The blood vessels of the skin

Anatomical structures, cell types and biomarkers of the Human Reference Atlas

The Human Reference Atlas (HRA) aims to map all of the cells of the human body to advance biomedical research and clinical practice. This Perspective presents collaborative work by members of 16 international consortia on two essential and interlinked parts of the HRA: (1) three-dimensional representations of anatomy that are linked to (2) tables that name and interlink major anatomical structures, cell types, plus biomarkers (ASCT+B). We discuss four examples that demonstrate the practical utility of the HRA.

The dynamic anatomy and patterning of skin

The skin is often viewed as a static barrier that protects the body from the outside world. Emphasis on studying the skin's architecture and biomechanics in the context of restoring skin movement and function is often ignored. It is fundamentally important that if skin is to be modelled or developed, we do not only focus on the biology of skin but also aim to understand its mechanical properties and structure in living dynamic tissue. In this review, we describe the architecture of skin and patterning seen in skin as viewed from a surgical perspective and highlight aspects of the microanatomy that have never fully been realized and provide evidence or concepts that support the importance of studying living skin's dynamic behaviour. We highlight how the structure of the skin has evolved to allow the body dynamic form and function, and how injury, disease or ageing results in a dramatic changes to the microarchitecture and changes physical characteristics of skin. Therefore, appreciating the dynamic microanatomy of skin from the deep fascia through to the skin surface is vitally important from a dermatological and surgical perspective. This focus provides an alternative perspective and approach to addressing skin pathologies and skin ageing.

Human pigmentation: A side effect adapted from a primitive organism's survival, acting through cell attachment with an affinity for the keratinocyte and for elastin: Part I

Pigmentation featured millions of years ago and perhaps began with an amoeba frightening off a predator with some agent such as dopamine to prevent its attachment for phagocytosis by an enemy. This paper suggests that the environmental forces of grip and stick deserve greater emphasis and that mechanical forces involved in grip and stick or release from attachment, all point to control of proteases underlying pigmentation. There is an affinity for elastin as a pathway for melanin to exit its peripheral location in the epidermis into lymphatics and play a humeral role in defense mechanisms. The hair follicle follows the epidermal-dermal pattern of behavior with an affinity for elastin, a controlling function of melanin and through the bulge, an influence of mechanical forces and control by protease inhibitors.

Clinical evaluation of 168 korean patients with rosacea: the sun exposure correlates with the erythematotelangiectatic subtype

BACKGROUND

Although rosacea is a chronic cutaneous inflammatory disorder that's commonly seen in adults, the etiology and pathogenesis of the illness remain unclear. A well established diagnostic classification and grading system may play a critical role in performing research and it would serve as a diagnostic reference in the clinical field.

OBJECTIVE

We sought to classify the patients with the new standard classification and grading system and we wanted determine the peculiar features and relationships of each subtype. We also analyzed the relationships between the degree of sun exposure and each subtype.

METHODS

We reviewed the medical records and clinical photos of 168 patients who were diagnosed with rosacea from 2002 to 2007 at our hospital. The standard classification and grading system suggested by the National Rosacea Society (NRS) Expert Committee was adopted to evaluate each patient's subtype and the severity.

RESULTS

The male:female ratio was 1:2.29. The mean age at the time of diagnosis was 47.8 years. The mean duration of disease was 3.5 years. Sun exposure and hot baths/exercise were the two most common precipitating factors, while the majority of patients did not have any specific factor that relieved their symptoms. According to the NRS classification and grading system, the patients were classified into four subtypes. One hundred sixty two (96.4%) patients were diagnosed with the erythematotelangiectatic subtype irrespective of severity. Eighty five (50.6%) patients had the papulopustular subtype and 24 (14.3%) patients had ocular rosacea. Eight (4.8%) patients displayed mild phymatous change. The degree of sun exposure had significant correlation with the development and severity of the erythematotelangiectatic subtype (p<0.05), while it had no correlation with the papulopustular, ocular and phymatous subtypes.

