Macromolecular crowding for tailoring tissue-derived fibrillated matrices.

Unlabelled: Tissue-derived fibrillated matrices can be instrumental for the in vitro reconstitution of multiphasic extracellular microenvironments. However, despite of several advantages, the obtained scaffolds so far offer a rather narrow range of materials characteristics only. In this work, we demonstrate how macromolecular crowding (MMC) - the supplementation of matrix reconstitution media with synthetic or natural macromolecules in ways to create excluded volume effects (EVE) - can be employed for tailoring important structural and biophysical characteristics of kidney-derived fibrillated matrices.

Macroporous biohybrid cryogels for co-housing pancreatic islets with mesenchymal stromal cells.

Unlabelled: Intrahepatic transplantation of allogeneic pancreatic islets offers a promising therapy for type 1 diabetes. However, long-term insulin independency is often not achieved due to severe islet loss shortly after transplantation. To improve islet survival and function, extrahepatic biomaterial-assisted transplantation of pancreatic islets to alternative sites has been suggested.

Cell survival signaling in the bovine mammary gland during the transition from lactation to involution.

In dairy cows, mammary gland involution, and thus a decline in milk production, occurs following peak lactation. To examine the cell signaling pathways regulating involution of the mammary gland, signal transducer and activator of transcription factors (STAT5 and 3), suppressors of cytokine signaling (SOCS1-3 and CIS), insulin-like growth factors (IGF1 and 2), and protein kinase B (Akt) were examined. Mammary involution was induced by termination of milking, and alveolar tissue was collected from 52 nonpregnant, primiparous, mid-lactation Holstein-Friesian cows killed at 0, 6, 12, 18, 24, 36, 72, and 192h postmilking.

Extracellular matrix deposition of bone marrow stroma enhanced by macromolecular crowding.

Decellularized extracellular matrices (ECM) from in vitro cell cultures can serve as in vivo-like matrix scaffolds for modulating cell-ECM interactions. Macromolecular crowding (MMC), the supplementation of synthetic or naturally occurring molecules resulting in excluded volume effects (EVE), has been demonstrated to provide valuable options for recapitulating the physiological environment of cells during matrix secretion. Human mesenchymal stem cell (MSC)-derived ECM was produced upon supplementation of standard culture medium with three different macromolecules of various size (10-500 kDa).

Availability of extracellular matrix biopolymers and differentiation state of human mesenchymal stem cells determine tissue-like growth in vitro.

To explore the space-filling growth of adherent mesenchymal stem cells (MSC) into tissue-like structures in vitro, human bone marrow derived MSC were exposed to fibronectin-coated, millimeter-sized, triangular channels casted in poly(dimethyl siloxane) carriers. The results revealed that the three dimensional (3D) growth of MSC differs in dependence on differentiation status and availability of extracellular matrix (ECM) proteins: Massive 3D structure formation was observed for MSC under pro-osteogenic stimulation but not for undifferentiated MSC nor for MSC under pro-adipogenic stimulation; boosting cellular matrix secretion and addition of soluble ECM proteins caused extensive 3D tissue formation of undifferentiated MSC. The reported findings may contribute to bridge the gap between in vitro and in vivo analyses and guide the application of MSC in tissue replacement approaches.

The self-renewal of mouse embryonic stem cells is regulated by cell-substratum adhesion and cell spreading.

Mouse embryonic stem cells (mESCs) undergo self-renewal in the presence of the cytokine, leukaemia inhibitory factor (LIF). Following LIF withdrawal, mESCs differentiate, and this is accompanied by an increase in cell-substratum adhesion and cell spreading. The purpose of this study was to investigate the relationship between cell spreading and mESC differentiation.

Tightly anchored tissue-mimetic matrices as instructive stem cell microenvironments.

A major obstacle in defining the exact role of extracellular matrix (ECM) in stem cell niches is the lack of suitable in vitro methods that recapitulate complex ECM microenvironments. Here we describe a methodology that permits reliable anchorage of native cell-secreted ECM to culture carriers. We validated our approach by fabricating two types of human bone marrow-specific ECM substrates that were robust enough to support human mesenchymal stem cells (MSCs) and hematopoietic stem and progenitor cells in vitro.

Dewaxed ECM: A simple method for analyzing cell behaviour on decellularized extracellular matrices.

Decellularization techniques have been used on a wide variety of tissues to create cell-seedable scaffolds for tissue engineering. Finding a suitable decellularization protocol for a certain type of tissue can be laborious, especially when organ perfusion devices are needed. In this study, we report a quick and simple method for comparing decellularization protocols combining the use of paraffin slices and two-dimensional cell cultures.

Polymeric biomaterials for stem cell bioengineering.

This review covers the application of polymeric materials in stem cell bioengineering. Main emphasis is directed towards current material design concepts that mimic distinct exogenous signals of the stem cell microenvironment. Progress within the field of stem cell-specific biomaterials will be discussed, focusing on pluripotent, hematopoietic, mesenchymal and neural stem cells.

In vitro model of metastasis to bone marrow mediates prostate cancer castration resistant growth through paracrine and extracellular matrix factors.

The spread of prostate cancer cells to the bone marrow microenvironment and castration resistant growth are key steps in disease progression and significant sources of morbidity. However, the biological significance of mesenchymal stem cells (MSCs) and bone marrow derived extracellular matrix (BM-ECM) in this process is not fully understood. We therefore established an in vitro engineered bone marrow tissue model that incorporates hMSCs and BM-ECM to facilitate mechanistic studies of prostate cancer cell survival in androgen-depleted media in response to paracrine factors and BM-ECM.

Matrix elasticity regulates the secretory profile of human bone marrow-derived multipotent mesenchymal stromal cells (MSCs).

The therapeutic efficacy of multipotent mesenchymal stromal cells (MSCs) is attributed to particular MSC-derived cytokines and growth factors. As MSCs are applied locally to target organs or home there after systemic administration, they experience diverse microenvironments that are biochemically and biophysically distinct. Here we use well-defined in vitro conditions to study the impact of substrate elasticity on MSC-derived trophic factors.

Knockdown of the co-chaperone Hop promotes extranuclear accumulation of Stat3 in mouse embryonic stem cells.

A key event in the mechanism of mouse embryonic stem cell (mESC) pluripotency is phosphorylation, dimerisation and translocation to the nucleus of the signal transducer and activator of transcription3, Stat3. We used RNAi to suppress the levels of the co-chaperone Hsp70/Hsp90 organising protein (Hop) in an mESC line. Hop knockdown caused 68% depletion in Stat3 mRNA levels, decreased soluble pYStat3 levels, and led to an extranuclear accumulation of Stat3.