Drug targeting to myofibroblasts: Implications for fibrosis and cancer

A review on dendrimer-based nanoconjugates and their intracellular trafficking in cancer photodynamic therapy

Nanotechnology-based cancer treatment has received considerable attention, and these treatments generally use drug-loaded nanoparticles (NPs) to target and destroy cancer cells. Nanotechnology combined with photodynamic therapy (PDT) has demonstrated positive outcomes in cancer therapy. Combining nanotechnology and PDT is effective in targeting metastatic cancer cells. Nanotechnology can also increase the effectiveness of PDT by targeting cells at a molecular level. Dendrimer-based nanoconjugates (DBNs) are highly stable and biocompatible, making them suitable for drug delivery applications. Moreover, the hyperbranched structures in DBNs have the capacity to load hydrophobic compounds, such as photosensitizers (PSs) and chemotherapy drugs, and deliver them efficiently to tumour cells. This review primarily focuses on DBNs and their potential applications in cancer treatment. We discuss the chemical design, mechanism of action, and targeting efficiency of DBNs in tumour metastasis, intracellular trafficking in cancer treatment, and DBNs' biocompatibility, biodegradability and clearance properties. Overall, this study will provide the most recent insights into the application of DBNs and PDT in cancer therapy.

Andrographolide: A promising therapeutic agent against organ fibrosis

Fibrosis is the terminal pathology of chronic illness in many organs, marked by excessive accumulation of extracellular matrix proteins. These changes influence organ function, ultimately resulting in organ failure. Although significant progress has been achieved in comprehending the molecular pathways responsible for fibrosis in the last decades, effective and approved clinical therapies for the condition are still lacking. Andrographolide is a diterpenoid isolated and purified mainly from the aboveground parts of the Andrographis paniculata plant, which possesses good effects of purging heat, detoxifying, antibacterial and anti-inflammatory. In-depth research has gradually confirmed the anticancer, antioxidant, antiviral and other effects of Andro so that it can play a preventive and therapeutic role in various diseases. Over the past few years, an increasing number of research findings have indicated that Andro exerts antifibrotic effects in various organs by acting on transforming growth factor-β/small mother against decapentaplegic protein, mitogen-activated protein kinases, nuclear factor-E2-related factor 2, nuclear factor kappa-B and other signalling molecules to inhibit inflammation, oxidative stress, epithelial-mesenchymal transition, fibroblast activation and collagen buildup. This review presents a compilation of findings regarding the antifibrotic impact of Andro in tissue and cell models in vitro and in vivo. Emphasis is placed on the potential therapeutic benefits of Andro in diseases related to organ fibrosis. Existing studies and cutting-edge technologies on Andro pharmacokinetics, toxicity and bioavailability are briefly discussed to provide evidence for accelerating its clinical conversion and adoption.

Multi-omic analysis identifies the molecular mechanism of hepatocellular carcinoma with cirrhosis

Hepatocellular carcinoma with cirrhosis promotes the advancement of malignancy and the development of fibrosis in normal liver tissues. Understanding the pathological mechanisms underlying the development of HCC with cirrhosis is important for developing effective therapeutic strategies. Herein, the RNA-sequencing (RNA-seq) data and corresponding clinical features of patients with HCC were extracted from The Cancer Genome Atlas (TCGA) database using the University of California Santa Cruz (UCSC) Xena platform. The enrichment degree of hallmarkers for each TCGA-LIHC cohort was quantified by ssGSEA algorithm. Weighted gene co-expression network analysis (WGCNA) revealed two gene module eigengenes (MEs) associated with cirrhosis, namely, MEbrown and MEgreen. Analysis of these modules using AUCell showed that MEbrown had higher enrichment scores in all immune cells, whereas MEgreen had higher enrichment scores in malignant cells. The CellChat package revealed that both immune and malignant cells contributed to the fibrotic activity of myofibroblasts through diverse signaling pathways. Additionally, spatial transcriptomic data showed that hepatocytes, proliferating hepatocytes, macrophages, and myofibroblasts were located in closer proximity in HCC tissues. These cells may potentially participate in the process of stimulating myofibroblast fibrotic activity, which may be related to the development of liver fibrosis. In summary, we made full use of multi-omics data to explore gene networks and cell types that may be involved in the development and progression of cirrhosis in HCC.

Advances in macrophage-myofibroblast transformation in fibrotic diseases

Macrophage-myofibroblast transformation (MMT) has emerged as a discovery in the field of fibrotic disease research. MMT is the process by which macrophages differentiate into myofibroblasts, leading to organ fibrosis following organ damage and playing an important role in fibrosis formation and progression. Recently, many new advances have been made in studying the mechanisms of MMT occurrence in fibrotic diseases. This article reviews some critical recent findings on MMT, including the origin of MMT in myofibroblasts, the specific mechanisms by which MMT develops, and the mechanisms and effects of MMT in the kidneys, lungs, heart, retina, and other fibrosis. By summarizing the latest research related to MMT, this paper provides a theoretical basis for elucidating the mechanisms of fibrosis in various organs and developing effective therapeutic targets for fibrotic diseases.

Preclinical targeting of liver fibrosis with a 89Zr-labeled Fibrobody® directed against platelet derived growth factor receptor-β

PURPOSE

Hepatic fibrosis develops as a response to chronic liver injury, resulting in the formation of fibrous scars. This process is initiated and driven by collagen-producing activated myofibroblasts which reportedly express high levels of platelet derived growth factor receptor-β (PDGFRβ). We therefore regard PDGFRβ as an anchor for diagnosis and therapy. The Fibrobody® SP02SP26-ABD is a biparatopic VHH-construct targeting PDGFRβ. Here, we explore its potential as a theranostic vector for liver fibrosis.

METHODS

Specificity, cross-species binding, and cellular uptake of SP02SP26-ABD was assessed using human, mouse and rat PDGFRβ ectodomains and PDGFRβ-expressing cells. Cellular uptake by PDGFRβ-expressing cells was also evaluated by equipping the Fibrobody® with auristatinF and reading out in vitro cytotoxicity. The validity of PDGFRβ as a marker for active fibrosis was confirmed in human liver samples and 3 mouse models of liver fibrosis (DDC, CCl4, CDA-HFD) through immunohistochemistry and RT-PCR. After radiolabeling of DFO*-SP02SP26-ABD with 89Zr, its in vivo targeting ability was assessed in healthy mice and mice with liver fibrosis by PET-CT imaging, ex vivo biodistribution and autoradiography.

RESULTS

SP02SP26-ABD shows similar nanomolar affinity for human, mouse and rat PDGFRβ. Cellular uptake and hence subnanomolar cytotoxic potency of auristatinF-conjugated SP02SP26-ABD was observed in PDGFRβ-expressing cell lines. Immunohistochemistry of mouse and human fibrotic livers confirmed co-localization of PDGFRβ with markers of active fibrosis. In all three liver fibrosis models, PET-CT imaging and biodistribution analysis of [89Zr]Zr-SP02SP26-ABD revealed increased PDGFRβ-specific uptake in fibrotic livers. In the DDC model, liver uptake was 12.15 ± 0.45, 15.07 ± 0.90, 20.23 ± 1.34, and 20.93 ± 4.35%ID/g after 1,2,3 and 4 weeks of fibrogenesis, respectively, compared to 7.56 ± 0.85%ID/g in healthy mice. Autoradiography revealed preferential uptake in the fibrotic (PDGFRβ-expressing) periportal areas.

CONCLUSION

The anti-PDGFRβ Fibrobody® SP02SP26-ABD shows selective and high-degree targeting of activated myofibroblasts in liver fibrosis, and qualifies as a vector for diagnostic and therapeutic purposes.

Desmoplakin mutations in cardiac fibroblasts cause TGFβ1-mediated pathological fibrogenesis in desmoplakin cardiomyopathy via beclin-1 regulation

Background

Pathological fibrosis is a major finding in cardiovascular diseases and can result in arrhythmia and heart failure. Desmosome gene mutations can lead to arrhythmogenic cardiomyopathy (ACM). Among ACM, pathogenic desmoplakin ( DSP ) variants cause a distinctive cardiomyopathy with excessive cardiac fibrosis that could precede ventricular dysfunction. DSP variants are also linked to other fibrotic diseases. Whether DSP plays any role in pathological fibrosis remain unknown.

Methods

Mesenchymal stromal cells (MSCs) are resident fibroblast-like cells that are responsible for fibrogenesis in most organs, including hearts. We first used unbiased genome-wide analyses to generate cardiac fibroblasts-like, induced pluripotent stem cell-derived MSCs from normal donors and ACM patients with DSP mutations. We then studied the fibrogenic responses of cardiac MSCs to transforming growth factor beta-1 (TGF-β1) using Western/Co-IP, autophagy assay, gene knockdowns/over-expressions, genomic analyses, mouse DSP knockdown models, immunostaining, and qPCR.

Results

TGFβ1 induced excessive accumulations of vimentin (VIM)/fibrillar collagens, and over-activated fibrotic genes in DSP- mutant MSCs when compared to normal MSCs. In normal MSCs, VIMs bind to wild-type DSP during normal fibrogenesis after TGFβ1. DSP- mutant MSCs exhibited a haplo-insufficient phenotype with increased DSP-unbound VIMs that sequestered beclin-1 (BECN1) from activating autophagy and caveolin-1 (CAV1)-mediated endocytosis. Decreased autophagy caused collagen accumulations and diminished CAV1 endocytosis resulted in abnormal CAV1 plaque formation that over-activated fibrotic genes [ COL1A1, COL3A1, and fibronectin ( FN )] via heightened p38 activities after TGFβ1. Genome-wide analysis and DSP knockdown in mouse fibroblasts confirmed this novel role of DSP mutations in pathological fibrosis. Overexpression of VIM-binding domains of DSP could suppress pathological fibrosis by increasing collagen autophagic degradation and decreasing fibrotic gene expressions.

