intermediate filament proteins in adult human arteries

Intermediate Filament Proteins in Adult Human Arteries

BENGT JOHANSSON,1,2 ANDERS ERIKSSON,2 ISMO VIRTANEN,3AND LARS-ERIC THORNELL1*

1Department of Anatomy, Umeå University, Umeå, Sweden2Department of Forensic Medicine, Umeå University, Umeå, Sweden

3Institute of Biomedicine, Department of Anatomy, University of Helsinki, Helsinki, Finland

ABSTRACT Background:The cytoskeleton of cells in blood vessel wallscontains desmin, vimentin, and cytokeratins. The distribution of theseproteins in human vessels is not fully known. We have mapped thedistribution of intermediate filament proteins in human arterial walls.Methods: Monoclonal antibodies targeted at the intermediate filament

proteins desmin, vimentin, and cytokeratins were used, and the distribu-tion of these proteins was studied by immunohistochemistry.Results: In the muscular arteries, most smooth muscle cells in the media

expressed both desmin and vimentin; in the elastic arteries, the propor-tion of desmin-labelled cells was lower and preferentially located to theperiphery of the media. In general, the desmin immunoreactivity withinthe intima was weak, but some smooth muscle cells and smooth musclecells in the musculoelastic layer showed strong immunoreactivity. Thevasa vasorum exhibited a heterogeneous desmin-labelling pattern. Thevimentin antibodies labelled the endothelium and showed a heteroge-neous staining pattern in the other layers of the arterial wall. Cytokeratinwas detected in occasional cells in themedia ofmuscular arteries, inmanyadluminal cells and cell clusters in the coronary intima, and in smoothmuscle cells in the media of the elastic arteries.Conclusions: Vimentin is widely distributed in vascular smooth muscle

cells, whereas the distribution of desmin and cytokeratin varies. Eachartery studied had an intermediate filament pattern typical for theanatomical location. There were no interindividual variations in the dis-tribution of intermediate filament proteins. Anat. Rec. 247:439–448, 1997.r 1997 Wiley-Liss, Inc.

Key words: immunohistochemistry; adult; man; arteries; desmin; vimen-tin; cytokeratin

All eukaryotic cells express intermediate filamentproteins related to cytoskeletal functions. Approxi-mately 40 different intermediate filament proteins areknown, and these have been grouped into six classes onthe basis of sequence homologies (Skalli et al., 1992).These proteins are multigene products and thus auseful tool in cell biology to distinguish major celllineages (Osborn andWeber, 1986).Vascular smooth muscle cells, the principal cellular

component of the arterial wall, express mainly vimen-tin, typical of cells of mesenchymal origin. In addition,many smooth muscle cells also express desmin, theintermediate filament protein of muscular cell lineages(Desmouliere and Gabbiani, 1992). Furthermore, thepresence of cytokeratin, mainly expressed in epithelialtissues, has been observed in some vascular smoothmuscle cells (Kuruc, 1988; Jahn and Franke, 1989).Data on intermediate filament proteins in vascular

tissues are mainly from studies on human and animalaortic tissue, but information on other human vessels isscarce and restricted to a few reports (Table 1). To the

best of our knowledge, no systematic investigation of alarge number of normal human arteries has beenpublished. We have performed such a study, investigat-ing the distribution of intermediate filament proteins indifferent parts of the normal human arterial system.The arteries included in this study are prone to developatherosclerosis, are distributed throughout the body,and are easy to obtain at a routine autopsy. Further-more, the material represents both elastic and muscu-lar arteries and low- and high-pressure arterial sys-tems. The results will form a broader basis for theunderstanding of possible alterations along the humanvascular system and for further studies of developmen-tal, physiological, and pathological changes.

Received 24 July 1995; accepted 8 November 1996.*Correspondence to: Prof. Lars-Eric Thornell, Department of

Anatomy, Umeå University, S-901 87 Umeå, Sweden.Contract grant sponsor: Umea University; Contract grant sponsor:

SwedishMedical Research Council; Contract grant sponsor: Norrland-ska Hjartfonden.

THE ANATOMICAL RECORD 247:439–448 (1997)

r 1997 WILEY-LISS, INC.

