Stem/progenitor cell-driven immune microenvironment remodeling in sepsis-associated acute respiratory distress syndrome

Abstract

BACKGROUND

Sepsis-associated acute respiratory distress syndrome (ARDS) is characterized by diffuse alveolar epithelial injury, dysregulated immune activation, and impaired inflammation resolution. Alveolar epithelial stem/progenitor cells are critical for restoring alveolar integrity; however, their phenotypic changes and association with local and systemic immune microenvironments remain insufficiently defined.

AIM

To investigate the relationship between phenotypic changes in alveolar epithelial stem cells/progenitor cells and the immune microenvironment imbalance in sepsis-associated ARDS and evaluate its correlation with the severity of the disease and intensive care unit (ICU) outcomes and to provide a basis for individualized intervention based on epithelial repair and immune regulation.

METHODS

A total of 200 patients with sepsis-ARDS who were admitted to the ICU of Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, from January 2023 to December 2025, were retrospectively included. They were divided into a moderate group (n = 111) and a severe group (n = 89) according to Berlin’s criteria. Bronchoalveolar lavage fluid (BALF) and peripheral blood were collected within 48 hours after tracheal intubation. Quantitative polymerase chain reaction was used to detect the relative expression of alveolar epithelial type II cells progenitor cell marker surfactant protein C (SFTPC) in BALF cell pellets, and the proportion of epithelial cell adhesion molecule and CD44-positive cells was determined by flow cytometry. The T helper 17 cells (Th17)/regulatory T cells (Treg) ratio in BALF, the ratio of CD4+/CD8+ T cells, and plasma interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and IL-10 were detected simultaneously. Blood lactate, ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO₂/FiO₂), sequential organ failure assessment (SOFA)/acute physiology and chronic health evaluation II scores, and duration of mechanical ventilation, ICU stay, and 28-day mortality were recorded.

RESULTS

In the severe group, SOFA, acute physiology and chronic health evaluation II, and lactic acid levels significantly increased, whereas PaO₂/FiO₂ decreased (all P < 0.001). Compared with the moderate group, the severe group had significantly decreased SFTPC and epithelial cell adhesion molecule, and increased CD44 (P < 0.001); the Th17/Treg ratio was increased, but the proportion of CD4+ T cells was decreased, and the proportion of CD8+ T cells was increased. IL-6 and tumor necrosis factor-α were significantly increased (P < 0.05). Correlation analysis showed that SFTPC was negatively correlated with Th17/Treg, IL-6, and lactic acid levels and positive correlated with PaO₂/FiO₂ (r = 0.510, P < 0.001). Multivariate logistic regression analysis indicated that SOFA (odds ratio = 1.33, P = 0.005) and SFTPC (odds ratio = 0.03, P = 0.002) were independent predictors of 28-day mortality.

CONCLUSION

The phenotypic decline of alveolar epithelial type II cells progenitor cells in sepsis-ARDS is associated with an imbalance in T cell subsets and increased levels of inflammatory factors, which are also closely related to oxygenation disorders and adverse outcomes. Epithelial repair-related indicators such as SFTPC can be used for risk stratification and suggest potential avenues for translational intervention.

Key Words: Sepsis; Acute respiratory distress syndrome; Alveolar epithelial type II cells; Progenitor cells; Inflammatory factors; Lactic acid; Prognosis

Core Tip: In sepsis-acute respiratory distress syndrome, the downregulation of alveolar epithelial type II cells progenitor markers (surfactant protein C, epithelial cell adhesion molecule) is accompanied by T-cell subset imbalance and elevated proinflammatory cytokines, which are closely associated with disease severity, oxygenation impairment and increased lactate; surfactant protein C and sequential organ failure assessment score are independent predictors of 28-day mortality, suggesting that stem/progenitor cell-mediated immune microenvironment remodeling may serve as a promising prognostic indicator and therapeutic target for sepsis-acute respiratory distress syndrome.

