Use of rats mesenchymal stem cells modified with mHCN2 gene to create biologic pacemakers

Transcription factor TBX18 promotes adult rat bone mesenchymal stem cell differentiation to biological pacemaker cells

Bone mesenchymal stem cells (BMSCs) are currently considered the optimal stem cells for biological pacemaker cell transformation. The cardiac-specific transcription factor T-Box protein 18 (TBX18) is essential for sinoatrial node (SAN) formation, particularly formation of the head region that generates the electrical impulses that induce heart contraction. The present study aimed to confirm the effects of TBX18 on biological pace-maker differentiation of rat BMSCs. Flow cytometry was used to identify the surface markers of BMSCs, in order to acquire pure mesenchymal stem cells. Subsequently, BMSCs were transduced with TBX18 or green fluorescent protein adenovirus vectors. The effects of TBX18 were evaluated using SAN-specific makers including TBX18, α-actin, cardiac troponin I, hyperpolarization-activated cyclic nucleotide-gated channel 4 and connexin 43 by reverse transcription-quantitative polymerase chain reaction, western blotting and immunofluorescence. The findings demonstrated that direct conversion of BMSCs to biological pacemaker cells via TBX18 is a feasible method in the field of cardiology.

Effect of mHCN2 gene modification on chronotropic relevant receptors in BMSCs co-cultured with atrial myocytes

Currently, the mechanism of the chronotropic ability of stem cells modified to express the hyperpolarization-activated cyclic nucleotide-gated (HCN) gene remains to be elucidated. The present study assessed the effects of mouse (m)HCN2 gene modification on the expression of chronotropic relevant receptors, adrenergic receptor β1 (Adrb1) and cholinergic receptor muscarinic M2 (Chrm2), in bone marrow stromal cells (BMSCs) co-cultured with atrial myocytes. BMSCs were divided into the following four groups: i) BMSCs transfected with the mHCN2 gene and co-cultured with atrial myocytes for 48 h (TF + CO); ii) respective transfection (TF); iii) respective co-culture (CO); and iv) the control group without treatment (CTL). Green fluorescent protein (GFP) was observed in the BMSCs 48 h after transfection with pEGFP-C1-mHCN2. The expression of Adrb1 and Chrm2 was significantly increased in the TF and TF + CO groups, particularly the TF + CO group, compared with the CTL group (P<0.05). This suggests that BMSCs modified to express the mHCN2 gene possess autorhythmicity and chronotropic ability, particularly when co-cultured with atrial myocytes. The results of the present study provide novel information regarding the molecular basis of biological pacemakers' chronotropic ability.

(Re-)programming of subtype specific cardiomyocytes

Adult cardiomyocytes (CMs) possess a highly restricted intrinsic regenerative potential - a major barrier to the effective treatment of a range of chronic degenerative cardiac disorders characterized by cellular loss and/or irreversible dysfunction and which underlies the majority of deaths in developed countries. Both stem cell programming and direct cell reprogramming hold promise as novel, potentially curative approaches to address this therapeutic challenge. The advent of induced pluripotent stem cells (iPSCs) has introduced a second pluripotent stem cell source besides embryonic stem cells (ESCs), enabling even autologous cardiomyocyte production. In addition, the recent achievement of directly reprogramming somatic cells into cardiomyocytes is likely to become of great importance. In either case, different clinical scenarios will require the generation of highly pure, specific cardiac cellular-subtypes. In this review, we discuss these themes as related to the cardiovascular stem cell and programming field, including a focus on the emergent topic of pacemaker cell generation for the development of biological pacemakers and in vitro drug testing.