Extrinsic Vessels Research Articles

Acceleration of vascularized bone tissue-engineered constructs in a large animal model combining intrinsic and extrinsic vascularization.

During the last decades, a range of excellent and promising strategies in Bone Tissue Engineering have been developed. However, the remaining major problem is the lack of vascularization. In this study, extrinsic and intrinsic vascularization strategies were combined for acceleration of vascularization. For optimal biomechanical stability of the defect site and simplifying future transition into clinical application, a primary stable and approved nanostructured bone substitute in clinically relevant size was used. An arteriovenous (AV) loop was microsurgically created in sheep and implanted, together with the bone substitute, in either perforated titanium chambers (intrinsic/extrinsic) for different time intervals of up to 18 weeks or isolated Teflon(®) chambers (intrinsic) for 18 weeks. Over time, magnetic resonance imaging and micro-computed tomography (CT) analyses illustrate the dense vascularization arising from the AV loop. The bone substitute was completely interspersed with newly formed tissue after 12 weeks of intrinsic/extrinsic vascularization and after 18 weeks of intrinsic/extrinsic and intrinsic vascularization. Successful matrix change from an inorganic to an organic scaffold could be demonstrated in vascularized areas with scanning electron microscopy and energy dispersive X-ray spectroscopy. Using the intrinsic vascularization method only, the degradation of the scaffold and osteoclastic activity was significantly lower after 18 weeks, compared with 12 and 18 weeks in the combined intrinsic-extrinsic model. Immunohistochemical staining revealed an increase in bone tissue formation over time, without a difference between intrinsic/extrinsic and intrinsic vascularization after 18 weeks. This study presents the combination of extrinsic and intrinsic vascularization strategies for the generation of an axially vascularized bone substitute in clinically relevant size using a large animal model. The additional extrinsic vascularization promotes tissue ingrowth and remodeling processes of the bone substitute. Extrinsic vessels contribute to faster vascularization and finally anastomose with intrinsic vasculature, allowing microvascular transplantation of the bone substitute after a shorter prevascularization time than using the intrinsic method only. It can be reasonably assumed that the usage of perforated chambers can significantly reduce the time until transplantation of bone constructs. Finally, this study paves the way for further preclinical testing for proof of the concept as a basis for early clinical applicability.

Clinical and Vascular Anatomical Study of Distally Based Sural Flap

The distally based sural flap has been useful for reconstruction of the distal third portion of the lower leg. We retrospectively review in this report the clinical outcomes. Moreover, we studied the vascular anatomy surrounding the sural nerve using preserved cadavers. Twenty-eight consecutive cases of distally based sural flap transfer were reviewed retrospectively. All flaps were harvested with the deep fascia and lesser saphenous vein, but the sural nerve was excluded in all cases to prevent paresthesia. The sural nerve can be easily detached from the flap by meticulous dissection from the deep fascia without causing significant bleeding. In the vascular anatomic study, barium was injected through the femoral artery after elevating the flap in 20 legs of preserved cadavers. Subsequently, tissue specimens were harvested from the upper, middle, and lower sites of the flap for histologic analyses. Clinically, 22 of 28 flaps survived completely. Distal partial necrosis was observed in 5 flaps, and total necrosis was observed in 1 flap. Causes of total or partial necrosis have been suggested to be dependent on flap shape, pedicle length, and complicating diseases. Anatomic angiography revealed that small extrinsic vessels around the sural nerve and the lesser saphenous vein are important, especially in distally-based sural flap transfer; those around the sural nerve seem to have the most important impact on flap survival. The sural nerve has fewer intrinsic vessels than the extrinsic vessels of the sural nerve and lesser saphenous vein. The distally based sural flap was useful for reconstruction of the distal third portion of the lower leg. Moreover, these clinical and anatomic findings suggest that the sural nerve can be preserved to prevent surgically induced paresthesia.

Preserved extrinsic neural connection between gallbladder and residual stomach is essential to prevent dysmotility of gallbladder after distal gastrectomy.

Many reports have been made on gallbladder dysfunction after gastric surgery. We reported that the gallbladder contractions were abolished after antrectomy. Our hypothesis is that preservation of the neural connection along gastric vessels maintains normal gallbladder function during fasting after antrectomy. Six dogs underwent antrectomy with preservation of the extrinsic nerves and six other dogs underwent conventional antrectomy with dissection of the extrinsic nerves and vessels. Laparotomy alone was performed on another six control dogs. Motor activities of the gallbladder and upper gastrointestinal tract were recorded by strain gauges in conscious dogs. Motilin and CCK-OP were used for pharmacological interventions. In conventional antrectomy, the amplitudes of the cyclic motor activity of the gallbladder and the stomach during fasting were significantly reduced, while this activity was maintained in dogs when extrinsic nerves were preserved. The coordination of the motor activity among the gallbladder, stomach and the duodenum was not impaired in the dogs when extrinsic nerves were preserved. The contractions of the gallbladder induced by exogenous motilin were reduced significantly in conventional antrectomy. Therefore, the preserved neural connection along the gastric vessels maintains normal gallbladder function in the fasting state even after distal gastrectomy.

