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Updated: Jul 16, 2025
Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury
Published on: September 4, 2013
FHL2 regulates microglia M1/M2 polarization after spinal cord injury via PARP14-depended STAT1/6 pathway
Aihua Xu1, Yang Yang1, Yang Shao1
1Department of Rehabilitation Medicine, The First Hospital of China Medical University, Shenyang, Liaoning, China.
Abstract:
Neuronal apoptosis and inflammation exacerbate the secondary injury after spinal cord injury (SCI). Four and a half domains 2 (FHL2) is a multifunctional scaffold protein with tissue- and cell-type specific effects on the regulation of inflammation, but its role in SCI remains unclear. The T10 mouse spinal cord contusion model was established, and the mice were immediately injected with lentiviruses carrying FHL2 shRNA after SCI. The results showed that FHL2 expression was increased following SCI, and then gradually decreased. Moreover, FHL2 depletion aggravated functional impairment, neuronal necrosis, and enlarged lesion cavity areas in the injured spinal cord. FHL2 deficiency facilitated neuronal apoptosis by elevating cleaved caspase 3/9 expression, neuroinflammation by regulating microglia polarization, and bone loss. Indeed, FHL2 deficiency increased the secretion of TNF-α and IL-6, M1 microglia polarization, and the activation of STAT1 pathway but decreased the secretion of IL-10 and IL-4, M2 microglia polarization, and the activation of the STAT6 pathway in the spinal cord. In vitro, FHL2 silencing promoted LPS + IFN-γ-induced microglia M1 polarization through activating the STAT1 pathway and alleviated IL-4-induced microglia M2 polarization via inhibiting the STAT6 pathway. FHL2 positively regulated the expression of poly (ADP-ribose) polymerase family member 14 (PARP14) by promoting its transcription. PARP14 overexpression inhibited FHL2 silencing-induced microglia M1 polarization and relieved the inhibitory effect of FHL2 silencing on microglia M2 polarization. Collectively, the study suggests that FHL2 reduces the microglia M1/M2 polarization-mediated inflammation via PARP14-dependent STAT1/6 pathway and thereby improves functional recovery after SCI.
Insights
Four and a half domains 2 (FHL2) protein deficiency worsens spinal cord injury (SCI) outcomes by increasing inflammation and neuronal apoptosis. FHL2 plays a protective role in SCI by modulating microglia polarization via the PARP14-dependent STAT1/6 pathway, improving functional recovery.
Area of Science:
- Neuroscience
- Immunology
- Regenerative Medicine
Background:
- Spinal cord injury (SCI) involves secondary damage from neuronal apoptosis and inflammation.
- The role of the multifunctional scaffold protein Four and a half domains 2 (FHL2) in SCI pathogenesis is not well understood.
- FHL2 exhibits tissue- and cell-type specific regulatory effects on inflammation.
Purpose of the Study:
- To investigate the role of FHL2 in the secondary injury phase following SCI.
- To elucidate the molecular mechanisms by which FHL2 influences neuroinflammation and neuronal apoptosis after SCI.
- To determine if FHL2 impacts microglia polarization and subsequent functional recovery.
Main Methods:
- Establishment of a T10 mouse spinal cord contusion model.
- In vivo FHL2 knockdown using lentiviral shRNA immediately after SCI.
- In vitro studies involving microglia stimulation (LPS + IFN-γ or IL-4) with FHL2 silencing.
- Assessment of neuronal apoptosis, inflammation markers (cytokines, microglia polarization), STAT pathway activation, and PARP14 expression.
- Evaluation of functional recovery and lesion size.
Main Results:
- FHL2 expression initially increased post-SCI before declining.
- FHL2 depletion aggravated functional deficits, neuronal necrosis, and lesion size.
- FHL2 deficiency enhanced apoptosis (cleaved caspase 3/9), M1 microglia polarization (increased TNF-α, IL-6, STAT1 activation), and bone loss.
- FHL2 deficiency reduced M2 microglia polarization (decreased IL-10, IL-4, STAT6 activation).
- FHL2 positively regulated PARP14 transcription; PARP14 overexpression counteracted FHL2 silencing effects on microglia polarization.
Conclusions:
- FHL2 plays a crucial protective role in mitigating secondary injury after SCI.
- FHL2 ameliorates neuroinflammation by inhibiting M1 microglia polarization and promoting M2 polarization through the PARP14-dependent STAT1/6 pathway.
- Targeting FHL2 may offer a therapeutic strategy to improve functional recovery following spinal cord injury.
