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Perivascular Secretome Influences Hematopoietic Stem Cell Maintenance in a Gelatin Hydrogel.

ABSTRACT: Adult hematopoietic stem cells (HSCs) produce the body's full complement of blood and immune cells. They reside in specialized microenvironments, or niches, within the bone marrow. The perivascular niche near blood vessels is believed to help maintain primitive HSCs in an undifferentiated state but demonstration of this effect is difficult. In vivo studies make it challenging to determine the direct effect of the endosteal and perivascular niches as they can be in close proximity, and two-dimensional in vitro cultures often lack an instructive extracellular matrix environment. We describe a tissue engineering approach to develop and characterize a three-dimensional perivascular tissue model to investigate the influence of the perivascular secretome on HSC behavior. We generate 3D endothelial networks in methacrylamide-functionalized gelatin hydrogels using human umbilical vein endothelial cells (HUVECs) and mesenchymal stromal cells (MSCs). We identify a subset of secreted factors important for HSC function, and examine the response of primary murine HSCs in hydrogels to the perivascular secretome. Within 4 days of culture, perivascular conditioned media promoted maintenance of a greater fraction of hematopoietic stem and progenitor cells. This work represents an important first-generation perivascular model to investigate the role of niche secreted factors on the maintenance of primary HSCs.

SUBMITTER: Barnhouse V

PROVIDER: S-EPMC7854499 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The objective of this study was to develop an injectable and biocompatible hydrogel that can deliver a cocktail of therapeutic biomolecules (secretome) secreted by human adipose-derived stem cells (hASCs) to the peri-infarct myocardium. Gelatin and Laponite® were combined to formulate a shear-thinning, nanocomposite hydrogel (nSi Gel) as an injectable carrier of secretome (nSi Gel+). The growth factor composition and the pro-angiogenic activity of the secretome were tested in vitro by evaluating the proliferation, migration and tube formation of human umbilical endothelial cells. The therapeutic efficacy of the nSi Gel?+?system was then investigated in vivo in rats by intramyocardial injection into the peri-infarct region. Subsequently, the inflammatory response, angiogenesis, scar formation, and heart function were assessed. Biocompatibility of the developed nSi Gel was confirmed by quantitative PCR and immunohistochemical tests which showed no significant differences in the level of inflammatory genes, microRNAs, and cell marker expression compared to the untreated control group. In addition, the only group that showed a significant increase in capillary density, reduction in scar area and improved cardiac function was treated with the nSi Gel+. Our in vitro and in vivo findings demonstrate the potential of this new secretome-loaded hydrogel as an alternative strategy to treat myocardial infarction. STATEMENT OF SIGNIFICANCE:Stem cell based-therapies represent a possible solution to repair damaged myocardial tissue by promoting cardioprotection, angiogenesis, and reduced fibrosis. However, recent evidence indicates that most of the positive outcomes are likely due to the release of paracrine factors (cytokines, growth factors, and exosomes) from the cells and not because of the local engraftment of stem cells. This cocktail of essential growth factors and paracrine signals is known as secretome can be isolated in vitro, and the biomolecule composition can be controlled by varying stem-cell culture conditions. Here, we propose a straightforward strategy to deliver secretome produced from hASCs by using a nanocomposite injectable hydrogel made of gelatin and Laponite®. The designed secretome-loaded hydrogel represents a promising alternative to traditional stem cell therapy for the treatment of acute myocardial infarction.

Project description:Glioblastoma (GBM) is the most common primary malignant brain tumor, with patients exhibiting poor survival (median survival time: 15 months). Difficulties in treating GBM include not only the inability to resect the diffusively-invading tumor cells but also therapeutic resistance. The perivascular niche within the GBM tumor microenvironment contributes significantly to tumor cell invasion, cancer stem cell maintenance, and has been shown to protect tumor cells from radiation and chemotherapy. In this study, we describe the development of an in vitro artificial perivascular niche (PVN), culturing endothelial and stromal cells along with GBM cells within a methacrylamide-functionalized gelatin hydrogel, in order to examine how the presence of the PVN alters global genomic expression profiles. Using RNA-seq, we demonstrate that the inclusion of perivascular niche cells with GBM cells upregulates genes related to angiogenesis and remodeling, while downregulated genes are related to cell cycle and DNA damage repair. Signaling pathways and genes commonly implicated in GBM malignancy, such as MGMT, EGFR, PI3K-Akt signaling, and Ras/MAPK signaling are also upregulated in the presence of perivascular niche cells. We describe the kinetics of gene expression within the PVN hydrogels over a course of 14 days, observing the patterns associated with previously-observed GBM-mediated endothelial network co-option and regression that are altered in the presence of covalently-bound hyaluronic acid. We finally examine the effect of PVN culture on GBM cell responsiveness to temozolomide, a frontline chemotherapy used clinically against GBM. Notably, the presence of a PVN leads to significantly increased TMZ resistance compared to hydrogels containing only GBM cells. Overall, these results demonstrate that inclusion of cellular and matrix-associated elements of the PVN within in vitro models of GBM provide critical signals to regulate the phenotype and therapeutic responsiveness of GBM cells.

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Perivascular Secretome Influences Hematopoietic Stem Cell Maintenance in a Gelatin Hydrogel.

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