Genetically engineered mesenchymal stem cells: The ongoing research for bone tissue engineering

miR-182-5p overexpression inhibits chondrogenesis by down-regulating PTHLH

Human bone marrow mesenchymal stem cells (hBM-MSC) have the ability of differentiating into chondrocytes and osteoblasts. miR-182-5p promotes osteoclastogenesis and bone metastasis by up-regulating the expression of parathyroid hormone-like hormone (PTHLH). However, the function of miR-182-5p in chondrogenesis is still unknown. Mimic or inhibitor of miR-182-5p was used to upregulate or knock-down miR-182-5p expression, respectively. We analyzed chondrogenesis by Safranin O staining and Blyscan™ Sulfated Glycosaminoglycan Assay. Immunohistochemistry, real-time PCR, and Western bolts were used to detect related makers. miR-182-5p overexpression inhibited chondrogenesis. Dual-luciferase reporter assay indicated that PTHLH was one of the target genes of miR-182-5p. Further studies showed that miR-182-5p overexpression down-regulated the expression of SOX-9 and COL2A1, but up-regulated COL1A1 and COL10A1. Consistently, miR-182-5p knock-down had the opposite effects. This effect of miR-182-5p in BM-MSCs can be rescued by PTHLH overexpression. miR-182-5p may play a negative role in chondrogenesis by down-regulating PTHLH.

Tissue engineering using 3D printed nano-bioactive glass loaded with NELL1 gene for repairing alveolar bone defects

The purposes of this study were to construct a novel tissue engineered bone composed of 3D-printed bioactive glass block/chitosan nanoparticles (BD/CSn) composites loaded with Nel-like Type I molecular-1 DNA (pDNA-NELL1) and/or bone marrow mesenchymal stem cells (BMSCs), and study their osteogenic activities by repairing bone defects in rhesus monkeys. CSn with NELL1 gene plasmid and rhesus monkey BMSCs were composited with a BD scaffold to prepare the tissue-engineered bone. Four adult female rhesus monkeys with 10- to 12-years old and 5-7 kg in weight were used in animal experiments. The first and second premolar teeth from four regions of each monkey were removed to form bone defects with size of 10 × 10 × 5 mm, which were then implanted with above-mentioned tissue engineered bone. At 12 weeks after the implantation, gross observations, X-ray and micro-CT observations revealed that the new bone was extremely close to normal bone in mass, density, hardness, and structure. The bony cortex was smooth and closely connected to the surrounding normal bone. Histological observations revealed moderate inflammation in the repair area, and the new bone tissues were similar to normal ones. In conclusion, tissue engineered bone of this study exhibited good osteoconductivity for promoting the formation of new alveolar bone tissue, and NELL1 gene played a promotional role in bone regeneration.

Adenovirus-mediated bone morphogenetic protein-2 promotes osteogenic differentiation in human mesenchymal stem cells in vitro

Delayed and failed bone union following fracture is a common clinical complication that requires treatment in orthopedics. Cell-based therapies and tissue-engineering approaches are potential therapeutic strategies for bone repair and fracture healing. However, the effect of adenovirus expressing bone morphogenetic protein-2 (Ad-BMP-2) on the osteogenic ability of human mesenchymal stem cells (hMSCs) has remained to be fully elucidated. Therefore, in the present study, hMSCs were transduced using Ad-BMP-2 to assess the effects of its application and to determine whether Ad-BMP-2 promotes the osteogenic differentiation of hMSCs. The purity of the hMSC cultures was assessed using flow cytometric analysis. In order to assess the osteogenic activity, alkaline phosphatase activity (ALP) was measured and to estimate the osteoblastic mineralization and calcification, von Kossa staining for phosphates was performed. Cells positive for Src homology 2 domain were determined to be hMSCs and the presence of CD34 was used to distinguish hematopoietic lineages. Following treatment, the Ad-BMP-2 and control group had significantly increased ALP levels (P<0.05). Compared to the blank group and the group transfected with adenoviral vector containing LacZ, the phosphate deposition in the Ad-BMP-2 group and the positive control group treated with dexamethasone was markedly increased. The results of the present study suggested that Ad-BMP-2 promotes osteogenic differentiation in hMSCs and may have a potential application in treating delayed union and nonunion following bone fracture.