INTRODUCTION

Sepsis is an infection-induced host response disorder that causes life-threatening organ dysfunction, and death is mainly related to immune-inflammatory disorders, microcirculation perfusion insufficiency, and multiple organ failure[1,2]. The lung is one of the most vulnerable target organs in sepsis, and when sepsis develops into acute respiratory distress syndrome (ARDS), mortality and medical burden increase significantly[3,4]. In sepsis-ARDS, pathogen- and damage-associated signals activate alveolar macrophages, neutrophils, endothelial cells, and lymphocytes, leading to cytokine release, epithelial-endothelial barrier leakage, disordered coagulation, and impaired alveolar fluid clearance. As the disease progresses, excessive inflammatory activation may coexist with lymphocyte depletion, T-cell exhaustion, and compensatory anti-inflammatory responses, which partly explains persistent organ dysfunction and secondary infection risk. Recent studies have suggested that sepsis-associated ARDS (sepsis-ARDS) is not the result of a simple “cytokine storm”. Failure of alveolar epithelial barrier repair continuously damages gas exchange[5,6]. However, the composition and function of immune cells in the alveolar cavity show dynamic changes, which can lead to continuous inflammation and may enter the immunosuppressive stage, thus increasing the risk of secondary infections and organ failure[7,8]. In terms of epithelial repair, alveolar epithelial type II cells (AEC II) are not only the main source of surface-active substances, but also have regenerative potential and can differentiate into AEC I cells and participate in alveolar re-epithelization[9,10]. Animal and human studies have shown that AEC II-related genes [such as surfactant protein C (SFTPC)] and epithelial cell surface molecules [such as the epithelial cell adhesion molecule (EPCAM)] are closely related to the repair of lung injury[11,12]. Some subsets (such as CD44-positive cells) can exhibit different proliferation and migration characteristics after injury[13,14]. Immunologically, the imbalance of T cell subsets is considered to be related to the persistent inflammation and tissue damage in ARDS, wherein the change in the T helper 17 cell (Th17)/regulatory T cell (Treg) ratio can reflect the tension between inflammation and immunosuppression[15,16]. At the same time, pro-inflammatory factors such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) as well as immunosuppressive factors such as IL-10 are involved in disease progression[17]. However, the correspondence between phenotypic changes in epithelial progenitor cells and immune microenvironment imbalance and their association with metabolic burden (such as lactic acid) and outcomes still lack systematic validation within the same clinical cohort. Based on this, in this study, AEC II progenitor cell markers and immune indicators in bronchoalveolar lavage fluid (BALF) and peripheral blood were jointly detected in patients with sepsis-ARDS admitted to the intensive care unit (ICU) over a 3-year period, and the corresponding analysis was conducted with ARDS severity, oxygenation status, lactic acid level, and ICU outcomes, emphasizing the clinical association, prognostic relevance, and translational significance, to provide clinically relevant data support for subsequent mechanistic and interventional research.

MATERIALS AND METHODS

Clinical data

This was a single-center, retrospective study. Two hundred patients with ARDS who were admitted to the ICU and met the criteria for sepsis-3 diagnosis between January 2023 and December 2025 were included in the study. ARDS was determined according to the Berlin’s criteria and the lowest ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO₂/FiO₂) within 24 hours after ICU admission, patients were divided into two groups: Moderate group (100-200 mmHg) and severe group (≤ 100 mmHg). In total, 111 patients and 89 patients were assigned to the moderate and severe groups, respectively. Inclusion criteria: (1) Age ≥ 18 years; (2) Met with sepsis-3 diagnostic criteria; (3) Imaging showed bilateral lung infiltration, which cannot be explained by cardiogenic edema; and (4) Invasive mechanical ventilation was performed, and BALF and peripheral blood collection were completed within 48 hours after intubation. The exclusion criteria were as follows: (1) Pre-existing interstitial lung disease, active pulmonary tuberculosis, or end-stage pulmonary fibrosis; (2) Malignant tumors of the hematological system with severe immunosuppression and expected survival < 48 hours after chemotherapy; (3) Pregnancy; and (4) Missing key information. This study was conducted in accordance with the Declaration of Helsinki and approved by the Hospital Ethics Committee. Owing to the retrospective nature of the study and the use of anonymized data, the requirement for informed consent was waived. The data were extracted using delabeling, which met the requirements for personal information protection.

