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Cell Biology and Toxicology. 1996; 12: 325-329.
' e. I! I+ f3 {, i, S# G$ |© 1996 Kluwer Academic Publishers. Printed in the Netherlands * J9 K2 k1 @% S+ Z5 d$ O2 R
Cell-based therapy of acute liver failure: The extracorporeal bioartificial liver
( V4 w6 ~1 I! g7 f- HB. Fr6mond, A. Joly, M. Desille, J.F. Desjardins, J.P. Campion and B. C16ment
$ r. _# L' J: [, A+ e3 e- @Detoxication and Tissue Repair Group, Institut National de la Santd et de la Recherche Mddicale,
3 v- o' _0 R9 @* _2 `2 R0 BRennes I University School of Medicine, CHRU Pontchaillou, Rennes, France 0 D, F, k! H0 ~- v9 f
Accepted 11 July 1996
: c4 C" f. J1 z t# fKeywords: acute liver failure, bioartificial liver, cell-based therapy, hepatocytes
+ y$ {/ |3 z4 f- hAbstract # n: ^$ j3 n* h* }- ]0 w, | J
The need for an alternative treatment to orthotopic liver transplantation for acute liver failure is a $ y( ~7 c: j" o( ]7 a/ t
major issue, and systems capable of temporarily providing liver functions are being actively tested.
' T: C |5 ~1 [$ [: u/ [Liver assist devices based on detoxication by dialysis or hemoperfusion through various membranes ( {+ ^! V& [9 Q' Q. R0 n4 y
or cartridges proved to be inefficient because of their lack of metabolic function. An extracorporeal 8 I* i P8 ] }+ G5 k( C
hybrid bioartificial liver might be an appropriate treatment, since it can provide liver-specific ! ^" V* ?6 q z# O8 `. g {4 Z% J
functions, maintain the patient alive, and allow spontaneous recovery of the patient's own liver or
- k2 F, Q5 c% y; Zact as a bridge toward liver transplantation. Many devices have been proposed, including fiat # f- B9 i+ F3 F* S
culture substrates, hollow-fiber bioreactors, or microcarriers, using xenogenic hepatocytes or
" J/ z. _: s8 C, v+ T1 \$ F7 Uhepatoma cell lines. Various drawbacks of these devices led us to attempt to develop a reliable
" A) w; ?8 Y9 R+ i! y7 @, xextracorporeal bioartificial liver based on alginate bead-entrapped hepatocytes. This system was
. p* V* ]4 c, y% Oused successfully for the correction of the Gunn rat genetic defect, which results in lack of bilirubin " z; {1 r t# C" Y3 U
conjugation. The development of this system for clinical purposes requires large yields of functional - |+ y8 k% k W
hepatocytes. We have isolated normal porcine hepatocytes by collagenase perfusion of the liver. ( [% A; _' T+ n6 W' m
Cells were immobilized in membrane-coated alginate gel beads, which were subsequently inoculated
9 x2 _) P: q! B% Y3 Q4 \8 C% Sinto a bioreactor. Porcine hepatocytes expressed liver-specific functions at high levels, particularly 5 x# i! u' c) q N
protein neosynthesis and enzymatic activities involved in detoxication and biotransformation
. }7 \/ k+ e: y" eprocesses. In addition, hepatocytes entrapped in coated alginate beads were isolated from : P8 u) }' G* {8 L" s$ J
immunoglobulins. This system represents a promising tool for the design of an extracorporeal
, ^0 L W# E' M# s1 h. H: vbioartificial liver in human beings. 5 |# c+ y! B) y2 x; `6 P6 R
Abbreviations: ALF, acute liver failure; EBAL, extracorporeal bioartificial liver; OLT, orthotopic
* n# U; {. Q- H, M( sliver transplantation 9 F: V8 g0 [+ Y+ _# Z
Introduction
7 _7 o* ^* w1 U2 }& h% EAcute liver failure (ALF) remains a therapeutic
% K6 Z! {# R$ n6 X, u# Y% Dchallenge. Despite recent advances, the mor- 1 }( C4 S& p5 o: u6 X; {- A/ M9 }
tality rate is high, ranging between 70% and ' v" H* @/ B5 i, M6 Z! O
90%, depending on both the age and the
% t9 b% T/ S) M1 y \etiology (Hoofnagle et al., 1995). Orthotopic * W8 o/ {2 f- ?4 E6 j& F$ I
liver transplantation (OLT) is the only cur- 3 u. @( M0 t3 h# z& b k
rently effective treatment, but it is a major and $ W: w' Q6 W- l3 K1 t/ k
costly surgical procedure which requires life- 326 & M/ I$ c% w. H! Q% C
long immunosuppression and is associated
3 {; T. \4 b/ N" K+ x' nwith a significant morbidity and mortality.
