Will hepatocyte transplantation replace liver transplantation ? Future aspect

1. Will hepatocyte transplantation replace
liver transplantation ? Future aspect
 DR MD AB QUIYUM
 PHASE B
 HEPATOBILIARY ,PANCREATIC & LIVER TRANSPLANT SURGERY

2. Introduction
 Liver transplantation is the accepted treatment for patients with acute
liver failure and liver-based metabolic disorders.
 However, donor organ shortage and lifelong need for immunosuppression
are the main limitations to liver transplantation.
 In addition, loss of the native liver as a target organ for future gene
therapy for metabolic disorders limits the futuristic treatment options,
resulting in the need for alternative therapeutic strategies.
 A potential alternative to liver transplantation is allogeneic hepatocyte
transplantation

3. Aim
 The aim of hepatocyte transplantation in patients
presenting metabolic disorders is to restore hepatic
functions without replacing the entire organ.

4. Indication
 2 major disease ..
 1. liver-based metabolic disorders that do not lead to cirrhosis.
 Crigler-Najjar syndrome, in which there is a defect in the enzyme that
conjugates bilirubin
 urea cycle disorders, in which there is abnormal processing of amino
acids, leading to elevated ammonia levels;
 and phenylketonuria, in which phenylalanine is not processed
 2. acute liver failure.
 In general, candidate conditions for hepatocyte transplantation are those in
which the architecture of the liver is intact.

5. The number of cells necessary for
correcting a deficit is unknown
For example, Crigler-Najjar syndrome, 12% of the liver mass is necessary
LIVER ..2.8% of the TBW , 1.5 kg/ADULT.
The minimum liver mass.. survival .. 10–30% of the total organ or 200–600 g.
Considering 120 million human hepatocytes/gram of tissue, a minimum of 2.5–7.5
billion cells would be required for a clinical therapeutic treatment
Nevertheless, major challenges for the wide clinical application of hepatocyte therapy include
availability, metabolic integrity, and sufficient amount of cells for transplantation.
 Transplanted cells are generally no longer observed after 6–9 months and it is not clear if
this is due to rejection, apoptosis, or other causes.
 109 cells are required for cell therapy

6. Source
 unviable organs for transplantation would become sources of viable
hepatocytes for transplantation.
 Each year, a large number of cadaverous donor livers for transplantation are
rejected.
 The reasons include high-grade steatosis, nonviral cirrhosis, and death due to
heart failure

7.  . Human hepatocytes are isolated from
 (i) whole donor livers unsuitable/rejected for OLT, mostly because of
severe steatosis, prolonged ischemia time, older, or non-heart-beating
donors, or
 (ii) from liver segments, mainly I and IV, which are available for cell
isolation after split liver transplantation.
 3. fetal and neonatal livers are being explored as a potential cell
source as they are currently not considered for OLT and may allow
the isolation of very high-quality cells .
 4. Explanted livers from patients with liver-based metabolic disorders
have also been considered as a potential source of cells,so-called
“domino” liver transplantation

9. procedure
a standardized three-step collagenase perfusion technique
First, major hepatic vessels are cannulated and perfused with Hank’s buffered
salt solution (HBSS) containing EGTA, which is able to chelate calcium ions, thus
disrupting the desmosomes, calcium-dependent cell-to-cell adhesions.
Second, the liver is flushed with plain HBSS to remove any residue of EGTA.
Third, the tissue is perfused with a calcium-dependent collagenase solution to
digest the extracellular matrix.
After breaking of the liver capsule, the released liver cells are filtered and
centrifuged at low speed to separate hepatocytes from nonparenchymal cells.

10. Hepatocytes can be used fresh for transplantation or cryopreserved.
cryopreserving 106–107 cells/ml in the University of Wisconsin organ
preservation solution
Cryopreserved hepatocytes are then stored at –140 °C until required for HT.
Most centers consider a dose of 2 × 108 cells per kg of body weight as the
upper safe limit for hepatocyte transplantation

11. lack of anchorage for the transplanted cells and
host immune response.. viability. encapsulation
of hepatocytes in alginate microbeads ..
prolonging survival.
hepatocyte-like cells (HLCs) , iPSC-derived HLCs,
safety concern for clinical applications is their
tumorigenic potential, which needs to be solved
before these cells can be used safely in humans

13.  Hepatocytes …sinusoidal vessels ….transient occlusions in the
periportal vascular areas .. followed by restoration of normal blood
flow by vascular permeabilization,
 which allows transplanted cells to reach the liver parenchyma
 Hepatocytes remaining in the portal vessels are cleared by
macrophages within 24 h.
 The number of cells injected is limited by portal pressure, which
should be monitored throughout by Doppler ultrasound, and should
not exceed 12 mm Hg to avoid the risk of portal hypertension (

14. Is it reversible ?
 1. significant infection
 2. an immune suppression–related complication,
 3. a patient decides to undergo a hepatocyte transplantation, his or her
access to a donor organ and ability to receive an organ transplant is not
affected.

