Ultrastructural analysis of adult stem cells embedded into a hyaluronan-based scaffold suitable for cardiac repair

Abstract

The transplantation of scaffolds engineered with stem cells represents an encouraging tool for cardiac regeneration. In this study, mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) were grown into a hyaluronan-benzyl ester biocompatible non-woven mesh (Hyaff-11®, Fidia Advanced Biopolymers, Abano Terme, Padua, Italy) to evaluate their morphology, proliferation and spatial organization. Rat bone marrow MSCs were seeded on the top layer of the scaffold at density of 2×106 cells/cm2. After 24 h most MSCs were attached to the fibres and had migrated into the scaffold. The number of viable MSCs increased over a 3-week period at a doubling rate of 1 day. Both fluorescence and optical microscopy showed that MSCs strongly adhered to each fibre as evidenced by their spread morphology. Cell-to-fibre focal adhesion points and extracellular matrix components were also seen by electron microscopy. Peripheral blood-derived human EPCs adhered to hyaluronan with less strength than MSCs, as shown by their round shape. EPCs slowly proliferated into the scaffold and exhibited structural and functional features similar to those of mature endothelial cells (i.e. channels for transcytosis, basement membrane production, ac-LDL uptake). Thus, we suggest that non-woven Hyaff-11® could be considered a scaffold useful for cardiac engineering because it allows appropriate MSC organization and EPC differentiation. This research was funded by a grant of Compagnia di San Paolo, Turin, Italy.