Sample collection and detection

BALF and peripheral blood: Total of 20-40 mL BALF was collected according to a routine bronchoscopic lavage procedure in the ICU, and cell pellets was obtained by centrifugation for nucleic acid extraction and flow cytometry. BALF was centrifuged at 4 °C and 3000 rpm for 10 minutes using a refrigerated centrifuge (Eppendorf 5810R, Eppendorf, Hamburg, Germany); the cell pellet was washed with cold phosphate-buffered saline, used immediately for flow cytometry, or stored at -80 °C for subsequent RNA extraction. 2-4 mL venous blood was collected for plasma separation and inflammatory factor detection. Peripheral venous blood was centrifuged at 4 °C and 3000 rpm for 10 minutes within 30 minutes after collection, and separated plasma was aliquoted and stored at -80 °C before enzyme-linked immunosorbent assay (ELISA) detection.

AEC II progenitor cell markers: The relative expression level of SFTPC (2^-ΔΔCt, GAPDH as the internal reference) was detected by quantitative polymerase chain reaction. Total RNA was extracted using TRIzol reagent (Invitrogen, Thermo Fisher Scientific, Waltham, MA, United States), reverse-transcribed with PrimeScript RT reagent kit (Takara Bio, Shiga, Japan), and amplified with TB Green Premix Ex Taq II on a CFX96 Real-Time PCR Detection System (Bio-Rad, Hercules, CA, United States). The ratio of EPCAM/CD44-positive cells (based on CD45-negative epithelial-gated cells) was determined using flow cytometry. Fluorochrome-conjugated antibodies against CD45, EPCAM, and CD44 were purchased from BD Biosciences (San Jose, CA, United States), and samples were analyzed on a BD FACSCanto II flow cytometer using FlowJo software (Tree Star/BD Biosciences, Ashland, OR, United States).

Immune indicators: The proportion of CD4+ and CD8+ T cells in the BALF and the proportion of Th17 (CD4+IL17A+) to Treg (CD4+CD25+Foxp3+) cells were detected by flow cytometry, and the Th17/Treg ratio was calculated. Flow cytometric antibodies against CD3, CD4, CD8, IL-17A, CD25, and Foxp3 were obtained from BD Biosciences (San Jose, CA, United States) or BioLegend (San Diego, CA, United States) according to the laboratory protocol. Plasma IL-6, TNF-α, and IL-10 were determined by ELISA. Commercial ELISA kits for IL-6, TNF-α, and IL-10 were purchased from R&D Systems (Minneapolis, MN, United States), and absorbance was read on a BioTek ELx808 microplate reader (BioTek Instruments, Winooski, VT, United States).

Metabolic and clinical indicators: Including lactic acid, PaO₂/FiO₂, sequential organ failure assessment (SOFA), and acute physiology and chronic health evaluation II scores in arterial blood on the first day of ICU admission were recorded. The outcome indicators included the duration of mechanical ventilation, ICU stay, and 28-day mortality.

Statistical analysis

Measurement data were expressed as mean ± SD or median (interquartile range) after normality testing, and intergroup comparisons were performed using t-test or Mann-Whitney U test. The count data were expressed as the n (%) and the comparison between groups was performed using the χ² test. Spearman’s correlation analysis was used. A multivariate logistic regression model was constructed with 28-day mortality as the dependent variable, and odds ratio (OR) and 95% confidence intervals (CIs) were reported. All tests were bilateral, and P < 0.05 indicated that the difference was statistically significant. Statistical analyses were performed in the R/Python environment.

RESULTS

General information and disease severity of two groups

A total of 200 patients with sepsis-ARDS were included, including 111 moderate and 89 severe cases. There were no significant differences between the two groups in terms of sex distribution, age, history of COPD or diabetes mellitus, or immunosuppressive status (all P > 0.05). Compared to the moderate group, the severe group had a higher prevalence of chronic kidney disease, higher SOFA and acute physiology and chronic health evaluation II scores, blood lactate level, mechanical ventilation duration, and ICU stay, but lower PaO₂/FiO₂ (all P < 0.001) (Table 1).

Table 1 General information and disease severity of two groups, n (%)/mean ± SD.

