Dr. Anne Bernhardt (Dresden, DE), Katharina Wirsig (Dresden, DE), Aylin Kara (Dresden, DE), Liu Suihong (Dresden, DE), Professor Michael Gelinsky (Dresden, DE)
Abstract text (incl. figure legends and references)
Introduction
Bioprinting is a versatile method to generate spatially arranged tissue models. Since osteocytes (ocy) are the most abundant bone cell species, in vitro bone models should include not only osteoblasts and their precursors, but also ocy.
Objectives
The aim of the study was to differentiate primary human ocy in bioprinted constructs. Suitable ink formulations and media supplements needed to be tested to find suitable conditions for cell attachment, spreading and differentiation.
Methods
Human osteoblasts (hOB) were expanded and bioprinted (Bioscaffolder 3.1. Gesim) using three different alginate-based inks: alginate (alg)/methylcellulose(MC)/human plasma, alg/MC/egg white and alg/MC/gelatin. After printing and cross-linking, constructs were cultivated for up to 14d. Different media with varying serum content were tested. Ocy morphology and gene expression of ocy markers were analyzed.
Results
Osteoblasts were viable after both printing and cultivation in all examined inks. The cells showed dendritic ocy morphology after cultivation under low serum conditions. While early ocy markers (E11, BGLAP) were already expressed after 7 d, late ocy marker expression was significantly enhanced after 14 d of differentiation. This is in accordance to the more pronounced ocy morphology at d14.
Conclusions
The application of primary human ocy, directly isolated from bone, is not feasible for bioprinting applications, since very high cell numbers are required. After bioprinting of primary hOB, their differentiation to ocy was achieved for the first time. The applied inks supported ocy differentiation, providing a suitable microenvironment for the formation of dendrites. The generation of a 3D printed ocy network offers the opportunity to establish a biomimetic in vitro bone model with spatially arranged bone cells.
Fig.1: Morphology (d14, scale 100 µm) and gene expression of ocy differenciated from hOB bioprinted in scaffolds from alg/MC/human plasma ink