Angiogenesis and the skin

Metformin: A Potential Treatment for Acne, Hidradenitis Suppurativa and Rosacea

Metformin is a widely used drug for treatment of diabetes mellitus, due to its safety and efficacy. In addition to its role as an antidiabetic drug, numerous beneficial effects of metformin have enabled its use in various diseases. Considering the anti-androgenic, anti-angiogenic, anti-fibrotic and antioxidant properties of metformin, it may have the potential to improve chronic inflammatory skin diseases. However, further evidence is needed to confirm the efficacy of metformin in dermatological conditions, This review focuses on exploring the therapeutic targets of metformin in acne vulgaris, hidradenitis suppurativa and rosacea, by studying their pathogeneses.

A Comparative Study on Two Types of Porcine Acellular Dermal Matrix Sponges Prepared by Thermal Crosslinking and Thermal-Glutaraldehyde Crosslinking Matrix Microparticles

Common commercial porcine acellular dermal matrix (PADM) products take the form of a thin membrane. Given its dense structure, delaying vascularization after implantation remains an issue to be solved. In addition, overlaying multiple sheets to address deep wounds and large tissue defects that are difficult to repair by self-tissues could hinder tissue ingrowth, angiogenesis, and integration. Here, we creatively prepared PADM microparticles through a homogenizing treatment and crosslinked them to ADM sponges by thermal crosslinking (VT-ADM) and thermal-glutaraldehyde crosslinking (GA-ADM). The resulting VT-ADM was thicker than GA-ADM, and both maintained the natural dermal matrix microstructure and thermal stability. The porosity of GA-ADM (mean 82%) was lower than that of VT-ADM (mean 90.2%), but the mechanical strength and hydrophilicity were significantly higher. The two types of ADM sponges showed no obvious difference in cell adhesion and proliferation without cytotoxicity. Furthermore, the human adipose stem cells were co-cultured with ADM sponges which promoted proliferation, tube formation, and migration of endothelial cells, and the GA-ADM group exhibited better migration behavior. There were no markable differences among expressions of pro-angiogenesis genes, including vascular endothelial growth factor, insulin-like growth factor-1, and epidermal growth factor. In a nude mouse model, the VT-ADM and GA-ADM pre-cultured with human adipose stem cells for 1 week in advance were implanted subcutaneously. The VT-ADM and the GA-ADM showed great histocompatibility without local redness, swelling, or necrosis. The vascular density of the local skin flap above the material was visualized using indocyanine green and showed no statistical difference between the two groups. The collagen tissue deposition in the pores and vessel formation within the sponges increased with time. Although VT-ADM had a higher degradation rate in vivo, the integrity of the two scaffolds was preserved. Collectively, the VT-ADM and the GA-ADM retained a natural matrix structure and presented biocompatibility. Thus, the above-mentioned two crosslinking methods for ADM sponges are safe and practicable. The novel ADM sponges with good physicochemical and biological properties are no longer limited to membrane tissue regeneration but could also realize structure remodeling where they act as scaffolds for a soft tissue filler and three-dimensional reconstruction of the tissue with strength requirements.

Wound closure, angiogenesis and antibacterial behaviors of tetracalcium phosphate/hydroxyethyl cellulose/hyaluronic acid/gelatin composite dermal scaffolds

Polymeric and tetracalcium phosphate (TTCP)-containing polymeric scaffolds were fabricated using a freeze-drying technique, with a homogenous solution of hydroxyethyl cellulose (HEC)/hyaluronic acid (HA)/gelatin (G) or suspension of 15 or 20% TTCP) particles in HEC/HA/G solution. The morphology, phase composition, chemical bands, and swelling behavior of the scaffold were determined. In vitro fibroblast cell viability and migration potential of the scaffolds were determined by MTT, live/dead staining, and scratch assay for wound healing. The in vivo chick embryo angiogenesis test was also carried out. Finally, the initial antibacterial activity of the scaffolds was determined using Staphylococcus aureus. The scaffolds exhibited an enormous porous structure in which the size of pores increased by the presence of TTCP particles. While the polymeric scaffold was amorphous, the formation of low crystalline hydroxyapatite phase and the initial TTCP particles was determined in the composition of TTCP-added scaffolds. TTCP increased swelling behavior of the polymeric scaffold in PBS. The results demonstrated that the amount of TTCP was a crucial factor in cell life. A high concentration of TTCP could restrict cell viability, although all the scaffolds were nontoxic. The scratch assessments determined better cell migration and wound closure in treating with TTCP-containing scaffolds so that after 24 h, a wound closure of 100% was observed. Furthermore, TTCP-incorporated scaffolds significantly improved the angiogenesis, in the chick embryo test. The presence of TTCP had a significant effect on reducing the bacterial activity and 20% TTCP-containing scaffold exhibited better antibacterial activity than the others.

