Stem cell niches exposed to tobacco smoke.

Stem cells (SC) were identified in both fetal and adult tissues. They appear a great potential for proliferation and differentiation. SC functions are affected by their local microenvironment, known as a SC niche, composed of extracellular matrix (ECM) and neighboring cells of other types. Both fetal and adult SC niches are potential targets for environmental pollutions. Environmental Tobacco Smoke (ETS) is one of the most dangerous sources of toxic and carcinogenic compounds. Adverse effect of tobacco smoke components on SC includes both direct influence on the cells and their regulatory mechanisms, as well as changes in SC microenvironment. Both mechanisms contribute to limitation of regenerative potential of the tissues. As targets for tobacco smoke during long-lasting active or passive smoking, SC can initiate malignant transformation. So called, cancer stem cells (CSC) exhibit some similarities as compared with SC, for example abilities of self-renewal and asymmetric divisions. Cancer treatment focused on CSC may contribute to increased efficiency of standard therapeutic methods. To sum up, effects of stem cells exposure to tobacco smoke may be particularly important in the context of tissue regeneration and carcinogenesis. Furthermore, SC exposure to tobacco smoke components may result in reduced number and quality of stem cells deposited in the tissue reservoirs. As a result the quality of SC derived from fetal (cord blood, amniotic fluid, placenta) and adult donors (i.e. bone marrow) for transplantations might be much reduced.