CONCLUSION

Although the erythematotelangiectatic subtype was the most common subtype of rosacea, many patients also had other subtypes of rosacea simultaneously. Based on our results, we proved that ocular rosacea is an extension of the clinical spectrum of erythematotelangiectatic rosacea. In addition, the results of our study particularly suggest that sun exposure has a different influence on each subtype of rosacea.

Childhood stye and adult rosacea

BACKGROUND

Little is known about how individuals with a predisposition for rosacea appear in childhood. This retrospective, matched control, longitudinal study examined the relationship between childhood stye and adult rosacea.

METHODS

The records of the Rochester Epidemiology Project were examined to identify patients who received care for stye or blepharitis between ages 2 and 17 years, and received care for any cause at age 40 years or older. Patients were matched by group to control subjects (1:2).

RESULTS

Patients with stye during childhood (N = 201) had a higher prevalence of adult rosacea than did control subjects (5.5% vs 1.5%, P = .01). Patients who had other childhood eye conditions without stye (N = 504) were not at higher risk.

LIMITATIONS

The study population included few minority patients.

CONCLUSIONS

The association between childhood stye and adult rosacea appears to be significant and should be examined further. Rosacea prevalence in adults may be lower (2.1%) than previously reported.

Raynaud’s Syndrome: comparison of late and early onset forms using hand perfusion scintigraphy

Primary Raynaud's disease is generally a disease of younger females; however, there are cases where symptoms present over the age of 40. These cases are described as late onset. In our current prospective study we compared the characteristics of early and late onset types of primary Raynaud's in 127 patients. In addition to the collection of medical records, we performed capillary-microscopy and hand perfusion scintigraphy using Tc-99 m DTPA to evaluate the microcirculation of each patient's fingers. Regarding the spectrum of the capillary-microscopic findings, we did not find any significant difference between the early and late onset forms. However, in hand perfusion examinations done using Tc-99 m DTPA, we measured a significantly lower finger/palm ratio (FPR) in the early onset group of patients. We also observed a correlation between the duration of the disease and the FPR, as well as between the age and FPR. Longer disease duration resulted in a significantly lower FPR. On the basis of our results, we believe that late onset Raynaud's should be treated as a separate entity. Due to its different characteristics found on examination and follow-up of our patients, functional hand perfusion examination should be recommended independently of the age-related characteristics of the disease.

Videocapillaroscopic alterations in erythematotelangiectatic rosacea

BACKGROUND

Rosacea is a common chronic dermatosis that involves the cutaneous microvasculature of the face. There are no objective measures for assessing the severity of erythematotelangiectatic rosacea.

OBJECTIVE

Our purpose was to characterize and provide objective measures of vessel changes in erythematotelangiectatic rosacea by videocapillaroscopy.

METHODS

We compared 30 patients with erythematotelangiectatic rosacea with 30 age- and sex-matched patients with facial seborrheic dermatitis and 30 healthy control subjects. Videocapillaroscopy was performed both on the cheeks and on the nailfold region. The analyzed parameters of the face were morphological (background color, vessel irregularities) and quantitative (polygonal net perimeter, telangiectasia, and vessel diameters).

RESULTS

Characteristic alterations of skin vessels were observed in facial rosacea, with a pattern distinct from that of facial seborrheic dermatitis. In particular, rosacea showed neoangiogenesis and significantly larger polygons (13.21 +/- 3 vs 7.8 +/- 3 mm; mean +/- standard deviation, P < .001), more prominent telangiectases (267.8 +/- 108 vs 118.2 +/- 35 microm; P < .001) and larger mean vessel diameter (46.71 +/- 9 vs 24 +/- 10 microm; P < .001) compared with seborrheic dermatitis. Seborrheic dermatitis displayed more polygon irregularities and vessel tortuosity. In contrast, no differences were found in the nailfold region.

LIMITATIONS

Vessel irregularities and overall erythema may be difficult to quantify.

CONCLUSIONS

Videocapillaroscopy may represent a valid adjunctive method in the early diagnosis and measurement of erythematotelangiectatic rosacea.

