Synaptic injury in the inner plexiform layer of the retina is associated with progression in multiple sclerosis

While neurodegeneration underlies the pathological basis for permanent disability in multiple sclerosis (MS), predictive biomarkers for progression are lacking. Using an animal model of chronic MS, we find that synaptic injury precedes neuronal loss and identify thinning of the inner plexiform layer (IPL) as an early feature of inflammatory demyelination-prior to symptom onset. As neuronal domains are anatomically segregated in the retina and can be monitored longitudinally, we hypothesize that thinning of the IPL could represent a biomarker for progression in MS. Leveraging our dataset with over 800 participants enrolled for more than 12 years, we find that IPL atrophy directly precedes progression and propose that synaptic loss is predictive of functional decline. Using a blood proteome-wide analysis, we demonstrate a strong correlation between demyelination, glial activation, and synapse loss independent of neuroaxonal injury. In summary, monitoring synaptic injury is a biologically relevant approach that reflects a potential driver of progression.

Neurofilament Light Chain Elevation and Disability Progression in Multiple Sclerosis

Importance

Mechanisms contributing to disability accumulation in multiple sclerosis (MS) are poorly understood. Blood neurofilament light chain (NfL) level, a marker of neuroaxonal injury, correlates robustly with disease activity in people with MS (MS); however, data on the association between NfL level and disability accumulation have been conflicting.

Objective

To determine whether and when NfL levels are elevated in the context of confirmed disability worsening (CDW).

Design, Setting, and Participants

This study included 2 observational cohorts: results from the Expression, Proteomics, Imaging, Clinical (EPIC) study at the University of California San Francisco (since 2004) were confirmed in the Swiss Multiple Sclerosis Cohort (SMSC), a multicenter study in 8 centers since 2012. Data were extracted from EPIC in April 2022 (sampling July 1, 2004, to December 20, 2016) and SMSC in December 2022 (sampling June 6, 2012, to September 2, 2021). The study included 2 observational cohorts in tertiary MS centers. All participants of both cohorts with available NfL results were included in the study, and no eligible participants were excluded or declined to participate.

Exposure

Association between NfL z scores and CDW.

Main Outcome Measures

CDW was defined as Expanded Disability Status Scale (EDSS) worsening that was confirmed after 6 or more months and classified into CDW associated with clinical relapses (CDW-R) or independent of clinical relapses (CDW-NR). Visits were classified in relation to the disability worsening events into CDW(-2) for 2 visits preceding event, CDW(-1) for directly preceding event, CDW(event) for first diagnosis of EDSS increase, and the confirmation visit. Mixed linear and Cox regression models were used to evaluate NfL dynamics and to assess the association of NfL with future CDW, respectively.

Results

A total of 3906 EPIC visits (609 participants; median [IQR] age, 42.0 [35.0-50.0] years; 424 female [69.6%]) and 8901 SMSC visits (1290 participants; median [IQR] age, 41.2 [32.5-49.9] years; 850 female [65.9%]) were included. In CDW-R (EPIC, 36 events; SMSC, 93 events), NfL z scores were 0.71 (95% CI, 0.35-1.07; P < .001) units higher at CDW-R(-1) in EPIC and 0.32 (95% CI, 0.14-0.49; P < .001) in SMSC compared with stable MS samples. NfL elevation could be detected preceding CDW-NR (EPIC, 191 events; SMSC, 342 events) at CDW-NR(-2) (EPIC: 0.23; 95% CI, 0.01-0.45; P = .04; SMSC: 0.28; 95% CI, 0.18-0.37; P < .001) and at CDW-NR(-1) (EPIC: 0.27; 95% CI, 0.11-0.44; P < .001; SMSC: 0.09; 95% CI, 0-0.18; P = .06). Those findings were replicated in the subgroup with relapsing-remitting MS. Time-to-event analysis confirmed the association between NfL levels and future CDW-R within approximately 1 year and CDW-NR (in approximately 1-2 years).

Conclusions and Relevance

This cohort study documents the occurrence of NfL elevation in advance of clinical worsening and may hint to a potential window of ongoing dynamic central nervous system pathology that precedes the diagnosis of CDW.

