Promotion of osteoblastic differentiation and osteogenic transcription factor expression on a microgroove titanium surface with immobilized fibronectin or bone sialoprotein II

Functionalization of 3D-Printed Titanium Scaffolds with Elastin-like Recombinamers to Improve Cell Colonization and Osteoinduction

The 3D printing of titanium (Ti) offers countless possibilities for the development of personalized implants with suitable mechanical properties for different medical applications. However, the poor bioactivity of Ti is still a challenge that needs to be addressed to promote scaffold osseointegration. The aim of the present study was to functionalize Ti scaffolds with genetically modified elastin-like recombinamers (ELRs), synthetic polymeric proteins containing the elastin epitopes responsible for their mechanical properties and for promoting mesenchymal stem cell (MSC) recruitment, proliferation, and differentiation to ultimately increase scaffold osseointegration. To this end, ELRs containing specific cell-adhesive (RGD) and/or osteoinductive (SNA15) moieties were covalently attached to Ti scaffolds. Cell adhesion, proliferation, and colonization were enhanced on those scaffolds functionalized with RGD-ELR, while differentiation was promoted on those with SNA15-ELR. The combination of both RGD and SNA15 into the same ELR stimulated cell adhesion, proliferation, and differentiation, although at lower levels than those for every single moiety. These results suggest that biofunctionalization with SNA15-ELRs could modulate the cellular response to improve the osseointegration of Ti implants. Further investigation on the amount and distribution of RGD and SNA15 moieties in ELRs could improve cell adhesion, proliferation, and differentiation compared to the present study.

Bone Sialoprotein Immobilized in Collagen Type I Enhances Angiogenesis In Vitro and In Ovo

Bone fracture healing is a multistep process, including early immunological reactions, osteogenesis, and as a key factor, angiogenesis. Molecules inducing osteogenesis as well as angiogenesis are rare, but hold promise to be employed in bone tissue engineering. It has been demonstrated that the bone sialoprotein (BSP) can induce bone formation when immobilized in collagen type I, but its effect on angiogenesis still has to be characterized in detail. Therefore, the aim of this study was to analyse the effects of BSP immobilized in a collagen type I gel on angiogenesis. First, in vitro analyses with endothelial cells (HUVECs) were performed detecting enhancing effects of BSP on proliferation and gene expression of endothelial markers. A spheroid model was employed confirming these results. Finally, the inducing impact of BSP-collagen on vascular density was proved in a yolk sac membrane assay. Our results demonstrate that BSP is capable of inducing angiogenesis and confirm that collagen type I is the optimal carrier for this protein. Taking into account former results, and literature showing that BSP also induces osteogenesis, one can hypothesize that BSP couples angiogenesis and osteogenesis, making it a promising molecule to be used in bone tissue regeneration.

OSGIN2 regulates osteogenesis of jawbone BMSCs in osteoporotic rats

Background

Augmentation of oxidative stress after estrogen deficiency leading to functional deficiency of jawbone bone marrow mesenchymal stem cells (BMSCs) causes jawbone loss in osteoporosis. OSGIN2, an oxidative stress induced factor, has been found to be associated with skeletal diseases. This study aims to investigate the function of OSGIN2 in jawbone BMSCs of osteoporotic rats. Jawbone BMSCs were used.

Results

Oxidative stress was increased in jawbone BMSCs of osteoporotic rats, meanwhile OSGIN2 was also up-regulated. Osteogenesis of jawbone BMSCs was declined under oxidative stress, while silence of OSGIN2 ameliorated the osteogenic deficiency. RORα and its downstream osteogenic markers (BSP and OCN) decreased under oxidative stress, while knocking-down of OSGIN2 restored their expressions. Inhibition of OSGIN2 improved the osteogenesis of jawbone BMSCs under oxidative stress, whereas down-regulation of RORα offset the effect. Intra-jawbone infusion of si-OSGIN2 rescued jawbone loss and promoted new bone deposition of osteoporotic rats.

Conclusions

Oxidative stress is redundant in osteoporosis, which results in up-regulation of OSGIN2. OSGIN2 restricts osteogenic ability of jawbone BMSCs via regulating RORα, while silencing of OSGIN2 rescues the osteogenic deficiency of osteoporotic rats.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12860-022-00423-8.

