Therapeutic potential of growth factors in pulmonary emphysematous condition

Differential lung gene expression identified Zscan2 and Bag6 as novel tissue repair players in an experimental COPD model

Chronic obstructive pulmonary disease is a common chronic lung disease with an ever-increasing incidence. Despite years of drug research and approvals, we are still not able to halt progress or restore normal lung function. Our previous studies have demonstrated that liver growth factor-LGF has an effect on the repair of the affected tissue in a mouse model of cigarette smoke exposure, but by what pathways it achieves this is unknown. The present study aimed to identify differentially expressed genes between emphysematous mice treated with LGF to identify potential therapeutic targets for the treatment of pulmonary emphysema. The emphysema mouse model was induced by prolonged exposure to cigarette smoke. To determine the gene expression profile of the lung in smokers treated or not with LGF, lung messenger RNA gene expression was assessed with the Agilent Array platform. We carried out differentially expressed gene analysis, functional enrichment and validated in treated mouse lung samples. The treated group significantly improved lung function (~35%) and emphysema level (~20%), consistent with our previous published studies. Microarray analysis demonstrated 290 differentially expressed genes in total (2.0-fold over or lower expressed). Injury repair-associated genes and pathways were further enhanced in the lung of LGF treated mice. The expression trends of two genes (Zscan2 and Bag6) were different in emphysematous lungs treated with LGF compared to untreated lungs. Therefore, Zscan2 and Bag6 genes could play a role in regulating inflammation and the immune response in the lung that undergoes partial lung regeneration. However, further studies are necessary to demonstrate this causal relationship.

IL-1β Induces a Proinflammatory Fibroblast Microenvironment that Impairs Lung Progenitors' Function

Chronic obstructive pulmonary disease (COPD) is characterized by a persistent inflammatory state in the lungs and defective tissue repair. Although the inflammatory response in patients with COPD is well characterized and known to be exaggerated during exacerbations, its contribution to lung injury and abnormal repair is still unclear. In this study, we aimed to investigate how the inflammatory microenvironment affects the epithelial progenitors and their supporting mesenchymal niche cells involved in tissue repair of the distal lung. We focused on IL-1β, a key inflammatory mediator that is increased during exacerbations of COPD, and used an organoid model of lung epithelial cells and fibroblasts to assess the effect of IL-1β treatment on these cells' transcriptome and secreted factors. Whereas direct treatment of the lung organoids with IL-1β promoted organoid growth, this switched toward inhibition when it was added as fibroblast pretreatment followed by organoid treatment. We then investigated the IL-1β-driven mechanisms in the fibroblasts and found an inflammatory response related to (C-X-C motif) ligand (CXCL) chemokines; we confirmed that these chemokines were responsible for the impaired organoid growth and found that targeting their C-X-C chemokine receptors 1/2 (CXCR1/2) receptors or the IL-1β intracellular signaling reduced the proinflammatory response and restored organoid growth. These data demonstrate that IL-1β alters the fibroblasts' state by promoting a distinct inflammatory response, switching their supportive function on epithelial progenitors toward an inhibitory one in an organoid assay. These results imply that chronic inflammation functions as a shift toward inhibition of repair, thereby contributing to chronic inflammatory diseases like COPD.

Potential Therapeutic Strategy in Chronic Obstructive Pulmonary Disease Using Pioglitazone-Augmented Wharton's Jelly-Derived Mesenchymal Stem Cells

Background

A recent study reported that mesenchymal stem cells possess potential cellular therapeutic properties for treating patients with chronic obstructive pulmonary disease, which is characterized by emphysema. We examined the potential therapeutic effect of Wharton's Jelly-derived mesenchymal stem cells (WJMSCs), following pretreatment with pioglitazone, in lung regeneration mouse emphysema models.

Methods

We used two mouse emphysema models, an elastase-induced model and a cigarette smoke-induced model. We intravenously injected WJMSCs (1×10⁴/mouse) to mice, pretreated or not, with pioglitazone for 7 days. We measured the emphysema severity by mean linear intercepts (MLI) analysis using lung histology.