Differences in Age-related Retinal and Cortical Atrophy Rates in Multiple Sclerosis

BACKGROUND AND OBJECTIVES

The timing of neurodegeneration in multiple sclerosis (MS) remains unclear. It is critical to understand the dynamics of neuroaxonal loss if we hope to prevent or forestall permanent disability in MS. We therefore used a deeply phenotyped longitudinal cohort to assess and compare rates of neurodegeneration in retina and brain throughout the MS disease course.

METHODS

We analyzed 597 patients with MS who underwent longitudinal optical coherence tomography imaging annually for 4.5 ± 2.4 years and 432 patients who underwent longitudinal MRI scans for 10 ± 3.4 years, quantifying macular ganglion cell-inner plexiform layer (GCIPL) volume and cortical gray matter (CGM) volume. The association between the slope of decline in the anatomical structure and the age of entry in the cohort (categorized by the MRI cohort's age quartiles) was assessed by hierarchical linear models.

RESULTS

The rate of CGM volume loss declined with increasing age of study entry (1.3% per year atrophy for the age of entry in the cohort younger than 35 years; 1.1% for older than 35 years and younger than 41; 0.97% for older than 41 years and younger than 49; 0.9% for older than 49 years) while the rate of GCIPL thinning was highest in patients in the youngest quartile, fell by more than 50% in the following age quartile, and then stabilized (0.7% per year thinning for the age of entry in the cohort younger than 35 years; 0.29% for age older than 35 and younger than 41 years; 0.34% for older than 41 and younger than 49 years; 0.33% for age older than 49 years).

DISCUSSION

An age-dependent reduction in retinal and cortical volume loss rates during relapsing-remitting MS suggests deceleration in neurodegeneration in the earlier period of disease and further indicates that the period of greatest adaptive immune-mediated inflammatory activity is also the period with the greatest neuroaxonal loss.

Plasma neurofilament light chain levels suggest neuroaxonal stability following therapeutic remyelination in people with multiple sclerosis

BACKGROUND

Chronic demyelination is a major contributor to axonal vulnerability in multiple sclerosis (MS). Therefore, remyelination could provide a potent neuroprotective strategy. The ReBUILD trial was the first study showing evidence for successful remyelination following treatment with clemastine in people with MS (pwMS) with no evidence of disease activity or progression (NEDAP). Whether remyelination was associated with neuroprotection remains unexplored.

METHODS

Plasma neurofilament light chain (NfL) levels were measured from ReBUILD trial's participants. Mixed linear effect models were fit for individual patients, epoch and longitudinal measurements to compare NfL concentrations between samples collected during the active and placebo treatment period.

RESULTS

NfL concentrations were 9.6% lower in samples collected during the active treatment with clemastine (n=53, geometric mean=6.33 pg/mL) compared to samples collected during treatment with placebo (n=73, 7.00 pg/mL) (B=-0.035 [-0.068 to -0.001], p=0.041). Applying age- and body mass index-standardised NfL Z-scores and percentiles revealed similar results (0.04 vs 0.35, and 27.5 vs 33.3, p=0.023 and 0.042, respectively). Higher NfL concentrations were associated with more delayed P100 latencies (B=1.33 [0.26 to 2.41], p=0.015). In addition, improvement of P100 latencies between visits was associated with a trend for lower NfL values (B=0.003 [-0.0004 to 0.007], p=0.081). Based on a Cohen's d of 0.248, a future 1:1 parallel-arm placebo-controlled study using a remyelinating agent with comparable effect as clemastine would need 202 subjects per group to achieve 80% power.

CONCLUSIONS

In pwMS, treatment with the remyelinating agent clemastine was associated with a reduction of blood NfL, suggesting that neuroprotection is achievable and measurable with therapeutic remyelination.

TRIAL REGISTRATION NUMBER

NCT02040298.

Performance report for a 10-year-old MD/PhD Program: A survey of trainees at the University of Ottawa

PURPOSE

Integrated MD/PhD programs are relatively new in Canada and represent a platform to train the next generation of clinician-scientists. However, MD/PhD programs vary substantially by structure, funding and mentorship opportunities, and there exists a paucity of data on the overall students' successes and challenges. The purpose of this study is to assess objective and subjective metrics of the MD/PhD Program at the University of Ottawa.