Functional outcome of anterior transposition of the vascularized ulnar nerve for cubital tunnel syndrome

Anterior transposition of the ulnar nerve is a widely used treatment for cubital tunnel syndrome, but neurolysis performed at the time of surgery may impair the blood supply to the ulnar nerve. This study compared the results of intramuscular anterior transposition of the ulnar nerve with or without preserving the extrinsic vessels of the ulnar nerve in 35 patients. The postoperative nerve conduction velocity and the clinical results were better in the group in which the extrinsic vessels were presented.

Blood flow in mobilized nerves: results in a rabbit sciatic nerve model.

The purpose of this study was to evaluate the immediate effect on capillary blood flow of surgical mobilization of 15 cm of the rabbit sciatic and tibial nerve. Capillary nerve blood flow was determined with 16-micron radioactive microspheres. Thirty-seven rabbits were divided into six groups. In the control group A (n = 7), the in situ nerve blood flow was determined. In group B (n = 7), the nerve was mobilized, leaving only the proximal and distal endoneurial vascular supplies; blood flow increased compared with in situ values in most segments. In group C (n = 5), the nerve was mobilized as in group B, but also transected distally; blood flow was markedly decreased in the distal segments but was maintained up to a diameter-to-length ratio of 1:63. In group D (n = 6), the nerve was not mobilized, but was transected proximally and distally; blood flow increased in all segments. In group E (n = 5), the nerve was mobilized and transected proximally and distally, leaving only nerve branches intact; blood flow was significantly higher in segments of the nerve from which nerve branches originated with the nerve receiving blood flow through its branches. In group F (n = 6), the nerve was mobilized, all extrinsic vessels except one were transected, and the proximal and distal nerve was transected; flow was maintained to a diameter:length ratio of 1:41 from the source of blood flow. Therefore, it does appear that long lengths of nerve may be mobilized and transposed while maintaining sufficient blood flow.

Direction of blood flow and changes in resistance of major arteries supplying the ovary of the pregnant rat.

In this study, we examined changes in vascular resistance contributing to increased ovarian blood flow in the pregnant rat. Ovarian blood flow was monitored in vivo using a venous outflow cannulation technique in nonpregnant rats and in pregnant rats at Day 16 and Day 22, and increased from 0.18 +/- 0.02 to 0.81 +/- 0.09 and 1.02 +/- 0.08 ml min(-1) ovary(-1) (mean +/- SEM; n = 7, 7, 6), respectively. Intrinsic vessels within the ovarian complex accounted for 81%, 73%, and 70% of total resistance to ovarian blood flow. Of the two major extrinsic supply vessels, from one-half to two-thirds of the ovarian blood was derived from the uterine artery, and the ovarian artery never contributed to uterine blood flow. These results indicate that the major supply vessels are unlikely to limit ovarian blood flow, even near term when competing demand by the gravid uterus reaches a peak. The finding that ovarian blood flow is derived predominantly from the uterine artery may relate to local mechanisms that influence ovarian function and fetal growth.

The vasculature of the peripheral portion of the human eighth cranial nerve

The vasculature of the peripheral portion of the human eighth cranial nerve (VIIIN) was investigated by light and transmission electron microscopy. Arterioles and venules running longitudinally around the VIIIN formed the extrinsic vascular system. The anatomical relationship between these extrinsic vessels and the VIIIN sheath was similar to that between blood vessels on the surface of the brain and the pia mater. In the endoneurium, postcapillary venules and large capillaries were sparsely distributed and longitudinally arranged, and these microvessels formed the intrinsic microvascular system, which was supported by the extrinsic vascular system via anastomosing vessels. The ultrastructural features of the internal auditory artery and its main branches were the same as those of other intracranial arteries. Ultrastructural study also revealed myo-endothelial junctions in anastomosing arterioles, and endotheli-pericytic junctions in extrinsic and anastomosing venules. Microvascular endothelial cells were connected by tight junctions in both the vestibular ganglion and the rest of the VIIIN. These features of the vasculature were considered to be effective for maintenance of the endoneurial fluid and regulation of the circulation in the peripheral portion of the human VIIIN.

Evidence that embryonic kidney cells expressing flk-1 are intrinsic, vasculogenic angioblasts.

