggest that STAP-2 deficiency influences endogenous c-Fms/M-CSF receptor signaling. Here we show that loss of STAP-2 expression in knockout mouse macrophages results in marked enhancement of the c-Fms/M-CSF receptor signaling and wound-healing process. We therefore propose that STAP-2 acts as an endogenous regulator in normal macrophages functions.

Colony-stimulating factor-1 transfection of myoblasts improves the repair of failing myocardium following autologous myoblast transplantation

AIMS

Skeletal myoblasts are used in repair of ischaemic myocardium. However, a large fraction of grafted myoblasts degenerate upon engraftment. Colony-stimulating factor-1 (CSF-1) accelerates myoblast proliferation and angiogenesis. We hypothesized that CSF-1 overexpression improves myoblast survival and cardiac function in ischaemia-induced heart failure.

METHODS AND RESULTS

Three weeks following myocardial infarction, rats developed heart failure and received intramyocardial injections of mouse CSF-1-transfected or untransfected primary autologous rat myoblasts, recombinant human CSF-1, mouse CSF-1 expressing plasmids, or culture medium. Tissue gene and protein expression was measured by quantitative RT-PCR (reverse transcription-polymerase chain reaction) and western blotting. Fluorescence imaging and immunocytochemistry were used to analyse myoblasts, endothelial cells, macrophages, and infarct wall thickening. Electrocardiograms were recorded online using a telemetry system. Left ventricular function was assessed by echocardiography over time, and improved significantly only in the CSF-1-overexpressing myoblast group. CSF-1-overexpression enhanced myoblast numbers and was associated with an increased infarct wall thickness, enhanced angiogenesis, increased macrophage recruitment and upregulated matrix metalloproteases (MMP)-2 and -12 in the zone bordering the infarction. Transplantation of CSF-1-overexpressing myoblasts did not result in major arrhythmias.

CONCLUSION

Autologous intramyocardial transplantation of CSF-1 overexpressing myoblasts might be a novel strategy in the treatment of ischaemia-induced heart failure.

Circulating colony stimulating factor-1 and breast cancer risk

Colony stimulating factor-1 (CSF1) and its receptor (CSF1-R) are important in mammary gland development and have been implicated in breast carcinogenesis. In a nested case-control study in the Nurses' Heath Study of 726 breast cancer cases diagnosed between June 1, 1992, and June 1, 1998, and 734 matched controls, we prospectively evaluated whether circulating levels of CSF1 (assessed in 1989-1990) are associated with breast cancer risk. The association varied by menopausal status (P(heterogeneity) = 0.009). CSF1 levels in the highest quartile (versus lowest) were associated with an 85% reduced risk of premenopausal breast cancer [relative risk (RR), 0.15; 95% confidence interval (95% CI), 0.03-0.85; P(trend) = 0.02]. In contrast, CSF1 levels in the highest quartile conferred a 33% increased risk of postmenopausal breast cancer (RR, 1.33; 95% CI, 0.96-1.86; P(trend) = 0.11), with greatest risk for invasive (RR, 1.45; 95% CI, 1.02-2.07; P(trend) = 0.06) and ER+/PR+ tumors (RR, 1.72; 95% CI, 1.11-2.66; P(trend) = 0.04). Thus, the association of circulating CSF1 levels and breast cancer varies by menopausal status.

Colon cancer cell-derived tumor necrosis factor-alpha mediates the tumor growth-promoting response in macrophages by up-regulating the colony-stimulating factor-1 pathway