Rosacea: I. Etiology, pathogenesis, and subtype classification

Rosacea is one of the most common conditions dermatologists treat. Rosacea is most often characterized by transient or persistent central facial erythema, visible blood vessels, and often papules and pustules. Based on patterns of physical findings, rosacea can be classified into 4 broad subtypes: erythematotelangiectatic, papulopustular, phymatous, and ocular. The cause of rosacea remains somewhat of a mystery. Several hypotheses have been documented in the literature and include potential roles for vascular abnormalities, dermal matrix degeneration, environmental factors, and microorganisms such as Demodex folliculorum and Helicobacter pylori. This article reviews the current literature on rosacea with emphasis placed on the new classification system and the main pathogenic theories. Learning objective At the conclusion of this learning activity, participants should be acquainted with rosacea's defining characteristics, the new subtype classification system, and the main theories on pathogenesis.

Rosacea: current thoughts on origin

Rosacea is a clinical pattern beginning and evolving in the genetically susceptible individual in response to a host of exposures. It produces a variety of clinical presentations, which vary over time and with age. Recently, many specific mediators of rosacea development have been described. A primary genetic cause for rosacea is suggested as single genes often control such mediators: enzymes, neuroendocrine transmitters, and cytokines are found in pathways to rosacea signs and symptoms. Currently, neither a specific cause nor a laboratory indicator of rosacea has been suggested. However, broadening interest in rosacea portends future increase in knowledge.

Expression of endoglin in psoriatic involved and uninvolved skin

Endoglin is a glycoprotein with TGF-beta binding capacity and is predominantly expressed on endothelial cells. In psoriasis, TGF-beta has appeared to play a role in the extravasation of peripheral blood mononuclear cells via the endothelium. In order to find out more about the role of endoglin in psoriasis, immunohistochemical staining with PN-E2, a novel anti-endoglin, and of PAL-E, recognizing vascular endothelium, was carried out in psoriatic involved, psoriatic uninvolved and normal skin. The expression of the antigens was assessed semi-quantitatively using a five-point scale. In psoriatic involved skin, a high endoglin expression was found. In psoriatic uninvolved skin, however, we found that endoglin expression was significantly decreased compared with normal skin. The relevance of these findings to the pathogenesis of psoriasis is discussed.

Carbonic anhydrase--a marker for fenestrated capillaries in psoriasis

A strong correlation between capillary fenestrations and the demonstration of carbonic anhydrase (CA) has previously been shown. In the present histochemical study we sought to determine whether CA could serve as a marker for fenestrated capillaries in psoriasis. In normal human skin capillary staining for CA was found only in the fenestrated capillaries of the perifollicular and periglandular plexus. In psoriatic skin lesions, however, the intrapapillary capillaries also reacted for CA. From ultrastructural investigations it is known that these capillaries are fenestrated. Our findings have shown that there is a strong correlation between fenestrated and CA-positive capillaries in normal human skin as well as in the lesional skin of psoriatics. Therefore, the demonstration of CA activity may serve as a specific and sensitive marker for fenestrated capillaries in psoriasis using an uncomplicated method, which makes it possible to detect numerous fenestrated capillaries in a single histological section.

Reduced hyperaemia following skin trauma: evidence for an impaired microvascular response to injury in the diabetic foot

The hyperaemic response to standard needle injury within dorsal foot skin was investigated in normal and Type 1 (insulin-dependent) diabetic subjects using laser Doppler flowmetry. The normal response was maximal within 15 min, localised, prolonged and biphasic. In 20 normal subjects and three groups of long-duration Type 1 diabetic patients (20 without complications; 20 with laser-treated retinopathy; 15 with neuropathy and retinopathy), the median (interquartile range) peak hyperaemic responses were 1.766 (1.220-1.970), 1.485 (1.342-1.672), 0.997 (0.705-1.203) and 1.030 (0.718-1.369) arbitrary units, respectively. Compared to normal and uncomplicated diabetic groups, peak flow was significantly reduced in the retinopathic (p less than 0.0001) and neuropathic (p = 0.001 and 0.007, respectively) groups. There was no significant difference between the normal and uncomplicated diabetic groups, nor between the retinopathic and neuropathic groups. There was no association of the hyperaemic response with blood sugar, HbA1c, or duration of diabetes. Diabetic patients who have microvascular complications, with or without neuropathy, have an associated impairment of microvascular response to mechanical injury which might predispose to infection and poor wound healing.