% C: ~/ W% ]- @% x1 m( X1 q$ C# BFurthermore, by removing the patient's own
# E' O$ |) X0 B F/ o% jliver, OLT prevents any opportunity of a ) F/ V2 `& ]) |6 m
spontaneous hepatic recovery. Finally, scarcity
8 t" ~. J* Z5 S5 mof liver grafts is an important limiting factor. ( A7 `. E( F( f, r* t3 v0 d4 }7 u
There is therefore a striking need for alterna-
" I7 Y% A% \& I3 v; ~; C6 U9 y4 Ltive treatments.
7 _9 V; l8 D2 E7 n$ g& aThe disappointing results of the first- 2 G" k* x# f, |( f6 ?# U$ ^
generation liver assist devices based on dialysis
* Q8 `/ ]* [$ `" Tor hemoperfusion through various membranes 8 e' a$ b: t! n. q8 t
or cartridges have suggested that the restora- 9 `, ?/ m/ P% v6 O: f0 Y* R
tion of hepatic metabolic functions is required
& Q8 W1 j; V, E U8 Ffor efficient treatment of ALF. The best way to
! D- V$ M2 e4 X. ?: lkeep alive patients with ALF, and to preserve
0 ]( C' R' z2 ^$ D8 ]/ Q& btheir neurological potentialities without OLT, # b5 I2 Y4 Z: O
would be to treat them with a hybrid, bio- , x# ^: @& ^" X* \5 s2 T f
artificial system capable of providing appro- 9 E; m7 l' | u7 O* e, m
priate hepatic functions of synthesis, biotrans-
- K8 c* U2 j h8 [1 Y! D! R8 pformation, and detoxication. Such a system
; d9 a0 y& M9 L) s2 Mcould allow spontaneous liver regeneration or & ^8 m! \, j3 J, L0 n
act as a bridge toward OLT in good conditions. . {. q3 {$ \6 _
Fulminant hepatic failures from viral, toxic, or
! @8 ^7 r' B: e* ]drug origin would be the main indication for
" h. Y4 F k" Athis therapy. Other indications include primary
9 n% g; K6 g6 |( m- J3 Z1 E0 ynonfunctioning grafts after OLT or acute de-
( c( T4 d1 s. i& s: L: Ecompensations of chronic liver insufficiency. 5 O `/ S+ H% u* t3 c
The design of such bioartificial devices is 3 I! D8 z* g- ~2 W( f: I- k" [' D
complex. They should contain hepatocytes, " C! @0 L7 [1 }. F& @0 M
which are highly differentiated and metaboli- 5 A6 N. j6 W" b
cally active cells and are dependent on cell-cell ! C. i/ |, w! M$ R( X* t# X& h5 u
and cell-matrix interactions for their survival ! x4 O# Y# U# V/ L2 n! y
in vitro. Due to the scarcity of human grafts,
; Q0 `' r( t8 j6 n. Uthese hepatocytes may not be normal hepato- 3 `5 I r6 J$ O1 Y, {( O9 I' ?
