a-lab-on-chip-platform-for-stimulating-osteocyte-mechanotransduction

A Lab-On-A-Chip Platform for Stimulating Osteocyte Mechanotransduction and Analyzing Functional Outcomes of Bone Remodeling

Bone remodeling is a tightly regulated process that is required for skeletal growth and repair as well as adapting to changes in the mechanical ...

The University of Akron

Researchers have been using lab-on-a-chip systems to isolate factors for study, simulate laboratory analysis and model cellular, tissue and organ level processes. The technology is increasing rapidly, but the bone field has been slow to keep pace. Novel models are needed that have the power and flexibility to investigate the elegant and synchronous multicellular interactions that occur in normal bone turnover and in disease states in which remodeling is implicated. By removing temporal and spatial limitations and enabling quantification of functional outcomes, the platforms should provide unique environments that are more biomimetic than single cell type systems while minimizing complex systemic effects of in vivo models. This manuscript details the development and characterization of lab-on-a-chip platforms for stimulating osteocytes and quantifying bone remodeling. Our platforms provide the foundation for a model that can be used to investigate remodeling interactions as a whole or as a standard mechanotransduction tool by which isolated activity can be quantified as a function of load.

Lab-on-a-chip platforms for quantification of multicellular interactions in bone remodeling.

Bisphosphonate-related osteonecrosis of the jaw is a disease appearing after tooth removal in patients undergoing bisphosphonate treatment for metastasizing cancers and osteoporosis. The complexity of the condition requires a multicellular model to address the net effects of two key risk factors: mechanical trauma (pathologic overload) and inflammation. In this work, a system comprised of a polydimethylsiloxane chip and mechanical loading device is used to expose bisphosphonate-treated osteocytes to mechanical trauma. Specifically, osteocytes are treated with the potent nitrogen-containing bisphosphonate, zoledronic acid, and exposed to short-term pathologic overload via substrate stretch. During bone remodeling, osteocyte apoptosis plays a role in attracting pre-osteoclasts to sites of damage; as such, lactate dehydrogenase activity, cell death and protein expression are evaluated as functions of load. Additionally, the effects of osteocyte soluble factors on osteoclast and osteoblast functional activity are quantified. Osteoclast activity and bone resorption are quantified in the presence and absence of inflammatory components, lipopolysaccharide and interferon gamma. Results suggest that inflammation associated with bacterial infection may hinder bone resorption by osteoclasts. In addition, osteocytes may respond to overload by altering expression of soluble signals that act on osteoblasts to attenuate bone formation. These findings give insight into the multicellular interactions implicated in bisphosphonate-related osteonecrosis of the jaw.

The effects of mechanically loaded osteocytes and inflammation on bone remodeling in a bisphosphonate-induced environment.

Our lab has developed a lab-on-a-chip platform for bone remodeling that enables long-term culturing of bone cells out to 7 weeks and serves as a foundation toward a multicellular organ-on-a-chip system. Here, we optimized culturing protocols for osteoblasts, osteoclasts and osteocytes within the lab-on-a-chip and performed functional activity assays for quantifying bone formation and resorption. We analyzed cell seeding densities, feeding schedules and time in culture as a basis for optimizing culturing protocols. Further, we addressed concerns of sterility, cytotoxicity and leakage during the extended culture period within the polydimethylsiloxane chip. This system provides a method for quantifying the soluble effects of mechanically stimulated osteocytes on bone remodeling (formation/resorption).

Cellular considerations for optimizing bone cell culture and remodeling in a lab-on-a-chip platform.

The purpose of this paper is to emphasize the need for more complex bone remodeling platforms that allow for investigations of intricate multicellular interactions that regulate this process. We discuss the efforts we have taken to develop lab-on-a-chip systems for bone remodeling and the motivation for pursuing more advanced multicellular models. Further, we discuss mathematical modeling opportunities that will allow experimental results to extend beyond the set laboratory conditions. We advocate for the development of an agent-based model comprised of multiple cellular automata of each bone cell type. In total, this work requires a combination of techniques from bone biology, microfluidics, cell mechanobiology, mechanics, and mathematical modeling. Thus, significant advancements within the field will require a collective contribution from a variety of research laboratories.

Article	Year
Lab-on-a-chip platforms for quantification of multicellular interactions in bone remodeling. Experimental cell research\| PubMed ID: 29499205	2018
The effects of mechanically loaded osteocytes and inflammation on bone remodeling in a bisphosphonate-induced environment. Bone\| PubMed ID: 31301402	2019
Cellular considerations for optimizing bone cell culture and remodeling in a lab-on-a-chip platform. BioTechniques\| PubMed ID: 32146829	2020
Bone remodeling platforms: Understanding the need for multicellular lab-on-a-chip systems and predictive agent-based models. Mathematical biosciences and engineering : MBE\| PubMed ID: 32233577	2019

Sharon L. Truesdell

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