In conversation with

Ankita Das

on her recent study:

Das A, Nikhil A, Kumar A. Preparation of thermo-responsive polymer encapsulated exosomes and its role as a therapeutic agent for blood clot lysis. Colloids and Surfaces B: Biointerfaces. 2022 May 18:112580.

MFCEM: Congratulations Ankita to you and all authors of the study. Let me start by asking you, what gap does this study fill with respect to known and standard methods for thrombus degradation?
Ankita Das:
First of all, on behalf of all the authors, I would like to thank MFCEM for appreciating our work and thanks for the opportunity to discuss on the key aspects of the study.

To tackle the problem of arteries getting blocked by a clot, clinically the first line of defense is systemic injections of tissue plasminogen activators like streptokinase and urokinase. But this strategy has a downside in aspects of various side effects including bleeding and bruising at the injection site, blurred vision, fast heart rate, bleeding from the nose and gums, among others. So, such treatment has to be used with caution with other medications that alter platelet function and increase the risk of bleeding. Our group wanted to propose an effective solution for this problem with enhanced efficiency to fill the limitations of standard methods for thrombus degradation. So, in our study we selected a combinatorial injectable therapy where the treatment was provided locally to the clot, in comparison to the conventional systemic approach applied in the in vivo system. In this approach exosomes isolated from a cell line reported to have urokinase releasing activity have been utilized to check the thrombolytic effects and a thermo-responsive polymer was used as the delivery vehicle for exosomes. When exosome laden thermo-responsive polymer will be injected over the clot, polymer would undergo phase-change in situ and encapsulate the clot and there will be sustained release of the exosomes which will eventually lead to clot lysis. The sustained release approach has been adapted to avoid the risk of thrombo-embolism, which might occur if clot is detached from its site by direct treatment of exosome. Hence, the proposed treatment system will enable clot dissolution without associated limitations.

MFCEM: The study is very exhaustive, and I see that it spreads from harvesting exosomes from cell lines, to standardizing the polymer for encapsulation & release. What was the most challenging part of the study?
Ankita Das:
Yes, the study is quite extensive but has shown very interesting results. In this study, we have utilized different exosome concentrations and compared their activity with commercial tissue plasminogen activator (tPA) streptokinase. From the clot lysis activity assays which are routinely carried out for fibrinolytic drugs, we were able to deduce that these exosomes had the potential to serve as a replacement for streptokinase. Since, the activity of exosomes matched to that of streptokinase applied at a much higher concentration than the test tube equivalent (when a blood clot is placed in a static milieu), thereby showing the potential and application of these exosomes. The polymer solution was also optimized at a concentration where the released exosome will be sufficient enough in terms of concentration to carry out clot lysis. Challenge was to make a strategy that will be at par with the current clinical treatment strategies and study has to be designed such that its application will be clinically possible after its evaluation in pre-clinical trials. The ideology for this strategy was instigated by my mentor, Prof. Ashok Kumar, and our collective team effort yielded fruitful results.

MFCEM: Do you have any plans to test these polymer-encapsulated-exosomes for their efficacy in clot removal in animal models?
Ankita Das:
Yes, we are planning to test the efficacy of these polymer-encapsulated exosomes in animal model, where we will be generating a localized thrombus using chemical reagents and our combinatorial therapy will be utilized for clot degradation. The work will be carried out on a collaborative basis, and we are in the process of finalizing it.

MFCEM: What was the most satisfying aspect of this study?
Ankita Das:
Exosomes or extracellular vesicles (on a broader perspective) from stem cells have been utilized extensively for regenerative and therapeutic applications. In the present study, we wanted to explore the role of exosomes for thrombus degradation by taking into consideration previous literature reports about their plasminogen converting activity. We were able to satisfactorily lyse blood clots with these exosomes and also the use of a thermo-responsive polymer proved to be beneficial in encapsulating the blood clots so that the retained exosomes would be able to function better. Also, we were able to show that the exosome-based therapy is showing clot lysis effect similar to the clinically used drugs like streptokinase which has enhanced the scope and potential of the study many folds. This work was accompanied with high-risk, although the outcome came out as a high reward to us, and has also opened a new avenue in this field of research.