Investigating the functions and therapeutic potential for Eph receptors and ephrins during wound repair and inflammation
Lead Research Organisation:
University of Bristol
Department Name: Biochemistry
Abstract
Wound healing is the body?s process of repairing damaged tissue and takes place for all wounds, be they a nick to the finger or the repair of internal organs after abdominal surgery.
There are many occasions when tissue repair fails, leading to chronic non-healing wounds such as venous leg ulcers which are a huge clinical burden for elderly patients and suffered by about 500,000 people in the UK. Equally, the process can be too exuberant leading to fibrosis and scarring as a consequence of excessive contraction, healing and inflammation. In order to understand how tissue repair goes awry and how it might be improved, we need to better understand the process, and essentially that means figuring out how the dormant tissues of unwounded skin (or other organs), are awakened upon damage, allowing them to migrate and fill the gap created by the wound, and how they know when to stop when the wound is healed.
The studies outlined here are to investigate a family of receptors and the proteins that bind to them, the Ephs and ephrins, that, despite being very well studied in embryonic development and in cancer and implicated in regulating the ?starting and stopping? of cell migrations in both these scenarios, have not previously been studied in the wound repair process.
We have preliminary data in mouse that shows how several members of this large family of receptors become expressed and activated in particular cell types during the wound closure process, in ways that are suggestive of their being key players, and we will look to see whether the same is true in human wound tissues and whether biopsies from pathological wounds, in particular longstanding leg ulcers, have an altered pattern of these receptors.
We will then test whether modulating particular Eph family members will allow us to alter and improve some aspects of healing while not affecting others, with a view to designing therapies that can either ?kickstart? the tissues of a non-healing wound to repair itself or shut down the repair machinery in a wound that is too inflamed and/or too exuberant and likely to form a bad scar.
There are many occasions when tissue repair fails, leading to chronic non-healing wounds such as venous leg ulcers which are a huge clinical burden for elderly patients and suffered by about 500,000 people in the UK. Equally, the process can be too exuberant leading to fibrosis and scarring as a consequence of excessive contraction, healing and inflammation. In order to understand how tissue repair goes awry and how it might be improved, we need to better understand the process, and essentially that means figuring out how the dormant tissues of unwounded skin (or other organs), are awakened upon damage, allowing them to migrate and fill the gap created by the wound, and how they know when to stop when the wound is healed.
The studies outlined here are to investigate a family of receptors and the proteins that bind to them, the Ephs and ephrins, that, despite being very well studied in embryonic development and in cancer and implicated in regulating the ?starting and stopping? of cell migrations in both these scenarios, have not previously been studied in the wound repair process.
We have preliminary data in mouse that shows how several members of this large family of receptors become expressed and activated in particular cell types during the wound closure process, in ways that are suggestive of their being key players, and we will look to see whether the same is true in human wound tissues and whether biopsies from pathological wounds, in particular longstanding leg ulcers, have an altered pattern of these receptors.
We will then test whether modulating particular Eph family members will allow us to alter and improve some aspects of healing while not affecting others, with a view to designing therapies that can either ?kickstart? the tissues of a non-healing wound to repair itself or shut down the repair machinery in a wound that is too inflamed and/or too exuberant and likely to form a bad scar.
Technical Summary
Wound healing is an evolutionary conserved process that enables all multicellular organisms to survive traumas. The repair process is generally efficient but there are many occasions when it fails or is too exuberant which leads, at one extreme, to chronic non-healing wounds or, at the other, to fibrosis and scarring. In this project we aim to investigate the role(s) of Eph receptors and their ephrin ligands in the normal process of skin wound healing and how these may be perturbed in chronic non-healing wounds and potentially modulated in order to improve tissue repair.
Microarray comparison of the repair transcriptomes of PU.1 null mice, where inflammatory cells are absent, versus those of wild type sibs, reveals both inflammation-dependent and independent wound healing genes (Cooper et al, Genome Biol 2005). This study highlighted how several members of the Eph family of receptors are dramatically up and down regulated with different timecourses post wounding. These receptors, which form the largest family of tyrosine kinase receptors in the mammalian genome, are already well established as regulators of cell migration during embryonic development and cancer, but have not yet been investigated in the context of skin repair. Led by this microarray result, our subsequent PCR and immunohistochemical studies in mice confirm that several of the Ephs and their ephrin ligands might be key regulators of migration in the various wound cell lineages, with particular receptor/ligand pairings being restricted to specific cell lineages, thus offering opportunities to therapeutically modulate some cell lineages while not disturbing others. We propose a systematic survey of these receptors and their ligands, and the activity states of receptors, during the various phases of the repair response, and we will test function using tissue specific knockout mouse strategies complemented by pharmacological and cell co-culture studies. In particular, we will be looking for Eph/ephrin pairings that may drive epidermal migration and stopping/fusing, wound angiogenesis, and/or the wound inflammatory response and its fibrotic consequences. Through a recently initiated collaboration with Prof Harding, who has a wound healing clinic in Cardiff, we will also examine how the Eph/ephrin signature we see in the healthy, acute wound repair process is disrupted in patients with chronic wound healing conditions, with a view to therapeutically modulating particular Eph/ephrin signals to enhance aspects of the repair process that have gone awry in such wounds.
Microarray comparison of the repair transcriptomes of PU.1 null mice, where inflammatory cells are absent, versus those of wild type sibs, reveals both inflammation-dependent and independent wound healing genes (Cooper et al, Genome Biol 2005). This study highlighted how several members of the Eph family of receptors are dramatically up and down regulated with different timecourses post wounding. These receptors, which form the largest family of tyrosine kinase receptors in the mammalian genome, are already well established as regulators of cell migration during embryonic development and cancer, but have not yet been investigated in the context of skin repair. Led by this microarray result, our subsequent PCR and immunohistochemical studies in mice confirm that several of the Ephs and their ephrin ligands might be key regulators of migration in the various wound cell lineages, with particular receptor/ligand pairings being restricted to specific cell lineages, thus offering opportunities to therapeutically modulate some cell lineages while not disturbing others. We propose a systematic survey of these receptors and their ligands, and the activity states of receptors, during the various phases of the repair response, and we will test function using tissue specific knockout mouse strategies complemented by pharmacological and cell co-culture studies. In particular, we will be looking for Eph/ephrin pairings that may drive epidermal migration and stopping/fusing, wound angiogenesis, and/or the wound inflammatory response and its fibrotic consequences. Through a recently initiated collaboration with Prof Harding, who has a wound healing clinic in Cardiff, we will also examine how the Eph/ephrin signature we see in the healthy, acute wound repair process is disrupted in patients with chronic wound healing conditions, with a view to therapeutically modulating particular Eph/ephrin signals to enhance aspects of the repair process that have gone awry in such wounds.