Interrupted reprogramming of alveolar type II cells induces progenitor-like cells that ameliorate pulmonary fibrosis

Engraftment of wild-type alveolar type II epithelial cells in surfactant protein C deficient mice

Childhood interstitial lung disease (chILD) secondary to pulmonary surfactant deficiency is a devastating chronic lung disease in children. Clinical presentation includes mild to severe respiratory failure and fibrosis. There is no specific treatment, except lung transplantation, which is hampered by a severe shortage of donor organs, especially for young patients. Repair of lungs with chILD represents a longstanding therapeutic challenge but cell therapy is a promising strategy. As surfactant is produced by alveolar type II epithelial (ATII) cells, engraftment with normal or gene-corrected ATII cells might provide an avenue to cure. Here we used a chILD disease-like model, Sftpc -/- mice, to provide proof-of-principle for this approach. Sftpc -/- mice developed chronic interstitial lung disease with age and were hypersensitive to bleomycin. We could engraft wild-type ATII cells after low dose bleomycin conditioning. Transplanted ATII cells produced mature SPC and attenuated bleomycin-induced lung injury up to two months post-transplant. This study demonstrates that partial replacement of mutant ATII cells can promote lung repair in a mouse model of chILD-like disease.

Enzyme-like nanoparticle-engineered mesenchymal stem cell secreting HGF promotes visualized therapy for idiopathic pulmonary fibrosis in vivo

Stem cell therapy is being explored as a potential treatment for idiopathic pulmonary fibrosis (IPF), but its effectiveness is hindered by factors like reactive oxygen species (ROS) and inflammation in fibrotic lungs. Moreover, the distribution, migration, and survival of transplanted stem cells are still unclear, impeding the clinical advancement of stem cell therapy. To tackle these challenges, we fabricate AuPtCoPS trimetallic-based nanocarriers (TBNCs), with enzyme-like activity and plasmid loading capabilities, aiming to efficiently eradicate ROS, facilitate delivery of therapeutic genes, and ultimately improve the therapeutic efficacy. TBNCs also function as a computed tomography contrast agent for tracking mesenchymal stem cells (MSCs) during therapy. Accordingly, we enhanced the antioxidant stress and anti-inflammatory capabilities of engineered MSCs and successfully visualized their biological behavior in IPF mice in vivo. Overall, this study provides an efficient and forward-looking treatment approach for IPF and establishes a framework for a stem cell-based therapeutic system aimed at addressing lung disease.

The occurrence and development of induced pluripotent stem cells

The ectopic expression of four transcription factors, Oct3/4, Sox2, Klf4, and c-Myc (OSKM), known as "Yamanaka factors," can reprogram or stimulate the production of induced pluripotent stem cells (iPSCs). Although OSKM is still the gold standard, there are multiple ways to reprogram cells into iPSCs. In recent years, significant progress has been made in improving the efficiency of this technology. Ten years after the first report was published, human pluripotent stem cells have gradually been applied in clinical settings, including disease modeling, cell therapy, new drug development, and cell derivation. Here, we provide a review of the discovery of iPSCs and their applications in disease and development.

Mesenchymal cells support the early retention of primary alveolar type 2 cells on acellular mouse lung scaffolds

Objectives

Tissue engineering approaches via repopulation of acellular biological grafts provide an exciting opportunity to generate lung grafts for transplantation. Alveolar type 2 (AT2) cells are a promising cell source for re-epithelialization. There are however inherent limitations with respect to their survival and growth, thus impeding their usability for tissue engineering applications. This study investigates the use of mesenchymal stromal cells to support primary AT2 cells for recellularization of mouse lung scaffolds.

Methods

AT2 cells and bone marrow-derived mesenchymal cells (BMC) were co-delivered to decellularized mouse lung scaffolds. Recellularized lungs were evaluated for cell surface coverage, viability, and differentiation at 1 and 4 days after cell seeding. Recellularization was evaluated via histological analysis and immunofluorescence.

Results

Simultaneous delivery of AT2 and BMC into acellular lung scaffolds resulted in enhanced cell surface coverage and reduced AT2 cell apoptosis in the recellularized scaffolds at Day 1 but not Day 4. AT2 cell number decreased after 4 days in both of AT2 only and codelivery groups suggesting limited expansion potential in the scaffold. After retention in the scaffold, AT2 cells differentiated into Aqp5-expressing cells.

