Abstract
Purpose :
The integrity of the corneal nerves is crucial for an intact ocular surface. Corneal nerve damage or injuries are the main causes of the degenerative disease Neurotrophic Keratopathy (NK) as well as neurogenic dry eye disease, which in severe cases can result in loss of vision due to limited curative treatment options. Despite the regenerative ability of the peripheral nerve system, the regeneration of corneal nerves is often incomplete and the underlying mechanisms are still unknown. Therefore, the aim of this study is to investigate possible new nerve regeneration factors to enhance corneal nerve regeneration as a therapeutic approach for NK. One candidate is Lysophosphatidic acid (LPA), which was found to be enhanced in the tear fluid of patients with Dry Eye Disease and is known for its influence on the central nerve system.
Methods :
The study investigated the effects of LPA on dorsal root ganglion (DRG) cells of 10-12-week-old male C57BL/6 mice. The fiber length of individual neurons (single-cell assay) and the regeneration of injured neurons (wound healing assay) were measured with and without the addition of LPA. Additionally, siRNA experiments were performed to identify the specific LPA receptor (Lpar) responsible for the observed effects of LPA on nerve regeneration. Furthermore, underlying signaling pathways were investigated by qrt-PCR.
Results :
The single-cell assay demonstrated a significant decrease in fiber length in the LPA-treated group (1.03 ± 0.25 µm, P = 0.018) compared to the control (3.22 ± 0.38 µm) after 48 h. However, the neuronal fiber length of LPA-treated neurons after Lpar2 knockdown increased from 2.81 ± 0.34 µm (negative control) to 7.04 ± 1.08 µm, P= 0.038 (Lpar2-knockdown) at 48 h. The wound healing assay exhibited comparable results. LPA-treated neurons exhibited elevated mRNA expression of Lpar2 and 4. Nerve regeneration markers Ngf and Gdnf were upregulated in injured neurons after LPA treatment.
Conclusions :
In conclusion, our study elucidates the inhibitory effects of LPA on fiber outgrowth of sensory neurons. Furthermore, the responsible receptor (Lpar2) for this inhibitory effect of LPA in the neurons was identified by siRNA transfection. These findings may offer a novel curative therapeutic approach by blocking the negative effect of LPA in patients with NK.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.