Macrophage-induced blood vessels guide Schwann cell-mediated regeneration of peripheral nerves

The peripheral nervous system has remarkable regenerative capacities in that it can repair a fully cut nerve. This requires Schwann cells to migrate collectively to guide regrowing axons across a 'bridge' of new tissue, which forms to reconnect a severed nerve. Here we show that blood vessels direct the migrating cords of Schwann cells. This multicellular process is initiated by hypoxia, selectively sensed by macrophages within the bridge, which via VEGF-A secretion induce a polarized vasculature that relieves the hypoxia. Schwann cells then use the blood vessels as "tracks" to cross the bridge taking regrowing axons with them. Importantly, disrupting the organization of the newly formed blood vessels in vivo, either by inhibiting the angiogenic signal or by re-orienting them, compromises Schwann cell directionality resulting in defective nerve repair. This study provides important insights into how the choreography of multiple cell-types is required for the regeneration of an adult tissue

The Identification of CELSR3 and Other Potential Cell Surface Targets in Neuroendocrine Prostate Cancer.

UNLABELLED Although recent efforts have led to the development of highly effective androgen receptor (AR)-directed therapies for the treatment of advanced prostate cancer, a significant subset of patients will progress with resistant disease including AR-negative tumors that display neuroendocrine features [neuroendocrine prostate cancer (NEPC)]. On the basis of RNA sequencing (RNA-seq) data from a clinical cohort of tissue from benign prostate, locally advanced prostate cancer, metastatic castration-resistant prostate cancer and NEPC, we developed a multi-step bioinformatics pipeline to identify NEPC-specific, overexpressed gene transcripts that encode cell surface proteins. This included the identification of known NEPC surface protein CEACAM5 as well as other potentially targetable proteins (e.g., HMMR and CESLR3). We further showed that cadherin EGF LAG seven-pass G-type receptor 3 (CELSR3) knockdown results in reduced NEPC tumor cell proliferation and migration in vitro. We provide in vivo data including laser capture microdissection followed by RNA-seq data supporting a causal role of CELSR3 in the development and/or maintenance of the phenotype associated with NEPC. Finally, we provide initial data that suggests CELSR3 is a target for T-cell redirection therapeutics. Further work is now needed to fully evaluate the utility of targeting CELSR3 with T-cell redirection or other similar therapeutics as a potential new strategy for patients with NEPC. SIGNIFICANCE The development of effective treatment for patients with NEPC remains an unmet clinical need. We have identified specific surface proteins, including CELSR3, that may serve as novel biomarkers or therapeutic targets for NEPC

A novel role for macrophages in peripheral nerve regeneration

Peripheral nerves are one of the few adult tissues which can regenerate following injury, and macrophages have many important roles in this multicellular process. Following nerve injury, regrowing axons must traverse tissue termed the ‘nerve bridge’, which forms spontaneously between the nerve stumps (proximal and distal), to reconnect with their original tissue target. Previously, we found that hypoxic macrophages in the bridge induce the formation of a polarised vasculature which dedifferentiated Schwann cells subsequently use as a scaffold to migrate along, taking axons with them into the distal stump. Here, macrophages together with Schwann cells function to clear debris and remodel the environment to facilitate axonal regeneration, demonstrating distinct functions for macrophages within discrete areas of the regenerating nerve. This thesis aims to characterise nerve macrophage populations and to determine whether there is a specific Schwann cell chemoattractant within the bridge. Resident nerve macrophages displayed a distinct gene expression pattern compared to other resident macrophage populations. Moreover, we found two distinct nerve resident populations which can be distinguished by CX3CR1 expression and physiological location. In the injured nerve, the origin and phenotype of macrophage populations is currently unknown. We determined that the majority of macrophages in the bridge and distal stump are monocyte-derived. In further characterisation of bridge macrophages, we have identified an intrinsic ability to differentially sense hypoxia. Here we show data to support a novel role for hypoxic bridge macrophages in promoting Schwann cell migration. Using in vitro chemotaxis assays, we found that hypoxic macrophages are able to induce Schwann cell migration and an unbiased screen identified the chemoattractant factor as CCL3. CCL3 is able to induce Schwann cell migration in chemotactic assays, and knockdown studies showed that CCL3 is the primary chemoattractant secreted by hypoxic macrophages. We also present preliminary in vivo experiments investigating the role of CCL3 following injury, as well as in models of nerve repair. A Schwann cell chemoattractant factor has wide therapeutic implications in peripheral nerve injury, as well as potential uses in the treatment of aberrant nerve growth and tumour spread