Functional regeneration of ischemic myocardium by transplanted cells overexpressing stromal cell-derived factor-1 (SDF-1): intramyocardial injection versus scaffold-based application

Mesenchymal Stem Cell Migration during Bone Formation and Bone Diseases Therapy

During bone modeling, remodeling, and bone fracture repair, mesenchymal stem cells (MSCs) differentiate into chondrocyte or osteoblast to comply bone formation and regeneration. As multipotent stem cells, MSCs were used to treat bone diseases during the past several decades. However, most of these implications just focused on promoting MSC differentiation. Furthermore, cell migration is also a key issue for bone formation and bone diseases treatment. Abnormal MSC migration could cause different kinds of bone diseases, including osteoporosis. Additionally, for bone disease treatment, the migration of endogenous or exogenous MSCs to bone injury sites is required. Recently, researchers have paid more and more attention to two critical points. One is how to apply MSC migration to bone disease therapy. The other is how to enhance MSC migration to improve the therapeutic efficacy of bone diseases. Some considerable outcomes showed that enhancing MSC migration might be a novel trick for reversing bone loss and other bone diseases, such as osteoporosis, fracture, and osteoarthritis (OA). Although plenty of challenges need to be conquered, application of endogenous and exogenous MSC migration and developing different strategies to improve therapeutic efficacy through enhancing MSC migration to target tissue might be the trend in the future for bone disease treatment.

Controlled Release of Collagen-Binding SDF-1α Improves Cardiac Function after Myocardial Infarction by Recruiting Endogenous Stem Cells

Stromal cell-derived factor-1α (SDF-1α) is a well-characterized chemokine that mobilizes stem cells homing to the ischemic heart, which is beneficial for cardiac regeneration. However, clinically administered native SDF-1α diffuses quickly, thus decreasing its local concentration, and results in side effects. Thus, a controlled release system for SDF-1α is required to produce an effective local concentration in the ischemic heart. In this study, we developed a recombinant chemokine, consisting of SDF-1α and a collagen-binding domain, which retains both the SDF-1α and collagen-binding activity (CBD-SDF-1α). In an in vitro assay, CBD-SDF-1α could specifically bind to a collagen gel and achieve sustained release. An intramyocardial injection of CBD-SDF-1α after acute myocardial infarction demonstrated that the protein was largely tethered in the ischemic area and that controlled release had been achieved. Furthermore, CBD-SDF-1α enhanced the recruitment of c-kit positive (c-kit⁺) stem cells, increased capillary density and improved cardiac function, whereas NAT-SDF-1α had no such beneficial effects. Our findings demonstrate that CBD-SDF-1α can specifically bind to collagen and achieve controlled release both in vitro and in vivo. Local delivery of this protein could mobilize endogenous stem cells homing to the ischemic heart and improve cardiac function after myocardial infarction.

Stem cell death and survival in heart regeneration and repair

Cardiovascular diseases are major causes of mortality and morbidity. Cardiomyocyte apoptosis disrupts cardiac function and leads to cardiac decompensation and terminal heart failure. Delineating the regulatory signaling pathways that orchestrate cell survival in the heart has significant therapeutic implications. Cardiac tissue has limited capacity to regenerate and repair. Stem cell therapy is a successful approach for repairing and regenerating ischemic cardiac tissue; however, transplanted cells display very high death percentage, a problem that affects success of tissue regeneration. Stem cells display multipotency or pluripotency and undergo self-renewal, however these events are negatively influenced by upregulation of cell death machinery that induces the significant decrease in survival and differentiation signals upon cardiovascular injury. While efforts to identify cell types and molecular pathways that promote cardiac tissue regeneration have been productive, studies that focus on blocking the extensive cell death after transplantation are limited. The control of cell death includes multiple networks rather than one crucial pathway, which underlies the challenge of identifying the interaction between various cellular and biochemical components. This review is aimed at exploiting the molecular mechanisms by which stem cells resist death signals to develop into mature and healthy cardiac cells. Specifically, we focus on a number of factors that control death and survival of stem cells upon transplantation and ultimately affect cardiac regeneration. We also discuss potential survival enhancing strategies and how they could be meaningful in the design of targeted therapies that improve cardiac function.

Cardiac regeneration and diabetes

The prevalence of diabetes continues to increase world-wide and is a leading cause of morbidity, mortality, and rapidly rising health care costs. Although strict glucose control combined with good pharmacological and non-pharmacologic interventions can increase diabetic patient life span, the frequency and mortality of myocardial ischemia and infarction remain drastically increased in diabetic patients. Therefore, more effective therapeutic approaches are urgently needed. Over the past 15 years, cellular repair of the injured adult heart has become the focus of a rapidly expanding broad spectrum of pre-clinical and clinical research. Recent clinical trials have achieved favorable initial endpoints with improvements in cardiac function and clinical symptoms following cellular therapy. Due to the increased risk of cardiac disease, cardiac regeneration may be one strategy to treat patients with diabetic cardiomyopathy and/or myocardial infarction. However, pre-clinical studies suggest that the diabetic myocardium may not be a favorable environment for the transplantation and survival of stem cells due to altered kinetics in cellular homing, survival, and in situ remodeling. Therefore, unique conditions in the diabetic myocardium will require novel solutions in order to increase the efficiency of cellular repair following ischemia and/or infarction. This review briefly summarizes some of the recent advances in cardiac regeneration in non-diabetic conditions and then provides an overview of some of the issues related to diabetes that must be addressed in the coming years.

Long-term follow-up after autologous skeletal myoblast transplantation in ischaemic heart disease

OBJECTIVES

Short-term follow-up after autologous skeletal myoblasts (ASM) transplantation (Tx) (Myoblast Autologous Grafting in Ischaemic Cardiomyopathy (MAGIC) Phase II Study) for the treatment of ischaemic cardiomyopathy revealed improved left ventricular (LV) remodelling. Our study reports the longest long-term worldwide follow-up of a single-centre cohort, focusing on the safety and efficacy of ASM-Tx.

METHODS

The multicentre MAGIC Phase II Study involved 120 patients and was conducted between 2004 and 2006. Out of the 120 patients involved in the entire study, the cohort treated at our institution contained 7 patients only. These 7 patients received ASM-Tx (injection volume: 400 million cells, n = 2 low dosage; 800 million cells, n = 2 high dosage) or placebo (n = 3) injections, in addition to coronary artery bypass grafting (CABG). After closure of the MAGIC registry, we conducted a long-term follow-up for our 7-patient cohort. The mean follow-up was 72.0 ± 5.3 months. The follow-up was complete for echo data, implanted cardioverter defibrillator (ICD) report, clinical investigation and New York Heart Association (NYHA) class.

RESULTS

At final follow-up, all the patients were alive, and 5 were in NYHA class 1 or 2. There were 6 hospitalizations for congestive heart failure during the follow-up (1 patient from each group). One patient (placebo group) was treated twice for ventricular fibrillation by the ICD. The LV ejection fraction remained stable in all the three groups (31.1 ± 3.9% preoperative vs 29.4 ± 4.4% at final follow-up). The LV volumes were reduced in the high-dosage group, remained unchanged in the low-dosage group and deteriorated in the placebo group.

CONCLUSIONS

Our long-term data confirm the findings of the MAGIC study. The LV function did not improve, but the long-term LV volumes in the high-dosage group were reduced. During the follow-up, there were also no additional arrhythmogenic incidences. Our data could imply that CABG in combination with ASM-Tx is safe and has beneficial therapeutic effects in the long-term. However, due to the small patient number, the clinical impact is limited.