BMP-2 Long-Term Stimulation of Human Pre-Osteoblasts Induces Osteogenic Differentiation and Promotes Transdifferentiation and Bone Remodeling Processes

Bone morphogenic protein (BMP-) 2 plays an important role in the regeneration of bone defects by promoting osteogenic differentiation. However, several animal studies have reported adverse side effects of BMP-2, including osteoclast activation, induction of peroxisome proliferator- activated receptor gamma (PPARG)expression, and inflammation. High BMP-2 concentrations are thought to be responsible for these side effects. For this reason, primary pre-osteoblasts were exposed to lower BMP-2 concentrations (1 and 2 µg/mL). Long-term exposure (up to 28 days) was performed to investigate whether this stimulation protocol may promote osteogenic differentiation without causing the side effects mentioned above. The results showed that BMP-2 treatment for 14 or 28 days resulted in increased osteogenesis, through an increase in runt-related transcription factor 2, osterix, alkaline phosphatase, and integrin-binding sialoprotein expression. However, an increase in tumor necrosis factor alpha and receptor activator of nuclear factor kappa-Β ligand protein levels was observed after BMP-2 exposure, indicating also an increased potential for osteoclast activation by osteoblasts. Additionally, morphological changes like intracellular, filled vacuoles could be detected. Enhanced PPARG and perilipin 1 mRNA transcripts and lipid droplets indicated an induced adipogenic differentiation. Overall, the data demonstrate that long-term BMP-2 exposure promotes not only osteogenic differentiation but also adipogenesis and regulates mediators involved in osteoclast activation in vitro

Characterization of the osteogenic differentiation capacity of human bone cells on hybrid β-TCP/ZrO2 structures

This study deals with synthetic biomaterials that are biocompatible and mechanically stable to serve as a potential bone graft for improved mandibular reconstruction. To fabricate novel hybrid scaffolds containing beta-tricalcium phosphate (β-TCP) and zirconia (ZrO2), 3D printing was combined with Freeze Foaming to achieve a certain porosity, mimicking cancellous bone. The aim was to characterize the differentiation capacity of human pre-osteoblasts on the hybrid scaffolds. Although a good biocompatibility was demonstrated for the tested components of the hybrid scaffold, pure β-TCP foams showed the best results regarding osteogenic differentiation and pro-inflammatory processes. To enhance the osteoinductive properties of the β-TCP foam, the structures were also biofunctionalized with bone morphogenic protein 2 (BMP–2) and its effect was analyzed either on single cell cultures of pre-osteoblasts or pre-osteoblasts directly co-cultured with human peripheral blood mononuclear cells (PBMCs). The latter served to analyze the induction of bone remodelling processes. The immobilization of BMP-2 on scaffolds and its biological accessibility could be demonstrated, however, the biofunctionalization did not result in an enhanced differentiation capacity and bone remodeling processes of either pre-osteoblasts or directly co-cultured pre-osteoblasts and PBMCs

Discordant Monozygotic Parkinson Disease Twins: Role of Mitochondrial Integrity

Objective Even though genetic predisposition has proven to be an important element in Parkinson's disease (PD) etiology, monozygotic (MZ) twins with PD displayed a concordance rate of only about 20% despite their shared identical genetic background. Methods We recruited 5 pairs of MZ twins discordant for idiopathic PD and established skin fibroblast cultures to investigate mitochondrial phenotypes in these cellular models against the background of a presumably identical genome. To test for genetic differences, we performed whole genome sequencing, deep mitochondrial DNA (mtDNA) sequencing, and tested for mitochondrial deletions by multiplex real‐time polymerase chain reaction (PCR) in the fibroblast cultures. Further, the fibroblast cultures were tested for mitochondrial integrity by immunocytochemistry, immunoblotting, flow cytometry, and real‐time PCR to quantify gene expression. Results Genome sequencing did not identify any genetic difference. We found decreased mitochondrial functionality with reduced cellular adenosine triphosphate (ATP) levels, altered mitochondrial morphology, elevated protein levels of superoxide dismutase 2 (SOD2), and increased levels of peroxisome proliferator‐activated receptor‐gamma coactivator‐α (PPARGC1A) messenger RNA (mRNA) in skin fibroblast cultures from the affected compared to the unaffected twins. Further, there was a tendency for a higher number of somatic mtDNA variants among the affected twins. Interpretation We demonstrate disease‐related differences in mitochondrial integrity in the genetically identical twins. Of note, the clinical expression matches functional alterations of the mitochondri