# Fibroblast heterogeneity in pulmonary fibrosis

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2021 · $812,923

## Abstract

ABSTRACT
Pulmonary fibrosis, characterized by accumulation of extracellular matrix (ECM) proteins that impair normal
function, is a major cause of disability and death. Although considerable research has been done to identify
multiple potential lineages of cells that can give rise to the fibroblasts responsible for ECM production, it has
been widely assumed that these cells are a relatively homogeneous population of cells called myofibroblasts,
characterized by high expression of a smooth muscle actin (aSMA). However, limited information about the
molecular characteristics of these cells in vivo has limited our understanding of the basic biology underlying
fibrosis and hampered the development of effective therapies. To address this important gap, we have used
single cell RNA sequencing (scRNAseq) of collagen producing cells to identify multiple distinct cell types that
produce collagen in the normal and fibrotic murine and human lung. Using proximity ligation in situ
hybridization (PLISH) we identified subsets of collagen-producing cells with distinct molecular signatures that
were concentrated within the walls of conducting airways (peribronchial), surrounding bronchovascular bundles
(adventitial) and diffusely distributed in gas exchanging regions (alveolar). After treatment with bleomycin, a
distinct new subset emerged that expressed high levels of collagens and other ECM proteins and was uniquely
marked by expression of collagen triple helix repeat containing protein 1 (cthrc1). scRNAseq of dissociated
cells from normal and fibrotic human lungs also identified a population of cells marked by CTHRC1-expression
that expressed the highest levels of collagens and other ECM proteins and was only seen in lungs from
patients with pulmonary fibrosis. In the studies proposed here, we will first determine the geographic and
temporal distribution and lineage of cthrc1+ cells in single and repeated dose bleomycin models using PLISH,
adoptive transfer and novel ERcre lines we are developing to track cells derived from peribronchial, adventitial
and alveolar fibroblasts. Next, we will evaluate the functional roles of cthrc1+ cells using adoptive transfer into
normal or bleomycin-treated mice, in vitro studies of an array of behaviors associated with pathologic
fibroblasts, and through deletion of these cells by crossing a novel cthrc1-ERcre line we have generated to
mice expressing lox-stop-lox dta in the Rosa locus. Finally, we will examine the functional significance of each
of the major collagen-producing cell populations we have identified in normal lungs at baseline and in models
of alveolar and airway fibrosis, using a similar ablation strategy or through deletion of genes previously shown
to contribute to tissue fibrosis. From these studies we hope to gain novel insights into the roles each of these
unique fibroblast subsets plays in lung homeostasis and disease.

## Key facts

- **NIH application ID:** 10133129
- **Project number:** 5R01HL142568-02
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Dean Sheppard
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $812,923
- **Award type:** 5
- **Project period:** 2020-04-01 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10133129

## Citation

> US National Institutes of Health, RePORTER application 10133129, Fibroblast heterogeneity in pulmonary fibrosis (5R01HL142568-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10133129. Licensed CC0.

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