Conclusions

Our results indicate that BMC support AT2 cell survival during the initial attachment and engraftment phase of recellularization. While our findings suggest only a short-term beneficial effect of BMC, our study demonstrates that AT2 cells can be delivered and retained in acellular lung scaffolds; thus with preconditioning and supporting cells, may be used for re-epithelialization. Selection and characterization of appropriate cell sources for use in recellularization, will be critical for ultimate clinical application.

Protein lysine acetylation played an important role in NH3-induced AEC2 damage and pulmonary fibrosis in piglets

Gaseous ammonia (NH3), as a main air pollutant in pig farms and surrounding areas, directly affects animal and human health. The lung, as an important organ for gas exchange in the respiratory system, is damaged after NH3 exposure, but the underlying mechanism needs to be further explored. In this study, seven weeks old piglets were exposed to 50 ppm NH3 for 30 days, and displayed pulmonary fibrosis. Then, the toxicological mechanism of NH3-induced pulmonary fibrosis was explored from the aspects of whole genome wide protein expression and post-translational modification. Totally, 404 differentially expressed proteins (DEPs) and 136 differentially lysine acetylated proteins (DAPs) were identified. The expression or lysine acetylation levels of proteins involved in mitochondrial energy metabolism including fatty acid oxidation (CPT1A, ACADVL, ACADS, HADHA, and HADHB), TCA cycle (IDH2 and MDH2), and oxidative phosphorylation (NDUFB7, NDUFV1, ATP5PB, ATP5F1A, COX5A, and COX5B) were significantly changed after NH3 exposure, which suggested that NH3 disrupted mitochondrial energy metabolism in the lung of piglets. Next, we found that type 2 alveolar epithelial cells (AEC2) damaged after NH3 exposure in vivo and in vitro. Integrin-linked kinase (ILK) was enriched in focal adhesion pathway, and showed significantly up-regulated acetylation levels at K191 (FC = 2.99) and K209 sites (FC = 1.52) after NH3 exposure. We illustrated that ILK-K191 hyper-acetylation inhibited AEC2 proliferation and induced AEC2 apoptosis by down-regulating pAKT-S473 in vitro. In conclusion, for the first time, our study revealed that protein acetylation played an important role in the process of NH3-induced pulmonary fibrosis in piglets. Our findings provided valuable insights into toxicological harm of NH3 to human health.

Epithelial cells/progenitor cells in developing human lower respiratory tract: Characterization and transplantation to rat model of pulmonary injury

Introduction

For cell-based therapies of lung injury, several cell sources have been extensively studied. However, the potential of human fetal respiratory cells has not been systematically explored for this purpose. Here, we hypothesize that these cells could be one of the top sources and hence, we extensively updated the definition of their phenotype.

Methods

Human fetal lower respiratory tissues from pseudoglandular and canalicular stages and their isolated epithelial cells were evaluated by immunostaining, electron microscopy, flow cytometry, organoid assay, and gene expression studies. The regenerative potential of the isolated cells has been evaluated in a rat model of bleomycin-induced pulmonary injury by tracheal instillation on days 0 and 14 after injury and harvest of the lungs on day 28.

Results

We determined the relative and temporal, and spatial pattern of expression of markers of basal (KRT5, KRT14, TRP63), non-basal (AQP3 and pro-SFTPC), and early progenitor (NKX2.1, SOX2, SOX9) cells. Also, we showed the potential of respiratory-derived cells to contribute to in vitro formation of alveolar and airway-like structures in organoids. Cell therapy decreased fibrosis formation in rat lungs and improved the alveolar structures. It also upregulated the expression of IL-10 (up to 17.22 folds) and surfactant protein C (up to 2.71 folds) and downregulated the expression of TGF-β (up to 5.89 folds) and AQP5 (up to 3.28 folds).

Conclusion

We provide substantial evidence that human fetal respiratory tract cells can improve the regenerative process after lung injury. Also, our extensive characterization provides an updated phenotypic profile of these cells.