Biochemical consequences of mechanical forces generated by distention and distortion

This review includes a number of concepts: (1) mechanical forces are transmitted to cell membranes by adhesion complexes between solid elements in the extracellular environment and the cytoskeleton; (2) the adhesion complexes require inhibition of proteases to maintain their adhesion; and (3) hydrostatic pressure is a mechanical stress on solid elements in the tissues, and it is controlled by the microcirculation and lymphatic system. Hypotheses include the following: (1) mechanical forces act on the cell membrane and induce inhibitors of proteases, thereby maintaining the adhesion complexes; (2) the transduction of chemical signals--protease inhibition--is more flexible in young cells, wounds, and psoriasis. In old tissues, protease inhibition is more sustained; and (3) cell shape, cell migration, and mitosis are in part controlled by such mechanisms. These hypotheses are supported by evidence from the literature and observations from my experience and that of many co-workers in the fields of microcirculation, lymphatic systems, angiogenesis, wound healing, and proteases.

Age-related changes in capillaries of rat oral mucosa. A quantitative electron microscopic study

Ultrastructural age changes in capillaries of the buccal mucosa were examined in montages of cross sections made from electron micrographs at 37,500 x. Six rats aged 6 months and 6 aged 30 months were perfused with glutaraldehyde and conventional thin sections obtained. Two capillaries located within a connective tissue papilla were studied from each rat. Capillaries of the old group differed from those of the young group by statistically significant increases in several parameters. The endothelial cell was increased in thickness, especially in the vicinity of junctions. The frequency of pinocytotic vesicles/unit length of the cell circumference was nearly doubled. Junctions were of nearly double length and took a more oblique course. All parts of the basement membranes were thickened, though perhaps less than seems true in skin. In striking contrast to epidermis, the epithelium of oral mucosa undergoes no appreciable thinning with age. We suggest that the observed age increases in frequency of pinocytotic vesicles and in the length of junctions may facilitate blood/tissue exchange, thus compensating for impaired exchange due to the thickened basement membranes. These compensatory changes in conjunction with the unchanged size of the mucosal capillary bed in the aged rat (demonstrated previously) could explain the unchanged thickness of the oral epithelium.

Blood flow and epithelial thickness in different regions of feline oral mucosa and skin

The relationship between epithelial thickness and blood flow was examined in 6 mucosal and 3 skin regions of the cat. Blood flow to these tissues was determined using the radiolabelled microsphere method. From histologic sections the proportion of the tissue biopsy occupied by epithelium and the average epithelial thickness were calculated. The oral tissues had a significantly higher blood flow than the skin regions (p less than 0.05). In terms of epithelial thickness, the tissues could be divided into 4 groups (p less than 0.05). These were: a) palate; b) gingival regions and dorsum of the tongue; c) lip and buccal mucosa; d) all skin regions. When epithelial thickness was related to blood flow there was a significant positive correlation (p less than 0.005) indicating that a thicker epithelium is associated with a higher blood flow. This finding may reflect the greater metabolic demands of the thicker epithelia.

Angiogenesis and the skin

This communication reviews the circumstances of angiogenesis in the embryo and in the adult. Various biochemical and physical factors reported to influence new blood vessel growth are discussed. Particular emphasis is given to angiogenesis occurring in the skin. Evidence concerning an epidermal stimulus for vascular growth is examined.

