The role of osteoblasts in regulating hematopoietic stem cell activity and tumor metastasis

Bone marrow stromal cells are critical regulators of hematopoiesis. Osteoblasts are part of the stromal cell support system in bone marrow and may be derived from a common precursor. Several studies suggested that osteoblasts regulate hematopoiesis, yet the entire mechanism is not understood. It is clear, however, that both hematopoietic precursors and osteoblasts interact for the production of osteoclasts and the activation of resorption. We observed that hematopoietic stem cells (HSCs) regulate osteoblastic secretion of various growth factors, and that osteoblasts express some soluble factors exclusively in the presence of HSCs. Osteoblasts and hematopoietic cells are closely associated with each other in the bone marrow, suggesting a reciprocal relationship between them to develop the HSC niche. One critical component regulating the niche is stromal-derived factor-1 (SDF-1) and its receptor CXCR4 which regulates stem cell homing and, as we have recently demonstrated, plays a crucial role in facilitating those tumors which metastasize to bone. Osteoblasts produce abundant amounts of SDF-1 and therefore osteoblasts play an important role in metastasis. These findings are discussed in the context of the role of osteoblasts in marrow function in health and disease.

Expression of Mucosal Cyto-Chemokine mRNAs in Patients with Helicobacter pylori Infection

BACKGROUND: Helicobacter pylori-induced destruction of the gastroduodenal mucosal barrier is initiated with mucosal infiltration of inflammatory cells. Cytokines and chemokines have been suggested to play important roles in the migration and activation of these inflammatory cells into the mucosa. The present study aimed to investigate expression rates of cyto-chemokine mRNAs using gastric mucosal biopsy specimens. METHODS: In 98 patients infected with Helicobacter pylori, mucosal mRNA expression rates of cytokines (IL-1beta, IL-6, and IL-10), C-C chemokines (macrophage inflammatory protein 1alpha [MIP-1alpha], and macrophage inflammatory protein 1beta [MIP-1beta], monocyte chemotactic and activating factor [MCAF], regulated on activation, normal T cell expressed and presumably secreted [RANTES]) and C-X-C chemokines (IL-8 and growth regulated alpha [GRO-alpha]) were examined using reverse transcription polymerase chain reaction (RT-PCR). RESULTS: The expression rates of mRNA for IL-8, GRO-alpha, MIP-1alpha and RANTES were significantly more increased in H. pylori-positive patients than in H. pylori- negative patients. However, the expressions of IL-1beta, IL-6 and IL-10 mRNA were statistically not different between two groups. After eradication of H. pylori, expressions of mRNA for three cytokines (IL-1beta, IL-6 and IL-10), four C-C chemokines (MIP-1alpha, MIP-1beta, MCAF and RANTES) and two C-X-C chemokines (IL-8 and GRO-alpha) were significantly decreased. CONCLUSION: These results suggest that C-X-C chemokines and some C-C chemokines play important roles in H. pylori-associated peptic ulcer diseases.