Persistent, Progressive Pulmonary Fibrosis and Epithelial Remodeling in Mice

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic interstitial lung disease with underlying mechanisms that have been primarily investigated in mice after intratracheal instillation of a single dose of bleomycin. However, the model has significant limitations, including transient fibrosis that spontaneously resolves and its failure to fully recapitulate the epithelial remodeling in the lungs of patients with IPF. Thus, there remains an unmet need for a preclinical model with features that more closely resemble the human disease. Repetitive intratracheal instillation of bleomycin has previously been shown to recapitulate some of these features, but the instillation procedure is complex, and the long-term consequences on epithelial remodeling and fibrosis persistence and progression remain poorly understood. Here, we developed a simplified repetitive bleomycin instillation strategy consisting of three bi-weekly instillations that leads to persistent and progressive pulmonary fibrosis. Lung histology demonstrates increased collagen deposition, fibroblast accumulation, loss of type I and type II alveolar epithelial cells within fibrotic areas, bronchiolization of the lung parenchyma with CCSP+ cells, remodeling of the distal lung into cysts reminiscent of simple honeycombing, and accumulation of hyperplastic transitional KRT8+ epithelial cells. Micro-computed tomographic imaging demonstrated significant traction bronchiectasis and subpleural fibrosis. Thus, the simplified repetitive bleomycin instillation strategy leads to progressive fibrosis and recapitulates the histological and radiographic characteristics of IPF. Compared with the single bleomycin instillation model, we suggest that the simplified repetitive instillation model may be better suited to address mechanistic questions about IPF pathogenesis and preclinical studies of antifibrotic drug candidates.

Loss of Fas signaling in fibroblasts impairs homeostatic fibrosis resolution and promotes persistent pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible fibrotic disease of the distal lung alveoli that culminates in respiratory failure and reduced lifespan. Unlike normal lung repair in response to injury, IPF is associated with the accumulation and persistence of fibroblasts and myofibroblasts, as well as continued production of collagen and other extracellular matrix (ECM) components. Prior in vitro studies have led to the hypothesis that the development of resistance to Fas-induced apoptosis by lung fibroblasts and myofibroblasts contributes to their accumulation in the distal lung tissues of IPF patients. Here, we test this hypothesis in vivo in the resolving model of bleomycin-induced pulmonary fibrosis in mice. Using genetic loss-of-function approaches to inhibit Fas signaling in fibroblasts, potentially novel flow cytometry strategies to quantify lung fibroblast subsets, and transcriptional profiling of lung fibroblasts by bulk and single cell RNA sequencing, we show that Fas is necessary for lung fibroblast apoptosis during homeostatic resolution of bleomycin-induced pulmonary fibrosis in vivo. Furthermore, we show that loss of Fas signaling leads to the persistence and continued profibrotic functions of lung fibroblasts. Our studies provide insights into the mechanisms that contribute to fibroblast survival, persistence, and continued ECM deposition in the context of IPF and how failure to undergo Fas-induced apoptosis impairs fibrosis resolution.

Protein Tyrosine Phosphatase-N13 Promotes Myofibroblast Resistance to Apoptosis in Idiopathic Pulmonary Fibrosis

RATIONALE

Idiopathic pulmonary fibrosis (IPF) is a progressive, fibrotic interstitial lung disease characterized by (myo)fibroblast accumulation and collagen deposition. Resistance to Fas-induced apoptosis is thought to facilitate (myo)fibroblast persistence in fibrotic lung tissues by poorly understood mechanisms.

OBJECTIVES

To test the hypothesis that PTPN13 (protein tyrosine phosphatase-N13) is expressed by IPF lung (myo)fibroblasts, promotes their resistance to Fas-induced apoptosis, and contributes to the development of pulmonary fibrosis.

