Distinct Stromal Cell Factor Combinations Can Separately Control Hematopoietic Stem Cell Survival, Proliferation, and Self-Renewal

Abstract

SummaryHematopoietic stem cells (HSCs) are identified by their ability to sustain prolonged blood cell production in vivo, although recent evidence suggests that durable self-renewal (DSR) is shared by HSC subtypes with distinct self-perpetuating differentiation programs. Net expansions of DSR-HSCs occur in vivo, but molecularly defined conditions that support similar responses in vitro are lacking. We hypothesized that this might require a combination of factors that differentially promote HSC viability, proliferation, and self-renewal. We now demonstrate that HSC survival and maintenance of DSR potential are variably supported by different Steel factor (SF)-containing cocktails with similar HSC-mitogenic activities. In addition, stromal cells produce other factors, including nerve growth factor and collagen 1, that can antagonize the apoptosis of initially quiescent adult HSCs and, in combination with SF and interleukin-11, produce >15-fold net expansions of DSR-HSCs ex vivo within 7 days. These findings point to the molecular basis of HSC control and expansion.

Hematopoietic stem cells: concepts, definitions, and the new reality

“…on May 10, 2018. by guest www.bloodjournal.org From exploitation of this latter approach has now provided conclusive robust evidence that LTRC self-renewal, mitogenesis, and survival can be independently regulated ( Figure 3B). 65 Nevertheless, the large (.500-fold) variations in self-renewal of individual LTRCs seen in vivo when these are tracked clonally and measured through at least 2 serial transplants support the operation of an underlying stochastic process. 44,66 On the other hand, analysis of clones produced from the first division progeny of stringently defined LTRCs have shown both variable (in vitro) 65,67 and more restricted (in vivo) 66 patterns of self-renewal behavior in paired daughter cells.…”

“…65 Nevertheless, the large (.500-fold) variations in self-renewal of individual LTRCs seen in vivo when these are tracked clonally and measured through at least 2 serial transplants support the operation of an underlying stochastic process. 44,66 On the other hand, analysis of clones produced from the first division progeny of stringently defined LTRCs have shown both variable (in vitro) 65,67 and more restricted (in vivo) 66 patterns of self-renewal behavior in paired daughter cells. The latter findings suggest LTRC self-renewal responses to external stimuli may reflect variable cell-intrinsic elements that can be sustained through multiple cell generations.…”

“…However, these markers have proven to be more discriminatory for LTRCs with durable activity than for LTRCs with a particular lineage output profile. It is also important to note that some secondary clones generated from serial transplants of single cells, 44 or from paired daughter cells obtained from purified LTRCs stimulated to divide in vitro, 65,67,93 have not shown convincing evidence of a preserved differentiation profile. Likewise, the distribution of LTRCs categorized according to the different lineage options they display has been found to change during development and aging 33,44,102 and be subject to extrinsic modulation.…”

A Lentiviral Fluorescent Genetic Barcoding System for Flow Cytometry-Based Multiplex Tracking

“…Since functional assays to assess HSC properties; e.g., characterization of new HSC markers, cytokine conditions for in vitro cultivation, or estimation of HSC numbers, furthermore rely on in vivo transplantation and subsequent detection of hematopoietic reconstitution for more than 4 months, 21,22 these assays typically require transplantation of many conditioned mice to generate reliable data sets and lack the opportunity to compete cells from different conditions in the same animal. To overcome these limitations, we opted to assess 3G-FGB-BC vector performance in ESLAM HSCs.…”

Niche Wnt5a regulates the actin cytoskeleton during regeneration of hematopoietic stem cells

“…This confirmed the migratory defects of hematopoietic cells regenerated in Wnt5a +/− recipients in vivo. To determine whether the remaining LSK-5a cells that do home to the marrow fail to engraft as a result of decreased cell division or reduced survival, we set up single-cell cultures (Wohrer et al, 2014;Istvánffy et al, 2015). These showed that cell division and survival of CD34 -LSK-5a cells were similar to CD34…”