Scientific Background Interstitial lung diseases (ILD) comprise a large heterogenic group
of conditions which involve the lung parenchyma by inflammation, fibrosis, or both.
Fibrotic ILD (FILD), which are characterized by evidence of lung fibrosis by either
imaging studies (chest CT), and/or histopathology, may result from known exposures or
association, or be idiopathic. Management of FILD depends on specific diagnosis, patient
characteristics, and disease behavior. Some conditions may respond favorably to
immunosuppression, while in others, such as idiopathic pulmonary fibrosis (IPF), such
treatment may be harmful. Antifibrotic therapy may attenuate the progression of various
FILD, including IPF, yet in many cases, disease progression ultimately leads to a fatal
outcome or need for lung transplantation.
Telomeres are repetitive 6-nucleotide sequences which cap the end of chromosomes, and are
essential in stabilizing chromosomes [1]. While they shorten with each cell replication,
telomeres are maintained by complex mechanisms which can add nucleotide repeats
(telomerase), and protect chromosomal ends by other mechanisms. Shortened telomeres may
result from mutations in telomere related genes. Short telomeres have also been
associated with single nucleotide polymorphism in those genes. Telomeres shorten with
age, and are also shorter among males. Additional acquired factors also contribute to
shortening, including harmful exposures, cigarette smoking, obesity, stress, lack of
physical activity, and others [3-4].
Short leukocyte telomere length (LTL), i.e. <10th percentile adjusted for age, are common
in patients with various FILD, with or without identifiable mutations in telomere related
genes, both in familial and sporadic cases [5-6]. Short LTL has been associated with
worse prognosis among subjects with several FILD, including faster deterioration of
pulmonary functions tests, quicker disease progression, and shorter transplant-free
survival [7-11]. In addition, IPF patients with short LTL had worse prognosis when
exposed to immunosuppressive treatment [12], as were patients with other FILD commonly
treated with immunosuppression [13]. Antifibrotic therapy, on the other hand, seems to be
safe and effective [14].
This accumulating data has implications on the management of patients. Experts suggest
testing for LTL in patients with familial pulmonary fibrosis, early age of disease onset,
or with personal or family history of relevant extrapulmonary disease [8, 15]. Prompt
initiation of antifibrotics, early referral for lung transplant and avoidance of
immunosuppression have also been recommended [8, 16].
However, the prevalence of short LTL varies among ethnically diverse cohorts of FILD
patients [7] and have never been assessed in the Israeli population.
Rationale We believe that this study will shed light on the prevalence of short LTL in
Israeli individuals with FILD, and identify predictors which will enable more precise
targeting of LTL measurements in Israel. In addition, it may guide physicians with
regards to careful administration of immunosuppressive treatments in Israeli FILD
patients suspected of having short telomeres.
Hypothesis We believe that the proportion of subjects with short LTL is higher in Israeli
subjects with familial FILD than with sporadic FILD, yet that a significant proportion of
sporadic FILD subjects will also have short LTL.
This may lead to more widespread and evidence-based directed use of LTL measurements
among Israeli patients with FILD.
Study Objectives General Aim To assess the prevalence of short LTL among Israeli patients
with FILD, and identify relevant association and impact of short LTL on those patients.
Specific Aims. 1. To assess the prevalence of short LTL among Israeli patients with familial and
sporadic FILD.
2. To identify risk factors for short LTL in Israeli FILD patients.
3. To prospectively assess the outcome of participants (with and without short
telomeres) using a composite of death of any cause, lung transplantation, and forced
vital capacity (FVC) decline ≥5% over a 1-year period [17].
4. Additionally, we will conduct an exploratory analysis of the components of the
composite outcome measure as well as other possible criteria for progressive
pulmonary fibrosis (PPF), including annual decline of diffusion capacity for CO
(DLCO) ≥10%, FVC decline ≥10%, FVC decline 5-9%, DLCO decline ≥15%, CT progression
of fibrosis, and clinical worsening of symptoms [17, 18].
