Heparin mimetics: Novel non-anticoagulant compounds to promote CNS repair.

Lead Research Organisation: University of Glasgow
Department Name: College of Medical, Veterinary &Life Sci

Abstract

Damage to the brain and spinal cord (together known as the central nervous system; CNS) is notoriously difficult to repair. In a disease such as multiple sclerosis damage occurs in which nerve processes lose their protective insulation wrapping (becoming "demyelinated", leading to faulty nerve signalling) and scarring forms in the tissue (called "astrogliosis", which prevents nerve regrowth). Current therapeutics tend to focus solely on altered immune responses, which cause damage, but not on other tissue changes. Repair is multifactorial and very complex, requiring a damping down of the immune response and scar tissue formation, as well as the promotion of re-insulation (myelination) and nerve outgrowth. Specialised sugar molecules that reside around the injury site, known as heparan sulphates (HS), carry out the regulation of many cellular functions required for repair. HS has varied patterns of sulphate groups on their surface, which by virtue of their number and position on the molecule can make neural cells carry out different types of functions. To study how HS works, we use chemical mimics of HS called heparin mimetics (mHeps). These mHeps are modified forms of the blood-thinning drug heparin but can be made chemically with altered amounts and positions of the sulphate groups. Using several assays in a Petri dish we have found that mHeps with a low number of sulphate groups promote remyelination, nerve process outgrowth and dampen down the scarring reactions. We also have some evidence that they can have a beneficial effect in animal models of disease, especially promoting remyelination, modulation of the immune response as well as general health (with less animal weight loss). For this reason, we now aim to carry out detailed experiments on the repair efficacy of a low sulphated mHep using an animal model of demyelination.

We aim to:
i) Confirm dosage, concentration and optimal molecular weight form of mHep7.
ii) Confirm preliminary data that mHep7 (comparing two MW forms) can promote repair in two pre-clinical animal models classically used to study CNS injury.
iii) Identify how the compounds work (ie. their mechanism-of-action), focusing on the immune response (which can enter the CNS and damage cells), weight gain (mHeps appear to promote CNS repair and animals appear healthier with less weight loss) and the integrity of the blood-brain barrier (BBB). The BBB prevents materials from the blood entering the brain. In disease, this can be leaky and allow the immune system to enter the brain, which can be harmful.

Overall we aim to show that low sulphated mHeps are potential new drugs to promote CNS repair by having a multi-modal effect on several key cellular properties induced after injury/disease.

Technical Summary

Damage to the CNS (e.g. in MS) is complex and results in multifocal areas of demyelination walled off by astrogliosis and axonal damage. By initially focussing on astrogliosis we discovered that highly sulphated heparan sulphates (HS) attenuate reactivity. By screening a panel of HS mimetics (mHeps), with varying levels of sulphation, we showed that exogenously added low sulphated (LS)-HS can reduce astrogliosis. Moreover, using complex myelinating cultures that mimic CNS injury we demonstrated that these LS-mHeps promoted remyelination and neurite outgrowth. Using mass spectrometry and cytokine/chemokine arrays we found that the mHeps sequester heparin-binding inhibitory molecules released after damage, resulting in the promotion of repair. Thus, mHeps have multifactorial effects on promoting CNS repair. Preliminary data using both the EAE and cuprizone models showed promising repair potential of LS-mHep7. Interestingly, mHep7 treated animals showed significantly less weight loss than controls during EAE disease onset. We now aim to corroborate these results through more extensive animal studies as well as identifying mechanism-of-action (focussing on the immune response, weight modulation and the integrity of the BBB) as follows:
i) Optimisation of the dose, concentration, mode of delivery and bioavailability of mHep7 by comparing the low MW form, expected to be more bioavailable.
ii) Confirm efficacy of the optimised mHep7 in both EAE and cuprizone animal models.
iii) Assess the mechanism-of-action in EAE mice by analysing the immune response (immunohistochemistry), multiplex assay, and FACS analysis, as well as correlating these findings with the prevention of weight loss by mHep7 treatment.
These studies will provide proof-of-concept for a novel strategy to enhance CNS repair by manipulating the inhibitory environment induced after injury using non-anticoagulant druggable mHeps, and will provide the foundation for developing clinical translation studies.

Planned Impact

The project will have significant impact by enhancing a number of research capacities relating to CNS repair, and ultimately the improvement of health as set out in our Impact Pathway document. The regulation of astrocytosis, myelination and axonal outgrowth by the novel interventions we will develop could have an economic impact on health and social well-being for a number of diseases in which these properties are perturbed. These include Multiple Sclerosis, spinal cord injury, Alexander's disease, Parkinson's disease, ALS etc. Effective therapeutic strategies have the potential to reduce the large negative economic impacts of these devastating diseases. Regarding potential exploitation of IP, we already have a granted EU and US patents on the use of the planned manipulation strategies, including the low sulphated heparin mimetics, and will continue to examine their role in regenerative medicine. There is significant potential for further new IP outputs from this project. We will actively monitor our research output and draft publications for potential IP opportunities, and protect these where relevant by liaising with the Universities' technology transfer office.

Who will benefit from this research?
Those who will benefit directly include scientists from other disciplines (e.g. pharmacology, molecular genetics, developmental biology) working on MS and other diseases with CNS damage, as well as the pharmaceutical industry, in particular in relation to the development of new therapies for the treatment of CNS repair. In the longer term, beneficiaries include human patients suffering from MS or CNS damage, and the clinicians responsible for their treatment. Specifically, both MS and spinal cord injury have no cures at present and it is therefore crucial to continue to work in the field. Thus, this work should have an impact on the health and well-being of patients. Improved treatments would be of considerable of great economic benefit to society.

How will they benefit from this research?
Offering a targeted approach of specific non-anticoagulant heparin-based drugs offers a novel, safe potential product that could be used therapeutically for currently unmet clinical needs. The project will provide an platform for collaborating with a pharmaceutical partner (e.g. IntelliHep, Liverpool spinout) which means positive results could quickly lead to commercial support for the next stages of translation of mHep7 to the clinic.