MATERIALS AND METHODS

Human arteries were obtained from six males, aged19–26 years, 12–48 hr after death. All individuals werepreviously physically healthy and had died a suddenaccidental death. Material from the aorta on 5–7 lo-cations, the truncus pulmonalis, the a. cerebri media, a.basilaris, a. coronaria dx et sin, a. renalis, and a. pro-funda femoris, was rapidly frozen in liquid propanethat had been precooled in liquid nitrogen. Tissue-tecO.C.T. compound (Miles Inc., Elkhart, Indiana) wasused as embedding medium. After storage at 280°C,5-µm-thick serial sections were obtained in a Reichert-Jung 2800 Frigocut cryostate at 225°C and processedfor immunohistochemical staining according to theperoxidase–antiperoxidase (PAP) technique (Stern-berger, 1979). In brief, the tissue specimens were airdried for 20–30 min and then incubated with 5%normal rabbit serum (Dakopatts, Copenhagen, Den-mark) for 15 min to inhibit unspecific staining. Thesections were then incubated with the appropriateprimary antibody for 60 min at 37°C. The primaryantibody was added in 0.1 M phosphate buffered saline

(PBS) with 0.01% bovine serum albumin. After incuba-tion, the sections were washed in 0.01 M PBS for 15min, followed by incubation with rabbit anti-mouseperoxidase-conjugated IgG (Dakopatts) for 30 min atroom temperature. Development of peroxidase stainingwas obtained by applying diaminobenzidine and H2O2for 10–15 min, followed by rinsing in running water for5 min. The sections were dehydrated in graded concen-trations of ethanol, followed by xylene, and mountedwith DPX (BDH, Poole, UK). For control stainingprocedures, the primary antibodywas omitted. Further-more, adjacent myocardial and central nervous system

TABLE 1. Overview of the reports on intermediate filament proteins in normal blood vessels, antibodies used,and vessels and species studied

ReferenceAnti-body Aorta

Truncuspulmonalis

Arteriacoronaria

Arteriarenalis

Arteriafemoralis

Arteria cerebrimedia andbasilaris Other vessels Species

Kocher andGabbiani(1986)

DV H H H

Thornell et al. (1986) DV H vasa vasorum (H)Osborn et al. (1987) DV H H H H a. carotis (H)Nikkari et al. (1988) DVC H (fetal)Bader et al. (1988) DVC umbilical ves-

sels (H)Nikkari et al. (1989) DV H a. thoracica

interna (H)Von Roggendorf andKunzig (1992)

DV H

Gabbiani et al. (1981) DV HA rat, cow, pig,rabbit

Berner et al. (1981) DV HA hamsterSchmid et al. (1982) DV HA cow, rat,

chickenOsborn et al. (1981) DV A A A A a. carotis,

vein (H)rat

Berner et al. (1981) DV A A A vein ratGabbiani et al. (1982) DV A ratKocher et al. (1984) DV A ratKocher et al. (1985) DV A rat1D, desmin; V, vimentin; C, cytokeratin;H, human;A, animal.

TABLE 2. Distribution of the intermediate filament proteins in different arteries as detected by antibodies againstvimentin (V9), desmin (des.), and cytokeratin (PKK1)1

Aorta A. coronaria Basal cerebral arteries A. renalis A. profunda femoris

V9 des. PKK1 V9 des. PKK1 V9 des. PKK1 V9 des. PKK1 V9 des. PKK1

Intima 111 1 2 111 1 1 111 1 2 111 (1) 2 111 (1) 2PGR 111 1 1ME 111 11 1

Media 111 1 (1) 111 1(1) (1) 111 111 2 111 11 2 111 11(1) 2Adv 11 2 2 111 2 2 111 2 111 1 2 111 1 2

1111, Staining in all cells; 11(1), staining in almost all cells; 11 and 1(1), staining in many cells; 1, strong staining in few cells or weak staining inmany cells; (1), staining in occasional cells;2, no staining. PGR, proteoglycan-rich layer;ME,musculoelastic layer;Adv, avdentitia.

TABLE 3. Schematic presentation of the distributionof the different vimentin antibodies1

V9 FV16DF8 FV21DH9 FV24BA6

Intima 111 1–11 1 1Media 111 11 2 11Adventitia 111 1–11 1 1

1111, Strong staining;11, moderate staining;1–11, weak tomoderatestaining;1, weak staining or staining in some cells;2, no staining.