Conclusions

Our data reveal that DSP deficiency in MSCs/fibroblasts leads to exaggerated fibrogenesis in DSP-cardiomyopathy by decreasing BECN1 availability for autophagy and CAV1-endocytosis. Overexpression of VIM binding domains of DSP could be a new strategy to treat pathological fibrosis.

Engineered SPIONs functionalized with endothelin a receptor antagonist ameliorate liver fibrosis by inhibiting hepatic stellate cell activation

Endothelin-1/endothelin A receptor (ET-1/ETAR) pathway plays an important role in the progression of liver fibrosis by activating hepatic stellate cells (HSCs) - a key cell type involved in the pathogenesis of liver fibrosis. Inactivating HSCs by blocking the ET-1/ETAR pathway using a selective ETAR antagonist (ERA) represents a promising therapeutic approach for liver fibrosis. Unfortunately, small-molecule ERAs possess limited clinical potential due to poor bioavailability, short half-life, and rapid renal clearance. To improve the clinical applicability, we conjugated ERA to superparamagnetic iron-oxide nanoparticles (SPIONs) and investigated the therapeutic efficacy of ERA and ERA-SPIONs in vitro and in vivo and analyzed liver uptake by in vivo and ex vivo magnetic resonance imaging (MRI), HSCs-specific localization, and ET-1/ETAR-pathway antagonism in vivo. In murine and human liver fibrosis/cirrhosis, we observed overexpression of ET-1 and ETAR that correlated with HSC activation, and HSC-specific localization of ETAR. ERA and successfully synthesized ERA-SPIONs demonstrated significant attenuation in TGFβ-induced HSC activation, ECM production, migration, and contractility. In an acute CCl4-induced liver fibrosis mouse model, ERA-SPIONs exhibited higher liver uptake, HSC-specific localization, and ET-1/ETAR pathway antagonism. This resulted in significantly reduced liver-to-body weight ratio, plasma ALT levels, and α-SMA and collagen-I expression, indicating attenuation of liver fibrosis. In conclusion, our study demonstrates that the delivery of ERA using SPIONs enhances the therapeutic efficacy of ERA in vivo. This approach holds promise as a theranostic strategy for the MRI-based diagnosis and treatment of liver fibrosis.

BRD4: an effective target for organ fibrosis

Fibrosis is an excessive wound-healing response induced by repeated or chronic external stimuli to tissues, significantly impacting quality of life and primarily contributing to organ failure. Organ fibrosis is reported to cause 45% of all-cause mortality worldwide. Despite extensive efforts to develop new antifibrotic drugs, drug discovery has not kept pace with the clinical demand. Currently, only pirfenidone and nintedanib are approved by the FDA to treat pulmonary fibrotic illness, whereas there are currently no available antifibrotic drugs for hepatic, cardiac or renal fibrosis. The development of fibrosis is closely related to epigenetic alterations. The field of epigenetics primarily studies biological processes, including chromatin modifications, epigenetic readers, DNA transcription and RNA translation. The bromodomain and extra-terminal structural domain (BET) family, a class of epigenetic readers, specifically recognizes acetylated histone lysine residues and promotes the formation of transcriptional complexes. Bromodomain-containing protein 4 (BRD4) is one of the most well-researched proteins in the BET family. BRD4 is implicated in the expression of genes related to inflammation and pro-fibrosis during fibrosis. Inhibition of BRD4 has shown promising anti-fibrotic effects in preclinical studies; however, no BRD4 inhibitor has been approved for clinical use. This review introduces the structure and function of BET proteins, the research progress on BRD4 in organ fibrosis, and the inhibitors of BRD4 utilized in fibrosis. We emphasize the feasibility of targeting BRD4 as an anti-fibrotic strategy and discuss the therapeutic potential and challenges associated with BRD4 inhibitors in treating fibrotic diseases.

GJA4 expressed on cancer associated fibroblasts (CAFs)-A 'promoter' of the mesenchymal phenotype

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer worldwide. Connexin is a transmembrane protein involved in gap junctions (GJs) formation. Our previous study found that connexin 37 (Cx37), encoded by gap junction protein alpha 4 (GJA4), expressed on fibroblasts acts as a promoter of CRC and is closely related to epithelial-mesenchymal transition (EMT) and tumor immune microenvironment. However, to date, the mechanism concerning the malignancy of GJA4 in tumor stroma has not been studied.

METHODS

Hematoxylin-eosin (HE) and immunohistochemical (IHC) staining were used to validate the expression and localization of GJA4. Using single-cell analysis, enrichment analysis, spatial transcriptomics, immunofluorescence staining (IF), Sirius red staining, wound healing and transwell assays, western blotting (WB), Cell Counting Kit-8 (CCK8) assay and in vivo experiments, we investigated the possible mechanisms of GJA4 in promoting CRC.

RESULTS

We discovered that in CRC, GJA4 on fibroblasts is involved in promoting fibroblast activation and promoting EMT through a fibroblast-dependent pathway. Furthermore, GJA4 may act synergistically with M2 macrophages to limit T cell infiltration by stimulating the formation of an immune-excluded desmoplasic barrier. Finally, we found a significantly correlation between GJA4 and pathological staging (P < 0.0001) or D2 dimer (R = 0.03, P < 0.05).

CONCLUSION

We have identified GJA4 expressed on fibroblasts is actually a promoter of the tumor mesenchymal phenotype. Our findings suggest that the interaction between GJA4+ fibroblasts and M2 macrophages may be an effective target for enhancing tumor immunotherapy.

Polymeric nanofiber leveraged co-delivery of anti-stromal PAK1 inhibitor and paclitaxel enhances therapeutic effects in stroma-rich 3D spheroid models

The role of tumor stroma in solid tumors has been widely recognized in cancer progression, metastasis and chemoresistance. Cancer-associated fibroblasts (CAFs) play a crucial role in matrix remodeling and promoting cancer cell stemness and resistance via reciprocal crosstalk. Residual tumor tissue after surgical removal as well as unresectable tumors face therapeutic challenges to achieve curable outcome. In this study, we propose to develop a dual delivery approach by combining p21-activated kinase 1 (PAK1) inhibitor (FRAX597) to inhibit tumor stroma and chemotherapeutic agent paclitaxel (PTX) to kill cancer cells using electrospun nanofibers. First, the role of the PAK1 pathway was established in CAF differentiation, migration and contraction using relevant in vitro models. Second, polycaprolactone polymer-based nanofibers were fabricated using a uniaxial electrospinning technique to incorporate FRAX597 and/or PTX, which showed a uniform texture and a prolonged release of both drugs for 16 days. To test nanofibers, stroma-rich 3D heterospheroid models were set up which showed high resistance to PTX nanofibers compared to stroma-free homospheroids. Interestingly, nanofibers containing PTX and FRAX597 showed strong anti-tumor effects on heterospheroids by reducing the growth and viability by > 90 % compared to either of single drug-loaded nanofibers. These effects were reflected by reduced intra-spheroidal expression levels of collagen 1 and α-smooth muscle actin (α-SMA). Overall, this study provides a new therapeutic strategy to inhibit the tumor stroma using PAK1 inhibitor and thereby enhance the efficacy of chemotherapy using nanofibers as a local delivery system for unresectable or residual tumor. Use of 3D models to evaluate nanofibers highlights these models as advanced in vitro tools to study the effect of controlled release local drug delivery systems before animal studies.

Glutaminolysis regulates endometrial fibrosis in intrauterine adhesion via modulating mitochondrial function

BACKGROUND

Endometrial fibrosis, a significant characteristic of intrauterine adhesion (IUA), is caused by the excessive differentiation and activation of endometrial stromal cells (ESCs). Glutaminolysis is the metabolic process of glutamine (Gln), which has been implicated in multiple types of organ fibrosis. So far, little is known about whether glutaminolysis plays a role in endometrial fibrosis.

METHODS

The activation model of ESCs was constructed by TGF-β1, followed by RNA-sequencing analysis. Changes in glutaminase1 (GLS1) expression at RNA and protein levels in activated ESCs were verified experimentally. Human IUA samples were collected to verify GLS1 expression in endometrial fibrosis. GLS1 inhibitor and glutamine deprivation were applied to ESCs models to investigate the biological functions and mechanisms of glutaminolysis in ESCs activation. The IUA mice model was established to explore the effect of glutaminolysis inhibition on endometrial fibrosis.

RESULTS

We found that GLS1 expression was significantly increased in activated ESCs models and fibrotic endometrium. Glutaminolysis inhibition by GLS1 inhibitor bis-2-(5-phenylacetamido-1,2,4-thiadiazol-2-yl) ethyl sulfide (BPTES or glutamine deprivation treatment suppressed the expression of two fibrotic markers, α-SMA and collagen I, as well as the mitochondrial function and mTORC1 signaling in ESCs. Furthermore, inhibition of the mTORC1 signaling pathway by rapamycin suppressed ESCs activation. In IUA mice models, BPTES treatment significantly ameliorated endometrial fibrosis and improved pregnancy outcomes.

CONCLUSION

Glutaminolysis and glutaminolysis-associated mTOR signaling play a role in the activation of ESCs and the pathogenesis of endometrial fibrosis through regulating mitochondrial function. Glutaminolysis inhibition suppresses the activation of ESCs, which might be a novel therapeutic strategy for IUA.