Research Design & Methods This is a prospective study, with collaboration of two Medical
Centers: The Pulmonary Fibrosis Center of Tel-Aviv Medical Center (Ichilov), a tertiary
medical center in Central Israel, and the Division of Pulmonary Medicine of Barzilai
University Medical Center, a secondary, peripheral medical center from Southern Israel.
A total of 90 patients with FILD will be recruited from the two clinics, thus
representing diverse Israeli population. This cohort will include 30 patients with
familial pulmonary fibrosis and 60 with sporadic lung fibrosis.
Patients with familial pulmonary fibrosis are those with at-least one first-degree or
second-degree relative with FILD [8].
10 healthy age-matched controls with no personal or family history of lung disease will
be recruited as well.
Thus, sample size of the whole study, as well as in our Center will include up to 100
participants.
Participants with FILD will be followed-up for 1-year after recruitment, including
clinical and pulmonary function tests at-least every 6 months, or more frequently,
according to the treating physician discretion. Collected data will include participants'
demographics and anthropometrics, family history and personal medical history, pulmonary
function tests results, thoracic imaging and histopathological patterns, clinical
diagnoses of FILD (according to a multidisciplinary team discussion), treatment and
outcome.
Measured Variables.Collected data will include (see attached excel file data sheet):
- - Past medical history, co-morbidities, and medications.
- - Specific ILD therapies.
- - Clinical findings, including physical examination, laboratory tests, pulmonary
function tests, imaging, echocardiography, lung biopsy diagnosis, bronchoalveolar
lavage differential.
- - Diagnosis of lung cancer or other malignancy.
- - Outcomes, including annual decline of pulmonary function tests, worsening symptoms,
worsening CT signs of lung fibrosis, lung transplantation, and death.
LTL measurement In addition to clinical data, blood samples will be collected to measure
LTL using the "gold standard" Telomere Restriction Fragment (TRF) Analysis method. In
short, genomic DNA (2-5 µg) is digested overnight at 37°C with HinfI restriction
endonuclease. Fragments are being separated on an agarose gel, transferred to a Hybond N+
membrane. The membrane is being hybridized over night at 50°C with a 5' end-labeled
(AACCCT)3 oligonucleotide probe and with ladder probe of 1Kb ladder. Following membrane
washes the membrane is exposed to PhosphoImager. The mean telomere length is calculated
by the computer program Telotool [19-20]. TRF analysis will be conducted at the
laboratory of Prof. Yehuda Tzfati at the Hebrew University, which is highly experienced
in the field of telomere biology and in telomere length analysis. Blood samples will be
taken once from each participant. As detailed above for LTL measuremement, no genetic
sequencing will be performed as part of this study.
Sample Size Calculation Assuming that 50% and 20% of participants in the familial FILD
and sporadic FILD will have short LTL, a sample size of 87 patients (29 familial and 58
sporadic FILD) is required to detect significant differences in the proportions of
subjects with short LTL with an alpha error rate of 0.05 and 80% power.
The proposed study will require approval by local Institutional Review Boards and
Helsinki Committees of both Medical Center. Individuals will provide informed consent
prior to participation in the study.
Inclusion Criteria. 1. Adult subjects, aged ≥18-years-old. 2. Able and willing to provide informed consent to participate in the study. 3. Lung fibrosis evident on chest CT (signs of honeycombing and/or traction
bronchiectasis) [17]
4. Subjects fulfilling criteria 1 and 2 but with no evidence of chronic lung disease
will serve as controls Exclusion Criteria. 1. Subjects with sarcoidosis as the etiology for FILD 2. Subjects who had undergone
lung transplantation 3. Pregnant women.Statistical Analysis Comparison between groups (i.e., familial vs.#46;sporadic FILD, patients
with vs.#46;without short LTL) will be performed using Chi-square test, Mann-Whitney test, or
Student's T-test, according to measured variables. Correlations will be assessed by
calculating Pearson's or Spearman's coefficients, as appropriate. Assessing predictors of
short LTL and of disease progression will be analyzed using univariate and multivariate
logistic regression analysis models.