Gene transfer of hepatocyte growth factor by electroporation reduces bleomycin-induced lung fibrosis

Enhanced secretion of hepatocyte growth factor in human umbilical cord mesenchymal stem cells ameliorates pulmonary fibrosis induced by bleomycin in rats

Umbilical cord mesenchymal stem cells (UCMSCs) are a reportedly promising choice in the treatment of irreversible pulmonary fibrosis and lethal interstitial lung disease with limited drug treatment options. In this study, we investigated the therapeutic efficacy of UCMSCs overexpressing hepatocyte growth factor (HGF), which is considered one of the main anti-fibrotic factors secreted by MSCs. Adenovirus vector carrying the HGF gene was transfected into UCMSCs to produce HGF-modified UCMSCs (HGF-UCMSCs). Transfection promoted the proliferation of UCMSCs and did not change the morphology, and differentiation ability, or biomarkers. Rats were injected with HGF-UCMSCs on days 7 and 11 after intratracheal administration of bleomycin (10 mg/kg). We performed an analysis of histopathology and lung function to evaluate the anti-fibrotic effect. The results showed that HGF-UCMSCs decreased the Ashcroft scores in hematoxylin and eosin-stained sections, the percentage positive area in Masson trichrome-stained sections, and the hydroxyproline level in lungs. Forced expiratory volume in the first 300 m/forced vital capacity was also improved by HGF-UCMSCs. To explore the possible therapeutic mechanism of HGF-UCMSCs, we detected inflammatory factors in the lungs and performed mRNA sequencing in UCMSCs and HGF-UCMSCs. The data indicated that inhibition of interleukin-17 in the lung may be related to the anti-fibrosis of HGF-UCMSCs, and overexpressed HGF probably played a primary role in the treatment. Collectively, our study findings suggested that the overexpression of HGF may improve the anti-fibrotic effect of UCMSCs through directly or indirectly interacting with interleukin-17-producing cells in fibrotic lungs.

Blocking Toll-like receptor 9 attenuates bleomycin-induced pulmonary injury

Background

Acute respiratory distress syndrome (ARDS) is one of the most common complications in coronavirus disease 2019 patients suffering from acute lung injury (ALI). In ARDS, marked distortion of pulmonary architecture has been reported. The pulmonary lesions in ARDS include hemodynamic derangements (such as alveolar edema and hemorrhage), vascular and bronchiolar damage, interstitial inflammatory cellular aggregations, and eventually fibrosis. Bleomycin induces ARDS-representative pulmonary damage in mice and rats; therefore, we used bleomycin model mice in our study. Recently, Toll-like receptor 9 (TLR9) was implicated in the development of ARDS and ALI.

Methods

In this study, we evaluated the efficiency of a TLR9 blocker (ODN2088) on bleomycin-induced pulmonary damage. We measured the apoptosis rate, inflammatory reaction, and fibroplasia in bleomycin- and bleomycin + ODN2088-treated mice.

Results

Our results showed a significant amelioration in bleomycin-induced damage to pulmonary architecture following ODN2088 treatment. A marked decrease in pulmonary epithelial and endothelial apoptosis rate as measured by cleaved caspase-3 expression, inflammatory reaction as indicated by tumor necrosis factor α expression, and pulmonary fibrosis as demonstrated by Van Gieson staining and α-smooth muscle actin immunohistochemistry were observed following ODN2088 treatment.

Conclusions

All these findings indicate that blocking downstream TLR9 signaling could be beneficial in prevention or mitigation of ARDS through hemodynamic derangements, inflammation, apoptosis, and fibrosis.

Corneal Opacity: Cell Biological Determinants of the Transition From Transparency to Transient Haze to Scarring Fibrosis, and Resolution, After Injury

Purpose

To highlight the cellular, matrix, and hydration changes associated with opacity that occurs in the corneal stroma after injury.

Methods

Review of the literature.

Results

The regulated transition of keratocytes to corneal fibroblasts and myofibroblasts, and of bone marrow-derived fibrocytes to myofibroblasts, is in large part modulated by transforming growth factor beta (TGFβ) entry into the stroma after injury to the epithelial basement membrane (EBM) and/or Descemet's membrane. The composition, stoichiometry, and organization of the stromal extracellular matrix components and water is altered by corneal fibroblast and myofibroblast production of large amounts of collagen type I and other extracellular matrix components-resulting in varying levels of stromal opacity, depending on the intensity of the healing response. Regeneration of EBM and/or Descemet's membrane, and stromal cell production of non-EBM collagen type IV, reestablishes control of TGFβ entry and activity, and triggers TGFβ-dependent myofibroblast apoptosis. Eventually, corneal fibroblasts also disappear, and repopulating keratocytes reorganize the disordered extracellular matrix to reestablish transparency.

Conclusions

Injuries to the cornea produce varying amounts of corneal opacity depending on the magnitude of cellular and molecular responses to injury. The EBM and Descemet's membrane are key regulators of stromal cellularity through their modulation of TGFβ. After injury to the cornea, depending on the severity of the insult, and possibly genetic factors, trace opacity to severe scarring fibrosis develops. Stromal cellularity, and the functions of different cell types, are the major determinants of the level of the stromal opacity.

Distal Lung Microenvironment Triggers Release of Mediators Recognized as Potential Systemic Biomarkers for Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease with an unmet need of biomarkers that can aid in the diagnostic and prognostic assessment of the disease and response to treatment. In this two-part explorative proteomic study, we demonstrate how proteins associated with tissue remodeling, inflammation and chemotaxis such as MMP7, CXCL13 and CCL19 are released in response to aberrant extracellular matrix (ECM) in IPF lung. We used a novel ex vivo model where decellularized lung tissue from IPF patients and healthy donors were repopulated with healthy fibroblasts to monitor locally released mediators. Results were validated in longitudinally collected serum samples from 38 IPF patients and from 77 healthy controls. We demonstrate how proteins elevated in the ex vivo model (e.g., MMP7), and other serum proteins found elevated in IPF patients such as HGF, VEGFA, MCP-3, IL-6 and TNFRSF12A, are associated with disease severity and progression and their response to antifibrotic treatment. Our study supports the model’s applicability in studying mechanisms involved in IPF and provides additional evidence for both established and potentially new biomarkers in IPF.

Efficacy of Combined in-vivo Electroporation-Mediated Gene Transfer of VEGF, HGF, and IL-10 on Skin Flap Survival, Monitored by Label-Free Optical Imaging: A Feasibility Study

Preventing surgical flaps necrosis remains challenging. Laser Doppler imaging and ultrasound can monitor blood flow in flap regions, but they do not directly measure the cellular response to ischemia. The study aimed to investigate the efficacy of synergistic in-vivo electroporation-mediated gene transfer of interleukin 10 (IL-10) with either hepatocyte growth factor (HGF) or vascular endothelial growth factor (VEGF) on the survival of a modified McFarlane flap, and to evaluate the effect of the treatment on cell metabolism, using label-free fluorescence lifetime imaging. Fifteen male Wistar rats (290–320 g) were randomly divided in three groups: group-A (control group) underwent surgery and received no gene transfer. Group-B received electroporation mediated hIL-10 gene delivery 24 h before and VEGF gene delivery 24 h after surgery. Group-C received electroporation mediated hIL-10 gene delivery 24 h before and hHGF gene delivery 24 h after surgery. The animals were assessed clinically and histologically. In addition, label-free fluorescence lifetime imaging was performed on the flap. Synergistic electroporation mediated gene delivery significantly decreased flap necrosis (P = 0.0079) and increased mean vessel density (P = 0.0079) in treatment groups B and C compared to control group-A. NADH fluorescence lifetime analysis indicated an increase in oxidative phosphorylation in the epidermis of the group-B (P = 0.039) relative to controls. These findings suggested synergistic in-vivo electroporation-mediated gene transfer as a promising therapeutic approach to enhance viability and vascularity of skin flap. Furthermore, the study showed that combinational gene therapy promoted an increase in tissue perfusion and a relative increase in oxidative metabolism within the epithelium.

