Vascular disease – including coronary artery disease, carotid artery disease, and peripheral vascular disease – is a leading cause of morbidity and mortality worldwide. The standard of care for restoring patency or bypassing occluded vessels involves using autologous grafts, typically the saphenous veins or internal mammary arteries. Yet, many patients who need life- or limb-saving procedures have poor outcomes, and a third of patients who need vascular intervention have multivessel disease and therefore lack appropriate vasculature to harvest autologous grafts from. Given the steady increase in the prevalence of vascular disease, there is great need for grafts with the biological and mechanical properties of native vessels that can be used as vascular conduits. In this review, we present an overview of methods that have been employed to generate suitable vascular conduits, focusing on the advances in tissue engineering methods and current three-dimensional (3D) bioprinting methods. Tissue-engineered vascular grafts have been fabricated using a variety of approaches such as using preexisting scaffolds and acellular organic compounds. We also give an extensive overview of the novel use of 3D bioprinting as means of generating new vascular conduits. Different strategies have been employed in bioprinting, and the use of cell-based inks to create de novo structures offers a promising solution to bridge the gap of paucity of optimal donor grafts. Lastly, we provide a glimpse of our work to create scaffold-free, bioreactor-free, 3D bioprinted vessels from a combination of rat vascular smooth muscle cells and fibroblasts that remain patent and retain the tensile and mechanical strength of native vessels.
3D Printing has become a mainstay of industry, with several applications in the medical field. One area that could benefit from 3D printing is intestinal failure due to injury or genetic malformations. We bioprinted cylindrical tubes from rat vascular cells that were sized to form biopatches. 2 mm enterotomies were made in the small intestine of male Sprague‐Dawley rats, and sealed with biopatches. These intestinal segments were connected to an ex vivo perfusion device that provided independent extraluminal and intraluminal perfusion. The fluorescence signal of fluorescein isothiocyanate (FITC)‐inulin in the intraluminal perfusate, a non‐absorbable fluorescent marker of intestinal integrity, was measured every 15 min over 90 min, and used to assess the integrity of the segments under both continuous perfusion and alternate‐flow perfusion. Enterotomies were made an inch away from the ileocecal junction in male Wistar rats and sealed with biopatches. The animals were monitored daily and euthanized at post‐operative days 7, 14, 21, and 30. Blinded histopathological analysis was conducted to compare the patch segments to native intestine. Biopatch‐sealed intestinal segments withstood both continuous and pulsatile flow rates without leakage of FITC‐inulin above the control baseline. 21 of 26 animals survived with normal activity, weight gain, and stool output. Histopathology of the explanted segments showed progressive villi and crypt formation over the enterotomies, with complete restoration of the epithelium by 30 days. This study presents a novel application of 3D bioprinting to develop a universal repair patch that can seal lesions in vivo, and fully integrate into the native intestine.
Background The calcium-sensing receptor (CaSR) has been localized and characterized in numerous tissues throughout the body. In the mammalian gastrointestinal tract, the CaSR is known to act as a nutrient sensor and has recently been found to play a role in intestinal fluid and electrolyte balance. This study aims to demonstrate the functionality of the CaSR as a modulator of fluid secretion and absorption along the small intestine. Methods Small intestine regions (proximal, middle, and distal) were isolated from Sprague Dawley rats and loaded into an ex vivo intestinal perfusion device that provides independent intraluminal and extraluminal (serosa/basolateral) perfusion. The regions were perfused with 5 and 7 mM of Ca 2+ , both in the presence and absence of forskolin (FSK), a potent secretagogue. Control experiments were conducted with intraluminal perfusate containing standard Ringer-HEPES buffer with a physiological concentration of Ca 2+ (1 mM). A second set of comparison experiments was performed with intraluminal perfusates containing AC-265347, a CaSR activator and agonist, in the presence of FSK. In all experimental conditions, the intraluminal perfusate contained fluorescein isothiocyanate (FITC)-inulin, a nonabsorbable fluorescent marker of secretion and/or absorption. Intraluminal fluorescence signal was utilized as a measure of water movement at the start of the experiment and every 15 min for 90 min. Results Under physiological conditions, increasing the concentration of Ca 2+ in the luminal perfusate reduced intestinal fluid secretion in all regions. At a Ca 2+ concentration of 7 mM, net fluid absorption was observed in all regions. In the presence of FSK, 5 mM Ca 2+ significantly decreased fluid secretion and 7 mM Ca 2+ abolished FSK-induced fluid secretion. Intraluminal perfusion with 5 mM Ca 2+ was as effective as AC-265347, in reducing secretagogue-induced fluid hypersecretion in the proximal and middle regions. Conclusion This study concludes that apical CaSR is active along the small intestine. Its activation by Ca 2+ and/or calcimimetics reduces fluid secretion in a dose-dependent manner, with higher Ca 2+ concentrations, or application of a calcimimetic, leading to fluid absorption. We furthermore show that, in the presence of FSK, receptor activation abates FSK secretagogue-induced fluid secretion. This presents a new therapeutic target to address secretory diarrheal illnesses.
Background: Sentinel lymph node biopsy is used to evaluate for micrometastasis in auricular melanoma. However, lymphatic drainage patterns of the ear are not well defined and predicting the location of sentinel nodes can be difficult. The goal of this study was to define the lymphatic drainage patterns of the ear and to compare multiple modalities of sentinel node identification. Methods: A retrospective review of a prospectively maintained database evaluated 80 patients with auricular melanoma who underwent sentinel lymph node biopsy by comparing preoperative imaging with intraoperative identification of sentinel nodes. Patients were placed into two cohorts, based on the modality of preoperative imaging: (1) planar lymphoscintigraphy only (n = 63) and (2) single-photon emission computerized tomography combined with computerized tomography (SPECT-CT) only (n = 17). Sites of preoperative mapping and sites of intraoperative identification were recorded as parotid/preauricular, mastoid/postauricular, and/or cervical. Results: In patients that underwent planar lymphoscintigraphy preoperatively (n = 63), significantly more sentinel nodes were identified intraoperatively than were mapped preoperatively in both the parotid/preauricular ( P = 0.0017) and mastoid/postauricular ( P = 0.0047) regions. Thirty-two nodes were identified intraoperatively that were not mapped preoperatively in the planar lymphoscintigraphy group (n = 63), two of which were positive for micrometastatic disease. In contrast, there were no discrepancies between preoperative mapping and intraoperative identification of sentinel nodes in the SPECT-CT group (n = 17). Conclusions: SPECT-CT is more accurate than planar lymphoscintigraphy for the preoperative identification of draining sentinel lymph nodes in auricular melanoma. If SPECT-CT is not available, planar lymphoscintigraphy can also be used safely, but careful intraoperative evaluation, even in basins not mapped by lymphoscintigraphy, must be performed to avoid missed sentinel nodes.
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