Renal glomerular capillary tufts have been believed to arise from angiogenic ingrowth of extrinsic vessels. We found, however, that when embryonic day 12 (E12) mouse kidneys were maintained in culture for 6 days and then grafted into anterior eye chambers of adult transgenic ROSA26 host mice (which carry the beta-galactosidase transgene), glomerular endothelial cells within the grafts were predominantly of intrinsic, kidney origin. To identify potential endothelial precursors, we immunolabled kidneys with antibodies against the vascular endothelial growth factor receptor, flk-1. Numerous discrete cells expressing flk-1 were scattered throughout the nephrogenic mesenchyme of both E12 and newborn kidneys, and with development these cells became concentrated in microvessels, glomerular vascular clefts, and glomerular tufts. In adults, flk-1 was weakly expressed in glomeruli but absent elsewhere. To examine abilities of flk-1-positive cells to establish glomeruli, E12 kidneys were grafted into kidney cortices of adult and newborn ROSA26 hosts. Grafts into adults resulted in few glomeruli containing host-derived endothelium, whereas a majority of glomeruli grafted into newborns contained host cells. Cells of graft origin were found in vessels forming in renal cortices of newborn hosts, but not in adults. Our findings indicate that embryonic kidney cells expressing flk-1 are angioblasts that create microvessels and glomeruli by vasculogenesis.

Noradrenergic and peptidergic innervation of the extrinsic vessels and microcirculation of the rat cremaster muscle

The noradrenergic and peptidergic innervation of the extrinsic vessels and microcirculation of the rat cremaster muscle was examined. Catecholamine-containing nerves were identified histochemically by glyoxylic acid-induced fluorescence and tyrosine hydroxylase immunoreactivity (TH-IR). The extrinsic pudic-epigastric artery and vein as well as the entire intramuscular arteriolar network was innervated by noradrenergic axons. The capillaries and intramuscular venules of the cremaster muscle were devoid of a noradrenergic innervation. Immunohistochemical double-labeling demonstrated that most, if not all, of the TH-IR axons also possessed neuropeptide Y immunoreactivity (NPY-IR), implying colocalization of the norepinephrine and NPY in the perivascular nerves. No vasoactive intestinal peptide immunoreactivity (VIP-IR) was found, except for occasional VIP-IR axons associated with the pudic-epigastric artery. Substance P immunoreactive (SP-IR) axons formed a sparse plexus around the arteries and larger arterioles. Calcitonin generelated peptide immunoreactivity (CGRP-IR) had a similar distribution to the SP-IR axons. CGRP-IR was also observed in axons alongside some smaller arterioles and capillaries. The extrinsic vessels and intramuscular arteriolar network of the rat cremaster muscle are innervated by noradrenergic axons which contain NPY and by presumed sensory nerves containing SP and/or CGRP. Both types of nerves may contribute to regulation of microvascular function.

肘部管症候群における我々の手術法とその成績

Twenty-four cases of cubital tunnel syndrome were operated on with our new technique from May, 1983 to April, 1987. A new neuro-groove was made at the anterior side of the medial epicondyle by cutting off the origin of pronator teres and flexor muscles. Then free fatty tissue was seated on the bottom of the new groove. The ulnar nerve was transposed to the new groove with its extrinsic vessels (A. collateralis ulnaris superior and A. recurrens ulnaris posterior). Results showed that 19 cases (79.2%) were estimated to be excellent or good. It is as good as results of a modified King's procedure. We had no “poor” case and no re-operated case.Considering some merits for occupations and activities of daily living by preserving the medial epicondyle, not only a modified King's procedure but also our procedure of vascularized anterior transposition can be selected.

Vasculogenesis of the bursa cloacalis (bursa of Fabricius) of the chick embryo.

Vasculogenesis of the bursa cloacalis (bursa of Fabricius) was examined i 10- to 21-day chick embryos and in chicks during the first 5 days post-hatching. The entire circulatory system was injected with India ink, and the bursae were then removed and either cleared for examination in toto or sectioned serially. The bursa was supplied by three pairs of extrinsic blood vessels. At 10 and 11 days of incubation, most intrinsic vessels were arranged in a superficial, hexagonal network. In regions of developing plicae, the hexagonal plexus extended into the core of each plica, forming middle plical vessels. The latter were interconnected across interplical areas by cross-connecting vessels. The middle plical vessels gave rise to small capillary offshoots, which soon increased in complexity, forming delicate loops. Branches extended from these loops through the subepithelial lamina propria to incipient epithelial buds by 12 days of incubation. All epithelial buds were supplied by at least one such branch, and similar branches extended to the basal aspect of the epithelium in areas where epithelial buds had not yet formed. This observation is consistent with the hypothesis that blood vessels induce formation of epithelial buds. At about 15 days of incubation, the cortex and medulla of each developing lymphatic follicle were defined clearly, and an intricate, web-like, capillary network coursed throughout the follicular cortex. The medulla appeared to be devoid of capillaries. The diameters of all intrinsic and extrinsic bursal blood vessels gradually increased throughout development. During post-hatching stages, the diameters of the extrinsic vessels continued to increase, whereas those of the intrinsic vessels were markedly decreased from late pre-hatching stages.