The ERC Starting Grant project ExocyTher focuses on a cell-free therapy for digestive fistulas related to Crohn's disease. The aim is to investigate extracellular vesicles (EVs) released by stromal cells. The project proposes the concepts of (i) turbulence vesiculation for high-yield and large-scale EV production in bioreactors and (ii) thermo-controlled local EV delivery at the fistula.
Digestive fistulas are a major health burden related to Crohn's disease or secondary to surgery, cancer therapy or trauma. Digestive fistulas are an abnormal communication between two digestive organs or a digestive organ and the skin representing challenging conditions associated with low remission rates and high refractoriness. There is an urgent need of novel therapeutic approaches for this disease. Such unmet needs in digestive fistula management motivated the investigation of cell therapy based on the local administration of stromal cells (SCs). These cells display multiple therapeutic effects and one of the main ones is to reduce the inflammation favoring the fistula healing process. Although cell therapy results are encouraging, they are not fully satisfactory in terms of percentage of patients that achieve log-term disease remission, leaving place for a second generation therapy. SCs are known to release pro-survival and anti-inflammatory signals by means of extracellular vesicles (EVs) pointing out EV role in regenerative medicine. The ExocyTher project investigates an alternative to cell therapy approach, by proposing a minimally-invasive cell-free local therapy based on the regenerative effect of EVs from SCs. Formerly regarded as a “cell dust”, EVs, specially from SCs, are now considered as regenerative agents able to play an important role in the healing process. Previous studies showed the beneficial effect of SC EVs in the therapy of heart, kidney, liver, brain and skin injuries. We consider that SC EVs represent an eligible alternative for fistula therapy, as they recapitulate the regenerative effect of their mother cells while mitigating risks of uncontrolled replication and differentiation while offering “off-the-shelf”, storage and shelf-life gains. Our previous results in a clinically relevant fistula disease model clearly indicated that a therapy based on SC EVs was able to promote post-surgical digestive fistula healing.
Today, the main challenges for rendering EV-based regenerative medicine clinically feasible are large-scale high-yield standardized EV production and EV optimized administration. Concerning EV manufacturing, stringent requirements must be considered such as up-scaled and high-yield production fulfilling uniformity, consistency, purity and reproducibility criteria based on standardized and reliable quality control and compliance to good manufacturing practices (GMP). The way EVs are administered also represents a main concern considering that systemic administration results in rapid EV clearance and localization in off-target organs.
The ExocyTher project has the ambition to render viable the implementation of EV-based therapy by tackling EV production and administration technical barriers.
ExocyTher proposes large-scale high-yield EV production based on our patented concept of turbulence-vesiculation complying with a standardized production in GMP bioreactors in line with regulatory issues. ExocyTher set-up relies on the generation of a controlled turbulent flow in which turbulence microvortices will elicit a shear stress on cells triggering EV release. Our approach is bio-inspired based on EV release by the turbulent flow in bloodstream. This turbulence-based strategy is (i) time-saving enabling massive EV release in some hours, (ii) integrated as it is based on tuning the own GMP bioreactor stirring system, (iii) straightforward as no further processing is required to eliminate the trigger (turbulence disappearing when stirring is turned off) and (iv) scalable based on turbulence physical laws.
ExocyTher also proposes a thermo-actuated EV delivery in the fistula tract for eliciting an enhanced therapeutic effect in situ. ExocyTher strategy is expected to avoid systemic administration clearance and overcome difficulties related to local delivery, such as fistula secretions (washing-out the therapeutic agent) and fistula tract inaccessibility (sometimes irregular large defects of several centimeters). ExocyTher relies on dual biomaterial/EV component for fistula therapy. The thermoresponsive hydrogel biomaterial component is expected to cope with fistula local delivery difficulties promoting an occlusive effect, retaining EVs in the fistula tract and preventing EV wash-out by fistula secretions, while enabling the filling of the entire fistula tract despite its size and irregular morphology. Biomaterial choice was based on material physical and therapeutic properties and considered a clinical translation perspective. Building on strong preliminary results, we intend to investigate the combination of turbulence EVs with a poloxamer 407 hydrogel. ExocyTher proposes the off-label use of this hydrogel, which was a vessel occlusive medical device authorized in Europe, as an innovative fistula occlusive EV vehicle. This mechanical occlusive effect has an interest by itself in the therapy of digestive fistulas. Healing process is favored by decreasing the flow of secretions from the digestive system to the skin. Therefore, ExocyTher relies on a potential synergic effect of SC EVs and the thermoresponsive gel association.
ExocyTher fully considers key regulatory and manufacturing issues in the project choices to set the basis for implementing the first future clinical trial on SC EVs in a biomaterial for the therapy of digestive fistulas. Noteworthy, ExocyTher approaches may be extended to a multitude of EV parent cell types, or therapy indication. Therefore, the advances to be achieved in this project may also be relevant for unmet needs related to other diseases. We hope that the ExocyTher project may contribute in the future to democratize EVs as biotherapies for the management of digestive fistulas and other diseases with high morbidity or mortality. In a long-term perspective, by facilitating patient access to last generation therapies, ExocyTher technologies may improve the quality of life of refractory patients, tackling medical and societal challenges.
