Daniela Giovanna De Ritis

Semiquantitative RT-PCR analysis to assess the expression levels of multiple transcripts from the same sample

We describe a semiquantitative RT-PCR protocol optimized in our laboratory to extract RNA from as little as 10,000 cells and to measure the expression levels of several target mRNAs from each sample. This procedure was optimized on the human erythroleukemia cell line TF-1 but was successfully used on primary cells and on different cell lines. We describe the detailed procedure for the analysis of Bcl-2 levels. Aldolase A was used as an internal control to normalize for sample to sample variations in total RNA amounts and for reaction efficiency. As for all quantitative techniques, great care must be taken in all optimization steps: the necessary controls to ensure a rough quantitative (semi-quantitative) analysis are described here, together with an example from a study on the effects of TGF-β1 in TF-1 cells.

Granulocyte colony‐stimulating factor promotes the generation of regulatory DC through induction of IL‐10 and IFN‐α

We have recently demonstrated that G‐CSF promotes the generation of human T regulatory (TREG) type 1 cells. In this study, we investigated whether the immunomodulatory effects of G‐CSF might be mediated by DC. CD14+ monocytes were cultured with serum collected after clinical administration of G‐CSF (post‐G), which contained high amounts of IL‐10 and IFN‐α. Similar to incompletely matured DC, monocytes nurtured with post‐G serum acquired a DC‐like morphology, expressed high levels of costimulatory molecules and HLA‐DR, and exhibited diminished IL‐12p70 release and poor allostimulatory capacity. Importantly, post‐G DC‐like cells were insensitive to maturation stimuli. As shown by neutralization studies, IFN‐α and, even more pronounced, IL‐10 contained in post‐G serum inhibited IL‐12p70 release by post‐G DC‐like cells. Furthermore, phenotypic and functional features of post‐G DC‐like cells were replicated by culturing post‐G monocytes with exogenous IL‐10 and IFN‐α. Post‐G DC‐like cells promoted Ag‐specific hyporesponsiveness in naive allogeneic CD4+ T cells and orchestrated a TREG response that was dependent on secreted TGFβ1 and IL‐10. Finally, neutralization of IL‐10 and IFN‐α contained in post‐G serum translated into abrogation of the regulatory features of post‐G DC‐like cells. This novel mechanism of immune regulation effected by G‐CSF might be therapeutically exploited for tolerance induction in autoimmune disorders.

Clinical isolation and functional characterization of cord blood CD133+ hematopoietic progenitor cells

BACKGROUND:  Human cord blood is a relevant source of CD133+ HPCs. Clinical‐scale isolation of human umbi‐lical cord blood (UCB) CD133+ HPCs using immunomag‐netic microbeads and the CliniMACS clinical cell isolator is reported. CD133+ HPCs isolated after large‐scale pro‐cessing were functionally characterized.

Identification of a Novel Subpopulation of Human Cord Blood CD34−CD133−CD7−CD45+Lineage− Cells Capable of Lymphoid/NK Cell Differentiation After In Vitro Exposure to IL-15

The hemopoietic stem cell (HSC) compartment encompasses cell subsets with heterogeneous proliferative and developmental potential. Numerous CD34− cell subsets that might reside at an earlier stage of differentiation than CD34+ HSCs have been described and characterized within human umbilical cord blood (UCB). We identified a novel subpopulation of CD34−CD133−CD7−CD45dimlineage (lin)− HSCs contained within human UCB that were endowed with low but measurable extended long-term culture-initiating cell activity. Exposure of CD34−CD133−CD7−CD45dimlin− HSCs to stem cell factor preserved cell viability and was associated with the following: 1) concordant expression of the stem cell-associated Ags CD34 and CD133, 2) generation of CFU-granulocyte-macrophage, burst-forming unit erythroid, and megakaryocytic aggregates, 3) significant extended long-term culture-initiating cell activity, and 4) up-regulation of mRNA signals for myeloperoxidase. At variance with CD34+lin− cells, CD34−CD133−CD7−CD45dimlin− HSCs maintained with IL-15, but not with IL-2 or IL-7, proliferated vigorously and differentiated into a homogeneous population of CD7+CD45brightCD25+CD44+ lymphoid progenitors with high expression of the T cell-associated transcription factor GATA-3. Although they harbored nonclonally rearranged TCRγ genes, IL-15-primed CD34−CD133−CD7−CD45dimlin− HSCs failed to achieve full maturation, as manifested in their CD3−TCRαβ−γδ− phenotype. Conversely, culture on stromal cells supplemented with IL-15 was associated with the acquisition of phenotypic and functional features of NK cells. Collectively, CD34−CD133−CD7−CD45dimlin− HSCs from human UCB displayed an exquisite sensitivity to IL-15 and differentiated into lymphoid/NK cells. Whether the transplantation of CD34−lin− HSCs possessing T/NK cell differentiation potential may impact on immunological reconstitution and control of minimal residual disease after HSC transplantation for autoimmune or malignant diseases remains to be determined.

