Regulating dynamic signaling between hematopoietic stem cells and niche cells via a hydrogel matrix

Abstract

Hematopoietic stem cells (HSC) reside in unique bone marrow niches and are influenced by signals from surrounding cells, the extracellular matrix (ECM), ECM-bound or diffusible biomolecules. Here we describe the use of a three-dimensional hydrogel to alter the balance of HSC-generated autocrine feedback and paracrine signals generated by co-cultured niche-associated cells. We report shifts in HSC proliferation rate and fate specification in the presence of lineage positive (Lin+) niche cells. Hydrogels promoting autocrine feedback enhanced expansion of early hematopoietic progenitors while paracrine signals from Lin+ cells increased myeloid differentiation. We report thresholds where autocrine vs. paracrine cues alter HSC fate transitions, and were able to selectively abrogate the effects of matrix diffusivity and niche cell co-culture via the use of inhibitory cocktails of autocrine or paracrine signals. Together, these results suggest diffusive biotransport in three-dimensional biomaterials are a critical design element for the development of a synthetic stem cell niche.

Mesenchymal stromal cell remodeling of a gelatin hydrogel microenvironment defines an artificial hematopoietic stem cell niche

“…Notably, while paracrine signals from Lin + cells induce HSC myeloid differentiation in high-diffusivity environments, diffusion-limited hydrogel environments promoted autocrine feedback and HSC maintenance [29].…”

“…27, 2018; displayed two subsets of diffusion and mesh size. Notably, based on previous result from Mahadik et al [29] the poor diffusivity of the High hydrogel suggests an autocrine-dominated regime for HSC culture characterized by a small radius of cell-secreted chemical diffusion [92].…”

“…Primary murine Hematopoietic stem progenitor cells (HSPC) were extracted from the femur and tibia bone marrow of C57BL/6 female mice, age 4 -8 weeks (Jackson Labs). The bones were gently crushed with pestle and mortar, and washed with PBS + 5%FBS prior to filtration with a 40µm sterile filter [29,46]. The collected suspension was lysed with ACK lysis buffer (Invitrogen, Carlsbad, CA), and then rinsed with PBS/FBS.…”

“…The LSK faction was collect in PBS + 25% FBS on ice and immediately used [19,29,46,[67][68][69][70].…”

“…Replicating aspects of this concept in a three-dimensional collagen hydrogel system, we recently showed the ability to maintain early progenitor HSC populations in autocrine-dominated environments with low diffusivity [29].…”