Identification of the haematopoietic stem cell niche and control of the niche size

Abstract

run in TBE £0.5 at room temperature for 2 h at 150 V. The following two (Q/q) 27-bp unmethylated oligonucleotides were used: 5 0 -GATCCTTCGCCTAGGCTC(A/G)CAGCG CGGGAGCGA-3 0 . A methylated q probe (q*) was generated by incorporating a methylated cytosine at the mutated CpG site during oligonucleotide synthesis. Transient transfection assayThe constructs contained 578 bp from IGF2 intron 3 (nucleotides 2868-3446), followed by the IGF2 P3 promoter (nucleotides 2222 to þ45 relative to the start of transcription) 12 and a luciferase reporter. C2C12 myoblast cells were grown to approximately 80% confluence. Cells were transiently co-transfected with the firefly luciferase reporter construct (4 mg) and a Renilla luciferase control vector (phRG-TK, Promega; 80 ng) using 10 mg Lipofectamine 2000 (Invitrogen). Cells were incubated for 25 h before lysis in 100 ml Triton lysis solution. Luciferase activities were measured using the Dual-Luciferase Reporter Assay System (Promega). The results are based on four triplicate experiments using two independent plasmid preparations for each construct. Statistical analysis was done with an analysis of variance.

Osteopontin attenuates aging‐associated phenotypes of hematopoietic stem cells

“…While mechanisms through which the niche regulates young HSCs have started to be elucidated (Visnjic et al , 2004; Xie et al , 2009; Méndez‐Ferrer et al , 2010; Nombela‐Arrieta et al , 2013; Bruns et al , 2014; Acar et al , 2015; Gur‐Cohen et al , 2015), data on the extent of aging of the niche and the contribution to aging of HSCs are rare. Changes in the niche composition or function upon aging involve decreased bone formation, enhanced adipogenesis and changes in extracellular matrix (ECM) components (Calvi et al , 2003; Zhang et al , 2003; Naveiras et al , 2009; Geiger et al , 2013). Skewing of aged HSCs toward myeloid differentiation was recently linked to increased secretion of the pro‐inflammatory CC‐chemokine ligand 5 (CCL5; also known as RANTES) in aged stroma (Ergen et al , 2012).…”

The BRG1 ATPase of chromatin remodeling complexes is involved in modulation of mesenchymal stem cell senescence through RB–P53 pathways

“…Among these are MSCs, which are nonhematopoietic stem cells possessing multilineage potential (Muller-Sieburg and Deryugina, 1995;Zhang et al, 2003). MSCs are of interest because of the multiple roles they perform.…”

BMP et cancer

“…L'inhibition conditionnelle de BMPRIa induit l'expansion des CS et des progéniteurs intestinaux, ce qui confirme le rôle de la signalisation en aval de ce récepteur dans le maintien de CS indifférenciées [6]. L'inhibition de la voie BMP chez des souris transgéniques exprimant noggin induit la formation ectopique de la famille BMP sur le compartiment des CSH via l'environnement : chez ces souris, l'augmentation du nombre d'ostéoblastes dans la moelle des souris BMPRIa -/-conduit à une expansion significative des CSH transplantées dans ces animaux [14]. Cette étude démontre de façon remarquable que les molécules de la famille BMP contrôlent la taille de la niche hématopoïétique par l'intermédiaire des ostéoblastes, support direct des propriétés des CSH.…”

“…Les cellules de la gaine dermique sécrètent l'inhibiteur noggin tandis que les cellules de la papille dermique synthétisent des BMP dont BMP4. Un gradient d'activité BMP est ainsi formé : concentration faible de BMP à la base du follicule où [14]. L'équilibre entre ces différents paramètres permet une régulation fine de la biologie des CS au sein de leur microenvironnement.…”