Correspondence regarding: Lung organoids: a new frontier in neonatology and paediatric respiratory medicine

Extract

We read with interest the article by Zanetto et al. [1], on the use of lung organoids as an alternative approach to treat neonatal and paediatric respiratory diseases because of their ability to mimic functional characteristics and their capacity to be cultured long-term, in vitro, without compromising many of the phenotypical characteristics. However, we believe certain key aspects of this review raised some unanswered questions, or were not addressed in sufficient detail, that could impact on the practical implications of lung organoids as a preferred bridge between basic research and clinical applications.

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Zanetto et al. should be more focused on how to generate lung organoids from human neonatal tissues rather than describing different paediatric/neonatal diseases that can be modelled using lung organoids https://bit.ly/3XQgSgc

To the Editor:

We read with interest the article by Zanetto et al. [1], on the use of lung organoids as an alternative approach to treat neonatal and paediatric respiratory diseases because of their ability to mimic functional characteristics and their capacity to be cultured long-term, in vitro, without compromising many of the phenotypical characteristics. However, we believe certain key aspects of this review raised some unanswered questions, or were not addressed in sufficient detail, that could impact on the practical implications of lung organoids as a preferred bridge between basic research and clinical applications.

Concerning ethical considerations, in the US, the National Institutes of Health (NIH) recently announced a new funding opportunity to establish Comprehensive NAMs (new approach methodologies) Technology Development Centers to support the NIH Common Fund's Complement Animal Research In Experimentation (Complement-ARIE) (https://commonfund.nih.gov/complementarie) and Standardized Organoid Modeling (SOM) Center (https://www.nih.gov/som) programme to establish in vitro cell culture system models, to complement animal models and use cutting-edge technologies to develop standardised organoid-based NAMs, like lung organoids or any other tissue-specific organoids that deliver robust, reproducible and patient-centred research findings. Although lung organoids have become a routine in vitro research model for adult diseases because there are multiple resources available to procure adult tissues from biopsies, organ donations, tumours or scavenged tissues post-surgery or other adult tissue-derived biomaterials, it is still a global challenge to obtain fetal and/or neonatal tissues due to ethical constraints. Recently, the US has restricted the use of fetal tissues for scientific research towards drug discovery and finding cures for neonatal and paediatric diseases. This becomes a major hurdle to advance neonatal lung research. It is not clear whether the European Union regulations are an obstacle in such a scenario for fetal LO research although there are strict guidelines for human cerebral organoids in Germany, UK, Australia and China [2]. What are the authors' suggestions to overcome this problem?

Access to fetal/newborn tissues is limited, and tissues in the repository are old stock, posing potential logistical challenges and barriers. Fresh tissues are preferred because the cell viability is high and standard freezing methods may compromise the quality of tissue over the course of time making it difficult to initiate and establish the organoid culture [3]. With only a handful of centralised biorepositories for human neonatal research in the US [4, 5], UK [6] and Australia [7] there could be a long wait-time for procuring these tissues, unless research laboratories have Institutional Review Board approvals to procure tissues from the hospitals where they are located. However, it is not guaranteed that fetal/neonatal lung tissues for a specific disease are available for easy access in these centres. Some practical suggestions by the authors of the article for surmounting this problem would have been helpful.

Further questions relate to the source of the cell types used to initiate lung organoids. How accurately lung organoids derived from difference sources, such as iPSCs (induced pluripotent stem cells), hESs (human embryonic stem cells), amniotic fluid, tracheal aspirates and specific regions of the lung, mimic the disease is a critical aspect that needs to be confirmed. By using these diverse sources of cell types, specific lung organoids to mimic a specific disease can enhance the relevance to the specific lung disease to be studied. Once established, disease models can be easily manipulated either pharmacologically or genetically or environmentally.

Selecting the most appropriate method for a specific paediatric disease type is critical for successful replication of the disease model. For a neonatal disease like bronchopulmonary dysplasia (BPD), which has a multifactorial pathogenesis, there is injury/inflammation at an immature stage of lung development in addition to persistence of inflammation, concomitantly with lung growth/healing/repair over a period of weeks to months [8]. Targeted therapies can be designed only with a deeper understanding of the disease phenotypes. To design drugs for such a debilitating condition, lung organoids must be created from either diseased lungs (i.e. “established BPD” patients as the experimental group) or from other infant lungs who have died prematurely due to another nonrespiratory complication (“control” group). However, using such an experimental set-up may not yield clinically translatable results [9] as these two groups may not be developmentally appropriately matched and/or the “established BPD” lungs may not be amenable to interventions that will be curative. This aspect of selection of appropriate controls is not emphasised in the review.

Only selective well-equipped laboratories with adequate funding and skilled personnel are capable of recapitulating LO research because of the reasons mentioned above. Once a culture is established, efforts should be made to finish the experiment to avoid epigenetic changes, initiation of senescence, and genetic drift. A call for inclusive and diverse collaboration in this field for sharing of this limited supply of samples is essential to minimise the use of financial resources and avail the technical expertise of laboratories dedicated to LO research. Only under such circumstances will the field advance to a stage wherein therapeutic advances will have a positive impact in curing disease and improve the health of neonates over their lifetimes.