S. Sakuma

Participation of Different Macrophage Populations and Myofibroblastic Cells in Chronically Developed Renal Interstitial Fibrosis after Cisplatin-induced Renal Injury in Rats

To shed some light on the mechanisms behind renal fibrogenesis, the present study immunohistochemically investigated the participation of different macrophage populations and myofibroblastic cells in rat renal interstitial fibrosis developed chronically after repeated injection of cisplatin (2 mg/kg body weight, once weekly for 7 weeks). During the 19-week recovery period after the final injection, fibrotic lesions progressively developed in the corticomedullary junction, with the greatest level at post-final injection (FPI) week 5, and then the lesions were gradually repaired by PFI week 19, indicative of a healing process. In conformity with the development of fibrotic lesions, the number of myofibroblastic cells reacting with an anti-α-smooth muscle actin antibody was increased, with a peak at PFI week 3, and collagens (types I, III, and IV), fibronection, and laminin were excessively accumulated in these areas. Interstitial cells forming the fibrotic lesions showed mitotic activity at the early stages, whereas they disappeared by apoptosis in the healing process. A large number of cells reacting with an antibody of ED1 (for exudate macrophages), ED2 (for resident macrophages), or OX6 (for major histocompatibility complex class II-presenting macrophages and interstitial dendritic cells) had already appeared at PF1 week 1, and then their numbers increased, with a peak at PFI weeks 7, 3, and 9 in ED1-, ED2-, and OX6-positive cells, respectively. Thereafter, the number of ED1- and ED2-positive cells decreased, whereas the number of OX6-positive cells persisted at a high level until PFI week 19. In the healing process, clusters of lymphocytes were present, the development of which might have been related to OX6-positive cells. The present study demonstrated that chronically developing rat renal interstitial fibrosis might be produced by the complicated mechanisms evoked by interactions between different macrophage populations and myofibroblastic cells, because macrophages show heterogeneous functions depending on microenvironmental factors.

In vivo responses of macrophages and myofibroblasts in the healing following isoproterenol-induced myocardial injury in rats

To clarify the relation between macrophage and myofibroblast involvement in various myocardial diseases, the authors investigated the kinetics of these cells in the healing (scar tissue formation) following isoproterenol-induced myocardial injury in rats. Alphasmooth muscle actin (α-SMA) expressing myofibroblasts were seen at the border of the affected area and appeared in the greatest numbers on days 3–7 post-injection, followed by a gradual decrease by day 35. The peak on day 3 was consistent with the timing of the highest proliferative activity of myofibroblasts. The number of ED1-positive macrophages began to increase as early as day 1, reaching a peak on day 3 within the injured myocardium. The expansion of EDI-positive macrophages preceded an increased number of α-SMA-positive myofibroblasts suggesting that myofibroblast proliferation and activation may be mediated by factors released by ED1-positive mcrophages in response to myocardial injury. The number of ED2-positive tissue-fixed, resident macrophages gradually increased from day 3 post-injection, and peaked on day 14, but the number of ED2-positive macrophages was consistently fewer than that of ED1-positive macrophages during the 35 day-observation period after the injection. The labelling index of the ED2-positive cells was maximal on day 14, indicative of local proliferation of resident macrophages. In the healing process after myocardial injury, EDI-positive macrophages increase markedly in the early stages; ED2-positive macrophages appear later.

MACROPHAGES, MYOFIBROBLASTS, AND EXTRACELLULAR MATRIX ACCUMULATION IN INTERSTITIAL FIBROSIS OF CHRONIC PROGRESSIVE NEPHROPATHY IN AGED RATS