Pulmonary gene delivery-Realities and possibilities

Delivery of genetic material to tissues in vivo is an important technique used in research settings and is the foundation upon which clinical gene therapy is built. The lung is a prime target for gene delivery due to a host of genetic, acquired, and infectious diseases that manifest themselves there, resulting in many pathologies. However, the in vivo delivery of genetic material to the lung remains a practical problem clinically and is considered the major obstacle needed to be overcome for gene therapy. Currently there are four main strategies for in vivo gene delivery to the lung: viral vectors, liposomes, nanoparticles, and electroporation. Viral delivery uses several different genetically modified viruses that enter the cell and express desired genes that have been inserted to the viral genome. Liposomes use combinations of charged and neutral lipids that can encapsulate genetic cargo and enter cells through endogenous mechanisms, thereby delivering their cargoes. Nanoparticles are defined by their size (typically less than 100 nm) and are made up of many different classes of building blocks, including biological and synthetic polymers, cell penetrant and other peptides, and dendrimers, that also enter cells through endogenous mechanisms. Electroporation uses mild to moderate electrical pulses to create pores in the cell membrane through which delivered genetic material can enter a cell. An emerging fifth category, exosomes and extracellular vesicles, may have advantages of both viral and non-viral approaches. These extracellular vesicles bud from cellular membranes containing receptors and ligands that may aid cell targeting and which can be loaded with genetic material for efficient transfer. Each of these vectors can be used for different gene delivery applications based on mechanisms of action, side-effects, and other factors, and their use in the lung and possible clinical considerations is the primary focus of this review.

Genetic Delivery and Gene Therapy in Pulmonary Hypertension

Pulmonary hypertension (PH) is a progressive complex fatal disease of multiple etiologies. Hyperproliferation and resistance to apoptosis of vascular cells of intimal, medial, and adventitial layers of pulmonary vessels trigger excessive pulmonary vascular remodeling and vasoconstriction in the course of pulmonary arterial hypertension (PAH), a subgroup of PH. Multiple gene mutation/s or dysregulated gene expression contribute to the pathogenesis of PAH by endorsing the proliferation and promoting the resistance to apoptosis of pulmonary vascular cells. Given the vital role of these cells in PAH progression, the development of safe and efficient-gene therapeutic approaches that lead to restoration or down-regulation of gene expression, generally involved in the etiology of the disease is the need of the hour. Currently, none of the FDA-approved drugs provides a cure against PH, hence innovative tools may offer a novel treatment paradigm for this progressive and lethal disorder by silencing pathological genes, expressing therapeutic proteins, or through gene-editing applications. Here, we review the effectiveness and limitations of the presently available gene therapy approaches for PH. We provide a brief survey of commonly existing and currently applicable gene transfer methods for pulmonary vascular cells in vitro and describe some more recent developments for gene delivery existing in the field of PH in vivo.

Non-viral Gene Delivery Methods for Bone and Joints

Viral carrier transport efficiency of gene delivery is high, depending on the type of vector. However, viral delivery poses significant safety concerns such as inefficient/unpredictable reprogramming outcomes, genomic integration, as well as unwarranted immune responses and toxicity. Thus, non-viral gene delivery methods are more feasible for translation as these allow safer delivery of genes and can modulate gene expression transiently both in vivo, ex vivo, and in vitro. Based on current studies, the efficiency of these technologies appears to be more limited, but they are appealing for clinical translation. This review presents a summary of recent advancements in orthopedics, where primarily bone and joints from the musculoskeletal apparatus were targeted. In connective tissues, which are known to have a poor healing capacity, and have a relatively low cell-density, i.e., articular cartilage, bone, and the intervertebral disk (IVD) several approaches have recently been undertaken. We provide a brief overview of the existing technologies, using nano-spheres/engineered vesicles, lipofection, and in vivo electroporation. Here, delivery for microRNA (miRNA), and silencing RNA (siRNA) and DNA plasmids will be discussed. Recent studies will be summarized that aimed to improve regeneration of these tissues, involving the delivery of bone morphogenic proteins (BMPs), such as BMP2 for improvement of bone healing. For articular cartilage/osteochondral junction, non-viral methods concentrate on targeted delivery to chondrocytes or MSCs for tissue engineering-based approaches. For the IVD, growth factors such as GDF5 or GDF6 or developmental transcription factors such as Brachyury or FOXF1 seem to be of high clinical interest. However, the most efficient method of gene transfer is still elusive, as several preclinical studies have reported many different non-viral methods and clinical translation of these techniques still needs to be validated. Here we discuss the non-viral methods applied for bone and joint and propose methods that can be promising in clinical use.

The Efficacy of Topical HGF on Corneal Fibrosis and Epithelial Healing after Scar-Producing PRK Injury in Rabbits

Purpose

To determine the effect of topical hepatocyte growth factor (HGF) on myofibroblast development and corneal opacity after fibrosis-producing photorefractive keratectomy (PRK).

Methods

Twelve New Zealand rabbits had transepithelial PRK. Six rabbits received topical recombinant human HGF (rhHGF) (50 µL of 0.1 mg/mL) 3 times a day for 1 week beginning 6 hours prior surgery and until full closure of the epithelium, and 6 control rabbits received vehicle by the same schedule. Slit lamp photos were taken immediately and at 43 to 45 hours after surgery to determine the rate of epithelial healing. Slit lamp photographs and immunohistochemistry for α-smooth muscle actin were analyzed at 1 month in masked fashion.

Results

The rhHGF group tended to have slower re-epithelization when compared with the controls, but no statistically significant difference was noted (P = 0.62). There was no significant difference in the density of myofibroblasts in the central stroma (P = 0.49) or corneal opacity (P = 0.84) between the HGF and control groups at 1 month after PRK.

Conclusions

Topical rhHGF applied three times a day during the early postoperative period prior to epithelial closure did not significantly change the corneal epithelial healing rate, myofibroblast density, or opacity compared with vehicle after transepithelial -9.0 D PRK injury of the central cornea in rabbits.

Translational Relevance

HGF has been reported to decrease myofibroblast generation and fibrosis in many organs, but topical HGF applied to the cornea until epithelial healing had no effect on scarring fibrosis in rabbit corneas.

The Tyrosine Kinase Inhibitor TAS-115 Attenuates Bleomycin-induced Lung Fibrosis in Mice

The signaling pathways of growth factors, including platelet-derived growth factor, can be considered specific targets for overcoming the poor prognosis of idiopathic pulmonary fibrosis. Nintedanib, the recently approved multiple kinase inhibitor, has shown promising antifibrotic effects in patients with idiopathic pulmonary fibrosis; however, its efficacy is still limited, and in some cases, treatment discontinuation is necessary owing to toxicities such as gastrointestinal disorders. Therefore, more effective agents with less toxicity are still needed. TAS-115 is a novel multiple tyrosine kinase inhibitor that preferably targets platelet-derived growth factor receptor (PDGFR), vascular endothelial growth factor receptor, and c-FMS in addition to other molecules. In this study, we evaluated the antifibrotic effect of TAS-115 on pulmonary fibrosis in vitro and in vivo. TAS-115 inhibited the phosphorylation of PDGFR on human lung fibroblast cell line MRC-5 cells and suppressed their platelet-derived growth factor-induced proliferation and migration. Furthermore, TAS-115 inhibited the phosphorylation of c-FMS, a receptor of macrophage colony-stimulating factor, in murine bone marrow-derived macrophages and decreased the production of CCL2, another key molecule for inducing pulmonary fibrosis, under the stimulation of macrophage colony-stimulating factor. Importantly, the inhibitory effects of TAS-115 on both PDGFR and c-FMS were 3- to 10-fold higher than those of nintedanib. In a mouse model of bleomycin-induced pulmonary fibrosis, TAS-115 significantly inhibited the development of pulmonary fibrosis and the collagen deposition in bleomycin-treated lungs. These data suggest that strong inhibition of PDGFR and c-FMS by TAS-115 may be a promising strategy for overcoming the intractable pathogenesis of pulmonary fibrosis.

The Effects of Adipose Stem Cell-Conditioned Media on Fibrogenesis of Dermal Fibroblasts Stimulated by Transforming Growth Factor-β1

Adipose-derived stem cells (ASCs) have been shown to enhance wound healing by human dermal fibroblasts; however, the interactions between ASCs and fibroblasts during injury remain unclear. Fibroblasts were treated with ASC-conditioned medium (ASC-CM) with and without transforming growth factor-β1 (TGF-β1) stimulation. Fibroblast proliferation, apoptosis, differentiation and expression of extracellular matrix genes and proteins, type I collagen, and type III collagen were measured. Also, wound-healing effect of ASC-CM was verified with in vivo animal study. ASC-CM inhibited proliferation and enhanced apoptosis of fibroblasts under TGF-β1 stimulation. Furthermore, 10% ASC-CM inhibited α-smooth muscle actin expression in fibroblasts, whereas 100% ASC-CM increased collagen, especially type III, expression in fibroblasts. ASC-CM was found to contain more basic fibroblast growth factor than hepatocyte growth factor, and 100% ASC-CM increased hepatocyte growth factor gene expression in fibroblasts. These results suggest ASCs affect fibrogenesis by dermal fibroblasts stimulated with TGF-β1 via paracrine signaling by adipocytokines present in ASC-CM. These results also suggest that higher concentrations of ASC-CM increase collagen production and inhibit fibroblast proliferation to avoid excessive fibrogenesis. We demonstrated that a lower ASC-CM concentration attenuated fibroblast differentiation. Additionally, 100% ASC-CM significantly reduced the wound size in an in vivo wound-healing model. In this study, we provided evidence that ASCs modulate fibrogenesis by fibroblasts via paracrine signaling, suggesting that application of ASCs during wound healing may improve the quality of wound repair.

