Malignant astrocytoma with binucleated granular cells in a Sprague-Dawley rat

Targeting glioblastoma-derived pericytes improves chemotherapeutic outcome

Glioblastoma is the most common malignant brain cancer in adults, with poor prognosis. The blood-brain barrier limits the arrival of several promising anti-glioblastoma drugs, and restricts the design of efficient therapies. Recently, by using state-of-the-art technologies, including thymidine kinase targeting system in combination with glioblastoma xenograft mouse models, it was revealed that targeting glioblastoma-derived pericytes improves chemotherapy efficiency. Strikingly, ibrutinib treatment enhances chemotherapeutic effectiveness, by targeting pericytes, improving blood-brain barrier permeability, and prolonging survival. This study identifies glioblastoma-derived pericyte as a novel target in the brain tumor microenvironment during carcinogenesis. Here, we summarize and evaluate recent advances in the understanding of pericyte's role in the glioblastoma microenvironment.

Desmin expression profile in reactive astrocytes in the 3-nitropropionic acid-lesioned striatum of rat: Characterization and comparison with glial fibrillary acidic protein and nestin

Desmin, a muscle-specific, type-III intermediate-filament protein, is reportedly expressed in astrocytes in the central nervous system. These cells become reactive astrocytes in response to brain injuries. To elucidate whether desmin is involved in this process, we examined the spatiotemporal expression profiles of desmin and their relationship with two astroglial intermediate filaments, glial fibrillary acidic protein (GFAP) and nestin, in the striatum of rats treated with the mitochondrial toxin 3-nitropropionic acid (3-NP). Weak, constitutive immunoreactivity for desmin was observed in astrocytes generally, and in reactive astrocytes in the peri-lesional area, its expression increased in parallel with that of GFAP over 3 d post-lesion and was maintained until at least day 28. Desmin, GFAP, and nestin showed characteristic time-dependent expression patterns in reactive astrocytes forming the astroglial scar; delayed and long-lasting induction of desmin and GFAP, and rapid but transient induction of nestin. In the lesion core, desmin was expressed in two categories of perivascular cells: nestin-negative and nestin-positive. These findings show that desmin, together with GFAP and nestin, is a dynamic component of intermediate filaments in activated astroglia, which may account for the dynamic structural changes seen in these cells in response to brain injuries.

Availability of a microglia and macrophage marker, iba-1, for differential diagnosis of spontaneous malignant reticuloses from astrocytomas in rats

In rats, it is sometimes difficult to distinguish malignant reticuloses from astrocytomas in routine histopathological assessment. In the present study, four spontaneous brain neoplasms developing in the cerebrum of one Wistar Hannover rat and three Sprague-Dawley rats were immunohistochemically examined using microglia and macrophage markers. Histopathologically, these neoplasms were localized mainly in the cerebral cortex, hypothalamus or piriform lobe, and the portions showing solid growth did not show characteristic cellular arrangement but had an indistinct boundary with the surrounding brain parenchyma. Neoplastic cells had oval or pleomorphic small nuclei with abundant eosinophilic cytoplasm. Two cases showed neoplastic cell infiltration into the meninges and perivascular spaces. Silver staining showed lack of reticulin fiber production in the stroma of the neoplasms. Immunohistochemically, the neoplastic cells were strongly positive for Iba-1 and sporadically positive for CD68 in all four cases. On the basis of these results, all the neoplasms examined here could be distinguished from astrocytomas and diagnosed as malignant reticuloses. Thus, immunohistochemical demonstration of microglia/macrophage characters, such as using Iba-1, is considered to be helpful for differential diagnosis of malignant reticuloses from astrocytomas among spontaneously occurring primary brain neoplasms in rats.

GFAP-positive neoplastic astrocytes in spontaneous oligodendrogliomas and mixed gliomas of rats

It is generally said that neoplastic cells are immunohistochemically negative for glial fibrillary acidic protein (GFAP) in rat spontaneous astrocytomas, and there are no reports describing the existence of GFAP-positive neoplastic astrocytes in rat spontaneous oligodendrogliomas and mixed gliomas which contain neoplastic astrocytes. In the present study, to clarify whether GFAP-positive neoplastic astrocytes exist in rat spontaneous oligodendrogliomas and mixed gliomas or not, immunohistochemical examination was performed on spontaneous oligodendrogliomas (26 cases) and mixed gliomas (5 cases) collected from the carcinogenicity studies and short-term toxicity studies. The neoplastic cells that constitute oligodendrogliomas and mixed gliomas were morphologically classified into five types: round A, round B, round C, spindle, and bizarre. The cells of round A, B, and C types were thought to be neoplastic oligodendrocytes because of their positive immunostainability for Olig2.  The origin of bizarre cells was obscure because they were negative for Olig2, GFAP, and nestin. The spindle cells were considered to be neoplastic astrocytes, because some of them were positive for GFAP or nestin, and GFAP-positive spindle cells could be morphologically distinguished from reactive astrocytes.  In conclusion, the present study clarified for the first time that GFAP-positive neoplastic astrocytes exist in rat spontaneous gliomas.

Classification of Neural Tumors in Laboratory Rodents, Emphasizing the Rat

Neoplasms of the nervous system, whether spontaneous or induced, are infrequent in laboratory rodents and very rare in other laboratory animal species. The morphology of neural tumors depends on the intrinsic functions and properties of the cell type, the interactions between the neoplasm and surrounding normal tissue, and regressive changes. The incidence of neural neoplasms varies with sex, location, and age of tumor onset. Although the onset of spontaneous tumor development cannot be established in routine oncogenicity studies, calculations using the time of diagnosis (day of death) have revealed significant differences in tumor biology among different rat strains. In the central nervous system, granular cell tumors (a meningioma variant), followed by glial tumors, are the most common neoplasms in rats, whereas glial cell tumors are observed most frequently in mice. Central nervous system tumors usually affect the brain rather than the spinal cord. Other than adrenal gland pheochromocytomas, the most common neoplasms of the peripheral nervous system are schwannomas. Neural tumors may develop in the central nervous system and peripheral nervous system from other cell lineages (including extraneural elements like adipose tissue and lymphocytes), but such lesions are very rare in laboratory animals.

Histological and immunohistochemical studies on spontaneous rat astrocytomas and malignant reticulosis

Among spontaneous neoplasms of the rat central nervous system, the discrimination between astrocytoma and malignant reticulosis (MR) is sometimes difficult because of their similar cell morphology and infiltration patterns. In the present study, we carried out histological and immunohistochemical analyses on a total of sixty-four cases in Sprague-Dawley and F344 rats. These cases were diagnosed as benign/malignant astrocytoma containing no neoplastic oligodendroglial elements or MR according to the diagnostic criteria of the World Health Organization International Classification of Rodent Tumors (Mohr et al. 1994). Astrocytomas were divided into three types and MR into two types based on the number of lesions, cellularity and infiltration patterns, and so on. Although the neoplastic cells from all types showed various immunoreactivities for RM-4 (anti-rat macrophages and dendritic cells), ED-1, and/or vimentin, there were no distinctive differences among these types, and most cells that were positive for RM-4 were also positive for ED-1. None of the tumor types showed any reactivity for GFAP or S-100 protein. From the results of morphological and immunohistochemical examinations, it was indicated that there are no distinctive differences between spontaneous astrocytomas and MR in rats, and they are probably derived from the same cell lineage, that is, microglia, macrophage, or radial glia.