Stimulation of Adult Human Bone Marrow by Factors Secreted by Fetal Liver Hematopoietic Cells: In Vitro Evaluation Using Semisolid Clonal Assay System

Abstract

Fetal liver infusion (FLI) therapy has been used in various disorders, such as aplastic anemia, leukemia, metabolic disorders, etc., and has been shown to result in stimulation of autologous hematopoiesis in many cases. The aim of the present study was to elucidate the mechanism of stimulation of adult hematopoiesis by fetal liver hematopoietic cells (FLHC) and to identify the factors involved in the process using a clonal assay system in vitro. The effect of FLHC on the clonal growth of bone marrow cells was studied using a co-culture system consisting of mitomycin C-treated FLHC with 2 × 10 5 bone marrow (BM) mononuclear cells. It was observed that FLHC induced a two-to four-fold increase in the BM colony formation. A further increase in the number of FLHC did not, however, result in an equivalent fold increase in the colony formation, indicating that the number of cells in the BM population responsive to FLHC was perhaps the limiting factor. When the effect of fetal liver cell conditioned medium (FLCM) was examined in a similar fashion, it was observed that the FLCM showed a 1.5-to 4-fold increase in the colony formation when used at 1%-5% along with limiting amounts of growth factors. Higher concentrations of conditioned medium resulted in inhibitory responses. One of the principal factors responsible for the stimulatory activity of FLCM was shown to be transforming growth factor-β1 (TGF-β1), by a variety of experiments such as its quantitation in FLCM by enzyme-linked immunosorbent assay, antibody neutralization, and reconstruction experiments using purified TGF-β1 and normal medium. In these reconstitution experiments, TGF-β1 stimulated the colony formation when it was applied at 1-50 pg/ml, but at higher concentration it induced an inhibitory effect, mimicking the behavior earlier seen with FLCM. Our data strongly suggest that one of the mechanisms in stimulation of a recipient's hematopoiesis could be mediated by the action of TGF-β1 secreted by infused FLHC and could provide a rational framework on which FLI therapy can be further evaluated.

Cell cycle status of CD34+ cells in human fetal bone marrow

“…The mechanism(s) responsible for the higher cycling rates that we observed in CD34+ cells from fetal marrow compared with those of adult marrow are unclear. These differences might reflect properties unique to the fetal hematopoietic microenvironment [11], such as a differing proportion of stimulatory factors [12] or hematopoietic inhibitors [13]. Alternatively, fetal progenitors might possess cell cycle characteristics that are intrinsically different from those of their adult counterparts [14].…”

Transforming growth factor β1 accelerates and enhances in vitro red blood cell formation from hematopoietic stem cells by stimulating mitophagy

“…Firstly, in these studies, nanogram concentrations of TGF-β1 have been used; secondly, the effect is either studied on a cell line or on erythroid progenitors; thirdly, our protocol is distinct from the reported ones; The effect of TGF-β1 on cell proliferation and differentiation depends on its concentration and the cell type used. Earlier, it was reported that TGF-β1 at low concentration (10-20 pg/ml) significantly stimulated colony formation from HSCs, indicating that these progenitors are the direct target of stimulatory action of TGF-β1, whereas at high TGF-β1 concentration (5-10 ng/ml) it inhibited colony formation [16,17,38]. Here, we show, for the first time, that low concentration of TGF-β1 is more effective on erythroid differentiation of HSCs.…”

Transforming growth factor‐β boosts the functionality of human bone marrow‐derived mesenchymal stromal cells

“…Wang, Dong, et al, 2018). However, a consistent association of TGFβ1 with the hematopoietically active sites such as bone marrow niche, second trimester foetal liver and the hematopoietic islands of the yolk sac (Kale & Limaye, 1999;Schmid, Cox, Bilbe, Maier, & McMaster, 1991) point towards a possibility that perhaps it could have an as yet unidentified positive regulatory role in hematopoiesis.…”