Novel Combination BMP7 and HGF Gene Therapy Instigates Selective Myofibroblast Apoptosis and Reduces Corneal Haze In Vivo

Purpose

We tested the potential of bone morphogenic protein 7 (BMP7) and hepatocyte growth factor (HGF) combination gene therapy to treat preformed corneal fibrosis using established rabbit in vivo and human in vitro models.

Methods

Eighteen New Zealand White rabbits were used. Corneal fibrosis was produced by alkali injury. Twenty-four hours after scar formation, cornea received topically either balanced salt solution (BSS; n = 6), polyethylenimine-conjugated gold nanoparticle (PEI2-GNP)-naked plasmid (n = 6) or PEI2-GNP plasmids expressing BMP7 and HGF genes (n = 6). Donor human corneas were used to obtain primary human corneal fibroblasts and myofibroblasts for mechanistic studies. Gene therapy effects on corneal fibrosis and ocular safety were evaluated by slit-lamp microscope, stereo microscopes, quantitative real-time PCR, immunofluorescence, TUNEL, modified MacDonald-Shadduck scoring system, and Draize tests.

Results

PEI2-GNP–mediated BMP7+HGF gene therapy significantly decreased corneal fibrosis in live rabbits in vivo (Fantes scale was 0.6 in BMP7+HGF-treated eyes compared to 3.3 in −therapy group; P < 0.001). Corneas that received BMP7+HGF demonstrated significantly reduced mRNA levels of profibrotic genes: α-SMA (3.2-fold; P < 0.01), fibronectin (2.3-fold, P < 0.01), collagen I (2.1-fold, P < 0.01), collagen III (1.6-fold, P < 0.01), and collagen IV (1.9-fold, P < 0.01) compared to the −therapy corneas. Furthermore, BMP7+HGF-treated corneas showed significantly fewer myofibroblasts compared to the −therapy controls (83%; P < 0.001). The PEI2-GNP introduced >10⁴ gene copies per microgram DNA of BMP7 and HGF genes. The recombinant HGF rendered apoptosis in corneal myofibroblasts but not in fibroblasts. Localized topical BMP7+HGF therapy showed no ocular toxicity.

Conclusions

Localized topical BMP7+HGF gene therapy treats corneal fibrosis and restores transparency in vivo mitigating excessive healing and rendering selective apoptosis in myofibroblasts.

Multipotent mesenchymal stem cells in lung fibrosis

Rationale

Stem cells have been identified in the human lung; however, their role in lung disease is not clear. We aimed to isolate mesenchymal stem cells (MSC) from human lung tissue and to study their in vitro properties.

Methods

MSC were cultured from lung tissue obtained from patients with fibrotic lung diseases (n = 17), from emphysema (n = 12), and normal lungs (n = 3). Immunofluorescence stainings were used to characterize MSC. The effect of MSC-conditioned media (MSC-CM) on fibroblast proliferation and on lung epithelial wound repair was studied.

Results

Expression of CD44, CD90, and CD105 characterized the cells as MSC. Moreover, the cells stained positive for the pluripotency markers Oct3/4 and Nanog. Positive co-stainings of chemokine receptor type 4 (CXCR4) with CD44, CD90 or CD105 indicated the cells are of bone marrow origin. MSC-CM significantly inhibited the proliferation of lung fibroblasts by 29% (p = 0.0001). Lung epithelial repair was markedly increased in the presence of MSC-CM (+ 32%). Significantly more MSC were obtained from fibrotic lungs than from emphysema or control lungs.

Conclusions

Our study demonstrates enhanced numbers of MSC in fibrotic lung tissue as compared to emphysema and normal lung. The cells inhibit the proliferation of fibroblasts and enhance epithelial repair in vitro. Further in vivo studies are needed to elucidate their potential role in the treatment of lung fibrosis.

Improvement of Flap Necrosis in a Rat Random Skin Flap Model by In Vivo Electroporation-Mediated HGF Gene Transfer

BACKGROUND

Despite great understanding of underlying mechanisms for flap necrosis and advances in surgical techniques, flap necrosis remains a critical issue. In the present study, the authors investigated the efficacy of electroporation-mediated hepatocyte growth factor (HGF) gene delivery to random dorsal skin flaps (McFarlane) to accelerate wound healing and reduce flap necrosis.

METHODS

Fifteen male Wistar rats (290 to 320 g) were divided randomly into three groups. Group a, the control group (n = 5), underwent surgery and received no gene transfer. Group b received electroporation-mediated HGF gene delivery 24 hours after surgery as a treatment. Group c received electroporation-mediated HGF gene delivery 24 hours before surgery as prophylaxis (n = 5). Planimetry, laser Doppler imaging, and immunohistochemistry were used to assess the efficacy of HGF gene therapy among the groups.

RESULTS

Electroporation-mediated HGF gene delivery significantly decreased flap necrosis percentage compared with the control group in prophylactic and treatment groups (p = 0.0317 and p = 0.0079, respectively) and significantly increased cutaneous perfusion compared with the control group (p = 0.0317 and p = 0.0159, respectively). Moreover, Spearman rank correlation showed a significant negative correlation between flap necrosis percentage and laser index (p = 0.0213 and r = -0.5964, respectively). Furthermore, significantly higher mean CD31 vessel density was detected in treatment and prophylactic groups (p = 0.0079 and p = 0.0159, respectively). In addition, quantitative image analysis revealed significantly higher HGF protein expression in groups b and c (p = 0.0079 and p = 0.0079, respectively).

CONCLUSION

These findings suggested in vivo electroporation-mediated HGF gene delivery enhanced viability and vascularity of the ischemic skin flap.

Efficacy of In Vivo Electroporation-Mediated IL-10 Gene Delivery on Survival of Skin Flaps

Despite advances in understanding the underlying mechanisms of flap necrosis and improvement in surgical techniques, skin flap necrosis after reconstructive surgery remains a crucial issue. We investigated the efficacy of electroporation-mediated IL-10 gene transfer to random skin flap with an aim to accelerate wound healing and improve skin flap survival. Nine male Wistar rats (300-330 g) were divided in two groups (a) control group (n = 5), only surgery no gene transfer, and (b) experimental group, received electroporation-mediated IL-10 gene transfer 24 h before the surgery as prophylaxis (n = 4). Random skin flap (McFarlane) was performed in both groups. Planimetry, Laser Doppler imaging, and immunohistochemistry were used to evaluate the effect of IL-10 gene transfer between study groups at day 7. Electroporation-mediated IL-10 gene transfer decreased percentage of flap necrosis (p value = 0.0159) and increased cutaneous perfusion compared to the control group (p value = 0.0159). In addition, Spearman's rank correlation showed a significant negative correlation between percentage of flap necrosis and Laser Index (p value = 0.0083, r -0.83, respectively). Furthermore, significantly higher mean CD31⁺ vessel density was detected in the experimental group compared to the control group (p value = 0.0159). Additionally, semi-quantitative image analysis showed lower inflammatory cell count in experimental group compared to control group (p value = 0.0317). In vivo electroporation-mediated IL-10 gene transfer reduced necrosis, enhanced survival and vascularity in the ischemic skin flap.

