Pulsating fluid flow affects pre‐osteoblast behavior and osteogenic differentiation through production of soluble factors

• Published in: Physiological reports Vol. 9; no. 12; pp. e14917 - n/a
• Main Authors: Jin, Jianfeng, Seddiqi, Hadi, Bakker, Astrid D., Wu, Gang, Verstappen, Johanna F. M., Haroon, Mohammad, Korfage, Joannes A. M., Zandieh‐Doulabi, Behrouz, Werner, Arie, Klein‐Nulend, Jenneke, Jaspers, Richard T.
• Format: Journal Article
• Language: English
• Published: United States John Wiley & Sons, Inc 01-06-2021; John Wiley and Sons Inc
• Subjects: Actin; Actins - metabolism; Actins - physiology; Alkaline phosphatase; Alkaline Phosphatase - metabolism; Animals; Bone growth; Bone mass; Boundary conditions; Cbfa-1 protein; Cell Differentiation - physiology; Cell Line; Collagen; Collagen - metabolism; Computer applications; Cytoskeleton; Fibroblast growth factor 2; Fibroblasts; Finite Element Analysis; finite element modeling; Fluid dynamics; Fluid flow; F‐actin stress fiber; Gene Expression; Growth factors; Mechanical loading; Mechanical stimuli; Metabolism; Mice; Mineralization; Morphology; Nitric oxide; Nitric Oxide - metabolism; Original; Osteoblastogenesis; Osteoblasts; Osteoblasts - metabolism; Osteoblasts - physiology; Osteocytes; Osteogenesis; Osteogenesis - physiology; osteogenic differentiation; Physiology; pre‐osteoblast; Pseudopodia; Pulsatile Flow - physiology; Shear stress; finite element modeling; fluid dynamics; osteogenic differentiation; pre-osteoblast; F-actin stress fiber
• ISSN: 2051-817X
• DOI: 10.14814/phy2.14917

Bone mass increases after error‐loading, even in the absence of osteocytes. Loaded osteoblasts may produce a combination of growth factors affecting adjacent osteoblast differentiation. We hypothesized that osteoblasts respond to a single load in the short‐term (minutes) by changing F‐actin stress fiber distribution, in the intermediate‐term (hours) by signaling molecule production, and in the long‐term (days) by differentiation. Furthermore, growth factors produced during and after mechanical loading by pulsating fluid flow (PFF) will affect osteogenic differentiation. MC3T3‐E1 pre‐osteoblasts were either/not stimulated by 60 min PFF (amplitude, 1.0 Pa; frequency, 1 Hz; peak shear stress rate, 6.5 Pa/s) followed by 0–6 h, or 21/28 days of post‐incubation without PFF. Computational analysis revealed that PFF immediately changed distribution and magnitude of fluid dynamics over an adherent pre‐osteoblast inside a parallel‐plate flow chamber (immediate impact). Within 60 min, PFF increased nitric oxide production (5.3‐fold), altered actin distribution, but did not affect cell pseudopodia length and cell orientation (initial downstream impact). PFF transiently stimulated Fgf2, Runx2, Ocn, Dmp1, and Col1⍺1 gene expression between 0 and 6 h after PFF cessation. PFF did not affect alkaline phosphatase nor collagen production after 21 days, but altered mineralization after 28 days. In conclusion, a single bout of PFF with indirect associated release of biochemical factors, stimulates osteoblast differentiation in the long‐term, which may explain enhanced bone formation resulting from mechanical stimuli.
Pulsating fluid flow has distinct temporal impact on pre‐osteoblast behavior and osteogenic differentiation. Initially, PFF increased nitric oxide production, followed in the short‐term by F‐actin stress fiber changes. In the long‐term, PFF did not enhance collagen production, but increased mineralization. This indicates that a single bout of mechanical loading, triggering release of soluble factors, stimulates mineralization in the long‐term.