cytes of human origin. The other sources of
+ o K0 m, A8 t9 \7 Ohepatocytes include either allogenic human . Q! b; v. Z! ~( t/ m4 Z( S0 N
immortalized and/or transformed cell lines or
) J* X4 a2 L, jxenogenic hepatocytes. In order to maintain * O' ]5 x( t; ]1 H3 q
these cells functional within an optimal envir-
0 V# {! O! Z; G3 G8 }$ conment for metabolic exchanges, hepatocytes : P+ g k" b# S$ |
must be in close contact with the patient's
; B+ w- h. `! B$ Vcirculation through an immumoisolating
5 I/ L t* Q" G9 phemocompatible barrier that prevents any
# i( G9 S: s+ |7 w4 Rinteraction with blood cells and immuno-
; F2 C: {+ m9 N& `! a5 fglobulins. The extracorporeal bioartificial liver " T: y P* N' t+ @8 x" t W, o
(EBAL) must be safe for the patient. The 8 o. g/ d0 [' J1 c2 g& j
minimum number of normal hepatocytes in
6 y4 {+ ^3 h; t. han efficient EBAL has been estimated to repre- 2 O* Q3 Q' n2 E! f1 N8 Z
sent at least 10% of the total pool of a normal ) t5 }/ |; S( @8 S6 h# K1 ]1 | C
liver. Cell density should be as high as possible " ^4 k4 T- j2 |& t% M: ^1 l+ Y
so as to obtain efficient mass transfer processes
6 g* L# g H- Y2 Q) J7 k0 }without the need for a bulky device. Finally,
+ `' J, Q# y% M4 G+ a: t0 j% Qthe clinical situation of ALF requires immedi-
; ~- ?- c" W; S/ T. [$ ?ate availability of the EBAL, and manufactur- ' H& N( \& ~' p2 e) L: K
ing, storage, and maintenance of EBALs must 7 } ^7 A1 v0 [4 M3 b ]
meet with industrial and economic gold stan-
8 M1 ]; e6 t5 M3 O5 \4 jdards. 3 I2 a0 `2 {* q. W2 G, n
Several authors have developed bioartificial
+ _; f, f4 P0 G8 R5 A! kliver assist devices. Dialysis with a suspension / z3 ~1 F$ q9 S k$ n! h
of hepatocytes is the simplest one. This is the
# N" C. Q4 d% ^2 e: s8 E5 W, _first system to have been used in a human + B4 [: ]$ K( h
being (Matsumura et al., 1987). However, 1 w. y' X$ A. v# S
hepatocytes are anchorage-dependent for their 5 }9 D+ r, W- G9 J7 D3 ?! Q: B
survival and function, and such a system has a
6 P6 A, J, S+ D7 llimited efficacy. To ensure hepatocyte adhe-
7 l& w" e- {$ H, T0 G5 } gsion, a monolayer culture can be established
: |0 N7 z- B0 {; z1 R, s0 Gin a bioreactor with a large internal surface.
) V) ~- E+ T4 cSuch a bioreactor is based either on stacked
1 Q/ ^0 Z! b2 n) a1 bplates (Takahaski et al., 1992) or on hollow 3 `! Y- ^& L6 I% Y& l
fibers (Gerlach et al., 1994; Jauregui et al., 9 E+ U4 K) G& z- T7 e! ~; u/ C i
1995). In both cases, the potential outputs of
9 G) `, ?& h* e' i1 J: a5 Q6 Rthese two-dimensional systems are very low, : K! g$ m/ w+ L" w
due to the small numbers of cells compared
' W3 B4 R% G: l& o" k: dwith the very large exchange surface. The
5 k9 A* H9 V9 z, ]efficiency of hollow-fiber bioreactors has been
; K7 K- d- G' P' Venhanced by seeding hepatocytes in collagen
1 g; E1 Q, W& D; ~: C5 @gel matrices inside the fibers (Nyberg et al., 1 q( O" r& n9 v) d* R0 S- C
1993). Promising results have been obtained in
o" n& R# ]' k6 ldogs with D-galactosamine-induced ALF (Sie- 3 \* O& _7 N9 e7 h R4 P- L
laff et al., 1995). However, the major draw- 2 J0 E# [0 v0 |3 g. `1 }( C
backs of these hollow-fiber-based bioreactors
0 q+ x4 O& X: I9 Y# \8 Kare time-consuming preparation and the im- ; Z2 r, ?4 j& ~ j* x
possibility of long-term preservation. These * E. D) y2 \7 l4 {2 I6 x2 m
conflict with one of the major requirements of 9 u1 a8 t7 h$ c9 v7 o
EBAL - the absolute need for emergency
7 l$ B4 ], s) g& o" b4 n9 o1 Savailability. ( z4 ^# q4 @8 O" q7 \! T
In order to fulfill this requirement, the bio- ) x2 y2 W2 K9 p/ @6 |
reactor must be prepared and checked in ; `. M" }7 I' i$ }4 W0 ~( m
advance, before storage. Specifically, the most 0 P( T5 `3 }/ ~5 L
time-consuming stage, i.e., preparation and 327 ' A7 q( \2 j, B$ P- R
immobilization of hepatocytes, must not be 9 Z/ i3 j! ~( g: ]- @: ?
