What is scaffolding in regenerative medicine?

 

Stem cells are self-renewing cells that can be differentiated into other cell types. Conventional in vitro models for studying stem cells differentiation are usually preformed in two-dimensional (2D) cultures. The design of three-dimensional (3D) in vitro models which ideally are supposed to mimic the in vivo stem cells microenvironment is potentially useful for inducing stem cell derived tissue formation. Biodegradable scaffolds play an important role in creating a 3D environment to induce tissue formation. The application of scaffolding materials together with stem cell technologies are believed to hold enormous potential for tissue regeneration. In this review, we provide an overview of application of tissue engineered scaffolds and stem cells for the development of stem cell-based engineered tissue replacements. In particular, we focus on bone marrow stem cells (BMSCs) and mesenchymal stem cell (MSCs) due to their extensive clinical applications.

Stem cells are primitive cells found in many multi-cellular organisms and possess self-renewal and potency abilities. Self-renewal is that characteristic of stem cells that maintains them in numerous cell cycle divisions, while potency defines the differentiation capability of stem cells into mature cell types. Mammalian stem cells are categorized based on the source they are derived from: embryonic stem (ES) cells, derived from blastocysts, and adult stem cells, found in adult tissues

Cell proliferation in 3-D scaffold, needs oxygen and nutrition supply. Therefore, the 3-D scaffold materials should provide such an environment for cells. The artificial scaffolds formed by self-assembling molecules not only provide suitable support for cell proliferation but also serve as a medium through which diffusion of soluble factors and migration of cells can occur. The result of the cell attachment and proliferation revealed that diffusion of nutrients, bioactive factors, and oxygen through these highly hydrated networks is sufficient for survival of large numbers of cells for extended periods of time.

The 3D scaffolds are capable of differentiating a single progenitor cell population into particular lineage either due to bulk incorporation of soluble factors within the scaffolds or due to exogenous delivery of chemicals, hormones, and growth factors in culture medium. Therefore, design of patterned scaffolds with the ability to develop multiple lineages and hybrid organ structures could provide promising alternatives.

Metal scaffolds like titanium are bio-compatible and suitable for hard-tissue applications, such as the growth and differentiation of rat dental pulp progenitor cells into odontoblast-like cells. In order to improve their efficacy, metal scaffolds can be covered with biological compounds, like titanium fibers pre-coated with ECM components that support the osteogenic differentiation of rats’ BMSCs.

Another type of scaffolds is made of organic materials that provide a bio-mimetic environment for stem cells. Human BMSCs regenerate bone in marine sponge skeletons, cartilage in silk fibroin scaffolds, and adipose tissue in gelatin. To provide mechanical strength, biological agents influencing stem cell fate could be added to the scaffold’s compounds. Marine sponge skeletons, for example, contain these cell adhesion proteins: fibronectin, collagen and gelatin.

The application of scaffolding materials together with stem cell technologies are believed to hold enormous potential for tissue regeneration. In this review, we provide an overview of application of tissue engineered scaffolds and stem cells for the development of stem cell-based engineered tissue replacements. In particular, we focus on bone marrow stem cells (BMSCs) and mesenchymal stem cell (MSCs) due to their extensive clinical applications.