Primary human CD34+ hematopoietic stem and progenitor cells express functionally active receptors of neuromediators

Abstract

Recently, overlapping molecular phenotypes of hematopoietic and neuropoietic cells were described in mice. Here, we examined primary human CD34 ؉ hematopoietic stem and progenitor cells applying specialized cDNA arrays, real-time reverse-transcriptase-polymerase chain reaction (RT-PCR), and fluorescent-activated cell sorter (FACS) analysis focusing on genes involved in neurobiologic functions. We found expression of vesicle fusion and motility genes, ligand-and voltage-gated ion channels, receptor kinases and phosphatases, and, most interestingly, mRNA as well as protein expression of G protein-coupled receptors of neuromediators (corticotropin-releasing hormone 1 [CRH 1] and CRH 2 receptors, orexin/ hypocretin 1 and 2 receptors, GABA B receptor, adenosine A 2 B receptor, opioid 1 and 1 receptors, and 5-HT 1F receptor). As shown by 2-color immunofluorescence, the protein expression of these receptors was higher in the more immature CD38 dim than in the CD38 bright subset within the CD34 ؉ population, and completely absent in fully differentiated blood cells, suggesting that those receptors play a role in developmentally early CD34 ؉ stem and progenitor cells. IntroductionHuman CD34 ϩ hematopoietic stem and progenitor cells ensure lifelong production of mature blood cells according to the varying needs of the individual. Hematopoiesis is a precisely regulated process based upon a balance of self-renewal and commitment to differentiation along the different hematopoietic lineages. The restorative capacity of human CD34 ϩ cells is clinically used in the autologous and allogeneic transplantation setting to reconstitute hematopoiesis following cytotoxic therapy for the treatment of patients with malignant or autoimmune diseases. [1][2][3] Beyond that, data of recent studies suggest that hematopoietic progenitors might also be able to transdifferentiate into nonhematopoietic cells, which could open novel therapeutic avenues in the treatment of diseases such as myocardial or cerebral infarction as well as other degenerative disorders. [4][5][6][7] However, novel data have challenged the transdifferentiation model by suggesting cell fusion rather than plasticity of stem cells. [8][9][10] A better molecular understanding of the signal perception pathways of hematopoietic stem and progenitor cells seems to be required to understand the conditions under which transdifferentiation of hematopoietic cells may occur. 11 Studies in animal models showed the presence of sensory and autonomic nerves in the bone marrow as a morphologic correlate of a possible neural regulation of hematopoiesis. [12][13][14] However, the idea that neuromediators might directly influence hematopoietic progenitors is controversially discussed. [15][16][17][18][19] Recently, several investigators described partly overlapping genetic programs of hematopoietic and neuropoietic cells in mice. 20,21 Those findings prompted us to examine human hematopoietic cells by means of specialized cDNA arrays, quantitative real-time reversetranscription-polymerase ch...

Epigenetics and the plasticity of differentiation in normal and cancer stem cells

“…Results with hematopoietic stem cells and CD34 positive hematopoietic progenitors have shown, that these cells express genes that are expressed in neural and various other normal nonhematopoietic tissues (Luce and Burrows, 1999;Akashi et al, 2003;Goolsby et al, 2003;Georgantas et al, 2004;Steidl et al, 2004). Skeletal muscle stem cells express neural stem cell genes and adult bone marrow-derived mesenchymal stem cells express different mesenchymal genes as well as genes of various other lineages including neuronal, testis, liver, lung, hematopoietic and endothelial tissues (Woodbury et al, 2002;Seshi et al, 2003).…”

Distinct molecular phenotype of malignant CD34+ hematopoietic stem and progenitor cells in chronic myelogenous leukemia

“…Recently, we have shown that genes primarily expressed in the nervous system may also be expressed in normal human CD34 þ cells (Steidl et al, 2004). This finding prompted us to examine our CML CD34 þ cells with regard to the expression of genes involved in neurobiological functions.…”

“…Since we have previously shown that the expression of those receptors on normal CD34 þ cells depends on the coexpression of CD38 (Steidl et al, 2004), we assessed the proportions of CD34 þ cells with low or high CD38 expression. Comparing CML CD34 þ cells with normal CD34 þ cells, we found a similar proportion of CD38 low expressing cells in both groups (4.26% (mean) vs 4.33% (mean)), indicating that differential expression of G protein-coupled receptors is not the result of a different composition of the CD34 þ cell population with regard to maturation state.…”

“…Analysis of CD38 coexpression and detection of opioid m1 and k1 receptors, GABA B receptor, serotonin (5-HT) 1F receptor, adenosine A1 and A2B receptors, CRH receptor, and orexin receptors 1 and 2 by indirect immunofluorescence was performed as described (Steidl et al, 2004).…”

Adult human hematopoietic stem cells produce neurons efficiently in the regenerating chicken embryo spinal cord

“…Several reports indicate an overlap in the molecular programs for hematopoiesis and neuropoiesis in mice (14,15). Another report has shown that primary CD34ϩ hHSCs express mRNA for a number of proteins that are used by (among other cell types) neurons, including receptors for trophic factors and other mediators that are known to influence the development of neurons (16). Commonalities in the expression profiles of neural and HSCs provide molecular opportunities for across-tissue differentiation, but it remains to be seen how well these can be used in the organism or exploited in the clinic.…”