Complications of Sclerotherapy

Sclerotherapy is the systematic, targeted elimination of intracutaneous and subcutaneous varicose, reticular, telangiectasias by the injection of a locally irritating chemical substance, called a sclerosant. The endpoint of this process is functionally analogous to surgical removal of a vein. However, regardless of the best of intentions, complications can and will occur with enough sclerotherapy treatments. Complications resulting from sclerotherapy can be divided into the following categories for ease of explanation: (1) frequent but transient, (2) rare but self-limited, and (3) rare but major. This article will focus on select complications in sclerotherapy, review the most common complications observed, and discuss how to minimize these in daily practice.

The cellular proliferative phase of the wound repair process

The proliferative--or new-tissue formation--phase of wound healing is complex. This article examines the changes that occur to cells during this stage and the effect on the extracellular matrix environment.

The skin in pregnancy

BACKGROUND

Physiologic skin changes are common during pregnancy due to a temporary shift in hormonal, metabolic, and immunologic factors. Physicians may mistake normal skin changes in pregnancy as pathologic change within the skin, and so an appreciation of the common and less common skin manifestations will assist in appropriate patient care.

OBJECTIVE

This review highlights the normal physiologic skin changes in pregnancy, which include pigmentary changes, changes to the hair and nails, alterations in glandular activity, vascular and hematological changes, cutaneous tumors, and mucous membrane changes.

CONCLUSION

Physiologic changes to the skin in pregnancy can be complex and confusing. Pregnancy can be a stressful time for women so it is imperative that physicians be aware of the normal skin changes during pregnancy in order to prevent unnecessary investigations and treatments.

Estrogen and progesterone receptors: their role in postsclerotherapy angiogenesis telangiectatic matting (TM)

BACKGROUND

Postsclerotherapy neoangiogenesis telangiectatic matting (TM) occurs in up to 24% of individuals treated by sclerotherapy. Although the etiology is unknown, obstructive flow factors, angiogenic factors, estrogen, inflammatory, and endogenous factors have all been postulated to play a role in its pathogenesis.

OBJECTIVE

The aim of the study was to ascertain the presence or absence of estrogen and progesterone receptors in postsclerotherapy TM lesions and thus substantiate their possible role in the pathogenesis of TM.

METHODS

Ten women, median age 37.7 years, were included in the study population who developed TM following a single sclerotherapy treatment session employing Sotradecol 0.25% for class I-II telangiectasia/venulectasia. Four of 10 patients had a history of previous hormonal therapy or pregnancy in the previous 12 months prior to entering into the study. Three millimeter punch biopsies were taken at 12 weeks posttreatment and assayed for estrogen and progesterone receptors by the ERICA and PRICA (estrogen/progesterone immune cytochemical assay) techniques.

RESULTS

Zero of 10 patients were positive for estrogen/progesterone receptors as assayed by the ERICA/PRICA technique in biopsied sites of postsclerotherapy TM.

CONCLUSION

Although estrogen and progesterone may play an indirect role in the development of postsclerotherapy TM via vasodilatory or secondary angiogenic or cytokine release mechanisms, they do not appear to play a primary role in promoting postsclerotherapy neoangiogenesis as demonstrated in this study.

Effect of cultured endothelial cells on angiogenesis in vivo

The purpose of this study is to evaluate the effect of cultured endothelial cells on angiogenesis in vivo. Endothelial cells obtained from thoracic aorta of male Wistar rats were cultured in thermoresponsive dishes, which are tissue culture polystyrene dishes bound with thermoresponsive poly (N-isopropylacrylamide). Using the thermoresponsive dishes, a confluent layer of endothelial cells can be detached as an intact sheet by low temperature treatment. The obtained sheets of cultured endothelial cells were grafted to 3 x 3 cm full-thickness skin defects that had been made on the backs of rats in combination with either free skin grafts or artificial dermis grafts. Histologic examinations were performed. The findings showed that, with each of the grafting procedures, the number of vessels in a unit area (1.0 x 10(-4) mm2) was significantly larger in the group with transplantation of cultured endothelial cells. This result suggests that the cultured vascular endothelial cells exert an angiogenic effect at the graft site.

