Microencapsulation of mesenchymal stem cells as a tool for studying the mechanisms of stem cell therapy of myocardial infarction

Introduction. Potential mechanisms of cell therapy benefit in myocardial ischemia include direct differentiation of stem cells into myocardial cells, stimulation of angiogenesis and differentiation of resident stem cells by paracrine factors secreted by autologous or allogeneic stem cells after intramyocardial injection. Dissection of the exact role of these mechanisms in the net effect of cell therapy can be aided by use of stem cell mircoencapsulation. Purpose. This work was aimed at: (i) evaluation of mesenchymal stem cells (MSC) viability and function after encapsulation in vitro and (ii) in vivo safety assessment of microencapsulated mesenchymal stem cells after intramyocardial transplantation. Methods. In order to encapsulate MSC from the rat bone marrow, the magneto-mechanical encapsulator was used. Sodium alginate in combination with a variety of coordinating agents (2.2 % BaCl₂, 1.2 % BaCl₂, and 1.5 % CaCl₂ was used as polymer for capsule formation. Stability assessment of capsules was made by incubation in phosphate buffer. The viability of encapsulated cells was evaluated in vitro by fluorescent staining by LIVE/DEAD Kit. Safety assessment of the intramyocardial transplantation of microencapsulated MSC was made in male Wistar rats weighing 225±25 g. Severity of systemic inflammation was assessed by leukocyte count in peripheral blood. Morphological and functional parameters of the heart were evaluated by echocardiography 5 days after transplantation. Results. In the result of this study standardized capsules were designed. The average diameter of the capsules was 225±25 μm. Capsule stabilization in 2.2 % barium chloride solution resulted in best stability (CaCl₂: swelling - 1 day, complete destruction - 5 days; BaCl₂: swelling - 14 days, complete destruction - more than 21 days), and viability of encapsulated cells (CaCl₂: after 30 min - 48±4 %, after 5 days - 18±2 %; BaCl₂: after 30 min - 63±6 %, after 5 days - 71±5 %). Intramyocardial injection of microcapsules had no effect on leukocyte count and morphofunctional parameters of the heart in comparison with control solution. Conclusion. The technique of MSC microencapsulation was designed with subsequent intramyocardial transplantation. Microencapsulation of MSC can be used to assess the role of paracrine factors in the mechanism of action of cell therapy on myocardial remodeling. Microencapsulation technique can also be used to protect stem cells from the effects of the host immune system and increase their survival early after intramyocardial transplantation.

микрокапсулы, альгинат, мезенхимные стволовые клетки, microcapsules, alginate, mesenchymal stem cells

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