Photodynamique therapy relieves tumor vascular anergy and promotes immune cell trafficking in an orthotopic mouse model of malignant pleural mesothelioma

Objective

Malignant pleural mesothelioma (MPM) is a deadly disease with limited treatment options. Recently, dual immune checkpoint inhibition therapy (ICI) showed improved patient survival. However, only a fraction of patients were responsive to immunotherapy. One potential mechanism of MPM resistance to ICIs could be their endothelial anergy that hampers leukocyte trafficking to the tumor bulk. Here, we hypothesized that vascular-targeted low dose photodynamic therapy (L-PDT), treatment of MPM could relieve tumor endothelial anergy and improve immunotherapy efficacy.

Methods

Using an orthotopic syngeneic MPM murine model (AB12 cells injected in the pleura of BALB/c mice), we determined the impact of L-PDT on the endothelial expression of E-Selectin, a key molecule involved in leukocyte diapedesis by immunohistochemistry. Furthermore, to confirm the role of E-selectin, we determined the extravasation of effector T cells (CD8+/CD4+) by immunostaining in L-PDT treated tumors in the presence or absence of an E-selectin blocking antibody. Finally, we assessed tumor growth/survival of our MPM murine model treated with L-PDT alone or combined to ICIs.

Results

L-PDT pre-treatment enhanced MPM endothelial E-Selectin expression in vivo. The latter was associated with increased CD4+ and CD8+ lymphocyte infiltration of MPM following L-PDT which did not occur after E-Selectin blockade. Also, L-PDT pre-treatment of MPM influenced favorably tumor control, mouse survival and the impact of ICIs compared to controls.

Conclusion

L-PDT pre-treatment relieves endothelial anergy in MPM which improves antitumor immunity and response to ICI. This approach could constitute a promising pre-treatment option, in combination with ICIs, for the management of this deadly disease.

Baseline brain function in the preadolescents of the ABCD Study

The Adolescent Brain Cognitive Development (ABCD) Study® is a 10-year longitudinal study of children recruited at ages 9 and 10. A battery of neuroimaging tasks are administered biennially to track neurodevelopment and identify individual differences in brain function. This study reports activation patterns from functional MRI (fMRI) tasks completed at baseline, which were designed to measure cognitive impulse control with a stop signal task (SST; N = 5,547), reward anticipation and receipt with a monetary incentive delay (MID) task (N = 6,657) and working memory and emotion reactivity with an emotional N-back (EN-back) task (N = 6,009). Further, we report the spatial reproducibility of activation patterns by assessing between-group vertex/voxelwise correlations of blood oxygen level-dependent (BOLD) activation. Analyses reveal robust brain activations that are consistent with the published literature, vary across fMRI tasks/contrasts and slightly correlate with individual behavioral performance on the tasks. These results establish the preadolescent brain function baseline, guide interpretation of cross-sectional analyses and will enable the investigation of longitudinal changes during adolescent development.

Is faster better? Impact of operative time on postoperative outcomes after VATS anatomical pulmonary resection

Objective

Video-Assisted Thoracic Surgery (VATS) is now the preferred approach for standard anatomical pulmonary resections. However, operative time (OT) for this technique is correlated to many aspects, such as the surgical complexity or the surgeon’s experience and skills. The aim of this study was to identify the factors associated with prolonged OTs and to assess the impact of OT on the development of post-operative complications after VATS anatomical pulmonary resections.

Methods

Retrospective monocentric study including all consecutive patients undergoing a VATS anatomical pulmonary resection for benign or malignant lesions between January 2010 and December 2019. Postoperative outcomes were compared between short (<150 minutes) and long (≥150 minutes) OTs. A multivariate analysis was carried out to identify predictors of longer OTs and post-operative complications.

Results

A total of 836 patients underwent a VATS anatomical pulmonary resection for malignant (n = 767, 91.7%) or benign (n = 69, 8.3%) lesions. Lobectomies were performed in 555 (66.4%), segmentectomies in 250 (29.9%), sleeve lobectomies in 16 (1.9%), bilobectomies in 11 (1.3%) and pneumonectomy in 4 (0.5%) patients. The conversion rate to thoracotomy was 7.7%. Of those 836 patients, 495 (59.2%) were operated within 150 minutes. During the 30-postoperative day period, the overall morbidity was significantly lower in the short OT group (29.1% vs. 40.5%; p = 0.001). Both the duration of drainage (3 vs. 4 days; p < 0.00001) and the length of hospital stay (6 vs. 7 days; p < 0.00001) were significantly reduced in the short OT group. Two predictors of long OT were identified on multivariate analysis: male sex (OR 1.41, p = 0.04) and neoadjuvant chemotherapy (OR 3.46, p = 0.003). A long OT was identified as an individual predictor of postoperative complications (OR 1.84, p < 0.0001).