Quantification of vascularity in nodular melanoma and Spitz's nevus

Spitz's nevi are acquired benign melanocytic skin tumors. Usually they are differentiated from nodular melanoma by clinical and histopathological criteria. Since Spitz's nevi are one of the most common simulators of nodular melanomas their bizarre histopathology may cause diagnostic confusion and make it difficult to differentiate these two melanocytic tumors. One of the histologic features shared by Spitz's nevus and nodular melanoma is prominent vascularity. The ability of malignant melanoma to induce angiogenesis is well established whereas benign melanocytic tumors do not have a prominent overall vascularity. The purpose of this study was to find out whether the degree of vascularity of nodular melanomas differs significantly from that of benign Spitz's nevi. In this study the number of microvessels and the vessel area were determined in 23 Spitz's nevi and 16 nodular melanomas. The number of microvessels and the vessel area were determined on Ulex Europaeus agglutinin I-stained sections by computer-assisted image analysis. Two methods of measurement were used, namely systematic and selective sampling. Measurement of the whole tumor specimen (systematic sampling) revealed a vessel count of 10.83/field (SD +/-5.97) for Spitz's nevi whereas nodular melanomas exhibited a significantly lower (p=0.04) vessel count of 6.44/field (SD +/-3.85). This difference was even more pronounced when the vessel area (Spitz's nevi: 17.85x10-4mm2, SD +/-10.32; nodular melanomas: 7.88x10-4mm2, SD +/-5.23) was investigated (p < 0.001). The difference in vessel area and vessel count was insignificant for areas exhibiting the greatest vascularity (selective sampling). Measurement of vessel count and vessel area lead us to conclude that Spitz's nevi have a significantly higher vascularity than do nodular melanomas. Our results thus indicate that angiogenesis in these pigmented lesions is not correlated with malignancy.

A model of growing vascular structures

Increasing attention is being paid to the configuration and development of vascular structures and their possible correlations with physiological events. The study of angiogenesis in normal and pathological states as well as in embryo and adult has provided new insights into the mechanism of vessel growth and organization of the vasculature. Various mathematical branching models have been developed. These constructions are mainly geometrical and only involve a branching phenomenon. We propose the use of a deterministic non-linear model based on physiological laws and hydrodynamics. Growth, branching and anastomosis, the three actual main events occurring in vascular growth, are included in this model. Space growth, including cells and vessels, is defined by a decreasing transformation. Space density and the length of new sprouts are controlled by a set of parameters. The conditions on these parameters are well established, which allows the production of realistic patterns.

Angiogenesis

The formation of new blood vessels, angiogenesis, is a complex process which is central to normal development and homeostasis. However, uncontrolled angiogenesis plays a critical role in both inflammatory and neoplastic disorders. Our understanding of angiogenesis has expanded greatly over the past two decades due to the development of in vivo and in vitro models to study this important process. A variety of cytokines and growth factors have been shown to induce new blood vessel formation in vivo, and in vitro studies have been able to define whether agents have direct or indirect effects upon vascular endothelial cells. Our improved understanding of the mechanisms which regulate angiogenesis has now created important opportunities for the development of new therapies for the treatment of inflammatory and neoplastic skin disease.

Immunohistochemical assessment of tumor vascularity in recurrent Clark II melanomas using antibody to type IV collagen

Thin melanomas, measuring 0.76 mm or less, are generally associated with an excellent prognosis. However, a certain subset of these seemingly innocuous lesions have been reported to develop recurrences. Therefore, the predictive values of currently accepted prognostic indicators have been questioned in thin melanomas. Several studies concerning tumor vascularity in melanoma and certain non-melanocytic malignancies suggest that the degree of vascularization correlates with growth rate and biologic aggressiveness. In the present study, we determined the vascularity of a small group of Clark level II melanomas that resulted in recurrence, and compared these results to an equal number of nonrecurrent lesions with similar prognostic indicators. Blood vessels were labeled by immunoperoxidase staining techniques for Type IV collagen, and quantified by image analysis. No statistical difference was found between the two groups when mean blood vessel counts and percent vascular area were measured. The recurrent tumors had a mean PVA of 4.68 compared to 4.34 for the nonrecurrent group (p = 0.677). The mean blood vessel count beneath the recurrent group was 29.6 per 400 x field, and the corresponding value for the nonrecurrent group was 31.8 (p = 0.681). Our data is preliminary within this limited group of tumors, yet it suggests that tumor vascularity is not a distinctive prognostic indicator by which eventual outcome can be predicted in thin Clark level II malignant melanomas.