Treatment with a programmed cell death-1-specific antibody has little effect on afatinib- and naphthalene-induced acute pneumonitis in mice

Although several antibodies developed to target programmed cell death-1 (PD-1) and its ligand (PD-L1) have demonstrated great promise for the treatment of non-small cell lung cancer (NSCLC), and other malignancies, these therapeutic antibodies can cause pneumonitis. Furthermore, epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI)-induced pneumonitis was reported after treatment with anti PD-1 antibodies. We previously demonstrated that mice with naphthalene-induced airway epithelial injury developed severe gefitinib-induced pneumonitis through a neutrophil-dependent mechanism. The present study aimed to investigate whether treatment with afatinib, an EGFR-TKI that effectively targets EGFR mutation-positive NSCLC, and anti PD-1 antibodies induces pneumonitis in mice. C57BL/6J mice were treated intraperitoneally with naphthalene (200 mg/kg) on day 0. Afatinib (20 mg/kg) was administered orally on days -1 to 13. An anti-PD-1 antibody (0.2 mg/mice) was also administered intraperitoneally every 3 days from day 1 until day 13. The bronchoalveolar lavage fluid (BALF) and lung tissues were sampled on day 14. As observed previously with gefitinib, afatinib significantly increased the severity of histopathologic findings and the level of protein in BALF on day 14, compared to treatment with naphthalene alone. A combined anti-PD-1 antibody and afatinib treatment after naphthalene administration had yielded the same histopathological grade of lung inflammation as did afatinib treatment alone. Our results suggest that anti-PD-1 antibody treatment has little effect on afatinib-induced lung injury.

Hepatocyte growth factor secreted by bone marrow stem cell reduce ER stress and improves repair in alveolar epithelial II cells

Idiopathic Pulmonary Fibrosis (IPF) is a progressive, irreversible lung disease with complex pathophysiology. Evidence of endoplasmic reticulum (ER) stress has been reported in alveolar epithelial cells (AEC) in IPF patients. Secreted mediators from bone marrow stem cells (BMSC-cm) have regenerative properties. In this study we investigate the beneficial effects of BMSC-cm on ER stress response in primary AEC and ER stressed A549 cells. We hypothesize that BMSC-cm reduces ER stress. Primary AEC isolated from IPF patients were treated with BMSC-cm. To induce ER stress A549 cells were incubated with Tunicamycin or Thapsigargin and treated with BMSC-cm, or control media. Primary IPF-AEC had high Grp78 and CHOP gene expression, which was lowered after BMSC-cm treatment. Similar results were observed in ER stressed A549 cells. Alveolar epithelial repair increased in presence of BMSC-cm in ER stressed A549 cells. Hepatocyte growth factor (HGF) was detected in biologically relevant levels in BMSC-cm. Neutralization of HGF in BMSC-cm attenuated the beneficial effects of BMSC-cm including synthesis of surfactant protein C (SP-C) in primary AEC, indicating a crucial role of HGF in ER homeostasis and alveolar epithelial repair. Our data suggest that BMSC-cm may be a potential therapeutic option for treating pulmonary fibrosis.

Tissue remodelling in pulmonary fibrosis

Many lung diseases result in fibrotic remodelling. Fibrotic lung disorders can be divided into diseases with known and unknown aetiology. Among those with unknown aetiology, idiopathic pulmonary fibrosis (IPF) is a common diagnosis. Because of its progressive character leading to a rapid decline in lung function, it is a fatal disease with poor prognosis and limited therapeutic options. Thus, IPF has motivated many studies in the last few decades in order to increase our mechanistic understanding of the pathogenesis of the disease. The current concept suggests an ongoing injury of the alveolar epithelium, an impaired regeneration capacity, alveolar collapse and, finally, a fibroproliferative response. The origin of lung injury remains elusive but a diversity of factors, which will be discussed in this article, has been shown to be associated with IPF. Alveolar epithelial type II (AE2) cells play a key role in lung fibrosis and their crucial role for epithelial regeneration, stabilisation of alveoli and interaction with fibroblasts, all known to be responsible for collagen deposition, will be illustrated. Whereas mechanisms of collagen deposition and fibroproliferation are the focus of many studies in the field, the awareness of other mechanisms in this disease is currently limited to biochemical and imaging studies including quantitative assessments of lung structure in IPF and animal models assigning alveolar collapse and collapse induration crucial roles for the degradation of the lung resulting in de-aeration and loss of surface area. Dysfunctional AE2 cells, instable alveoli and mechanical stress trigger remodelling that consists of collapsed alveoli absorbed by fibrotic tissue (i.e., collapse induration).

Hepatocyte Growth Factor Is Required for Mesenchymal Stromal Cell Protection Against Bleomycin-Induced Pulmonary Fibrosis

: The incidence of idiopathic pulmonary fibrosis is on the rise and existing treatments have failed to halt or reverse disease progression. Mesenchymal stromal cells (MSCs) have potent cytoprotective effects, can promote tissue repair, and have demonstrated efficacy in a range of fibrotic lung diseases; however, the exact mechanisms of action remain to be elucidated. Chemical antagonists and short hairpin RNA knockdown were used to identify the mechanisms of action used by MSCs in promoting wound healing, proliferation, and inhibiting apoptosis. Using the bleomycin induced fibrosis model, the protective effects of early or late MSC administration were examined. The role for hepatocyte growth factor (HGF) in MSC protection against bleomycin lung injury was examined using HGF knockdown MSC. Terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling assay was performed on ex vivo lung sections to examine the effects of MSC on apoptosis. MSC conditioned media (CM) enhanced wound closure and inhibited apoptosis of pulmonary cells in vitro. HGF was required for MSC CM enhancement of epithelial cell proliferation and inhibition of apoptosis. In contrast, MSC required COX-2 for CM to inhibit fibroblast proliferation. In a murine model, early administration of MSC protected against bleomycin induced lung fibrosis and correlated with reduced levels of the proinflammatory cytokine interleukin-1β, reduced levels of apoptosis, and significantly increased levels of HGF. These protective effects were in part mediated by MSC derived HGF as HGF knockdown MSC were unable to protect against fibrosis in vivo. These findings delineate the mechanisms of MSC protection in a preclinical model of fibrotic lung disease.

SIGNIFICANCE

The mechanisms used by mesenchymal stromal cells (MSCs) in mediating protective effects in chronic models of lung disease are not understood and remain to be elucidated. These findings from in vitro studies highlight an important role for the MSC-derived soluble factors hepatocyte growth factor (HGF) and prostaglandin E₂ in promoting wound healing and inhibiting apoptosis. Furthermore, this study translates these findings demonstrating an important role for HGF in the protective effects mediated by MSC in vivo in the bleomycin model. These findings support a targeted approach to enhancing MSC therapy for fibrotic disease and highlight the importance of timing of MSC therapy.

Aliskiren attenuates bleomycin-induced pulmonary fibrosis in rats: focus on oxidative stress, advanced glycation end products, and matrix metalloproteinase-9

Pulmonary fibrosis is a progressive lung disorder with high mortality rate and limited successful treatment. This study was designed to assess the potential anti-oxidant and anti-fibrotic effects of aliskiren (Alsk) during bleomycin (BLM)-induced pulmonary fibrosis. Male Wistar rats were used as control untreated or treated with the following: a single dose of 2.5 mg/kg of BLM endotracheally and BLM and Alsk (either low dose 30 mg/kg/day or high dose 60 mg/kg/day), and another group was given Alsk 60 mg/kg/day alone. Alsk was given by gavage. Alsk anti-oxidant and anti-fibrotic effects were assessed. BLM significantly increased relative lung weight and the levels of lactate dehydrogenase and total and differential leucocytic count in bronchoalveolar lavage that was significantly ameliorated by high-dose Alsk treatment. As markers of oxidative stress, BLM caused a significant increase in the levels of lipid peroxides and nitric oxide accompanied with a significant decrease of superoxide dismutase and glutathione transferase enzymes. High-dose Alsk treatment restored these markers toward normal values. Alsk counteracted the overexpression of advanced glycation end products, matrix metalloproteinase-9 (MMP-9), and tissue inhibitor of metalloproteinases-1 in lung tissue induced by BLM. Fibrosis assessed by measuring hydroxyproline content, which markedly increased in the BLM group, was also significantly reduced by Alsk. These were confirmed by histopathological and immunohistochemical examination which revealed that Alsk attenuates signs of pulmonary fibrosis and decreased the overexpressed MMP-9 and transforming growth factor β1. Collectively, these findings indicate that Alsk has a potential anti-fibrotic effect beside its anti-oxidant activity.

The hepatocyte growth factor-expressing character is required for mesenchymal stem cells to protect the lung injured by lipopolysaccharide in vivo

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a life-threatening condition in critically ill patients. Recently, we have found that mesenchymal stem cells (MSC) improved the permeability of human lung microvascular endothelial cells by secreting hepatocyte growth factor (HGF) in vitro. However, the properties and functions of MSC may change under complex circumstances in vivo. Here, we sought to determine the role of the HGF-expressing character of MSC in the therapeutic effects of MSC on ARDS in vivo.