Bruceine D suppresses CAF-promoted TNBC metastasis under TNF-α stimulation by inhibiting Notch1-Jagged1/NF-κB(p65) signaling

BACKGROUND

Triple-negative breast cancer (TNBC) has a poor prognosis because of its high degree of malignancy and the lack of effective treatment options. Cancer-associated fibroblasts (CAFs) comprise the most abundant stromal cells in the tumor microenvironment (TME), leading to functional impairments and facilitating tumor metastasis. Excessive TNF-α further promotes cross-talk between different cells in TME. Therefore, there is an urgent need to develop more effective therapies and potential drugs that target the key factors that promote TNBC metastasis.

PURPOSE

The study aimed to evaluate the efficacy of Bruceine D, an active compound derived from the Chinese herb Brucea javanica, in inhibiting metastasis and elucidate the underlying mechanism of action in TNBC.

METHODS

In vitro, the clonogenic and the Transwell assays were used to assess the effects of Bruceine D on the proliferation, migration and invasion abilities of co-cultured CAFs and MDA-MB-231 (4T1) cells under TNF-α stimulation. TNF-α, IL-6, CXCL12, TGF-β1, and MMP9 levels in the supernatant of co-cultured cells were determined using ELISA. Western blotting was utilized to detect the expression levels of proteins related to the Notch1-Jagged1/NF-κB(p65) pathway. In vivo, the anti-tumor growth and anti-metastatic effectiveness of Bruceine D was evaluated by determining tumor weight, number of metastatic lesions, and pathological changes in the tumor and lung/liver tissues. The inhibitory effect of Bruceine D on α-SMA+ CAFs activation and CAF-medicated extracellular matrix remodeling was accessed using immunohistochemistry, immunofluorescence, and Masson and Sirius Red staining. The expression levels of Notch1, Jagged1 and p-NF-κB(p65) proteins in the primary tumors were measured by immunohistochemistry and western blotting.

RESULTS

In vitro, Bruceine D significantly inhibited the migration and invasion of co-cultured CAFs and MDA-MB-231 (4T1) cells under TNF-α stimulation, reduced the expression of tumor-promoting and matrix-remodeling cytokines secreted by CAFs, and hindered the mutual activation of Notch1-Jagged1 and NF-κB(p65). In vivo, Bruceine D significantly suppressed tumor growth and the formation of lung and liver metastases by decreasing TNF-α stimulated α-SMA+ CAFs activation, collagen fibers, MMPs production, and inhibited Notch1-Jagged1/NF-κB(p65) signaling in TNBC-bearing mice.

CONCLUSION

Bruceine D effectively weakened the "tumor-CAF-inflammation" network by inhibiting the mutual activation of Notch1-Jagged1 and NF-κB(p65) and thereby suppressed TNBC metastasis. This study first explored that Bruceine D disrupted the cross-talk between CAFs and tumor cells under TNF-α stimulation to inhibit the metastasis of TNBC, and highlighted the potential of Bruceine D as therapeutic agent for suppressing tumor metastasis.

Monoclonal enolase-1 blocking antibody ameliorates pulmonary inflammation and fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic fatal disease with limited therapeutic options. The infiltration of monocytes and fibroblasts into the injured lungs is implicated in IPF. Enolase-1 (ENO1) is a cytosolic glycolytic enzyme which could translocate onto the cell surface and act as a plasminogen receptor to facilitate cell migration via plasmin activation. Our proprietary ENO1 antibody, HL217, was screened for its specific binding to ENO1 and significant inhibition of cell migration and plasmin activation (patent: US9382331B2).

METHODS

In this study, effects of HL217 were evaluated in vivo and in vitro for treating lung fibrosis.

RESULTS

Elevated ENO1 expression was found in fibrotic lungs in human and in bleomycin-treated mice. In the mouse model, HL217 reduced bleomycin-induced lung fibrosis, inflammation, body weight loss, lung weight gain, TGF-β upregulation in bronchial alveolar lavage fluid (BALF), and collagen deposition in lung. Moreover, HL217 reduced the migration of peripheral blood mononuclear cells (PBMC) and the recruitment of myeloid cells into the lungs. In vitro, HL217 significantly reduced cell-associated plasmin activation and cytokines secretion from primary human PBMC and endothelial cells. In primary human lung fibroblasts, HL217 also reduced cell migration and collagen secretion.

CONCLUSIONS

These findings suggest multi-faceted roles of cell surface ENO1 and a potential therapeutic approach for pulmonary fibrosis.

Bioinspired fine-tuning of the mechanical rigidity of SNEDDS for the efficient crossing of multiple gastrointestinal barriers

Nanoproperties, such as size, charge, and rigidity, have been demonstrated to be crucial for nanovehicles to overcome numerous gastrointestinal obstacles. However, the facile approach of modifying the rigidity of nanovehicles remains scarce, limiting understanding of how rigidity impacts their oral delivery. Inspired by the fact that cellular phospholipid content regulates plasma membrane rigidity, the rigidity of self-nanoemulsifiying drug delivery system (SNEDDS) could be fine-tuned via phosphocholine content while their size and zeta potential remain unchanged, using insulin as a model drug. Notably, soft SNEDDS exerted longer gastrointestinal transit time, higher drug release rate, stronger gastrointestinal stability and relatively lower mucus permeation but superior epithelial transcytosis than their hard counterparts in a macropinocytosis-dependent manner. The rigidity-related enhanced transcytosis was attributed to improved endocytosis, lysosome escape capability and exocytosis. Rats with type 1 diabetes exhibited greater oral insulin absorption and blood glucose lowering effect with soft SNEDDS. This study demonstrated the regulatory role of phospholipids in nanovehicle rigidity, which could help develop mechanically optimized nanomedicines in the future.

Total sesquiterpenoids from Eupatorium lindleyanum DC. attenuate bleomycin-induced lung fibrosis by suppressing myofibroblast transition

Eupatorium lindleyanum DC. has been used as a functional food in China for a long time. However, the antifibrotic activity of total sesquiterpenoids from Eupatorium lindleyanum DC. (TS-EL) is still unknown. In this study, we discovered that TS-EL reduced the increase in α-smooth muscle actin (α-SMA), type I collagen and fibronectin content, the formation of cell filaments and collagen gel contraction in transforming growth factor-β1-stimulated human lung fibroblasts. Intriguingly, TS-EL did not change the phosphorylation of Smad2/3 and Erk1/2. TS-EL decreased the levels of serum response factor (SRF), a critical transcription factor of α-SMA, and SRF knockdown alleviated the transition of lung myofibroblasts. Furthermore, TS-EL significantly attenuated bleomycin (BLM)-induced lung pathology and collagen deposition and reduced the levels of two profibrotic markers, total lung hydroxyproline and α-SMA. TS-EL also decreased the levels of SRF protein expression in BLM-induced mice. These results suggested that TS-EL attenuates pulmonary fibrosis by inhibiting myofibroblast transition via the downregulation of SRF.

Nanovesicles loaded with a TGF-β receptor 1 inhibitor overcome immune resistance to potentiate cancer immunotherapy

The immune-excluded tumors (IETs) show limited response to current immunotherapy due to intrinsic and adaptive immune resistance. In this study, it is identified that inhibition of transforming growth factor-β (TGF-β) receptor 1 can relieve tumor fibrosis, thus facilitating the recruitment of tumor-infiltrating T lymphocytes. Subsequently, a nanovesicle is constructed for tumor-specific co-delivery of a TGF-β inhibitor (LY2157299, LY) and the photosensitizer pyropheophorbide a (PPa). The LY-loaded nanovesicles suppress tumor fibrosis to promote intratumoral infiltration of T lymphocytes. Furthermore, PPa chelated with gadolinium ion is capable of fluorescence, photoacoustic and magnetic resonance triple-modal imaging-guided photodynamic therapy, to induce immunogenic death of tumor cells and elicit antitumor immunity in preclinical cancer models in female mice. These nanovesicles are further armored with a lipophilic prodrug of the bromodomain-containing protein 4 inhibitor (i.e., JQ1) to abolish programmed death ligand 1 expression of tumor cells and overcome adaptive immune resistance. This study may pave the way for nanomedicine-based immunotherapy of the IETs.

Understanding of arthrofibrosis: New explorative insights into extracellular matrix remodeling of synovial fibroblasts

Arthrofibrosis following total knee arthroplasty is a fibroproliferative joint disorder marked by dysregulated biosynthesis of extracellular matrix proteins, such as collagens and proteoglycans. The underlying cellular events remain incompletely understood. Myofibroblasts are highly contractile matrix-producing cells characterized by increased alpha-smooth muscle actin expression and xylosyltransferase-I (XT-I) secretion. Human XT-I has been identified as a key mediator of arthrofibrotic remodeling. Primary fibroblasts from patients with arthrofibrosis provide a useful in vitro model to identify and characterize disease regulators and potential therapeutic targets. This study aims at characterizing primary synovial fibroblasts from arthrofibrotic tissues (AFib) regarding their molecular and cellular phenotype by utilizing myofibroblast cell culture models. Compared to synovial control fibroblasts (CF), AFib are marked by enhanced cell contractility and a higher XT secretion rate, demonstrating an increased fibroblast-to-myofibroblast transition rate during arthrofibrosis. Histochemical assays and quantitative gene expression analysis confirmed higher collagen and proteoglycan expression and accumulation in AFib compared to CF. Furthermore, fibrosis-based gene expression profiling identified novel modifier genes in the context of arthrofibrosis remodeling. In summary, this study revealed a unique profibrotic phenotype in AFib that resembles some traits of other fibroproliferative diseases and can be used for the future development of therapeutic interventions.

