Edyta Wrobel

Perinatal sources of mesenchymal stem cells: Wharton’s jelly, amnion and chorion

Recently, stem cell biology has become an interesting topic, especially in the context of treating diseases and injuries using transplantation therapy. Several varieties of human stem cells have been isolated and identified in vivo and in vitro. Ideally, stem cells for regenerative medical application should be found in abundant quantities, harvestable in a minimally invasive procedure, then safely and effectively transplanted to either an autologous or allogenic host. The two main groups of stem cells, embryonic stem cells and adult stem cells, have been expanded to include perinatal stem cells. Mesenchymal stem cells from perinatal tissue may be particularly useful in the clinic for autologous transplantation for fetuses and newborns, and after banking in later stages of life, as well as for in utero transplantation in case of genetic disorders.This review highlights the characteristics and therapeutic potential of three human mesenchymal stem cell types obtained from perinatal sources: Wharton’s jelly, the amnion, and the chorion.

Effect of substrate stiffness on the osteogenic differentiation of bone marrow stem cells and bone-derived cells.

There is a profound dependence of cell behaviour on the stiffness of its microenvironment. To gain a better understanding of the regulation of cellular differentiation by mechanical cues, we investigated the influence of matrix stiffness (E = 1.46 kPa and E = 26.12 kPa) on differentiated osteogenic cell lineage of bone marrow stem cells (BM‐MSCs) and bone‐derived cells (BDCs) using flexible collagen‐coated polyacrylamide substrates. Differentiation potential was determined by measuring alkaline phosphatase activity, expression of osteoblast‐specific markers including alkaline phosphatase, osteocalcin, Runx2 and collagen type I, as well as assessment of mineralisation (Alizarin Red S staining). We found that osteogenic differentiation can be regulated by the rigidity of the substrate, which may depend on the commitment in multi‐ or uni‐potent targeting cells. Osteogenic differentiation of BM‐MSCs was enhanced on a stiff substrate compared to a soft one, whereas BDCs osteogenic differentiation did not vary depending on the substrate stiffness. The data help in understanding the role of the external mechanical determinants in stem cell differentiation, and can also be useful in translational approach in functional tissue engineering.

Candidate bone-tissue-engineered product based on human-bone-derived cells and polyurethane scaffold.

Biodegradable polyurethanes (PURs) have recently been investigated as candidate materials for bone regenerative medicine. There are promising reports documenting the biocompatibility of selected PURs in vivo and the tolerance of certain cells toward PURs in vitro - potentially to be used as scaffolds for tissue-engineered products (TEPs). The aim of the present study was to take a step forward and create a TEP using human osteogenic cells and a polyurethane scaffold, and to evaluate the quality of the obtained TEP in vivo. Human-bone-derived cells (HBDCs) were seeded and cultured on polyurethane scaffolds in a bioreactor for 14 days. The TEP examination in vitro was based on the evaluation of cell number, cell phenotype and cell distribution within the scaffold. TEPs and control samples (scaffolds without cells) were implanted subcutaneously into SCID mice for 4 and 13 weeks. Explants harvested from the animals were examined using histological and immunohistochemical methods. They were also tested in mechanical trials. It was found that dynamic conditions for cell seeding and culture enable homogeneous distribution, maintaining the proliferative potential and osteogenic phenotype of the HBDCs cultured on polyurethane scaffolds. It was also found that HBDCs implanted as a component of TEP survived and kept their ability to produce the specific human bone extracellular matrix, which resulted in higher mechanical properties of the harvested explants when preseeded with HBDCs. The whole system, including the investigated PUR scaffold and the method of human cell seeding and culture, is recommended as a candidate bone TEP.

α2β1 integrin-mediated mechanical signals during osteodifferentiation of stem cells from the Wharton’s jelly of the umbilical cord

INTRODUCTION The formation and maintenance of tissues is regulated by various signals triggered by biological, chemical, and physical factors. Data increasingly confirm that matrix or tissue elasticity plays an influential role in regulating numerous cell functions. The aim of the present study was to better understand the regulation of cellular differentiation by mechanical cues. We studied the influence of matrix stiffness on the osteodifferentiation of two cell lineages characterized by different responses: mesenchymal stromal/stem cells isolated from the Whartons jelly of the umbilical cord (UC-MSCs) with strong stiffness-dependent responses; and bone-derived cells (BDCs), which are insensitive to changes in matrix rigidity. The study also aimed to delineate how matrix stiffness affects intracellular signaling through focal adhesion kinase (FAK) activity—one of the key components in integrin-mediated signaling pathways. MATERIAL AND METHODS The effect of substrate stiffness on the expression of α2, α5, and β1 integrin was studied using real time PCR and Western blot using cells cultured in an osteogenic medium on tunable polyacrylamide gels coated with type I collagen, with elasticities corresponding to Youngs moduli of 1.46 kPa and 26.12 kPa. FAK activity was monitored using ELISA assays. RESULTS We demonstrate for the first time the changes in the expression of α2, α5, and β1 integrin subunits in perinatal stem cells and in adult osteoblast precursor cells during in vitro osteogenic differentiation on surfaces characterized by different stiffness. We found that matrix rigidity significantly affects the osteogenic differentiation of UC-MSCs through α2 integrin-mediated mechanotransduction events, though not through the α5 integrin subunit. In BDCs, there were no significant changes in the expression levels of the tested protein associated with varying stiffness. CONCLUSIONS Our results provide evidence that matrix rigidity affects the osteogenic differentiation of UC-MSCs via mechanotransduction events mediated by α2 integrin subunits.

The Most Important Transcriptional Factors of Osteoblastogenesis

Summary One of the key issues of organogenesis is the understanding of mechanisms underlying the differentiation of progenitor cells into more specialized cells of individual tissues. Recent transcriptomic and proteomic approaches of molecular biology have led to the identification of several factors and mechanisms regulating morphogenesis at the genetic level which affect the function of already differentiated cells. In the last few years, several reports about osteoblastogenesis have been published. This review presents recent findings on the role of the most important transcription factors supporting bone formation.