METHODS

MSC with HGF gene knockdown (MSC-ShHGF) were constructed using lentiviral transduction. The HGF mRNA and protein levels in MSC-ShHGF were detected using quantitative real-time polymerase chain reaction and Western blotting analysis, respectively. HGF levels in the MSC culture medium were measured by enzyme-linked immunosorbent assay (ELISA). Rats with ARDS induced by lipopolysaccharide received MSC infusion via the tail vein. After 1, 6, and 24 h, rats were sacrificed. MSC retention in the lung was assessed by immunohistochemical assay. The lung wet weight to body weight ratio (LWW/BW) and Evans blue dye extravasation were obtained to reflect lung permeability. The VE-cadherin was detected with inmmunofluorescence, and the lung endothelial cell apoptosis was assessed by TUNEL assay. The severity of lung injury was evaluated using histopathology. The cytokines and HGF levels in the lung were measured by ELISA.

RESULTS

MSC-ShHGF with markedly lower HGF expression were successfully constructed. Treatment with MSC or MSC carrying green fluorescent protein (MSC-GFP) maintained HGF expression at relatively high levels in the lung at 24 h. MSC or MSC-GFP decreased the LWW/BW and the Evans Blue Dye extravasation, protected adherens junction VE-cadherin, and reduced the lung endothelial cell apoptosis. Furthermore, MSC or MSC-GFP reduced the inflammation and alleviated lung injury based on histopathology. However, HGF gene knockdown significantly decreased the HGF levels without any changes in the MSC retention in the lung, and diminished the protective effects of MSC on the injured lung, indicating the therapeutic effects of MSC on ARDS were partly associated with the HGF-expressing character of MSC.

CONCLUSIONS

MSC restores lung permeability and lung injury in part by maintaining HGF levels in the lung and the HGF-expressing character is required for MSC to protect the injured lung.

Alveolar derecruitment and collapse induration as crucial mechanisms in lung injury and fibrosis

Idiopathic pulmonary fibrosis (IPF) and bleomycin-induced pulmonary fibrosis are associated with surfactant system dysfunction, alveolar collapse (derecruitment), and collapse induration (irreversible collapse). These events play undefined roles in the loss of lung function. The purpose of this study was to quantify how surfactant inactivation, alveolar collapse, and collapse induration lead to degradation of lung function. Design-based stereology and invasive pulmonary function tests were performed 1, 3, 7, and 14 days after intratracheal bleomycin-instillation in rats. The number and size of open alveoli was correlated to mechanical properties. Active surfactant subtypes declined by Day 1, associated with a progressive alveolar derecruitment and a decrease in compliance. Alveolar epithelial damage was more pronounced in closed alveoli compared with ventilated alveoli. Collapse induration occurred on Day 7 and Day 14 as indicated by collapsed alveoli overgrown by a hyperplastic alveolar epithelium. This pathophysiology was also observed for the first time in human IPF lung explants. Before the onset of collapse induration, distal airspaces were easily recruited, and lung elastance could be kept low after recruitment by positive end-expiratory pressure (PEEP). At later time points, the recruitable fraction of the lung was reduced by collapse induration, causing elastance to be elevated at high levels of PEEP. Surfactant inactivation leading to alveolar collapse and subsequent collapse induration might be the primary pathway for the loss of alveoli in this animal model. Loss of alveoli is highly correlated with the degradation of lung function. Our ultrastructural observations suggest that collapse induration is important in human IPF.

Respiratory Tissue Engineering: Current Status and Opportunities for the Future

Currently, lung disease and major airway trauma constitute a major global healthcare burden with limited treatment options. Airway diseases such as chronic obstructive pulmonary disease and cystic fibrosis have been identified as the fifth highest cause of mortality worldwide and are estimated to rise to fourth place by 2030. Alternate approaches and therapeutic modalities are urgently needed to improve clinical outcomes for chronic lung disease. This can be achieved through tissue engineering of the respiratory tract. Interest is growing in the use of airway tissue-engineered constructs as both a research tool, to further our understanding of airway pathology, validate new drugs, and pave the way for novel drug therapies, and also as regenerative medical devices or as an alternative to transplant tissue. This review provides a concise summary of the field of respiratory tissue engineering to date. An initial overview of airway anatomy and physiology is given, followed by a description of the stem cell populations and signaling processes involved in parenchymal healing and tissue repair. We then focus on the different biomaterials and tissue-engineered systems employed in upper and lower respiratory tract engineering and give a final perspective of the opportunities and challenges facing the field of respiratory tissue engineering.

Electroporation-mediated gene delivery

Electroporation has been used extensively to transfer DNA to bacteria, yeast, and mammalian cells in culture for the past 30 years. Over this time, numerous advances have been made, from using fields to facilitate cell fusion, delivery of chemotherapeutic drugs to cells and tissues, and most importantly, gene and drug delivery in living tissues from rodents to man. Electroporation uses electrical fields to transiently destabilize the membrane allowing the entry of normally impermeable macromolecules into the cytoplasm. Surprisingly, at the appropriate field strengths, the application of these fields to tissues results in little, if any, damage or trauma. Indeed, electroporation has even been used successfully in human trials for gene delivery for the treatment of tumors and for vaccine development. Electroporation can lead to between 100 and 1000-fold increases in gene delivery and expression and can also increase both the distribution of cells taking up and expressing the DNA as well as the absolute amount of gene product per cell (likely due to increased delivery of plasmids into each cell). Effective electroporation depends on electric field parameters, electrode design, the tissues and cells being targeted, and the plasmids that are being transferred themselves. Most importantly, there is no single combination of these variables that leads to greatest efficacy in every situation; optimization is required in every new setting. Electroporation-mediated in vivo gene delivery has proven highly effective in vaccine production, transgene expression, enzyme replacement, and control of a variety of cancers. Almost any tissue can be targeted with electroporation, including muscle, skin, heart, liver, lung, and vasculature. This chapter will provide an overview of the theory of electroporation for the delivery of DNA both in individual cells and in tissues and its application for in vivo gene delivery in a number of animal models.

The secretome of induced pluripotent stem cells reduces lung fibrosis in part by hepatocyte growth factor

Introduction

Idiopathic pulmonary fibrosis (IPF) is a progressive and irreversible fibrotic lung disease, resulting in respiratory insufficiency and reduced survival. Pulmonary fibrosis is a result of repeated alveolar epithelial microinjuries, followed by abnormal regeneration and repair processes in the lung. Recently, stem cells and their secretome have been investigated as a novel therapeutic approach in pulmonary fibrosis. We evaluated the potential of induced pluripotent stem cells (iPSC) conditioned media (iPSC-cm) to regenerate and repair the alveolar epithelium in vitro and improve bleomycin induced lung injury in vivo.

Methods

IPSC-cm was collected from cultured iPSC derived from human foreskin fibroblasts and its biological effects on alveolar epithelial wound repair was studied in an alveolar wound healing assay in vitro. Furthermore, iPSC-cm was intratracheally instilled 7 days after bleomycin induced injury in the rat lungs and histologically and biochemically assessed 7 days after instillation.

Results

iPSC-cm increased alveolar epithelial wound repair in vitro compared with medium control. Intratracheal instillation of iPSC-cm in bleomycin-injured lungs reduced the collagen content and improved lung fibrosis in the rat lung in vivo. Profibrotic TGFbeta1 and α-smooth muscle actin (α-sma) expression were markedly reduced in the iPSC-cm treated group compared with control. Antifibrotic hepatocyte growth factor (HGF) was detected in iPSC-cm in biologically relevant levels, and specific inhibition of HGF in iPSC-cm attenuated the antifibrotic effect of iPSC-cm, indicating a central role of HGF in iPSC-cm.

Conclusion

iPSC-cm increased alveolar epithelial wound repair in vitro and attenuated bleomycin induced fibrosis in vivo, partially due to the presence of HGF and may represent a promising novel, cell free therapeutic option against lung injury and fibrosis.

Electronic supplementary material

The online version of this article (doi:10.1186/scrt513) contains supplementary material, which is available to authorized users.

