Leukocyte transmigration into tissue-engineered constructs is influenced by endothelial cells through Toll-like receptor signaling

Cell-based mechanisms and strategies of co-culture system both in vivo and vitro for bone tissue engineering

The lack of a functional vascular supply has been identified as a major challenge limiting the clinical introduction of stem cell-based bone tissue engineering (BTE) for the repair of large-volume bone defects (LVBD). Various approaches have been explored to improve the vascular supply in tissue-engineered constructs, and the development of strategies that could effectively induce the establishment of a functional vascular supply has become a major goal of BTE research. One of the state-of-the-art methods is to incorporate both angiogenic and osteogenic cells in co-culture systems. This review clarifies the key concepts involved, summarises the cell types and models used to date, and systematically evaluates their performance. We also discuss the cell-to-cell communication between these two cell types and the strategies explored in BTE constructs with angiogenic and osteogenic cells to optimise their functions. In addition, we outline unresolved issues and remaining obstacles that need to be overcome for further development in this field and eventual successful repair of LVBD.

Scaffold-based delivery of mesenchymal stromal cells to diabetic wounds

Foot ulceration is a major complication of diabetes mellitus, which results in significant human suffering and a major burden on healthcare systems. The cause of impaired wound healing in diabetic patients is multifactorial with contributions from hyperglycaemia, impaired vascularization and neuropathy. Patients with non-healing diabetic ulcers may require amputation, creating an urgent need for new reparative treatments. Delivery of stem cells may be a promising approach to enhance wound healing because of their paracrine properties, including the secretion of angiogenic, immunomodulatory and anti-inflammatory factors. While a number of different cell types have been studied, the therapeutic use of mesenchymal stromal cells (MSCs) has been widely reported to improve delayed wound healing. However, topical administration of MSCs via direct injection has several disadvantages, including low cell viability and poor cell localization at the wound bed. To this end, various biomaterial conformations have emerged as MSC delivery vehicles to enhance cell viability and persistence at the site of implantation. This paper discusses biomaterial-based MSCs therapies in diabetic wound healing and highlights the low conversion rate to clinical trials and commercially available therapeutic products.

Endochondral Ossification Induced by Cell Transplantation of Endothelial Cells and Bone Marrow Stromal Cells with Copolymer Scaffold Using a Rat Calvarial Defect Model

It has been recently reported that, in a rat calvarial defect model, adding endothelial cells (ECs) to a culture of bone marrow stromal cells (BMSCs) significantly enhanced bone formation. The aim of this study is to further investigate the ossification process of newly formed osteoid and host response to the poly(L-lactide-co-1,5-dioxepan-2-one) [poly(LLA-co-DXO)] scaffolds based on previous research. Several different histological methods and a PCR Array were applied to evaluate newly formed osteoid after 8 weeks after implantation. Histological results showed osteoid formed in rat calvarial defects and endochondral ossification-related genes, such as dentin matrix acidic phosphoprotein 1 (Dmp1) and collagen type II, and alpha 1 (Col2a1) exhibited greater expression in the CO (implantation with BMSC/EC/Scaffold constructs) than the BMSC group (implantation with BMSC/Scaffold constructs) as demonstrated by PCR Array. It was important to notice that cartilage-like tissue formed in the pores of the copolymer scaffolds. In addition, multinucleated giant cells (MNGCs) were observed surrounding the scaffold fragments. It was concluded that the mechanism of ossification might be an endochondral ossification process when the copolymer scaffolds loaded with co-cultured ECs/BMSCs were implanted into rat calvarial defects. MNGCs were induced by the poly(LLA-co-DXO) scaffolds after implantation, and more specific in vivo studies are needed to gain a better understanding of host response to copolymer scaffolds.

Systems-wide analysis unravels the new roles of CCM signal complex (CSC)

Cerebral cavernous malformations (CCMs) are characterized by abnormally dilated intracranial capillaries that result in increased susceptibility to stroke. Three genes have been identified as causes of CCMs; KRIT1 (CCM1), MGC4607 (CCM2) and PDCD10 (CCM3); one of them is disrupted in most CCM cases. It was demonstrated that both CCM1 and CCM3 bind to CCM2 to form a CCM signaling complex (CSC) to modulate angiogenesis. In this report, we deployed both RNA-seq and proteomic analysis of perturbed CSC after depletion of one of three CCM genes to generate interactomes for system-wide studies. Our results demonstrated a unique portrait detailing alterations in angiogenesis and vascular integrity. Interestingly, only in-direct overlapped alterations between RNA and protein levels were detected, supporting the existence of multiple layers of regulation in CSC cascades. Notably, this is the first report identifying that both β4 integrin and CAV1 signaling are downstream of CSC, conveying the angiogenic signaling. Our results provide a global view of signal transduction modulated by the CSC, identifies novel regulatory signaling networks and key cellular factors associated with CSC.

