Tissue-Derived Signals for Mesenchymal Stem Cell Stimulation: Role of Cardiac and Umbilical Cord Microenvironments.

The tissue microenvironment regulates such stem cell behaviors as self-renewal and differentiation. Attempts to mimic components of these microenvironments could provide new strategies for culturing and directing the behavior of stem cells. The aim of the present study was to mimic cardiac and umbilical cord tissue microenvironments in vitro and compare the resulting bone marrow-derived mesenchymal stem cell (BM-MSC) behaviors. We generated tissue microenvironments using conditioned medium (CM) and extracellular matrix (ECM) samples obtained from human heart and umbilical cord tissue explant cultures and by tissue decellularization. Mass spectrometry and immunostaining were used to characterize and determine the specific protein profiles of the ECMs and CMs. We demonstrated that the ECMs and CMs were not cytotoxic to BM-MSCs and could thus be tested via cell culture. The BM-MSCs showed a higher proliferation rate when cultured with umbilical cord-derived CM compared with the other analyzed conditions. Furthermore, the ECMs increased cell adhesion and migration. However, although the conditions tested in this work were able to maintain the viability and affect the proliferation, adhesion and migration of BM-MSCs in vitro, mimicking tissue microenvironments using ECM and CM was not sufficient to induce the cardiomyogenic differentiation of BM-MSCs. The present study provides a thorough characterization of the biological activity of these ECMs and CMs in human BM-MSC cultures.

Comparison of cryopreserved homografts and decellularized porcine heterografts implanted in sheep.

This study evaluated cryopreserved homografts (Group 1) and porcine heterografts decellularized with deoxicholic acid (Group 2), implanted in the right ventricular outflow tract of juvenile sheep. Two groups with four animals in each were used and all animals survived with good outcome. Animals were sacrificed 90 or more days after surgery (90-150 days). On the third and fifth postoperative months they were submitted to echocardiographic examination with normal function and appearance observed for both groups. Explants were evaluated through histological analysis, atomic spectrophotometry and radiological examination. Calcium content was higher in the cusps of cryopreserved homografts, despite an otherwise similar macroscopic appearance between grafts of both groups. Decellularized heterografts were progressively repopulated by autologous cells suggesting some regenerative ability and longer durability than conventional homografts.