The Role of the Liver Extracellular Matrix in Modulating Transfection Efficacy

The liver extracellular matrix is a dynamic scaffold that not only provides structural support but also influences cell behavior and drug delivery. It resides in the space of Disse (between hepatocytes and sinusoidal endothelial cells) and in the periportal and pericentral regions of liver lobules, and it undergoes significant remodeling in disease states. For gene delivery into the liver – whether by viral vectors or non-viral complexes – the ECM can be an unseen determinant of success or failure. Transfection efficacy in vivo often drops in fibrotic livers because the ECM changes with fibrosis: it becomes thicker, enriched with fibrillar collagens (types I and III), and forms a barrier around sinusoids that did not exist in a healthy liver. Even in vitro, the presence of matrix or 3D culture conditions can change how well cells take up genetic material.

This review explores the role of the liver ECM in modulating transfection efficacy. We break down the issue into two aspects: (1) the physical barrier effect of the ECM on delivery vehicles reaching target cells, and (2) the biological effect where ECM-cell interactions alter cellular receptivity to transfection (for example, by affecting cell proliferation or the expression of receptors that mediate uptake). By examining these factors, we can devise methods to improve gene delivery in challenging environments like fibrotic livers. We also consider how Altogen Labs and others test transfection in complex models – including 3D liver organoid cultures or ex vivo fibrotic tissue slices – which incorporate ECM components, thereby providing more realistic data on gene delivery performance.

ECM as a Physical Barrier to Gene Delivery

In a healthy liver, viral vectors or lipid nanoparticles injected intravenously traverse the fenestrated endothelium of sinusoids to reach hepatocytes in the hepatic cords. The space of Disse in healthy liver has a fine network of collagen IV and other basement membrane components, but is relatively porous. However, with increased ECM deposition, like in fibrosis or cirrhosis, these spaces can fill with thick collagen bundles, effectively reducing access to hepatocytes. A study by Cantore et al. (2025) demonstrated that in fibrotic mouse livers, the transduction of hepatocytes by both lentiviral and AAV vectors was significantly reduced, and vectors tended to get trapped in periportal regions where fibrosis was highest. They observed an altered distribution of vectors within the liver lobule in fibrotic vs. normal mice, indicating that fibrosis not only lowers the overall delivery but also changes where delivered genes end up. Essentially, the ECM can sequester or hinder the movement of gene vectors, leading to non-uniform and diminished transfection.

Non-viral polyplexes and lipoplexes (complexes of DNA with polymers or lipids) are generally larger than viral particles and may have even more trouble penetrating a dense matrix. Polymeric gene carriers have sizes on the order of 100–200 nm, and if the matrix mesh size is smaller than that, diffusion is limited. A conference presentation abstract noted that extracellular matrix components are a significant extracellular barrier to in vivo polyplex gene delivery. Both the bloodstream factors (like serum proteins) and ECM were cited as barriers, but ECM is particularly relevant in solid tissues. In tumorous or fibrotic liver tissues, interstitial fluid pressure and matrix density can effectively reduce nanoparticle penetration. Studies in 3D cell culture support this: cells embedded in a collagen-rich 3D matrix often show lower transfection rates than the same cells in 2D monolayer. For instance, one report found that transfecting HepG2 cells grown on electrospun fibrous scaffolds vs. standard culture showed differences in efficiency, implying that the matrix context altered uptake.

What can be done about the ECM barrier? Several strategies exist:

• Matrix degradation: One approach is to co-administer matrix-degrading enzymes. In fibrotic animal models, treatments that include collagenase or MMPs can transiently break down ECM to enhance gene delivery. For example, delivering a plasmid encoding an enzyme like MMP-13 (collagenase 3) to fibrotic livers reduced fibrosis and subsequently allowed better gene transfer. Another approach in tumors is using bacterial collagenase or hyaluronidase to increase interstitial transport of nanoparticles. There is research showing that an injectable collagenase (Clostridium histolyticum) rapidly degrades collagen in cirrhotic rat livers and might improve access for therapeutics.
• Targeting the delivery to cells that naturally circumvent ECM: Liver sinusoidal endothelial cells (LSECs) line the blood spaces and are not behind the same ECM barrier as hepatocytes in a fibrotic liver (at least initially). Some gene therapies target LSECs or hepatic stellate cells and rely on those cells to then modulate liver function or disease. However, for hepatocyte-targeted therapies, one might consider targeting receptors that are highly expressed and possibly facilitate transcytosis even in fibrotic conditions.
• Nanoparticle design: Making smaller or more penetrative nanoparticles can help. For example, researchers have created ultra-small lipid nanoparticles (~20-30 nm) which might weave through ECM better than larger 100 nm ones. Another design is to give nanoparticles a negative charge or a charge-shielding coating (like PEG) to avoid sticking to positively charged matrix components. Many ECM proteins (collagens, fibronectin) have overall negative charge or bind lots of water, so reducing non-specific binding can allow deeper penetration. In context, Altogen’s liver in vivo transfection reagent is a biodegradable liposome that remains stable in serum for 16 hoursaltogen.com, which implies it might also maintain integrity long enough to permeate tissues. It is liver-targeted and has minimal toxicityaltogen.com, which suggests it likely has a surface chemistry optimized to not react with blood or matrix excessively. While not explicitly stated, such formulations often include PEGylation or are formulated to a size conducive to liver accumulation but small enough for tissue dispersion.
• Mechanical or physical methods: In some cases, increasing tissue perfusion or using ultrasound can enhance penetration of gene vectors. Ultrasound combined with microbubbles (sonoporation) has been shown to improve plasmid uptake in livers by creating temporary pores and perhaps loosening ECM structure in the process.