Towards reconstruction of epithelialized cartilages from autologous adipose tissue-derived stem cells

Deformities of the upper airways, including those of the nose and throat, are typically corrected by reconstructive surgery. The use of autologous somatic stem cells for repair of defects could improve quality and outcomes of such operations. The present study explored the ability of paediatric adipose-derived stem cells (pADSCs), a readily available source of autologous stem cells, to generate a cartilage construct with a functional epithelium. Paediatric ADSCs seeded on the biodegradable nanocomposite polymer, polyhedral oligomeric silsesquioxane poly(ϵ-caprolactone-urea) urethane (POSS-PCL), proliferated and differentiated towards mesenchymal lineages. The ADSCs infiltrated three-dimensional POSS-PCL nanoscaffold and chondroid matrix was observed throughout chondrogenically induced samples. In ovo chorioallantoic membrane-grafted ADSC-nanoscaffold composites were enwrapped by host vessels indicating good compatibility in an in vivo system. Furthermore, pADSCs could be induced to transdifferentiate towards barrier-forming epithelial-like cells. By combining differentiation protocols, it was possible to generate epithelial cell lined chondrogenic micromasses from the same pADSC line. This proof-of-concept study appears to be the first to demonstrate that individual pADSC lines can differentiate towards two different germ lines and be successfully co-cultured. This has important implications for bioengineering of paediatric airways and further confirms the plastic nature of ADSCs. Copyright © 2016 John Wiley & Sons, Ltd.

Angiogenic and Immunomodulatory Properties of Endothelial and Mesenchymal Stem Cells

It has been suggested that the effect of implanted cells on the local environment is important when selecting the appropriate cell type for tissue regeneration. Our aim was to compare the local tissue response to implanted human mesenchymal stem cells (MSC) and human umbilical vein endothelial cells (EC). MSC and EC were cultured in poly(L-lactide-co-1,5-dioxepan-2-one) scaffolds for 1 week in a bioreactor system, after which they were implanted subcutaneously in NOD/SCID mice. After 3 weeks, scaffolds were retrieved, and the mRNA expression of selected genes involved in hypoxia and inflammation was examined by real-time reverse transcription polymerase chain reaction and correlated with immunofluorescent staining for corresponding proteins. The Toll-like receptor signaling pathway was examined by superarray hybridization. The expression of 53 angiogenesis-related proteins was investigated by a proteome profiler angiogenesis antibody array kit. Vascularization was quantified using immunohistochemistry for CD31. The expression of hypoxia-inducible factors and biomarkers for angiogenesis was more strongly upregulated in response to implanted EC than to MSC, suggesting a higher sensitivity to low oxygen tension among EC. Hypoxic signaling was increased after implantation of EC compared with MSC, leading to a prolonged acute inflammatory phase that promoted ingrowth of vascular cells and establishment of the circulation. Inflammatory cytokines were also differently expressed at the gene and protein levels in the two experimental groups, resulting in altered recruitment of acute and chronic inflammatory cells. The end result of these differences was increased vessel formation within the constructs in the EC group.

Three-dimensional spheroid cell culture of umbilical cord tissue-derived mesenchymal stromal cells leads to enhanced paracrine induction of wound healing

Introduction

The secretion of trophic factors by mesenchymal stromal cells has gained increased interest given the benefits it may bring to the treatment of a variety of traumatic injuries such as skin wounds. Herein, we report on a three-dimensional culture-based method to improve the paracrine activity of a specific population of umbilical cord tissue-derived mesenchymal stromal cells (UCX®) towards the application of conditioned medium for the treatment of cutaneous wounds.

Methods

A UCX® three-dimensional culture model was developed and characterized with respect to spheroid formation, cell phenotype and cell viability. The secretion by UCX® spheroids of extracellular matrix proteins and trophic factors involved in the wound-healing process was analysed. The skin regenerative potential of UCX® three-dimensional culture-derived conditioned medium (CM3D) was also assessed in vitro and in vivo against UCX® two-dimensional culture-derived conditioned medium (CM2D) using scratch and tubulogenesis assays and a rat wound splinting model, respectively.

Results

UCX® spheroids kept in our three-dimensional system remained viable and multipotent and secreted considerable amounts of vascular endothelial growth factor A, which was undetected in two-dimensional cultures, and higher amounts of matrix metalloproteinase-2, matrix metalloproteinase-9, hepatocyte growth factor, transforming growth factor β1, granulocyte-colony stimulating factor, fibroblast growth factor 2 and interleukin-6, when compared to CM2D. Furthermore, CM3D significantly enhanced elastin production and migration of keratinocytes and fibroblasts in vitro. In turn, tubulogenesis assays revealed increased capillary maturation in the presence of CM3D, as seen by a significant increase in capillary thickness and length when compared to CM2D, and increased branching points and capillary number when compared to basal medium. Finally, CM3D-treated wounds presented signs of faster and better resolution when compared to untreated and CM2D-treated wounds in vivo. Although CM2D proved to be beneficial, CM3D-treated wounds revealed a completely regenerated tissue by day 14 after excisions, with a more mature vascular system already showing glands and hair follicles.

Conclusions

This work unravels an important alternative to the use of cells in the final formulation of advanced therapy medicinal products by providing a proof of concept that a reproducible system for the production of UCX®-conditioned medium can be used to prime a secretome for eventual clinical applications.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0082-5) contains supplementary material, which is available to authorized users.