Biological Hyperthermia-Inducing Nanoparticles for Specific Remodeling of the Extracellular Matrix Microenvironment Enhance Pro-Apoptotic Therapy in Fibrosis

The extracellular matrix (ECM) is a major driver of fibrotic diseases and forms a dense fibrous barrier that impedes nanodrug delivery. Because hyperthermia causes destruction of ECM components, we developed a nanoparticle preparation to induce fibrosis-specific biological hyperthermia (designated as GPQ-EL-DNP) to improve pro-apoptotic therapy against fibrotic diseases based on remodeling of the ECM microenvironment. GPQ-EL-DNP is a matrix metalloproteinase (MMP)-9-responsive peptide, (GPQ)-modified hybrid nanoparticle containing fibroblast-derived exosomes and liposomes (GPQ-EL) and is loaded with a mitochondrial uncoupling agent, 2,4-dinitrophenol (DNP). GPQ-EL-DNP can specifically accumulate and release DNP in the fibrotic focus, inducing collagen denaturation through biological hyperthermia. The preparation was able to remodel the ECM microenvironment, decrease stiffness, and suppress fibroblast activation, which further enhanced GPQ-EL-DNP delivery to fibroblasts and sensitized fibroblasts to simvastatin-induced apoptosis. Therefore, simvastatin-loaded GPQ-EL-DNP achieved an improved therapeutic effect on multiple types of murine fibrosis. Importantly, GPQ-EL-DNP did not induce systemic toxicity to the host. Therefore, the nanoparticle GPQ-EL-DNP for fibrosis-specific hyperthermia can be used as a potential strategy to enhance pro-apoptotic therapy in fibrotic diseases.

A 3D culture system for evaluating the combined effects of cisplatin and anti-fibrotic drugs on the growth and invasion of lung cancer cells co-cultured with fibroblasts

Fibrosis and fibroblast activation usually occur in the tissues surrounding a malignant tumor; therefore, anti-fibrotic drugs are used in addition to chemotherapy. A reliable technique for evaluating the combined effects of anti-fibrotic drugs and anticancer drugs would be beneficial for the development of an appropriate treatment strategy. In this study, we manufactured a three-dimensional (3D) co-culture system of fibroblasts and lung cancer cell spheroids in Matrigel supplemented with fibrin (fibrin/Matrigel) that simulated the tissue microenvironment around a solid tumor. We compared the efficacy of an anticancer drug (cisplatin) with or without pretreatments of two anti-fibrotic drugs, nintedanib and pirfenidone, on the growth and invasion of cancer cells co-cultured with fibroblasts. The results showed that the addition of nintedanib improved cisplatin's effects on suppressing the growth of cancer cell spheroids and the invasion of cancer cells. In contrast, pirfenidone did not enhance the anticancer activity of cisplatin. Nintedanib also showed higher efficacy than pirfenidone in reducing the expression of four genes in fibroblasts associated with cell adhesion, invasion, and extracellular matrix degradation. This study demonstrated that the 3D co-cultures in fibrin/Matrigel would be useful for assessing the effects of drug combinations on tumor growth and invasion.

Orally administration of cerium oxide nanozyme for computed tomography imaging and anti-inflammatory/anti-fibrotic therapy of inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD) is a chronic nonspecific disease with unknown etiology. Currently, the anti-inflammatory therapeutic approaches have achieved a certain extent of effects in terms of inflammation alleviation. Still, the final pathological outcome of intestinal fibrosis has not been effectively improved yet.

RESULTS

In this study, dextran-coated cerium oxide (D-CeO₂) nanozyme with superoxide dismutase (SOD) and catalase (CAT) activities was synthesized by chemical precipitation. Our results showed that D-CeO₂ could efficiently scavenge reactive oxide species (ROS) as well as downregulate the pro-inflammatory cytokines (IL-1β, IL-6, TNF-α, and iNOS) to protect cells from H₂O₂-induced oxidative damage. Moreover, D-CeO₂ could suppress the expression of fibrosis-related gene levels, such as α-SMA, and Collagen 1/3, demonstrating the anti-fibrotic effect. In both TBNS- and DSS-induced colitis models, oral administration of D-CeO₂ in chitosan/alginate hydrogel alleviated intestinal inflammation, reduced colonic damage by scavenging ROS, and decreased inflammatory factor levels. Notably, our findings also suggested that D-CeO₂ reduced fibrosis-related cytokine levels, predicting a contribution to alleviating colonic fibrosis. Meanwhile, D-CeO₂ could also be employed as a CT contrast agent for noninvasive gastrointestinal tract (GIT) imaging.

CONCLUSION

We introduced cerium oxide nanozyme as a novel therapeutic approach with computed tomography (CT)-guided anti-inflammatory and anti-fibrotic therapy for the management of IBD. Collectively, without appreciable systemic toxicity, D-CeO₂ held the promise of integrated applications for diagnosis and therapy, pioneering the exploration of nanozymes with ROS scavenging capacity in the anti-fibrotic treatment of IBD.

Hepatic Stellate Cell Targeting Using Peptide-Modified Biologicals

Liver diseases are a leading cause of death worldwide and are rising exponentially due to increasing prevalence of metabolic disorders. Hepatic stellate cells (HSCs) are recognized as a key therapeutic target in liver diseases as these cells, upon activation during liver damage and ongoing liver inflammation, secrete excessive amounts of extracellular matrix that leads to liver tissue scarring (fibrosis) responsible for liver dysfunction (end-stage liver disease) and desmoplasia in hepatocellular carcinoma. Targeting of HSCs to reverse fibrosis progression has been realized by several experts in the field, including us. We have developed strategies to target activated HSCs by utilizing the receptors overexpressed on the surface of activated HSCs. One well-known receptor is platelet derived growth factor receptor-beta (PDGFR-β). Using PDGFR-β recognizing peptides (cyclic PPB or bicyclic PPB), we can deliver biologicals, e.g., interferon gamma (IFNγ) or IFNγ activity domain (mimetic IFNγ), to the activated HSCs that can inhibit their activation and reverse liver fibrosis. In this chapter, we provide the detailed methods and the principles involved in the synthesis of these targeted (mimetic) IFNγ constructs. These methods can be adapted for synthesizing constructs for targeted/cell-specific delivery of peptides/proteins, drugs, and imaging agents useful for various applications including diagnosis and treatment of inflammatory and fibrotic diseases and cancer.

Myofibroblast depletion reduces kidney cyst growth and fibrosis in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) involves the development and persistent growth of fluid filled kidney cysts. In a recent study, we showed that ADPKD kidney cyst epithelial cells can stimulate the proliferation and differentiation of peri-cystic myofibroblasts. Although dense myofibroblast populations are often found surrounding kidney cysts, their role in cyst enlargement or fibrosis in ADPKD is unclear. To clarify this, we examined the effect of myofibroblast depletion in the Pkd1RC/RC (RC/RC) mouse model of ADPKD. RC/RC;αSMAtk mice that use the ganciclovir-thymidine kinase system to selectively deplete α-smooth muscle actin expressing myofibroblasts were generated. Ganciclovir treatment for four weeks depleted myofibroblasts, reduced kidney fibrosis and preserved kidney function in these mice. Importantly, myofibroblast depletion significantly reduced cyst growth and cyst epithelial cell proliferation in RC/RC;αSMAtk mouse kidneys. Similar ganciclovir treatment did not alter cyst growth or fibrosis in wild-type or RC/RC littermates. In vitro, co-culture with myofibroblasts from the kidneys of patients with ADPKD increased 3D microcyst growth of human ADPKD cyst epithelial cells. Treatment with conditioned culture media from ADPKD kidney myofibroblasts increased microcyst growth and cell proliferation of ADPKD cyst epithelial cells. Further examination of ADPKD myofibroblast conditioned media showed high levels of protease inhibitors including PAI1, TIMP1 and 2, NGAL and TFPI-2, and treatment with recombinant PAI1 and TIMP1 increased ADPKD cyst epithelial cell proliferation in vitro. Thus, our findings show that myofibroblasts directly promote cyst epithelial cell proliferation, cyst growth and fibrosis in ADPKD kidneys, and their targeting could be a novel therapeutic strategy to treat PKD.

SARS-CoV-2-mediated liver injury: pathophysiology and mechanisms of disease

BACKGROUND

SARS-CoV-2-induced severe inflammatory response can be associated with severe medical consequences leading to multi-organ failure, including the liver. The main mechanism behind this assault is the aggressive cytokine storm that induces cytotoxicity in various organs. Of interest, hepatic stellate cells (HSC) respond acutely to liver injury through several molecular mechanisms, hence furthering the perpetuation of the cytokine storm and its resultant tissue damage. In addition, hepatocytes undergo apoptosis or necrosis resulting in the release of pro-inflammatory and pro-fibrogenic mediators that lead to chronic liver inflammation.

AIMS

The aim of this review is to summarize available data on SARS-CoV-2-induced liver inflammation in addition to evaluate the potential effect of anti-inflammatory drugs in attenuating SARS-CoV-2-induced liver inflammation.

METHODS

Thorough PubMed search was done to gather and summarize published data on SARS-CoV-2-induced liver inflammation. Additionally, various anti-inflammatory potential treatments were also documented.

RESULTS

Published data documented SARS-CoV-2 infection of liver tissues and is prominent in most liver cells. Also, histological analysis showed various features of tissues damage, e.g., hepatocellular necrosis, mitosis, cellular infiltration, and fatty degeneration in addition to microvesicular steatosis and inflammation. Finally, the efficacy of the different drugs used to treat SARS-CoV-2-induced liver injury, in particular the anti-inflammatory remedies, are likely to have some beneficial effect to treat liver injury in COVID-19.

CONCLUSION

SARS-CoV-2-induced liver inflammation is a serious condition, and drugs with potent anti-inflammatory effect can play a major role in preventing irreversible liver damage in COVID-19.