METHODS

Students in all years of the program were invited to complete a 58- question survey, and the resulting data were analyzed by descriptive statistics.

RESULTS

Our survey had an 88.5% (23/26) participation rate. The program has been gaining interest and the number of applications increased by 178% between 2013 and 2018. Tuition support was considered an essential element in accepting the admission offer, as 47.8% of students would have declined admission without full tuition coverage. The MD/PhD students were heavily engaged in scholarly activities, with an average of 8.3 presentations/ publications per respondent. Respondents indicated low satisfaction with formal career planning advice (28.6% satisfied/very satisfied) and program transition guidance (22.2%). When delivered informally by peers, both career planning advice and program transition guidance were experienced as more satisfying (65.2% and 63.6%, respectively). Only 34.8% of survey respondents identified as female, highlighting the challenge of achieving diversity in clinician-scientist training programs.

CONCLUSION

Our report contributes to the body of knowledge on concrete obstacles experienced by students within MD/PhD programs and key areas that can be improved upon-locally, provincially and nationally-to further advance student success.

Antenatal IL-1-dependent inflammation persists postnatally and causes retinal and sub-retinal vasculopathy in progeny

Antenatal inflammation as seen with chorioamnionitis is harmful to foetal/neonatal organ development including to eyes. Although the major pro-inflammatory cytokine IL-1β participates in retinopathy induced by hyperoxia (a predisposing factor to retinopathy of prematurity), the specific role of antenatal IL-1β associated with preterm birth (PTB) in retinal vasculopathy (independent of hyperoxia) is unknown. Using a murine model of PTB induced with IL-1β injection in utero, we studied consequent retinal and choroidal vascular development; in this process we evaluated the efficacy of IL-1R antagonists. Eyes of foetuses exposed only to IL-1β displayed high levels of pro-inflammatory genes, and a persistent postnatal infiltration of inflammatory cells. This prolonged inflammatory response was associated with: (1) a marked delay in retinal vessel growth; (2) long-lasting thinning of the choroid; and (3) long-term morphological and functional alterations of the retina. Antenatal administration of IL-1R antagonists - 101.10 (a modulator of IL-1R) more so than Kineret (competitive IL-1R antagonist) - prevented all deleterious effects of inflammation. This study unveils a key role for IL-1β, a major mediator of chorioamnionitis, in causing sustained ocular inflammation and perinatal vascular eye injury, and highlights the efficacy of antenatal 101.10 to suppress deleterious inflammation.