done extemporaneously prior to use. It has ! h+ k) v/ V, N/ h( q
been shown that cryopreservation of hepato- , Q' h. M+ [: i- `
cytes is possible and safe (Chesn6 et al., 1993). A/ A+ }& ^7 t) |) v
A prototype meeting this major specification
4 A. R/ o5 Y- {8 ?7 S Rhas been designed by Demetriou and collea- ( Q7 E; `, C$ P' P
gues and tested in rats (Arnaout et al., 1990), % q; Y/ _6 c; r2 d9 K0 b; |5 G. {
dogs (Rozga et al., 1993), and humans
7 V `* Z8 b6 p' L" x(Demetriou et al., 1995). This system contains - N( |: S6 f a; n9 ~" t7 Q9 S
cryopreserved pig hepatocytes attached to # c! N9 S6 P) \$ A; S: P) ]
microcarriers. Microcarriers are inoculated
$ [: p( S' }/ X& {into the extracapillary space of a microporous A9 k( K1 D9 K& b7 E* G
hollow-fiber bioreactor (pore size 0.2 gm).
4 P* @- v- b: J; IPlasma from a plasma separator flows in the 9 J T: ]9 k' S! v
intracapillary space, filters through the mem-
. A- b# f+ j* x- F: F! A# \9 tbrane pores, and interacts directly with hepa- ( [( O9 f# @9 }
tocytes before being reinjected into the " t7 [. Q) F1 j' B! V
patient's circulation. A charcoal column is 3 _% |1 w7 E4 {9 l2 p
inserted in the loop. The membrane has no ( j' r6 ], s# j X8 K
perm-selectivity, large macromolecules includ-
( X* O8 n6 X& W9 g/ v- Sing immunoglobulins being able to permeate. 7 I' u5 F2 g1 A% g' e M; y0 o
Eighteen patients have been treated with such a
5 Q f) _# }% B# |, Ndevice (Chen et al., 1995), either for fulminant 8 Y% h3 v. m& v/ B# {
hepatitis (group A, n = 11) or for acute decom-
) c Y* f% u, g/ Fpensation of chronic hepatopathy (group B, + _' a0 Q; t U' T1 j) H
n = 8). In group B, only two patients underwent
' t) h& A k" w2 k7 U+ M0 xOLT; all others died. In group A, all the : ]4 _3 Q3 M, S" T
patients have undergone OLT, but their neuro-
* e9 a' p I' P' v! x5 d" Q: Tlogical status improved during the EBAL treat- 6 l+ T% v) i `/ m9 t2 |% a
ment. However, a charcoal hemoperfusion
% d: `# Y8 E. [/ K9 k( |5 Q, |alone may also improve the neurological status
/ f! o1 d+ H7 v. h* eof patients with ALF (O'Grady et al., 1988). A
& m. k: b/ u: T! \0 f7 M0 G9 ]major drawback of this system is the direct L* M$ L$ `' b$ v- w# u
contact between human plasma and pig hepa-
. D5 o. ?/ ~, P3 Rtocytes. Although pig hepatocytes are less
: S% a9 z* H D9 A# G- s3 cvulnerable to the cytotoxicity of human natural
7 U! R- g% E# P" _0 w4 jantibodies than other cells, particularly endo-
& I* i! ]- [; u+ dthelial cells (Fujioka et al., 1995), this direct ) K9 p( n7 l3 d# W* s! G2 Z4 m
contact is likely to be deleterious for the
0 T# v: K/ s, v3 [+ d5 z2 N* b9 {6 s1 abioreactor in some cases. Complete immuno- 5 n% K9 \! q7 t0 c$ n1 U
isolation of xenohepatocytes appears manda- + X+ }. ]! N, s' D# |
tory.