440 B. JOHANSSON ET AL.

tissue served as internal controls of the immunohisto-chemical stainings. In addition, secondary antibodieslabelled with fluorescein isothiocyanate (FITC) andtetramethyl rhodamine isothiocyanate (TRITC) wereused in some sections, mainly to obtain details ongroups of cells in the adventitita of the a. profundafemoris and the a. renalis. The antibodies againstdesmin (Virtanen et al., 1986), vimentin (V9, FV16DF8,FV21DH9, FV24BA6; Kjorell et al., 1987), and cytoker-atins (PKK1; Virtanen, 1985) have been described. Inbrief, the FV16DF8 reacts with smooth muscle cells inbovine arterial media but only weakly in the intima;FV24BA6 stains capillaries, endothelium, and smoothmuscle cells in intramyocardial vessels; and FV21DH9preferentially stains the endothelium in bovine largevessels (Kjorell et al., 1987). The sections were viewedand photographed in an Olympus VanoxAH-2 photomi-croscope.

RESULTS

Except for the different vimentin antibodies, theresults of the immunohistochemical stainings will bepresented for each individual artery. An overview of theantibody labelling is presented in Table 2.

Vimentin

The staining pattern of different vimentin antibodieswas the same in all vessels; Figure 1A–D shows anexample of an elastic artery, and Figure 2 showsmuscular arteries represented by a coronary artery. Anoverview of the vimentin antibody labelling is pre-sented in Table 3.The V9 labelled the cells within the intima, virtually

all smooth muscle cells in the media, and virtually allcell types in the adventitia (e.g., Figs. 1A, 2A). Thestaining intensity in the intima was uniform and did

Fig. 1. Transverse sections of the inner (A–F) and the outer (G–I)halves of the wall of the aorta abdominalis stained with antibodiesagainst vimentin (V9) (A, G), (FV16DF8) (B), (FV21DH9) (C),(FV24BA6) (D), cytokeratin (PKK1) (E,H), and desmin (F,I). The V9antibodies stain cells in all layers of the aortic wall (A, G), FV21DH9

stain the endothelium and cells in the adventitia (C), and FV24BA6stain the endothelial cells and some smooth muscle cells in the media(D). Both cytokeratin and desmin were seen in few smoothmuscle cellsin the luminal part and in many smooth muscle cells in the outer partof the media (E,F,H,I). i, intima; m, media; a, adventitia, 3100.

441IF PROTEINS IN HUMAN ARTERIES

not vary intra- or interindividually. The FV16DF8antibody exhibited the same staining pattern as V9, butthe labelling was generally weaker (Fig. 1B, 2B). TheFV21DH9 antibody labelled endothelial cells and someof the smooth muscle cells in the adventitia, whereascells in the intima and media showed very weak or nostaining (Figs. 1C, 2C). The FV24BA6 antibody labelledendothelial cells and some of the smooth muscle cells inthe media. Otherwise, staining was weak in the intimaand almost absent in the adventitia (Figs. 1D, 2D).

Aorta and Truncus Pulmonalis

In the intima of the elastic arteries, desmin stainingwas generally weak, but some cells were stronglystained. The proportion of cells that stained for desminwas low in elastic arteries, and these cells were prefer-entially located in the outer third of the media (Fig. 1F,1I). In a few specimens, strongly labelled cells werelocated in the subintimal region of the elastic arteries(not shown). At all levels of the aorta, the desmindistribution was the same. Weak cytokeratin labelling

was seen, with the highest number of stained cells inthe outer half of the media.

Arteriae Coronariae

Awell-developed intima with a clear subdivision intoa proteoglycan-rich layer and a musculoelastic layer(Stary et al., 1992) was seen in half of the subjects (Fig.3A, B). In other cases, this subdivision was not obvious.When a musculoelastic layer could be identified in thecoronary arteries, many longitudinally oriented smoothmuscle cells were strongly labelled with the desminantibody (Fig. 3B). In the proteoglycan-rich layer and inordinary intima, the desmin labelling was generallyweak. Some cells were, however, strongly stained withthe desmin antibody (Fig. 3C). Many cells in the mediaexpressed desmin, and the highest staining intensitywas observed in the outer part of the media (Fig.3B,C,E). The PKK1 antibody stained some cells in theintima of the coronary arteries. These cells were eithersingle or in clusters and were often located in the innerpart of the intima or near the lamina elastica interna(Fig. 3F). Only occasional cells in the media werelabelled with the PKK1 antibody.

A. Basilaris and A. Cerebri Media

The intima of the cerebral arteries was thin andconsisted of few cells other than the endothelial cells.Desmin was detected in all cells in the media. ThePKK1 antibody did not label cells in the media (Fig. 4).