Progressive renal fibrosis is considered to be the final common pathway leading to chronic renal failure. Macrophages are thought to play a role in the induction of the myofibroblasts that produce extracellular matrix (ECM) proteins in renal interstitial fibrosis. We immunohistochemically investigated the relationship between infiltrating macrophages and myofibroblast development in chronic progressive nephropathy (CPN) in 24 month-old male F344 rats, and we also analyzed components of ECM proteins using immunofluorescence microscopy. According to histomorphologic criteria for severity, described elsewhere, rats with CPN were divided into grade 1 (n = 20), grade 2 (n = 34), grade 3 (n = 10), and grade 4 (n = 6). The ratio of fibrotic tissues per unit area, determined by morphometric analysis, was increased with advancing grade of nephropathy. The number of interstitial macrophages continued to be increased gradually, with a peak in grade 4. α-smooth muscle actin-positive myofibroblasts developed, surrounding the regenerating renal tubules in conjunction with the fibrotic areas. The number of the myofibroblasts was also increased, with a peak in grade 3, but in grade 4, it was slightly decreased. There was a significant relationship between the number of infiltrating macrophages and the degree of interstitial fibrosis (r = 0.802; P < 0.05). These observations suggest that macrophages and myofibroblasts might be key cells in fibrogenesis in CPN. However, there was no significant correlation between the numbers of macrophages and myofibroblasts (r = 0.198; P>0.05), although a significant relation between these cells has been reported in the early stages of experimental rat renal fibrosis. Immunostaining for collagen type IV demonstrated increased expression in thickened tubular basement membranes. Abnormal depositions of collagen types I and III, fibronectin, and tenascin were also observed in fibrotic areas adjacent to dilated or atrophic tubules with thickened basement membranes. These ECM proteins were increased in conjunction with the grade of nephropathy, suggesting that ECM accumulation might contribute to progression of renal interstitial fibrosis.

Relationship between vimentin expressing renal tubules and interstitial fibrosis in chronic progressive nephropathy in aged rats

Abstract We investigated the relationship between regenerating renal tubular epithelial cells and myofibroblast development in chronic progressive nephropathy (CPN) of aged male F344 rats. We used established criteria to classify disease in rats with CPN as grade 1 (n=9), grade 2 (n=10), grade 3 (n=7) and grade 4 (n=4). Five young rats served as controls (grade 0). The ratio of fibrotic tissues per unit area, assessed in collagen type III-immunostained sections by morphometric analysis, increased significantly with advancing grade of CPN. Vimentin-expressing, regenerating renal tubules were found from grade 1 and continued to increase in number up to grade 3, decreasing slightly, however, in grade 4. Similar kinetics were seen for the number of α-smooth muscle actin-positive myofibroblasts, and there was a significant correlation between the number of regenerating renal tubules and myofibroblast development (correlation coefficient=0.83, P<0.01). The myofibroblasts developed in close association with the fibrotic areas seen in grades 1–4; the cells also reacted to desmin or vimentin, indicating the activated state. Immunohistochemistry for platelet-derived growth factor (PDGF)-BB and transforming growth factor (TGF)-β revealed that vimentin-positive renal tubules were positive for PDGF-BB, but negative for TGF-β, and that interstitial reactive cells showed no positive reactions for both factors. The present studies on rat CPN showed that regenerating renal tubules may be a major source of a fibrogenic growth factor, PDGF-BB, and that the PDGF-BB might induce the development of fibrogenic cells, myofibroblasts, culminating in progressive interstitial fibrosis.

Canine Peripheral Nerve Sheath Tumor with Eosinophilic Cytoplasmic Globules

A 13-year-old male Shetland Sheepdog had a subcutaneous tumor in the left brachium. The tumor was removed and recurred several times at 5, 13, 16, 22, and 31 months after the initial presentation. Histologically, the removed nodules from the fourth resection were composed of neoplastic proliferation of round to fusiform cells, which possessed eosinophilic globules in their cytoplasm. The globules were periodic acid–Schiff positive and diastase resistant. Positive reactions for acid phosphatase were observed in the cytoplasm of the tumor cells. Ultrastructurally, these globules consisted of membrane-bound, dense structures containing dense granules, lucent vacuoles, and homogeneous materials. The recurrent tumors removed at the fifth resection consisted of spindle cell proliferation arranged in interlacing fascicles with wavy nuclei and containing a small number of cells with cytoplasmic globules. The tumor cells were immunoreactive to vimentin, S-100 protein, myelin basic protein, and neuron-specific enolase. The tumor was diagnosed as a peripheral nerve sheath tumor with eosinophilic cytoplasmic globules. These findings are unique for the histogenesis of granular cell tumors.

