Transplantation of involved psoriatic and nonpsoriatic human skin onto congenitally athymie (nude) mice has been performed successfully. Although biopsies at selected intervals demonstrate that the excess glycogen deposition normally seen in psoriasis is no longer consistently present, the psoriatic grafts did retain the usual characteristic histologic differences throughout the life of the animal, up to 11 weeks. This grafting procedure potentially represents a useful method whereby the study of psoriasis can be made in a nonhuman, living system

G.G. Krueger

Dean D. Manning

James Malouf

Bruce Ogden

Wortis

Cantrell

Flanagen

Manning

Reed

Rygaard

Billingham

Marks

Goldschmidt

Voorhees

Pilgrim

Braun-Falco

Krueger, G.G.

Manning, Dean D.

Malouf, James

Ogden, Bruce

Elsevier - Publisher Connector 

Long-Term Maintenance of Psoriatic Human Skin on Congenitally Athymic (Nude) Mice 

Ajuntament de Barcelona

Repositori Obert de Coneixement de l'Ajuntament de Barcelona

Gaseta municipal de Barcelona. Any 079: Índex (1992)

Gaseta municipal de Barcelona. Any 080: Índex (1993)

THE JOURNAL OF INVESTIGATIVE DERMATOLOGY, 64:307-312, 1975 
Copyright© 1975 by The Williams & Wilkins Co. 
Vol. 64. No.5 
Printed in U.S.A. 
REPORTS 
LONG-TERM MAINTENANCE OF PSORIATIC HUMAN SKIN ON 
CONGENITALLY ATHYMIC (NUDE) MICE 
G. G. KRUEGER, M.D., DEAN D. MANNING, PH.D.*, JAMES MALOU>t, AND BRUCE 0GDENt 
Division of Dermatology, Department of Medicine, University of Utah College of Medicine, Salt Lake City, Utah 
Transplantation of involved psoriatic and nonpsoriatic human skin onto congenitally 
athymic (nude) mice has been performed successfully. Although biopsies at selected intervals 
demonstrate that the excess glycogen deposition normally seen in psoriasis is no longer 
consistently present, the psoriatic grafts did retain the usual characteristic histologic 
differences throughout the life of the animal, up to 11 weeks. This grafting procedure 
potentially represents a useful method whereby the study of psoriasis can be made in a 
nonhuman, living system. 
Further insight into the pathogenesis of psoriasis 
as well as the development of new treatment 
programs, topical or systemic, has been hampered 
by the lack of an animal model for psoriasis. This 
paper describes a potenital model in which human 
psoriatic skin is maintained on the congenitally 
athymic (nude) mouse. 
Nude (nu/nu} mice are unique in that they are 
congenitally a thymic and thus are unable to mount 
thymus-dependent immune responses, e.g., cell-
mediated rejection of a foreign graft, as well as the 
antibody production for most antigens. Nude is a 
mutant allele of the nu locus of the VII linkage 
group, is recessive, and is being put onto inbred 
backgrounds by repeated backcrossing [1]. Under 
non-germ-free states, nude mice develop at a near 
normal rate for approximately 3 to 4 months, then 
characteristically they develop wasting which 
manifests as rapidly progressive weight loss and 
death [2,3]. Surgical procedures. anesthesia, etc., 
seem to hasten the onset of this wasting phenome-
non [4]. 
Recently there have been two reports of the 
long-term maintenance of normal human skin 
transplants on the nude mouse [5, 6]. On the basis 
of these observations, we conducted a pilot project 
to determine whether similar maintenance could 
Manuscript received October 10, 1974; in revised form 
December 9, 1974; accepted for publication December 13, 
1974. 
This work was supported in part by grants from the 
Dermatology Foundation, Syntex Summer Fellowship, 
and USPHS Grant AI ll625 01. 
• National Institutes of Health Postdoctoral Fellow 
A155024, Montana State University, Bozeman, Montana. 
tMedical students, University of Utah College of 
Medicine, Salt Lake City, Utah. 
Reprint requests to: Dr. G. G. Krueger, Division of 
Dermatology, The University of Utah Medical Center, 
Salt Lake City, Utah 84132. 
be accomplished with transplanted psoriatic skin. 