Hepatocyte Growth Factor Isoforms in Tissue Repair, Cancer, and Fibrotic Remodeling

Hepatocyte growth factor (HGF), also known as scatter factor (SF), is a pleotropic factor required for normal organ development during embryogenesis. In the adult, basal expression of HGF maintains tissue homeostasis and is up-regulated in response to tissue injury. HGF expression is necessary for the proliferation, migration, and survival of epithelial and endothelial cells involved in tissue repair in a variety of organs, including heart, lung, kidney, liver, brain, and skin. The administration of full length HGF, either as a protein or using exogenous expression methodologies, increases tissue repair in animal models of tissue injury and increases angiogenesis. Full length HGF is comprised of an N-terminal hairpin turn, four kringle domains, and a serine protease-like domain. Several naturally occurring alternatively spliced isoforms of HGF were also identified. The NK1 variant contains the N-terminal hairpin and the first kringle domain, and the NK2 variant extends through the second kringle domain. These alternatively spliced forms of HGF activate the same receptor, MET, but they differ from the full length protein in their cellular activities and their biological functions. Here, we review the species-specific expression of the HGF isoforms, their regulation, the signal transduction pathways they activate, and their biological activities.

Time-dependent and somatically acquired mitochondrial DNA mutagenesis and respiratory chain dysfunction in a scleroderma model of lung fibrosis

Reactive oxygen species (ROS) have been implemented in the etiology of pulmonary fibrosis (PF) in systemic sclerosis. In the bleomycin model, we evaluated the role of acquired mutations in mitochondrial DNA (mtDNA) and respiratory chain defects as a trigger of ROS formation and fibrogenesis. Adult male Wistar rats received a single intratracheal instillation of bleomycin and their lungs were examined at different time points. Ashcroft scores, collagen and TGFβ1 levels documented a delayed onset of PF by day 14. In contrast, increased malon dialdehyde as a marker of ROS formation was detectable as early as 24 hours after bleomycin instillation and continued to increase. At day 7, lung tissue acquired significant amounts of mtDNA deletions, translating into a significant dysfunction of mtDNA-encoded, but not nucleus-encoded respiratory chain subunits. mtDNA deletions and markers of mtDNA-encoded respiratory chain dysfunction significantly correlated with pulmonary TGFβ1 concentrations and predicted PF in a multivariate model.

Hepatocyte growth factor regulates the TGF-β1-induced proliferation, differentiation and secretory function of cardiac fibroblasts

Cardiac fibroblast (CF) proliferation and transformation into myofibroblasts play important roles in cardiac fibrosis during pathological myocardial remodeling. In this study, we demonstrate that hepatocyte growth factor (HGF), an antifibrotic factor in the process of pulmonary, renal and liver fibrosis, is a negative regulator of cardiac fibroblast transformation in response to transforming growth factor-β₁ (TGF-β₁). HGF expression levels were significantly reduced in the CFs following treatment with 5 ng/ml TGF-β₁ for 48 h. The overexpression of HGF suppressed the proliferation, transformation and the secretory function of the CFs following treatment with TGF-β₁, as indicated by the attenuated expression levels of α-smooth muscle actin (α-SMA) and collagen I and III, whereas the knockdown of HGF had the opposite effect. Mechanistically, we identified that the phosphorylation of c-Met, Akt and total protein of TGIF was significantly inhibited by the knockdown of HGF, but was significantly enhanced by HGF overexpression. Collectively, these results indicate that HGF activates the c-Met-Akt-TGIF signaling pathway, inhibiting CF proliferation and transformation in response to TGF-β₁ stimulation.

TGF-β1 as a therapeutic target for pulmonary fibrosis and COPD

TGF-β1 is a multifunctional molecule that is expressed in an exaggerated fashion during injury, inflammation and repair. Its expression is dysregulated in lung tissues from patients with pulmonary fibrosis and chronic obstructive pulmonary disease. In animal models, introduction of TGF-β1 expression in the lung causes prominent tissue fibrosis and alveolar destruction. On the other hand, the exaggerated production of TGF-β1, an inability to activate TGF-β1 or a block in TGF-β1 signaling have all been associated with the development of emphysematous pulmonary lesions. A number of studies have demonstrated that TGF-β1 is a major player in the pathogenesis of pulmonary fibrosis and emphysema. In this review, we discuss how TGF-β1 expression is regulated and mechanistically related to the development of tissue fibrosis and emphysema in experimental animal models and humans. We further highlight potential therapeutic options that control TGF-β1-associated genes or signals to restore extracellular matrix homeostasis in which TGF-β1 plays a central role.

Electroporation-mediated gene delivery to the lungs

Electroporation is a safe, efficient, and inexpensive method to transfer naked plasmid DNA into various tissues. For electroporation-mediated gene transfer to the mouse lung, a plasmid solution is delivered to the lungs via the trachea. Immediately after plasmid delivery, eight square wave pulses are delivered by two pre-gelled electrodes placed on each side of the chest. An optimal field strength in mice is 200 V/cm, with a pulse duration of 10 ms each and a 1 s interval between pulses. High level gene expression can be achieved within 24 h in all cell types in the lung with very little inflammation and no apparent trauma.

Evaluating the Ameliorative Potential of Quercetin against the Bleomycin-Induced Pulmonary Fibrosis in Wistar Rats

The current study deals with the effect of a dietary flavanoid quercetin on fibrotic lung tissue in rats. Bleomycin was administered by single intratracheal instillation to Wistar rats to induce lung fibrosis. The pathologies associated with this included significantly reduced antioxidant capacity, ultimately leading to protracted inflammation of the lung tissue. The hallmark of this induced fibrosis condition was an excessive collagen deposition in peribronchial and perialveolar regions of the lung. Oral quercetin treatment over a period of twenty days resulted in significant reversal of the pathologies. The antioxidant defense in lung tissue was revived. Moreover, activity of the collagenase MMP-7, which was high in fibrotic tissue, was seen restored after quercetin administration. Trichome staining of lung tissue sections showed high collagen deposition in fibrotic rats, which may be a direct result of increased mobilization of collagen by MMP-7. This was appreciably reduced in quercetin treated animals. These results point towards an important protective role of quercetin against idiopathic lung fibrosis, which remains a widely prevalent yet incurable condition in the present times.

Evaluating the inhibitory potential of sulindac against the bleomycin-induced pulmonary fibrosis in wistar rats

The present study examined the protective effect of sulindac on bleomycin-induced lung fibrosis in rats. Animals were divided into saline group, bleomycin group (single intra-tracheal instillation of bleomycin) and bleomycin+sulindac (orally from day 1 to day 20). Bleomycin administration reduced the body weight, altered antioxidant status (such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione) while it increased the lung weight, hydroxyproline content, collagen deposition and lipid peroxidation. However, simultaneous administration of sulindac improved the body weight, antioxidant status and decreased the collagen deposition in lungs. Moreover, the levels of inflammatory cytokine tumour necrosis factor-α increased in bleomycin-induced group, whereas, on treatment with sulindac the levels of tumour necrosis factor-α were found reduced. Finally, histological evidence also supported the ability of sulindac to inhibit bleomycin-induced lung fibrosis. The results of the present study indicate that sulindac can be used as an agent against bleomycin-induced pulmonary fibrosis.

Hepatocyte growth factor is an attractive target for the treatment of pulmonary fibrosis

INTRODUCTION

Pulmonary fibrosis (PF) is a progressive fatal disorder and is characterized by alveolar epithelial injury, myofibroblast proliferation, and extracellular matrix remodeling, resulting in irreversible distortion of lung's architecture. Available therapies are associated with side effects and show restricted efficacy. Therefore, there is an urgent need to find a therapeutic solution to PF. Therapeutic strategies interfering myofibroblast expansion, apoptosis of epithelial and endothelial cells might be beneficial for treatment of PF. Hepatocyte growth factor (HGF), a pleiotropic growth factor, plays an important role in lung development, inflammation, repair, and regeneration. In animal model of PF, administration of recombinant HGF protein or ectopic HGF expression ameliorates fibrosis.

AREAS COVERED

The focus of this review is to highlight HGF as a promising therapeutic approach for the treatment of PF. The review discusses the currently available treatment option for PF as well as highlights the possible beneficial effect of HGF as a drug target.

EXPERT OPINION

HGF with its anti-fibrotic effect provides a promising new therapeutic approach by protecting lung from fibrotic remodeling and also promoting normal regeneration of lung. The development of HGF mimetics may provide a potential attractive therapy for treatment of this devastating and complex disease.