A. Renalis and A. Profunda Femoris

Both arteries had a thin, almost acellular, intima. Inthe a. renalis, many medial smooth muscle cells werelabelled with desmin antibodies. Labelled cells werehomogeneously distributed in the media (Fig. 5B). Inthe media of the a. profunda femoris, a slightly highernumber of cells was labelled and homogeneously distrib-uted. In the periphery of the adventitial layer of the a.renalis and the a. profunda femoris, desmin was oftendetected in single cells or in groups of cells. Vimentincould not be detected in these cells (Fig. 5B,E,F).

Vasa Vasorum, Endocardial Smooth Muscle Cells, andSmall Intramyocardial Vessels

The small blood vessels in the adventitia, mostly thevasa vasorum, showed variable desmin expression. The

Fig. 2. Transverse sections of a coronaria dx stained with antibodiesagainst vimentin (V9) (A), (FV16DF8) (B), (FV21DH9) (C), and(FV24BA6) (D). The V9 and FV16DF8 antibodies stain cells in alllayers of the vessel (A,B), FV21DH9 stain the endothelium and cells inthe adventitia (C), and FV24BA6 stain the endothelial cells and somesmooth muscle cells in the media (D). Lumen 5 upper parts of A–D.3100.

Fig. 3. Transverse sections of the r. interventricularis anterior (a.coronaria sin.) (A–C,F) and a diagonal branch of the r. interventricu-laris anterior (D–E) stained with antibodies against vimentin (V9)(A,D), desmin (B,C,E), and cytokeratin (F). Antibodies against vimen-tin strongly stain cells in all the layers of the main vessel (A). Desminantibodies stain many smooth muscle cells in the media and thesmooth muscle cells in the musculoelastic layer of the intima, whereasonly faint staining is seen in the outer part of the intima (B,C).Clusters of smooth muscle cells strongly stained with the desminantibody are often seen in the intima, close to themedia (arrows, C). Inthe branch, where the intima is thin, colocalization of vimentin anddesmin is seen only in the media (D,E), but desmin staining showsgreat variability (E). The small vessel in the lower right (D,E) stainswith antivimentin but only faintly with antidesmin. The cytokeratinantibodies stain cells in the luminal part of the intima of the mainvessel and sometimes clusters of smooth muscle cells in the intima(arrows, F). Only occasional smooth muscle cells in the media arelabelled (lower right, F). p, proteoglycan-rich layer of the intima; me,musculoelastic layer of the intima; m, media; a, adventitia. 3100 inA,B,D,E, 3200 in C,F.


Fig. 3.


most common pattern was that some smooth musclecells expressed both desmin and vimentin (Fig. 6D).However, some of the vasa vasorum exhibited strongdesmin labelling, with a high proportion of desmin-positive cells (Fig. 6B). Endocardial smoothmuscle cellswere intensely stained both with vimentin and desminantibodies (Fig. 6E, F). Some of the smooth muscle cellsin the intramyocardial vessel were labelled with des-min antibodies (Fig. 6G). The proportion of labelledcells increased with increasing vessel diameter.In control experiments, where the first antibody was

omitted, no staining was seen.

DISCUSSION

Our results show that each artery exhibited a distri-bution of intermediate filament proteins in its tunicamedia, typical for its anatomical location. Major differ-ences were seen between the elastic and the musculararteries, but heterogeneity was also seen among themuscular arteries. Vimentin was the main type ofintermediate filament protein in both muscular andelastic arteries, whereas desmin was more widely dis-tributed in the muscular arteries than in the elasticarteries. Because expression of desmin is considered as

Fig. 4. Transverse sections of the a. cerebri media (A,B) and a branchof the a. basilaris (C,D) stained with antibodies against vimentin (V9)(A,C) and desmin (B,D). InA, the endothelial cells of the intima (i), themedia (m), and cells in the adventitia (a) are stained. In B, only smoothmuscle cells in the media are stained. A group of longitudinallyoriented subintimal cells, near a splitted lamina elastica interna,

express vimentin but generally not desmin (A,B, arrows). In thebranch, the media contains circular and longitudinal smooth musclecells (C,D). Note the weaker staining of the circular smooth musclelayer in D. The small vessel (short arrows) in the lower right and thesmall nerve in the lower left (long arrows) both stain with antivimen-tin but not with antidesmin. 3200.


