Introduction: One of the main problems in the rapid translation of preclinical cell‐basedtherapy to restore damaged myocardium is to find the best delivery route and the best time ofcell injection into the myocardium. Intramyocardial injection of stem cells is by far the mostuseddelivery technique in preclinical studies. Three‐dimensional scaffolds may be used todeliver a limited number of stem cells in their undifferentiated state, but many biomaterialsmay cause a foreign body reaction on their own. We have recently demonstrated that c‐Kitpositive cardiac progenitor cells are able to organize themselves into a tissue‐like cell mass incollagen I three‐dimensional cultures within 72h in 5% horse serum and that inside an OpenPore Poly‐lactic acid scaffold, commercially available, these cells can create an organizedelementary myocardium. Hypothesis: We assessed the hypothesis that poly‐lactic and fibroinscaffolds, designed to deliver cardiac progenitor cells in the infarcted region of the heart, mayinduce a better differentiation into cardiomyocytes. Methods: For the synthesis of PDLLAscaffolds, the Poly (D,L lactic acid) (RESOMER® 207, MW = 252 kDa) polimer were used (6.7%)in Dicloromethane/Dimetilformamide (DCM/DMF) 70/30 (v/v). The three‐dimensionalstructure was obtained by salt‐leaching, using NaCl crystals as porosity agent (NaCl < 224 μmand <150 μm). For the synthesis of fibroin scaffolds, degummed silk fibres were dried anddissolved into 9.3 m LiBr water solution (20% w/v) at 65°C for 3h. Scaffolds with differentporosities, pore size, and properties were made by freeze‐drying and salt‐leaching. Silk fibroinnets were created from silk powder after freeze‐drying. A net was made by electrospinning asolution containing 10% wt of fibroin solution in formic acid. To test the foreign body reactionscaffolds alone or embedded with collagen I and cardiac progenitor cells were implanted in thesubcutaneous dorsal region of athymic Nude‐Foxn1nu mice for 45 days. Results: Cardiacprogenitor cells were obtained by collagenase type II digestion of beating adult rat hearts, andtested after each preparation for the expression of c‐Kit, MDR‐1 and Sca‐1 by flow cytometry.These cells were able to partially differentiate into cardiomyocytes in vitro into all thesynthesized scaffolds in a M‐199 medium supplemented with 20% FBS within 21 days. Thedegree of differentiation and the expression of extracellular matrix and integrin proteinsdepended on the type of scaffold used. In vivo, all the used scaffolds induced a foreign bodyreaction, apart from fibroin nets. Cells implanted within scaffolds were rapidly degraded by theforeign body reaction. Cardiac stem cells alone implanted in nude mice were also degraded bya cell‐mediated immune response. Conclusions: Scaffolds are useful devices to deliver cardiacstem cells in the site of implantation, but more research is needed to find non‐reactivebiomaterials.
|Publication status||Published - 2011|