Mesenchymal stem/stromal cells as a delivery platform in cell and gene therapies

Regenerative medicine relying on cell and gene therapies is one of the most promising approaches to repair tissues. Multipotent mesenchymal stem/stromal cells (MSC), a population of progenitors committing into mesoderm lineages, are progressively demonstrating therapeutic capabilities far beyond their differentiation capacities. The mechanisms by which MSC exert these actions include the release of biomolecules with anti-inflammatory, immunomodulating, anti-fibrogenic, and trophic functions. While we expect the spectra of these molecules with a therapeutic profile to progressively expand, several human pathological conditions have begun to benefit from these biomolecule-delivering properties. In addition, MSC have also been proposed to vehicle genes capable of further empowering these functions. This review deals with the therapeutic properties of MSC, focusing on their ability to secrete naturally produced or gene-induced factors that can be used in the treatment of kidney, lung, heart, liver, pancreas, nervous system, and skeletal diseases. We specifically focus on the different modalities by which MSC can exert these functions. We aim to provide an updated understanding of these paracrine mechanisms as a prerequisite to broadening the therapeutic potential and clinical impact of MSC.

AvidinOX&#x2122; for tissue targeted delivery of biotinylated cells

AvidinOX™, a product containing aldehyde groups, generated by ligand-assisted sugar oxidation of avidin by sodium periodate, maintains the capacity to bind biotin with very high affinity and exhibits the property to chemically link cellular and tissue proteins through Schiff's base formation thus residing in tissues for weeks. In recent studies, we have shown that AvidinOX exhibits much higher persistency in the skeletal muscle than native avidin. The aim of the present study is to evaluate whether AvidinOX-biotin interaction might be exploited to target biotinylated cells to an AvidinOX pre-treated muscle. To accomplish this we performed the following experiments: 1) The proliferation and differentiation properties of biotinylated C2C12 myoblasts were tested in vitro upon linkage to AvidinOX; 2) Bone marrow-derived cells (BMDC) were isolated from GFP positive transgenic mice [strain C57 BL/6-tg (UBC-GFP)] and after biotinylation (bBMDC) were intravenously administered to naive and MAVA+ (Mouse anti Avidin Antibody) C57/B6 mice previously injected with AvidinOX in a tibial muscle (TM). Localization efficiency of GFP+ bBMDC was evaluated on serial sections of the AvidinOX- and vehicle-treated (contra lateral limb) TM, 5 days after transplantation. Results show that biotinylated C2C12 cells, once linked to AvidinOX, maintain their proliferation and differentiation capacity, in vitro. Intravenous injection of biotinylated GFP+ bone marrow-derived cells leads to their specific and efficient localization in the AvidinOX-pre-treated, but not contra lateral muscle of both naive and MAVA+ mice. The present data suggest a potential use of AvidinOX to improve tissue targeted delivery of biotinylated cells.

Mesenchymal stem cells as a potent cell source for bone regeneration

While small bone defects heal spontaneously, large bone defects need surgical intervention for bone transplantation. Autologous bone grafts are the best and safest strategy for bone repair. An alternative method is to use allogenic bone graft. Both methods have limitations, particularly when bone defects are of a critical size. In these cases, bone constructs created by tissue engineering technologies are of utmost importance. Cells are one main component in the manufacture of bone construct. A few cell types, including embryonic stem cells (ESCs), adult osteoblast, and adult stem cells, can be used for this purpose. Mesenchymal stem cells (MSCs), as adult stem cells, possess characteristics that make them good candidate for bone repair. This paper discusses different aspects of MSCs that render them an appropriate cell type for clinical use to promote bone regeneration.