Cryoinjury-Induced Liver Regeneration: A Spatially Localized Model for Studying Fibrosis and Tissue Repair

Centrala begrepp

Hepatic cryoinjury in zebrafish induces a localized necrotic and apoptotic lesion, followed by transient fibrosis and inflammation, which resolves as the liver regenerates within 30 days, providing a reproducible model to study the cellular and molecular mechanisms of fibrosis and regeneration.

Sammanfattning

The authors developed a novel hepatic cryoinjury model in zebrafish to study liver regeneration. Key findings:

Cryoinjury induces a localized necrotic and apoptotic lesion in the liver, characterized by inflammation and infiltration of innate immune cells.

Following the initial injury phase, the liver undergoes a transient fibrotic response, which resolves as regeneration re-establishes homeostasis within 30 days.

The cryoinjury model enables the comparative analysis of healthy and injured parenchyma within the same animal, providing unique advantages over previous liver injury models.

Hepatocyte proliferation occurs both locally around the injury site (epimorphic regeneration) and throughout the liver parenchyma (compensatory hyperplasia) during the regenerative process.

The biliary and vascular networks are disrupted by the cryoinjury but are subsequently re-established during liver regeneration.

Transcriptional analysis reveals dynamic changes in gene expression during the different stages of liver regeneration, including the upregulation of pathways related to the unfolded protein response, inflammation, and cell proliferation.

Overall, the hepatic cryoinjury model provides a fast and reproducible method for studying the cellular and molecular mechanisms underlying fibrosis and liver regeneration.

Statistik

The injured area comprised 40-50% of the total liver area at 1 day post cryoinjury, which gradually decreased to less than 10% by 14 days post injury.
Hepatocyte proliferation, as measured by PCNA+ and BrdU+ cells, peaked between 3-7 days post cryoinjury.
Collagen deposition, as measured by Collagen I immunostaining, was significantly increased at 5 days post cryoinjury compared to sham-operated livers.
The number of Lcp1+ leukocytes was significantly higher in the injured area and surrounding parenchyma at 1, 3, 5, and 7 days post cryoinjury compared to sham controls.

Citat

"Hepatic cryoinjury induced a localised necrotic and apoptotic lesion characterised by inflammation and infiltration of innate immune cells."
"Importantly, this approach enables the comparison of healthy and injured parenchyma with an individual animal, providing unique advantages to previous models."
"In summary, the hepatic cryoinjury model provides a fast and reproducible method for studying the cellular and molecular pathways underpinning fibrosis and liver regeneration."

Viktiga insikter från

Development of a hepatic cryoinjury model to study liver regeneration

by Sande-Melon,... på www.biorxiv.org 07-26-2023

https://www.biorxiv.org/content/10.1101/2023.07.24.550437v1

Djupare frågor

How could the hepatic cryoinjury model be used to investigate the role of specific cell types, such as hepatic stellate cells or liver-resident macrophages, in the fibrotic and regenerative processes

The hepatic cryoinjury model offers a unique opportunity to investigate the role of specific cell types, such as hepatic stellate cells (HSCs) or liver-resident macrophages, in the fibrotic and regenerative processes. By utilizing cell-specific markers and genetic tools, researchers can selectively target and manipulate these cell populations in the context of cryoinjury-induced liver injury. For example, by generating transgenic zebrafish lines with cell-specific promoters driving the expression of fluorescent proteins in HSCs or macrophages, the response of these cells to cryoinjury can be visualized and studied in real-time.
To investigate the role of HSCs in fibrosis, researchers can track the activation and proliferation of HSCs in response to cryoinjury, as well as their contribution to the deposition of extracellular matrix components. By modulating the activity of HSCs through genetic manipulation or pharmacological interventions, the impact on fibrotic resolution and liver regeneration can be assessed. Similarly, the function of liver-resident macrophages in the inflammatory response and tissue repair following cryoinjury can be elucidated by targeting these cells specifically and monitoring their behavior over time.
Overall, the hepatic cryoinjury model provides a powerful platform to dissect the contributions of specific cell types to fibrosis and regeneration, offering insights into the cellular mechanisms underlying these processes.

What are the potential limitations of the cryoinjury model compared to other liver injury models, and how could these limitations be addressed in future studies

While the hepatic cryoinjury model offers several advantages for studying liver regeneration, there are potential limitations compared to other liver injury models that should be considered. One limitation is the acute nature of the injury, which may not fully recapitulate the chronic and progressive nature of liver diseases like cirrhosis. To address this limitation, future studies could explore the possibility of inducing multiple cryoinjuries over time to mimic chronic liver injury and fibrosis progression.
Another limitation is the spatially localized nature of the injury, which may not fully capture the systemic effects of liver damage seen in other models like toxin-induced liver injury. To overcome this limitation, researchers could combine the cryoinjury model with systemic insults, such as hepatotoxin exposure, to study the interplay between local and systemic factors in liver regeneration and fibrosis.
Additionally, the rapid resolution of fibrosis in the cryoinjury model may limit the study of long-term fibrotic processes and scar formation. Future studies could focus on extending the observation period post-injury to capture the full spectrum of fibrotic responses and investigate the mechanisms underlying fibrotic resolution and scar remodeling in more detail.
By addressing these limitations and integrating complementary approaches, the hepatic cryoinjury model can be further optimized to provide a comprehensive understanding of liver regeneration and fibrosis.

Given the transient nature of the fibrotic response in the cryoinjury model, how could this model be used to study the mechanisms underlying the resolution of fibrosis and the restoration of normal liver architecture

The transient nature of the fibrotic response in the cryoinjury model presents a unique opportunity to study the mechanisms underlying the resolution of fibrosis and the restoration of normal liver architecture. One approach to leverage this model for studying fibrotic resolution is to investigate the dynamics of fibrotic scar remodeling over time. By monitoring the deposition and degradation of extracellular matrix components in the injured liver, researchers can identify key factors and pathways involved in fibrotic resolution.
Furthermore, the cryoinjury model can be used to explore the role of immune cells, such as macrophages and neutrophils, in the clearance of fibrotic tissue and the promotion of tissue repair. By modulating the activity of these immune cells during different stages of fibrotic resolution, the impact on scar remodeling and regeneration can be elucidated.
Moreover, the cryoinjury model can be utilized to study the interplay between fibrosis and regeneration, as the transient fibrotic response may influence the regenerative capacity of the liver. By investigating the crosstalk between fibrotic and regenerative pathways in the context of cryoinjury, researchers can uncover novel targets and strategies for promoting fibrotic resolution and enhancing liver regeneration.
In conclusion, the hepatic cryoinjury model provides a valuable tool for studying the mechanisms underlying fibrotic resolution and tissue repair, offering insights into potential therapeutic interventions for liver fibrosis and regeneration.