Indirect Application of Intense Pulsed Light Induces Therapeutic Effects on Experimental Murine Meibomian Gland Dysfunction

Diurnal rhythm-modulated transcriptome analysis of meibomian gland in hyperlipidemic mice using RNA sequencing

AIM

To explore the regulatory mechanism of meibomian gland (MG) in hyperlipidemic mice under a diurnal rhythm by transcriptomic analysis based on high-throughput sequencing.

METHODS

The mouse model of hyperlipidemia induced by four months of high-fat diet (HFD) feeding to a regular light-dark (LD) cycle for 2 weeks was used in this study. Phenotypic observation and RNA sequencing (RNA-seq) of MGs of the experimental mice were then performed to investigate transcriptional changes due to hyperlipidemia and the diurnal rhythm and their effects on meibomian gland dysfunction (MGD).

RESULTS

The expression levels of the identified dysregulated genes were then validated by qRT-PCR. Several significantly regulated genes and enriched pathways were identified as associated with MGD in hyperlipidemic mice under a diurnal rhythm; these genes included some core diurnal clock genes, e.g., Clock, Per2 and Per3. Phenotypic and histological analysis reveals abnormal morphology concomitantly with a modification of the transcriptional landscape of MG caused by HFD.

CONCLUSION

Our findings provide us with a deeper understanding of the diurnal rhythm regulation of MG in hyperlipidemic mice altered by daily nutritional challenge.

Effects of Intense Pulsed Light on Presumed Neuropathic Pain Associated with Meibomian Gland Dysfunction: A Before-After Study

Purpose: Meibomian gland dysfunction (MGD) may cause chronic ocular surface pain (COSP) with a neuropathic component that can significantly impact quality of life and be poorly responsive to conventional treatments of MGD. Intense pulsed light (IPL) is an emerging treatment already acknowledged as improving refractory MGD, potentially modulating inflammatory mediators on the ocular surface. This study aimed to assess the impact of IPL on COSP associated with unresponsive MGD. Methods: A monocentric prospective study has been conducted from 2021 to 2023 on patients presenting with moderate MGD and COSP non-responsive to conventional treatments of MGD. Neuropathic pain components were suspected when severe discomfort (OSDI score above 33/100) was observed despite moderate objective signs. Three sessions of IPL were performed at a two-week interval. The primary outcome was change in OSDI at day 60. Secondary outcomes included OSDI modification at D120, DEQ-5, and Pentascore results at D60/D120, together with changes in clinical [Schirmer I, Fluorescein Break-up time (BUT), fluorescein staining, and MGD classification] and paraclinical tests [noninvasive BUT, tear meniscus height (TMH), and meibography]. Results: A significant improvement of COSP (p < 0.05 for changes in OSDI and Pentascore results) was observed 2 and 4 months after the last IPL session, together with an improvement in tear film stability, corneal epitheliopathy, meibomian gland obstruction, and TMH. Conclusion: The results of this study suggest the beneficial effect of IPL on neuropathic component of COSP associated with MGD. The underlying mechanisms involved in that improvement, presumably related to downgrading of inflammatory effectors, remain however to be explored.

Efficacy of indirect intense pulsed light irradiation on meibomian gland dysfunction: a randomized controlled study

AIM

To investigate the efficacy and mechanisms of indirect intense pulsed light (IPL) irradiation on meibomian gland dysfunction (MGD).

METHODS

A total of 60 MGD patients was included in this prospective randomized controlled trial. Patients were randomly assigned 1:1 into two groups (3-mm group and 10-mm group) in which IPL was applied at distances from the lower eyelid margin of 3 and 10 mm, respectively. Both groups received three times treatment with 3-week interval. Meibomian gland yield secretion score (MGYSS), standard patient evaluation of eye dryness (SPEED) questionnaire, tear break-up time (TBUT), corneal fluorescein staining (CFS), and in vivo confocal microscopy were performed at baseline and after every treatment.

