Bone Tissue Engineering

Project 1: Non-destructive Real-time Imaging and Control of Bone Tissue Engineering
Graduate Student Researcher: Bryce Whited

The use of tissue engineered scaffolds in combination with progenitor cells has emerged as a promising strategy to restore or replace tissues damaged by disease or trauma. In addition to being biocompatible and exhibiting appropriate mechanical properties, scaffolds must be designed to sustain cell attachment, proliferation, and differentiation to ultimately produce the desired tissue once implanted in the patient. Conventional techniques used to assess successful scaffold design include cell viability stains, DNA assays, and histological sectioning/staining. While significant information can be gained from using these methodologies, they are destructive to the sample and only provide snapshots of scaffold and cell development at a limited number of time points. Consequently, key temporal and spatial information relating to tissue regeneration in the scaffold is lost utilizing these techniques. Thus, the ability to non-destructively monitor cell viability, proliferation, and differentiation in real-time is of great importance for scaffold design and tissue engineering.

To meet this challenge, we have developed a novel imaging-bioreactor system capable of monitoring the development of tissue engineered scaffolds at the cellular level non-destructively and in real time. Our system is based on the incorporation of miniature hollow-core silica fiber (HCFs) imaging microchannels into the scaffold. We have demonstrated the capability of cellular-level imaging of cells labeled with fluorescent proteins through relatively thick scaffolds (~1 mm) (Figure 1). After some modifications, our imaging system can be extended to monitor scaffold development after in-vivo implantation.

Our group is also interested in designing novel tissue scaffolds for bone regeneration. One such scaffold that we have fabricated and characterized is an apatite coated electrospun Poly lactic acid scaffold that enhances cellular infiltration and promotes osteoblastic differentiation (Whited et al., 2010) (Figure 2).

Funding
Institute for Critical Technologies and Applied Sciences Grant

1R01HL098912-01 BRP (G. Wang) 3/01/2010-3/30/2014 NIH/NHLBI

Optical Molecular Tomography for Regenerative Medicine

Relevant Papers
Whited BM, Whitney JR, Hofmann MC, Xu Y, Rylander MN. Pre-osteoblast infiltration and differentiation in highly porous apatite-coated PLLA electrospun scaffolds. Biomaterials. 2011 Mar; 32(9):2294-304.

Project 2: Stress Preconditioning Strategies for Bone Tissue Regeneration
Graduate Student Researcher: Eunna Chung (graduated)

Bone related disorders associated with cancer, injury, abnormal development, and degenerative conditions dramatically diminish the health and quality of life of millions of people. These disorders can cause significant disability through loss of bone or its functionality, creating a need for bone replacements (over 3 million orthopaedic procedures are performed every year) or effective regenerative strategies. Although tissue engineered bone replacements have enormous potential, development of truly viable and functional tissues is limited by numerous aspects such as cell growth rate and formation of connective tissue surrounding cells, extracellular matrix (ECM). Furthermore, there are no effective strategies for stimulating bone regeneration directly in injured or diseased bone in vivo.

Stress conditioning in the form of thermal, tensile, and shear stress can up-regulate ECM production, cell proliferation, and induction of molecular chaperones known as heat shock proteins (HSPs). A clear link has been shown between up-regulated HSPs and enhanced cell proliferation and collagen biosynthesis. However, tissue engineering approaches have not harnessed the potential of HSPs for creation of more viable bone replacements. Furthermore, delivery of HSPs exogenously to diseased bone regions could have tremendous potential to stimulate bone regeneration. The objective of this study is to investigate a transformative approach for bone replacement and regeneration through heat shock protein-based therapies. This research is utilizing combinatorial stress conditioning strategies involving thermal, tensile, and shear stress and exogenous delivery of HSPs to both cell monolayers and scaffolds.