A more definitive project was then carried out 
which standardized the variable of thickness of 
grafts, i.e., amount of dermis included. Common to 
both studies after transplantation were the reduc-
tion of some of the features of psoriasis and the 
persistence of the typical psoriasiform acanthosis 
for the life span of the animal, up to at least 11 
weeks post grafting. 
MATERIALS AND METHODS 
Initially each of 13 nude mice on a BALB/c background 
had an 8-mm punch biopsy of involved psoriatic skin (10) 
and noninvolved psoriatic skin (3) from 1 of 3 living 
psoriatic donors transplanted onto a graft bed. Prior to 
grafting, varying amounts of the dermis were trimmed so 
that the thickness of the human graft approximated the 
thi~kness of the mouse skin. Grafts were secured in the 
graft bed utilizing the casting technique of Billingham 
[7]. 
Following the initial study. 11 particularly healthy· 
appearing nude mice, also on a BALB/c background, 40 
to 50 days of age, were used as recipients for donor grafts 
of both noninvolved psoriatic skin (NIPS) and involved 
psoriatic skin (IPS) from another 3 patients with psoria-
sis. All mice were housed away from other animals, 
maintained on autoclaved Purina 5010C feed and acidi-
fied-chlorinated water, and bedding that was sterilized 
and changed weekly. These procedures were imple-
mented to keep the nude mice relatively pathogen free in 
an attempt to lengthen their expected survival. 
Informed consent was obtained from the psoriatic 
subjects, and IPS and NIPS donor specimens 20 mm 
wide, 36 mm long, and 0.4 mm thick were taken 
aseptically under local anesthesia with a Castroveijo 
electrokeratome as described by Voorhees et al [8]. To 
prevent ripping of the edges during removal, a sterile 
template 20 x 36 mm was placed on the skin and a very 
superficial cut with a scalpel made along each edge, 
approximately 0.5-0.7 mm in depth. The specimen was 
placed in a sterile Petri dish with Minimal Essential 
Medium for transport to the lab, donor graft wounds were 
307 
308 KRUEGER ET AL 
covered with sterile Vaseline-impregnated gauze and 
wrapped with a Kling dressing. 
The skin specimens were placed on a sterile cork 
board, stretched and pinned in place, and 4 round, 1-cm 
grafts were taken from each specimen with a sharp, 1-cm 
sterile punch. The remaining donor scraps were fixed in 
95% ethyl alcohol and histologic sections prepared to 
serve as a control of the thickness of the graft as well as to 
determine the degree of acanthosis and parakeratosis, 
Figure 1 is representative of these donor NIPS and IPS 
specimens. Periodic acid-Schiff (PAS) stains with amy-
lase hydrolysis were also made to determine the amount 
of glycogen in both the initial IPS and NIPS specimens. 
In these experiments we used a new grafting procedure 
which is much faster than conventional casting tech-
niques of Billingham [7] and induces less wasting in the 
nude mice. This technique, which we have reported in 
detail elsewhere [4]. is described here briefly {Fig. 2). 
Mice were anesthetized with intraperitoneal sodium 
pentobarbital dosage according to weight-dose scale [9]. 
Recipient graft beds, slightly larger than the donor graft, 
were then prepared, right thorax for the IPS and left 
thorax for the NIPS. Grafts on each animal were from the 
same donor. Donor grafts were secured in place with 
Permabond 102 cement (Pearl Chemical Company, To-
kyo) and covered with a Band-Aid trimmed to size. 
Band-Aids were removed at day 7, and 2- to 3-mm sliver 
biopsies (Fig. 2D) were tsken at 2, 4, and 6 weeks post 
FIG. L A: NIPS-Noninvolved psoriatic skin, B: IPS-
Involved psoriatic skin. Both 0.4 mm thick, prepared from 
scraps of donor specimen at the time of grafting. 
Vol, 64, No, 5 
grafting while the animal was under pentobarbital anes-
thesia. These biopsies were fixed in 95% ethyl alcohol, 
and PAS as well as H & E histologic sections were 
prepared. 
RESULTS 