Conclusion

A prolonged OT is an individual risk factor for postoperative complications in patients undergoing VATS anatomical pulmonary resection.

Intrapleural hyperthermic chemotherapy induces pro-immunogenic e-selectin expression in the vasculature of malignant pleural mesothelioma

Objective

Malignant pleural mesothelioma (MPM) is a deadly disease with dismal prognosis. Prior studies combining surgery with intrapleural hyperthermic chemotherapy (IPHC) have shown improved survivals in selected patients with MPM. However, the mechanisms by which IPHC acts on MPM and its microenvironment remains unknown. Here we focus on tumor endothelial adhesion molecule expression patterns.

Methods

First, we determined the impact of IPHC on MPM tumor and vascular compartments in vitro using a novel bioincubater for hyperthermic cell culture. The cytotoxicity of normo (37 °C) / hyperthermic (42 °C for 60 minutes) cisplatin/carboplatin therapies were evaluated on four MPM (MSTO211H, H-Meso, AE17 and AB12) and one endothelial (EC-RF24) cell lines at a minimum of 24 hours using a presto-blue assay. Second, we treated endothelial cells with IPHC (60 min, 42 °C at optimized cytotoxic concentrations) and determined its impact on pro-immunogenic adhesion molecule (E-selectin, VE-cadherin, VCAM and Connexin-43) expression at 24 hours by Western blot.

Results

Tumor and endothelial cell viability decreased with increasing doses of both chemotherapeutics but was not affected by hyperthermia (IC50 with or without hyperthermia of each cell line at 24 hours reported in Figure 1A). Interestingly, endothelial cell line IC50 was much higher than that of MPM tumor cells for both chemotherapeutics (Figure 1A). Pro-immunogenic adhesion molecule E-Selectin was increased at 24 hours by IPHC with both chemotherapeutics while VE-Cadherin, VCAM and Connexin-43 were not affected (Figure 1B).

Conclusion

Hyperthermia adds no cytotoxicity to intrapleural chemotherapy. However, IPHC favors pro-immunogenic endothelial E-selectin expression. The latter could help induce patient immunity against their MPM and improve survival. Confirmation of these findings in vivo is mandatory.

Objective performance assessment on trainees of a VATS simulation program: A prospective single center study

Objective

A prospective single center study to assess the objective impact on motion performance of a VATS simulation program on thoracic surgery trainees.

Methods

We developed a 6-month VATS simulation training program including exercises of progressive complexity on 3 different black box simulators: a 2D and 3D lobectomy model (Stupnik®) and a 3D perfused lobectomy model (Crabtree®). Between November 2019 and 2020, all consecutive thoracic surgery residents (study group) were prospectively enrolled in this weekly training program that was supervised by a board certified thoracic surgeon. We compared an objective performance evaluation of the study group before and after the training program by assessing movement parameters (distance in cm, time in sec) and absence of shock/extreme motion (%) on 3 simple standardized thoracoscopic exercises (peg placement on a board, rope insertion in loops and precision circle cutting) using the Simball®. Also, we determined the objective performance 6 months apart of 5 final year medical students (unexperienced controls) that were not trained.

Results

There were 7 residents (2 female and 5 male, median age: 29 [range: 26-34] years) who completed the 6-month VATS simulation training program. Five residents were in their first year while two had >3 year experience. The study group's objective performance improved significantly for all three movement parameters in all standardized exercises (Figure 1) after the training program. The objective performance of the unexperienced control group was comparable to the study group before training, but it remained unchanged at 6 months (p > 0.05). When comparing unexperienced and advanced residents, we observed that the training program had more impact on improving the performance for unexperienced residents (p < 0.05).

Conclusion

This study suggests that the implementation of a VATS simulation training program improves the objective performance of trainees compared to controls. Such programs could be interesting adjuncts for residents.