Glial pathology in development of cerebellar dysplasia in the hereditary cerebellar vermis defect (CVD) rat

Abstract The cerebellar vermis defect (CVD) rat is a new neurological mutant characterized by a cerebellar vermis defect and dysplasia in the cerebellum, especially at the cerebellopontine junctions. In this study, the cytokinetics of glia in terms of the development of cerebellar dysplasia in the CVD rat was investigated using glial fibrillary acidic protein (GFAP) and vimentin immunohistochemistry. In the cerebellar hemispheres, dislocation of the Bergmann glia was observed from postnatal day 5 (P5) in lesions with abnormally aggregated external granule cells (EGCs). Rearranging Bergmann glia were often seen around the EGCs penetrating into the white matter. In the cerebellopontine junctional areas, Bergmann glia were induced after penetration of the Purkinje cells, identified with calbindin immunohistochemistry, and EGCs into the pons from P10. Bergmann fibers were frequently arranged perivascularly. In the clusters of Purkinje cells without EGC settlement in the pons, a small number of Bergmann fibers were observed and their alignment was completely disturbed. These findings suggest that morphological changes in the Bergmann glia depend on their contact with Purkinje cells, but that the orientation of their processes may be influenced by EGC settlement. These glial fibers in the CVD rat may play an important role in the aberrant migration of EGCs, resulting in the development of cerebellar dysplasia.

Chronological and immunohistochemical observations of cerebellar dysplasia and vermis defect in the hereditary cerebellar vermis defect (CVD) rat

Abstract Hereditary cerebellar vermis defect (CVD) rats, a new neurological mutant, developed both cerebellar vermis defect and cerebellar dysplasia. Developmental alterations in the cerebellum of the CVD rats were studied chronologically and immunohistochemically. The earliest architectural abnormality was a maldevelopment of the inferior cerebellar peduncle from embryonic day 17 (E17), leading to an indistinct separation between the cerebellum and the pons. From E19, the CVD rats lacked vermis development and, therefore, the cerebellar hemispheres were fused. After birth, Purkinje cells and external granule cells (EGCs) penetrated into the pontine tissue, but retained their normal position until postnatal day 10. Cerebellar lamination began to be disturbed due to abnormal perivascular aggregations of the EGCs, resulting in convoluted and occasionally perivascular lamination. There were no Bergmann glia in the heterotopic cerebellum of the pons, and abnormally arranged Bergmann glia were observed in the mildly disorganized cerebellar hemispheres. Immunohistochemistry for calbindin revealed that abnormal orientation of the Purkinje cells might be related to the perivascular EGCs. Parvalbumin-immunopositive microneurons were seen only in the disarranged molecular layers, and synaptophysin-immunopositive cerebellar glomeruli were present in the afflicted internal granular layers. These findings suggest that perivascular EGCs may play an important role in cerebellar dysplasia and the developmental plasticity in the altered cerebellogenesis.

Characterization of newly established tumor lines from a spontaneous malignant schwannoma in F344 rats: nerve growth factor production, growth inhibition by transforming growth factor-β1, and macrophage-like phenotype expression

