Fibrosis & Fibrocytes
What’s a Fibrocyte?
•Fibrocytes are blood-borne cells with the ability to produce
extracellular matrix (ECM)
•The cells express the hematopoietic cell surface markers
CD34+, CD45+, as well as fibroblast markers such as collagen
•The fact that these cells circulate in blood, express collagen and
the leukocyte cell surface marker CD 34 makes them unique
among connective tissue cells
•Previous studies looking at wound injury have estimated that up to
10% of the cells that infiltrate sites of acute injury may be fibrocytes
What’s a Fibrocyte?
•The cells express CD34 cell surface marker indicating that they are
derived from the bone marrow. CD45 indicates that they are from
the leukocyte family.
•They can under prolonged culture acquire a myfibroblast
phenotype (increase expression of ASMA)
•They traffic to the longs in response to the chemokine CXCL12 and
have been thought to be involved in the pathogenesis of
What do they do and why are they important?
•Fibrocytes are a sub-population of peripheral blood cells that
produce connective tissue proteins such as collagens and alpha
smooth muscle actin
•It’s suggested that they play a pivotal role in wound healing and
tissue repair by:
– serving as potent antigen presenting cells
– producing important cytokines, chemokines and growth factors necessary for wound
– secreting essential extracellular matrix proteins involved in wound repair
– serving as a contractile force in wound closure via alpha smooth muscle actin expression
– promoting angiogenesis (growth of new blood vessels from pre-existing vessels)
•Fibrocytes have been identified in scar tissue and more recently in
the lung tissue of IPF (Idiopathic Pulmonary Fibrosis) patients
Why are we interested in them?
• Sarcoidosis, also called sarcoid (from the Greek 'sark' and 'oid'
meaning "flesh-like") is an immune system disorder that most
commonly arises in young adults
• Can be hard to diagnose early
• Many patients do not require treatment and recover
• Difficult to identify those who’ll need treatment from those who don’t
• Treatment is with corticosteroids
• Is it possible to predict who will develop severe sarcoidosis, and
therefore will need treatment, based on their fibrocyte count?
• Long term study (years)
• Enrol patients
• Isolate fibrocytes and see can we detect them via FACS
• See is it possible to detect and identify fibrocytes directly from
whole blood without culture
• Determine if there are differences between mild and severe
• Do circulating fibrocyte levels in blood vary over time in sarcoid
• Can we predict on presentation whether a patient needs
treatment now or will recover themselves?
How are we studying them?
• Cells are then analysed by FACS for:
CD34/CD45 and Collagen I
or CXCR4 Collagen I