Indicators	Moderate group (n = 111)	Severe group (n = 89)	Statistical values	P value
Gender			χ2 = 0.002	0.964
Male	77 (69.37)	62 (69.66)
Female	34 (30.63)	27 (30.34)
History of COPD	16 (14.41)	17 (19.10)	χ2 = 0.788	0.375
Diabetes	30 (27.03)	34 (38.20)	χ2 = 2.835	0.092
Chronic kidney disease	9 (8.11)	24 (26.97)	χ2 = 12.750	< 0.001
Immunosuppressive state	7 (6.31)	10 (11.24)	χ2 = 1.543	0.214
Age (years)	64.34 ± 11.14	66.97 ± 8.74	t = 1.822	0.070
SOFA score	8.81 ± 2.12	10.59 ± 2.39	t = 5.575	< 0.001
APACHE II score	19.45 ± 4.60	23.70 ± 5.91	t = 5.719	< 0.001
PaO2/FiO2 (mmHg)	150.97 ± 24.20	91.12 ± 10.55	t = 21.727	< 0.001
Blood lactic acid (mmol/L) on the first day of ICU admission	2.65 ± 0.93	3.62 ± 1.13	t = 6.659	< 0.001
Mechanical ventilation time (days)	8.24 ± 4.44	12.43 ± 5.57	t = 5.920	< 0.001
ICU stay (days)	11.77 ± 5.87	15.46 ± 6.40	t = 4.244	< 0.001

COPD: Chronic obstructive pulmonary disease; SOFA: Sequential organ failure assessment; APACHE II: Acute physiology and chronic health evaluation II; ICU: Intensive care unit.

Phenotypic changes of AEC II progenitor cells

Compared to the moderate group, the relative expression of SFTPC in BALF cell pellets and the positive proportion of EPCAM were significantly decreased in the severe group, whereas the positive proportion of CD44 was increased (P < 0.001) (Table 2). This indicates that in the background of more severe oxygenation disorders, the signal related to the epithelial repair potential is weakened, accompanied by phenotypic enhancement related to the injury response (Figure 1).

Figure 1 Comparison of surfactant protein C/epithelial cell adhesion molecule/CD44 expression (violin plot). A: Relative expression of surfactant protein C; B: Proportion of epithelial cell adhesion molecule positive cells; C: Proportion of CD44 positive cells. STTPC: Surfactant protein C; EPCAM: Epithelial cell adhesion molecule.

Table 2 Comparison of alveolar epithelial type II cells progenitor cell-related indicators in bronchoalveolar lavage fluid, mean ± SD.

Indicators	Moderate group (n = 111)	Severe group (n = 89)	t	P value
Relative expression of SFTPC (2-ΔΔCt)	0.81 ± 0.20	0.55 ± 0.20	9.137	< 0.001
Proportion of EPCAM positive (%)	0.88 ± 0.26	0.63 ± 0.19	7.589	< 0.001
Proportion of CD44 positive (%)	0.92 ± 0.32	1.15 ± 0.26	5.483	< 0.001

SFTPC: Surfactant protein C; EPCAM: Epithelial cell adhesion molecule.

Imbalance of immune microenvironment and changes of inflammatory factors

The Th17/Treg ratio cells in the severe group was significantly higher than that in the moderate group, and the proportion of CD4+ T cells decreased, whereas the proportion of CD8+ T cells increased (P < 0.05). Plasma IL-6 and TNF-α levels as well as IL-10 were increased (P < 0.05) (Table 3). These results demonstrate a more pronounced T-cell subpopulation imbalance and systemic inflammatory response in the alveolar cavity of patients with severe ARDS (Figure 2).

Figure 2 Distribution of immune microenvironment indicators (violin plot). Th17: T helper 17 cell; Treg: Regulatory T cells; IL: Interleukin; TNF-α: Tumor necrosis factor-α.

Table 3 Imbalance of immune microenvironment and changes of inflammatory factors, mean ± SD.

Indicators	Moderate group (n = 111)	Severe group (n = 89)	t	P value
Th17/Treg ratio	1.38 (1.18-1.74)	2.05 (1.73-2.54)	-7.842	< 0.001
CD4+T cell ratio (%)	41.88 ± 6.68	35.49 ± 7.86	6.213	< 0.001
CD8+T cell ratio (%)	26.38 ± 5.68	29.02 ± 5.47	3.321	0.001
IL-6 (pg/mL)	101.70 (75.17-135.41)	183.11 (143.88-245.16)	-8.156	< 0.001
TNF-α (pg/mL)	28.93 (25.96-36.76)	40.82 (32.90-54.50)	-6.734	< 0.001
IL-10 (pg/mL)	13.86 (10.65-19.34)	15.64 (13.03-22.77)	-1.982	0.049

Th17: T helper 17 cell; Treg: Regulatory T cells; IL: Interleukin; TNF-α: Tumor necrosis factor-α.