VE/VCO2 slope predicts short- and long-term outcome after anatomical pulmonary resection by VATS

Objective

The ventilation-to-carbon dioxide output (VE/VCO2) slope could predict morbidity and mortality after lung resection. The aim of the study was to identify whether VE/VCO2 slope obtained from cardiopulmonary exercise test (CPET) was an independent predictor of cardiopulmonary complications after anatomical pulmonary resection by video-assisted thoracic surgery (VATS).

Methods

We reviewed the files of all consecutive patients that underwent pulmonary anatomical resections by VATS between January 2010 and October 2020. The data were extracted from the registry of the Centre for Thoracic Surgery of Western Switzerland. Pneumonectomies were excluded from the study. We used a multivariable Cox regression to investigate the risk of cardiopulmonary complications associated with the VE/VCO2 slope and other possible confounders, including the Charlson Comorbidity Index (CCI), the CPET data and pulmonary functions.

Results

In total, 1392 patients (mean age: 66±11 years; ratio female: 47%) underwent anatomical resection by VATS. CPET was performed in 204 patients (15%). However, the VE/VCO2 slope data were available in 145 patients, which were included for the analysis. Patients underwent segmentectomies (N = 42) and lobectomies (N = 101) mainly for lung cancer (96%). The average percentage of the predicted VO2max was of 70±17%. Maximal effort during the CPET (respiratory coefficient ratio >1.1) was not reached in 30% of patients, without impact on the VE/VCO2 slope (39±6 vs 37±7, P = 0.21). Cardiopulmonary complications appeared in 32% of patients with no mortality at 90 days. In the multivariate analysis, VE/VCO2 slope >35 was correlated with cardiopulmonary complications (OR 3.5, 95% CI [1.3-9.3], P = 0.012). CCI, pulmonary functions, peak VO2 and the extension of the anatomical resection was not associated with cardiopulmonary complications.

Conclusion

VE/VCO2 slope above 35 predicts postoperative cardiopulmonary complications in anatomical resections by VATS. The VE/VCO2 slope is independent of the intensity of effort during the CPET. The impact of prehabilitation on the slope should be determined.

[Pheochromocytomas and paragangliomas in pregnancy: About four cases and key messages on management]

OBJECTIFS

The diagnosis of a pheochromocytoma or paraganglioma secreting during pregnancy is a rare and serious situation, involving maternal-fetal prognosis. The purpose of this case series is to discuss the management of these patients.

METHODS

This is a retrospective study of cases of pheochromocytoma (n=2) or paraganglioma (n=2) managed during pregnancy between 2013 and 2020 in one center (Lille, France).

RESULTS

We report four cases of patients with a diagnosis of pheochromocytoma or paraganglioma during pregnancy, at respectively 4, 28, 31 and 34 weeks of amenorrhea (AS). Their pregnancies were affected by a sudden onset of hypertension sometimes associated with headaches, sweating, and palpitations. All patients delivered by Caesarean section after calcium channel blocker impregnation, with a good outcome. Tumor removal took place at a distance from delivery for each patient.

CONCLUSIONS

The therapeutic strategy includes antihypertensive treatment with calcium channel blockers or alphablockers and surgical curative treatment linked to gestational age. Multidisciplinary management as well as early diagnosis can improve the maternal-fetal prognosis. The preferred way of delivery is Caesarean section, but vaginal delivery can also be considered. Removal should ideally take place at a distance from the birth. The analysis of these cases has led to the development of a protocol for monitoring and management of parturients with diagnosis of pheochromocytoma or paraganglioma during pregnancy.

508 Conservative Management of Small Bowel Obstruction: A Local Experience

Introduction

Post-operative intra-abdominal adhesions remain the leading cause of small bowel obstruction (SBO) representing one of the main diagnoses warranting emergency laparotomies. The National Audit in Small Bowel Obstruction advocates the use of water-soluble contrast agents (WSCA) as initial management of SBO. We aim to assess the role and outcomes of WSCA and its rate in successfully managing SBO non-operatively.

Method

We conducted a 2-year retrospective analysis including all patients admitted with adhesive SBO. Outcomes of patients who received WSCA were compared to those who hadn’t.

