سید حسین احمدی تفتی

Injectable hydrogels that mimic heart tissues can be considered a promissing perspective towards the future developments of cardiac tissue engineering. This study aims to fabricate an injectable, thermosensitive hydrogel consisting of chitosan/gelatin/glycerol phosphate. Due to their unique electro-conductivity characteristic, hydrogels can provide a suitable environment to accelerate cardiac cell proliferation. Polyaniline/multi-walled carboxylated carbon nanotube (PAni/c-MWNT) was prepared using Sodium Dodecyl Sulfate (SDS) emulsion. To prevent the interaction between the PAni/c-MWNT nanocomposite and hydrogel, the nanocomposite was coated with gelatin to form polyaniline/carboxylated carbon nanotube/gelatin (PAni/c-MWNT/G). The PAni/c-MWNT/G nanocomposite was then dispersed to provide electrical signals throughout the hydrogel. The gelation time, gel temperature, and mechanical properties of the hydrogel were measured using a rheometer. FTIR spectroscopy results revealed that the interaction between the aniline and c-MWNT/G could change the position of the quinone and benzene peaks. The conductivity of hydrogel-containing nanocomposite was found to be higher than that of c-MWNT and PAni. Scanning Electron Microscopy (SEM) confirmed the uniform distribution of PAni/c-MWNT/G nanocomposite throughout the hydrogel. The degradation rate of conductive hydrogel is lower than that of pure hydrogel. The MTT assay test showed the biocompatibility of the cell-hydrogel. Finally, Mesenchymal Stem Cells (MSCs) were cultured in the hydrogels for 14 days. Cell adhesion, cell viability, and proliferation were also examined. This study utilized PAni/c-MWNT/G, for the first time, to enhance the electro-conductivity of chitosan/gelatin/glycerol phosphate hydrogel. This conductive thermosensitive injectable hydrogel can be used to regenerate cardiac tissue and other electroactive tissues.

Cardiovascular disease is one of the leading causes of death worldwide. Mesenchymal stem cells (MSCs) are one of the most common sources of cell-based therapies in heart regeneration. There are several approaches to differentiate MSCs into cardiac-like cells, such as genetic modification. In addition, using of 3D culture, such as hydrogels, increases the efficiency of differentiation.

In the present study, lentiviruses containing microRNA 1 (miR- 1) and myocardium (Myocd) were co-transducted to mouse adipose-derived MSCs. Three days after, transduced MSCs were transferred to a hydrogel containing chitosan and collagen. After 21 days, the differentiation of encapsulated cells was evaluated. In this regard, the expression of cardiac markers such as NK2 homeobox 5 (Nkx2-5), GATA binding protein 4 (Gata4) and troponin T type 2 (Tnnt2) at the level of gene and protein were investigated.

The results of real-time quantitative polymerase chain reaction (qRT-PCR) and immunocytochemistry showed that co-induction of miR-1 and Myocd in MSCs followed by transfer to composite hydrogel increased the expression of cardiac markers.

The use of 3D culture such as chitosan/collagen hydrogel improves the differentiation of MSCs and subsequently obtains more mature cells for use in cell-based regenerative medicine

Atrial and ventricular arrhythmias are among the most common complications after coronary artery bypass graft (CABG) surgery. Previous studies demonstrated that cardiopulmonary bypass itself results in reduced serum magnesium levels. In this study, we evaluated the effect of total blood magnesium level (TMG) on the prevention of perioperative arrhythmias with routine regimens of 2-4 grams supplemental magnesium (SMG).

TMG was measured in patients who were scheduled for CABG on three occasions: just before anesthesia, just after entering the intensive care unit (ICU) after completion of the sugery, and on the first morning after the operation. Patients were evaluated for primary cardiac rhythm and other variables that could have an influence on the magnesium level, including serum creatinine, urine output in the operating room and diuretic therapy. The SMG dosage was also recorded in the operating room and ICU. Patients were then evaluated for the rate and type of arrhythmia for the next three days.

The mean TMG levels in 174 cases were 2.2 (0.5), 2.6 (0.6) and 2.4 (0.6) mg/dl for the three occasions, respectively. The mean SMG was 2.5 (1.2) grams. Of 164 patients, 51 (31%) developed the following post-operative arrhythmias: AF (7.3%), non- AF SVA (15.2%) and ventricular (16.5%). The mean serum creatinine level and urine output were 1.2 mg/dl and 1800 ml, respectively. Although there was a significant difference between the TMG levels on the three different occasions (P<0.001), all values were within normal range. When we stratified the TMG levels of the patients based on administered SMG, the Mentel-Haenszel test revealed no significant difference between the first and third TMG (P=0.6). Although the TMG levels were higher in arrhythmic patients compared to those without arrhythmia (2.25 vs. 2.14 mg/dl), both values were within the normal range and there was no significant difference between the two groups. Serum creatinine levels and urine volume were not related to TMG levels.

This study indicates that routine magnesium administration has no significant effect on SMG levels. Also, serum creatinine and urine output are not determinant factors for SMG administration. There was no correlation between TMG levels and perioperative arrhythmia. We conclude that the routine regimen of magnesium administration has no effect on the incidence of perioperative arrhythmia, though it is necessary for maintaining normal magnesium levels.