Long-term lung healing even after mild or moderate COVID-19. Many could develop lung fibrosis

COVID-19 News - Months of Healing Even After Mild COVID-19
COVID-19 has had a profound impact on the world, affecting millions of lives. While much attention has been given to severe cases, a new study sheds light on the long-term lung repair that continues months after recovery, even in mild to moderate cases. This research led by scientist from the U.S. NIH that is covered in this COVID-19 News report, reveals surprising findings about the persistence of lung repair processes long after symptoms have subsided.


Long-term lung healing even after mild or moderate COVID-19. 
 
The Study: An Overview
The study involved 45 patients with mild to moderate COVID-19. Researchers collected samples of bronchoalveolar lavage (BAL), a fluid from the lungs, at three different stages: acute (shortly after symptom onset), recovery, and convalescent (up to 9 months post-symptom onset). The goal was to understand how the lung's protein landscape changes over time and what this means for long-term recovery.
 
Initial Findings: The Acute Phase
During the acute phase of COVID-19, the lung's protein profile showed significant inflammation and tissue damage. Proteins associated with the body's defense mechanisms and tissue repair were highly active. This is the body's natural response to the viral attack, aiming to control the infection and start the healing process.
 
In particular, the study identified two distinct groups of patients during the acute phase, based on the severity of their symptoms and the activity of specific proteins in their lungs. One group showed a more severe inflammatory response, while the other had a milder reaction. This difference in initial response could be crucial in understanding the long-term effects of COVID-19 on different individuals.
 
The Recovery Phase: A Mixed Bag
As patients moved into the recovery phase, about three months after infection, the study found a decrease in inflammatory and fibrogenic (scar-forming) proteins. Clinical symptoms also improved significantly. However, the lung proteins did not return to normal levels seen in healthy individuals. This indicates that, even as symptoms improve, the lungs continue to undergo repair.
 
One of the interesting findings during this phase was the identification of specific proteins that remained elevated even as others returned to normal levels. These proteins are involved in ongoing repair and maintenance of lung tissue, suggesting that the body continues to work on healing the lungs long after the acute phase of the disease has passed.
 
Long-Term Healing: The Convalescent Phase
Nine months after the initial infection, the study found that the lungs were still in a state of repair. Although most clinical symptoms and radiographic abnormalities (seen in chest scans) had resolved, the lung's protein profile revealed ongoing repair processes. This prolonged repair activity was unexpected and suggests that the lung con tinues to heal long after the visible signs of COVID-19 have disappeared.
 
Persistent Repair: What It Means
The prolonged lung repair processes observed in this study are significant for several reasons. Firstly, it highlights that COVID-19 can have long-lasting effects on lung health, even in cases that were not severe. Secondly, it underscores the importance of monitoring recovered patients for potential long-term lung issues. Finally, it raises questions about the possible long-term impact of COVID-19 on lung function and overall health.
 
Predicting Long-Term Lung Issues
One of the key findings of the study was the identification of a protein, secreted phosphoprotein 1 (SPP1), which could predict the development of interstitial lung disease or fibrosis (scarring) in the lungs. High levels of SPP1 in the early stages of recovery were linked to more severe lung abnormalities later on. This discovery could help doctors identify patients at risk of long-term lung issues early and take preventive measures.
 
The researchers used a sophisticated machine learning algorithm to identify SPP1 as a key predictor. By analyzing the protein levels in the BAL fluid from the acute phase, they could predict which patients were more likely to develop long-term lung problems. This approach could be a game-changer in how we monitor and treat patients recovering from COVID-19.
 
The Role of Proteins in Lung Repair
Proteins play a crucial role in the body's response to injury and infection. In the context of COVID-19, proteins involved in inflammation, tissue repair, and immune response are particularly important. The study found that these proteins remained active long after the initial infection, suggesting that the body continues to work on repairing the damage caused by the virus.
 
Among the key proteins identified were those involved in the body's immune response, such as cytokines and chemokines. These proteins help coordinate the immune system's attack on the virus and also play a role in repairing damaged tissue. The study found that levels of these proteins remained elevated for months, indicating that the immune system continues to be active even after the acute infection has resolved.
 
Implications for Other Viral Infections
While this study focused on COVID-19, the findings may have implications for other viral infections that affect the lungs. The prolonged repair processes observed in this study could be a common response to severe lung infections, indicating that the body takes much longer to fully heal than previously thought.

For example, infections like influenza or respiratory syncytial virus (RSV) might also trigger long-term repair processes similar to those seen in COVID-19. Understanding these mechanisms could help in developing better treatments for a range of respiratory illnesses.
 
Conclusion: A New Understanding of COVID-19 Recovery
This study provides valuable insights into the long-term impact of COVID-19 on the lungs. It shows that even mild to moderate cases can result in prolonged lung repair processes, highlighting the need for ongoing monitoring and care for recovered patients. The identification of predictive proteins like SPP1 also opens up new avenues for early intervention and treatment to prevent long-term lung damage.
 
The research underscores the importance of not underestimating the potential long-term effects of COVID-19, even in cases that do not require hospitalization. Regular follow-up and lung health assessments could be crucial in ensuring full recovery and preventing chronic conditions.
 
The study findings from this research were published in the peer-reviewed journal: Cell Reports Medicine.
https://www.cell.com/cell-reports-medicine/fulltext/S2666-3791(24)00356-2
 
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