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What is IPF?Insights into Pathogenesis

Paul WoltersProfessor

University of California, San Francisco

Outline• Predisposition to Idiopathic Pulmonary

Fibrosis (IPF)– Epidemiology of IPF– Genetic predisposition

• Initiation of IPF– Epithelial cell dysfunction

• Telomere dysfunction• Propagation of IPF

– Pathologic Matrix

IPF: Pathology IPF: Pathology

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IPF: Survival

/IPF

Predisposition to IPF: Epidemiology

Risk Factors for IPF

• Tobacco smoking• Working in dusty environments• Gastroesophageal reflux disease• Aging• Genetic predisposition

IPF is a Disease Associated With Aging

Ley, Clin Epidemiol 2013

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Population is Aging Prevalence of IPF is Increasing

Raghu et al, Lancet Resp Med 2014

Predisposition to IPF: Genetics

Genetics: Dyskeratosis Congenita• Skin hyperpigmentation• Nail dystrophy• Oral leukoplakia• Liver cirrhosis• Bone marrow failure• Lung fibrosis

Caused by mutations in:TERT, TERC, proteins in shelterin complex

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Telomerase Mutations and Lung Fibrosis

• Patients with Dyskeratosis Congenita have mutations in TERT, TERC, DKC1 and lung fibrosis

• TERT/TERC mutations are found in 8-15% of patients with FPF, 5% with IPF.

• Lung fibrosis is found in 40% of patients with TERT/TERC mutations. Diaz de Leon et al, Plos One ‘10

Alder et al, PNAS ‘08Armanios et al, New Engl J Med ‘07

Genes Associated with Familial ILDSPASPC

TERTTERCRTEL1PARN

ABCA3TINF2DKC1

Genetics: Familial IPF

Nogee et al, NEJM ‘01Thomas et al, Am J Resp Crit Care Med ‘02Armanios et al, New Engl J Med ’07Tsakiri et al, PNAS ‘07Alder et al, PNAS ’08Wang et al, Am J Hum Genet ‘09Diaz de Leon et al, Plos One ’10Kropski et al, Chest 2014Stuart et al, Nat Genetics ’15Cogan et al, Am J Resp Crit Care Med ‘15

Genetics: Sporadic IPF

Fingerlin et al, Nat Gen 2013

1616 pts with IPF

4618 controls

MUC5B Variant • MUC5B: Glycoprotein encoded by the MUC5B gene.• Expressed mostly in distal airways

– Increased expression in honeycomb cyst of IPF lung• Odds ratio for developing disease

– Heterozygous (GT)= 6.8-9.0– Homozygous (TT)= 21-22

• Genetic association replicated in many studies.• Variant causes increased MUC5B expression. Unknown

how this contributes to disease pathogenesis.

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IPF Genetic Predisposition: SummaryGenes Associated with Familial ILD Genes Associated with Sporadic IPF

SPA MUC5BSPC DSP

TERT TERTTERC TERCRTEL1 OBFC1PARN DPP9

ABCA3 FAM13ATINF2 TOLLIPDKC1

Pulmonary fibrosis genetic studies overwhelmingly implicate epithelial cells and telomere dysfunction in disease process

Initiation of IPF: Epithelial cell Telomere Dysfunction

Telomeres/Telomerase• Telomere: Repetitive DNA

sequence at end of chromosomes, which protect the end of chromosomes from deterioration.

• Maintained by telomerase

• Telomeres progressively shorter with each cell division.

• Cells with short telomeres either senesce or die.

Peripheral Blood Leukocyte Telomeres Shorten with Aging

Vaziri et al. AJHG (1995) Cawthon et al. Lancet (2005)

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Lung Telomeres Shorten Relatively More Than other Organs

Gardner et al, J GerontolBiol Soc 2007

Peripheral Blood Leukocyte Telomeres Length Predicts IPF Patient Survival

Stuart et al, Lancet Resp Med 2014

Time to Death

Telomeres are Shortened in IPF Type II Cells

Alder J K et al. PNAS 2008Kropski et al. Am J Resp Crit Care Med 2015Wolters, unpublished

Epithelial Cell Senescence is Unique to IPF

IPF Normal

HP SSc

Disayabutr et al, PLOSONE 2016

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Modeling Telomere Dysfunction

Modeling Telomere Dysfunction in Mice

• Mouse telomeres are 5-10x longer than human telomeres

• Deletion of TERT or TERC do not successfully model diseases of telomere dysfunction– Mice become sterile before diseases manifest.

Blood 2012

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Type II Cell-Specific Telomere Dysfunction Causes Lung Fibrosis

Naikawadi et al, JCI Insight 2016

Type II Cell-Specific Telomere Dysfunction Causes Lung Fibrosis

**p< 0.01

Naikawadi et al, JCI Insight 2016

0

10

20

30

40

50

TRF1F/F

SPC-creTRF1F/F

*

3M 8MTamox

Act

ive

TG

F- β1

(pg

/ml)

Lung Remodeling is Associated with Increased Levels of Active TGFβ

Propagation of IPF :Pathologic Matrix

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IPF Fibroblast Biology• IPF fibroblasts are different from “normal” fibroblasts.

– Resistant to apoptosis– Make more collagen– More invasive

• Fibroblast phenotype differs when cultured on matrix of different stiffness (Young’s elastic modulus).– Stiffness of lung: 1 kPa– Stiffness of plastic: 2-4 GPa

• Fibroblasts alter phenotype when cultured on matrix derived from IPF lung vs. normal lung

Decellularized lung

Booth et al, AJRCCM, 2012

IPF Extracellular Matrix Has a Unique Composition

Higher in IPF Matrix Lower in IPF Matrix

Booth et al, AJRCCM, 2012

IPF Matrix is Stiffer than Normal

Booth et al, AJRCCM, 2012

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Fibrotic Matrix Activates a Positive Feedback

Parker et al JCI 2014

IPF Pathogenesis: Summary

ER Stress AECII turnover

Normal TII Cell TII Cell replicationTelomere shortening

TII Cell replicationTelomere Shortening

Misfolded proteinInfectionsGenetic predisposition (SPC, TERT, TERC, MUC5B)

Environmentalinsult, Time/Ageing

SenescentTII Cell

Activated fibroblastMyofibroblast differentiation

Deposition of pathologic matrix

apoptosis

Critically short telomere’s

Clinical Relevance: IPF Comorbidities• Family history• Early Greying (< age 30) of hair may be clue to

telomere dysfunction, IPF• Bone marrow abnormalities

– Macrocytic anemia– Myelodysplastic syndrome

• Predisposition to cancer• Co-morbidity of cirrhosis

Clinical Relevance: Management• Engage in behaviors that maintain telomere

length– Aerobic exercise – De-stress your life, increase social support– Healthy diet, antioxidants, fish oil

• Engage in behaviors that limit risk for injury to the lung– Avoid pollution– Vaccinate– No smoking