Micro-vesicles from mesenchymal stem cells over-expressing miR-34a inhibit transforming growth factor-b1-induced epithelial-mesenchymal transition in renal tubular epithelial cells in vitro

0
0
0

Micro-vesicles from mesenchymal stem cells over-expressing miR-34a inhibit transforming growth factor-b1-induced epithelial-mesenchymal transition in renal tubular epithelial cells in vitro

Chronic kidney disease (CKD) affects over 10% of the global population, and its progression to kidney failure is often driven by fibrosis—a scarring process that damages renal tissue. For years, scientists have sought ways to stop or reverse this fibrosis, and recent research points to a promising tool: micro-vesicles (MVs) from mesenchymal stem cells (MSCs), tiny particles that carry molecular signals for tissue repair.

One challenge in using microRNAs (miRNAs)—small gene-regulating molecules—to treat kidney disease is getting them to the right cells. MVs act as natural “delivery trucks” for miRNAs, making them ideal for targeted therapy. Building on prior work showing MSC-derived MVs reduce kidney injury in mice, researchers at Xijing Hospital’s Department of Nephrology (Fourth Military Medical University, China) tested whether MVs loaded with an anti-fibrotic miRNA, miR-34a, could better fight fibrosis in kidney cells.

How the Study Worked

The team isolated MSCs from mouse bone marrow, confirmed their identity (positive for the stem cell marker CD105, negative for blood cell markers like CD45 and CD11b), and showed they could differentiate into bone (via Alizarin Red staining) or fat (via Oil Red O staining)—hallmarks of multipotent MSCs. They then used lentiviruses to make these MSCs overproduce miR-34a, a miRNA known to suppress fibrosis by targeting genes linked to scarring. MVs were collected from these modified MSCs and from unmodified “control” MSCs for comparison.

Next, they tested the MVs on human renal tubular cells (HK-2 cells) treated with transforming growth factor-beta 1 (TGF-b1)—a protein that drives fibrosis by triggering epithelial-mesenchymal transition (EMT). EMT is a process where kidney epithelial cells lose their structured, barrier-like identity and become mesenchymal cells, which produce excess scar tissue. The team measured:

  • Cell survival (via MTT assay),
  • Apoptosis (cell death, via Annexin V-Light 650/propidium iodide),
  • EMT markers (e.g., E-cadherin and TJP1 for epithelial cells; a-SMA and fibronectin for mesenchymal cells) using Western blotting and immunofluorescence,
  • Notch-1/Jagged-1 signaling—a pathway linked to EMT that miR-34a is predicted to target.

Key Findings

  1. MiR-34a Loading Worked: MVs from miR-34a-modified MSCs had 3x more miR-34a than control MVs, confirming successful loading.

  2. Stronger Anti-Fibrotic Effects: TGF-b1 drastically reduced epithelial markers (E-cadherin dropped to 37% of normal; TJP1 to 31%), but miR-34a-enriched MVs restored them to 70% and 62%, respectively. Conversely, TGF-b1 increased mesenchymal markers (a-SMA by 3.9x; fibronectin by 5x), but miR-34a MVs cut these to 2x and 1.7x—more effectively than control MVs.

  3. Targeted the Notch Pathway: TGF-b1 activated Notch-1 (3.4x increase) and Jagged-1 (5x increase)—proteins that drive EMT. MiR-34a MVs reversed these increases to 1.3x and 1.2x, respectively—better than control MVs. To confirm this link, the team forced HK-2 cells to overexpress Jagged-1; this weakened the anti-fibrotic effects of miR-34a MVs, proving the Notch-1/Jagged-1 pathway is key to miR-34a’s action.

  4. Survival vs. Apoptosis: Both modified and control MVs improved HK-2 cell survival, but miR-34a MVs were slightly less effective (control: 1.3; TGF-b1: 0.6; control MVs: 1.1; miR-34a MVs: 0.9). Similarly, TGF-b1 raised apoptosis to 23.3%, while control MVs cut it to 9.4% and miR-34a MVs to 17.4%. The team suspects this is because miR-34a can promote apoptosis by targeting Bcl-2, a protein that keeps cells alive.

What This Means for Kidney Disease

This study builds on growing evidence that MSC-derived MVs are powerful tools for kidney repair—and that genetically modifying MVs to carry anti-fibrotic miRNAs boosts their effectiveness against fibrosis. The biggest takeaway: MiR-34a works by shutting down the Notch-1/Jagged-1 pathway, which TGF-b1 uses to drive EMT. While miR-34a slightly reduced the MVs’ survival benefits, its stronger anti-fibrotic effect makes it a promising candidate for treating CKD, where fibrosis is the main driver of kidney failure.

Of course, more research is needed. MiR-34a can accelerate MSC aging (by targeting Sirtuin 1), and the team plans to test these MVs in live animals with kidney fibrosis. But the results are exciting: By using MVs as natural delivery vehicles for anti-fibrotic miRNAs, scientists are one step closer to a cell-free therapy for CKD—one that could slow or stop the scarring that leads to kidney failure.

This research was published in the Chinese Medical Journal in 2020 by Juan He, Ya-Li Jiang, Yan Wang, Xiu-Juan Tian, and Shi-Ren Sun (Department of Nephrology, Xijing Hospital, Fourth Military Medical University, Xi’an, Shaanxi 710032, China).

doi.org/10.1097/CM9.0000000000000720

Was this helpful?

0 / 0