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. Author manuscript; available in PMC: 2026 Jun 27.
Published in final edited form as: Am J Physiol Lung Cell Mol Physiol. 2026 May 20;330(6):L780–L788. doi: 10.1152/ajplung.00012.2026

Tracheal Aspirates of Mechanically Ventilated Preterm Infants Possess Cytopathic Tau Variants: A Prospective Exploratory Study

Kalsang Dolma 1,4, Saminathan Anbalagan 1,4, Linn Ayers 2,4, Althea deWeever 1,4, Brian Fouty 3,4, Jonathon P Audia 4,5, Chung-Sik Choi 2,4, Mike Lin 2,4, Manimaran Ramani 1,4, Troy Stevens 2,3,4
PMCID: PMC13308501  NIHMSID: NIHMS2179865  PMID: 42161310

Abstract

Tau protein, a microtubule-associated protein expressed in lung capillary endothelium, is detectable early in lung development and has been implicated in systemic dysfunction during adult respiratory infections. Its role in neonatal lung injury, however, remains undefined. In this study, we analyzed tracheal aspirates from 67 mechanically ventilated infants (51 preterm and 16 term) and compared them with 20 cord blood samples and five healthy adult plasma samples. Preterm infants were further stratified by histological chorioamnionitis status and severity of bronchopulmonary dysplasia (BPD) at 36 weeks' postmenstrual age (Jensen's 2019 criteria). Total tau concentrations were measured using a Meso-Scale Discovery assay, and neuronal tau seeding assays assessed the presence of cytopathic tau variants. Tau was detected in all samples, with significantly higher concentrations in neonatal tracheal aspirates and cord blood compared with adult plasma. In both cord blood and tracheal aspirates, preterm infants exhibited elevated total tau levels relative to term infants. The tau protein present in preterm tracheal aspirates induced neuronal tau aggregation across gestational ages. Although total tau concentrations did not differ, the cytopathic activity of tracheal aspirates was increased in infants with chorioamnionitis. Neither total tau nor seeding activity correlated with BPD severity. Our study findings demonstrate that tau is abundant in the airways of mechanically ventilated preterm infants and exhibits cytopathic properties, suggesting a potential role in both neonatal lung injury and development. Further studies are needed to clarify the mechanistic contribution of tau to lung pathology in this highly vulnerable population.

Keywords: Tau protein, Cytopathic tau, Preterm, Bronchopulmonary dysplasia, Histologic chorioamnionitis

New and Noteworthy

In mechanically ventilated preterm infants, endogenous airway molecules may influence lung injury and development. Tau, a microtubule-associated protein expressed in lung endothelium, was abundant in neonatal tracheal aspirates and elevated in preterm infants. Tau in preterm samples also showed cytopathic seeding activity, which was further increased in infants with histological chorioamnionitis. These findings identify tau as a previously unrecognized bioactive airway component that may contribute to early lung pathology.

Graphical Abstract

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Introduction

The alveolar–capillary membrane is a specialized interface that enables efficient gas exchange and maintains a tightly regulated barrier (1, 2). Its development relies on coordinated cellular interactions between the resident lung cells, leading to the formation of a dense alveolar capillary network that expands rapidly during late gestation (3–6). In extremely preterm infants, this process is often disrupted by prenatal and postnatal insults—including chorioamnionitis, mechanical ventilation, oxidative stress, and sepsis leading to bronchopulmonary dysplasia (BPD), a chronic lung disease characterized by simplified alveolar structures and abnormal pulmonary vascular growth (7–13). Despite considerable research, the mechanistic pathway linking inflammation to impaired lung development remains poorly understood.

Tau, a microtubule-associated protein best known for its role in neurodegenerative disease, has also been identified in non-neuronal tissues, including the lung (14–16). In pulmonary capillary endothelium, tau is expressed as early as the pseudoglandular stage of lung development and persists into adulthood, suggesting a role in vascular stability and remodeling (17). To date, four isoforms—0N4R, 1N4R, 2N4R, and big tau—have been identified from adult rodent lung endothelium (16). Under normal conditions, tau stabilizes microtubules; however, hyperphosphorylation causes it to dissociate and form oligomeric aggregates that are cytotoxic (18). In adult humans, lower respiratory tract infections can trigger the formation of these pathogenic tau variants, which are then released into the circulation and contribute to organ dysfunction (19–22). Whether tau, particularly its cytopathic (pathological) forms, plays a role in the normal or abnormal development of the human lung remains unknown.

