Decreased soluble TGF-β1, Tie-2, and angiopoietins serum levels in bone marrow after treating healthy donors with granulocyte colony-stimulating factor

TGFBI Expressed by Bone Marrow Niche Cells and Hematopoietic Stem and Progenitor Cells Regulates Hematopoiesis

The interactions of hematopoietic stem and progenitor cells (HSPCs) with extracellular matrix (ECM) components and cells from the bone marrow (BM) microenvironment control their homeostasis. Regenerative BM conditions can induce expression of the ECM protein transforming growth factor beta-induced gene H3 (TGFBI or BIGH3) in murine HSPCs. In this study, we examined how increased or reduced TGFBI expression in human HSPCs and BM mesenchymal stromal cells (MSCs) affects HSPC maintenance, differentiation, and migration. HSPCs that overexpressed TGFBI showed accelerated megakaryopoiesis, whereas granulocyte differentiation and proliferation of granulocyte, erythrocyte, and monocyte cultures were reduced. In addition, both upregulation and downregulation of TGFBI expression impaired HSPC colony-forming capacity of HSPCs. Interestingly, the colony-forming capacity of HSPCs with reduced TGFBI levels was increased after long-term co-culture with MSCs, as measured by long-term culture-colony forming cell (LTC-CFC) formation. Moreover, TGFBI downregulation in HSPCs resulted in increased cobblestone area-forming cell (CAFC) frequency, a measure for hematopoietic stem cell (HSC) capacity. Concordantly, TGFBI upregulation in HSPCs resulted in a decrease of CAFC and LTC-CFC frequency. These results indicate that reduced TGFBI levels in HSPCs enhanced HSC maintenance, but only in the presence of MSCs. In addition, reduced levels of TGFBI in MSCs affected MSC/HSPC interaction, as observed by an increased migration of HSPCs under the stromal layer. In conclusion, tight regulation of TGFBI expression in the BM niche is essential for balanced HSPC proliferation and differentiation.

The kinetics of hematopoietic niche cytokines and their influence on mobilization efficacy and timing in patients with hematological malignancies

The bone marrow niche functions are modulated by complicated cytokines network. The aim of our study was to evaluate the levels of VCAM-1, VEGF, MMP-9 and SDF during mobilization of CD34+ cells in patients with hematological malignancies. Thirty four patients were enrolled to the study (19F, 15 M) at median age of 57 years. The group consisted of patients with multiple myeloma (26) and lymphoma (8). The mobilization procedures comprised chemotherapy and then G-CSF. Blood samples were collected before chemotherapy (N = 34) and on the day of the first apheresis (N = 26). Cytokines were evaluated with ELISA assay. We observed significant increase in VCAM-1 levels during mobilization. On contrary, VEGF and SDF levels decreased during mobilization procedure. The levels of MMP-9 were stable during mobilization. We divided patients according to baseline cytokines levels below and above median into "low" and "high" expressors. The group of VEGF "low" expressors had longer median time of G-CSF treatment before first apheresis than 'high' expressors. Baseline VEGF levels correlated adversely with duration of G-CSF treatment before first apheresis. Patients were also divided according to median cytokines levels at apheresis into "low" and "high" expressors. "High" VCAM-1 expressors had higher CD34+in peripheral blood as well as higher CD34+numbers collected during first apheresis than "low" expressors. In conclusion, the levels of niche cytokines change significantly during mobilization in patients with hematopoietic malignancies. Baseline VEGF can influence timing of mobilization. Higher VCAM-1 corresponds with higher mobilization efficacy.

Angiopoietins in haematopoietic stem cell mobilisation in patients with haematological malignancies

BACKGROUND

The bone marrow niche contains different types of cells including osteoblasts and endothelial progenitors, all of which interact and take part in the process of mobilisation. The aim of our study was to evaluate the levels of cytokines (osteopontin and angiopoietins 1 and 2) active in the bone marrow niche during the mobilisation of haematopoietic stem cells for autologous transplantation.

MATERIALS AND METHODS

Forty-eight patients (24 females, 24 males), median age 56.5 years, entered the study. The group consisted of patients with multiple myeloma (n=34), lymphoma (n=13) and acute myeloid leukaemia (n=1). Blood samples were collected before chemotherapy and on the day of the first apheresis. Cytokines were evaluated by enzyme-linked immunosorbent assays. Additionally, circulating endothelial cells were assessed by flow cytometry.

RESULTS

The median concentration of angiopoietin 1 at the time of apheresis was lower than that at baseline (2.7 vs 7.8 ng/mL, p<0.001). In contrast, the median level of angiopoietin 2 increased during the mobilisation procedure (3.6 vs 2.8 ng/mL, p=0.001). The patients were divided according to the number of days of granulocyte colony-stimulating factor treatment before the first apheresis into "early" (<median=11 days) and "late" (>median) mobilisers. The group of "early mobilisers" had higher baseline angiopoietin 1 levels (median=11.6 ng/mL) than those of the "late mobilisers" (median=6.0 ng/mL, p=0.05). An adverse correlation was observed between duration of granulocyte colony-stimulating factor treatment and baseline angiopoietin 1 level. Baseline angiopoietin 1 levels correlated with numbers of circulating endothelial cells. Low angiopoietin 2 level increased the chance of poor mobilisation.

CONCLUSIONS

The angiogenic processes can influence the timing of mobilisation. Angiopoietins 1 and 2 need further evaluation in the context of mobilisation.