Highly efficient reprogrammable mouse lines with integrated reporters to track the route to pluripotency

Revealing the molecular events associated with reprogramming different somatic cell types to pluripotency is critical for understanding the characteristics of induced pluripotent stem cell (iPSC) therapeutic derivatives. Inducible reprogramming factor transgenic cells or animals-designated as secondary (2°) reprogramming systems-not only provide excellent experimental tools for such studies but also offer a strategy to study the variances in cellular reprogramming outcomes due to different in vitro and in vivo environments. To make such studies less cumbersome, it is desirable to have a variety of efficient reprogrammable mouse systems to induce successful mass reprogramming in somatic cell types. Here, we report the development of two transgenic mouse lines from which 2° cells reprogram with unprecedented efficiency. These systems were derived by exposing primary reprogramming cells containing doxycycline-inducible Yamanaka factor expression to a transient interruption in transgene expression, resulting in selection for a subset of clones with robust transgene response. These systems also include reporter genes enabling easy readout of endogenous Oct4 activation (GFP), indicative of pluripotency, and reprogramming transgene expression (mCherry). Notably, somatic cells derived from various fetal and adult tissues from these 2° mouse lines gave rise to highly efficient and rapid reprogramming, with transgene-independent iPSC colonies emerging as early as 1 wk after induction. These mouse lines serve as a powerful tool to explore sources of variability in reprogramming and the mechanistic underpinnings of efficient reprogramming systems.

Use of High-Rate Ventilation Results in Enhanced Recellularization of Bioengineered Lung Scaffolds

While transplantation is a viable treatment option for end-stage lung diseases, this option is highly constrained by the availability of organs and postoperative complications. A potential solution is the use of bioengineered lungs generated from repopulated acellular scaffolds. Effective recellularization, however, remains a challenge. In this proof-of-concept study, mice lung scaffolds were decellurized and recellurized using human bronchial epithelial cells (BEAS2B). We present a novel liquid ventilation protocol enabling control over tidal volume and high rates of ventilation. The use of a physiological tidal volume (300 μL) for mice and a higher ventilation rate (40 breaths per minute vs. 1 breath per minute) resulted in higher cell numbers and enhanced cell surface coverage in mouse lung scaffolds as determined via histological evaluation, genomic polymerase chain reaction (PCR) analysis, and immunohistochemistry. A biomimetic lung bioreactor system was designed to include the new ventilation protocol and allow for simultaneous vascular perfusion. We compared the lungs cultured in our dual system to lungs cultured with a bioreactor allowing vascular perfusion only and showed that our system significantly enhances cell numbers and surface coverage. In summary, our results demonstrate the importance of the physical environment and forces for lung recellularization. Impact statement New bioreactor systems are required to further enhance the regeneration process of bioengineered lungs. This proof-of-concept study describes a novel ventilation protocol that allows for control over ventilation parameters such as rate and tidal volume. Our data show that a higher rate of ventilation is correlated with higher cell numbers and increased surface coverage. We designed a new biomimetic bioreactor system that allows for ventilation and simultaneous perfusion. Compared to a traditional perfusion only system, recellularization was enhanced in lungs recellularized with our new biomimetic bioreactor.

You Say You Want a Resolution (of Fibrosis)

In pathological fibrosis, aberrant tissue remodeling with excess extracellular matrix leads to organ dysfunction and eventual morbidity. Diseases of fibrosis create significant global health and economic burdens and are often deadly. Although fibrosis has traditionally been thought of as an irreversible process, a growing body of evidence demonstrates that organ fibrosis can reverse in certain circumstances, especially if an underlying cause of injury can be removed. This body of evidence has uncovered more and more contributors to persistent and nonresolving tissue fibrosis. Here, we review the present knowledge on resolution of organ fibrosis and restoration of near-normal tissue architecture. We emphasize three critical areas of tissue homeostasis that are necessary for fibrosis resolution, namely, the elimination of matrix-producing cells, the clearance of excess matrix, and the regeneration of normal tissue constituents. In so doing, we also highlight how profibrotic pathways interact with one another and where there may be therapeutic opportunities to intervene and remediate pathological persistent fibrosis.