The interplay between malignant and stromal cells is essential in tumorigenesis. We have previously shown that colony-stimulating factor (CSF)-1, matrix metalloprotease (MMP)-2, and vascular endothelial growth factor (VEGF)-A production by stromal cells is enhanced by CSF-1-negative SW620 colon cancer cells. In the present study, the mechanisms by which colon cancer cells up-regulate host factors to promote tumorigenesis were investigated. Profiling of tumor cell cytokine expression in SW620 tumor xenografts in nude mice showed increased human tumor necrosis factor (TNF)-alpha mRNA expression with tumor growth. Incubation of macrophages with small interfering (si) RNAs directed against TNF-alpha or TNF-alpha-depleted SW620 cell conditioned medium versus SW620 cell conditioned medium failed to support mouse macrophage proliferation, migration, and expression of CSF-1, VEGF-A, and MMP-2 mRNAs. Consistent with these results, human TNF-alpha gene silencing decreased mouse macrophage TNF-alpha, CSF-1, MMP-2, and VEGF-A mRNA expression in macrophages cocultured with human cancer cells. In addition, inhibition of human TNF-alpha or mouse CSF-1 expression by siRNA reduced tumor growth in SW620 tumor xenografts in mice. These results suggest that colon cancer cell-derived TNF-alpha stimulates TNF-alpha and CSF-1 production by macrophages, and that CSF-1, in turn, induces macrophage VEGF-A and MMP-2 in an autocrine manner. Thus, interrupting tumor cell-macrophage communication by targeting TNF-alpha may provide an alternative therapeutic approach for the treatment of colon cancer.

Colony-stimulating factor-1 antibody reverses chemoresistance in human MCF-7 breast cancer xenografts

Overexpression of colony-stimulating factor-1 (CSF-1) and its receptor in breast cancer is correlated with poor prognosis. Based on the hypothesis that blockade of CSF-1 would be beneficial in breast cancer treatment, we developed a murinized, polyethylene glycol-linked antigen-binding fragment (Fab) against mouse (host) CSF-1 (anti-CSF-1 Fab). Mice bearing human, chemoresistant MCF-7 breast cancer xenografts were treated with combination chemotherapy (CMF: cyclophosphamide, methotrexate, 5-fluorouracil; cycled twice i.p.), anti-CSF-1 Fab (i.p., cycled every 3 days for 14 days), combined CMF and anti-CSF-1 Fab, or with Ringer's solution as a control. Anti-CSF-1 Fab alone suppressed tissue CSF-1 and retarded tumor growth by 40%. Importantly, in combination with CMF, anti-CSF-1 Fab reversed chemoresistance of MCF-7 xenografts, suppressing tumor development by 56%, down-regulating expression of the chemoresistance genes breast cancer-related protein, multidrug resistance gene 1, and glucosylceramide synthase, and prolonging survival significantly. Combined treatment also reduced angiogenesis and macrophage recruitment and down-regulated tumor matrix metalloproteinase-2 (MMP-2) and MMP-12 expression. These studies support the paradigm of CSF-1 blockade in the treatment of solid tumors and show that anti-CSF-1 antibodies are potential therapeutic agents for the treatment of mammary cancer.

Regeneration of the rat neonatal intestine in transplantation

OBJECTIVE

Based on development of stem cell technology, newborn tissue, even undergoing cryopreservation, possesses promising potential as a donor source in the field of organ transplantation. However, the precise regeneration processes remains unclear. This study was designed to investigate the regenerative potential of newborn intestine with or without cryopreservation in the transplantation.

METHODS

Newborn rat intestines with or without cryopreservation were transplanted subcutaneously into the syngeneic host, and specimens were evaluated by histology, multiple immunostaining, and comprehensive gene expression analysis.

RESULTS

We determined that newborn rat intestine possessed regenerative potential in the syngeneic host even after cryopreservation, where angiogenesis was induced early in the submucosa with subsequent maturation in the crypts. Furthermore, newborn intestinal graft could facilitate the survival of maturation-incompetent 10-day-old graft that lacked regenerating activity (P < 0.01, n = 13). Tissue aggregates from the maturation-incompetent graft underwent reconstitution of their histologic configuration in the presence of newborn intestinal aggregates. Comprehensive gene expression analysis showed that 37 genes were preferentially up-regulated, while 19 genes were down-regulated in the regenerating 10-day-old graft (supported by the newborn graft).