In this exploratory study, we analyzed tracheal aspirates from mechanically ventilated preterm and term infants to determine the presence and levels of tau and cytotoxic tau protein. We further evaluated whether perinatal risk factors such as pregnancy-induced hypertension, maternal diabetes, histological chorioamnionitis, mode of delivery, gender, and race influence total or cytopathic tau concentrations and examined their association with the subsequent development of BPD. We hypothesized that tau variants are detectable in airway secretions of preterm infants and that perinatal inflammation induces the release of cytopathic tau, contributing to abnormal lung development. By characterizing the tau in the tracheal aspirates, we aim to investigate its possible role in neonatal lung development and injury.

Material and Methods:

A prospective observational study was conducted between July 2019 and October 2023 at the University of South Alabama Neonatal Intensive Care Unit (NICU). The study protocol was approved by the University of South Alabama Institutional Review Board (IRB #22–398), with a waiver of consent granted, as samples were either obtained during routine clinical care or classified as biological waste and were handled in a de-identified manner. All procedures were performed in accordance with institutional and national ethical guidelines.

Patient Population:

All intubated preterm and term infants admitted to our NICU were eligible for inclusion. Tracheal aspirate samples were collected from term and preterm infants to measure total tau levels. In a separate cohort of term and preterm infants, umbilical cord blood samples were collected at birth to assess circulating tau levels. Additionally, we also collected five blood samples from healthy adults for comparison.

Sample Collection:

Tracheal aspirate:

According to the unit protocol, tracheal aspirate samples were collected from patients within the first hours following intubation. Sample collection was performed after ensuring that the infant was adequately ventilated. The sample collection procedure ensured that there was no interruption to normal clinical care. Tracheal aspirate samples were obtained after instilling 1 mL sterile isotonic saline into the infant’s endotracheal tube, manual ventilation through the endotracheal tube for three breaths, and suctioning the fluid into a sterile mucus trap. Samples were stored frozen at −80°C until further processing. Before analysis, tracheal aspirate samples were diluted in HBSS (with Ca2+/Mg2+) to a final volume of 500 μL, then centrifuged at 4000 g for 10 minutes to remove any mucous plus or debris. The supernatant was used for analysis.

Cord Blood:

Cord blood was collected from the umbilical vein in sodium heparin tubes. Samples were centrifuged at 4000 g for 10 minutes, and the plasma was stored at −80°C until analysis. Cord blood plasma was analyzed without dilution.

Measurement of Total Tau Protein using Meso Scale Discovery (MSD) Assay:

Total tau concentrations were measured using the Meso Scale Discovery (MSD, Rockville, MD) Human Total Tau R-PLEX Plus Kit (K1518DR-2) according to the manufacturer’s protocol (23). All samples were tested in duplicate by a single technician, and tracheal aspirate (TA) results were corrected for the dilution factor.

Biomolecular Fluorescence Complementation (BiFC) Seeding Assay:

To assess cytopathic potential (seeding potential or presence of misfolded tau capable of promoting the aggregation of normal tau monomers), tau seeding activity was evaluated using a BiFC assay as described previously (16). HEK293 cells stably expressing human 2N4R tau BiFC constructs were cultured to 70% confluence in 12-well plates with coverslips and transfected with TA supernatants using the Xfect Protein Transfection Reagent (Clontech, Mountain View, CA; #NC1102016). After 24 hours, cells were fixed in 4% paraformaldehyde, and coverslips were mounted for imaging. Fluorescence micrographs were captured using a Nikon Eclipse 80i microscope (excitation: 514 nm; emission: 535 nm) with a 20× objective. Five fields per sample were imaged, and fluorescence intensity was quantified using FIJI-ImageJ, as per established methodology.

