[Frontiers in Bioscience E3, 371-379, January 1, 2011]

Bone marrow-derived microglia in pilocytic astrocytoma

Wafa AlShakweer1, Yazeed Alwelaie1, Aaron M. Mankung1, Manuel B. Graeber1,2

1Division of Neuropathology, Neurosciences Center and Department of Pathology and Clinical Laboratory Medicine, Faculty of Medicine, King Fahad Medical City, Riyadh, Kingdom of Saudi Arabia,2Brain Tumour Research Laboratories, The Brain and Mind Research Institute, University of Sydney, Camperdown NSW 2050, Sydney, Australia


1. Abstract
2. Introduction
3. Materials and methods
3.1. Tissue samples
3.2. Immunohistochemistry
3.3. In silico analysis
4. Results
5. Discussion
6. Acknowledgements
7. References


Tumour associated macrophages (TAMs) are increasingly recognized as supporters of tumour growth. The present study was undertaken to examine benign pilocytic astrocytomas (PAs) for the presence of M2 macrophages. We have asked the question whether TAMs in PAs share the predominant CD163 immunophenotype with tumour-associated microglia/macrophages of malignant gliomas. In addition, we were interested in the question whether there is evidence that the macrophages in PAs derive from resident microglia in surrounding normal brain or whether cells expressing a macrophage phenotype may invade PAs from the vasculature. The latter question is of great interest with regard to so-called "bone marrow-derived microglia" (BMDM) which may provide a physiological route of entry into the CNS that could be used for novel cell-based treatments of brain cancer. In fact, we have found strong morphological evidence for such macrophage recruitment into PAs. We propose therefore that PAs may be used as a model for the study of macrophage recruitment into gliomas. Importantly, our results also confirm that microglia/macrophage infiltration per se is not associated with malignant glioma behaviour.