Focal adhesion kinase activation plays a critical role in the restoration of simulated microgravity-inhibited osteoblast differentiation by triggering transcriptional Wnt/B-Catenin-BMP2-COL1 and metabolic SIRT1-PGC1a-CPT1A pathways

Eric Zhao; Zhaojia Wu; Jim Xiang; Eric Zhao; Zhaojia Wu; Jim Xiang

doi:10.3934/molsci.2026001

AIMS Molecular Science

2026, Volume 13, Issue 1: 1-9. doi: 10.3934/molsci.2026001

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Commentary

Focal adhesion kinase activation plays a critical role in the restoration of simulated microgravity-inhibited osteoblast differentiation by triggering transcriptional Wnt/B-Catenin-BMP2-COL1 and metabolic SIRT1-PGC1a-CPT1A pathways

1.
Research Unit, Saskatchewan Cancer Agency, 20 Campus Drive, Saskatoon, Saskatchewan S7N 4H4, Canada
2.
Division of Oncology, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada

Received: 09 September 2025 Revised: 18 November 2025 Accepted: 25 November 2025 Published: 12 January 2026

Background
Aerospace microgravity (AMG) poses a major threat during spaceflight, impairing osteoblast differentiation (OBD) and causing bone loss. To replicate AMG conditions for ground-based experimental procedures, simulated microgravity (SMG) has been implemented to explore the molecular mechanisms of AMG-induced alterations in osteoblast differentiation. However, SMG's metabolic implications contributing to defective osteoblast differentiation remain unexplored.
Methods
To investigate this, we investigated effects of SMG on pre-osteoblast MC3T3-E1 cells using Western-blotting to analyze expression of metabolic regulators and Seahorse assays to characterize cellular metabolism. The cytotoxic necrotizing factor-1 (CNF1), an activator of focal adhesion kinase (FAK), was applied to assess its ability to modulate SMG-inhibited OBD.
Results
Our results showed that, besides its established inhibition of FAK and the Wnt/β-catenin signaling cascade, SMG also induced a metabolic shift from fatty acid oxidation (FAO) to glycolysis by decreasing mitochondrial content and reducing expression of metabolic regulators [sirtuin-1 (SIRT1), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), and carnitine palmitoyl transferase-1α (CPT1A)] that are critical for mitochondrial biogenesis and FAO capacity. CNF1 exposure was found to counteract the SMG's inhibitory influence by upregulating expression of above metabolic regulators and restoring mitochondrial content and FAO as the primary cellular metabolism and thereby rescuing OBD. Altogether, our findings emphasize that FAK activation plays a critical role in restoration of SMG-inhibited osteoblast differentiation by triggering transcriptional Wnt/B-Catenin-BMP2 (bone morphogenic protein-2)-COL1 (type-1 collagen) and metabolic SIRT1-PGC1a-CPT1A pathways.
Conclusion
Our data shed light on FAK as a potential therapeutic target to mitigate SMG-driven bone-loss for astronauts and attenuate bone defectiveness for clinical osteoporosis.
- Osteoblast metabolism,
- Simulated microgravity,
- FAK,
- CNF-1,
- Wnt/β-catenin,
- BMP2,
- COL1,
- SIRT1,
- PGC-1α,
- CPT1A
Citation: Eric Zhao, Zhaojia Wu, Jim Xiang. Focal adhesion kinase activation plays a critical role in the restoration of simulated microgravity-inhibited osteoblast differentiation by triggering transcriptional Wnt/B-Catenin-BMP2-COL1 and metabolic SIRT1-PGC1a-CPT1A pathways[J]. AIMS Molecular Science, 2026, 13(1): 1-9. doi: 10.3934/molsci.2026001

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Abstract

Background

Aerospace microgravity (AMG) poses a major threat during spaceflight, impairing osteoblast differentiation (OBD) and causing bone loss. To replicate AMG conditions for ground-based experimental procedures, simulated microgravity (SMG) has been implemented to explore the molecular mechanisms of AMG-induced alterations in osteoblast differentiation. However, SMG's metabolic implications contributing to defective osteoblast differentiation remain unexplored.

Methods

To investigate this, we investigated effects of SMG on pre-osteoblast MC3T3-E1 cells using Western-blotting to analyze expression of metabolic regulators and Seahorse assays to characterize cellular metabolism. The cytotoxic necrotizing factor-1 (CNF1), an activator of focal adhesion kinase (FAK), was applied to assess its ability to modulate SMG-inhibited OBD.

Results

Our results showed that, besides its established inhibition of FAK and the Wnt/β-catenin signaling cascade, SMG also induced a metabolic shift from fatty acid oxidation (FAO) to glycolysis by decreasing mitochondrial content and reducing expression of metabolic regulators [sirtuin-1 (SIRT1), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), and carnitine palmitoyl transferase-1α (CPT1A)] that are critical for mitochondrial biogenesis and FAO capacity. CNF1 exposure was found to counteract the SMG's inhibitory influence by upregulating expression of above metabolic regulators and restoring mitochondrial content and FAO as the primary cellular metabolism and thereby rescuing OBD. Altogether, our findings emphasize that FAK activation plays a critical role in restoration of SMG-inhibited osteoblast differentiation by triggering transcriptional Wnt/B-Catenin-BMP2 (bone morphogenic protein-2)-COL1 (type-1 collagen) and metabolic SIRT1-PGC1a-CPT1A pathways.

Conclusion

Our data shed light on FAK as a potential therapeutic target to mitigate SMG-driven bone-loss for astronauts and attenuate bone defectiveness for clinical osteoporosis.

Abbreviations

ALP

alkaline phosphatase

AMG

Aerospace microgravity

AMPK

AMP-activated protein kinase

AQP9

aquaporin-9

BMP2

bone morphogenetic protein-2

CNF1

The cytotoxic necrotizing factor-1

COL1

type I collagen

CPT1A

carnitine palmitoyl transferase-1α

ECAR

extracellular acidification rate

ECM

extracellular matrix

ERK

extracellular signal-regulated kinase

FAK

focal adhesion kinase

FAO

fatty acid oxidation

FAs

Focal adhesions

Hindlimb unloading

IAPs

intracellular adaptor proteins

LEF

lymphoid-enhancing-binding factor

MSCs

mesenchymal stem cells

mTORC1

mechanistic target of rapamycin complex-1

OBD

osteoblast differentiation

OCR

oxygen consumption rate

OXPHOS

oxidative phosphorylation

PGC-1α

peroxisome proliferator-activated receptor-γ coactivator-1α

PPARγ

proliferator-activated receptor-γ

Rho

Ras homolog

RPM

random positional machine

SMG

stimulated microgravity

TCF1

T-cell factor-1

Acknowledgments

This work was supported by a research grant (#421820) from the Natural Sciences and Engineering Research Council of Canada (NSERC) for JX.

Conflict of interest

The authors declare that they have no conflicts of interest in this paper.

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