Clinical Data Collection:

Clinical data were extracted from the electronic medical record at enrollment and throughout hospitalization, including antenatal exposure such as corticosteroids. Preterm Infants were followed to determine their BPD status at 36 weeks postmenstrual age. BPD and its severity were defined by Jensen’s 2019 criteria (24). Intrauterine inflammation, which can influence neonatal tau expression and aggregation, was considered in our analyses. Within preterm groups, intrauterine inflammation was assessed as histological chorioamnionitis, diagnosed according to the Amsterdam Placental Workshop Group criteria, defined by the presence of acute maternal inflammatory response in the chorion and/or amnion with or without a fetal inflammatory response (funisitis) (25). As our center does not routinely perform placental histology for term infants, clinical chorioamnionitis was used when comparing term and preterm infants. Clinical chorioamnionitis was defined by the presence of one or more of the following signs and symptoms: maternal fever, maternal or fetal tachycardia, uterine tenderness, foul-smelling amniotic fluid, or an elevated white blood cell count.

Statistical Analysis:

Statistical analyses were performed using Stata v17.0 (StataCorp, College Station, TX) and GraphPad Prism v10 (Boston, MA). Continuous variables are presented as mean ± SD (clinical data) or mean ± SE (experimental data). Comparisons between term and preterm infants were made using the Mann–Whitney U test or chi-squared analysis, as appropriate. Tau levels across gestational ages and subgroups were analyzed using the Kruskal–Wallis test with Dunn’s post hoc correction. A p-value < 0.05 was considered statistically significant.

Results:

Infant characteristics of 2 groups:

A total of 67 infants were enrolled in the study and were separated into two groups based on gestational age (51 preterm and 16 term infants). The demographic and clinical characteristics of patients included in the study are shown in Table 1. Seven preterm and one term infant died before eligibility for BPD assessment. Known BPD risk factors, including gestational age, birthweight, gender, ethnicity, intrauterine growth restriction, presence of histological chorioamnionitis, late onset sepsis, and maternal preeclampsia, are shown in Table 1.

Table 1:

Baseline demographic and clinical characteristics of the study population.

Preterm (n=51) Term (n=16)
PMA at sample collection, weeks±SD 26.5± 2.7 38.6 ± 1.1
Gestational age, weeks±SD 26.1 ± 2.8 38.1 ± 1.1
Birthweight, grams ±SD 841±382 3097 ± 976
Male sex, no. (%) 26 (53) 12 (75)
Black, no. (%)  19 (37)  4 (25)
Inborn, no (%) 45 (90) 10 (63)
Small for gestational age, no. (%) 12 (24) 0 (0)
Multiple gestation, no. (%) 13 (25) 0 (0)
Antenatal corticosteroid, no. (%) 43 (84) 1 (6)
Histological chorioamnionitis, no. (%) 21 (41) 1 (6)
Cesarean section, no. (%) 36 (71) 12 (75)
Gestational hypertension, no. (%) 21 (44) 0 (0)
Maternal Diabetes, no. (%) 4 (8) 0 (0)
BPD at 36 weeks, no. (%) 29 (66) 0 (0)
PDA any treatment, no. (%) 18 (35) 0 (0)
Early onset sepsis, no. (%) 3 (6) 0 (0)
Late onset sepsis, no. (%) 7 (14) 1 (6)
IVH grade 3 or 4, no. (%) 5 (10) 1 (6)
ROP stage ≥3, no. (%) 4 (9) 0 (0)
Necrotizing enterocolitis ≥ stage 2, no. (%) 3 (6) 0 (0)
Home oxygen, no. (%) 22 (54) 1 (7)
Mortality, no. (%) 7 (14) 1 (6)
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Continuous variables are presented as mean±SD, and categorical variable represented as number (%). PMA, postmenstrual age; BPD, bronchopulmonary dysplasia; PDA, patent ductus arteriosus; IVH, intraventricular hemorrhage; ROP, Retinopathy of prematurity

1. Tau protein concentration in tracheal aspirates and cord blood of term and preterm infants

We quantified total tau concentrations in 67 tracheal aspirate samples (51 from preterm infants and 16 from term infants) and 20 cord blood plasma samples and compared it with five adult plasma samples. Total tau protein was consistently detectable across all sample types. The mean concentration of total tau in tracheal aspirates was 73.2 ± 11.7 pg/mL, whereas cord blood samples exhibited significantly higher levels, averaging 248 ± 27.8 pg/mL. Total tau levels in cord blood were significantly higher than in adult plasma (Figure 1A). There was also a trend toward higher total tau levels in neonatal tracheal aspirate samples compared to adult plasma, although this difference did not reach statistical significance.

