Bone marrow cells for cardiac regeneration and repair: current status and issues

Extensive studies in experimental animal heart models and patients have shown the promise of bone marrow cell (BMC) transplantation as an alternative strategy to the conventional treatment modalities for cardiac repair. 'Stemness' of BMC to adopt cardiac phenotype, their potential as carriers of exogenous therapeutic genes and an inherent ability to express growth factors and cytokines to exert paracrine effects have been especially focused until recently. These findings suggest that locally delivered BMCs are capable of regenerating de novo myocardium. Others have shown that extensive neovascularization due to paracrine effects of the engrafted cells resulted in improved regional blood flow and reduced infarct size. Despite initial success, there are multiple fundamental issues that remain contentious. Indeed, resolving these issues will optimize future heart cell therapy protocols to achieve better prognosis in the clinical settings. This review is a concise, in-depth and critical appreciation of the role of BMCs in heart cell therapy and builds a conceptual framework to elaborate their significance as a possible source of donor cells. Moreover, it discusses the current status of BMC transplantation as a clinical modality and the relevant issues confronting this approach in light of the published data with clinical relevance.