Results

Pioglitazone pretreated WJMSCs (pioWJMSCs) were associated with greater lung regeneration than non-augmented WJMSCs in the two mouse emphysema models. In the elastase-induced emphysema model, the MLIs were 59.02±2.42 µm (n=6), 72.80±2.87 µm (n=6), for pioWJMSCs injected mice, and non-augmented WJMSCs injected mice, respectively (p<0.01). Both pioWJMSCs and non-augmented WJMSCs showed regenerative effects in the cigarette smoke emphysema model (MLIs were 41.25±0.98 [n=6] for WJMSCs and38.97±0.61 µm [n=6] for pioWJMSCs) compared to smoking control mice (51.65±1.36 µm, n=6). The mean improvement of MLI appeared numerically better in pioWJMSCs than in non-augmented WJMSCs injected mice, but the difference did not reach the level of statistical significance (p=0.071).

Conclusion

PioWJMSCs may produce greater lung regeneration, compared to non-augmented WJMSCs, in a mouse emphysema model.

Therapeutic effects of adipose-derived stem cells pretreated with pioglitazone in an emphysema mouse model

There is no therapy currently available that influences the natural history of disease progression in patients with chronic obstructive pulmonary disease (COPD). Although stem cell therapy is considered a potential therapeutic option in COPD, there are no clinical trials proving definitive therapeutic effects in patients with COPD. Recently, it was reported that pioglitazone might potentiate the therapeutic effects of stem cells in patients with heart or liver disease. To test the capacity of pioglitazone pretreatment of stem cells for emphysema repair, we evaluated the therapeutic effects of pioglitazone-pretreated human adipose-derived mesenchymal stem cells (ASCs) on elastase-induced or cigarette smoke-induced emphysema in mice. We also investigated the mechanisms of action of pioglitazone-pretreated ASCs. Pioglitazone-pretreated ASCs had a more potent therapeutic effect than non-pretreated ASCs in the repair of both elastase-induced and smoke-induced emphysema models (mean linear intercept, 78.1±2.5 μm vs 83.2±2.6 μm in elastase models and 75.6±1.4 μm vs 80.5±3.2 μm in smoke models, P<0.05). Furthermore, we showed that pioglitazone-pretreated ASCs increased vascular endothelial growth factor (VEGF) production both in vitro and in mouse lungs in the smoke-induced emphysema model. Pioglitazone-pretreated ASCs may have more potent therapeutic effects than non-pretreated ASCs in emphysema mouse models.

The Therapeutic Effects of Optimal Dose of Mesenchymal Stem Cells in a Murine Model of an Elastase Induced-Emphysema

Background

Chronic obstructive pulmonary disease is characterized by emphysema, chronic bronchitis, and small airway remodeling. The alveolar destruction associated with emphysema cannot be repaired by current clinical practices. Stem cell therapy has been successfully used in animal models of cigarette smoke- and elastase-induced emphysema. However, the optimal dose of mesenchymal stem cells (MSCs) for the most effective therapy has not yet been determined. It is vital to determine the optimal dose of MSCs for clinical application in emphysema cases.

Methods

In the present study, we evaluated the therapeutic effects of various doses of MSCs on elastase-induced emphysema in mice. When 3 different doses of MSCs were intravenously injected into mice treated with elastase, only 5×10⁴ MSCs showed a significant effect on the emphysematous mouse lung. We also identified action mechanisms of MSCs based on apoptosis, lung regeneration, and protease/antiprotease imbalance.

Results

The MSCs were not related with caspase-3/7 dependent apoptosis. But activity of matrix metalloproteinase 9 increased by emphysematous lung was decreased by intravenously injected MSCs. Vascular endothelial growth factor were also increased in lung from MSC injected mice, as compared to un-injected mice.

Conclusion

This is the first study on the optimal dose of MSCs as a therapeutic candidate. This data may provide important basic data for determining dosage in clinical application of MSCs in emphysema patients.