Figure 1. Tau protein levels in adult plasma, cord blood, and tracheal aspirates, with comparisons between preterm and term infants.

Figure 1.

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(1A) Tau protein concentrations (pg/mL) measured in adult plasma, cord blood, and tracheal aspirate samples. Cord blood and tracheal aspirates showed significantly higher tau levels compared to adult plasma. (1B) Comparison of tau levels in tracheal aspirates between preterm and term infants. Preterm infants exhibited significantly elevated tau concentrations (p < 0.01). (1C) Summary table of clinical characteristics for preterm and term infants from whom cord blood was collected. (1D) Tau protein concentrations in cord blood samples from preterm and term infants. Preterm cord blood samples showed significantly higher tau levels (p < 0.05). Statistical significance is indicated by **** (p < 0.0001), ** (p < 0.01), * (p<0.05), and ns (not significant). Comparisons among more than two groups were performed using the Kruskal-Wallis test with Dunn’s multiple correction, and comparisons between two groups were performed using the Mann-Whitney U test.

Subgroup analyses revealed notable differences in tau protein concentration between term and preterm infants. In tracheal aspirates, total tau concentrations were significantly higher in preterm infants compared to term infants (80.5 ± 13.3 vs. 14.2 ± 4.5 pg/ml, p < 0.01; Figure 1B). To account for potential confounding by antenatal corticosteroid exposure (ACS) and intrauterine inflammation, a restricted analysis was performed including only preterm infants without ACS exposure and without clinical chorioamnionitis. In this subgroup, tau levels remained higher compared to term infants, although the difference was not statistically significant (36.0 ± 13.6 vs. 11.6 ± 4.1 pg/mL, p = 0.11).

Similarly, cord blood from preterm infants showed elevated tau levels relative to term infants (312.4 ± 37.8 vs. 184.2 ± 30.2 pg/ml, p < 0.05; Figures 1C and 1D). This difference persisted when the analysis was limited to infants without clinical chorioamnionitis (289.7 ± 33.9 vs. 184.2 ± 30.2 pg/mL, p < 0.05). All preterm infants in the cord blood cohort had received ACS, precluding subgroup analyses based on corticosteroid exposure. Notably, cord blood tau levels in term infants without ACS or clinical chorioamnionitis remained significantly higher than adult plasma (184.2 ± 30.2 vs. 4.7 ± 0.5 pg/mL, p < 0.01).

2. Tau variants isolated from the airways of premature infants can lead to neuronal tau aggregation

To further investigate the relationship between gestational age and tau protein levels in the respiratory tract of preterm infants, tracheal aspirate samples were grouped by gestational age: 22–24 weeks, 25–28 weeks, and 29–32 weeks. We observed that total tau protein was present in all tracheal aspirate samples as early as 22 weeks of gestational age, and the concentration level did not change with gestational age groups (Figure 2A).

Figure 2. Tau protein levels and neuronal tau aggregation across gestational age groups in preterm infants.

Figure 2.

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(2A) Tau protein concentrations (pg/mL) measured in tracheal aspirates from preterm infants grouped by gestational age: 22–24 weeks, 25–28 weeks, and 29–32 weeks. No significant differences were observed between all groups. (2B) BiFC assay results showing neuronal tau aggregation (%) in HEK 293 cells exposed to tracheal aspirates from the same gestational age groups. Nearly all samples induced tau aggregation (BiFC activity >100%); 5 samples did not meet the threshold. No significant differences in BiFC signals were observed between gestational age groups (p > 0.05). Statistical significance is indicated by * and ns (not significant) using the Kruskal-Wallis test with Dunn’s multiple comparisons correction. BIFC: Biomolecular Fluorescence Complementation.

To determine whether tracheal aspirate samples collected from these mechanically ventilated preterm infants expressed pathogenic tau variants, we evaluated the ability of tracheal aspirates from preterm infants to induce neuronal tau aggregation using a BiFC assay. We found no difference in cytopathic tau levels between the gestational age groups; however, tracheal aspirates from each group consistently seeded neuronal tau aggregation in vitro. These findings suggest that tau derived from the premature mechanically ventilated lung possesses intrinsic pathogenic potential.