Cutaneous necrosis, telangiectatic matting, and hyperpigmentation following sclerotherapy. Etiology, prevention, and treatment

BACKGROUND

Telangiectatic matting and hyperpigmentation are some of the most commonly observed side effects of sclerotherapy. Cutaneous necrosis is relatively rare and often of limited sequelae but most commonly related to extravasation of sclerosant. Physicians treating varicosities and telangiectasia by sclerotherapy must be familiar with causes and means for minimization of all three side effects.

OBJECTIVE

This review article discusses the proposed etiology, risk factors, approach for minimizing, and suggested treatment for the three side effects of cutaneous necrosis, telangiectatic matting, and hyperpigmentation.

RESULTS

Cutaneous necrosis may occur with the injection of any sclerosing agent even under ideal circumstances and does not necessarily represent physician error. When sclerosant extravasation occurs, dilution must occur immediately. Telangiectatic matting is a recognized complication occurring in approximately 15-20% of patients treated by sclerotherapy. Although the exact mechanism of the phenomena remains unknown, reactive inflammatory and/or angiogenic mechanisms are felt to play a role. Patients are advised that telangiectatic matting is usually not permanent and usually resolves spontaneously in 3-12 months. Postsclerosis pigmentation is defined as the appearance of persistent, increased pigmentation running the course of an ectatic blood vessel treated by sclerotherapy. The general incidence of hyperpigmentation ranges from 10 to 30%. Although hyperpigmentation may persist for months, its presence rarely deters patients from continuing treatment. Spontaneous resolution occurs in 70% at 6 months with 99% resolution occurring within 1 year.

CONCLUSIONS

With understanding the etiology, risk factors, and ways to minimize these side effects our goal is to reduce their incidence. Attempting prevention may ultimately be the most effective means of treatment. Dermatol Surg 1995;21:19-29.

LEARNING OBJECTIVES

After studying the following article, participant should be able to: 1. Understand the definition and potential causes of cutaneous necrosis, telangiectatic matting, and hyperpigmentation following sclerotherapy. 2. Advise patients prior to treatment on the common risks involved in sclerotherapy and to advise them on the relative incidence. 3. Understand the concept of minimal sclerosant concentration and how it can help the physician to choose sclerosing solution concentrations to minimize risks.

Margin assessment of selected basal cell carcinomas utilizing laser Doppler velocimetry

BACKGROUND

Basal cell carcinomas (BCC) have increased vasculature, therefore, blood flow within the tumor may be greater than normal surrounding skin. We attempted to detect the difference in blood flow between the tumor and uninvolved surrounding skin utilizing laser doppler velocimetry (LDV).

METHODS

Ten patients with 14 BCC were studied. Using LDV, we calculated the size of the tumor based on margin assessment as predicted by the measured difference in blood flow and compared this size with the clinically predicted size and the size of the defect after Mohs micrographic surgery (MMS).

RESULTS

Clinical evaluation of tumor size prior to MMS did not correlate with the size of the surgical defect after MMS; however, correlation was found between the predicted size of the tumor as determined by LDV and the defect after MMS.

CONCLUSIONS

Tumor size of BCC as predicted by measured differences in blood flow using LDV correlated with the size of the surgical defect after MMS. This suggests that LDV was able to detect the difference in blood flow between the tumor and uninvolved surrounding skin.

Organ culture of psoriatic skin: effect of TGF-alpha and TGF-beta on epidermal structure in vitro

Normal skin and uninvolved and involved psoriatic skin specimens were maintained in vitro in organ culture. The 3-4 mm punch-biopsied skin specimens were put freely into the culture medium with or without fetal calf serum, under an atmosphere of 95% O2 plus 5% CO2, and rotated at 60 rpm at 37 degrees C. In the serum-free culture medium (vitamin A-free) granular layers appeared in the involved psoriatic epidermis in culture. Addition of TGF-alpha caused normal skin and uninvolved and involved psoriatic skin specimens to become acanthotic and to degenerate easily almost to the full thickness of the epidermal layer in proportion to increasing concentrations of TGF-alpha as well as with the duration of the culture, but without disappearance of their granular layers. TGF-beta caused the normal skin and uninvolved psoriatic skin specimens to become thinned without disappearance of granular layers, but caused the involved psoriatic skin specimens to be thinned without appearance of granular layers in serum-containing medium or with their disappearance in the serum-free medium. TGF-beta also antagonized the acanthotic and degenerative effect of TGF-alpha. The results suggest that TGF-alpha and TGF-beta may partially be related to the induction of psoriatic epidermal lesions.

