Kidney Week

Abstract: SA-PO149

Role of LTBP4 in Kidney Injury: A Study on the Effect of LTBP4 on Angiogenesis and Inflammation in Renal Fibrosis

Session Information

• AKI: Mechanisms - III
  November 04, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 103 AKI: Mechanisms

Authors

• Su, Chi-Ting, National Taiwan University Hospital, Taipei, Taiwan

Chi-Ting Su,

• See, Daniel H. W., National Taiwan University Hospital, Taipei, Taiwan

Daniel H. W. See,

• Huang, Yue-Jhu, National Taiwan University Hospital, Taipei, Taiwan

Yue-Jhu Huang,

• Huang, Jenq-wen, National Taiwan University Hospital, Taipei, Taiwan

Jenq-wen Huang,

• Hung, Kuan-Yu, National Taiwan University Hospital, Taipei, Taiwan

Kuan-Yu Hung,

Background

Transforming growth factor beta (TGFβ), a key player in renal fibrosis, is regulated by latent transforming growth factor beta binding protein 4 (LTBP4). However, we hypothesized that LTBP4 also plays a role in angiogenesis and inflammation, both TGFβ related and TGFβ independent. This is significant because the role of angiogenesis and inflammation in kidney injury is widely recognized.

Methods

We employed wild-type (WT) and Ltbp4^PTKO-/- [Ltbp4 proximal tubule knockout (PTKO)] mice for our animal experiments. Additionally, we used human proximal tubule cells (HK-2 cells) transfected with LTBP4 lentiviral knockdown for in vitro cellular studies. To induce kidney injury, the mice underwent 30 min of bilateral renal ischemia-reperfusion injury (IRI) surgery. HK-2 cells were subjected to 24 h of hypoxia at 1% O₂, 5% CO₂, and 94% N₂ to simulate pathological kidney injury. Subsequently, molecular studies were conducted on mice kidney samples and HK-2 cells to assess the extent of injury and the expression of proangiogenic molecules and inflammatory cytokines.

Results

Our study demonstrated increased expression of LTBP4 in mice after kidney injury. Fourteen days post-IRI, Ltbp4^PTKO-/- mice showed more pronounced fibrosis than WT mice. Immunohistochemistry analysis revealed stronger positive staining for CD31, an endothelial marker, in WT mice than in Ltbp4^PTKO-/- mice. Moreover, WT mice exhibited higher expression of vascular endothelial growth factor (VEGF) than Ltbp4^PTKO-/- mice after undergoing IRI surgery. Transcriptomic analysis revealed upregulation of genes linked to angiogenesis in LTBP4-overexpressed HK-2 cells. Cellular studies reflected similar results in HK-2 cells, where VEGF expression was lower in LTBP4 knockdown cells. Additionally, inflammatory cytokines were upregulated in Ltbp4^PTKO-/- mice compared with those in WT mice after injury.

Conclusion

Our study findings show that LTBP4 plays a key role in regulating angiogenesis and inflammation during kidney injury. We demonstrated that LTBP4 partly has a protective effect in the progression of kidney disease. The increased angiogenesis and reduction in inflammation aid in the recovery of kidney injury and potentially mitigates long-term complications. These findings highlight the potential therapeutic avenues for utilizing LTBP4 in managing kidney injury.