Novel genetic loci associated with osteoarthritis in multi-ancestry analyses in the Million Veteran Program and UK Biobank

Osteoarthritis is a common progressive joint disease. As no effective medical interventions are available, osteoarthritis often progresses to the end stage, in which only surgical options such as total joint replacement are available. A more thorough understanding of genetic influences of osteoarthritis is essential to develop targeted personalized approaches to treatment, ideally long before the end stage is reached. To date, there have been no large multiancestry genetic studies of osteoarthritis. Here, we leveraged the unique resources of 484,374 participants in the Million Veteran Program and UK Biobank to address this gap. Analyses included participants of European, African, Asian and Hispanic descent. We discovered osteoarthritis-associated genetic variation at 10 loci and replicated findings from previous osteoarthritis studies. We also present evidence that some osteoarthritis-associated regions are robust to population ancestry. Drug repurposing analyses revealed enrichment of targets of several medication classes and provide potential insight into the etiology of beneficial effects of antiepileptics on osteoarthritis pain.

Intersection of stem cell biology and engineering towards next generation in vitro models of human fibrosis

Human fibrotic diseases constitute a major health problem worldwide. Fibrosis involves significant etiological heterogeneity and encompasses a wide spectrum of diseases affecting various organs. To date, many fibrosis targeted therapeutic agents failed due to inadequate efficacy and poor prognosis. In order to dissect disease mechanisms and develop therapeutic solutions for fibrosis patients, in vitro disease models have gone a long way in terms of platform development. The introduction of engineered organ-on-a-chip platforms has brought a revolutionary dimension to the current fibrosis studies and discovery of anti-fibrotic therapeutics. Advances in human induced pluripotent stem cells and tissue engineering technologies are enabling significant progress in this field. Some of the most recent breakthroughs and emerging challenges are discussed, with an emphasis on engineering strategies for platform design, development, and application of machine learning on these models for anti-fibrotic drug discovery. In this review, we discuss engineered designs to model fibrosis and how biosensor and machine learning technologies combine to facilitate mechanistic studies of fibrosis and pre-clinical drug testing.

Reversal of pancreatic desmoplasia by a tumour stroma-targeted nitric oxide nanogel overcomes TRAIL resistance in pancreatic tumours

OBJECTIVE

Stromal barriers, such as the abundant desmoplastic stroma that is characteristic of pancreatic ductal adenocarcinoma (PDAC), can block the delivery and decrease the tumour-penetrating ability of therapeutics such as tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), which can selectively induce cancer cell apoptosis. This study aimed to develop a TRAIL-based nanotherapy that not only eliminated the extracellular matrix barrier to increase TRAIL delivery into tumours but also blocked antiapoptotic mechanisms to overcome TRAIL resistance in PDAC.

DESIGN

Nitric oxide (NO) plays a role in preventing tissue desmoplasia and could thus be delivered to disrupt the stromal barrier and improve TRAIL delivery in PDAC. We applied an in vitro-in vivo combinatorial phage display technique to identify novel peptide ligands to target the desmoplastic stroma in both murine and human orthotopic PDAC. We then constructed a stroma-targeted nanogel modified with phage display-identified tumour stroma-targeting peptides to co-deliver NO and TRAIL to PDAC and examined the anticancer effect in three-dimensional spheroid cultures in vitro and in orthotopic PDAC models in vivo.

RESULTS

The delivery of NO to the PDAC tumour stroma resulted in reprogramming of activated pancreatic stellate cells, alleviation of tumour desmoplasia and downregulation of antiapoptotic BCL-2 protein expression, thereby facilitating tumour penetration by TRAIL and substantially enhancing the antitumour efficacy of TRAIL therapy.

CONCLUSION

The co-delivery of TRAIL and NO by a stroma-targeted nanogel that remodels the fibrotic tumour microenvironment and suppresses tumour growth has the potential to be translated into a safe and promising treatment for PDAC.

Anti-Fibrotic Effect of SDF-1β Overexpression in Bleomycin-Injured Rat Lung

Rational: Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease and is associated with high mortality due to a lack of effective treatment. Excessive deposition of the extracellular matrix by activated myofibroblasts in the alveolar space leads to scar formation that hinders gas exchange. Therefore, selectively removing activated myofibroblasts with the aim to repair and remodel fibrotic lungs is a promising approach. Stromal-derived growth factor (SDF-1) is known to stimulate cellular signals which attract stem cells to the site of injury for tissue repair and remodeling. Here, we investigate the effect of overexpression of SDF-1β on lung structure using the bleomycin-injured rat lung model. Methods: Intratracheal administration of bleomycin was performed in adult male rats (F344). Seven days later, in vivo electroporation-mediated gene transfer of either SDF-1β or the empty vector was performed. Animals were sacrificed seven days after gene transfer and histology, design-based stereology, flow cytometry, and collagen measurement were performed on the tissue collected. For in vitro experiments, lung fibroblasts obtained from IPF patients were used. Results: Seven days after SDF-1β gene transfer to bleomycin-injured rat lungs, reduced total collagen, reduced collagen fibrils, improved histology and induced apoptosis of myofibroblasts were observed. Furthermore, it was revealed that TNF-α mediates SDF-1β-induced apoptosis of myofibroblasts; moreover, SDF-1β overexpression increased alveolar epithelial cell numbers and proliferation in vivo and also induced their migration in vitro. Conclusions: Our study demonstrates a new antifibrotic mechanism of SDF-1β overexpression and suggests SDF-1β as a potential new approach for the treatment of lung fibrosis.

Transient receptor potential vanilloid subtype 1: A potential therapeutic target for fibrotic diseases

The transient receptor potential vanilloid subtype 1 (TRPV1), belonging to the TRPV channel family, is a non-selective, calcium-dependent, cation channel implicated in several pathophysiological processes. Collagen, an extracellular matrix component, can accumulate under pathological conditions and may lead to the destruction of tissue structure, organ dysfunction, and organ failure. Increasing evidence indicates that TRPV1 plays a role in the development and occurrence of fibrotic diseases, including myocardial, renal, pancreatic, and corneal fibrosis. However, the mechanism by which TRPV1 regulates fibrosis remains unclear. This review highlights the comprehensive role played by TRPV1 in regulating pro-fibrotic processes, the potential of TRPV1 as a therapeutic target in fibrotic diseases, as well as the different signaling pathways associated with TRPV1 and fibrosis.

Intratracheally administered LNA gapmer antisense oligonucleotides induce robust gene silencing in mouse lung fibroblasts

The lung is a complex organ with various cell types having distinct roles. Antisense oligonucleotides (ASOs) have been studied in the lung, but it has been challenging to determine their effectiveness in each cell type due to the lack of appropriate analytical methods. We employed three distinct approaches to study silencing efficacy within different cell types. First, we used lineage markers to identify cell types in flow cytometry, and simultaneously measured ASO-induced silencing of cell-surface proteins CD47 or CD98. Second, we applied single-cell RNA sequencing (scRNA-seq) to measure silencing efficacy in distinct cell types; to the best of our knowledge, this is the first time scRNA-seq has been applied to measure the efficacy of oligonucleotide therapeutics. In both approaches, fibroblasts were the most susceptible to locally delivered ASOs, with significant silencing also in endothelial cells. Third, we confirmed that the robust silencing in fibroblasts is broadly applicable by silencing two targets expressed mainly in fibroblasts, Mfap4 and Adam33. Across independent approaches, we demonstrate that intratracheally administered LNA gapmer ASOs robustly induce gene silencing in lung fibroblasts. ASO-induced gene silencing in fibroblasts was durable, lasting 4-8 weeks after a single dose. Thus, lung fibroblasts are well aligned with ASOs as therapeutics.

Cytotoxicity Assessment of Surface-Modified Magnesium Hydroxide Nanoparticles

Magnesium-based nanoparticles have shown promise in regenerative therapies in orthopedics and the cardiovascular system. Here, we set out to assess the influence of differently functionalized Mg nanoparticles on the cellular players of wound healing, the first step in the process of tissue regeneration. First, we thoroughly addressed the physicochemical characteristics of magnesium hydroxide nanoparticles, which exhibited low colloidal stability and strong aggregation in cell culture media. To address this matter, magnesium hydroxide nanoparticles underwent surface functionalization by 3-aminopropyltriethoxysilane (APTES), resulting in excellent dispersible properties in ethanol and improved colloidal stability in physiological media. The latter was determined as a concentration- and time-dependent phenomenon. There were no significant effects on THP-1 macrophage viability up to 1.500 μg/mL APTES-coated magnesium hydroxide nanoparticles. Accordingly, increased media pH and Mg²⁺ concentration, the nanoparticles dissociation products, had no adverse effects on their viability and morphology. HDF, ASCs, and PK84 exhibited the highest, and HUVECs, HPMECs, and THP-1 cells the lowest resistance toward nanoparticle toxic effects. In conclusion, the indicated high magnesium hydroxide nanoparticles biocompatibility suggests them a potential drug delivery vehicle for treating diseases like fibrosis or cancer. If delivered in a targeted manner, cytotoxic nanoparticles could be considered a potential localized and specific prevention strategy for treating highly prevalent diseases like fibrosis or cancer. Looking toward the possible clinical applications, accurate interpretation of in vitro cellular responses is the keystone for the relevant prediction of subsequent in vivo biological effects.