An approach towards bronchoscopic-based gene therapy using electrical field accelerated plasmid droplets

Idiopathic pulmonary fibrosis (IPF) is a devastating disease affecting the distal lung, due to failure of the alveolar epithelium to heal after micro-injuries, leading to inefficient gas exchange and resulting in death. Therapeutic options are very limited. A new therapeutic approach based on gene therapy restores the self-healing process within the lung in the experimental setup. A basic requirement of this therapy is the successful transduction of genes into the alveolar epithelium in the distal part of the lung, for which a new therapeutic instrument is required. In this paper we present the concept and first experimental results of a device which uses an electrical field to accelerate the charged droplets of plasmid suspension toward the tissue and which overcomes cell membrane with its impact energy. The aim is to develop a therapeutic device capable of being integrated into minimally invasive procedures such as bronchoscopy.

Targeted gene transfer of hepatocyte growth factor to alveolar type II epithelial cells reduces lung fibrosis in rats

Inefficient alveolar wound repair contributes to the development of pulmonary fibrosis. Hepatocyte growth factor (HGF) is a potent growth factor for alveolar type II epithelial cells (AECII) and may improve repair and reduce fibrosis. We studied whether targeted gene transfer of HGF specifically to AECII improves lung fibrosis in bleomycin-induced lung fibrosis. A plasmid encoding human HGF expressed from the human surfactant protein C promoter (pSpC-hHGF) was designed, and extracorporeal electroporation-mediated gene transfer of HGF specifically to AECII was performed 7 days after bleomycin-induced lung injury in the rat. Animals were killed 7 days after hHGF gene transfer. Electroporation-mediated HGF gene transfer resulted in HGF expression specifically in AECII at biologically relevant levels. HGF gene transfer reduced pulmonary fibrosis as assessed by histology, hydroxyproline determination, and design-based stereology compared with controls. Our results indicate that the antifibrotic effect of HGF is due in part to a reduction of transforming growth factor-β(1), modulation of the epithelial-mesenchymal transition, and reduction of extravascular fibrin deposition. We conclude that targeted HGF gene transfer specifically to AECII decreases bleomycin-induced lung fibrosis and may therefore represent a novel cell-specific gene transfer technology to treat pulmonary fibrosis.

HGF Expressing Stem Cells in Usual Interstitial Pneumonia Originate from the Bone Marrow and Are Antifibrotic

Background

Pulmonary fibrosis may result from abnormal alveolar wound repair after injury. Hepatocyte growth factor (HGF) improves alveolar epithelial wound repair in the lung. Stem cells were shown to play a major role in lung injury, repair and fibrosis. We studied the presence, origin and antifibrotic properties of HGF-expressing stem cells in usual interstitial pneumonia.

Methods

Immunohistochemistry was performed in lung tissue sections and primary alveolar epithelial cells obtained from patients with usual interstitial pneumonia (UIP, n = 7). Bone marrow derived stromal cells (BMSC) from adult male rats were transfected with HGF, instilled intratracheally into bleomycin injured rat lungs and analyzed 7 and 14 days later.

Results

In UIP, HGF was expressed in specific cells mainly located in fibrotic areas close to the hyperplastic alveolar epithelium. HGF-positive cells showed strong co-staining for the mesenchymal stem cell markers CD44, CD29, CD105 and CD90, indicating stem cell origin. HGF-positive cells also co-stained for CXCR4 (HGF+/CXCR4+) indicating that they originate from the bone marrow. The stem cell characteristics were confirmed in HGF secreting cells isolated from UIP lung biopsies. In vivo experiments showed that HGF-expressing BMSC attenuated bleomycin induced pulmonary fibrosis in the rat, indicating a beneficial role of bone marrow derived, HGF secreting stem cells in lung fibrosis.

Conclusions

HGF-positive stem cells are present in human fibrotic lung tissue (UIP) and originate from the bone marrow. Since HGF-transfected BMSC reduce bleomycin induced lung fibrosis in the bleomycin lung injury and fibrosis model, we assume that HGF-expressing, bone-marrow derived stem cells in UIP have antifibrotic properties.

Hepatocyte growth factor, a determinant of airspace homeostasis in the murine lung

The alveolar compartment, the fundamental gas exchange unit in the lung, is critical for tissue oxygenation and viability. We explored hepatocyte growth factor (HGF), a pleiotrophic cytokine that promotes epithelial proliferation, morphogenesis, migration, and resistance to apoptosis, as a candidate mediator of alveolar formation and regeneration. Mice deficient in the expression of the HGF receptor Met in lung epithelial cells demonstrated impaired airspace formation marked by a reduction in alveolar epithelial cell abundance and survival, truncation of the pulmonary vascular bed, and enhanced oxidative stress. Administration of recombinant HGF to tight-skin mice, an established genetic emphysema model, attenuated airspace enlargement and reduced oxidative stress. Repair in the TSK/+ mouse was punctuated by enhanced akt and stat3 activation. HGF treatment of an alveolar epithelial cell line not only induced proliferation and scattering of the cells but also conferred protection against staurosporine-induced apoptosis, properties critical for alveolar septation. HGF promoted cell survival was attenuated by akt inhibition. Primary alveolar epithelial cells treated with HGF showed improved survival and enhanced antioxidant production. In conclusion, using both loss-of-function and gain-of-function maneuvers, we show that HGF signaling is necessary for alveolar homeostasis in the developing lung and that augmentation of HGF signaling can improve airspace morphology in murine emphysema. Our studies converge on prosurvival signaling and antioxidant protection as critical pathways in HGF–mediated airspace maintenance or repair. These findings support the exploration of HGF signaling enhancement for diseases of the airspace.

The airspace compartment of the mammalian lung, comprised of spherical sacs termed alveoli, harbors the architecture, cellular composition, and molecular armamentarium to perform the critical function of gas exchange or oxygen uptake. Despite the necessity of this alveolar compartment for organismal viability, the mechanism by which alveoli are formed and maintained is obscure. Furthermore, no treatments are currently available that can regenerate the airspace once damaged. In this manuscript, we sought to determine whether hepatocyte growth factor, a cytokine with a functional armamentarium that subserves the critical events of alveolar formation (epithelial proliferation, migration, resistance from apoptosis and angiogenesis), could be an important mediator of alveolar formation and airspace maintenance. Our simple paradigm was that critical homeostatic pathways for the lung should operate both in lung formation and in lung maintenance/regeneration. Using an informative battery of mouse models and cell lines, we show that hepatocyte growth factor is a determinant of alveolar formation and that the enhancement of hepatocyte growth factor signaling can both protect and repair the airspace from pathologic airspace enlargement or emphysema.

Hepatocyte growth factor and lung fibrosis

Idiopathic pulmonary fibrosis is currently believed to be driven by alveolar epithelial cells, with abnormally activated alveolar epithelial cells accumulating in an attempt to repair injured alveolar epithelium (1). Thus, targeting the alveolar epithelium to prevent or inhibit the development of pulmonary fibrosis might be an interesting therapeutic option in this disease. Hepatocyte growth factor (HGF) is a growth factor for epithelial and endothelial cells, which is secreted by different cell types, especially fibroblasts and neutrophils. HGF has mitogenic, motogenic, and morphogenic properties and exerts an antiapoptotic action on epithelial and endothelial cells. HGF has also proangiogenic effect. In vitro, HGF inhibits epithelial-to-mesenchymal cell transition and promotes myofibroblast apoptosis. In vivo, HGF has antifibrotic properties demonstrated in experimental models of lung, kidney, heart, skin, and liver fibrosis. Hence, the modulation of HGF may be an attractive target for the treatment of lung fibrosis.

Cell-specific expression of human HGF by alveolar type II cells induces remodeling of septal wall tissue in the lung: a morphometric study

Hepatocyte growth factor (HGF) is involved in development and regeneration of the lungs. Human HGF, which was expressed specifically by alveolar epithelial type II cells after gene transfer, attenuated the bleomycin-induced pulmonary fibrosis in an animal model. As there are also regions that appear morphologically unaffected in fibrosis, the effects of this gene transfer to normal lungs is of interest. In vitro studies showed that HGF inhibits the formation of the basal lamina by cultured alveolar epithelial cells. Thus we hypothesized that, in the healthy lung, cell-specific expression of HGF induces a remodeling within septal walls. Electroporation of a plasmid of human HGF gene controlled by the surfactant protein C promoter was applied for targeted gene transfer. Using design-based stereology at light and electron microscopic level, structural alterations were analyzed and compared with a control group. HGF gene transfer increased the volume of distal air spaces, as well as the surface area of the alveolar epithelium. The volume of septal walls, as well as the number of alveoli, was unchanged. Volumes per lung of collagen and elastic fibers were unaltered, but a marked reduction of the volume of residual extracellular matrix (all components other than collagen and elastic fibers) and interstitial cells was found. A correlation between the volumes of residual extracellular matrix and distal air spaces, as well as total surface area of alveolar epithelium, could be established. Cell-specific expression of HGF leads to a remodeling of the connective tissue within the septal walls in the healthy lung, which is associated with more pronounced stretching of distal air spaces at a given hydrostatic pressure during instillation fixation.