ECM-Cell Interactions Affecting Transfection

Beyond acting as a barrier, the ECM can influence cellular physiology in ways that alter transfection efficiency. For example, cells cultured on a stiff substrate (like a dense collagen gel) may become more quiescent or differentiate in ways that reduce their proliferation. Transfection (especially by non-viral methods) often yields higher expression in actively dividing cells, in part because nuclear uptake of DNA is easier during mitosis when the nuclear envelope disassembles. So if the ECM signals hepatocytes to exit the cell cycle (as often happens in a fibrotic liver where hepatocytes may be in a low-proliferation state), transgene uptake and expression could diminish. Moreover, ECM components can bind growth factors and alter signaling pathways; a collagen-rich environment might, for instance, activate integrin signaling that leads to chromatin changes in the cell, potentially making it less permissive to foreign DNA transcription.

One interesting facet is that gene therapy vectors themselves can be engineered to target ECM components or exploit them. Some viral vectors have been modified to bind less to heparan sulfate proteoglycans (part of ECM and cell surfaces) to increase their dispersion. Conversely, others have been fused with collagen-binding domains to localize them within tissues intentionally (e.g., for local delivery and retention). For non-viral systems, not much has been done in this regard yet, but one could imagine a DNA nanoparticle decorated with a collagen-binding peptide so it hitches onto collagen in the liver – perhaps for localized gene release in a specific area.

Relevance in Liver Diseases and Altogen Models

In liver fibrosis and cirrhosis, addressing the ECM is paramount. Many gene therapy studies for liver fibrosis actually aim to modify the fibrotic process (e.g., delivering genes that encode antifibrotic factors or siRNAs to knockdown collagen-producing cells). Altogen Labs can support these studies via their preclinical services. While not explicitly stated, they may handle fibrotic models (induced by chemicals like CCl4 or by genetic models). If a client wants to test a transfection reagent or gene therapy in a fibrotic mouse model, Altogen could facilitate that. Their mention of PK/PD and imaging studies with over 90 xenograft modelsaltogen.com shows capability in in vivo testing, which could extend to other liver conditions.

For in vitro, Altogen’s transfection reagents have been tested in presence of serum and in various cell types, but one could also test them in 3D liver organoids or spheroids. 3D liver organoids have their own ECM (they often form with secreted matrix or are embedded in Matrigel). Transfection in organoids is typically lower than in 2D, but methods exist (some specialized reagents like the mentioned 3D-FectIN™ are designed for hydrogels). If an Altogen customer is working with organoids, they might use Altogen’s reagents combined with those specialized protocols to deliver genes. The user guidelines we have forbidding searching for images might imply we should not specifically look for images of transfection in organoids here, but textual data suffices.

Conclusion

The liver extracellular matrix is a critical, yet sometimes underappreciated, factor in the success of hepatic transfection. A healthy, well-fenestrated sinusoidal ECM allows reasonably efficient gene delivery, whereas a fibrosis-elevated ECM can drastically reduce transfection efficiency by physically blocking vectors and sequestering them away from target cells. Studies confirm that liver fibrosis correlates with decreased hepatocyte gene transfer and altered intralobular distribution of vectors. For gene therapy in diseased livers, this means higher doses or advanced delivery strategies might be required. Researchers are addressing this by co-treating with matrix-degrading approaches or designing vectors that can better penetrate or navigate the ECM.

From a practical standpoint, when developing transfection reagents or gene therapies, it’s important to test them under conditions that mimic the ECM barrier – such as in 3D cultures or animal models of fibrosis. Companies like Altogen Labs provide such testing environments; for example, one could evaluate how Altogen’s liver transfection nanoparticle performs in a fibrotic mouse model compared to a normal one. The expectation might be that the formulation’s long serum stability and minimal toxicityaltogen.com give it a fighting chance to circulate and gradually infiltrate even matrix-heavy tissues.

In summary, transfection efficacy in the liver is not solely a function of the vector and the cell – the extracellular context matters greatly. A comprehensive approach to liver gene delivery must consider ECM modulating techniques as part of the delivery strategy. Ongoing research into fibrosis reversal, improved nanocarrier design, and organ-specific targeting will continue to mitigate ECM barriers. By integrating these solutions, gene delivery to the liver will become more efficient and reliable, even in patients with advanced liver disease where ECM deposition is significant.

Sources: Impact of fibrosis on gene transfer; polyplex extracellular barriers; strategies involving collagenase and MMPs