METHODS

PTPN13 was localized in lung tissues from patients with IPF and control subjects by immunohistochemical staining. Inhibition of PTPN13 function in primary IPF and normal lung (myo)fibroblasts was accomplished by: 1) downregulation with TNF-α (tumor necrosis factor-α)/IFN-γ, 2) siRNA knockdown, or 3) a cell-permeable Fas/PTPN13 interaction inhibitory peptide. The role of PTPN13 in the development of pulmonary fibrosis was assessed in mice with genetic deficiency of PTP-BL, the murine ortholog of PTPN13.

MEASUREMENTS AND MAIN RESULTS

PTPN13 was constitutively expressed by (myo)fibroblasts in the fibroblastic foci of patients with IPF. Human lung (myo)fibroblasts, which are resistant to Fas-induced apoptosis, basally expressed PTPN13 in vitro. TNF-α/IFN-γ or siRNA-mediated PTPN13 downregulation and peptide-mediated inhibition of the Fas/PTPN13 interaction in human lung (myo)fibroblasts promoted Fas-induced apoptosis. Bleomycin-challenged PTP-BL-/- mice, while developing inflammatory lung injury, exhibited reduced pulmonary fibrosis compared with wild-type mice.

CONCLUSIONS

These findings suggest that PTPN13 mediates the resistance of human lung (myo)fibroblasts to Fas-induced apoptosis and promotes pulmonary fibrosis in mice. Our results suggest that strategies aimed at interfering with PTPN13 expression or function may represent a novel strategy to reduce fibrosis in IPF.

Nintedanib reduces pulmonary fibrosis in a model of rheumatoid arthritis-associated interstitial lung disease

Rheumatoid arthritis (RA)-associated interstitial lung disease (RA-ILD) develops in ~20% of patients with RA. SKG mice, which are genetically prone to development of autoimmune arthritis, develop a pulmonary interstitial pneumonia that resembles human cellular and fibrotic nonspecific interstitial pneumonia. Nintedanib, a tyrosine kinase inhibitor approved for treatment of idiopathic pulmonary fibrosis, has been shown to reduce the decline in lung function. Therefore, we investigated the effect of nintedanib on development of pulmonary fibrosis and joint disease in female SKG mice with arthritis induced by intraperitoneal injection of zymosan (5 mg). Nintedanib (60 mg·kg-1·day-1 via oral gavage) was started 5 or 10 wk after injection of zymosan. Arthritis and lung fibrosis outcome measures were assessed after 6 wk of treatment with nintedanib. A significant reduction in lung collagen levels, determined by measuring hydroxyproline levels and staining for collagen, was observed after 6 wk in nintedanib-treated mice with established arthritis and lung disease. Early intervention with nintedanib significantly reduced development of arthritis based on joint assessment and high-resolution μ-CT. This study impacts the RA and ILD fields by facilitating identification of a therapeutic treatment that may improve both diseases. As this model replicates the characteristics of RA-ILD, the results may be translatable to the human disease.

Fertility status and symptoms in childbearing couples

The symptoms of 58 pregnant couples--37 with a history of infertility and 21 without a history of infertility--were compared. The Symptomatology Inventory, a checklist of 42 common physical and psychological symptoms of pregnancy, was completed by each spouse from months 4 to 9 of pregnancy. For purposes of analysis, the individual symptoms were grouped into three categories: physical symptoms, negative affective symptoms, and positive affective symptoms. Although the infertile pregnant couples did not experience more symptoms than fertile couples, their pattern of reporting pregnancy-related symptoms was quite different. In terms of both number and type of symptoms, infertile spouses' symptoms tended to be positively related. Compared to fertile couples, the infertile couples experienced symptoms globally and were more consistent in the number of symptoms reported by each spouse. Additional research is needed to confirm these findings and to determine the implications of these differences for childbearing and the martial relationship.