Age-related changes in the epithelial dimensions and capillaries of the oral mucosa of the rat

Seven homologous regions of the oral mucosa were compared in rats 6, 18 and 30 months of age. Capillaries were visualized by their alkaline-phosphatase activity revealed by an azo-dye. Measurements on tracings of densely-spaced histological sections in two planes perpendicular to the epithelial surface showed epithelial thickness in masticatory mucosa decreased by 18 months, but increased by 30 months. In regions of lining mucosa, thickness increased by 18 months, but decreased by up to 13 per cent at 30 months. The size of the capillary bed increased substantially by 18 months and further increased by 30 months. Variability in the epithelial dimensions increased up to 18 months but not beyond; variability in the capillary measurements showed no change with age. The quantitative relationship between epithelial thickness and the size of the epithelial-connective tissue interface and the capillary bed remained unchanged with age.

A study of uniaxial tension on the superficial dermal microvasculature

A spring-loaded apparatus was designed to apply uniaxial tension to forearm skin in 17 human subjects--10 normals, 6 psoriatics, and 1 patient with scleroderma. Simultaneously, the effects of stretching on the upper dermal vasculature were observed stereomicroscopically. Progressive changes (collapse) in the superficial microvasculature--vertical capillary loops and horizontal subpapillary plexus--with increasing tension were photographed. Force and strains were recorded at the points of disappearance of virtually all vessels. An average force of 11.9 newtons (N), accompanied by a mean strain of 10.3%, resulted in occlusion of all vessels. A much higher force (18.5 N) was necessary to occlude blood flow in the 1 patient with scleroderma. In summary, we have described a new technique for the study of mechanical forces on the blood supply of the epidermis. The data have shown that uniaxial tension has important effects on the superficial dermal microvasculature, resulting in impedance and obliteration of blood flow at relatively low magnitudes.

Epithelial dimensions and capillary supply in the oral mucosa of the rat

Subdividing the cheek, palate and ventral tongue into seven anatomically identifiable regions enabled us to assess relationships that were previously obscured by the great heterogeneity of rat oral epithelium. Capillaries were visualized by an alkaline phosphatase azo dye method in oral mucosa of four 3-month old male rats. Basal layer length per unit surface length showed a statistically significant relationship with the thickness of the epithelial cell layer in all seven regions. Linear regression of mean regional length of basal layer on mean thickness of the cellular layer in the seven regions was statistically highly significant. This was true also for mean capillary length. Thickness of the cellular layer, length of the basal layer and capillary length were similar in a palatal ruga and a thick region of cheek, suggesting that epithelial thickness rather than the type of mucosa influences the magnitude of these values. Proportional reductions in all three variables were observed in a second region of cheek and a region of ventral tongue, supporting this suggestion.

The fibrinolytic activity of human oral epithelium and epidermis

The fibrinolytic activity of normal human oral epithelium and abdominal epidermis was studied by two techniques. With fibrinolytic autography, dorsal tongue, ventral tongue, cheek, palate and gingival sulcus epithelium showed fibrinolytic activity but oral gingival epithelium and the epidermis showed no activity. With a fibrin plate technique, potassium thiocyanate extracts of epidermis and oral epithelium all showed strong fibrinolytic activity, but activity in tris buffer extracts was demonstrable only with oral epithelium, and the activity was much weaker. The fact that the tris buffer extractable fibrinolytic activator was demonstrated only in oral epithelium suggests that the presence of this activator in epithelium is related to the type of keratinization and/or its rate of cell turnover.

Human dermal microvasculature: I. Its segmental differentiation. Light and electron microscopic study

Light microscopic examination of I micrometer thick epoxy resin sections of human skin preserved in fixative normally used for electron microscopy allows division of the microvasculature of the reticular and superficial dermis into several distinct segments. More precise delineation of these components can be achieved by correlative study using electron microscopy. Measurement of vessel diameter in tissue sections is of limited value in vessel classification because there is a wide overlap between different vascular segments and the results are influenced by the type of fixative used for processing the tissue. Detailed observation of the morphological characteristics of the endothelium and its investment, including the elastic and basal laminae, is consider preferable for identifying individual vascular segments. Differences in body region do not appear to have any obvious influence on vessel structure although there are regional differences in vessel density and arrangement. In comparison with earlier studies on animal tissues or human skin, no structures resembling arteriovenous shunts or precapillary sphincters were observed in the present investigation. However, closed fenestrae and other structures thought to be transendothelial channels were often found at the tips of capillary loops adjacent to the epidermis.

