An Overview of RNA-Based Scaffolds for Osteogenesis

Abstract

Tissue engineering provides new hope for the combination of cells, scaffolds, and bifactors for bone osteogenesis. This is achieved by mimicking the bone's natural behavior in recruiting the cell's molecular machinery for our use. Many researchers have focused on developing an ideal scaffold with specific features, such as good cellular adhesion, cell proliferation, differentiation, host integration, and load bearing. Various types of coating materials (organic and non-organic) have been used to enhance bone osteogenesis. In the last few years, RNA-mediated gene therapy has captured attention as a new tool for bone regeneration. In this review, we discuss the use of RNA molecules in coating and delivery, including messenger RNA (mRNA), RNA interference (RNAi), and long non-coding RNA (lncRNA) on different types of scaffolds (such as polymers, ceramics, and metals) in osteogenesis research. In addition, the effect of using gene-editing tools-particularly CRISPR systems-to guide RNA scaffolds in bone regeneration is also discussed. Given existing knowledge about various RNAs coating/expression may help to understand the process of bone formation on the scaffolds during osseointegration.

Keywords: CRISPR; RNA; bone osteogenesis; gene therapy; tissue engineering.

FIGURE 1

Schematic illustration showing different types of RNA in mammalian cells mRNA, miRNA, siRNA, and lnRN. (A) Premature mRNA gets exported to the cytoplasm then translated into protein by ribosomes. (B,C) pre miRNA and pre siRNA are produced in the nucleus and then gets exported to the cytoplasm then processed by Dicer followed by RISC complex formation, finally the miRNA or siRNA binds to the target sequence by complementation. This causes the degradation of the target RNA or translation block. (D) lncRNA are produced in the nucleus then exported into the cytoplasm in which they can regulate the gene expression (Created with BioRender.com).

FIGURE 2

Schematic illustration showingthe two main used methods for miRNA mediated gene silencing in scaffold-based bone regeneration. miRNA is introduced into cells and works on silencing (A) cellular miRNA that can target osteogenesis related genes (anti-miRNA) (B) osteogenesis related genes (Created with BioRender.com).

FIGURE 3

Schematic illustration of RNA delivery method used for bone osteointegration. RNA was combined with vector (e.g., lipids and polymers) and/or transfecting the MSCs before loaded to the scaffolds (e.g., gel or porous scaffolds) (Created with BioRender.com).

FIGURE 4

Schematic showing CRIPSR based genome editing. (A) CRISPR/Cas9 system works by the sgRNA recognize the target DNA then the Cas9 preform a double strand break, the NHEJ repair system then may causes insertion or deletion resulting in a change in the target gene expression. (B,C) CRISPRa/CRISPRi systems works by the sgRNA recognition of the target site followed by the activation or repression of gene expression of the target gene via an activation or a repression domain, altering the gene expression of the target gene (Created with BioRender.com).