a hallmark ofmuscular differentiation (Lazarides, 1980),this variation probably reflects differences in the myo-cyte function between the two types of arteries. Amongthe muscular arteries, the proportion of desmin-containing cells was higher in the a. profunda femorisand in the basal cerebral arteries than in the a. renalisand the a. coronariae.The peripheral location of desmin in the media of

elastic arteries was an almost constant finding. Similarobservations on adult human aortas have beenmade bysome investigators (Kocher and Gabbiani, 1986; Thor-nell et al., 1986) but not by others (Osborn et al., 1987),who also reported a high proportion of desmin-labelledcells in the aortic media. In the bovine aorta, strands ofcells in the outer part of the media that express desmin

only have been reported (Schmid et al., 1982). Incontrast to this peripheral location in adults, the firstdesmin-expressing cells in the embryonal abdominalaorta were seen in the subintimal region (Nikkari et al.,1988). It is not known when the transition to the adultpattern occurs, but this matter is currently underinvestigation.In the rat aorta, an increasing number of desmin-

expressing cells from the arcus to the iliac arteries hasbeen reported (Osborn et al., 1981). In addition, aheterogeneous distribution along the aorta of elastinand collagen gene expression has been observed in thepig (Davidson, 1985), and a gradient of smooth musclemyosin has been reported in man (Frid et al., 1993).However, we did not detect such a gradient of desmin in

Fig. 5. Transverse sections of a. renalis (A,B), a. profunda femoris(C,D), and the adventitia of the a. renalis in larger magnification(E,F), stained with antibodies against vimentin (V9) (A,C,E) anddesmin (B,D,F). The antibodies in the adventitia of a. renalis arevisualized with TRITC-labelled secondary antibodies (E,F). Vimentinis seen in all wall layers. The desmin antibodies stain the media,

although somewhat heterogeneously, and groups of cells in the adven-titia of the a. renalis (B,F) but not in this specimen of a. profundafemoris (D). These groups of cells in the adventitia of the a. renalis(E,F) express desmin but not vimentin (arrows). 3100 in A–D, 3200in E,F.


the human aorta, despite the fact that we carefullyinvestigated this issue.Smooth muscle cells expressing desmin are often

located in the outer half of the media in the coronaryarteries, a feature not described in the only previous

report on intermediate filaments in human coronaryarteries (Kocher and Gabbiani, 1986). Our findings inthe coronary arteries with a peripheral location ofdesmin-labelled cells is analogous to the distribution inthe aorta. A possible explanation may be the close

Fig. 6. Transverse sections of vasa vasorum of a. coronaria dx (A,B)and r. interventricularis anterior (a. coronaria sin.) (C,D), an endocar-dial region (E,F), and a small intramyocardial vessel (G,H). Themediaof a. coronaria dx (A,B) and r. interventricularis anterior (C,D) is seenin the upper part of the figure. The sections are stained withantibodies against vimentin (V9) (A,C,E,G), and desmin (B,D,F,H).Vimentin antibodies stain cells in the vasa vasorum (A,C). Antibodiesagainst desmin stain the smooth muscle cells of the vasa vasorum

heterogeneously (B,D). Endocardial bundles of smooth muscle cells(stars) are stained with both the vimentin (E) and the desmin (F)antibodies. In addition, the vimentin antibodies stain other endocar-dial cells and the myocardial capillaries (E). Myocytes are stained onlywith desmin (F). In the small intramyocardial vessel, the vimentinantibodies label cells throughout the wall (G), whereas the desminantibodies detect only a few smooth muscle cells in the media (arrows,H). 3100 inA–D, 3200 in E,F, 3400 in G,H.


relation to the aorta and a gradual transition from anelastic artery to a muscular artery. Reports on interme-diate filament proteins in animal coronary arteries arescarce. In the rat, homogeneous distribution of desmin-labelled smooth muscle cells has been reported (Osbornet al., 1981), but when illustrating this statement witha figure, the vessel is represented by an intramyocar-dial artery.In a. basilaris and a. cerebri media, desmin was

homogeneously distributed throughout the media, andall smooth muscle cells were labelled. In a previousstudy, where the tissues were fixed in formalin, desminwas observed in the entire media but with strongeststaining in the outer part of the media (von Roggendorfand Kunzig, 1992). To the best of our knowledge, thereare no data on intermediate filament proteins in animalcerebral arteries.In the renal artery, many cells in the media were

stained and homogeneously distributed. In a previousreport, a similar homogeneous distribution was de-scribed, but the proportion of labelled cells was notreported (Osborn et al., 1987).The cytoskeletal features of the a. profunda femoris