CONCLUSIONS

Regeneration of newborn intestine is implicated in neo-angiogenesis in the host, and the newborn intestinal graft is capable of mediating the survival of the maturation-incompetent 10-day-old graft. Notwithstanding ethical and legal limitations in the clinic, these results may provide new insights into the regenerative role of newborn grafts.

beta-Catenin expression during vascular development and degeneration of avian mesonephros

beta-Catenin is a structural component of adherens junctions, a regulator of the Wnt signalling pathway and a transcriptional co-activator with a key role in vascular patterning. The avian mesonephros is a transitory embryonic kidney that is used in the study of vascular development and degeneration. Here we examine beta-catenin expression in this model during vascular development and degeneration. Quail embryos with developing or degenerating mesonephros were studied, on day 6 (30HH) or day 11 of incubation (40HH), respectively. QH1 whole mounts of developing mesonephros revealed numerous angioblast-like cells situated in the paramesonephric duct that seem to invade the mesonephros. Although these cells did not express beta-catenin, the surrounding periductal mesenchymal cells translocated high levels of beta-catenin into the nucleus. In contrast, degenerating mesonephros were devoid of angioblast-like cells and beta-catenin was lower than in the developing mesonephros. beta-Catenin was significantly reduced in the glomerular capillary tuffs, indicating that it was particularly down-regulated in the vascular system. No sex-related differences in beta-catenin expression were observed in degenerating mesonephros. Furthermore, two special populations of glomerular and peritubular endothelial cells were observed in degenerating mesonephros: one translocating beta-catenin into the nucleus and the other in apoptosis that did not translocate it. In conclusion, our results indicate that the paramesonephric duct is a potential new vasculogenetic pathway, and suggest that beta-catenin plays a role in the fate of mesonephric endothelial cells.

Colony-stimulating factor-1 blockade by antisense oligonucleotides and small interfering RNAs suppresses growth of human mammary tumor xenografts in mice

Colony-stimulating factor (CSF)-1 is the primary regulator of tissue macrophage production. CSF-1 expression is correlated with poor prognosis in breast cancer and is believed to enhance mammary tumor progression and metastasis through the recruitment and regulation of tumor-associated macrophages. Macrophages produce matrix metalloproteases (MMPs) and vascular endothelial growth factor, which are crucial for tumor invasion and angiogenesis. Given the important role of CSF-1, we hypothesized that blockade of CSF-1 or the CSF-1 receptor (the product of the c-fms proto-oncogene) would suppress macrophage infiltration and mammary tumor growth. Human MCF-7 mammary carcinoma cell xenografts in mice were treated with either mouse CSF-1 antisense oligonucleotide for 2 weeks or five intratumoral injections of either CSF-1 small interfering RNAs or c-fms small interfering RNAs. These treatments suppressed mammary tumor growth by 50%, 45%, and 40%, respectively, and selectively down-regulated target protein expression in tumor lysates. Host macrophage infiltration; host MMP-12, MMP-2, and vascular endothelial growth factor A expression; and endothelial cell proliferation within tumors of treated mice were decreased compared with tumors in control mice. In addition, mouse survival significantly increased after CSF-1 blockade. These studies demonstrate that CSF-1 and CSF-1 receptor are potential therapeutic targets for the treatment of mammary cancer.

The osteopetrotic mutation toothless (tl) is a loss-of-function frameshift mutation in the rat Csf1 gene: Evidence of a crucial role for CSF-1 in osteoclastogenesis and endochondral ossification

The toothless (tl) mutation in the rat is a naturally occurring, autosomal recessive mutation resulting in a profound deficiency of bone-resorbing osteoclasts and peritoneal macrophages. The failure to resorb bone produces severe, unrelenting osteopetrosis, with a highly sclerotic skeleton, lack of marrow spaces, failure of tooth eruption, and other pathologies. Injections of CSF-1 improve some, but not all, of these. In this report we have used polymorphism mapping, sequencing, and expression studies to identify the genetic lesion in the tl rat. We found a 10-base insertion near the beginning of the open reading of the Csf1 gene that yields a truncated, nonfunctional protein and an early stop codon, thus rendering the tl rat CSF-1(null). All mutants were homozygous for the mutation and all carriers were heterozygous. No CSF-1 transcripts were identified in rat mRNA that would avoid the mutation via alternative splicing. The biology and actions of CSF-1 have been elucidated by many studies that use another naturally occurring mutation, the op mouse, in which a single base insertion also disrupts the reading frame. The op mouse has milder osteoclastopenia and osteopetrosis than the tl rat and recovers spontaneously over the first few months of life. Thus, the tl rat provides a second model in which the functions of CSF-1 can be studied. Understanding the similarities and differences in the phenotypes of these two models will be important to advancing our knowledge of the many actions of CSF-1.