# [& [, e8 K0 g% e/ @Immunoisolation of xenohepatocytes can be
+ v$ c+ \% N1 U0 U# Z5 Nachieved in a different design of bioreactor that
, C& d6 F% b% e" ^6 xis based on hepatocytes embedded within
/ \, I1 s0 R* ^ W/ Uhate-entrapped hepatocytes 7 V' k5 A0 F/ `3 a/ `
Figure 1. Schematic diagram of a bioreactor containing porcine $ L& m1 s% A; @5 j Q+ d
hepatocytes entrapped in calcium alginate beads. ( X* f6 }- d! `9 l Z
microspheres made of a semipermeable matrix " F! F! q8 ? g
of calcium alginate. We have developed an $ b: h0 G* |/ }* C6 m
EBAL based on this new concept. Plasma
# v0 \/ o# R) d# i. s+ h8 x7 c) q! wflows inside the bioreactor in direct contact 8 C7 C0 x0 O2 h" n6 \/ }* e1 S
with beads, without the interposition of any 6 ~) S4 }$ {' O
artificial membrane, since hepatocytes have no 8 d1 Q! _8 A! e5 r: R# Y! W6 k
direct contact with plasma (Figure 1). These
7 A: o$ o8 t$ u" Nbeads exhibit a very large surface-volume
S: p+ Y. b& E) L( ?- c& n6 @ratio. Such a system allows optimal mass
+ X: V$ O' x% {0 p0 p- ?transfer conditions, with a high cell density ; d: R2 Z7 U5 h
(up to 107 hepatocytes/ml) and minimal dead 3 V0 t9 M/ N" t" ^9 i4 N
spaces. We have been able to demonstrate the 5 n! G+ Z. x* H d* ?7 q8 [- X' n1 D
efficacy of this device in an experimental model
4 v& c0 l r+ zof impaired liver function in Gunn rats 8 ?& E7 e' g# y/ [; ?* E. f2 @
(Fr6mond et al., 1993). The homozygous Gunn
+ y0 l$ b) S c. l4 R7 l; @rats possess a congenital deficiency of bilirubin
% f( y# k7 T7 P8 Z6 F* U5 Jconjugation. When maintained in EBAL, im-
/ d; v/ t! Y* |mobilized normal rat hepatocytes did not ex- 328 ! Z8 a0 k6 Z3 L
hibit any loss of viability for at least 6 h of & X) G$ T& e0 ~9 _6 d" j
extracorporeal circulation. In the test group of 5 k* E5 w4 L/ B3 N
Gunn rats, the concentration of total biliary ) c @$ o& T: d% w5 v$ {
bilirubin conjugates increased rapidly, reach- ' _$ I9 t1 H* s
ing more than 200 gmol/L after 3 h in some ) v& |, r% N% S* Y8 N+ o
cases, as compared with less than 1 gmol/L in - p$ W. D+ t+ c( ~6 G P
the control group. Recently, we have designed . }+ v: t$ g, M K9 J# W0 O3 Y& H
a similar bioreactor for experimental purposes - o4 I$ _% P8 F( ^, w
with large mammals and future potential clin- 6 n. |' @% i& n6 ~; C- s
ical use (Joly et al., accepted, in press). Survi- ]* v- c$ y- f8 k1 S3 [3 M; k
val, proliferation, and functions of porcine
& L# ~7 ]; u* t* h1 _; Lhepatocytes were evaluated in primary mono- 9 k& R6 F% T; w8 q0 \6 h
layer culture and after embedding in alginate $ D9 @5 K$ E. a( R' _* a
beads that were subsequently coated with a
. c! G& i0 d; k8 s7 imembrane, produced by a transacylation reac-
6 R* r0 w+ I- }- A" n2 t7 r& W6 Wtion between alginate and albumin, in order to
: e2 b+ E5 V+ \& o4 X5 R: nimprove the immunoisolation. Disruption of 6 k1 ?7 r" p- o1 d; Y) B! D( X O
whole pig livers by collagenase perfusion al-
, d' _2 }* ~' @% ]* Y; i+ Qlowed up to 8 x 101° hepatocytes, with a viabi-
R# J5 `* ]2 w: u" a r9 P1 s! ^lity greater than 90%, to be obtained. ; ^/ h& E( ?4 \# c! S
Hepatocytes in monolayer culture or en-
5 u# `' l4 e- E6 @3 m+ T$ i, ltrapped in coated alginate beads survived for
/ H4 k( G- B0 ^& v( Pabout 10 days, secreted proteins, and main-