Chaotic activation of developmental signalling pathways drives idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterised by an important remodelling of lung parenchyma. Current evidence indicates that the disease is triggered by alveolar epithelium activation following chronic lung injury, resulting in alveolar epithelial type 2 cell hyperplasia and bronchiolisation of alveoli. Signals are then delivered to fibroblasts that undergo differentiation into myofibroblasts. These changes in lung architecture require the activation of developmental pathways that are important regulators of cell transformation, growth and migration. Among others, aberrant expression of profibrotic Wnt-β-catenin, transforming growth factor-β and Sonic hedgehog pathways in IPF fibroblasts has been assessed. In the present review, we will discuss the transcriptional integration of these different pathways during IPF as compared with lung early ontogeny. We will challenge the hypothesis that aberrant transcriptional integration of these pathways might be under the control of a chaotic dynamic, meaning that a small change in baseline conditions could be sufficient to trigger fibrosis rather than repair in a chronically injured lung. Finally, we will discuss some potential opportunities for treatment, either by suppressing deleterious mechanisms or by enhancing the expression of pathways involved in lung repair. Whether developmental mechanisms are involved in repair processes induced by stem cell therapy will also be discussed.

Cell-Based Therapeutic Approaches for Cystic Fibrosis

Cystic Fibrosis (CF) is a chronic autosomal recessive disease caused by defects in the cystic fibrosis transmembrane conductance regulator gene (CFTR). Cystic Fibrosis affects multiple organs but progressive remodeling of the airways, mucus accumulation, and chronic inflammation in the lung, result in lung disease as the major cause of morbidity and mortality. While advances in management of CF symptoms have increased the life expectancy of this devastating disease, and there is tremendous excitement about the potential of new agents targeting the CFTR molecule itself, there is still no curative treatment. With the recent advances in the identification of endogenous airway progenitor cells and in directed differentiation of pluripotent cell sources, cell-based therapeutic approaches for CF have become a plausible treatment method with the potential to ultimately cure the disease. In this review, we highlight the current state of cell therapy in the CF field focusing on the relevant autologous and allogeneic cell populations under investigation and the challenges associated with their use. In addition, we present advances in induced pluripotent stem (iPS) cell approaches and emerging new genetic engineering methods, which have the capacity to overcome the current limitations hindering cell therapy approaches.

Monocyte-derived multipotent cell delivered programmed therapeutics to reverse idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a highly heterogeneous and fatal disease. However, IPF treatment has been limited by the low drug delivery efficiency to lungs and dysfunctional "injured" type II alveolar epithelial cell (AEC II). Here, we present surface-engineered nanoparticles (PER NPs) loading astaxanthin (AST) and trametinib (TRA) adhered to monocyte-derived multipotent cell (MOMC) forming programmed therapeutics (MOMC/PER). Specifically, the cell surface is designed to backpack plenty of PER NPs that reach directly to the lungs due to the homing characteristic of the MOMC and released PER NPs retarget injured AEC II after responding to the matrix metalloproteinase-2 (MMP-2) in IPF tissues. Then, released AST can enhance synergetic effect of TRA for inhibiting myofibroblast activation, and MOMC can also repair injured AEC II to promote damaged lung regeneration. Our findings provide proof of concept for developing a strategy for cell-mediated lung-targeted delivery platform carrying dual combined therapies to reverse IPF.

Mesenchyme-free expansion and transplantation of adult alveolar progenitor cells: steps toward cell-based regenerative therapies

Alveolar type-2 (AT2) cells are necessary for the lung’s regenerative response to epithelial insults such as influenza. However, current methods to expand these cells rely on mesenchymal co-culture, complicating the possibility of transplantation following acute injury. Here we developed several mesenchyme-free culture conditions that promote growth of murine AT2 organoids. Transplanting dissociated AT2 organoids into influenza-infected mice demonstrated that organoids engraft and either proliferate as AT2 cells or unexpectedly adopt a basal cell-like fate associated with maladaptive regeneration. Alternatively, transplanted primary AT2 cells also robustly engraft, maintaining their AT2 lineage while replenishing the alveolar type-1 (AT1) cell population in the epithelium. Importantly, pulse oximetry revealed significant increase in blood-oxygen saturation in primary AT2 recipients, indicating that transplanted cells also confer increased pulmonary function after influenza. We further demonstrated that both acid installation and bleomycin injury models are also amenable to AT2 transplantation. These studies provide additional methods to study AT2 progenitor potential, while serving as proof-of-principle for adoptive transfer of alveolar progenitors in potential therapeutic applications.