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Neovascularization plays a major role in prosthetic vascular graft healing. New developments in manufacturing biomaterials have encouraged the use of biological and biosynthetic materials for both arterial replacement and bypass procedures. We have analyzed in vivo the process of neovascularization and incorporation of biolized bovine carotid artery (Solco P), a biological material, and the composite of ovine collagen and polyester mesh (Omniflow), a biosynthetic material. The synthetic fabric polytetrafluorethylene (e-PTFE), which is widely used in cardiovascular surgery, served as control. Using the dorsal skinfold chamber of the Syrian golden hamster as site for implantation (n = 15), angiogenesis and neovascularization were analyzed quantitatively by means of intravital fluorescence microscopy. In each chamber a piece (approximately 1 mm2) of each of the three vascular grafts was implanted. Five days after implantation neovascularization was ascertained in 90% of the Omniflow grafts, while only 40% of the PTFE and 20% of the Solco P implants revealed new ingrowing microvessels. On day 10 the density of newly formed microvessels was significantly higher (p less than 0.01) in Omniflow grafts (263.5 +/- 24.1 cm-1) as compared to PTFE (134.2 +/- 20.8 cm-1) and Solco P (153.2 +/- 32.0 cm-1). In addition, the biosynthetic composite revealed a larger extension of neovascularization into the perigraft tissue, and 12 days after implantation these grafts were most tightly incorporated.(ABSTRACT TRUNCATED AT 250 WORDS)

Intact blood supply by microcirculation to a wounded site is an indispensable prerequisite for normal tissue regeneration. However, microvascular changes taking place in the healing process of skin wounds are not understood due to the fact that only few models allow chronic in vivo studies on skin microcirculation. Therefore, we have modified the hairless mouse ear model with the purpose of a quantitative in vivo study of microhemodynamic changes throughout the healing process. Following the creation of a standardized skin wound on the ear of the homozygous hairless mouse (hr/hr), microvessel diameters, red blood cell velocities, wet weight, and leucocyte content of the ear tissue were determined. Surface area of the wound was assessed until complete closure was achieved. By repeated measurements at identical sites over the entire healing period, a distinct pattern of microvascular changes could be observed: microvessel diameters increased to a maximum a few days after wound creation, whereas red blood cell velocities reached their highest values at a later point in time and were still elevated after complete reepithelization of the wounds. Edema and leucocyte content of the ear tissue was most prominent in the early healing phase and gradually decreased to normal values thereafter. These results demonstrate changes of the microvasculature of the hairless mouse ear to injury, which are in accordance to other more indirect studies on this topic. Therefore, we conclude that the model presented is suitable for prolonged quantitative analysis of microcirculation during normal wound healing and may be used to assess microvascular changes taking place during wound healing in pathologically altered tissue.

The effect of buflomedil to protect skin tissue from ischemia and necrosis was studied in random cutaneous flaps. Measurements were performed by intravital microscopy on the microcirculatory level of capillary perfusion in a flap model in the hairless mouse. In 30 hairless mice, single-pedicle flaps measuring 6 x 16 mm were raised perpendicular to the spine of the animal. This flap develops a reliable amount of necrosis at its distal edge over a period of 7 days. A group of 10 mice received intravenous injections of buflomedil in doses of 3 mg/kg per day diluted in 0.1 ml normal saline beginning 4 hours before flap elevation and for 6 consecutive days postoperatively. In addition, 10 further animals received the same treatment except that it was started 5 minutes after flap elevation. In 10 mice serving as controls, normal saline in equal volumes as in the experimental groups was applied. By means of intravital microscopy, functional vessel density (FVD) was determined in 2.5-mm increments from the flap's base to its distal edge at 1, 6, and 24 hours after elevation. Skin-flap survival was quantified by measuring the necrotic area on day 7 by means of digital planimetry. Functional vessel density was preserved in the distal flap of animals pretreated with buflomedil, revealing a higher functional vessel density at 10.0 mm (p less than 0.01), 12.5 mm (p less than 0.05), and 15.0 mm (p less than 0.001) from the flap's base as compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

The objective of this article is to briefly review our present knowledge of the pattern, the functional behaviour and the fine structure of the cutaneous papillary vessels and their alterations under various pathological conditions. The shape of these capillary loops varies within wide ranges dependant on the functional state of the covering epidermis. If the latter is hyperplastic the vessels are elongated, twisted and coiled. In case of epidermal atrophy the capillaries become shorter, decrease in number until their final complete absorption. At the level of the electron microscope the capillary wall clearly shows to consist of 2--3 or more endothelial cells of high electron density encircling an always narrow lumen. Both the inner and outer endothelial surfaces are irregular in outline and the cytoplasm is crowded with filaments of 50--70 A in diameter. In addition it is characterized by the occurrence of a larger number of vacuoles and Weibel-Palade bodies, the latter serving as an excellent marker for endothelial cells to e.g. clearly decide the morphogenesis of certain vascular tumors. Along their apex the capillary loops show a fenestrated endothelium particularly at their adepidermal sites. The basal lamina is multilayered and thereby giving a scroll-like appearance in cross sections. At the ultrastructural level endothelial cells are only provided with a limited repertoire of reactions to noxious stimuli. Among these are: (1) an increase in vesiculation and organelles, (2) the formation of cytoplasmic processes often accompanied by the development of interendothelial "gaps" and (3) alterations - mostly thickenings - of the basement membrane. These different fine structural changes were shown to also occur in various diseases of the skin including it's vascular tumors. In experimental research of the skin microvasculature the most spectacular technique was that of a human skin chamber as originated by Branemark. Thereby most of our older findings as to the functional behavior of the microcirculation in laboratory animals were shown to be valid and hence transferable to humans provided similar experimental approaches were used. Finally the vitalmicroscopy and ultrastructure of tumors (melanoma, hemangiopericytoma and neurilemmoma) transplanted into the hamster cheek pouch are briefly outlined.

The homozygous (hr/hr) hairless mouse ear was introduced in 1980 by Eriksson and coworkers as a model for in vivo studies of the skin microcirculation. Herein we expand on this work, presenting results of in vivo microvascular parameter measurements and morphologic studies in the intact ear. The in vivo measurements include microvascular diameter, RBC velocity, capillary density, and the frequency and amplitude of arteriolar vasomotion. In connection with the in vivo studies, a detailed anatomic description of the overall and vascular anatomy is given. Additionally, the preparation techniques for carrying out these in vivo and morphologic studies in the mouse ear are presented in detail.