Transplantable tumor (KE) and clone cell (KE-F11) lines were established from a spontaneous malignant schwannoma found in an aged F344 rat. The primary tumor and KE tumors consisted of oval or spindle cells arranged in ill-defined bundles. Cultured KE-F11 cells exhibited polygonal or spindle configurations. Immunohistochemically, neoplastic cells in KE and KE-F11 reacted to vimentin, S-100 protein, neuron-specific enolase, myelin basic protein, and glial fibrillary acidic protein in varying degrees, indicating neurogenic features; occasional cells reacted to α-smooth muscle actin. Cells positive for lysosomal enzymes (acid phosphatase and non-specific esterase), and ED1 (rat macrophage specific) were observed in KE-F11, and electron microscopically, cells with many lysosomes were frequently present, indicating expression of macrophage-like phenotypes. Bioassay analysis revealed that KE-F11 cells produced high levels of nerve growth factor. DNA synthesis was inhibited by addition of transforming growth factor-β1 (TGF-β1), and Northern blot analysis revealed that expression of c-myc, a cell cycle-related immediate early gene, was depressed by TGF-β1. Likely, TGF-β1 is a factor capable of inhibiting cellular growth of Schwann cells. mRNA expression of the low-density lipoprotein receptor-related protein (LRP) was seen in KE-F11 cells by Northern blot analysis, and the level was decreased by lipopolysaccharide (LPS) treatment. LRP may be attributable to regulation of Schwann cell functions. KE-F11 cells seeded on laminin-coated dishes exhibited more extended cytoplasmic projections than on collagen type I-coated dishes. The present study provides evidence that biological properties of malignant schwannoma-derived cells might be affected by exogenous factors such as TGF-β1, LPS and laminin. These tumor lines may be useful for studies on pathobiological characteristics of Schwann cells.

INFLUENCE OF PROGESTERONE AND OESTROGEN ON GROWTH AND MORPHOLOGY OF A TRANSPLANTABLE RAT UTERINE SMOOTH MUSCLE TUMOUR (SMT-Y)

Tumours of uterine smooth muscle are poorly understood neoplasms in which the effects of steroid sex hormones are complex. The influence of progesterone and oestrogen on a transplantable rat uterine smooth muscle tumour line (SMT-Y) was investigated. Female F344 rats given subcutaneous transplants of tumour fragments developed tumours, 1.5-2 cm in diameter, and were then treated with progesterone (10 mg/rat) or 17 beta-oestradiol (50 mg/rat). Tumours in treated groups were compared with those in untreated controls. During a 9-week observation period after treatment, progesterone promoted tumour growth from 4 weeks, with increased numbers of proliferating cells. In contrast, oestradiol inhibited tumour growth from 6 weeks; the degraded tumours, consisting mainly of vacuolated neoplastic cells, had decreased numbers of proliferating cells and increased numbers of apoptotic cells, demonstrable by in-situ terminal deoxyribonucleotide transferase (TdT)-mediated dUTP nick labelling. Immunohistochemically, tumours in control and progesterone groups were labelled positively for alpha-smooth muscle actin (SMA) and desmin but not for vimentin, whereas the degraded tumours in the oestradiol group had reduced reactivity for SMA and desmin but an increased reactivity for vimentin. These results indicate that progesterone may act as a promoter for uterine smooth muscle tumour growth by stimulating mitotic activity, whereas oestrogen may have suppressive effects on tumour growth, accompanied by morphological changes.

Analysis of aberrant neuronal migrations in the hereditary cerebellar vermis defect (CVD) rat using bromodeoxyuridine immunohistochemistry

Abstract The hereditary cerebellar vermis defect rat (CVD) is a new neurological mutant characterized by cerebellar vermis defect and a dysplastic cerebellum, especially in the cerebello-pontine junctions. In this study, the cytokinetics of neuronal migrations in the CVD were analyzed using 5-bromo-2′-deoxyuridine (BrdU) as a labeling marker. From embryonic day 21, the CVD cerebellum was small in size with retarded foliation, but no significant differences were detected in the migration pattern of the BrdU-labeled cells between the unaffected controls and the CVD during the prenatal period. On postnatal day 0 (P0), heterotopic Purkinje cells, demonstrable by calbindin immunohistochemistry, were seen in the dorsal pons of the CVD. From P4, BrdU-positive external granule cells (EGCs), which were labeled by BrdU injection on P2, began to penetrate the pons. From P5, the EGCs aggregated around the blood vessels, leading to a disturbance of the cerebellar lamination both in the cerebello-pontine junctions and in the cerebellar hemispheres. Thereafter, the BrdU-labeled cells in the perivascularly aggregated EGCs migrated radially, and formed internal granular layers around the vessels, indicating an aberrant perivascular migration of the EGCs. These findings suggest that the EGC dislocation was preceded by an aberrant settlement of the Purkinje cells, and that the perivascularly aggregated EGCs resulted in cerebellar dysplasia in the CVD.