Correlation between epithelial progenitor cell indicators and immune/metabolic load

Spearman’s correlation analysis showed that SFTPC was negatively correlated with Th17/Treg, IL-6, and lactic acid levels and positively correlated with PaO₂/FiO₂. EPCAM showed a trend similar to that of the above indicators. CD44 was positively correlated with Th17/Treg and lactic acid levels and negatively correlated with PaO₂/FiO₂ (Figure 3).

Figure 3 Heat plot of correlation between epithelial progenitor cell indicators and immune/metabolic index. ^bP < 0.01. AEC II: Alveolar epithelial type II cells; STTPC: Surfactant protein C; EPCAM: Epithelial cell adhesion molecule.

Clinical outcomes and related factors

The 28-day mortality rate in the severe group was higher than in the moderate group (P < 0.001) (Table 4, Figure 4). Multivariate logistic regression showed that increased SOFA scores and decreased SFTPC were independently associated with 28-day mortality (Table 5), suggesting that in addition to the severity of overall organ failure, decreased epithelial repair potential might be more directly correlated with adverse outcomes.

Figure 4 The 28-day survival curve or outcome comparison by surfactant protein C. STTPC: Surfactant protein C; ARDS: Acute respiratory distress syndrome.

Table 4 Comparison of clinical outcomes between the two groups, n (%)/mean ± SD.

Outcome indicators	Moderate group (n = 111)	Severe group (n = 89)	Statistical values	P value
28 days of death	20 (18.02)	47 (52.81)	χ2 = 26.838	< 0.001
Mechanical ventilation time (days)	8.24 ± 4.44	12.43 ± 5.57	t = 5.920	< 0.001
ICU stay (days)	11.77 ± 5.87	15.46 ± 6.40	t = 4.244	< 0.001

ICU: Intensive care unit.

Table 5 Multivariate logistic regression analysis of 28 days death.

Variable	β	SE	Wald χ2	OR	95%CI	P value
Severe	-0.274	0.595	0.213	0.76	0.23-2.46	0.641
Lactic acid	0.299	0.210	2.031	1.35	0.89-2.03	0.156
SOFA	0.286	0.102	7.863	1.33	1.09-1.62	0.005
SFTPC	-3.507	1.132	9.603	0.03	0.00-0.26	0.002
LogTh17/Treg	1.368	0.745	3.371	3.93	0.91-16.93	0.066
Constant term	-4.826	1.894	6.497	0.008	-	0.011

OR: Odds ratio; CI: Confidence interval; SOFA: Sequential organ failure assessment; SFTPC: Surfactant protein C; Th17: T helper 17 cell; Treg: Regulatory T cells.

DISCUSSION

In this study, the correlation between BALF epithelial progenitor cell phenotype and immune indicators in peripheral blood was analyzed, and it was found that patients with severe ARDS presented significant decreases in SFTPC and EPCAM (P < 0.05), while CD44 was significantly increased (P < 0.05). As a key molecule in AEC II, SFTPC is associated with epithelial cell homeostasis and regenerative potential. This decrease in clinical samples often suggests that AEC II is more seriously injured or has insufficient repair reserve[18,19]. Previous studies have emphasized the re-epithelization of AEC II during the recovery stage of ARDS. Some factors (such as an abnormal fibrinolytic system and continuous increase in inflammatory mediators) may inhibit the self-renewal of AEC II and affect the quality of repair[20,21]. In this study, an increase in CD44 expression was observed in the severe group, which was positively associated with a decrease in the oxygenation index and an increase in lactic acid. CD44 expression is often associated with cell migration, adhesion, and changes in the inflammatory microenvironment after injury. Some studies have suggested that the CD44-positive AEC II subgroup may exhibit different regenerative performances under specific conditions. Therefore, the observed decrease in SFTPC and EPCAM expression together with increased CD44 expression may indicate a distinct epithelial response pattern in severe sepsis-associated ARDS. This phenotype was associated with impaired oxygenation and increased metabolic burden in our cohort. However, whether these changes directly reflect impaired regenerative capacity or adaptive epithelial remodeling requires further mechanistic investigation[22,23].