Initial studies, Five of the 13 initial grafts were 
technical failures which were felt to be due to 
either an excessively thick graft with subsequent 
inadequate perfusion, or slipping of the graft from 
the graft bed during casting, both resulting in 
necrosis of the graft. Four out of 13 mice developed 
the severe wasting peculiar to nude mice and died 
shortly after the grafts were placed; thus, no 
interpretation was possible in these animals, The 
remaining 4 mice had successful grafts. One such 
graft with evident psoriatic acanthosis 11 weeks 
after transplant (the longest surviving animal) is 
shown microscopically (Fig. 3). Superficial biop-
sies [10] of these successful grafts showed some 
parakeratosis, but very few "halo nuclei" peculiar 
to scale of psoriasis [11 ], suggesting that this 
technique would not be useful in determining 
whether the transplanted skin still exhibited typi-
cal psoriasis. Further, it was apparent that we 
could not distinguish between the noninvolved 
psmiatic grafts and the involved psoriatic grafts on 
a macroscopic basis. 
This initial study was encouraging enough to 
justify a second, more definitive study, using 11 
more animals and the methods described above. 
All results reported hereafter are from this second 
experiment. 
Animal and graft survival. Seven of 11 animals 
survived at least 6 weeks post grafting; 1 died at 
day 1, 2 died at approximately 4 weeks, and 1 was 
sacrificed at 5 weeks after grafting. The 10 animals 
surviving at least 4 weeks after grafting all had 
successful grafts, both grossly and microscopically, 
Human skin which appeared ''normal" macroscop-
ically was present in all 20 grafts placed; an 
example is illustrated. in Fig. 2D. 
The changes which occurred in the grafts as they 
healed in place were: ( 1) thin crust formation 
(7/20) and what appeared to be a "ghost" of stra-
tum corneum: {2) on occasion (l/20) a necrotic 
crust formed. Both types of crust sloughed by day 
14, and normal-appearing human skin was seen. 
The necrotic crust rarely (1/20) occurred with the 
0.4-mm shave biopsy of donor skin, but was very 
common in our initial study, where the dermis was 
trimmed manually. By day 14, the grafts appeared 
grossly as they were to remain for the rest of the 
animal's life. 
Gross appearance, No gross difference between 
IPS and NIPS grafts could be detected at any time 
after grafting. There was never evidence of graft 
rejection, i.e., shriveling and necrosis, after a graft 
was healed in place. 
Histology. Sliver biopsies from NIPS and IPS 
grafts were obtained every 2 weeks. Animal #6 at 4 
weeks (NIPS) and animals #6 and #11 at 6 weeks 
May 1975 LONG·TERM MAINTENANCE OF PSORIATIC SKIN 309 
FIG. 2. A: NIPS donor graft in place. B: MIPS graft secured in place with cyanoacrylate cement. C: Band-Aid in 
place to protect graft. D: IPS graft site at 4 weeks immediately after removal of sliver biopsy. 
FIG. 3. Cross-section IPS graft at 11 weeks at 25:<: 
arrow points to mouse skin. 
(both IPS and NIPS) had no remaining human 
skin due to overaggressive biopsies at an earlier 
date. Data in the Table demonstrate the findings 
in a summary form. 
In the psoriasis grafts, all animals had typical 
psoriasiform acanthosis of the epidermis at some 
time during the sequential biopsying. Such a series 
from IPS is seen in Figure 4, which represents both 
the typical (Figs. 4A and 4B) and the atypical (Fig. 
4C) acanthosis seen. Figure 5 is the NIPS and is 
representative of the histology seen. 
Figure 6 shows the junction of IPS to mouse 
epidermis to be quite distinct. The human epider-
mis is many cell layers thick, while the mouse 
epidermis is only 2 to 3 cell layers thick. The 
granular layer of the nude mouse is different from 
the human in that the granules in the mouse 
epidermis appear to not be as distinctly intracellu-
lar as in humans (Fig. 7). 
PAS stains of IPS at the time of grafting 
revealed excess glycogen accumulation which was 