1 E- S3 j m! y6 v% v. H4 l! Xtained at high levels several phase I and phase * a% M) t8 s! S0 Q! {" E
II enzymatic activities, namely, ethoxy- , b m0 A" K6 f% X% w; [) s$ d
resorufin-O-deethylase, oxidation of nifedipin
: |6 }- `! ?7 r) o" U# Nto pyridine, phenacetin deethylation to U$ k, j6 b G# h( y* [8 n
paracetamol, glucuroconjugation of paraceta- % T; [* Z2 N) @1 ^2 t; }
mol, and N-acetylation of procainamide. Typi- . g- \+ @# c, |# S4 g
cal features of mitosis and [3H]thymidine
+ {1 q! Q4 u; ~, e& k, kincorporation showed that porcine hepatocytes
+ t1 B: C* O; \7 [+ o1 j1 v! i5 u7 Kproliferated spontaneously in both monolayers
% d5 U: c% w( P! t& S4 v ]and beads. The immunoisolating properties of 9 i$ O; s$ h. @' n$ l
the coated alginate beads were checked by # Y' S h+ E% s. } F4 v; A
incubating entrapped HLA-typed human
+ N- N9 i' i! D* f* qlymphocytes with specific anti-HLA immuno- 6 i# w- X7 C' h# X+ d6 d
globulin G and complement: no lysis was
2 R/ ~- a$ }& T/ ^6 e7 M9 I9 j( kobserved, in contrast to controls (non-
2 n$ ?* _2 S8 K/ Yentrapped lymphocyteS)o In addition, we have 8 N& P+ X& K3 n: \, O( `
recently demonstrated that cryopreservation of ]" P7 F& o7 g v6 S; [3 D
hepatocytes immobilized in alginate beads did 1 c- P* @9 E' X
not result in marked alterations of liver-specific " L+ _. W# a* a
functions (Guyomard et al., accepted, in + c" D. Q1 _1 p7 }
press). 1 j) g3 N4 X% L: Q% P
All of the devices described above use hepa- 8 ^ C) N& G% z/ ~# k* |
tocytes of animal origin, mainly from the pig. 9 V$ h1 ^1 ~9 D4 j# \1 U
Many initial problems have been solved
d7 g! J5 R9 q: Kthrough the use of animal hepatocytes, includ-
# H. y- H6 y6 T! Sing isolation, culture, immobilization, func- 2 w u/ H! l+ v+ n, x/ O7 K0 E
tional studies, and cryopreservation. The main
/ y" Q5 ]9 l8 g, v3 z8 Jproblems that remain to be settled are first of
5 b1 x# V1 w- limmunological nature and second the risk of * U2 d6 x- A5 Z- S: k- b
xenogenic infections. The immunological pro-
! ~/ x% ~% J7 e: e1 G d3 lblem has been solved in part by the use of & L+ k# t2 `; h
alginate beads, which prevent the risk of dele-
4 A, h$ U( T0 y0 Z4 U& qterious effects of human plasma on the cells.
, A( o" p' e" n3 M9 QHowever, both the function and immuno-
2 @! K9 Y& Z! u; R+ ~genicity of xenogenic neosynthetized proteins " L, @. ~+ O) U( W) n
in human beings remain unknown. Only few 2 m' a- w5 Q* F; o
data are available concerning this important 3 Y3 A6 P+ O( ^- z: D
issue. A baboon-to-human liver transplanta-
7 a8 V8 ~' [- Q& Xtion was recently performed by T.E. Starzl
; S2 |3 c$ K# E. ^4 _3 t P( l( Land colleagues (Starzl et al., 1993). In that
: c7 _$ G+ w. F: icase, the function of the baboon proteins ( A9 l1 `2 |) a
synthetized by the graft seemed to be normal, 0 j$ \- \' h7 E. u
but their immunogenicity has not been investi- 0 ~* f2 ]9 C0 @7 A- k) W2 _5 w
gated, due to immunosuppressive drugs and % V) @5 t4 }4 o' V0 E/ ?0 W# ] T# N& A/ T
the patient's brief survival. The risk for patients ! `9 D9 G- t% \/ v0 F
and public health of xenogenic infections, 6 g( x' g( q$ e
particularly retroviral, is a major concern. This 8 m! F: R( ~9 y
risk would probably be minimized by using 2 `3 | c: v7 A6 R6 |4 {
hepatocytes from pigs, which are phylo- $ l6 ]7 M% M) S' A