Procollagen-derived biomarkers in malignant ascites of ovarian cancer. Independent prognosticators for progression-free interval and survival

OBJECTIVE

Matrix formation is a hallmark of solid tumor biology. Circulating antigens of structural matrix proteins should reflect this fact, yet are subject to systemic variables. We propose that if measured regionally, in a cancer-induced extravascular fluid pool such as malignant ascites of ovarian cancer, the same antigens retain their conceptual advantage as surrogate markers for tumor biology.

METHODS

In malignant ascites obtained at staging laparatomy of 35 women with ovarian cancer, the protein-normalized levels of the C-terminal propeptide of procollagen type I (pnPICP) and the N-terminal propeptide of procollagen type III (pnPIIINP) were determined. Using univariate and multivariate analysis, we examined these parameters, their (pnPIIINP/pnPICP) quotient, and clinical criteria (FIGO stage, age, residual tumor, histology, and tumor grade) for impact on progression-free interval and survival.

RESULTS

The absolute level of pnPIIINP was the single most powerful independent factor impacting on survival, its P value being distinctly below (P = 0.0005 vs 0.003) and its risk ratio distinctly above (15 vs 2.5) residual tumor after debulking surgery. The relative level of pnPIIINP, i.e. (pnPIIINP / pnPICP), impacted on the likelihood of recurrence even more than residual tumor. By Kaplan-Meier analysis, cutoff values for the absolute or relative pnPIIINP level significantly discriminated patients with shortened survival or progression-free interval, respectively.

CONCLUSIONS

Since malignant ovarian epithelium itself forms collagen type III, and since collagen type III is a solid-phase regulator of angiogenesis, we propose that ascitic pnPIIINP is a fluid-phase indicator for angiogenic activity in ovarian cancer and thus represents a tumor virulence index.

Gene expression of colony-stimulating factors and stem cell factor after myocardial infarction in the mouse

Recent studies have suggested that cytokines such as macrophage colony-stimulating factor (M-CSF) might be involved in the pathogenesis of ischaemic heart disease. Macrophage colony-stimulating factor, granulocyte-colony stimulating factor (G-CSF), granulocyte-macrophage-colony stimulating factor (GM-CSF), stem cell factor (SCF), interleukin-3 (IL-3) and interleukin-7 (IL-7) are potent cytokines belonging to the same structual class that may affect function, growth and apoptosis both in the heart and other organs. The aims of the present study were to characterize a post-infarction model in the mouse and to examine mRNA expression of M-CSF, GM-CSF, SCF, IL-3 and IL-7 during the development of heart failure. Myocardial infarction (MI) was induced in mice by ligation of the left coronary artery. Average infarct size was 40% and the mice developed myocardial hypertrophy and pulmonary oedema. Ribonuclease (RNAase) protection assays showed abundant cardiac expression of M-CSF and SCF. After MI, we measured down-regulation of cytokine mRNA expression in the heart (M-CSF, SCF), lung (M-CSF), liver (M-CSF) and spleen (M-CSF) compared with sham. Cardiac G-CSF, GM-CSF and IL-7 mRNAs were not detected. In conclusion, abundant cardiac gene expression of M-CSF and SCF was found. In our mouse model of MI, M-CSF and SCF were down-regulated in the heart and several other organs suggesting specific roles for these cytokines during development of ischaemic heart failure.