Results

118 patients were included, 27(23%) of which required immediate surgery while 91(77%) were initially managed conservatively. From the latter group, 53(58.2%) received WSCA whilst 38(41.8%) didn’t. Of the group that received WSCA, 36(39.5%) were successfully managed non-operatively, compared to 26(28.5%) that didn’t, this however lacked statistical significance. LOS didn’t differ between these two groups (5 days vs. 5.5 days, p = 0.805). 32% of the patients required eventual surgical intervention needing longer LOS regardless of receiving WSCA (6.6 days vs. 13.6 days p < 0.001).

Conclusions

Adhesive SBO can be managed conservatively in up to two-thirds of patients. WSCA usage has a positive impact but needs further assessment in larger studies.

Pathological response and tumour bed histopathological features correlate with survival following neoadjuvant immunotherapy in stage III melanoma

BACKGROUND

Guidelines for pathological evaluation of neoadjuvant specimens and pathological response categories have been developed by the International Neoadjuvant Melanoma Consortium (INMC). As part of the Optimal Neo-adjuvant Combination Scheme of Ipilimumab and Nivolumab (OpACIN-neo) clinical trial of neoadjuvant combination anti-programmed cell death protein 1/anti-cytotoxic T-lymphocyte-associated protein 4 immunotherapy for stage III melanoma, we sought to determine interobserver reproducibility of INMC histopathological assessment principles, identify specific tumour bed histopathological features of immunotherapeutic response that correlated with recurrence and relapse-free survival (RFS) and evaluate proposed INMC pathological response categories for predicting recurrence and RFS.

PATIENTS AND METHODS

Clinicopathological characteristics of lymph node dissection specimens of 83 patients enrolled in the OpACIN-neo clinical trial were evaluated. Two methods of assessing histological features of immunotherapeutic response were evaluated: the previously described immune-related pathologic response (irPR) score and our novel immunotherapeutic response score (ITRS). For a subset of cases (n = 29), cellular composition of the tumour bed was analysed by flow cytometry.

RESULTS

There was strong interobserver reproducibility in assessment of pathological response (κ = 0.879) and percentage residual viable melanoma (intraclass correlation coefficient = 0.965). The immunotherapeutic response subtype with high fibrosis had the strongest association with lack of recurrence (P = 0.008) and prolonged RFS (P = 0.019). Amongst patients with criteria for pathological non-response (pNR, >50% viable tumour), all who recurred had ≥70% viable melanoma. Higher ITRS and irPR scores correlated with lack of recurrence in the entire cohort (P = 0.002 and P ≤ 0.0001). The number of B lymphocytes was significantly increased in patients with a high fibrosis subtype of treatment response (P = 0.046).

CONCLUSIONS

There is strong reproducibility for assessment of pathological response using INMC criteria. Immunotherapeutic response of fibrosis subtype correlated with improved RFS, and may represent a biomarker. Potential B-cell contribution to fibrosis development warrants further study. Reclassification of pNR to a threshold of ≥70% viable melanoma and incorporating additional criteria of <10% fibrosis subtype of response may identify those at highest risk of recurrence, but requires validation.

Beyond Teenage and Young Adult Cancer Care: Care Experiences of Patients Aged 25-39 Years Old in the UK National Health Service

AIMS

Adolescents and young adults aged 15-39 years with cancer face unique medical, practical and psychosocial issues. In the UK, principal treatment centres and programmes have been designed to care for teenage and young adult patients aged 13-24 years in an age-appropriate manner. However, for young adults (YAs) aged 25-39 years with cancer, little access to age-specific support is available. The aim of this study was to examine this possible gap by qualitatively exploring YA care experiences, involving patients as research partners in the analysis to ensure robust results.

MATERIALS AND METHODS

We conducted a phenomenological qualitative study with YAs diagnosed with any cancer type between ages 25 and 39 years old in the last 5 years. Participants took part in interviews or focus groups and data were analysed using inductive thematic analysis. Results were shaped in an iterative process with the initial coders and four YA patients who did not participate in the study to improve the rigor of the results.

RESULTS

Sixty-five YAs with a range of tumour types participated. We identified seven themes and 13 subthemes. YAs found navigating the healthcare system difficult and commonly experienced prolonged diagnostic pathways. Participants felt under-informed about clinical details and the long-term implications of side-effects on daily life. YAs found online resources overwhelming but also a source of information and treatment support. Some patients regretted not discussing fertility before cancer treatment or felt uninformed or rushed when making fertility preservation decisions. A lack of age-tailored content or age-specific groups deterred YAs from accessing psychological support and rehabilitation services.

