Z. Zellforsch. 93, 249--253 (1969)

Mitochondrion-Desmosome Complexes in Human Hepatocytes*

I~MIN STERNLIEB

Department of Medicine, Albert Einstein College of Medicine, and Bronx Municipal Hospital Center, Bronx, New York, U.S.A.

Received August 8, 1968

Summary. Mitochondrion-desmosome complexes similar to those seen in other epithelia were observed in hepatocytes from normal and diseased human livers of children and adults. Their occurrence could not be explained by random distribution of mitochondria in the cells. The close associations of mitochondria with desmosomes supported the hypothesis that the latter might be special areas of intercellular ionic diffusion between hepatocytes.

A pecu l i a r associa t ion be tween mi tochondr ia and desmosomes was no ted b y JOYON, MALET and TU~CHI~I (1964) in hepa tocy te s and b y D~AN~ and WUI~Z~L- MANN (1966) in severa l o ther t ypes of epi thel ia l cells of young mice. S imi lar observa t ions have since been made in cells l ining the r ec tum of a t e rmi t e (NOIROT- TXMOTHC, E and NOIROT, 1967) and those of the ep id idymis of the opossum (LADMAN, 1967). The p resen t observat ions , concerning mi tochondr ion-desmosome complexes in h u m a n hepa tocy tes , were made on diagnost ic b iopsy specimens f rom four normal subjects , a boy 14, two girls 12 and 17, and a woman 51 years old ; two girls and five boys wi th Wi l son ' s disease (hepato len t icu lar degenerat ion) , r ang ing in age f rom 21/2 to 16 years ; and one 44-year-old woman with ana lbumin- emia 1. The b iopsy specimens were processed for e lect ron microscopy wi th the a id of me thods which h a d been de ta i led in ear l ier s tudies (STERNLI~B, 1965, 1968).

Junc t iona l complexes near bile canal icul i regular ly conta in desmosomes in the h u m a n l iver (CossEL, 1964). I n add i t i on there are i r regu la r ly sca t t e red i so la ted desmosomes along the la te ra l surfaces of hepa tocy tes , referred to as " s c a t t e r e d de smosomes" in th is paper . A desmosome consists of two dense plaques , each a b o u t 0 .13- -0 .2 ~ long and abou t 2 5 0 - - 3 5 0 / k th ick , connected b y i r regular , fine f i laments . Shor t f i l aments ex tend f rom the desmosomes into the cy top l a sm (Figs. 1, 2). There is ne i ther ano the r special ized s t ruc tu re nor a l ine of condensa- t ion t h a t can be recognized in the in te rspace be tween the two plaques besides the amorphous f i lamentous mater ia l .

* This work was supported in part by United States Public Health Service Grants AI-1059 and TI AM-5384 from the National Institute of Arthritis and Metabolic Diseases, 5 MOI FR 000-50 from the General Clinical Research Center, HD 00674 from the National Institute of Child Health and Development and by a grant from the Life Insurance Medical Research Fund G-65-50.

The author is very grateful to Dr. ALEX B. NOVIXOFF for the use of the facilities of his laboratory (supported by United States Public Health Service Grant CA-06576), to Mr. NELSON QUINTA~x and Mrs. Jv I~ . WINDSOR for their superb technical assistance and to Miss M_A~L~NV, VA~ HOORE~ for preparation of the photographs.

1 The selection of the material for study reflects the interests of this laboratory and obviously should not imply that the finding is characteristic for either Wilson's disease or analbuminemia.

250 I. STERNLIEB:

General ly , mi tochondr ia are sca t t e red th rough the hepa tocy te cytoplasm. W h e n found near the pe r iphe ry of the cell t h e y are separa ted from the p l a sma m e m b r a n e b y some cy top lasm t h a t is free of larger organelles ( " ec top l a sm") . Some of the mi tochondr ia , however, are found close to desmosomes in more per iphera l locat ions t h a n those of mi tochondr ia which are r a n d o m l y sca t te red in hepa tocy tes . Such associat ions develop with e i ther one or wi th two mitochon- dria, resul t ing in b lending of the cy top lasmic f i laments of the desmosomes with the mi tochondr ia l outer membrane (Figs. 1--5) . W h e n two mi tochondr ia are complexed with a single desmosome, a v i r tua l mir ror image of mi tochondr ia appears (Figs. 1, 4).

Of 90 " s c a t t e r e d desmosomes" f rom a series of unselected e lect ron micro- g raphs of hepa tocy tes f rom the group of the 12 subjects used for the present s tudy , 34 desmosomes were associated with one and addi t iona l 17 with two mi tochondr ia . I n contras t , desmosomes of junc t iona l complexes near bile canali- curl were on ly in f requen t ly associa ted with mi tochondr ia , bu t even there such complexes were seen (Figs. 3, 6). Most of the desmosomes associa ted with mi tochondr ia exh ib i ted the usual continuous, paral lel , dense plaques (Figs. 1--3) , bu t in some complexes the p laques seemed to be discont inuous (Figs. 4---6).

The poss ib i l i ty t h a t the associat ion be tween mi tochondr ia and desmosomes was pu re ly the resul t of r andom sca t t e r of the organelles had to be considered. This, however, seemed unl ike ly because first, " s c a t t e r e d desmosomes" were uncommon, ye t more t han half of t h e m was associa ted with mi toehondr ia ; second, the " m i r r o r - i m a g e s " across desmosomes, present in one th i rd of all complexes, were no t observed elsewhere; th i rd , the discont inui t ies of some of the desmosome plaques (Figs. 4, 5) resembled the junc t ions of synap tosomes (GRAY and GUILLERY, 1966). This r a the r inf requent f inding was no ted only in desmo- somes complexed with mi tochondr ia .

