Combining biomaterial scaffolds with stem cells for tissue engineering applications

Noted Stem Cell Researchers Present a State-of-the-Art Review in the Inaugural Article Published in StemJournal

StemJournal, a new open access, peer-reviewed journal published by IOS Press, announces publication of its inaugural article, "Combining Stem Cells and Biomaterial Scaffolds for Constructing Tissues and Cell Delivery," by Stephanie M. Willerth, PhD, and Shelly E. Sakiyama-Elbert, PhD. This timely overview of the available biomaterials for directing stem cell differentiation as a means of producing replacements for diseased or damaged tissues is a comprehensive update of the classic review published in StemBook in 2008.

"In the 10 years since the publication of our review, the field of stem biology has advanced rapidly as regenerative medicine strategies move into clinical trials for a variety of health disorders," explain Dr. Willerth, of the Department of Mechanical Engineering and Division of Medical Sciences, University of Victoria; and the International Collaboration on Repair Discoveries, University of British Columbia, and Dr. Sakiyama-Elbert, of the Department of Biomedical Engineering, University of Texas-Austin. "The biomaterials have improved along with drug delivery systems for promoting the desired stem cell behavior, as have methods for confirming tissue function. The field of tissue engineering has also advanced significantly in harnessing the potential of pluripotent stem cells. Another exciting area is the development of novel bio-inks for 3D printing stem cell-derived tissues."

Stem cells possess two novel properties: the ability to produce additional stem cells and the capacity to become multiple cell types. The major types of stem cells include adult, embryonic, fetal, induced pluripotent, and mesenchymal stem cells. Both natural and synthetic biomaterials can serve as the starting point for generating bioactive scaffolds for controlling stem cell differentiation into the desired tissue type. Types of scaffolds include hydrogels, micro- and nanofibers, and micro- and nanospheres.

This review encapsulates current foundational knowledge on general concepts that apply when combining biomaterial scaffolds with stem cells for tissue engineering applications, including the widespread adoption of induced pluripotent stem cells. Presenting promising strategies for engineering tissues for both in vitro and in vivo applications, it covers:

Types of Scaffold Formulations - Both natural and synthetic biomaterials can serve as the starting point for generating bioactive scaffolds for controlling stem cell differentiation into the desired tissue type.

Natural Biomaterials - The proteins and polysaccharides found in the extracellular matrix provide an obvious starting point when developing scaffolds derived from natural biomaterials.

Synthetic Biomaterials - Synthetic biomaterials provide an alternative to natural materials for engineering tissues from stem cells and offer many advantages.

Ceramic-Based Biomaterials - Ceramics, inorganic materials formed through treatment with heat, possess crystalline structures, meaning they are often porous and brittle.

While many of these materials have not been fully developed for specific tissue engineering applications, further work will continue to optimize these formulations for translation to the clinic for targeted applications. For example, optimized scaffolds could enhance the survival and differentiation of neural stem cells being transplanted into the diseased or damaged nervous system, which could lead to improved function. The type of material and the cues that are incorporated in the scaffold play a large role in directing the fate of the stem cells seeded inside, as detailed in this review.

According to the authors, the ability to further functionalize the materials discussed in this review in terms of their mechanical and chemical properties provides an excellent opportunity for future work, because such bioactive and instructive scaffolds can improve cell survival and differentiation into the desired phenotypes. The method of fabrication serves as an important parameter, which allows different types of patterns and architecture to be formed, which include hydrogels, microcarriers, fibers, and 3D bioprinted constructs. The latter offers the possibility of printing constructs to fill an injury site, as well as the ability to produce tissues with complex structures containing multiple cell types.

The future of this line of stem cell research is promising. "The ability to make universal induced pluripotent stem cell lines for engineering replacement tissues would be a game changer as it would make it easier to rapidly deliver effective, personalized therapies. Cellular reprogramming also has tremendous promise in terms of cell therapy," comment Dr. Willerth and Dr. Sakiyama-Elbert.