CONCLUSIONS

YAs with cancer may miss some benefits provided to teenagers and young adults in age-tailored cancer services. Improving services for YAs in adult settings should focus on provision of age-specific information and access to existing relevant support.

What does the freshwater clam, Corbicula largillierti, have to tell us about chlorothalonil effects?

Chlorothalonil (CLT) is a broad spectrum, and non-systemic fungicide applied in foliar structures to prevent and treat pathogens. This compound reaches to aquatic environments and affects the biota. In this context, the main goal of this study was to assess the effects of CLT at biochemical, tissular, and individual levels of biological organization using the invasive bivalve Corbicula largillierti as a bioindicator species. Clams were exposed to different sublethal concentrations (0, 10, 20 and 50 µg. L^-1 CLT) for 96 h. At biochemical level, the enzymatic activity (Glutathione-s-Transferase, Catalase, Acetyl-, Butiryl- and Carboxyl-esterases) and lipid peroxidation were measured in gills and the visceral mass. Also, the digestive gland morphometry through quantitative histological indexes was registered at the tissular level. Finally, filtering activity and burial behavior at the individual level were measured. At the highest CLT concentration, the most significant changes were observed in enzymatic activity (except for butyrylcholinesterase), lipid peroxidation and in digestive gland morphometry. It was also registered increases of the filtering activity and the latency time to burial. Most of the biomarkers assessed showed significant responses under CLT exposure. Therefore, taking into account that C. largillierti was affected by CLT, it can be expected that other species could be in a potential risk if this fungicide is present in freshwater systems.

SETD1 and NF-κB Regulate Periodontal Inflammation through H3K4 Trimethylation

The inflammatory response to periodontal pathogens is dynamically controlled by the chromatin state on inflammatory gene promoters. In the present study, we have focused on the effect of the methyltransferase SETD1B on histone H3 lysine K4 (H3K4) histone trimethylation on inflammatory gene promoters. Experiments were based on 3 model systems: 1) an in vitro periodontal ligament (PDL) cell culture model for the study of SETD1 function as it relates to histone methylation and inflammatory gene expression using Porphyromonas gingivalis lipopolysaccharide (LPS) as a pathogen, 2) a subcutaneous implantation model to determine the relationship between SETD1 and nuclear factor κB (NF-κB) through its activation inhibitor BOT-64, and 3) a mouse periodontitis model to test whether the NF-κB activation inhibitor BOT-64 reverses the inflammatory tissue destruction associated with periodontal disease. In our PDL progenitor cell culture model, P. gingivalis LPS increased H3K4me3 histone methylation on IL-1β, IL-6, and MMP2 gene promoters, while SETD1B inhibition decreased H3K4me3 enrichment and inflammatory gene expression in LPS-treated PDL cells. LPS also increased SETD1 nuclear localization in a p65-dependent fashion and the nuclear translocation of p65 as mediated through SETD1, suggestive of a synergistic effect between SETD1 and p65 in the modulation of inflammation. Confirming the role of SETD1 in p65-mediated periodontal inflammation, BOT-64 reduced the number of SETD1-positive cells in inflamed periodontal tissues, restored periodontal tissue integrity, and enhanced osteogenesis in a periodontal inflammation model in vivo. Together, these results have established the histone lysine methyltransferase SETD1 as a key factor in the opening of the chromatin on inflammatory gene promoters through histone H3K4 trimethylation. Our studies also confirmed the role of BOT-64 as a potent molecular therapeutic for the restoration of periodontal health through the inhibition of NF-κB activity and the amelioration of SETD1-induced chromatin relaxation.

Effect of a lifestyle-focused electronic patient support application on risk factor management in post-myocardial infarction patients – a randomized controlled trial

Background

Cardiac rehabilitation (CR) is central in reducing morbidity and mortality after myocardial infarction (MI). However, the fulfillment of guideline recommended CR targets is unsatisfactory. eHealth offers new possibilities to improve clinical care.

Purpose

The aim of this study was to assess the efficacy of a mobile device application to support adherence to lifestyle advice and self-control of risk factors as a complement to traditional CR after MI.

