Ischaemic stroke develops through an interference with blood supply to the brain and
continues to be one of the leading causes of morbidity and mortality in the World. Global
medical statistics reveal that ~75% of all stroke patients are older than 65 years and that
the stroke occurrence more than doubles every 10 years after the age of 55 in both men and
women.
Although various mechanisms may alter the structure and function of the adult brain during
the aging process, endothelial dysfunction is regarded as the main pathology that renders
cerebral vessels susceptible to atherosclerosis and subsequent vascular events. Endothelial
dysfunction also constitutes the main cause of vascular abnormality in most lacunar strokes
which result from occlusion of one of the penetrating arteries deep within the brain.
Cortical strokes represent another common form of ischaemic stroke and develop from an
embolism from the heart or large arteries. As the endothelium maintains vascular balance
through regulation of many distinct functions like vascular permeability, tone and
inflammation, it is of crucial importance to preserve its integrity and function at all times
to prevent age- and stroke-related vascular damage.
Recent studies show that bone marrow-derived endothelial progenitor cells (EPCs) play a key
role in sustaining appropriate endothelial function by re-endothelialisation of blood vessels
in adult brain and ischaemic settings. Like embryonic angioblasts, EPCs are equipped with an
inherent capacity to circulate, proliferate and differentiate. Hence, the markers of
endothelial maturity (KDR), immaturity (CD133) and stemness (CD34) must be simultaneously
detected in relevant studies to identify all endothelial-committed and undifferentiated
cells.
It is likely that environmental changes, like oxidative stress, inflammatory responses and
nitric oxide availability, evoked by ischaemic injury and aging may also suppress the
generation and function of EPCs. As mobilisation, recruitment and homing of EPCs to sites of
vascular injury are mediated by various growth factors like the SDF-1 (stromal cell-derived
factor-1), VEGF (vascular endothelial growth factor) and GCSF (granulocyte-colony stimulating
factor), it is likely that the diminished expression of these factors may also negatively
influence the number and function of EPCs.
Interestingly, while there is little data on functional and numerical alteration of EPCs
during the chronic phase of stroke, current data regarding EPC levels during acute and
subacute phases of disease are inconsistent in that stable, increased or decreased numbers
have been reported as compared to healthy subjects.The time course of EPC release after acute
cerebral infarction also remains inconclusive.
In light of the above, the aims of the current study are to reveal whether 1- variations in
circulating EPC levels and/or their functional aspects may be used as markers to identify
ischaemic stroke subtypes and predict patients' outcome; 2- differences in EPC
number/function during acute, subacute or chronic phases of stroke correlate with severity
and functional outcome of ischaemic stroke; 3- EPC counts and function are affected by aging
process; and 4- levels or activity of key pathophysiological elements like VEGF, inflammatory
cytokines and nitric oxide, known to affect EPC count and function, differ between patients
with lacunar and cortical strokes and between stroke patients and healthy counterparts.
STUDY MANAGEMENT Independent outcome assessments (mRS, BI, NIHSS) will be performed on
admission and days 7, 30 and 90 after stroke. The laboratory procedures will be carried out
by a post-doctoral research fellow who will collate and analyse the data. The Chief
Investigator has overall responsibility for the study and shall oversee all study management.
The data custodian will be the Chief Investigator.
PARTICIPANT DURATION Each participant with stroke will be followed-up for 90 days from the
time of recruitment. Elderly and young healthy volunteers will be seen only once.
RECRUITMENT Participants will be recruited from Nottingham University Hospitals Stroke
Services. The initial approach will be from a member of the patient's usual care team (which
may include the investigators) who will inform the participant or their nominated
representative of all aspects pertaining to participation in the study. It will be explained
to the potential participant that entry into the study is entirely voluntary and that their
treatment and care will not be affected by their decision. It will also be explained that
they can withdraw at any time.
PARTICIPANT WITHDRAWAL Participants may be withdrawn from study in cases of disease
progression and withdrawal of consent. The participants will be made aware that this will not
affect their future care.
INFORMED CONSENT No patient will be recruited into the study without obtaining their written
informed consent. In cases of incapacity, the consent of an appropriate personal consultee
will be sought. The Investigator will explain the details of the study and provide a
Participant Information Sheet. Participants will be offered 24 hours to consider
participation. However, they will be allowed to consent at an earlier time, if they prefer.
In cases where stroke patients regain capacity, they will be re-consented for their ongoing
participation in the study.
STATISTICS All results including subject characteristics will be reported as means±SD.
Continuous variables, including age and circulating EPC level will be analysed by independent
t-test among groups. Circulating EPC levels at different time points (within 48 h and on days
7, 30 and 90 post-stroke) will be compared using the repeated measures of ANOVA. Scheffe's
multiple comparison will be used to analyse the intra-individual courses of parameters over
time. These will then be compared among patients with lacunar and cortical strokes. Multiple
logistic regression analyses will determine the independent impact of different predictive
variables on functional outcome and neurological deficits.
Sample size have been calculated to allow for failures of patient attendance on days 30 and
90 (15% for each time point) and possibility of patients illness/death during the course of
the study (5%).
ADVERSE EVENTS As this is not an interventional study, no adverse event is anticipated to
develop because of it. Adverse events of venepuncture will be dealt with according to
standard practice.
DATA PROTECTION The study form will only collect the minimum required information for the
purposes of the study. Study forms will be held securely, in a locked room, or locked
cupboard or cabinet. Access to the information will be limited to the study staff and
investigators and relevant regulatory authorities. Computer held data including the study
database will be held securely and password protected. All data will be stored on a secure
dedicated web server. Access will be restricted by user identifiers and passwords (encrypted
using a one way encryption method). Information about the study in the participant's medical
records / hospital notes will be treated confidentially in the same way as all other
confidential medical information. Electronic data will be backed up every 24 hours to both
local and remote media in encrypted format.
STUDY DATA Monitoring of study data shall include confirmation of informed consent; source
data verification; data storage and data transfer procedures; local quality control checks
and procedures, back-up and disaster recovery of any local databases and validation of data
manipulation. The Academic Supervisor, or where required, a nominated designee of the
Sponsor, shall carry out monitoring of study data as an ongoing activity.
Entries on study forms will be verified by inspection against the source data. A sample of
study forms (10% or as per the study risk assessment) will be checked on a regular basis for
verification of all entries made. In addition the subsequent capture of the data on the study
database will be checked. Where corrections are required these will carry a full audit trail
and justification. Study data and evidence of monitoring and systems audits will be made
available for inspection as/when required.