Abstract
We and others have published on the rapid manufacture of micropellet tissues, typically formed from 100–500 cells each. The micropellet geometry enhances cellular biological properties, and in many cases the micropellets can subsequently be utilized as building blocks to assemble complex macrotissues. Generally, micropellets are formed from cells alone, however when replicating matrix-rich tissues such as cartilage it would be ideal if matrix or biomaterials supplements could be incorporated directly into the micropellet during the manufacturing process. Herein we describe a method to efficiently incorporate donor cartilage matrix into tissue engineered cartilage micropellets. We lyophilized bovine cartilage matrix, and then shattered it into microscopic pieces having average dimensions < 10 μm diameter; we termed this microscopic donor matrix “cartilage dust (CD)”. Using a microwell platform, we show that ~0.83 μg CD can be rapidly and efficiently incorporated into single multicellular aggregates formed from 180 bone marrow mesenchymal stem/stromal cells (MSC) each. The microwell platform enabled the rapid manufacture of thousands of replica composite micropellets, with each micropellet having a material/CD core and a cellular surface. This micropellet organization enabled the rapid bulking up of the micropellet core matrix content, and left an adhesive cellular outer surface. This morphological organization enabled the ready assembly of the composite micropellets into macroscopic tissues. Generically, this is a versatile method that enables the rapid and uniform integration of biomaterials into multicellular micropellets that can then be used as tissue building blocks. In this study, the addition of CD resulted in an approximate 8-fold volume increase in the micropellets, with the donor matrix functioning to contribute to an increase in total cartilage matrix content. Composite micropellets were readily assembled into macroscopic cartilage tissues; the incorporation of CD enhanced tissue size and matrix content, but did not enhance chondrogenic gene expression.
Highlights
A gradient in particle size was observed in cartilage dust (Fig 1A), and overall size distribution graph indicated that particle size was mainly less than 10 μm (Fig 1B)
The smaller particles tend to rapidly lose both the unwanted residual DNA as well as leach the desired sulfated glycosaminoglycan (sGAG) molecules. The release of both DNA and sGAG increases proportionally to the increased surface area to volume ratio that occurs as the particle diameter is reduced. This phenomenon was noted nearly three decades ago; at the time pulverizing cartilage into microparticles was done purposefully to enhance the extraction of sGAG from cartilage [21]
Composite micropellets self-assembled into structures with a core of cartilage dust (CD), and a cellular surface that facilitated the bridging of micropellets into macrotissues when they were in contact with each other
Summary
Cartilage injuries often further degenerate rather than healing spontaneously. The tendency to degenerate makes osteoarthritis (OA) the leading cause of pain and disability in developed nations [1,2,3,4]. The repair of osteoarthritic lesions is not possible and joint replacements are the only surgical interventions that successfully restore OA joint function [5]. Surgical repair of acute cartilage injuries and delayed onset of OA is possible to a limited extent. A range of surgical methodologies has been developed and the most promising methods utilize cell-based tissue engineering approaches
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