Dissociation of angiogenesis and osteoclastogenesis during endochondral bone formation in neonatal mice

Invasion of the mineralized matrix by endothelial cells and osteoclasts is a key event in endochondral bone formation. To examine the putative role of osteoclast activity in the angiogenic process, we used two in vivo models of suppressed bone resorption: mice treated with the bisphosphonate clodronate and in osteoclast-deficient, osteopetrotic mice. Angiogenesis was assessed in caudal vertebrae of these neonatal mice. This model enables us to study the interaction between osteoclasts and endothelial cells during endochondral bone formation. In control conditions, sinusoid-like structures were detected in the vicinity of tartrate resistance acid phosphatase positive (TRAcP+) osteoclasts. Treatment with clodronate completely abolished osteoclastic bone resorption, whereas angiogenesis remained unaffected. In line with these observations, in the osteopetrotic mouse mutants c-fos knockout mice and op/op mice, capillaries invaded the calcified cartilage in the absence of osteoclasts. In conclusion, our data strongly suggest that during endochondral bone formation, vascular invasion can occur in the absence of osteo(chondro)clastic resorption. In addition, bisphosphonates show no apparent effect on angiogenesis in this in vivo model. These findings may have important clinical implications in the management of skeletal disorders such as metastatic bone disease, in which both osteoclastic bone resorption and angiogenesis contribute to tumor growth. On the other hand, our results confirm that bisphosphonates can be used safely in the treatment of disorders that affect the growing skeleton, such as in juvenile osteoporosis.

Macrophage colony stimulating factor modulates the development of hematopoiesis by stimulating the differentiation of endothelial cells in the AGM region

Definitive hematopoietic stem cells arise in the aorta-gonad-mesonephros (AGM) region from hemangioblasts, common precursors for hematopoietic and endothelial cells. Previously, we showed that multipotential hematopoietic progenitors and endothelial cells were massively produced in primary culture of the AGM region in the presence of oncostatin M. Here we describe a role for macrophage-colony-stimulating factor (M-CSF) in the development of hematopoietic and endothelial cells in AGM culture. The number of hematopoietic progenitors including multipotential cells was significantly increased in the AGM culture of op/op embryos. The addition of M-CSF to op/op AGM culture decreased colony-forming unit (CFU)-GEMM, granulocyte macrophage-CFU, and erythroid-CFU, but it increased CFU-M. On the other hand, the number of cells expressing endothelial markers, vascular endothelial-cadherin, intercellular adhesion molecule 2, and Flk-1 was reduced in op/op AGM culture. The M-CSF receptor was expressed in PCLP1(+)CD45(-) cells, the precursors of endothelial cells, and M-CSF up-regulated the expression of more mature endothelial cell markers-VCAM-1, PECAM-1, and E-selectin-in PCLP1(+)CD45(-) cells. These results suggest that M-CSF modulates the development of hematopoiesis by stimulating the differentiation of PCLP-1(+)CD45(-) cells to endothelial cells in the AGM region.

Vascular endothelial growth factor is expressed in human fetal growth cartilage

Angiogenesis is a crucial event in endochondral ossification. Chemoattractants and mitogens for endothelial cells (such as basic fibroblast growth factor [bFGF] and transforming growth factor beta [TGF-beta]), which act as local regulators of the process, are synthesized by chondrocytes under several stimuli and in relation to the differentiation stage of the cartilage. Vascular endothelial growth factor (VEGF) is a 44-kDa protein well known as a potent angiogenic molecule owing to its mitogenic and permeability-causing properties. In this work, VEGF was located by immunohistochemistry in growth plate cartilage of human fetuses (20-22 weeks old) and its expression was demonstrated by reverse-transcription polymerase chain reaction (RT-PCR). Primary culture of human fetal epiphyseal chondrocytes (HFEC) maintained VEGF expression at protein and messenger RNA (mRNA) levels and this expression was stimulated by cartilage-promoting growth factors incorporated into the culture media (rFGF-b, rTGF-beta1, and insulin-like growth factor [rFGF-b] at 50 ng/ml). The conditioned medium (CM) of HFEC stimulated the proliferation of endothelial cells, and this was partially blocked by anti-VEGF antibody. These studies showed VEGF production by chondrocytes of the epiphyseal growth cartilage and suggested a role of this factor in cartilage physiology and the angiogenic process.