Novel Synthetic Polymer-Based 3D Contraction Assay: A Versatile Preclinical Research Platform for Fibrosis

The driving factors causing fibrosis and scar formation include fibroblast differentiation into myofibroblasts and hampered myofibroblast apoptosis, which ultimately results in collagen accumulation and tissue contraction. Currently, only very few drugs are available for fibrosis treatment, and there is an urgent demand for new pharmaceutical products. High-throughput in vitro fibrosis models are necessary to develop such drugs. In this study, we developed such a novel model based on synthetic polyisocyanide (PIC-RGD) hydrogels. The model not only measures contraction but also allows for subsequent molecular and cellular analysis. Fibroblasts were seeded in small (10 μL) PIC-RGD gels in the absence or presence of TGFβ1, the latter to induce myofibroblast differentiation. The contraction model clearly differentiates fibroblasts and myofibroblasts. Besides a stronger contraction, we also observed α-smooth muscle actin (αSMA) production and higher collagen deposition for the latter. The results were supported by mRNA expression experiments of αSMA, Col1α1, P53, and Ki67. As proof of principle, the effects of FDA-approved antifibrotic drugs nintedanib and pirfenidone were tested in our newly developed fibrosis model. Both drugs clearly reduce myofibroblast-induced contraction. Moreover, both drugs significantly decrease myofibroblast viability. Our low-volume synthetic PIC-RGD hydrogel platform is an attractive tool for high-throughput in vitro antifibrotic drug screening.

Cancer-associated fibroblasts in breast cancer: Challenges and opportunities

The tumor microenvironment is proposed to contribute substantially to the progression of cancers, including breast cancer. Cancer-associated fibroblasts (CAFs) are the most abundant components of the tumor microenvironment. Studies have revealed that CAFs in breast cancer originate from several types of cells and promote breast cancer malignancy by secreting factors, generating exosomes, releasing nutrients, reshaping the extracellular matrix, and suppressing the function of immune cells. CAFs are also becoming therapeutic targets for breast cancer due to their specific distribution in tumors and their unique biomarkers. Agents interrupting the effect of CAFs on surrounding cells have been developed and applied in clinical trials. Here, we reviewed studies examining the heterogeneity of CAFs in breast cancer and expression patterns of CAF markers in different subtypes of breast cancer. We hope that summarizing CAF-related studies from a historical perspective will help to accelerate the development of CAF-targeted therapeutic strategies for breast cancer.

Delivery of sorafenib by myofibroblast-targeted nanoparticles for the treatment of renal fibrosis

Fibrosis is an excessive accumulation of the extracellular matrix within solid organs in response to injury and a common pathway that leads functional failure. No clinically approved agent is available to reverse or even prevent this process. Herein, we report a nanotechnology-based approach that utilizes a drug carrier to deliver a therapeutic cargo specifically to fibrotic kidneys, thereby improving the antifibrotic effect of the drug and reducing systemic toxicity. We first adopted in vitro-in vivo combinatorial phage display technology to identify peptide ligands that target myofibroblasts in mouse unilateral ureteral obstruction (UUO)-induced fibrotic kidneys. We then engineered lipid-coated poly(lactic-co-glycolic acid) nanoparticles (NPs) with fibrotic kidney-homing peptides on the surface and sorafenib, a potent antineoplastic multikinase inhibitor, encapsulated in the core. Sorafenib loaded in the myofibroblast-targeted NPs significantly reduced the infiltration of α-smooth muscle actin-expressing myofibroblasts and deposition of collagen I in UUO-treated kidneys and enhanced renal plasma flow measured by Technetium-99m mercaptoacetyltriglycine scintigraphy. This study demonstrates the therapeutic potential of the newly identified peptide fragments as anchors to target myofibroblasts and represents a strategic advance for selective delivery of sorafenib to treat renal fibrosis. SIGNIFICANCE STATEMENT: Renal fibrosis is a pathological feature accounting for the majority of issues in chronic kidney disease (CKD), which may progress to end-stage renal disease (ESRD). This manuscript describes a myofibroblast-targeting drug delivery system modified with phage-displayed fibrotic kidney-homing peptides. By loading the myofibroblast-targeting nanoparticles (NPs) with sorafenib, a multikinase inhibitor, the NPs could suppress collagen synthesis in cultured human myofibroblasts. When given intravenously to mice with UUO-induced renal fibrosis, sorafenib loaded in myofibroblast-targeting NPs significantly ameliorated renal fibrosis. This approach provides an efficient therapeutic option to renal fibrosis. The myofibroblast-targeting peptide ligands and nanoscale drug carriers may be translated into clinical application in the future.

Antibody-drug conjugates targeting CD248 inhibits liver fibrosis through specific killing on myofibroblasts

Background

Chronic liver injury induces pathological repair, resulting in fibrosis, during which hepatic stellate cells (HSCs) are activated and transform into myofibroblasts. CD248 is mainly expressed on myofibroblasts and was considered as a promising target to treat fibrosis. The primary aim of this study was to generate a CD248 specific antibody-drug conjugate (ADC) and evaluate its therapeutic efficacy for liver fibrosis and its safety in vivo.

Methods

CD248 expression was examined in patients with liver cirrhosis and in mice with CCl₄-induced liver fibrosis. The ADC IgG78-DM1, which targets CD248, was prepared and its bioactivity on activated primary HSCs was studied. The anti-fibrotic effects of IgG78-DM1 on liver fibrosis were evaluated in CCl₄-induced mice. The reproductive safety and biosafety of IgG78-DM1 were also evaluated in vivo.

Results

CD248 expression was upregulated in patients with liver cirrhosis and in CCl₄-induced mice, and was mainly expressed on alpha smooth muscle actin (α-SMA)⁺ myofibroblasts. IgG78-DM1 was successfully generated, which could effectively bind with and kill CD248⁺ activated HSCs in vitro and inhibit liver fibrosis in vivo. In addition, IgG78-DM1 was demonstrated to have qualified biosafety and reproductive safety in vivo.

Conclusions

Our study demonstrated that CD248 could be an ideal target for myofibroblasts in liver fibrosis, and CD248-targeting IgG78-DM1 had excellent anti-fibrotic effects in mice with liver fibrosis. Our study provided a novel strategy to treat liver fibrosis and expanded the application of ADCs beyond tumors.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00460-1.

A Klotho-derived peptide protects against kidney fibrosis by targeting TGF-β signaling

Loss of Klotho, an anti-aging protein, plays a critical role in the pathogenesis of chronic kidney diseases. As Klotho is a large transmembrane protein, it is challenging to harness it as a therapeutic remedy. Here we report the discovery of a Klotho-derived peptide 1 (KP1) protecting kidneys by targeting TGF-β signaling. By screening a series of peptides derived from human Klotho protein, we identified KP1 that repressed fibroblast activation by binding to TGF-β receptor 2 (TβR2) and disrupting the TGF-β/TβR2 engagement. As such, KP1 blocked TGF-β-induced activation of Smad2/3 and mitogen-activated protein kinases. In mouse models of renal fibrosis, intravenous injection of KP1 resulted in its preferential accumulation in injured kidneys. KP1 preserved kidney function, repressed TGF-β signaling, ameliorated renal fibrosis and restored endogenous Klotho expression. Together, our findings suggest that KP1 recapitulates the anti-fibrotic action of Klotho and offers a potential remedy in the fight against fibrotic kidney diseases.

Studying Activated Fibroblast Phenotypes and Fibrosis-Linked Mechanosensing Using 3D Biomimetic Models

Fibrosis and solid tumor progression are closely related, with both involving pathways associated with chronic wound dysregulation. Fibroblasts contribute to extracellular matrix (ECM) remodeling in these processes, a crucial step in scarring, organ failure, and tumor growth, but little is known about the biophysical evolution of remodeling regulation during the development and progression of matrix-related diseases including fibrosis and cancer. A 3D collagen-based scaffold model is employed here to mimic mechanical changes in normal (2 kPa, soft) versus advanced pathological (12 kPa, stiff) tissues. Activated fibroblasts grown on stiff scaffolds show lower migration and increased cell circularity compared to those on soft scaffolds. This is reflected in gene expression profiles, with cells cultured on stiff scaffolds showing upregulated DNA replication, DNA repair, and chromosome organization gene clusters, and a concomitant loss of ability to remodel and deposit ECM. Soft scaffolds can reproduce biophysically meaningful microenvironments to investigate early stage processes in wound healing and tumor niche formation, while stiff scaffolds can mimic advanced fibrotic and cancer stages. These results establish the need for tunable, affordable 3D scaffolds as platforms for aberrant stroma research and reveal the contribution of physiological and pathological microenvironment biomechanics to gene expression changes in the stromal compartment.

Remodelling of the fibre-aggregate structure of collagen gels by cancer-associated fibroblasts: A time-resolved grey-tone image analysis based on stochastic modelling

Introduction

Solid tumors consist of tumor cells associated with stromal and immune cells, secreted factors and extracellular matrix (ECM), which together constitute the tumor microenvironment. Among stromal cells, activated fibroblasts, known as cancer-associated fibroblasts (CAFs) are of particular interest. CAFs secrete a plethora of ECM components including collagen and modulate the architecture of the ECM, thereby influencing cancer cell migration. The characterization of the collagen fibre network and its space and time-dependent microstructural modifications is key to investigating the interactions between cells and the ECM. Developing image analysis tools for that purpose is still a challenge because the structural complexity of the collagen network calls for specific statistical descriptors. Moreover, the low signal-to-noise ratio of imaging techniques available for time-resolved studies rules out standard methods based on image segmentation.

Methods

In this work, we develop a novel approach based on the stochastic modelling of the gel structure and on grey-tone image analysis. The method is then used to study the remodelling of a collagen matrix by migrating breast cancer-derived CAFs in a three-dimensional spheroid model of cellular invasion imaged by time-lapse confocal microscopy.

Results

The structure of the collagen at the scale of a few microns consists in regions with high fibre density separated by depleted regions, which can be thought of as aggregates and pores. The approach developped captures this two-scale structure with a clipped Gaussian field model to describe the aggregates-and-pores large-scale structure, and a homogeneous Boolean model to describe the small-scale fibre network within the aggregates. The model parameters are identified by fitting the grey-tone histograms and correlation functions of the images. The method applies to unprocessed grey-tone images, and it can therefore be used with low magnification, noisy time-lapse reflectance images. When applied to the CAF spheroid time-resolved images, the method reveals different matrix densification mechanisms for the matrix in direct contact or far from the cells.

