School of Medicine
PhD Project Application 2017
Sarcopenia in liver disease – systemic effect of hepatocyte senescence?
SECTION 1 – Project Details:
Maximum 800 words, using the following headings
Rationale:
The incidence of liver disease is on the rise and will continue to rise for the foreseeable
future. Further, liver disease is the only major cause of death still increasing year-on-year
and is the third most common cause of premature death in the UK1. Sarcopenia, a common
phenomenon in end-stage liver disease, is an independent risk factor of morbidity and
mortality; the cause/s for sarcopenia are not fully understood2. Malnutrition is unlikely to be
the sole cause, as it fails to explain the presence of sarcopenia in non-alcoholic fatty liver
disease, which is associated with over nutrition in the vast majority of cases.
Cellular senescence is evident in up to 80% of hepatocytes in advanced liver disease and is
known to play a crucial role in disease progression3-5. Accumulation of senescent
hepatocytes alters the microenvironment and influences neighbouring stellate cells, nonsenescent hepatocytes, and immune cells through secretion of a wide variety of factors5
(local paracrine effect). Given that these are highly potent chemical mediators, the possibility
of sarcopenia being a systemic consequence of the release of secretory factors from
senescent hepatocytes (systemic paracrine effect) warrants further investigation. This is a
novel concept and has not been explored in the past. However, it is not an unsubstantiated
concept as hepatocytes have been shown to regulate systemic metabolism and energy
homeostasis through secreting hepatokines6.
Aims and methodology:
The overarching aim of this project is to explore the possible relation between hepatocyte
senescence and sarcopenia and to identify factor/s which are involved in exerting this
influence (liver-muscle axis senescence mediators).
1. Influence of senescent hepatocyte secretory factors on muscle cells
Induction of cellular senescence in primary human hepatocytes will be achieved through
oxidative stress using sub-lethal concentrations of hydrogen peroxide in three-dimensional
cell cultures. Primary human skeletal muscle cells will then be cultured in culture media of
senescent hepatocytes. The changes in morphology, metabolic activity, and function of
striated muscle cells cultured in senescent hepatocyte culture media will be studied in detail
using a variety of techniques including confocal microscopy, immunohistochemistry,
fluorescent in situ hybridization, metabolic assays, and quantitative reverse transcription
polymerase chain reaction (qRTPCR).
2. Comparing in vitro and in vivo changes in primary human skeletal muscle cells
Muscle biopsy specimens will be collected from patients with end-stage liver disease and
marked sarcopenia, patients with early stage liver disease (no sarcopenia), and healthy
volunteers. The difference in morphology, metabolic status, and gene expression between
these three groups will be studied in detail using immunohistochemistry and qRTPCR, and
will be compared to the changes seen cultured skeletal muscle cells.
3. Identifying potential secretory factors which may induce/influence sarcopenia
Secretory factors in senescent hepatocyte culture media will first be identified using mass
spectrometry proteomics and ELISA techniques. The presence of these factors will then be
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School of Medicine
PhD Project Application 2017
explored in the serum samples (collected at the time of muscle biopsy) of above
patient/volunteer groups.
The influence of any common secretory factors identified between senescent hepatocyte
culture media and serum sample from patients with end-stage liver disease will be studied in
vitro by blocking/neutralising these factors individually and in combination. This is may lead
to identification of unique factor/s which are involved in liver-muscle axis, opening a novel
avenue for therapeutic manipulation.
Benefits and suitability as a PhD project:
The role of cellular senescence in chronic diseases is an emerging concept in the field of cell
biology and hepatology. The prognostic role of sarcopenia is being increasing recognised as
an independent predictor of clinical outcome. This project, which marries cellular
senescence to sarcopenia is novel and therefore has the potential for high impact journal
publications, attracting major grants, and more importantly may open an innovative avenue
to make a meaningful impact in the management of liver disease. The objectives of this
project are realistic and achievable within a 3 – 4 year PhD programme. This project will
provide knowledge, exposure, and training in all basic techniques required to develop into a
successful basic scientist.
Key References:
1. Williams, R. et al. Lancet 384, 1953-1997 (2014).
2. Nishikawa, H. et al. Hepatology research 46, 951-963 (2016).
3. Aravinthan, A. et al. Journal of hepatology 58, 549-556 (2013).
4. Aravinthan, A. et al. PloS one 8, e72904 (2013).
5. Aravinthan, A. D. & Alexander, G. J. Journal of hepatology 65, 825-834 (2016).
6. Jung, T. W. et al. Biochimica et Biophysica Acta Clinical 5, 108-113 (2016).
SECTION 2 – Training Provision:
Maximum of 250 words. Please detail the training provision that will be made available to the
student.
Professor MacDonald and Dr Bennett have considerable experience in PhD supervision.
The expertise and facilities for the training of the PhD candidate in all basic techniques
required for successful completion of this project is available within the School of Medicine
and School of Life Sciences. Further, the PhD candidate will have the opportunity to train
with Dr Bennett’s group which is one of the few groups in the country with expertise in threedimensional culture of primary hepatocytes and primary skeletal muscle cell culture.
In addition to the basic science techniques, the candidate will also be trained in writing
scientific articles and grant applications, and establishing successful collaborations with
clinicians and scientists, tools that are essential for a successful career in science.
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