Macrophage-derived angiogenesis factors

A majority of angiogenic factors has been shown to be produced by macrophages. This review will give a concise description of their biochemical nature, their isolation from macrophages and their angiogenic activity. Among the factors with mitogenic effects on endothelial cells are basic fibroblast growth factor (bFGF), transforming growth factor-alpha (TGF-alpha) and very probably insulin-like growth factor-1 (IGF-1). Other secretory products such as angiotropin and human angiogenic factor (HAF) are nonmitogenic but promote angiogenesis by inducing migration of endothelial cells. Prostaglandins, platelet-derived growth factor (PDGF), granulocyte-macrophage- and granulocyte-colony stimulating factor (GM-CSF, G-CSF), interleukin 6 (IL-6) and angiotensin converting enzyme (ACE) have also been shown to be angiogenic, but their mode of action is still to be clearly defined. As the extracellular matrix appears to be involved in the control of angiogenesis, macrophage-derived factors that can alter this structure via degradation or via the clotting system will also be discussed. Tumor necrosis factor alpha (TNF-alpha), interleukin 1 (IL-1) and transforming growth factor-beta (TGF-beta) have complex actions on endothelial cells, and can partially inhibit angiogenesis. Among the factors which solely inhibit neovascularization are the interferons. As it is not known whether all of these factors play a role in angiogenesis in vivo attempts to detect them in situ during the course of neovascularization will be described. Finally macrophages will be discussed as cells that may not be mandatory for each phase of the angiogenic process but whose angiogenic capabilities are comprehensive and unsurpassed by any other cell.

Development of angiogenesis inhibitors for clinical applications

Angiogenesis, the development of new blood vessels, is associated with many life-threatening pathologies. The neovascularization of tumors for example, allows a blood supply to deliver the required nutrients for tumor development. Inappropriate blood vessel growth also contributes to the pathology of other diseases such as atherosclerosis and arthritis. The process of angiogenesis is beginning to be better understood, and as Ted Maione and Richard Sharpe explain, this understanding has led to the identification of several lead compounds that inhibit this process. At present all of these candidate drugs exhibit severe host toxicity, but more selective angiogenesis inhibitors might be expected to be extremely useful therapeutic agents.

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.

Does peripheral collateralization also cause collateralization in the canine heart?

1. Experiments were conducted in chronically prepared dogs to determine if gradual obstruction of the proximal femoral arteries would also cause collateralization in the coronary circulation. 2. Peripheral coronary pressure was measured before and after peripheral collateralization as an index of coronary collateral function. Coronary collateral blood flow was measured with radioactive microspheres after peripheral collateralization. 3. Peripheral coronary pressure was not significantly altered by peripheral collateralization. Coronary collateral blood flow measured after peripheral collateralization was similar to that reported in non-collateralized hearts. 4. Results indicated that the mechanism(s) responsible for peripheral collateralization do not act systemically, at least not on the coronary circulation.

Overexpression of transforming growth factor alpha in psoriatic epidermis

Transforming growth factor alpha (TGF-alpha) is produced by and required for the growth of epithelial cells and is angiogenic in vivo. Since epidermal hyperplasia and angiogenesis are hallmarks of psoriasis, TGF-alpha gene expression was analyzed in epidermal biopsies of normal and psoriatic skin. TGF-alpha messenger RNA and protein are much more abundant in lesional psoriatic epidermis than in normal-appearing skin of psoriatic patients or in normal epidermis. In contrast, messenger RNA levels of transforming growth factor beta 1 (TGF-beta 1), which inhibits epithelial cell growth, are not significantly different in normal, uninvolved, and lesional psoriatic epidermis. Thus, psoriatic epidermal hyperplasia may involve increased expression of a keratinocyte mitogen (TGF-alpha) rather than deficient expression of a growth inhibitor (TGF-beta 1).

Wound healing for the dermatologic surgeon

An understanding of the basic science of cutaneous wound repair is essential to the dermatologic surgeon for the management of the postoperative wound. This review discusses the stages of wound healing and then applies these principles to the preoperative, intraoperative, and postoperative management of the surgical patient.