Facial development and type III collagen RNA expression: concurrent repression in the osteopetrotic (Toothless,tl) rat and rescue after treatment with colony-stimulating factor-1

The toothless (osteopetrotic) mutation in the rat is characterized by retarded development of the anterior facial skeleton. Growth of the anterior face in rats occurs at the premaxillary-maxillary suture (PMMS). To identify potential mechanisms for stunted facial growth in this mutation we compared the temporospatial expression of collagen I (Col I) and collagen III (Col III) RNA around this suture in toothless (tl) rats and normal littermates by in situ hybridization of specific riboprobes in sagittal sections of the head. In normal rats, the suture is S shaped at birth and becomes highly convoluted by 10 days with cells in the center (fibroblasts and osteoblast progenitors) expressing Col III RNA and those at the periphery (osteoblasts) expressing no Col III RNA but high amounts of Col I RNA throughout the growth phase (the first 2 postnatal weeks). In the mutant PMMS, cells were reduced in number, less differentiated, and fewer osteoblasts were encountered. Expression of Col I RNA was at normal levels, but centrosutural cells expressed Col III RNA only after day 6 and then only weakly. A highly convoluted sutural shape was never achieved in mutants during the first 2 postnatal weeks. Treatment of tl rats with the cytokine CSF-1 improved facial growth and restored cellular diversity and Col III RNA expression in the PMMS to normal levels. Taken together, these data suggest that normal facial growth in rats is related to expression of Col III RNAby osteoblast precursors in the PMMS, that these cells are deficient in the tl mutation and are rescued following treatment with CSF-1.

Auditory ossicle abnormalities and hearing loss in the toothless (osteopetrotic) mutation in the rat and their improvement after treatment with colony-stimulating factor-1

Osteopetrosis describes a group of skeletal metabolic diseases of heterogeneous etiology and varied severity that produces a generalized accumulation of skeletal mass, the result of reduced bone resorption. Inherited in a variety of species including humans, the most severe forms are lethal. Among common features are progressive blindness and deafness of controversial etiologies for which there are no universally effective treatments. We have studied the auditory responsiveness and auditory ossicle quantitative histomorphology and temporal bone vasculature in the toothless (tl) rat, a lethal osteopetrotic mutation with few osteoclasts, very low bone turnover, and limited angiogenesis in the axial skeleton. Compared with normal littermates, 3-week-old mutants showed significantly reduced auditory responsiveness, a hearing loss due to abnormalities in both form and tissue composition of the stapes, and little capillary sprouting in the vascular bed of the temporal bone. Treatment of mutants with colony-stimulating factor 1 (CSF-1), known to greatly reduce sclerosis in the axial skeleton, significantly improved hearing, stapedial form and tissue composition, and angiogenesis in the temporal bone. In normal rats, the stapes consisted of 89.3% bone, 9.1% mineralized cartilage, and 0.8% porosity. In osteopetrotic rats, the stapes consisted of 48.3% bone, 35.9% mineralized cartilage, and 15.9% porosity, while after CSF-1 treatment, the bone content increased to 55.2%, cartilage was decreased to 21.7%, and porosity increased to 23.0%, respectively. This is the first demonstration of an auditory abnormality in an osteopetrotic animal mutation and shows that the hearing loss in tl rats can be significantly improved following treatment with CSF-1.

Insulin-like growth factor-I (IGF-I) and IGF-I receptor (IGF-IR) immunoreactivity in normal and osteopetrotic (toothless, tl/tl) rat tibia

Insulin-like growth factor-I (IGF-I) plays a major role in regulating cell growth. This study examined the immunohistochemical distribution of IGF-I and IGF-I receptor (IGF-IR) in tibias from normal and osteopetrotic (toothless, tl/tl) rats, following treatment with colony stimulating factor-1 (CSF-1). In normal rats, immunoreactivity for IGF-I and IGF-IR was detected in cells of the articular and epiphyseal cartilage, secondary ossification centres, zones of resting and proliferating chondrocytes and bone marrow. Bone marrow cells immunoreactive for IGF-I and IGF-IR were significantly reduced in the tl/tl rat (p < 0.001) compared with normal animals. Treatment of tl/tl rats with CSF-1 increased immunoreactivity for IGF-I and IGF-IR in bone marrow cells as well as the number of TRAP positive osteoclasts. This increase was the result of recruitment of a range of hematopoietic cell types, including eosinophils, polymorphs and a substantial number of monocyte-like cells demonstrating strong immunoreactivity to IGF-I/IGF-IR. The differences in relative immunoreactivity for IGF-I/IGF-IR by bone marrow cells in untreated and CSF-1-treated tl/tl rats indicate a CSF-1-dependent recruitment of cells bearing surface IGF-IRs which may be mediated by an increase in local or systemic IGF-I.