 IF If a patient undergoes hepatocyte transplantation and the procedure does
not adequately correct the liver abnormality, then liver transplantation is
performed as originally planned.
 If a donated organ becomes available during the observation period following
hepatocyte transplantation and the disease has not been corrected liver
transplantation be performed.

15. In Cirrhosis ???
the native liver is structurally abnormal.
Donor hepatocytes are not able to get into the liver because of a thickening of
the extracellular matrix.
Placing hepatocytes in extrahepatic locations, such as the spleen or in a
lymph node, may be effective, but this approach has not been tested
clinically.
In the latest approach … a decellularized liver from an animal, such as a pig, is
repopulated with viable hepatocytes and other types of liver cells, which can
then be used as a bioartificial liver that could potentially be engrafted into the
patient.

16. challenges
 1. supply of an adequate number of cells into the liver .
 2.Isolated hepatocytes .. viable for 48 hours after isolation … transplanted
within this time frame.
 3. capacity of the portal vein …. Portal hypertension .. varices and gastrointestinal
bleeding.
 4. Thrombosis of the portal circulation .. liver dysfunction.
 5.shunting..translocate to the lungs…cardiovascular instability or pulmonary
insufficiency
 6. too late diagnosis
 7. engraftment
 8. difficult to identify transplanted cells by biopsy… difficult.. Predict rejection.
 9. not interested .. experimental intervention, preferring instead to wait for an
organ transplant.

17. Potential solution
 1.cells from multiple donors
 2 to infuse them over a long period of time.
 3. low-dose irradiation .. short-term loss of the endothelial cells ..enter the liver.
 selectively grow ..replaced by donor cells.
4.. stem cells will be harvested from the peripheral blood after stimulation of
bone marrow. with more frequent doses of G-CSF followed by autologous
transfusion of harvested stem cells,

20. Advantage
 1.Chance of spontaneous patient recovery,
 2. increasing patient survival rate while awaiting donation

21. Disadvantage
 1. immunosuppressive regimens include
induction with steroids and calcineurin
inhibitors (tacrolimus or cyclosporine) .
Some centers have also included therapy
with anti-interleukine-2 receptor
antibodies (basiliximab) 1.
 2. ultimately need OLT

22. Difference
 With liver transplantation, the entire organ is replaced.
 If there is acute or chronic rejection that compromises the liver and cannot
be controlled, then the patient may require retransplantation.
 With hepatocyte transplantation, only a small fraction of liver cells—
hepatocytes, the metabolic engine of the liver—are replaced, leaving intact
all of the other types of cells within the liver, including endothelial cells,
stellate cells, Kupffer cells, and fibroblasts.
 With this approach to transplantation, between 5% and 15% of the host’s liver
is replaced with transplanted hepatocytes.
 is difficult to identify transplanted cells by biopsy, which is routinely
performed in organ transplant recipients, so it is difficult to know definitively
whether the donor cells are being rejected until it is too late to intervene.

23. hepatocyte transplantation has several
advantages over OLT
: (i) it is less invasive and less expensive not involving a complex surgery;
(ii) it can be performed repeatedly if required;
(iii) cryopreserved cells isolated from donor livers are available immediately
when needed;
(iv) native liver remains in place serving as a backup in case of cell graft failure
and allowing potential regeneration in patients with acute liver failure (ALF), as
well as representing a possible target for future gene therapy in patients with
liver-based metabolic disorders; and
(v) because this procedure only requires a fraction of the cells isolated from a
donor organ, multiple patients can be treated from one donor tissue, thus saving
other organs for patients who do require OLT.

24. Current Status
 The experience worldwide has been similar from center to center.
down to less than half of their initial values
 partial correction is not adequate because the patients remain at risk for
severe brain injury.
In almost all cases, the patients have ultimately received an organ transplant.

25. Future aspect
 The last two decades have seen a considerable development of hepatocyte
transplantation, with demonstration of short-term efficacy and safety.
 However, some hurdles still need to be overcome to widen hepatocyte
transplantation clinical applications,
 mainly regarding isolation of high-quality cells from marginal donor liver,
improvement of cell engraftment, and long-lasting effects, as well as optimal
immunosuppression regimen identification.

26. Take home message
 With improvements in optimizing delivery technique and assessing
proper recipients of livers, monitoring graft function, as well as
recognizing and treating graft rejection, HTx may be able to be used
more widely in metabolic liver disease and potentially delay necessity
of OLT.

27. Thank you