Proliferative activity of liver growth factor is associated with an improvement of cigarette smoke-induced emphysema in mice

Cigarette smoke (CS)-induced emphysema is a major component of chronic obstructive pulmonary disease (COPD). COPD treatment is based on the administration of bronchodilators and corticosteroids to control symptoms and exacerbations, however, to date, there are no effective therapies to reverse disease progression. Liver growth factor (LGF) is an albumin-bilirubin complex with mitogenic properties, whose therapeutic effects have previously been reported in a model of emphysema and several rodent models of human disease. To approach the therapeutic effect of LGF in a model of previously established emphysema, morphometric and lung function parameters, matrix metalloproteinase (MMP) activity and the expression of several markers, such as VEGF, PCNA, 3NT and Nrf2, were assessed in air-exposed and CS-exposed C57BL/6J male mice with and without intraperitoneal (i.p.) injection of LGF. CS-exposed mice presented a significant enlargement of alveolar spaces, higher alveolar internal area and loss of lung function that correlated with higher MMP activity, higher expression of 3NT and lower expression of VEGF. CS-exposed mice injected with LGF, showed an amelioration of emphysema and improved lung function, which correlated with lower MMP activity and 3NT expression and higher levels of VEGF, PCNA and Nrf2. Taken together, this study suggests that LGF administration ameliorates CS-induced emphysema, highlights the ability of LGF to promote alveolar cell proliferation and may be a promising strategy to revert COPD progression.

Effect of recombinant human keratinocyte growth factor in inducing Ras-Raf-Erk pathway-mediated cell proliferation in emphysematous mice lung

CONTEXT

Pulmonary emphysema is resulted due to destruction of the structure of the alveoli. Recently, exogenous recombinant human Keratinocyte growth factor (rHuKGF) has been reported to induce the regeneration of gas exchange structures. However, the molecular mechanisms governing this process are so far unknown.

OBJECTIVE

The objective of this study was to investigate the effect of rHuKGF in the lungs of emphysema-challenged mice on Ras-Raf-Erk (Erk, extracellular signal-regulated kinase) mediated signaling pathway that regulates alveolar epithelial cell proliferation.

METHODS

Three experimental groups (i.e. emphysema, therapy and control group) were prepared. Lungs of mice were therapeutically treated at three occasions by oropharyngeal instillation of 10 mg rHuKGF per kg body weight after induction of emphysema by porcine pancreatic elastase (PPE). Subsequently, lung tissues from each mouse were collected for histopathology and molecular biology studies.

RESULTS AND DISCUSSION

Histopathology photomicrographs and Destructive Index analysis have shown that elastase induced airspace enlargement and loss of alveoli were recovered in therapy group. Moreover, proliferating cell nuclear antigen (PCNA) at mRNA and protein expression level was markedly increased in therapy group than emphysema group. Upon validation at mRNA level, expressions of FGF-7, FGF-R, Ras, c-Raf, Erk-1, Erk-2, c-Myc and were significantly increased, whereas Elk-1 was notably decreased in therapy group when compared with emphysema group and were well comparable with the control group.

CONCLUSION

Therapeutic supplementation of rHuKGF rectifies the deregulated Ras-Raf-Erk pathway in emphysema condition, resulting in alveolar epithelium regeneration. Hence, rHuKGF may prove to be a potential drug in the treatment of emphysema.

Animal models of chronic obstructive pulmonary disease

Animal models of disease have always been welcomed by the scientific community because they provide an approach to the investigation of certain aspects of the disease in question. Animal models of COPD cannot reproduce the heterogeneity of the disease and usually only manage to represent the disease in its milder stages. Moreover, airflow obstruction, the variable that determines patient diagnosis, not always taken into account in the models. For this reason, models have focused on the development of emphysema, easily detectable by lung morphometry, and have disregarded other components of the disease, such as airway injury or associated vascular changes. Continuous, long-term exposure to cigarette smoke is considered the main risk factor for this disease, justifying the fact that the cigarette smoke exposure model is the most widely used. Some variations on this basic model, related to exposure time, the association of other inducers or inhibitors, exacerbations or the use of transgenic animals to facilitate the identification of pathogenic pathways have been developed. Some variations or heterogeneity of this disease, then, can be reproduced and models can be designed for resolving researchers' questions on disease identification or treatment responses.