Isolation and growth of endothelial cells from the microvessels of the newborn human foreskin in cell culture

A procedure for the isolation and in vitro cultivation of endothelial cells from the microvessels of the newborn human foreskin dermis is described. The epidermis was removed from foreskin tissue using a Castroviejo keratotome (0.1 mm shim). Endothelial cells were released from the dermal vessels by trypsinization of 5 mm2 sections of dermis at 37 degrees C for 40 min. Cells were expressed into Minimal Essential Medium (MEM) containing 10% pooled human serum, collected by centrifugation and plated onto either a plain plastic or a fibronectin treated culture surface. In primary culture the rate of endothelial cell proliferation was dependent upon serum type and concentration being optimal in 50% pooled human serum. High serum concentration in combination with pretreatment of the culture surface with fibronectin was required for maximal proliferation rate, for the cells to achieve confluence and for subcultivation. Primary and subcultured cells were characterized as endothelial by light microscopic, immunofluorescent (Factor VIII associated protein) and ultrastructural (Weibel-Palade body) criteria.

Growth and morphology of rabbit marginal vessel endothelium in cell culture

A procedure for the isolation and cultivation of endothelium from the marginal vessels of the rabbit ear is described. Endothelial cells, isolated by slow perfusion with a trypsin solution, are cultured in minimal essential medium supplemented with 10% fresh rabbit serum for up to 6 mo. In primary culture, marginal vessel endothelial cells grow in an expanding circular pattern with closely apposed cell membranes. Weibel-Palade bodies, subcellular organelles unique to endothelial cells in situ, are present in both primary and in serially cultivated cells (12 passages). In intact skin, Weibel-Palade (W-P) bodies are observed in the perinuclear cytoplasm in close proximity to the cell membrane facing the vascular lumen. 8-16 tubules of 200 A diameter are present in each body. In primary and subcultured cells, W-P bodies of identical size are seen in the vicinity of the Golgi apparatus and in close proximity to the outer cell membrane. At the optimum serum concentration (10%), a cell doubling time of 72-96 h is observed. When growth in normal rabbit serum and in platelet-poor serum is compared, a slower growth rate is observed in the absence of platelets, suggesting that factors released by platelets affect endothelial cell proliferation. However, addition of crude platelet factor does not substitute for complete serum. Fibroblast growth factor is not mitogenic for rabbit marginal vessel endothelium in vitro.

Reactive angioendotheliomatosis

Angioendotheliomatosis is a rare disorder with both cutaneous and systemic clinical presentations. We agree that there is evidence in the existing medical literature for the separation of reactive and malignant (neoplastic) variants of angioendotheliomatosis. These variants share similar histologic and ultrastructural features but seem clinically distinct. The reactive variant has been associated (four of seven cases, including our patient) with existing or preexisting subacute bacterial endocarditis.

Patterns of activation and inhibition of fibrinolysis in the normal skin of rat, guinea pig, and rabbit

The distribution and intensity of fibrinolytic activity and of inhibitors of fibrinolysis in the normal skin of the rat, guinea pig and rabbit were studied with histochemical techniques. Rat skin exhibited the highest overall fibrinolytic activity and rabbit skin the lowest, with guinea-pig intermediate. The distribution of fibrinolytic areas differed in the different species. The fibrinolytic activity was caused by an activator of plasminogen related to the blood vessels or in some instances (mainly in the rabbit) to the epidermis. The ability to inhibit plasmin was highest in guinea pig skin and lowest in rat skin, with rabbit skin intermediate. In all 3 species the inhibition was related chiefly to the muscular layer. Epidermis was an additional source of inhibition.