No abstract

Transplantation of embryonic stem cells (ESCs) can improve cardiac function in treatment of myocardial infarction. The low rate of cell retention and survival within the ischemic tissues makes the application of cell transplantation techniques difficult. In this study, we used a temperature-responsive chitosan hydrogel (as scaffold) combined with ESCs to maintain viable cells in the infarcted tissue. Temperature-responsive chitosan hydrogel was prepared and injected into the infarcted heart wall of rat infarction models alone or together with mouse ESCs. The result showed that the 24-h cell retention and 4 week graft size of both groups was significantly greater than with a phosphate buffered saline control. After 4 weeks of implantation, heart function, wall thickness, and microvessel densities within the infarct area improved in the chitosan + ESC, chitosan, and ESC group more than the PBS control. Of the three groups, the chitosan + ESC performed best. Results of this study indicate that temperature-responsive chitosan hydrogel is an injectable scaffold that can be used to deliver stem cells to infarcted myocardium. It can also increase cell retention and graft size. Cardiac function is well preserved, too.

The purpose of this study has been to investigate the possible effects of the normal joint cavity environment on chondrocytic differentiation of bone-marrow-derived mesenchymal stem cells (MSCs). Autologous bone marrow was aspirated from the iliac crest of male sheep. MSCs were purified, expanded, and labeled with the fluorescent dye PKH26. Labeled MSCs were then grown on a three-dimensional porous scaffold of poly (L-lactic-co-glycolic acid) in vitro and implanted into the joint cavity by a surgical procedure. At 4 or 8 weeks after implantation, the implants were removed for histochemical and immunohistochemical analysis. The cells labeled with red fluorescent PKH26 in the implants expressed type II collagen and synthesized sulfated proteoglycans. However, the osteoblast-specific marker, osteocalcin, was not detected by immunohistochemistry indicating that the implanted MSCs had not differentiated into osteoblasts by being directly exposed to the normal joint cavity. To investigate the possible factors involved in chondrocytic differentiation of MSCs further, we co-cultured sheep MSCs with the main components of the normal joint cavity, viz., synovial fluid or synovial cells, in vitro. After 1 or 2 weeks of co-culture, the MSCs in both co-culture systems expressed markers of chondrogenesis. These results suggest that synovial fluid and synovium from normal joint cavity are important for the chondrocytic differentiation of adult bone-marrow-derived MSCs.

Recently, the presence of telocytes was demonstrated in human and mammalian tissues and organs (digestive and extra-digestive organs, genitourinary organs, heart, placenta, lungs, pleura, striated muscle). Noteworthy, telocytes seem to play a significant role in the normal function and regeneration of myocardium. By cultures of telocytes in two- and three-dimensional environment we aimed to study the typical morphological features as well as functionality of telocytes, which will provide important support to understand their in vivo roles. Neonatal rat cardiomyocytes were isolated and cultured as seeding cells in vitro in two-dimensional environment. Furthermore, engineered myocardium tissue was constructed from isolated cells in three-dimensional collagen/Matrigel scaffolds. The identification of telocytes was performed by using histological and immunohistochemical methods. The results showed that typical telocytes are distributed among cardiomyocytes, connecting them by long telopodes. Telocytes have a typical fusiform cell body with two or three long moniliform telopodes, as main characteristics. The vital methylene blue staining showed the existence of telocytes in primary culture. Immunohistochemistry demonstrated that some c-kit or CD34 immuno-positive cells in engineered heart tissue had the morphology of telocytes, with a typical fusiform cell body and long moniliform telopodes. Also, a significant number of vimentin+ telocytes were present within engineered heart tissue. We suggest that the model of three-dimensional engineered heart tissue could be useful for the ongoing research on the functional relationships of telocytes with cardiomyocytes. Because the heart has the necessary potential of changing the muscle and non-muscle cells during the lifetime, telocytes might play an active role in the heart regeneration process. Moreover, telocytes might be a useful tool for cardiac tissue engineering.

In this study, an injectable, biodegradable hydrogel composite of oligo[poly(ethylene glycol) fumarate] (OPF) was investigated as a carrier of mouse embryonic stem cells (mESCs) for the treatment of myocardial infarction (MI). The OPF hydrogels were used to encapsulate mESCs. The cell differentiation in vitro over 14 days was determined via immunohistochemical examination. Then, mESCs encapsulated in OPF hydrogels were injected into the LV wall of a rat MI model. Detailed histological analysis and echocardiography were used to determine the structural and functional consequences after 4 weeks of transplantation. With ascorbic acid induction, mESCs could differentiate into cardiomyocytes and other cell types in all three lineages in the OPF hydrogel. After transplantation, both the 24-hr cell retention and 4-week graft size were significantly greater in the OPF + ESC group than that of the PBS + ESC group (P < 0.01). Four weeks after transplantation, OPF hydrogel alone significantly reduced the infarct size and collagen deposition and improved the cardiac function. The heart function and revascularization improved significantly, while the infarct size and fibrotic area decreased significantly in the OPF + ESC group compared with that of the PBS + ESC, OPF and PBS groups (P < 0.01). All treatments had significantly reduced MMP2 and MMP9 protein levels compared to the PBS control group, and the OPF + ESC group decreased most by Western blotting. Transplanted mESCs expressed cardiovascular markers. This study suggests the potential of a method for heart regeneration involving OPF hydrogels for stem cell encapsulation and transplantation.