Preterm Birth: An Inflammatory Syndrome, Not Just A Myometrial Disorder

Preterm birth (PTB) is the leading cause of neonatal mortality and morbidity. Although the severity of neonatal outcomes is inversely correlated with gestational age, all PTBs can lead to potentially life-threatening neonatal outcomes and major lifelong health complications. Because advances in neonatal care have substantially decreased neonatal mortality, the incidence of PTB and its complications is unabatedly rising. PTB currently affects more than 10% of births worldwide, with similar numbers in developed countries. Correspondingly, improving neonatal outcome is a key objective of the World Health Organization. The recently approved (in Europe) tocolytics drug, Atosiban, used to prolong preterm gestation, has not been shown to improve neonatal outcome, nor have other tocolytic agents used in clinic. Thus, PTB remains an unmet medical need. Recent evidence shows that most, if not all, PTBs are associated with (overt or occult) inflammatory processes in gestational tissues, independent of infection. Pro- inflammatory cytokines are produced from maternal and fetal cells in response to sterile or infectious stressors. These seem to orchestrate a multi-tissue response including myometrial contractility, cervical ripening, and weakening/rupture of fetal membranes, leading to the onset of preterm labor. This integrated system might have been conserved through mammalian evolution due to increased maternal and/or fetal survival when gestation is terminated in specific settings, such as infection. Hence, inflammation may be a common pathway to the numerous aetiologies of PTB. Most importantly, recent evidence suggests that inflammation is transmitted to the fetus, thereby inducing organ injuries that may underlie the development of major neonatal diseases. Targeting inflammation prenatally instead of myometrial contraction could be a more successful and safe approach for the management of PTB, as suggested by recent animal studies. RésuméLa naissance prématurée est la principale cause de mortalité et de morbidité néonatale. Bien que la sévérité des issus néonataux soit inversement corrélée avec l’âge gestationnel à la naissance, toutes les naissances prématurées peuvent mener à des issus néonataux potentiellement mortels et à des complications avec répercussions s’échelonnant sur toute la vie. Étant donné que la mortalité néonatale a considérablement diminuée avec les récentes avancées en néonatalogie, l’incidence de la naissance prématurée et de ses complications sont en hausse. La naissance prématurée affecte présentement plus de 10% des naissances à travers le monde, avec des taux similaires dans les pays développés. Conséquemment, d’améliorer l’issu néonatal est un objectif clé de l’Organisation Mondiale de la Santé. Le tocolytique Atosiban récemment approuvé (en Europe) pour prolonger les gestations pré- maturées n’a pas démontré d’efficacité pour améliorer les issus néonataux, tout comme les autres tocolytiques utilisés en clinique, et la naissance prématurée demeure un besoin médical non-atteint. Des données récentes démontrent que la plupart, sinon toutes les naissances prématurées sont associées avec des processus inflammatoires (francs ou silencieux) dans les tissus gestationnels, indépendamment de l’infection. Les cytokines pro-inflammatoires sont produites dans les cellules maternelles et fœtales en réponse à des stresseurs stériles ou infectieux, et semblent orchestrer une réponse multi-tissulaire incluant la contractilité myométriale, la préparation cervicale, et l’affaiblissement/rupture des membranes fœtales, menant au commencement du travail préterme. Ce système intégré pourrait avoir été conservé durant l’évolution mammifère à cause d’une survie accrue de la mère et/ou du fœtus lorsque la gestation est terminée dans un contexte spécifique, comme l’infection. Donc, l’inflammation pourrait constituer une voie commune finale pour les nombreuses causes de la naissance prématurée. De façon importante, des données récentes sug- gèrent que cette inflammation est transmise au fœtus et en retour induit des dommages aux organes qui pourraient sous-tendre le développement de maladies néonatales majeures. De cibler l’inflammation en prénatal plutôt que les contractions myométriales pourrait constituer une approche sécuritaire et plus efficace, comme suggéré par de récentes études animales.  

Antenatal Suppression of IL-1 Protects against Inflammation-Induced Fetal Injury and Improves Neonatal and Developmental Outcomes in Mice

Preterm birth (PTB) is commonly accompanied by in utero fetal inflammation, and existing tocolytic drugs do not target fetal inflammatory injury. Of the candidate proinflammatory mediators, IL-1 appears central and is sufficient to trigger fetal loss. Therefore, we elucidated the effects of antenatal IL-1 exposure on postnatal development and investigated two IL-1 receptor antagonists, the competitive inhibitor anakinra (Kineret) and a potent noncompetitive inhibitor 101.10, for efficacy in blocking IL-1 actions. Antenatal exposure to IL-1β induced Tnfa, Il6, Ccl2, Pghs2, and Mpges1 expression in placenta and fetal membranes, and it elevated amniotic fluid IL-1β, IL-6, IL-8, and PGF_2α, resulting in PTB and marked neonatal mortality. Surviving neonates had increased Il1b, Il6, Il8, Il10, Pghs2, Tnfa, and Crp expression in WBCs, elevated plasma levels of IL-1β, IL-6, and IL-8, increased IL-1β, IL-6, and IL-8 in fetal lung, intestine, and brain, and morphological abnormalities: e.g., disrupted lung alveolarization, atrophy of intestinal villus and colon-resident lymphoid follicle, and degeneration and atrophy of brain microvasculature with visual evoked potential anomalies. Late gestation treatment with 101.10 abolished these adverse outcomes, whereas Kineret exerted only modest effects and no benefit for gestation length, neonatal mortality, or placental inflammation. In a LPS-induced model of infection-associated PTB, 101.10 prevented PTB, neonatal mortality, and fetal brain inflammation. There was no substantive deviation in postnatal growth trajectory or adult body morphometry after antenatal 101.10 treatment. The results implicate IL-1 as an important driver of neonatal morbidity in PTB and identify 101.10 as a safe and effective candidate therapeutic.

