Gene The histopathology examination revealed milder changes. The graft

Gene Therapy
99

 

Another
promising option for organ transplantation recondition and prevention or
attenuation of the ischaemia / re-perfusion injury in transplanted organs could
be the gene transfer. There is a unique advantage that in transplantation a
graft can be successfully transduced prior to it by donor pre-treatment or even
gene therapy while preservation is taking place 100.  The aim is the expression of the therapeutic
gene post transplantation 101. So far two methods are available for
introduction of genetic code into tissue or cellular level; via recombinant
viruses or via other non-viral transfer techniques (i.e. lipid mediated,
electroporation etc).  The later ones are
superior in view of not eliciting immunological response in the transplanted
patient however with poor results in vivo 102, 103. Examples of gene transfer
include;

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–       
anti-oxidative molecules

–       
anti-apoptotic molecules

–       
cytoprotective   proteins

–       
cytokines and cytokine antagonist

 

An interesting study focuses on Ischemia-Reperfusion
Injury in Kidney Transplantation. They proposed perfusing organs with small
interference RNA (siRNA) cocktail solution to attenuate the effect of above and
delayed graft function 104. 
Ischemia-reperfusion (I/R) injury, is thought to be the main cause of
renal graft dysfunction and failure in kidney transplantation.  The mechanisms of I/R have been investigated
thoroughly and reports suggesting that it involves activation of numerous
signalling pathways leading to upregulation of genes and as a result promoting
cell death via apoptosis and ultimately being responsible for graft damage 105,
106. In that experimental protocol in mice the donor kidneys were perfused
with siRNA solution. Then those kidneys were transplanted into the recipient
mice. To assess the effect of this proposed solution on I/R injury they
assessed the renal function, inflammation levels, histopathology examination as
well as cell apoptosis.  The mechanism of
action of siRNA solution included suppression of the expression of complement
3, RelB, and Fas in the kidney at the mRNA and protein level. Their results
suggested that in treated mice levels of blood urea and creatinine were lower
compared to controls. The histopathology examination revealed milder changes.
The graft survival was longer. Levels of some cytokines such as IL-6 and TNF-?
which are proinflammatory were also reduced.  
Overall, they reported that siRNA based treatments may have a place in
organ reconditioning via gene silencing 104.

 

 

 

Pharmacological Manoeuvres
99

 

There
is evidence to suggest that there are ways to prevent cellular damage secondary
to ischaemia, cellular activation or mononuclear cells infiltration during
re-perfusion. Certain pharmacological agents are key in facilitating above
pre-transplantation; either application of those pharmacological manoeuvres in
the donor, or in the allograft during preservation.  These agents include nitric oxide (NO),
carbon monoxide (CO), hydrogen sulphide (H2S), serine plasma proteases, heparin,
thrombalexin  and others. It has been
observed that gases such as NO, CO and H2S may boost the function and increase
the survival of transplants 107. There are studies to suggest that CO has
anti-inflammatory action as well as promotes cytoprotection. With regards to
kidney grafts, inhalation of it leads to protection of the graft from cold
ischaemic reperfusion injury and preservation of its function post
transplantation 108. Inhalation therapy and use of these gases requires
controlled ventilation or may promote adverse cardiac side – effects etc. In
the future the role of medical gas therapy in the recondition of transplants
will have to target on certain administration aspects and safety. Only
randomised controlled trials can outline the indications of their use and result
in production of guidelines. 

 

 

Another
research team has worked on pre-treatment of organs with cytotopic
anti-coagulant peptides with the ability to localise to endothelial cell
membranes 109. Based on evidence that these could reduce microvascular
thrombotic related damage post-transplantation they designed a series of
ex-vivo haemoperfusion plus NMP preservation protocol in porcine and human
kidneys. The molecule they used was Thrombalexin (TLN), a cell binding
thrombin-inhibitor. They showed improved perfusion
in TLN-treated kidneys versus controls: 26.4% superior flow, 28.9% greater
perfusion flow indices and improved microvascular capillary perfusion when
assessed by orthogonal polarization spectral imaging. Also, they tested
rapid-sampling microdialysis (RSM) in terms or assessing organs condition.  With this technique they measured cortical
lactate in order to assess organ’s ischaemia. They found drop in lactate levels
in kidneys pre-treated with Thrombalexin 109. Lastly there was a reduction in
generation of fibrin in the treated group. 
Overall, they concluded that use of cytotopic anticoagulant peptides can
be done directly to the grafts ex vivo during machine perfusion and this has a
potential role in suppressing the microvascular thrombotic sequelae but at the
same time bypassing the risks of systemic anticoagulation.

 

 

Cell Therapy
99 

 

Cell transplantation may be an alternative for
improving organ condition. Stem cells and others from any origin could be
valuable sources of protective molecules with positive effects when present in
organ preservation. These molecules include growth factors and investigators
have proposed two modes of application; donor pre-treatment and enrichment of
the preservation solution with the above molecules.  The first has ethical limitations as some consider
it as treating the donor without benefit for him however the second has hurdles
such as the low temperature that causes delay in molecule penetration or uptake
by the cells and obstacles in process control.

 

With
regards to kidney transplantation, there has been research on enrichment of
preservation fluid with combination of growth factors known as “trophic
factors”. It has resulted in greater survival rates post transplantation 110,
111.  A commonly used source of this
trophic cocktail includes stem and progenitor cells that normally produce
numerous cytokines and growth factors. 112, 113. Another characteristic of
these cells is their ability to resist to hypoxia 114.

 

 

There
is research in rats to suggest that administration of mesenchymal stem
cells  (MSC) boosts recovery and
attenuates damage caused from I/R and subsequent acute renal failure 115.
Although the exact mechanisms are not yet clear, it seems that
anti-inflammatory properties and tissue repair pathways are involved via the
interactions and communication between MSCs, macrophages, dendritic cells etc
at cellular level 116.  These effects
of MSCs and their ability to assist cellular reconstruction after an ischaemic
insult have included them as a new treatment option in acute kidney injury 117.
Lastly there is research on use of autologous MSCs to boost renal graft
acceptance 118.