3. Histological chorioamnionitis enhances the neuronal tau aggregation activity in tracheal aspirates:

We next questioned whether the total tau and cytopathic tau concentration was dependent on intrauterine inflammation. To investigate the involvement of tau protein in the context of histologic chorioamnionitis, infants born at ≤32 weeks’ gestation and at risk for BPD were stratified based on the presence or absence of histologic chorioamnionitis as determined by placental pathology. Total tau concentration in tracheal aspirates did not differ between the two groups (Figure 3A). These findings suggest that exposure to histologic chorioamnionitis does not affect the overall tau concentration in tracheal aspirates.

Figure 3. Tau Expression and Aggregation in Preterm Infants with and Without Histological Chorioamnionitis.

Figure 3.

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(3A) Total tau concentrations in tracheal aspirates from infants born at ≤32 weeks’ gestation, stratified by the presence or absence of histological chorioamnionitis. No statistically significant difference was observed between groups, despite notable inter-individual variability. (3B) BiFC fluorescence analysis of tau aggregation in the same cohort. Infants exposed to histological chorioamnionitis exhibited significantly increased fluorescence intensity compared to those without exposure (3C). Representative histologic images with or without chorioamnionitis images. (3D) Representative BiFC fluorescence micrographs. HBSS and cAMP are used as negative and positive controls, respectively. The intensity of the yellow fluorescence reflects the extent of neuronal tau aggregation. Vertical colorimetry indicates the strength of BiFC signal. The scale bar represents 100 μm. Statistical significance is indicated by * (p<0.05) and ns (not significant) using the Mann-Whitney U test. HCA: Histological Chorioamnionitis; BIFC: Biomolecular Fluorescence Complementation. cAMP: cyclic Adenosine Monophosphate.

However, BiFC fluorescence analysis demonstrated a significant increase in signal intensity among infants with histologic chorioamnionitis compared to those without (p < 0.05), indicating enhanced neuronal tau aggregation in the presence of prenatal inflammation regardless of gestational age (Figure 3B). Importantly, in subgroup analyses restricted to infants who received ACS, total tau concentrations remained unchanged between infants with and without histologic chorioamnionitis, whereas tau aggregation was significantly increased (p < 0.05). This suggests that the association between intrauterine inflammation and increased tau aggregation is independent of corticosteroid administration. We were unable to perform a similar subgroup analysis in infants without antenatal corticosteroid exposure due to limited sample size.

4. Total tau concentration or cytopathic tau aggregation in tracheal aspirates did not predict the development of BPD:

We further investigated the potential role of tau in predicting BPD development. Infants born at ≤32 weeks’ gestation were stratified into two outcome groups: those who developed Grade 2 or 3 BPD or died before 36 weeks’ postmenstrual age, and those with Grade 0 or 1 BPD. Tracheal aspirates analysis revealed no statistically significant differences in total tau concentrations between the two groups (Figure 4A). Infants with Grade 0 or 1 BPD exhibited a wide range of tau levels, with substantial overlap compared to those with Grade 2 or 3 BPD or who died. BiFC analysis showed a trend toward increased tau aggregation activity in the Grade 2 or 3 BPD/death group; however, this increase was also not statistically significant (Figure 4B, p = 0.41). Additionally, subgroup analyses accounting for ACS exposure and histologic chorioamnionitis showed no significant differences in either total tau levels or tau aggregation between the two groups.

Figure 4: Tau Expression and Aggregation in Preterm Infants Across BPD Severity Grades and Mortality Outcomes.

Figure 4:

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(4A) Total tau concentrations measured in tracheal aspirates from infants born at ≤32 weeks’ gestation were stratified into two groups: Grade 0 or 1 BPD and Grade 2 or 3 BPD or death. Although individual variability was pronounced, no statistically significant differences were observed between groups. (4B) Tau aggregation assessed via BiFC fluorescence analysis in the same cohort revealed no significant differences between the two groups. Statistical significance is indicated by ns (not significant) using the Mann-Whitney U test. BPD: Bronchopulmonary Dysplasia; BIFC: Biomolecular Fluorescence Complementation.