Comparison of pregnancy symptoms of infertile and fertile couples

This study was undertaken to describe the most common symptoms experienced during pregnancy by couples with a history of infertility and to compare them with symptoms of expectant couples without a history of reproductive problems. The Symptomatology Inventory, a 42-item checklist of common pregnancy symptoms, was used. The 10 most frequent symptoms reported and their rank order were very similar for the women from both groups. Men from the two groups frequently reported similar symptoms, but differed on their rank order. This research provides evidence that in terms of pregnancy symptoms infertile and fertile couples are more alike than they are different.

The epistemology of expectant parenthood

A secondary analysis of information obtained from 288 interviews, conducted with 62 childbearing couples in the course of a qualitative and longitudinal study, suggests that much of the work of expectant parenthood is oriented toward getting to know the fetus. This article emphasizes the epistemological (as opposed to the emotional) relationship between parent and fetus.

Beyond couvade: pregnancy symptoms in couples with a history of infertility

Thirty-six couples with a history of infertility reported their physical, positive emotional, and negative emotional symptoms during pregnancy. The women experienced more physical symptoms than did the men. Both the men and women experienced second-trimester decreases in negative emotional symptoms and third-trimester increases in negative emotional symptoms. The women's physical symptoms also showed a second-trimester dip. Each symptom type was correlated for husbands and wives, but only 6 husbands showed evidence of couvade syndrome by exhibiting exact correspondence with their wives' symptoms. Symptom attunement appears to be a better term than couvade for most infertile men's experiences of pregnancy.

Blood lead levels and behaviour of 400 preschool children

A study of 400 Sydney children of preschool age has found a range of blood lead levels from 0.1 mumol/L to 1.4 mumol/L (2 micrograms/100 mL to 29 micrograms/100 mL), with no children having readings above the currently accepted "level of concern". Within the Sydney metropolitan area, a significant inverse relationship was found between blood lead level and distance of the home from the city centre. Within the range of blood lead levels, no relationship appeared between blood lead levels and performance in verbal intelligence test, three of the tests of motor ability, and a parent rating. In one of the tests of fine motor coordination, there was a tendency for the children with lower lead levels to perform better than those with moderate blood lead levels. In one of the tests of gross motor skill, the results for the two age groups were conflicting. Further studies of a prospective nature covering the period of maximum vulnerability (0 to three years) are essential before any conclusion can be drawn about the effects of subclinical blood levels of lead.

Children born after elective induction of labour

A comparison was made between the performance at eight years of age of 63 children who were born after elective induction of labour, and 29 spontaneously born children. The children had been tested previously at five years of age. Tests of reading and arithmetic achievement, visuomotor coordination, aural-visual coordination, auditory discrimination, and behavioural rating scales were administered. On two of the 12 measures (reading comprehension and euroticism) the induced children performed better than the spontaneously born. On all other measures there were no significant differences. There appeared to be no evidence of specific learning disabilities or behavioural problems among the induced children.

Method of delivery and developmental outcome at five years of age

A controlled follow-up study examined the impact of delivery method on developmental outcome of the child. The modes of delivery investigated were low forceps delivery (188 infants), midcavity forceps delivery (51 infants), forceps rotation with forceps delivery (57 infants), manual rotation with forceps delivery (67 infants), elective caesarean section (101 infants) and spontaneous delivery (control, 207 infants). Breech presentation (100 infants) was separately compared with the vertex presentation groups. Sample selection controlled for complications during pregnancy and low birthweight and was restricted to married English-speaking mothers. The children were assessed at the age of five years on verbal and non-verbal subtests of a standardized intelligence scale, tests of gross motor coordination, and auditory and visual tests. A full paediatric examination was also performed. Breech presentation children performed less well on tests of balance and fine motor coordination and on visual acuity and stereopsis testing than children who presented in the vertex position. No deleterious effect of delivery method was found. In the absence of other complicating events (like a poor antenatal history, prematurity, and a disorganized home environment) delivery complication constitutes an early risk factor which the growing child is able to overcome.