genetically more distant from the human spe-
6 k' s9 v' i$ g- s0 rcies than are primates (Chapman et al., 1995). 4 S0 C* o% @( Q/ |
In order to overcome the problems raised by & Z- @" h9 E5 o+ s6 e$ S
the use of xenohepatocytes in EBAL, Sussman
- B0 C1 i- G0 Y; E5 x7 s. B9 vand colleagues have designed another type of
4 i- h% G( Z3 d7 y9 Y1 K0 Z$ cliver assist device, based on a hollow-fiber
$ H/ @! D. k: R" sbioreactor containing cells from the human
1 `8 n" |/ v4 CC3A cell line (Sussman et al., 1992). This well- 9 k# k m! c$ ?% U0 N5 x! U
differentiated cell line was isolated from a child 5 t7 U1 z, N) s- u
hepatoblastoma. Cells are inoculated in the
& G4 f* ?) i" C- f) ^; n( _1 D' g- kextracapillary compartment of a bioreactor
& t( Z, N6 w% W' W0 f- @' Fand are allowed to grow until confluence for a
- V. F% T; d5 D9 b1 ]) b/ l, ~few weeks, after which cells survive within the & T9 `$ V/ D2 _$ f$ [
bioreactor for several months in vitro. This 0 X# `- o6 ^6 V1 c# D$ @" A
allows immediate availability for clinical use, 7 p6 G4 e; w' L
at the cost of important culture and storage - ~4 @0 y% r8 O5 H0 m5 u
units capable of maintaining hundreds of bio- " U& V7 s5 U& G. L
reactors for several months. Such an EBAL 329
* K7 { i5 x) a5 A3 Y; V5 e( r6 ncontains a significant mass of cells, and could
4 P6 S4 O2 H* j* K: D. Xthus potentially represent a very efficient de- # m) N( t9 Y. c9 s+ }1 ?1 E
vice. A multicentric study is in progress in the
, E- k$ g. F& b* O2 K" \, @United States and Europe. Preliminary results
5 y: F* s1 u3 |from 17 patients have been published recently
r% F/ n' J! C% g: R(Sussman et al., 1994; Ellis et al., 1994), but no
\7 P5 L1 H5 N7 `$ N% odefinitive conclusion can be drawn. The major
3 d" I5 q. y/ c0 \drawback of this system is the use of C3A - }8 L' s2 J% a; p
neoplastic cells in the EBAL. The risk of tumor
$ W% p8 L( o3 g$ H8 u! z2 s5 ugraft and/or induction in the treated patients
: d' \0 n; p6 k4 vhas been suggested. Moreover, it is known that
9 ?# s O: Y3 f9 m5 Athe functional capacities of transformed & L* ~% f, ^2 f. F3 r/ i3 S
hepatoblastoma cells are much lower than % u- @& P0 O3 S* A2 ]% R
those of freshly isolated normal hepatocytes.
( B* [6 y3 `' gIn conclusion, there are many solutions to 8 B; _+ j m1 \) Z/ x5 g
the various problems raised in the use of an 2 L Z- L4 `- `" K! K
extracorporeal bioartificial liver for the treat- 9 X! r6 s* F& }7 ~+ d
ment of ALF. Each solution displays advan-
# ]3 X2 p* d2 K7 P8 atages and disadvantages, but the existing 4 o1 j4 D0 ]2 b- Q
results clearly show that cell-based therapy of 1 W' S1 R3 [$ [( o- a7 f) T- Y- i
ALF is feasible and should be available in the
$ n5 y4 b) S4 x0 \& ^; ~near future. 8 N) X- N) O8 e) B; J2 {( B1 b
Acknowledgments
! C3 I5 f6 z8 G, v. v4 Z8 R4 hThis work was supported by INSERM and by
$ w0 o" J w& [$ l7 e3 U2 H, pgrants from Minist~re de la Recherche
5 N( z4 T2 z" b/ m) S7 u" n(DSPT5-ACC-SV No.14; Biotechnologie) and
Y2 t/ o) @! [! Y8 z9 H9 EFondation de l'Avenir (ET5.144). * x5 r6 I5 x4 H5 {' {6 w' h
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Address for correspondence." Benjamin Fr6mond, Groupe DRT, 7 Q0 w5 a% g& R, h4 W! B4 |. i( Q
INSERM, 2 avenue L6on Bernard, 35043 Rennes, France |
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