amylase hydrolyzable in all specimens. The NIPS 
skin showed no PAS granules. Figure 8 demon-
strates the finding of glycogen in both an IPS and 
NIPS biopsy. Attempts to grade the amount of 
glycogen present in the biopsies by the PAS stain 
on a scale of 0-4 did not result in substantial 
differences between the involved and uninvolved 
groups (see Table). 
Biopsies taken early (2 weeks) showed an in-
310 KRUEGER ET AL 
FrG. 4. Sliver biopsies from :3 different IPS grafts dem-
onstratin!( the variation in acanthosis at 68;,:. A: IPS at 4 
weeks. animal #1. B: IPS at 6 weeks, animal #2. C: IPS at 
2 weeks. animal #7; arrou: points to mouse-human junc-
tion. 
creased number of fibroblasts in some specimens, a 
phenomenon which decreased with time. 
DISCUSSION 
Not all of the biopsies from IPS grafts revealed 
the acanthosis typical of that seen in psoriasis. 
Other investigators have noted that within any 
given plaque of psoriasis there may be areas 
Vol. 64, No.5 
without the typical histologic changes of psoriasis 
[12,13]. This. plus the problem of improper ori-
entation during embedding, may explain the occa-
sional failure to demonstrate the typical pso-
FIG. 5. Sliver biopsy from 2 different NIPS grafts 
demonstratin>: variations seen histologically at 74'. A: 
NIPS at 4 weeks, animal #L B. NIPS at 2 weeks, animal 
#7. 
FIG. 6. IPS graft at 4 weeks: arrow points to junction 
of mouse and human skin I x 250.l. 
May 1975 
FtG. 7. A: IPS at 2 weeks. animal #1 ( z :>50). B: IPS at 
2 weeks, animal #l ( x 7701. Note granules of upper epi-
dermis. C: Mouse skin of animal #1 ( 350). D: Mouse 
skin of animal #1 ( x 770). Note difference in granules of 
upper epidermis. 
FIG. 8. A: NIPS. B: IPS. Both at 4 weeks post graft, 
460 ~" PAS stain; arrows point to glycogen deposits. 
riatic acanthosis in some of our biopsies. lt should 
be emphasized that all of the animals had typical 
psoriatic acanthosis in at least 2 of the IPS biopsies 
taken over the 6-week period. 
Since inflammation can result in parakeratosis 
[14], the presence of parakeratosis in 9 of 23 of the 
NIPS biopsies may be attributed to the inflamma-
tion of the healing process of the graft as well as 
LONG-TERM MAINTENANCE OF PSORIATIC SKIN 311 
inflammation secondary to healing from previous 
biopsy sites. The presence of parakeratosis in 12 of 
24 IPS biopsies is not markedly different from the 
presence of parakeratosis in the NIPS group. Not 
recorded, but paralleling the disapperance of para-
keratosis, was the reappearance of the granular 
layer. 
If glycogen persisted in the epidermal cells of 
IPS grafts it might indicate a decrease in intracel-
lular cyclic AMP, a finding which in some laborato-
ries has been seen in psoriasis [15]. The fairly good 
relationship between parakeratosis and the pres-
ence of excess glycogen in 30 out of 46 versus no 
relation in the remaining 16 out of 46 suggests that 
these parameters are related. This led to the 
conclusion that even though there is psoriatic 
acanthosis in the IPS biopsies, the excess glycogen 
accumulation normally seen in psoriasis probably 
reverts to a more normal state, i.e., decreased to 
normal levels. Perhaps necessary host factors are 
not present in the nude which are needed to 
maintain all of the typical characteristic features 
of psoriasis. Evidence to support this is the fact 
that the nude in the non-germ-free state goes into 
wasting at about 3 to 4 months of age [3], and a 
general state of nutritive deficiency develops which 
could be a factor in not keeping the IPS grafts 
"fully psoriatic." 
The presence of glycogen, usually with accom-
panying parakeratosis, demonstrates that some of 
our NIPS grafts appear to take on some psoriatic 
changes without the acanthosis. Reasons for this 
are unclear unless thev are also related to the 
inflammatory response, associated with healing. 
The sliver biopsies may have induced uninten-
tional inflammation even though attempts were 