Mesenchymal stromal cells from neonatal tracheal aspirates demonstrate a pattern of lung-specific gene expression

We have previously isolated mesenchymal stromal cells (MSCs) from the tracheal aspirates of premature neonates with respiratory distress. Although isolation of MSCs correlates with the development of bronchopulmonary dysplasia, the physiologic role of these cells remains unclear. To address this, we further characterized the cells, focusing on the issues of gene expression, origin, and cytokine expression. Microarray comparison of early passage neonatal lung MSC gene expression to cord blood MSCs and human fetal and neonatal lung fibroblast lines demonstrated that the neonatal lung MSCs differentially expressed 971 gene probes compared with cord blood MSCs, including the transcription factors Tbx2, Tbx3, Wnt5a, FoxF1, and Gli2, each of which has been associated with lung development. Compared with lung fibroblasts, 710 gene probe transcripts were differentially expressed by the lung MSCs, including IL-6 and IL-8/CXCL8. Differential chemokine expression was confirmed by protein analysis. Further, neonatal lung MSCs exhibited a pattern of Hox gene expression distinct from cord blood MSCs but similar to human fetal lung fibroblasts, consistent with a lung origin. On the other hand, limiting dilution analysis showed that fetal lung fibroblasts form colonies at a significantly lower rate than MSCs, and fibroblasts failed to undergo differentiation along adipogenic, osteogenic, and chondrogenic lineages. In conclusion, MSCs isolated from neonatal tracheal aspirates demonstrate a pattern of lung-specific gene expression, are distinct from lung fibroblasts, and secrete pro-inflammatory cytokines.

Association of hepatocyte growth factor promoter polymorphism with severity of interstitial lung disease in Japanese patients with systemic sclerosis

OBJECTIVE

To examine associations of single-nucleotide polymorphisms (SNPs) within genes for hepatocyte growth factor (HGF) and its receptor c-met with disease susceptibility and organ involvement in Japanese patients with systemic sclerosis (SSc).

METHODS

Four SNPs (HGF -1652 C/T, +44222 C/T, and +63555 G/T, and c-met -980 T/A) were analyzed in 159 SSc patients and 103 healthy control subjects with the use of a polymerase chain reaction-based assay. The influence of the HGF -1652 SNP on transcription activity was evaluated with a luciferase reporter assay and an electrophoretic mobility shift assay (EMSA).

RESULTS

There was no difference in the distribution of HGF/c-met SNPs between SSc patients and controls. HGF -1652 TT was found much more frequently in SSc patients with end-stage lung disease (ESLD) than in those without (41% versus 8%; P = 0.0004). This association was confirmed by a replication study involving a separate cohort of 155 SSc patients. Kaplan-Meyer analysis revealed that HGF -1652 TT carriers had a higher probability of developing ESLD than did CT or CC carriers. The HGF promoter carrying the HGF -1652 T allele had lower transcription activity than did the promoter carrying the C allele. EMSA showed the presence of a potential negative transcription regulator that binds specifically to the HGF promoter carrying a T allele at position -1652. Finally, TT carriers had a relative inability to increase circulating HGF levels even in the presence of advanced interstitial lung disease.

CONCLUSION

A SNP in the HGF promoter region may modulate the severity of interstitial lung disease by controlling the transcriptional efficiency of the HGF gene.

Prolonged amelioration of acute lung allograft rejection by sequential overexpression of human interleukin-10 and hepatocyte growth factor in rats

The effect of prolonged electroporation-mediated human interleukin-10 (hIL-10) overexpression 24 hours before transplantation, combined with sequential human hepatocyte growth factor (HGF) overexpression into skeletal muscle on day 5, on rat lung allograft rejection was evaluated. Left lung allotransplantation was performed from Brown-Norway to Fischer-F344 rats. Gene transfer into skeletal muscle was enhanced by electroporation. Three groups were studied: group I animals (n = 5) received 2.5 μg pCIK-hIL-10 (hIL-10/CMV [cytomegalovirus] early promoter enhancer) on day -1 and 80 μg pCIK-HGF (HGF/CMV early promoter enhancer) on day 5. Group II animals (n = 4) received 2.5 μg pCIK-hIL-10 and pUbC-hIL-10 (hIL-10/pUbC promoter) on day -1. Control group III animals (n = 4) were treated by sham electroporation on days -1 and 5. All animals received daily nontherapeutic intraperitoneal dose of cyclosporin A (2.5 mg/kg) and were sacrificed on day 15. Graft oxygenation and allograft rejection were evaluated. Significant differences were found between study groups in graft oxygenation (Pao(2)) (P = .0028; group I vs. groups II and III, P < .01 each). Pao(2) was low in group II (31 ± 1 mm Hg) and in group III controls (34 ± 10 mm Hg), without statistically significant difference between these 2 groups (P = .54). In contrast, in group I, Pao(2) of recipients sequentially transduced with IL-10 and HGF plasmids was much improved, with 112 ± 39 mm Hg (vs. groups II and III; P < .01 each), paralleled by reduced vascular and bronchial rejection (group I vs. groups II and III, P < .021 each). Sequential overexpression of anti-inflammatory cytokine IL-10, followed by sequential and overlapping HGF overexpression on day 5, preserves lung function and reduces acute lung allograft rejection up to day 15 post transplant as compared to prolonged IL-10 overexpression alone.

Therapeutic implications of mesenchymal stem cells transfected with hepatocyte growth factor transplanted in rat kidney with unilateral ureteral obstruction

PURPOSE

The purpose of the study was to establish whether bone marrow mesenchymal stem cells (MSCs) transfected with hepatocyte growth factor (HGF) can migrate and localize in the rat's kidney with unilateral ureteral obstruction (UUO) and contribute to repair of renal fibrosis.

METHODS

We separated and cultured bone marrow-derived MSCs of male rats in vitro and transfected them with adenovirus-mediated HGF (Ad-HGF). The expression of HGF was measured with enzyme-linked immunosorbent assay. Sixty female rats were sham operated (n = 24) or subjected to left UUO: Ad-HGF-transfected MSCs, uninfected MSCs, or saline was injected into the rat's tail vein. Kidney tissue was collected at the end of the seventh or 14th day after operation. The distribution of Y chromosome in the kidney after Ad-HGF-transfected MSCs transplantation was determined by an in situ hybridization method. As the hallmark of myofibroblasts, α-smooth muscle actin (expression of which significantly increases in the presence of renal fibrosis) was detected by immunohistochemistry in all UUO rats' left kidney tissue.

RESULTS

Y chromosome-positive cells were found only in the obstructed kidney of the transplantation group. The positive cells were mainly distributed in the tubular cells. The average intensity of immunolabeling for α-smooth muscle actin in the transplanted group significantly decreased compared with sham-transplanted group (P < .05), and the expression in the rats injected with uninfected MSCs was higher than that in the rats with MSCs transfected with HGF (P < .05).

CONCLUSIONS

Mesenchymal stem cells transfected with HGF can migrate to the rat kidney with UUO and are mainly distributed in the region of renal tubular epithelial cells. The data indicate that MSCs transfected with HGF contribute to a reduction of renal fibrosis after ureteral obstruction and suggest that this may be exploited therapeutically.

Hepatocyte growth factor in lung repair and pulmonary fibrosis

Pulmonary remodeling is characterized by the permanent and progressive loss of the normal alveolar architecture, especially the loss of alveolar epithelial and endothelial cells, persistent proliferation of activated fibroblasts, or myofibroblasts, and alteration of extracellular matrix. Hepatocyte growth factor (HGF) is a pleiotropic factor, which induces cellular motility, survival, proliferation, and morphogenesis, depending upon the cell type. In the adult, HGF has been demonstrated to play a critical role in tissue repair, including in the lung. Administration of HGF protein or ectopic expression of HGF has been demonstrated in animal models of pulmonary fibrosis to induce normal tissue repair and to prevent fibrotic remodeling. HGF-induced inhibition of fibrotic remodeling may occur via multiple direct and indirect mechanisms including the induction of cell survival and proliferation of pulmonary epithelial and endothelial cells, and the reduction of myofibroblast accumulation.