Overall, these findings suggest that early postnatal tau expression in the airways, whether assessed by total protein abundance or pathogenic aggregation potential, does not reliably distinguish infants who progress to severe BPD or mortality from those with milder outcomes.

5. Duration of mechanical ventilation does not affect total tau concentration or cytopathic tau aggregation

All tracheal aspirate samples were collected from mechanically ventilated term and preterm infants within the first seven days of intubation. To assess the effect of mechanical ventilation on tau expression, Spearman correlation analyses were performed between duration of mechanical ventilation and tracheal aspirate tau concentrations. No significant association was observed (r = 0.051, 95% CI −0.236 to 0.329, p = 0.724). Similarly, tau aggregation measured by BiFC analysis was not correlated with ventilation duration (r = −0.17, 95% CI −0.47 to 0.16, p = 0.313). These findings suggest that mechanical ventilation alone is unlikely to be the primary driver of elevated tau levels in this cohort. Nevertheless, as tracheal aspirates from mechanically ventilated adults were not available, we cannot fully exclude a potential contribution of ventilation-related stress to tau expression in infants.

6. Common perinatal risk factors are not described by total tau levels and neuronal tau aggregation

We also evaluated the impact of various perinatal risk factors on total tau levels and neuronal tau aggregation. Maternal conditions, including pregnancy-induced hypertension and diabetes, showed no significant association with tau concentrations or cytotoxicity (Figures 5A-5D). Similarly, antenatal corticosteroid administration and mode of delivery did not influence tau levels or aggregation patterns (Figures 5E-5H).

Figure 5. Maternal and Neonatal Risk Factors Do Not Significantly Influence Tau Concentration or Aggregation in Neonates.

Figure 5.

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Total Tau levels and Tau aggregation were assessed using the BiFC assay across various maternal and neonatal conditions. (5A, 5B) Infants born to mothers with or without pregnancy-induced hypertension showed no significant differences in Tau concentration or aggregation. (5C, 5D) No statistical differences were observed between infants born to mothers with or without diabetes. (5E, 5F) Exposure to antenatal corticosteroids did not significantly alter Tau measures. (5G, 5H) Mode of delivery (vaginal vs. cesarean section) had no impact on Tau concentration or aggregation. (5I–5L) Stratification by infant gender (5I, 5J) and race (5K, 5L) revealed no significant differences in Tau metrics. Statistical significance is indicated by ns (not significant) using the Mann-Whitney U test. BIFC: Biomolecular Fluorescence Complementation; PIH: Pregnancy Induced Hypertension; DM: Diabetes Mellitus; ACS: Antenatal Corticosteroids.

Among neonatal variables, gestational age emerged as the only factor associated with changes in tau metrics. In contrast, neonatal gender and ethnicity demonstrated no measurable effect on total tau or cytopathic tau levels (Figures 5I-5L)

Discussion:

In this exploratory study, we observed that total tau protein concentrations were highest in preterm infants compared to term infants and were lowest in adults. This developmental gradient between preterm and term infants was consistently evident in both cord blood and tracheal aspirates. Notably, tracheal aspirates from preterm infants induced neuronal tau aggregation, with increased activity in samples derived from neonates exposed to maternal histological chorioamnionitis. To our knowledge, this is the first report to describe the presence of tau variants within the neonatal lung.

Our findings align with prior reports documenting elevated levels of phosphorylated tau at serine 217 in the plasma samples of preterm infants relative to term infants and healthy young adults (26). We also found increased total tau concentrations in cord blood obtained from preterm infants relative to term infants and healthy adults. This increase in the systemic tau levels suggests that tau expression is developmentally regulated and may reflect a transcriptional program essential for early organ development. Furthermore, the detection of total tau in tracheal aspirates as early as 22 weeks of gestation, with higher levels in preterm lungs compared to term, underscores its potential role in pulmonary morphogenesis. Tau is known to stabilize microtubules (25, 26) and regulate endothelial cytoskeletal architecture (27, 28), suggesting a plausible role in cellular organization and intercellular interactions during lung development. However, we did not characterize tau isoforms, and the differential roles of fetal versus adult isoforms in organ development remain to be elucidated.