Transforming growth factor-beta1 causes transcriptional activation of CD34 and preserves haematopoietic stem/progenitor cell activity.

Summary. Stem/progenitor cells endowed with in vitro and in vivo haematopoietic activity express the surface protein CD34. Transforming growth factor β1 (TGF‐β1) is one of the soluble molecules that regulate cell cycle and differentiation of haematopoietic cells, but has pleiotropic activities depending on the state of responsiveness of the target cells. It has previously been shown that TGF‐β1 maintains human CD34+ haematopoietic progenitors in an undifferentiated state, independently of any cell cycle effect. Here, we have shown that TGF‐β1 upregulates the human CD34, an effect that was evident in primary stem/progenitor cells (CD34+lin–) both at the transcriptional and protein levels, and was not associated with any relevant effect on cell growth. The presence of TGF‐β1 influenced differentiation, maintaining primary CD34+/Lin– in an undifferentiated state. This effect was associated with Smad activation and with a dramatic decrease in p38 phosphorylation. Moreover, blocking p38 phosphorylation by the SB202190 inhibitor increased CD34 RNA levels but did not enhance CD34 protein expression in CD34+/Lin– cells, suggesting that modulation of multiple signalling pathways is necessary to reproduce TGF‐β1 effects. These data establish the role that TGF‐β1 has in the modulation of the CD34 stem/progenitor protein and stem/progenitor functions, providing important clues for understanding haematopoietic development and a potential tool for the modulation of human haematopoiesis.

Cell Cycle Regulation in Human Hematopoietic Stem Cells: From Isolation to Activation

Hematopoietic stem cells (HSCs) reside mostly in the bone marrow and are defined by their ability to self-renew and to give rise by proliferation and differentiation to all blood lineages. Despite this strict definition HSCs cannot be unequivocally identified in the hematopoietic cell pool. Despite innumerable studies over the years, which focused on the search of the ideal phenotypic marker to selectively isolate stem cells, most of the known markers still define heterogeneous populations in different stages of commitment. Functional features attributed to stem cells have also been investigated, and among these the use of fluorescent markers which allow tracking of the cell division record of each cell. A second issue, after the initial isolation process, is the expansion ex vivo in order to obtain production of large numbers of homogeneous cell populations for both biological studies and clinical applications. Expansion ex vivo is difficult to modulate and normally occurs only along with commitment and consequent loss of multipotentiality. Moreover expansion obtained ex vivo is significantly reduced to that achievable in vivo. One of the key features of HSCs is a very slow proliferation rate, but when the appropriate stimuli are delivered, the proliferation rate can drastically increase. In normal physiological conditions a strict balance is maintained between the number of cells that maintain the original pool and those that proliferate and differentiate. Numerous data in recent years are providing some clue to elucidate the key steps in this tightly controlled process, but the dynamics that regulate which and how many cells self-renew to maintain the pool, and which proliferate and become committed to give rise to the mature blood elements, are still unclear.

Changes in protein serum levels during stem cell transplantation

GvHD is one of the major complication after stem cell transplantation affecting transplant‐related mortality. Throughout the last years, many serum proteins were been proposed as possible biomarkers for GvHD.

Fecal but not serum calprotectin is a potential marker of GVHD after stem cell transplantation

Gastrointestinal graft-versus-host disease (GvHD) represents a life-threatening complication after stem cell transplantation. Differential diagnosis between gut GvHD and other causes of diarrhea after HSCT is still subjected to endoscopy and histological findings. The research for a reliable biomarker for gut GvHD might allow an early diagnosis of this condition and a consequent prompt treatment that could reduce unfavorable outcomes. Recently, fecal calprotectin was reported as reliable marker of gut involvement. We would evaluate if serum instead of fecal calprotectin could be considered a possible biomarker of gut GvHD. Serum calprotectin was measured in a cohort of 54 patients submitted to allogeneic stem cell transplantation using ELISA assay. For a subset of 21 patients, calprotectin serum levels were compared with fecal calprotectin detection. Contrary to fecal calprotectin, we found only a trend to high level of serum calprotectin for GvHD development and gut involvement, but statistical difference was not reached. Fecal but not serum calprotectin could be considered as possible biomarker for gut GvHD.