Conclusion

We developed a novel and multidisciplinary image analysis approach to investigate the remodelling of fibrillar collagen in a 3D spheroid model of cellular invasion. The specificity of the method is that it applies to the unprocessed grey-tone images, and it can therefore be used with noisy time-lapse reflectance images of non-fluorescent collagen. When applied to the CAF spheroid time-resolved images, the method reveals different matrix densification mechanisms for the matrix in direct contact or far from the cells.

Current Perspectives on the Immunosuppressive Niche and Role of Fibrosis in Hepatocellular Carcinoma and the Development of Antitumor Immunity

Immune checkpoint inhibitors have become the mainstay of treatment for hepatocellular carcinoma (HCC). However, they are ineffective in some cases. Previous studies have reported that genetic alterations in oncogenic pathways such as Wnt/β-catenin are the important triggers in HCC for primary refractoriness. T-cell exhaustion has been reported in various tumors and is likely to play a prominent role in the emergence of HCC due to chronic inflammation and cirrhosis-associated immune dysfunction. Immunosuppressive cells including regulatory T-cells and tumor-associated macrophages infiltrating the tumor are associated with hyperprogressive disease in the early stages of immune checkpoint inhibitor treatment. In addition, stellate cells and tumor-associated fibroblasts create an abundant desmoplastic environment by producing extracellular matrix. This strongly contributes to epithelial to mesenchymal transition via signaling activities including transforming growth factor beta, Wnt/β-catenin, and Hippo pathway. The abundant desmoplastic environment has been demonstrated in pancreatic ductal adenocarcinoma and cholangiocarcinoma to suppress cytotoxic T-cell infiltration, PD-L1 expression, and neoantigen expression, resulting in a highly immunosuppressive niche. It is possible that a similar immunosuppressive environment is created in HCC with advanced fibrosis in the background liver. Although sufficient understanding is required for the establishment of immune therapies of HCC, further investigations are still required in this field.

Deciphering Mesenchymal Drivers of Human Dupuytren's Disease at Single-Cell Level

Dupuytren's disease (DD) is a common, progressive fibroproliferative disease affecting the palmar fascia of the hands, causing fingers to irreversibly flex toward the palm with significant loss of function. Surgical treatments are limited; therefore, effective new therapies for DD are urgently required. To identify the key cellular and molecular pathways driving DD, we employed single-cell RNA sequencing, profiling the transcriptomes of 35,250 human single cells from DD, nonpathogenic fascia, and healthy dermis. We identify a DD-specific population of pathogenic PDPN+/FAP+ mesenchymal cells displaying an elevated expression of fibrillar collagens and profibrogenic genes. In silico trajectory analysis reveals resident fibroblasts to be the source of this pathogenic population. To resolve the processes governing DD progression, genes differentially expressed during fibroblast differentiation were identified, including upregulated TNFRSF12A and transcription factor SCX. Knockdown of SCX and blockade of TNFRSF12A inhibited the proliferation and altered the profibrotic gene expression of cultured human FAP+ mesenchymal cells, demonstrating a functional role for these genes in DD. The power of single-cell RNA sequencing is utilized to identify the major pathogenic mesenchymal subpopulations driving DD and the key molecular pathways regulating the DD-specific myofibroblast phenotype. Using this precision medicine approach, inhibition of TNFRSF12A has shown potential clinical utility in the treatment of DD.

Irinotecan/scFv co-loaded liposomes coaction on tumor cells and CAFs for enhanced colorectal cancer therapy

BACKGROUND

Cancer-associated fibroblasts (CAFs), as an important component of stroma, not only supply the "soils" to promote tumor invasion and metastasis, but also form a physical barrier to hinder the penetration of therapeutic agents. Based on this, the combinational strategy that action on both tumor cells and CAFs simultaneously would be a promising approach for improving the antitumor effect.

RESULTS

In this study, the novel multifunctional liposomes (IRI-RGD/R9-sLip) were designed, which integrated the advantages including IRI and scFv co-loading, different targets, RGD mediated active targeting, R9 promoting cell efficient permeation and lysosomal escape. As expected, IRI-RGD/R9-sLip showed enhanced cytotoxicity in different cell models, effectively increased the accumulation in tumor sites, as well as exhibited deep permeation ability both in vitro and in vivo. Notably, IRI-RGD/R9-sLip not only exhibited superior in vivo anti-tumor effect in both CAFs-free and CAFs-abundant bearing mice models, but also presented excellent anti-metastasis efficiency in lung metastasis model.

CONCLUSION

In a word, the novel combinational strategy by coaction on both "seeds" and "soils" of the tumor provides a new approach for cancer therapy, and the prepared liposomes could efficiently improve the antitumor effect with promising clinical application prospects.

NF-кB c-Rel modulates pre-fibrotic changes in human fibroblasts

Skin fibrosis is one central hallmark of the heterogeneous autoimmune disease systemic sclerosis. So far, there are hardly any standardized and effective treatment options. Pathogenic mechanisms underlying fibrosis comprise excessive and uncontrolled myofibroblast differentiation, increased extracellular matrix protein (ECM) synthesis and an intensification of the forces exerted by the cytoskeleton. A deeper understanding of fibroblast transformation could help to prevent or reverse fibrosis by specifically interfering with abnormally regulated signaling pathways. The transcription factor NF-κB has been implicated in the progression of fibrotic processes. However, the cellular processes regulated by NF-κB in fibrosis as well as the NF-κB isoforms preferentially involved are still completely unknown. In an in vitro model of fibrosis, we consistently observed the induction of the c-Rel subunit of NF-κB. Functional abrogation of c-Rel by siRNA resulted in diminished cell contractility of dermal fibroblasts in relaxed, but not in stressed 3D collagen matrices. Furthermore, directed migration was reduced after c-Rel silencing and total N-cadherin expression level was diminished, possibly mediating the observed cellular defects. Therefore, NF-кB c-Rel impacts central cellular adhesion markers and processes which negatively regulate fibrotic progression in SSc pathophysiology.

Fighting the Fiber: Targeting Collagen in Lung Fibrosis

Organ fibrosis is characterized by epithelial injury and aberrant tissue repair, where activated effector cells, mostly fibroblasts and myofibroblasts, excessively deposit collagen into the extracellular matrix. Fibrosis frequently results in organ failure and has been estimated to contribute to at least one third of all global deaths. Also lung fibrosis, in particular idiopathic pulmonary fibrosis (IPF), is a fatal disease with rising incidence worldwide. As current treatment options targeting fibrogenesis are insufficient, there is an urgent need for novel therapeutic strategies. During the last decade, several studies have proposed to target intra- and extracellular components of the collagen biosynthesis, maturation, and degradation machinery. This includes intra- and extracellular targets directly acting on collagen gene products, but also such that anabolize essential building blocks of collagen, in particular glycine and proline biosynthetic enzymes. Collagen, however, is a ubiquitous molecule in the body and fulfils essential functions as a macromolecular scaffold, growth factor reservoir, and receptor binding site in virtually every tissue. This review summarizes recent advances and future directions in this field. Evidence for the proposed therapeutic targets and where they currently stand in terms of clinical drug development for treatment of fibrotic disease is provided. The drug targets are furthermore discussed in light of (1) specificity for collagen biosynthesis, maturation and degradation, and (2) specificity for disease-associated collagen. As therapeutic success and safety of these drugs may largely depend on targeted delivery, different strategies for specific delivery to the main effector cells and to the extracellular matrix are discussed.

Fibroblast Activation Protein Targeted Photodynamic Therapy Selectively Kills Activated Skin Fibroblasts from Systemic Sclerosis Patients and Prevents Tissue Contraction

Systemic sclerosis (SSc) is a rare, severe, auto-immune disease characterized by inflammation, vasculopathy and fibrosis. Activated (myo)fibroblasts are crucial drivers of this fibrosis. By exploiting their expression of fibroblast activation protein (FAP) to perform targeted photodynamic therapy (tPDT), we can locoregionally deplete these pathogenic cells. In this study, we explored the use of FAP-tPDT in primary skin fibroblasts from SSc patients, both in 2D and 3D cultures. Method: The FAP targeting antibody 28H1 was conjugated with the photosensitizer IRDye700DX. Primary skin fibroblasts were obtained from lesional skin biopsies of SSc patients via spontaneous outgrowth and subsequently cultured on plastic or collagen type I. For 2D FAP-tPDT, cells were incubated in buffer with or without the antibody-photosensitizer construct, washed after 4 h and exposed to λ = 689 nm light. Cell viability was measured using CellTiter Glo^®®. For 3D FAP-tPDT, cells were seeded in collagen plugs and underwent the same treatment procedure. Contraction of the plugs was followed over time to determine myofibroblast activity. Results: FAP-tPDT resulted in antibody-dose dependent cytotoxicity in primary skin fibroblasts upon light exposure. Cells not exposed to light or incubated with an irrelevant antibody-photosensitizer construct did not show this response. FAP-tPDT fully prevented contraction of collagen plugs seeded with primary SSc fibroblasts. Even incubation with a very low dose of antibody (0.4 nM) inhibited contraction in 2 out of 3 donors. Conclusions: Here we have shown, for the first time, the potential of FAP-tPDT for the treatment of fibrosis in SSc skin.