Method

This unblinded multi-centre randomized controlled trial included 150 patients with MI (81% men, 60.4±8.8 years). All patients in the intervention (INT) and control (CON) groups participated in a 1-year CR program. Additionally, INT patients (n=101) received access to the mobile device application for 25 weeks post-MI where information about lifestyle (i.e., diet, physical activity, smoking), modifiable risk factors (i.e., weight, blood pressure (BP)), and symptoms could be registered. The software provided direct positive feedback and lifestyle advice. Data was reviewed twice weekly by the CR nurse. The primary outcome was change in sub-maximal exercise capacity (W) between an exercise test 2-weeks post MI and at follow-up 4 month later. Secondary outcomes included changes in lifestyle and modifiable risk factors including body mass index, waist circumference, blood-lipids, fasting glucose and HbA1c, between baseline and 2-week, 2-month and 1-year follow-up visits. Regression analysis was used, adjusting for relevant baseline variables.

Results

Participation in CR was high, with 96% of INT patients and 98% of the CON patients attending the 1-year follow-up visit. Forty-six percent of the INT patients and 57% of the CON patients attended centre-based exercise training (p=0.1). In the INT group 86% logged data in the application at least once. Adherence, defined as logging data at least twice per week, was 92% in week 1 and 57% in week 25. There was a numerical trend toward better exercise capacity improvement in the INT group (INT +14.4±19.0 vs. CON +10.3±16.1 W, p=0.2) although differences were non-significant. INT patients achieved larger BP reduction at 2-weeks (systolic) and 2-months (systolic and diastolic) (Figure). At 2-months 70% vs. 46% of smokers in the INT vs CON groups had quit smoking, and at 1-year the respective percentages were 57% vs. 36%. The number of smokers in the study was however low (n=33) and the differences non-significant. For other secondary endpoints no differences were observed.

Conclusion

Complementing CR with a mobile device application improved BP during the first months after MI, and non-significant trends towards better exercise capacity and higher smoking cessation rates were observed. Even though the differences were non-significant in our small study sample, they indicate that using eHealth in the form of a mobile device application could clinically benefit post-MI patients participating in CR.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Governmental funding of clinical research within the National Health Services in Sweden.

Impact de l’infection par le SARS-CoV2 chez la femme enceinte et ses conséquences en santé au travail

L’objectif de cette recommandation est de présenter à travers une revue narrative l’impact de l’infection par le SARS-CoV2 chez la femme enceinte et ses conséquences en santé au travail.

Histone Methylation: Achilles Heel and Powerful Mediator of Periodontal Homeostasis

The packaging of DNA around nucleosomes exerts dynamic control over eukaryotic gene expression either by granting access to the transcriptional machinery in an open chromatin state or by silencing transcription via chromatin compaction. Histone methylation modification affects chromatin through the addition of methyl groups to lysine or arginine residues of histones H3 and H4 by means of histone methyl transferases or histone demethylases. Changes in histone methylation state modulate periodontal gene expression and have profound effects on periodontal development, health, and therapy. At the onset of periodontal development, progenitor cell populations such as dental follicle cells are characterized by an open H3K4me3 chromatin mark on RUNX2, MSX2, and DLX5 gene promoters. During further development, periodontal progenitor differentiation undergoes a global switch from the H3K4me3 active methyl mark to the H3K27me3 repressive mark. When compared with dental pulp cells, periodontal neural crest lineage differentiation is characterized by repressive H3K9me3 and H3K27me3 marks on typical dentinogenesis-related genes. Inflammatory conditions as they occur during periodontal disease result in unique histone methylation signatures in affected cell populations, including repressive H3K9me3 and H3K27me3 histone marks on extracellular matrix gene promoters and active H3K4me3 marks on interleukin, defensin, and chemokine gene promoters, facilitating a rapid inflammatory response to microbial pathogens. The inflammation-induced repression of chromatin on extracellular matrix gene promoters presents a therapeutic opportunity for the application of histone methylation inhibitors capable of inhibiting suppressive trimethylation marks. Furthermore, inhibition of chromatin coregulators through interference with key inflammatory mediators such as NF-kB by means of methyltransferase inhibitors provides another avenue to halt the exacerbation of the inflammatory response in periodontal tissues. In conclusion, histone methylation dynamics play an intricate role in the fine-tuning of chromatin states during periodontal development and harbor yet-to-be-realized potential for the treatment of periodontal disease.