Pulmonary Fibrosis, Macrophage Research Jumped Since 2020

An analysis of research from 1990 to 2023 demonstrated a steady increase in literature about macrophages and pulmonary fibrosis, with the US and China leading in collaborative efforts. These findings were published in Frontiers in Medicine.¹

Between January 1990 and July 2023, there were 3479 publications on macrophages and pulmonary fibrosis, averaging about 102 papers per year. Over time, the number of publications has increased, with a fairly steady increase in publications per year starting in 2008. With just 6 included studies from 1990, the number of publications per year ranged from 57 to 117 prior to 2017, and jumped to more than 200 publications per year starting in 2020. The review authors also mentioned notable peaks in publication in 1995 and 2022, indicating significant research activity during these years.

“This increased focus underscores the evolving nature of research in this domain, suggesting potential implications for future PF [pulmonary fibrosis] treatments,” the authors said.

Research by Region

An analysis using VOSviewer software revealed that 69 countries contributed to the total number of articles on macrophages and pulmonary fibrosis. Over the past 3 decades and change, the US has led in publication count with 1297 articles (31.47%) and has strong collaborations, particularly with China, which followed with 601 articles. However, China had the highest surge in publications with a burst strength of 99.84 between 2021 and 2023.

A few other countries trailing closely behind on publications include Japan (n = 471), Germany (n = 256), and the United Kingdom (n = 191). Additionally, South Korea and Greece had the longest periods of increased publication activity, from 2018 to 2023 and 2001 to 2006, respectively, indicating sustained research interest during these times.

Institutional and Author Collaboration

Using VOSviewer software, the authors found that 2967 institutions have contributed to the 3479 publications on the correlation between macrophages and pulmonary fibrosis. Setting a threshold of 13 publications per institution identified the top 100 collaborating institutions, Harvard University emerged as the most collaborative institution, with strong ties between the University of Colorado and the National Jewish Medical and Research Center. The University of Michigan led in publication output with 107 articles, followed by the University of Colorado and the University of Pittsburgh, with 52 and 50 articles, respectively.

Aligning with China’s surge in publications in 2021, CiteSpace analysis of the top 10 institutions showed a significant increase in publications from the Chinese Academy of Medical Sciences – Peking Union Medical College, Central South University, Nanjing Medical University, and China-Japan Friendship Hospital during that time. This indicates these institutions have recently intensified their focus on research related to macrophages and pulmonary fibrosis.

A total of 17,700 authors contributed to the 3479 research articles on macrophages and pulmonary fibrosis. Setting a threshold of 8 publications per author helped identify a collaborative network among researchers. Aaron Brent Carter, MD, was the most collaborative author, and worked especially with Jennifer L. Larson-Casey, PhD, as they both worked at the University of Alabama at Birmingham. Carter and Steven L. Kunkel, PhD, University of Michigan Medical School, led in publication count with 25 articles each.

The study also highlighted that the proteins TGFβ1, TNF, and CXCL8 are the most frequently studied targets, with a particular emphasis on their roles in cytokine-cytokine receptor interaction pathways. Additionally, the research showed a connection between pulmonary fibrosis and other diseases, notably cancer, through a detailed cluster analysis.

This study’s limitations include only involving literature published in English from the last 30 years in a single database, as well as the use of complex bibliometric algorithms, which lack transparency and interpretability and may introduce biases from self-citation and coauthorship citations, according to the authors.

“Research on the relationship between macrophages and PF is primarily concentrated in the fields of molecular biology and medicine, with a notable emphasis on the subfield of zoology,” the authors said. “This suggests that studies related to macrophages and PF are more oriented toward experimental levels. In the future, exploring the correlation between macrophages and PF through experimental approaches could contribute to better clinical drug applications and disease treatments.”

What Are Pulmonary Fibrosis and Macrophages?

Pulmonary fibrosis is a lung disease characterized by damaged and scarred lung tissue, making it difficult for the lungs to function properly.² The condition worsens over time, leading to increased shortness of breath. While the cause is often unknown—then referred to as idiopathic pulmonary fibrosis—treatments can slow progression and improve quality of life, with lung transplants being an option for some patients.

Macrophages are white blood cells that play a crucial role in the immune system by engulfing and digesting microorganisms, clearing debris and dead cells, and stimulating other immune cells.³ They provide innate immunity and secrete anti-inflammatory cytokines to aid in tissue repair. Derived from monocytes, macrophages are found in various organs and tissues throughout the body, including the liver, brain, bones, lungs, and blood.

References

1. Min Y, Wu L, Xu C, et al. Macrophages and pulmonary fibrosis: a bibliometric and visual analysis of publications from 1990 to 2023. Front Med (Lausanne). 2024;11:1374177. doi:10.3389/fmed.2024.1374177
2. Pulmonary fibrosis. Mayo Clinic. Accessed July 10, 2024. https://www.mayoclinic.org/diseases-conditions/pulmonary-fibrosis/symptoms-causes/syc-20353690
3. Guo L. Macrophages: what are they, different types, function, and more. Osmosis. Updated July 14, 2022. Accessed July 10. 2024. https://www.osmosis.org/answers/macrophages