The lack of genital ridge vascularization in the early chick embryo: implications in the migration of the primordial germ cells

It is known that chick primordial germ cells (PGCs) in early embryonic development migrate via the blood vascular system to colonize the gonadal anlagen. Classically, two factors have been involved in the extravasation of PGCs from the blood stream: chemotactic and mechanical factors. An accurate knowledge of the vascular system of the genital ridge is therefore necessary. However, development of gonadal vascularization in bird embryos has been scarcely studied. Our previous studies have shown that the gonadal arteries develop from the mesonephric arteries. The purpose of this work was to study the implications of the development of the vascular system of the chick genital ridge on PGCs colonization. We selected the Hamburger and Hamilton (H-H) stage 18, since the genital ridge is well developed and PGCs actively extravasate. Forty chick embryos of this stage were processed for scanning electron microscopy of vascular corrosion casts and of critical point-dried specimens as well as light microscopy. Our results are conclusive. We could not find any vessel or capillary network supplying the genital ridge; the dorsal aorta and the primordia of the mesonephric arteries were the closest vessels. However, numerous interendothelial spaces were found in the dorsal aorta at the level of the genital ridge. It is suggested that the interendothelial gaps may be very important in the exchange of substances between the avascular genital ridge and the aortic endothelium at this developmental stage. Two different routes are thought to be involved in PGC migration to the gonadal anlage at this stage: the aortic endothelium and the mesonephric arteries. Whereas mechanical factors may be important for extravasation of PGCs in the mesonephric arteries, no reasons have been found from the morphological point of view to support a slowness of the blood flow in the dorsal aorta at the level of the genital ridge facilitating the extravasation.

Role of the subchondral vascular system in endochondral ossification: endothelial cells specifically derepress late differentiation in resting chondrocytes in vitro

Endochondral ossification in growth plates proceeds through several consecutive steps of late cartilage differentiation leading to chondrocyte hypertrophy, vascular invasion, and, eventually, to replacement of the tissue by bone. It is well established that the subchondral vascular system is pivotal in the regulation of this process. Cells of subchondral blood vessels act as a source of vascular invasion and, in addition, release factors influencing growth and differentiation of chondrocytes in the avascular growth plate. To elucidate the paracrine contribution of endothelial cells we studied the hypertrophic development of resting chondrocytes from the caudal third of chick embryo sterna in co-culture with endothelial cells. The design of the experiments prevented cell-to-cell contact but allowed paracrine communication between endothelial cells and chondrocytes. Under these conditions, chondrocytes rapidly became hypertrophied in vitro and expressed the stage-specific markers collagen X and alkaline phosphatase. This development also required signaling by thyroid hormone in synergy. Conditioned media could replace the endothelial cells, indicating that diffusible factors mediated this process. By contrast, smooth muscle cells, fibroblasts, or hypertrophic chondrocytes did not secrete this activity, suggesting that the factors were specific for endothelial cells. We conclude that endochondral ossification is under the control of a mutual communication between chondrocytes and endothelial cells. A finely tuned balance between chondrocyte-derived signals repressing cartilage maturation and endothelial signals promoting late differentiation of chondrocytes is essential for normal endochondral ossification during development, growth, and repair of bone. A dysregulation of this balance in permanent joint cartilage also may be responsible for the initiation of pathological cartilage degeneration in joint diseases.

Lingual papillae of the growing rat as a model of vasculogenesis

BACKGROUND

Capillary sprouting is an important mechanism that initiates neovascularization. Because observation of capillary sprouting and its morphological staging can be problematic, we sought to establish a simple model of capillary growth.

METHODS

Rats were obtained at gestational days 15, 16, and 20, at birth, and at postnatal day 10. Scanning electron microscopy (SEM) of vascular casts, freeze-fractured and epithelium-exfoliated specimens, as well as transmission electron microscopy (TEM) of tissue sections were used.