The cellular origin of tau in cord blood and tracheal aspirates remains undefined. Both neuronal and non-neuronal cell types express tau, and multiple isoforms have been identified in lung-resident populations, including pericytes, alveolar fibroblasts, GCap cells, Acap cells, and lymphatic endothelial cells (29). The detection of tau in both airway and circulatory compartments, in the absence of isoform-specific resolution, suggests a heterogeneous cellular source and highlights the need for further investigation into the origin and regulation of tau expression in the developing lung.

Beyond total tau levels, we also examined the presence of pathological tau variants in the neonatal lung. In adult populations, lower respiratory tract infections have been shown to induce cytotoxic tau, contributing to end-organ dysfunction (19–22). In our cohort, cytopathic tau was consistently detected in tracheal aspirates from mechanically ventilated preterm infants independent of postnatal infection status. This observation suggests that non-infectious stimuli may have contributed to the release of tau, or alternatively, that the transition to air-breathing life concurrent with exposure to lung microbiome triggers tau release. Notably, preterm infants exposed to maternal histological chorioamnionitis exhibited higher levels of cytotoxic tau.

Mechanical ventilation and hyperoxia are well-established sources of oxidative stress in the immature lung, promoting the generation of reactive oxygen species (ROS) that activate inflammatory cascades and cytokine release. These processes exacerbate alveolar and endothelial injury, compromise microvascular integrity, and impair alveolar development (30–35). Prenatal inflammation, such as histological chorioamnionitis, further primes fetal tissues for increased susceptibility to postnatal stressors, although the molecular mediators remain incompletely defined (36–40).

Within this context, ROS and inflammatory signals converge on stress response pathways, particularly p53, a key regulator of cellular responses to DNA damage, oxidative stress, and inflammation (41, 42). Neurobiological studies have shown that p53 activation can promote tau phosphorylation and aggregation (43–45), and recent work suggests that tau plays a role in alveolar type 2 (AT2) cell differentiation (46). Together, these findings suggest that tau may act as a downstream effector of p53-mediated stress responses, linking prenatal inflammation and postnatal oxidative injury to cytopathic tau accumulation. This p53–tau axis may represent a critical mechanism influencing alveolar–capillary development and repair in the preterm lung.

Evidence also suggests a potential interplay between corticosteroids and tau signaling in the brain (47–49). In our cohort, ACS exposure did not significantly affect total or cytopathic tau levels, which may reflect the small sample size or the influence of placental metabolism on tau. Nonetheless, the possibility that ACS impacts tau post-translational modifications and aggregation cannot be excluded. Taken together, these observations highlight a potential interplay between prenatal inflammation, oxidative stress, corticosteroid exposure, and tau signaling in the developing lung, which may influence injury and repair processes.

This study has several limitations. The sample size was relatively small, which limited the ability to perform detailed subgroup analyses. Histological chorioamnionitis data were not available for all patients, and proinflammatory profiles of tracheal aspirates were not assessed, precluding direct correlations with total tau levels or tau aggregation. Analyses of tau aggregation were not performed on cord blood or tracheal aspirates from term infants, and mechanically ventilated adults were not included in the study for comparison.

In conclusion, this study demonstrates that total tau concentrations are elevated in neonates relative to adults, with significantly higher levels observed in preterm infants. We also identified increased cytopathic tau in tracheal aspirates from mechanically ventilated preterm neonates, particularly among those exposed to maternal histological chorioamnionitis. These findings suggest that both prenatal and postnatal inflammatory exposures may contribute to aberrant tau phosphorylation and misfolding. Although tau expression was elevated following perinatal inflammation, it did not correlate with the subsequent development of BPD, potentially due to the limited sample size. Further mechanistic studies are warranted to determine the role of tau dysregulation in the pathogenesis of neonatal lung injury and development, as well as to evaluate its potential utility as a biomarker or therapeutic target.

ACKNOWLEDGEMENTS:

We would like to thank the parents, respiratory therapists, nurses, neonatal nurse practitioners and physicians involved in the care and management of these neonates. Graphical abstract created with a licensed version of BioRender.com.

GRANTS:

This work was supported in part by HL167997 (Troy Stevens), HL148069 (Troy Stevens), and HL140182 (Mike Lin)

Footnotes

DISCLOSURES: No conflicts of interest, financial or otherwise, are declared by the authors.

DATA AVAILABILITY:

Data will be made available upon reasonable request.

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