Choroidal Involution Is Associated with a Progressive Degeneration of the Outer Retinal Function in a Model of Retinopathy of Prematurity: Early Role for IL-1β

Retinopathy of prematurity (ROP), the most common cause of blindness in premature infants, has long been associated with inner retinal alterations. However, recent studies reveal outer retinal dysfunctions in patients formerly afflicted with ROP. We have recently demonstrated that choroidal involution occurs early in retinopathy. Herein, we investigated the mechanisms underlying the choroidal involution and its long-term impact on retinal function. An oxygen-induced retinopathy (OIR) model was used. In vitro and ex vivo assays were applied to evaluate cytotoxic effects of IL-1β on choroidal endothelium. Electroretinogram was used to evaluate visual function. We found that proinflammatory IL-1β was markedly increased in retinal pigment epithelium (RPE)/choroid and positively correlated with choroidal degeneration in the early stages of retinopathy. IL-1β was found to be cytotoxic to choroid in vitro, ex vivo, and in vivo. Long-term effects on choroidal involution included a hypoxic outer neuroretina, associated with a progressive loss of RPE and photoreceptors, and visual deterioration. Early inhibition of IL-1β receptor preserved choroid, decreased subretinal hypoxia, and prevented RPE/photoreceptor death, resulting in life-long improved visual function in IL-1 receptor antagonist-treated OIR animals. Together, these findings suggest a critical role for IL-1β-induced choroidal degeneration in outer retinal dysfunction. Neonatal therapy using IL-1 receptor antagonist preserves choroid and prevents protracted outer neuroretinal anomalies in OIR, suggesting IL-1β as a potential therapeutic target in ROP.

Uterotonic Neuromedin U Receptor 2 and Its Ligands Are Upregulated by Inflammation in Mice and Humans, and Elicit Preterm Birth

Uterine labor requires the conversion of a quiescent (propregnancy) uterus into an activated (prolabor) uterus, with increased sensitivity to endogenous uterotonic molecules. This activation is induced by stressors, particularly inflammation in term and preterm labor. Neuromedin U (NmU) is a neuropeptide known for its uterocontractile effects in rodents. The objective of the study was to assess the expression and function of neuromedin U receptor 2 (NmU-R2) and its ligands NmU and the more potent neuromedin S (NmS) in gestational tissues, and the possible implication of inflammatory stressors in triggering this system. Our data show that NmU and NmS are uterotonic ex vivo in murine tissue, and they dose-dependently trigger labor by acting specifically via NmU-R2. Expression of NmU-R2, NmU, and NmS is detected in murine and human gestational tissues by immunoblot, and the expression of NmS in placenta and of NmU-R2 in uterus increases considerably with gestation age and labor, which is associated with amplified NmU-induced uterocontractile response in mice. NmU- and NmS-induced contraction is associated with increased NmU-R2-coupled Ca⁺⁺ transients, and Akt and Erk activation in murine primary myometrial smooth muscle cells (mSMCs), which are potentiated with gestational age. NmU-R2 is upregulated in vitro in mSMCs and in vivo in uterus in response to proinflammatory interleukin 1beta (IL1beta), which is associated with increased NmU-induced uterocontractile response and Ca⁺⁺ transients in murine and human mSMCs; additionally, placental NmS is markedly upregulated in vivo in response to IL1beta. In human placenta at term, immunohistological analysis revealed NmS expression primarily in cytotrophoblasts; furthermore, stimulation with lipopolysaccharide (LPS; Gram-negative endotoxin) markedly upregulates NmS expression in primary human cytotrophoblasts isolated from term placentas. Correspondingly, decidua of women with clinical signs of infection who delivered preterm display significantly higher expression of NmS compared with those without infection. Importantly, in vivo knockdown of NmU-R2 prevents LPS-triggered preterm birth in mice and the associated neonatal mortality. Altogether, our data suggest a critical role for NmU-R2 and its ligands NmU and NmS in preterm labor triggered by infection. We hereby identify NmU-R2 as a relevant target for preterm birth.