RESULTS

In day 15 fetuses, the filiform papillae and their connective tissue cores had not been formed, but a simple capillary network without regional differences was present. In day 16 fetuses, mesenchymal cells started to form papillary connective tissue cores, and, inside the epithelium, ridges were found. Capillary sprouts arose from the preexisting sinusoidal capillaries by elongation and widening, invaded into connective tissue cores in day 20 fetuses, and gradually bifurcated to form capillary loops in the prospective giant conical papillae of the newborn rat. In postnatal day 10 rats, the capillary network beneath the papillae became bilayered.

CONCLUSION

Vascular formation in the lingual papillae in growing rats offers an easy model for the observation of capillary sprouting. In this model, the sprouts arise from preexisting sinusoidal capillaries and not from veins, as usually observed in other models. The mechanism of capillary growth is the elongation of (preexisting) sinusoidal capillaries into the developing connective tissue cores and toward the forming epithelial ridges.

Abnormalities in bone cell function and endochondral ossification in the osteopetrotic toothless rat

The toothless (tl) rat is an osteopetrotic mutation whose excess skeletal mass is produced by a defect in its skeletal microenvironment. Its skeletal sclerosis fails to be cured by bone marrow transplantation but is largely reversed by exogenous administration of colony stimulating factor 1 which increases osteoclast neogenesis and resorptive activity. Recent studies have also indicated abnormalities in growth plate cartilage morphology and in osteoblast number and function in the tl rat. The present histomorphometric study examined static and kinetic parameters of bone cell and cartilage function in young (3-5-week-old) animals of tl stock for evidence of tissue level dysfunction. Mineralization of growth plate cartilage in mutants occurred only in the lateral regions of the growth plate, not in the central region, and longitudinal bone growth was significantly reduced (36%-61%) in mutants at the ages examined. Bone volume and trabecular thickness were greater in mutants despite significant reductions in their osteoblast populations and bone formation rates (two to threefold lower). Mutants also showed progressive age- and metaphyseal site-related decreases in osteoblast numbers which, compared to normal littermates, may relate to differences in osteoprogenitor cell pools, osteoblast lifespan, or resorption-derived skeletal growth factors locally available to support and maintain normal osteoblast phenotype. Osteoclast number per millimeter bone perimeter was reduced 96-fold in mutants and showed no age- or metaphyseal site-related changes. This study presents evidence in support of defects in chondrocyte and bone cell function in the tl rat and reveals the specific tissue locations where they occur.

Decreased growth hormone receptor expression in long bones from toothless (osteopetrotic) rats and restoration by treatment with colony-stimulating factor-1

Growth hormone (GH) is known to regulate growth and development of skeletal tissues. This study examined the distribution of growth hormone receptor (GHR) expression in tibias from normal and osteopetrotic tl/tl rats. For normal 2 week-old rats, GHR expression was detected immunocytochemically in cells of the articular and epiphyseal cartilage, primary and secondary ossification centres, zone of resting cartilage and bone marrow. Within the marrow, GHR immunopositive cells were concentrated in the central cone and largely excluded from the zone of immature progenitors at the periphery. For the marrow haemopoietic compartment, GHR expression was almost restricted to the nucleus in large mononuclear cells, adipocytes and megakaryocytes. A population of small lymphocytelike cells in the marrow periphery expressed GHR on the plasma membrane. GHR was not detected in mature erythroid cells, macrophages, granulocytes, or osteoclasts. The expression of GHR was significantly reduced in bone marrow cells of the tl/tl rat (p < 0.001) compared with normal animals. Injection of recombinant CSF-1 into tl/tl rats every 48 hours for 2 weeks from birth restored GHR-positive cells to the central core of the marrow space. The most striking change was the appearance of substantial numbers of mononuclear cells expressing abundant GHR on the cell surface. We infer that these cells are a novel subset of CSF-1 responsive cells involved in bone resorption. The differences in relative expression of GHR by bone marrow cells in untreated and CSF-1-treated tl/tl rats suggests a CSF-1-dependent recruitment of cells bearing surface GHRs.