A recent paper by Bischoff et al. describes the effect of tissue acidification on mesenchymal stem cells. It is known that injured tissue is more acidic in comparison to healthy tissue, since injury is associated with reduced blood flow which results in hypoxic conditions and the accumulation of carbon dioxide, which lowers pH. In this study the investigators exposed mesenchymal stem cells that were derived from human bone marrow to various levels of acidity (7.4, 7.0, 6.7, and 6.4) from which they assessed the ability of the stem cells to generate interleukin-8 (IL-8), which is a pro-inflammatory chemotactic cytokine. The results correlated the lowest pH (6.4) with the maximum transcription of the IL-8 protein. Although the scientists were primarily interested in bone injury, their findings are applicable to a number of medical conditions including to the treatment of various types of tumors which are known to express a lower pH than non-malignant tissue. Further investigations will involve the administration of mesenchymal stem cells to patients with tumors, the lower acidity of which could possibly stimulate IL-8 which in turn could call in neutrophils that would eradicate the tumor via pro-inflammatory cytokines and other cellular mechanisms.
