In vitrobioprinted 3D model enhancing osteoblast-to-osteocyte differentiation

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Cell Biology

Background:

• * In vitro bone models are essential for understanding bone pathologies and testing therapies.
• * Current models lack the ability to replicate osteoblast-to-osteocyte differentiation using primary cells.
• * Achieving realistic mechanical properties and cellular behavior in bio-printed models remains a challenge.

Purpose of the Study:

• * To develop a bio-printed in vitro bone model that accurately captures human primary osteoblast differentiation into osteocytes.
• * To investigate the impact of hydrogel biomechanical properties (stiffness and viscoelasticity) on this differentiation process.

Main Methods:

• * Fabrication of gelatin, alginate, and fibrinogen hydrogels with modulated stiffness and viscoelasticity using transglutaminase and calcium cross-linking.
• * Micro-extrusion bioprinting of primary human osteoblasts within the developed hydrogels.
• * Assessment of cell proliferation, alkaline phosphatase activity, dendrite formation, and osteocyte marker (PHEX) expression.

Main Results:

• * A specific hydrogel formulation (8 kPa elastic modulus, time-dependent viscoelastic behavior) promoted osteoblast-to-osteocyte differentiation.
• * Differentiation was marked by suppressed proliferation, increased alkaline phosphatase activity, dendrite development, and PHEX expression.
• * Cells actively remodeled the hydrogel, showing contraction and collagen I secretion.

Conclusions:

• * A bio-printed in vitro model using primary human osteoblasts successfully achieved osteocyte differentiation, evidenced by specific protein markers.
• * This model offers a significant advancement for studying bone diseases like osteoporosis and bone tumors.
• * The findings highlight the critical role of hydrogel biomechanics in directing cell fate for bone tissue engineering.