made to biopsy away from previous sites. Each 
previous biopsy site appeared to be well healed 
prior to new biopsies. 
The unlikely possibility that in this study mouse 
epidermis built on a grafted human epidermal 
skeleton must be addressed. This hypothesis would 
suggest that mouse epidermal cells flow in from the 
edge and replace the human epidermal cells one by 
one until all that is left is mouse epidermal cells on 
TABLE. Histology of grafts 
' Psoriasiform . I Parakeratosis I Glycogen 
Biopsy time acanthosis 
I NI 1- l I Nl I I NI 
Initial 11/11 0/111 11/11 0/11 I 11/11 I 0/ll 
2 Weeks 8/JO 0/10, 5/10 )5/lO I 8/10 I!0/10 
4 Weeks 8/8 0/1 I 4/8 2/7 , /8 5/7 
6 Weeks 4/6 o/6 3/6 2/6 1 3/6 4/6 
I ~ involved (IPS) 
Nl ~ noninvolved (NIPS) 
Numerator ~ number of grafts showing effect 
Denominator ~ number of grafts showing human skin 
histologically 
312 KRUEGER ET AL 
a human skeleton. The points of evidence against 
this are: 
a. The granular layer of mouse epidermis is 
different from that of human skin {see Fig. 7). 
b. Gross appearance of the graft complete with 
Langer's lines appear totally human (see Fig. 3). 
c. Distinct histologic differences can be seen at 
the margins where human and mouse skin meet 
(see Fig. 6). This has been noted previously [5, 6). 
d. Implantation of a thymus gland causes 
human xenografts on nude mice to be rejected [16]. 
This should not be possible unless the skin re-
mained human. 
The presence and significance of antihuman 
antibodies in nude mice grafted with human skin, 
of the type reported in nudes carrying human 
tumors [1), are uncertain. One of us {D.M.) has 
attempted to demonstrate these antibodies unsuc-
cessfully {unpublished results). 
REFERENCES 
1. Wortis HA: Immunological studies of nude mice, 
Contemporary Topics in Immunology. vol B. 
Edited by MD Cooper, NL Warner. New York, 
Plenum, 1974, pp 243-263 
2. Cantrell JC, Jutila JW: Bacteriologic studies on 
wasting disease induced by neonatal thymectomy. 
J Immunol 104:79-85, 1969 
3. Flanagen SP: Nude, a new hairless gene with pleio-
tropic effects in the mouse. Gen Res 8:295-301. 
1966 
4. Manning DD, Krueger GG: Use of cyanoacrylate 
cement in skin grafting congenitally athymic 
(nude) mice. Transplantation (in press) 1974 
5. Reed ND, Manning DD: Long term maintenance of 
normal human skin on congenitally athymic 
Vol. 64, No.5 
(nude) mice. Proc Soc Exp Bioi Med 143:350-353, 
1973 
6. Rygaard J: Skin grafts in nude mice. 3. Fate of grafts 
from man and other taxonomic classes. Acta Pathol 
Microbial Scand 82:105-112. 1974 
7. Billingham RE: Chapter 1, Transplantation of Tis-
sues and Cells. Edited by RE Billingham, WK Sil-
vers. Philadelphia, Wistor Institute, 1961. pp 1-17 
8. Marks R, Dawber RPR: In situ microbiology of the 
stratum corneum. Arch Derma to! 105:216-221, 
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ER: Decreased cyclic AMP in the epidermis of 
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1972 
11. Pilgrim HI, DeOme KB: Intraperitoneal pentobarbi-
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12. Cox AJ, Watson W: Histological evidence of the 
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13. Braun-Falco 0: Dynamics of growth and regression 
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14. Graham JH, Johnson WC, Helwig EB: Dermal 
Pathology. Hagerstown, Harper and Row, p 972 
15. Voorhees JJ, Duell EA, Stawiski M, Harrell ER: 
Cyclic nucleotide metabolism in normal and pro-
liferating epidermis, Advances in Cyclic Nucleo-
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origin on congenitally athymic (nude) mice. J Exp 
Med 138:488-494, 1973 


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Long-Term Maintenance of Psoriatic Human Skin on Congenitally Athymic (Nude) Mice

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Long-Term Maintenance of Psoriatic Human Skin on Congenitally Athymic (Nude) Mice

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