Molecular Mechanisms and Cellular Contribution from Lung Fibrosis to Lung Cancer Development

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, fibrosing interstitial lung disease (ILD) of unknown aetiology, with a median survival of 2-4 years from the time of diagnosis. Although IPF has unknown aetiology by definition, there have been identified several risks factors increasing the probability of the onset and progression of the disease in IPF patients such as cigarette smoking and environmental risk factors associated with domestic and occupational exposure. Among them, cigarette smoking together with concomitant emphysema might predispose IPF patients to lung cancer (LC), mostly to non-small cell lung cancer (NSCLC), increasing the risk of lung cancer development. To this purpose, IPF and LC share several cellular and molecular processes driving the progression of both pathologies such as fibroblast transition proliferation and activation, endoplasmic reticulum stress, oxidative stress, and many genetic and epigenetic markers that predispose IPF patients to LC development. Nintedanib, a tyrosine-kinase inhibitor, was firstly developed as an anticancer drug and then recognized as an anti-fibrotic agent based on the common target molecular pathway. In this review our aim is to describe the updated studies on common cellular and molecular mechanisms between IPF and lung cancer, knowledge of which might help to find novel therapeutic targets for this disease combination.

DOCK2 Promotes Pleural Fibrosis by Modulating Mesothelial to Mesenchymal Transition

Mesothelial to mesenchymal transition (MesoMT) is one of the crucial mechanisms underlying pleural fibrosis, which results in restrictive lung disease. DOCK2 plays important roles in immune functions, however, its role in pleural fibrosis particularly MesoMT remains unknown. We found that DOCK2 and the MesoMT maker α-SMA were significantly elevated and colocalized in the thickened pleura of patients with nonspecific pleuritis, suggesting the involvement of DOCK2 in the pathogenesis of MesoMT and pleural fibrosis. Likewise, data from three different pleural fibrosis models (TGF-β, carbon black/bleomycin, and streptococcal empyema) consistently demonstrated DOCK2 upregulation and its colocalization with α-SMA in the pleura. In addition, induced DOCK2 colocalized with the mesothelial marker calretinin, implicating DOCK2 in the regulation of MesoMT. Our in vivo data also showed that DOCK2 knockout mice were protected from Streptococcus pneumoniae induced pleural fibrosis, impaired lung compliance, and collagen deposition. To determine the involvement of DOCK2 in MesoMT, we treated primary human pleural mesothelial cells with the potent MesoMT inducer TGF-β. TGF-β significantly induced DOCK2 expression in a time-dependent manner, along with α-SMA, collagen 1, and fibronectin. Furthermore, DOCK2 knockdown significantly attenuated TGF-β induced α-SMA, collagen 1 and fibronectin expression, suggesting the importance of DOCK2 in TGF-β induced MesoMT. DOCK2 knockdown also inhibited TGF-β induced Snail upregulation, which may account for its role in regulating MesoMT. Taken together, the current study provides evidence that DOCK2 contributes to the pathogenesis of pleural fibrosis by mediating MesoMT and deposition of neomatrix and may represent a novel target for its prevention or treatment.

ELTD1 Activation Induces an Endothelial-EMT Transition to a Myofibroblast Phenotype

ELTD1 is expressed in endothelial and vascular smooth muscle cells and has a role in angiogenesis. It has been classified as an adhesion GPCR, but as yet, no ligand has been identified and its function remains unknown. To establish its role, ELTD1 was overexpressed in endothelial cells. Expression and consequently ligand independent activation of ELTD1 results in endothelial-mesenchymal transistion (EndMT) with a loss of cell-cell contact, formation of stress fibres and mature focal adhesions and an increased expression of smooth muscle actin. The effect was pro-angiogenic, increasing Matrigel network formation and endothelial sprouting. RNA-Seq analysis after the cells had undergone EndMT revealed large increases in chemokines and cytokines involved in regulating immune response. Gene set enrichment analysis of the data identified a number of pathways involved in myofibroblast biology suggesting that the endothelial cells had undergone a type II EMT. This type of EMT is involved in wound repair and is closely associated with inflammation implicating ELTD1 in these processes.

Modulation of Oxidative Phosphorylation with IM156 Attenuates Mitochondrial Metabolic Reprogramming and Inhibits Pulmonary Fibrosis

Metabolic reprogramming of the myofibroblast plays a fundamental role in the pathogenesis of fibrosing interstitial lung diseases. Here, we characterized the in vitro and in vivo metabolic and anti-fibrotic effects of IM156, an oxidative phosphorylation (OXPHOS) modulator that acts by inhibiting Protein Complex 1 (PC1). In vitro, IM156 inhibited TGFβ-dependent increases in mitochondrial oxygen consumption rate and expression of myofibroblast markers in human pulmonary fibroblasts without altering cell viability or adding to TGF-β induced increases in the extracellular acidification rate (ECAR). IM156 significantly increased cellular AMPK phosphorylation and was 60-fold more potent than metformin. In vivo, chronic oral administration of IM156 was highly distributed to major peripheral organs (i.e. lung, liver, kidney, heart) and had significant dose-related effects on the plasma metabolome consistent with OXPHOS modulation and AMPK activation. IM156 increased glycolysis, lipolysis, β-oxidation and amino acids, and decreased free fatty acids, TCA cycle activity and protein synthesis. In the murine bleomycin model of pulmonary fibrosis, daily oral administration of IM156 administered 7 days after lung injury, attenuated body/lung weight changes, and reduced lung fibrosis and inflammatory cell infiltration. The plasma exposures of IM156 were comparable to well-tolerated doses in human studies. In conclusion, the metabolic and anti-fibrotic effects of IM156 suggest that OXPHOS modulation can attenuate myofibroblast metabolic reprogramming and support testing IM156 as a therapy for IPF and other fibrotic diseases. Significance Statement Fibrosing Interstitial Lung Diseases (FILD) have a poor prognosis and current anti-fibrotic treatments have significant limitations. This study demonstrates that attenuation of fibrogenic metabolic remodeling, by modulation of OXPHOS with IM156, prevents the myofibroblast phenotype/collagen deposition and is a potentially effective and translational anti-fibrotic strategy.

Tumor-Associated Fibroblast-Targeting Nanoparticles for Enhancing Solid Tumor Therapy: Progress and Challenges

Even though nanoparticle drug delivery systems (nanoDDSs) have improved antitumor efficacy by delivering more drugs to tumor sites compared to free and unencapsulated therapeutics, achieving satisfactory distribution and penetration of nanoDDSs inside solid tumors, especially in stromal fibrous tumors, remains challenging. As one of the most common stromal cells in solid tumors, tumor-associated fibroblasts (TAFs) not only promote tumor growth and metastasis but also reduce the drug delivery efficiency of nanoparticles through the tumor's inherent physical and physiological barriers. Thus, TAFs have been emerging as attractive targets, and TAF-targeting nanotherapeutics have been extensively explored to enhance the tumor delivery efficiency and efficacy of various anticancer agents. The purpose of this Review is to opportunely summarize the underlying mechanisms of TAFs on obstructing nanoparticle-mediated drug delivery into tumors and discuss the current advances of a plethora of nanotherapeutic approaches for effectively targeting TAFs.

Targeted inhibition of PI3 kinase/mTOR specifically in fibrotic lung fibroblasts suppresses pulmonary fibrosis in experimental models

Idiopathic pulmonary fibrosis (IPF) is a lethal disease with an average life expectancy of 3 to 5 years. IPF is characterized by progressive stiffening of the lung parenchyma due to excessive deposition of collagen, leading to gradual failure of gas exchange. Although two therapeutic agents have been approved from the FDA for IPF, they only slow disease progression with little impact on outcome. To develop a more effective therapy, we have exploited the fact that collagen-producing myofibroblasts express a membrane-spanning protein, fibroblast activation protein (FAP), that exhibits limited if any expression on other cell types. Because collagen-producing myofibroblasts are only found in fibrotic tissues, solid tumors, and healing wounds, FAP constitutes an excellent marker for targeted delivery of drugs to tissues undergoing pathologic fibrosis. We demonstrate here that a low-molecular weight FAP ligand can be used to deliver imaging and therapeutic agents selectively to FAP-expressing cells. Because induction of collagen synthesis is associated with phosphatidylinositol 3-kinase (PI3K) activation, we designed a FAP-targeted PI3K inhibitor that selectively targets FAP-expressing human IPF lung fibroblasts and potently inhibited collagen synthesis. Moreover, we showed that administration of the inhibitor in a mouse model of IPF inhibited PI3K activation in fibrotic lungs, suppressed production of hydroxyproline (major building block of collagen), reduced collagen deposition, and increased mouse survival. Collectively, these studies suggest that a FAP-targeted PI3K inhibitor might be promising for treating IPF.

Recapitulating Tumorigenesis in vitro: Opportunities and Challenges of 3D Bioprinting

Cancer is considered one of the most predominant diseases in the world and one of the principal causes of mortality per year. The cellular and molecular mechanisms involved in the development and establishment of solid tumors can be defined as tumorigenesis. Recent technological advances in the 3D cell culture field have enabled the recapitulation of tumorigenesis in vitro, including the complexity of stromal microenvironment. The establishment of these 3D solid tumor models has a crucial role in personalized medicine and drug discovery. Recently, spheroids and organoids are being largely explored as 3D solid tumor models for recreating tumorigenesis in vitro. In spheroids, the solid tumor can be recreated from cancer cells, cancer stem cells, stromal and immune cell lineages. Organoids must be derived from tumor biopsies, including cancer and cancer stem cells. Both models are considered as a suitable model for drug assessment and high-throughput screening. The main advantages of 3D bioprinting are its ability to engineer complex and controllable 3D tissue models in a higher resolution. Although 3D bioprinting represents a promising technology, main challenges need to be addressed to improve the results in cancer research. The aim of this review is to explore (1) the principal cell components and extracellular matrix composition of solid tumor microenvironment; (2) the recapitulation of tumorigenesis in vitro using spheroids and organoids as 3D culture models; and (3) the opportunities, challenges, and applications of 3D bioprinting in this area.