Elastin-based hydrogel as a treatment for critical limb ischemia, an insight into the glyco-host response

Abstract

Critical limb ischemia (CLI) is severe impairment of the microcirculation resulting in inflammation, ischaemic pain, non-healing ulcers and gangrene. Over 20% of patients have no option but to undergo a major limb amputation. Therefore, the need to develop new therapies is urgent. To this end, there are three important aspects to be taken in account: 1) to have a preclinical model that would mimic as closely as possible the pathological events associated to CLI; 2) to understand the molecular basis of the pathological events, 3) to provide extracellular matrix inputs to the damaged tissue to stimulate the formation of new blood vessels. In the light of these considerations, this thesis has contributed to the field with a multidisciplinary approach. Firstly, a severe model of CLI was established and characterized in a wildtype mouse. The blood-flow recovery was severely impaired and histopathological features associated with ischemia - necrosis, inflammation, and spontaneous angiogenic response -were present. Secondly, this model was adopted to study the glycoenvironment modifications provoked by the ischemic insult. Among the biomolecules involved in the ischemic regeneration, glycans remain the least explored, despite their critical functional and structural roles. Although the role of glycans in mediating these pathological events has been reported, changes in the glycosignature following muscle ischemia remains poorly understood. Distinctive N-glycosylation modifications- increase of mannosidic species, alteration of sialylation type balance and reduction of hybrid and bisected glycans were identified. These modifications identified can serve as molecular targets and used when designing new therapeutic strategies. Finally, an Elastin-like hydrogel was tested for its potential modulation of the post-ischemic remodelling. Elastin is a natural protein present in the ECM that regulates specific cell pathways and mediates cell activities such as differentiation. Recently, Elastin-like recombinamers (ELRs) have demonstrated an angiogenic potential both in vitro and in vivo. The administration of an elastin-like recombinamers (ELRs) hydrogel was able to stimulate angiogenesis in a severe model of CLI. The hydrogel also induced the remodelling of ECM components towards the healthy state. N-glycosylation modulation were reported which suggested, in particular, the role of mannosylation and sialylation in mediating the healing effect. This study suggests that the ELRs hydrogel is a promising clinical candidate for the treatment of CLI, and identifies glycosylation alterations as potential new therapeutic targets.