have not been described before. There are, however,reports on the closely related a. femoralis. In thesereports, a high proportion of desmin-labelled cells (37%;Kocher and Gabbiani, 1986) and ‘‘relative high ratios’’(Osborn et al., 1987) have been described. We foundthat almost all cells in the media of the a. profundafemoris were labelled and that these cells were homoge-neously distributed throughout the media. However,these vessels may not be comparable with respect tocytoskeletal proteins, even if they are anatomicallyclosely related.Asparse desmin content in the human aortic (Schmid

et al., 1982; Thornell et al., 1986) and coronary (Nikkariet al., 1989) intima has been reported. Conversely, ahigh desmin expression in the smooth muscle cells inthe intima of the a. thoracica interna (Nikkari et al.,1989) has been observed. In our material, the desminlabelling of cells in the aortic intima and in the proteo-glycan-rich layer of the coronary intima was weak andonly few cells were strongly stained, whereas almost allsmooth muscle cells in the musculoelastic layer of thecoronary intima were strongly stained. Presence orabsence of desmin may reflect two different types ofsmooth muscle cells. As previously reported, there aretwo phenotypes of vascular smooth muscle cells, onerich in myofilaments and the other with well-developedcell organelles for protein synthesis (Dilley et al., 1987;Campbell et al., 1988). Desmin may be a marker of theformer type.Cytokeratins are the intermediate filament proteins

of epithelial cells. However, two subtypes (8, 18) ofcytokeratin have been reported to be expressed invascular smooth muscle cells under certain conditions.The presence of cytokeratin has been observed inhuman embryonal vascular tissues (van Muijen et al.,1987; Kuruc, 1988), human umbilical cord (Bader et al.,1988; Jahn and Franke, 1989), intimal thickenings, anddifferent atherosclerotic lesions (Jahn and Franke,1989; Jahn et al., 1993). The PKK1 antibody, known byimmunoblot to react with cytokeratins 8, 18, and 19(Miettinen et al., 1985), labelled some smooth musclecells in the coronary intima, many cells in the aortic

media, but only some cells in the media of the musculararteries. Thus, the PKK1 antibody detected antigens insmooth muscle cells in the media of the elastic arteriesbut not in muscular arteries. However, the staining inthe elastic arteries was weak, indicating sparse expres-sion of the antigen. This result is in agreement with aprevious report that failed to demonstrate the presenceof cytokeratin in paraffin-embedded human aorta whenusing the same antibody (Huitfeldt and Brandtzaeg,1985). The PKK1 staining pattern in the coronaryintima was variable but in general included cells closeto the lumen, cells on both sides of the lamina elasticainterna, and clusters of cells. Smooth muscle cellsexpressing cytokeratin may be in a proliferative state(Gown et al., 1988; Jahn and Franke, 1989). Becauseproliferation of smoothmuscle cells is a key event in thedevelopment of atherosclerosis, cytokeratin expressionmay be related to atherosclerotic disease.The vimentin antibodies used in this investigation

also exhibited heterogeneous staining in the vasculartissues. The V9 and FV16DF8 antibodies labelled cellsthroughout the vascular wall, FV21DH9 labelled endo-thelial and adventitial cells, and FV24BA6 labelledendothelial cells and smooth muscle cells in the media.These results are in line with previous observations onbovine intramyocardial vessels (Kjorell et al., 1987).Although vimentin is a product of a single gene (forreferences, see Kjorell et al., 1987), different antigenicproperties of the vimentinmolecule in the different walllayers seem to exist. This variation may be related tovariations in the vimentin molecule, e.g., due to post-translational modification, or to different masking ofthe epitopes.The vasa vasorum exhibited heterogenous desmin

staining, which may reflect different functions of theindividual small vessels in the adventitia, but furtherinvestigations are needed to clarify this issue.Vascular smooth muscle cells differ from visceral

ones in the expression of intermediate filament pro-teins, where the latter contain desmin only (Gabbianiet al., 1981). This general difference was valid also forthe arteries investigated by us, even if we cannot ruleout that a few smooth muscle cells express desmin only.However, groups of adventitial smooth muscle cells insome muscular arteries expressed desmin only, whichmay indicate a different embryonal origin of these cells.Endocardial smooth muscle cells, the function of whichis poorly understood (Terasaki et al., 1993), exhibitedthe intermediate filament proteins characteristic ofvascular smooth muscle cells.

ACKNOWLEDGMENTS

Financial support was provided by Umeå University,the Swedish Medical Research Council, and Norrland-ska Hjartfonden. Skillful technical assistance was pro-vided byMonikaKarlsson, Lena Soderberg, Anna-KarinNordlund, Gudrun Furtenbach, and Bror Berggren.

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intermediate filament proteins in adult human arteries

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