Flexible nanofilms coated with aligned piezoelectric microfibers preserve the contractility of cardiomyocytes.

The use of engineered cardiac tissue for high-throughput drug screening/toxicology assessment remains largely unexplored. Here we propose a scaffold that mimics aspects of cardiac extracellular matrix while preserving the contractility of cardiomyocytes. The scaffold is based on a poly(caprolactone) (PCL) nanofilm with magnetic properties (MNF, standing for magnetic nanofilm) coated with a layer of piezoelectric (PIEZO) microfibers of poly(vinylidene fluoride-trifluoroethylene) (MNF+PIEZO). The nanofilm creates a flexible support for cell contraction and the aligned PIEZO microfibers deposited on top of the nanofilm creates conditions for cell alignment and electrical stimulation of the seeded cells. Our results indicate that MNF+PIEZO scaffold promotes rat and human cardiac cell attachment and alignment, maintains the ratio of cell populations overtime, promotes cell-cell communication and metabolic maturation, and preserves cardiomyocyte (CM) contractility for at least 12 days. The engineered cardiac construct showed high toxicity against doxorubicin, a cardiotoxic molecule, and responded to compounds that modulate CM contraction such as epinephrine, propranolol and heptanol.

Fibrin hydrogels functionalized with cartilage extracellular matrix and incorporating freshly isolated stromal cells as an injectable for cartilage regeneration.

UNLABELLED: Freshly isolated stromal cells can potentially be used as an alternative to in vitro expanded cells in regenerative medicine. Their use requires the development of bioactive hydrogels or scaffolds which provide an environment to enhance their proliferation and tissue-specific differentiation in vivo. The goal of the current study was to develop an injectable fibrin hydrogel functionalized with cartilage ECM microparticles and transforming growth factor (TGF)-ß3 as a putative therapeutic for articular cartilage regeneration. ECM microparticles were produced by cryomilling and freeze-drying porcine articular cartilage. Up to 2% (w/v) ECM could be incorporated into fibrin without detrimentally affecting its capacity to form stable hydrogels. To access the chondroinductivity of cartilage ECM, we compared chondrogenesis of infrapatellar fat pad-derived stem cells in fibrin hydrogels functionalized with either particulated ECM or control gelatin microspheres. Cartilage ECM particles could be used to control the delivery of TGF-ß3 to IFP-derived stem cells within fibrin hydrogels in vitro, and furthermore, led to higher levels of sulphated glycosaminoglycan (sGAG) and collagen accumulation compared to control constructs loaded with gelatin microspheres. In vivo, freshly isolated stromal cells generated a more cartilage-like tissue within fibrin hydrogels functionalized with cartilage ECM particles compared to the control gelatin loaded constructs. These tissues stained strongly for type II collagen and contained higher levels of sGAGs. These results support the use of fibrin hydrogels functionalized with cartilage ECM components in single-stage, cell-based therapies for joint regeneration. STATEMENT OF SIGNIFICANCE: An alternative to the use of in vitro expanded cells in regenerative medicine is the use of freshly isolated stromal cells, where a bioactive scaffold or hydrogel is used to provide an environment that enhances their proliferation and tissue-specific differentiation in vivo. The objective of this study was to develop an injectable fibrin hydrogel functionalized with cartilage ECM micro-particles and the growth factor TGF-ß3 as a therapeutic for articular cartilage regeneration. This study demonstrates that freshly isolated stromal cells generate cartilage tissue in vivo when incorporated into such a fibrin hydrogels functionalized with cartilage ECM particles. These findings open up new possibilities for in-theatre, single-stage, cell-based therapies for joint regeneration.