An Innovative Model of Bronchopulmonary Dysplasia in Premature Infants

Protective effect of recombinant interleukin-10 on newborn rat lungs exposed to short-term sublethal hyperoxia

BACKGROUND

Lung injury imposed by hyperoxia is the main cause of bronchopulmonary dysplasia in newborns. These injuries are generated from the early stage of hyperoxia through the main biologic effects of cell death and inflammatory response. Interleukin (IL)-10 is a potent anti-inflammatory cytokine that may have the inhibitory effects on these biologic actions induced by hyperoxia.

PURPOSE

Based on our former in vitro studies investigating the effect of recombinant IL-10 (rIL-10) on protecting cultured alveolar type II cells exposed to short-term hyperoxia, we performed the in vivo study to investigate the effect of rIL-10 in newborn rats aged P4 exposed to hyperoxia.

METHODS

Rats were classified into 3 groups; the control group exposed to normoxia for 24 hours; the hyperoxia group exposed to 65% hyperoxia for 24 hours; and the IL10 group treated with intratracheal instillation of rIL-10 prior to exposure to 65% hyperoxia for 24 hours. Following each treatment, the rats were euthanized. Individual lobes of the right lung were prepared for hematoxyling and eosin (H&E) staining and immunohistochemical staining for thyroid transcription factor-1 (TTF1). Bronchoalveolar lavage (BAL) was performed in the left lung to analyze cell counts and cytokines.

RESULTS

The IL10 group showed preserved air spaces similar to the control group, with decreased cellularity compared to the hyperoxia group, whereas the hyperoxia group showed markedly reduced air spaces with increased cellularity compared to the IL10 group. And, the IL10 group showed more TTF1-positive cells, which represented alveolar type II cells, compared to the hyperoxia group. Inflammatory cells, such as neutrophils and lymphocytes and proinflammatory cytokines of tumor necrosis factor-α, IL-1α, IL-8, and macrophage inflammatory protein-1α were significantly lower in BAL fluid of the IL10 group compared to the hyperoxia group.

CONCLUSION

These results indicate that rIL-10 may be a promising pharmaceutical measure for protecting newborn lungs from injury induced at the early stage of hyper oxia.

[Role and mechanism of epithelial-mesenchymal transition in a rat model of bronchopulmonary dysplasia induced by hyperoxia exposure]

OBJECTIVES

To investigate the role and mechanism of epithelial-mesenchymal transition (EMT) in a rat model of bronchopulmonary dysplasia (BPD).

METHODS

The experiment consisted of two parts. (1) Forty-eight preterm rats were randomly divided into a normoxia group and a hyperoxia group, with 24 rats in each group. The hyperoxia group was exposed to 85% oxygen to establish a BPD model, while the normoxia group was kept in room air at normal pressure. Lung tissue samples were collected on days 1, 4, 7, and 14 of the experiment. (2) Rat type II alveolar epithelial cells (RLE-6TN) were randomly divided into a normoxia group (cultured in air) and a hyperoxia group (cultured in 95% oxygen), and cell samples were collected 12, 24, and 48 hours after hyperoxia exposure. Hematoxylin-eosin staining was used to observe alveolarization in preterm rat lungs, and immunofluorescence was used to detect the co-localization of surfactant protein C (SPC) and α-smooth muscle actin (α-SMA) in preterm rat lung tissue and RLE-6TN cells. Quantitative real-time polymerase chain reaction and protein immunoblotting were used to detect the expression levels of EMT-related mRNA and proteins in preterm rat lung tissue and RLE-6TN cells.

RESULTS

(1) Compared with the normoxia group, the hyperoxia group showed blocked alveolarization and simplified alveolar structure after 7 days of hyperoxia exposure. Co-localization of SPC and α-SMA was observed in lung tissue, with decreased SPC expression and increased α-SMA expression in the hyperoxia group at 7 and 14 days of hyperoxia exposure compared to the normoxia group. In the hyperoxia group, the mRNA and protein levels of TGF-β1, α-SMA, and N-cadherin were increased, while the mRNA and protein levels of SPC and E-cadherin were decreased at 7 and 14 days of hyperoxia exposure compared to the normoxia group (P<0.05). (2) SPC and α-SMA was observed in RLE-6TN cells, with decreased SPC expression and increased α-SMA expression in the hyperoxia group at 24 and 48 hours of hyperoxia exposure compared to the normoxia group. Compared to the normoxia group, the mRNA and protein levels of SPC and E-cadherin in the hyperoxia group were decreased, while the mRNA and protein levels of TGF-β1, α-SMA, and E-cadherin in the hyperoxia group increased at 48 hours of hyperoxia exposure (P<0.05).

CONCLUSIONS

EMT disrupts the tight connections between alveolar epithelial cells in a preterm rat model of BPD, leading to simplified alveolar structure and abnormal development, and is involved in the development of BPD. Citation:Chinese Journal of Contemporary Pediatrics, 2024, 26(7): 765-773.

The benefits, limitations and opportunities of preclinical models for neonatal drug development

Increased research to improve preclinical models to inform the development of therapeutics for neonatal diseases is an area of great need. This article reviews five common neonatal diseases - bronchopulmonary dysplasia, retinopathy of prematurity, necrotizing enterocolitis, perinatal hypoxic-ischemic encephalopathy and neonatal sepsis - and the available in vivo, in vitro and in silico preclinical models for studying these diseases. Better understanding of the strengths and weaknesses of specialized neonatal disease models will help to improve their utility, may add to the understanding of the mode of action and efficacy of a therapeutic, and/or may improve the understanding of the disease pathology to aid in identification of new therapeutic targets. Although the diseases covered in this article are diverse and require specific approaches, several high-level, overarching key lessons can be learned by evaluating the strengths, weaknesses and gaps in the available models. This Review is intended to help guide current and future researchers toward successful development of therapeutics in these areas of high unmet medical need.

A Review of Placenta and Umbilical Cord-Derived Stem Cells and the Immunomodulatory Basis of Their Therapeutic Potential in Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a devastating lung disorder of preterm infants as a result of an aberrant reparative response following exposures to various antenatal and postnatal insults. Despite sophisticated medical treatment in this modern era, the incidence of BPD remains unabated. The current strategies to prevent and treat BPD have met with limited success. The emergence of stem cell therapy may be a potential breakthrough in mitigating this complex chronic lung disorder. Over the last two decades, the human placenta and umbilical cord have gained increasing attention as a highly potential source of stem cells. Placenta-derived stem cells (PDSCs) and umbilical cord-derived stem cells (UCDSCs) display several advantages such as immune tolerance and are generally devoid of ethical constraints, in addition to their stemness qualities. They possess the characteristics of both embryonic and mesenchymal stromal/stem cells. Recently, there are many preclinical studies investigating the use of these cells as therapeutic agents in neonatal disease models for clinical applications. In this review, we describe the preclinical and clinical studies using PDSCs and UCDSCs as treatment in animal models of BPD. The source of these stem cells, routes of administration, and effects on immunomodulation, inflammation and regeneration in the injured lung are also discussed. Lastly, a brief description summarized the completed and ongoing clinical trials using PDSCs and UCDSCs as therapeutic agents in preventing or treating BPD. Due to the complexity of BPD, the development of a safe and efficient therapeutic agent remains a major challenge to both clinicians and researchers.