RESULTS

After three IPL treatments, both groups had significant improvement in MGYSS (both P<0.05). The non-inferiority test showed that improvement in 10-mm group was not inferior to that in 3-mm group (P<0.001). In both groups, temporal regions of both upper and lower eyelids showed significant improvement in MGYSS. Scores of SPEED questionnaire in both groups declined significantly (both P<0.001) and changes of SPEED had no difference between two groups (P=0.57). Density of central corneal subepithelial nerves and TBUTs showed no statistically significant changes. The 3-mm group had improvement on corneal fluorescein staining (P=0.048) and meibomian gland morphology (acini wall thickness P=0.003, hyperreflective points P=0.024) while the 10-mm group had not.

CONCLUSION

The efficacy of IPL indirect irradiation in improving meibomian gland secretion and alleviating dry eye symptoms remains unchanged with increase in treatment distance. IPL may primarily act on the functional improvement of the meibomian glands and corneal nerves.

The photothermal effect of intense pulsed light and LipiFlow in eyelid related ocular surface diseases: Meibomian gland dysfunction, Demodex and blepharitis

The treatment and management of ocular surface diseases have shifted towards a co-treatment approach focusing on overall ocular surface homeostasis. When treating issues related to the eye, it is essential to not only focus on the damaged or disabled areas but also consider the larger picture. Meibomian gland dysfunction (MGD), Demodex infection, and blepharitis all interact at the eyelid site and can cause damage to the ocular surface to varying degrees. Palpebral lesions disrupt the balance of ocular surface homeostasis, leading to dry eye and keratitis. Traditional treatments, such as manual physical hot compress massage, have limited effectiveness due to the structure of the eyelid. However, intense pulsed light (IPL) technology uses penetrating light energy to generate heat energy, which can eliminate inflammation of capillaries or kill Demodex. Additionally, the LipiFlow thermal effect and physical compression provide a more vital and longer-lasting therapeutic effect on MGD by excluding other primary causes of ocular surface inflammation. Therefore, personalized treatment techniques based on photothermal effects may be effective. In the future, IPL and LipiFlow may potentially dismiss immune-inflammation factors causing ocular surface disease or block the delivery of systemic immune-related diseases.

Cellular senescence promotes meibomian gland dysfunction in a chronic graft-versus-host disease mouse model

PURPOSE

Aging is a well-established risk factor for meibomian gland dysfunction (MGD). We previously reported an accelerated cellular senescence phenomenon in the lacrimal glands of a murine model of chronic graft-versus-host disease (cGVHD). Herein, we aimed to elucidate the relationship between cellular senescence and MGD in cGVHD mice, utilizing the senolytic agent ABT-263.

METHODS

A cGVHD mouse model was established through allogeneic bone marrow transplantation (BMT) from B10.D2 to BALB/c mice. Subsequently, cGVHD mice were treated with either ABT-263 or vehicle. The eyelids of recipients were analyzed at 4-week intervals post-BMT in both groups.

RESULTS

Meibomian gland (MG) area was significantly smaller in cGVHD mice than in syngeneic control mice. ABT-263-treated mice retained a significantly larger MG area than their vehicle-treated counterparts. Pathological and immunohistochemical examinations revealed significant reductions in eyelid tissue inflammation and pathological fibrosis in the ABT-263 group compared to that in the vehicle-treated group. Additionally, expression of DNA damage markers, senescent cell markers, and senescence-associated secretory phenotype (SASP) factors was elevated in the eyelids of cGVHD mice compared with that in syngeneic mice. The expression of these cellular senescence-associated molecules was considerably suppressed in ABT-263-treated eyelids compared to that in vehicle-treated ones.

CONCLUSIONS

Cellular senescence, along with expression of SASP factors, exhibited increased activity in the eyelids, particularly in the MGs of cGVHD mice. ABT-263 mitigated the severity of MGD. These findings highlight the potential of targeting cellular senescence as an effective approach for MGD treatment in cGVHD.