Proteoglycans and Glycosaminoglycans in Stem Cell Homeostasis and Bone Tissue Regeneration

Stem cells maintain a subtle balance between self-renewal and differentiation under the regulatory network supported by both intracellular and extracellular components. Proteoglycans are large glycoproteins present abundantly on the cell surface and in the extracellular matrix where they play pivotal roles in facilitating signaling transduction and maintaining stem cell homeostasis. In this review, we outline distinct proteoglycans profiles and their functions in the regulation of stem cell homeostasis, as well as recent progress and prospects of utilizing proteoglycans/glycosaminoglycans as a novel glycomics carrier or bio-active molecules in bone regeneration.

Proteins, peptides and peptidomimetics as active agents in implant surface functionalization

The recent impact of implants on improving the human life quality has been enormous. During the past two decades we witnessed major advancements in both material and structural development of implants. They were driven mainly by the increasing patients' demand and the need to address the major issues that come along with the initially underestimated complexity of the bone-implant interface. While both, the materials and design of implants reached a certain, balanced state, recent years brought a shift in focus towards the bone-implant interface as the weakest link in the increasing implant long-term usability. As a result, several approaches were developed. They aimed at influencing and enhancing the implant osseointegration and its proper behavior when under load and stress. With this review, we would like to discuss the recent advancements in the field of implant surface modifications, emphasizing the importance of chemical methods, focusing on proteins, peptides and peptidomimetics as promising agents for titanium surface coatings.

Identification of the Biomarkers and Pathological Process of Heterotopic Ossification: Weighted Gene Co-Expression Network Analysis

Heterotopic ossification (HO) is the formation of abnormal mature lamellar bone in extra-skeletal sites, including soft tissues and joints, which result in high rates of disability. The understanding of the mechanism of HO is insufficient. The aim of this study was to explore biomarkers and pathological processes in HO+ samples. The gene expression profile GSE94683 was downloaded from the Gene Expression Omnibus database. Sixteen samples from nine HO- and seven HO+ subjects were analyzed. After data preprocessing, 3,529 genes were obtained for weighted gene co-expression network analysis. Highly correlated genes were divided into 13 modules. Finally, the cyan and purple modules were selected for further study. Gene ontology functional annotation and Kyoto Encyclopedia of Genes and Genomes pathway enrichment indicated that the cyan module was enriched in a variety of components, including protein binding, membrane, nucleoplasm, cytosol, poly(A) RNA binding, biosynthesis of antibiotics, carbon metabolism, endocytosis, citrate cycle, and metabolic pathways. In addition, the purple module was enriched in cytosol, mitochondrion, protein binding, structural constituent of ribosome, rRNA processing, oxidative phosphorylation, ribosome, and non-alcoholic fatty liver disease. Finally, 10 hub genes in the cyan module [actin related protein 3 (ACTR3), ADP ribosylation factor 4 (ARF4), progesterone receptor membrane component 1 (PGRMC1), ribosomal protein S23 (RPS23), mannose-6-phosphate receptor (M6PR), WD repeat domain 12 (WDR12), synaptosome associated protein 23 (SNAP23), actin related protein 2 (ACTR2), siah E3 ubiquitin protein ligase 1 (SIAH1), and glomulin (GLMN)] and 2 hub genes in the purple module [proteasome 20S subunit alpha 3 (PSMA3) and ribosomal protein S27 like (RPS27L)] were identified. Hub genes were validated through quantitative real-time polymerase chain reaction. In summary, 12 hub genes were identified in two modules that were associated with HO. These hub genes could provide new biomarkers, therapeutic ideas, and targets in HO.

Bone physiology as inspiration for tissue regenerative therapies

The development, maintenance of healthy bone and regeneration of injured tissue in the human body comprise a set of intricate and finely coordinated processes. However, an analysis of current bone regeneration strategies shows that only a small fraction of well-reported bone biology aspects has been used as inspiration and transposed into the development of therapeutic products. Specific topics that include inter-scale bone structural organization, developmental aspects of bone morphogenesis, bone repair mechanisms, role of specific cells and heterotypic cell contact in the bone niche (including vascularization networks and immune system cells), cell-cell direct and soluble-mediated contact, extracellular matrix composition (with particular focus on the non-soluble fraction of proteins), as well as mechanical aspects of native bone will be the main reviewed topics. In this Review we suggest a systematic parallelization of (i) fundamental well-established biology of bone, (ii) updated and recent advances on the understanding of biological phenomena occurring in native and injured tissue, and (iii) critical discussion of how those individual aspects have been translated into tissue regeneration strategies using biomaterials and other tissue engineering approaches. We aim at presenting a perspective on unexplored aspects of bone physiology and how they could be translated into innovative regeneration-driven concepts.