The presence of mi tochondr ion-desmosome complexes in epi thel ia f rom fetal t issues and the i r absence in the same tissues f rom adu l t animals , suggested to

Fig. 1. Three mitochondrion-desmosome complexes and portions of three hepatocytes from a biopsy specimen obtained from a 51-year-old control subject. D desmosome; L/lipofuscin; M miteehondrion; Mb microbody; Pm plasma membrane; rEr rough endoplasmic retieulum. OsO4-Veronal acetate, pH 7.4, with 0.25 M sucrose; Epon; uranyl acetate and lead citrate.

• 35,000

Fig. 2. Higher magnification of fragments of two hepatocytes from same subject as in Fig. 1 showing a "scattered desmosome" (D) with two dense plaques on the apposing membranes joined by amorphous, filamentous material in the intercellular space. Cytoplasmic filaments (/) blend with the outer membrane of the mitechondrion (M). Pm plasma membrane. • 87,000

Fig. 3. Portions of two hepatocytes near bile canaliculus (BC) from same subject as in Figs. 1 and 2. Desmosome which is part of junctional complex (JC) is associated with a mitochondrion (M). Pm plasma membrane; R ribosomes; rEr rough endoplasmie retieuinm.

• 35,000

Fig. 4. Portions of two hepatecytes from a biopsy specimen obtained from a 15-year-old girl with Wilson's disease, showing two mitochondrion-desmosome complexes. Note discontinuities in desmosome plaques (arrow) similar to those seen in synaptosomes. Same fixation and processing as in Fig. 1. M mitechondrion; Pm plasma membrane; sEr smooth endoplasmic

reticulum. • 35,000

Fig. 5. Higher magnification of mitochondrion-desmosome complex from Fig. 4. • 87,000

Mitochondrion-Desmosome Complexes in Human Liver 251

Figs. 1--5

252 I. STERNLIEB:

Fig. 6. Portions of two hepatoeytes with part of a bile canaliculus (BC) from a biopsy specimen obtained from a 15-year-old boy with Wflson's disease. Note abnormally dense mitochondrion (M) seen in young patients with Wilson's disease (STE~NLIEB, 1968) near desmosome (D) which is part of junctional complex (JC). Er endoplasmic reticulum; L/ lipofuscin. Same

fixation and staining as in Fig. 1 ; embedded in Araldite. • 35,000

DEANE, WURZELMANN and KOSTELLOW (1966) tha t mitochondria might supply energy or essential metabolites needed for the formation of desmosomes. Con- ceivably the same relationship could exist even in the liver of an adult subject with preferential occurrence of mitochondrion-desmosome complexes in young hepatoeytes. Unfor tunately , however, young hepatoeytes could not be identified reliably by morphologie criteria, thus leaving the question of a possible devel- opmental relationship between mitoehondria and desmosomes unanswered.

I n the light of the experimental evidence tha t desmosomes are special areas of ionic diffusion (LoEw]~NSTEIN, SOCOLAR, HIGASHINO, KANNO and DAVIDSON, 1965; PV, NN, 1966) the present findings suggest tha t a similar process of inter- cellular communicat ion m a y operate across these bridges in human hepatocytes.

The presence in the hepatocytes of normal subjects of mitoehondrion- desmosome complexes indistinguishable f rom those of patients with liver disease indicates t ha t such complexes are probably normal findings in the liver. Moreover, the fact t ha t these complexes have been encountered in a number of different epithelia suggests t ha t - - if searched for - - they will be found in m a n y additional tissues.

R e f e r e n c e s

COSSEL, L.: Die menschliche Leber im Elektronenmikroskop. Jena: Gustav Fischer 1962. DEANS, H. W., and S. WURZELMANN: Mitochondrial-desmosome complexes in various dif-

ferentiating epithelia. In: Proc. 6th Int. Congr. Electron Micro., p. 403--404, Kyoto 1966. - - - - , and A. B. KOSTELLOW: Survey for mitochondrial-desmosome complexes in differen-

tiating epithelia. Z. Zellforsch. 75, 166--177 (1966).

Mitochondrion-Desmosome Complexes in Human Liver 253

GRAY, E. G., and R. W. GUILLERY: Synaptic morphology in the normal and degenerating nervous system. Int. Rev. Cytol. 19, 111--182 (1966).

JoYO~, L., P. MALET et J.-P. TURC~INI: Structures et rapports partieuliers des membranes plasmiques d'h~patocytes de nouveau-n~s. C. R. Acad. Sci. (Paris) 259, 2532--2534 (1964).

LADMA~, A. J . : The fine structure of the ductuli efferentes of the opossum. Anat. Rec. 157, 559--576 (1967).

LOEWENSTEIN, W. I~., S. J . SOCOLAR, S. HIGASItINO, Y. KAZOO, and N. DAVIDSON: Inter- ceUular communication: renal, urinary bladder, sensory and salivary gland cells. Science 149, 295--298 (1965).

NOIROT-TIMOTH~E, C., et C. NOIROT: Liaison de mitoehondries avee des zones d'adh~sion intereellulaires. J. Microscopie 6, 87--90 (1967).

PENN, R. D. : Ionic communication between liver cells. J . Cell Biol. 29, 171--174 (1966). STERNLIEB, I. : Perinuclear filaments and mierotubules in human hepatoeytes and biliary

epithelial cells. J. Microseopie 4, 551--558 (1965). - - Mitochondrial and fatty changes in hepatecytes of patients with Wilson's disease. Gastro-

enterology 55, 354--367 (1968).

IRMIN ST]~RNLIEB~ M. D. Department of Medicine, Albert Einstein College of Medicine 1300 Morris Park Avenue Bronx, New York 10461, U.S.A.