In the immune microenvironment, the Th17/Treg ratio cells increased, the proportion of CD4+ cells decreased, and the proportion of CD8+ cells increased in the severe group (P < 0.05). Th17 and Treg cells represent different directions of proinflammation and immunosuppression/tolerance, respectively, and changes in their balance are of great significance in infectious inflammation and organ damage[24,25]. In the ARDS population, the increase in IL-6 in plasma and BALF is closely related to severity and prognosis[26,27]. As a classical pro-inflammatory factor, TNF-α can promote the increase of endothelial and epithelial permeability and aggravate pulmonary edema[28,29]. In this study, the proportions of immune cells and levels of inflammatory factors were analyzed in the same cohort. The results showed that in the severe group, there was a parallel phenomenon of “enhanced inflammation” and “upward shift of immunoregulatory signals” (an upward trend of IL-10), which was consistent with the common clinical complex state of “inflammation intertwined with immunosuppression”. Notably, in this study, a trend-based association between log(Th17/Treg) and death was observed in the regression model, suggesting that T-cell imbalance may indirectly affect the outcome by affecting persistent inflammation, secondary infection, and organ failure, and a single sampling may not be sufficient to fully reflect the dynamic process.

In addition, we found a stable correlation between epithelial progenitor cell markers and the immune/metabolic burden. SFTPC and EPCAM negatively correlated with Th17/Treg, IL-6, and lactic acid levels and positively correlated with PaO₂/FiO₂. Expression of CD44 was observed to show the opposite trend. Lactic acid, as a comprehensive indicator of tissue hypoperfusion and metabolic stress, has been confirmed to be related to the risk of death and the need for mechanical ventilation in many sepsis studies[30-33]. The results of this study suggest that under conditions of high lactic acid and hypoxia, the reduction in epithelial repair-related signals was more prominent, which might reflect that systemic hypoperfusion and inflammation could continuously limit the regenerative ability of AEC II through microcirculatory disorders, damaged mitochondrial function, and insufficient cell energy supply[34]. At the same time, structural changes in immune cells in the alveolar cavity and an increase in inflammatory factors further exacerbate local damage and form an irreversible vicious circle[35].

Based on the above findings, the following conclusions could be drawn: (1) In terms of risk assessment, in addition to comprehensive scores such as SOFA, early detection of epithelial repair-related indicators such as SFTPC is expected to provide additional information for sepsis-ARDS. The multivariate analysis revealed an independent association between SFTPC and mortality, suggesting its prognostic relevance; (2) In terms of intervention direction, if the reduction in epithelial repair potential is confirmed to be an interventional factor in future prospective studies, measures for promoting AEC II regeneration and improving the alveolar microenvironment may be explored based on infection control and organ support, and attention should be paid to the selection of a time window for immune regulation; and (3) With respect to the sample and platform, BALF and peripheral blood can complement each other; BALF is closer to local alveolar changes, and peripheral blood reflects systemic inflammation and metabolic load. Clinically, based on the stability of the disease and operational feasibility, a stratification strategy can be adopted. In the severe stage, blood indicators were mainly used, and when the conditions permitted, BALF cytology and molecular testing were performed to improve our understanding of intrapulmonary changes.

CONCLUSION

In the sepsis-ARDS population, decreases in AEC II progenitor cell markers SFTPC and EPCAM co-existed with increases in the immune microenvironment imbalance (increased Th17/Treg, altered CD4/CD8) and inflammatory factors, and were associated with increases in lactic acid, worsening oxygenation, and adverse outcomes; SOFA combined with SFTPC may be useful for early risk stratification. Limitations include that a retrospective single-center design may result in selection bias and residual confounding: BALF sampling lacked full-course dynamic assessment only within 48 hours after intubation. The study did not cover a broader subset of cells (such as macrophage polarization or myeloid suppressor cells) or histological validation. Looking forward, multicenter prospective follow-up and dynamic sampling should be conducted, the immune cell lineage should be expanded in combination with histological/spatial omics verification, and a comprehensive evaluation system should be constructed around “epithelial repair ability + immune regulation” to support mechanism interpretation and clinical translation.