Development of the Human Umbilical Vein Scaffold for Cardiovascular Tissue Engineering Applications

Abstract

Biologic function and the mechanical performance of vascular grafting materials are important predictors of graft patency. As such, "functional" materials that improve biologic integration and function have become increasingly sought after. An important alternative to synthetic materials is the use of biomaterials derived from ex vivo tissues that retain significant biologic and mechanical function. Unfortunately, inconsistent mechanical properties that result from tedious, time consuming, manual dissection methods have reduced the potential usefulness of many of these materials. We describe the preparation of the human umbilical vein (HUV) for use as an acellular, three-dimensional, vascular scaffold using a novel, automated dissection methodology. The goal of this investigation was to determine the effectiveness of the autodissection methodology to yield an ex vivo biomaterial with improved uniformity and reduced variance. Mechanical properties, including burst pressure, compliance, uniaxial tension testing, and suture holding capacity, were assessed to determine the suitability of the HUV scaffold for vascular tissue engineering applications. The automated methodology results in a tubular scaffold with significantly reduced sample to sample variation, requiring significantly less time to excise the vein from the umbilical cord than manual dissection methods. Short-term analysis of the interactions between primary human vascular smooth muscle cells and fibroblasts HUV scaffold have shown an excellent potential for cellular integration by native cellular remodeling processes. Our work has shown that the HUV scaffold is mechanically sound, uniform, and maintains its biphasic stress-strain relationship throughout tissue processing. By maintaining the mechanical properties of the native blood vessels, in concert with promising cellular interactions, the HUV scaffold may lead to improved grafts for vascular reconstructive surgeries.

Preparation of Ex Vivo–Based Biomaterials Using Convective Flow Decellularization

“…18 Briefly, human umbilical cords were collected from a local hospital up to 48 h after delivery. Cords were then carefully rinsed with distilled water to remove residual blood and cut into 120-mm-long segments.…”

In Vitro Method for Real-Time, Direct Observation of Cell–Vascular Graft Interactions under Simulated Blood Flow

“…13 In brief, umbilical cords were rinsed clean and cut into 10 cm sections. A stainless steel mandrel (1/4¢¢ outside diameter (OD)) was inserted through the vein and then progressively frozen down to -80°C.…”

“…21 The HUV has been used in vascular reconstruction surgeries for more than 30 years, 22 and, more recently, it has been developed as an ex vivo-derived vascular scaffold for tissue engineering applications. 13,23 Due to its clinical relevance, the HUV served as an excellent model to assess a vascular biomaterial for both modeling platelet/neutrophil adhesion and endothelialization under flow.…”

Directed Oxygen Gradients Initiate a Robust Early Remodeling Response in Engineered Vascular Grafts

“…HUV sections were dissected using an automated method as previously described. 21 Briefly, 100-mm segments of human umbilical cords ( < 24 h from delivery) were collected and mounted onto stainless steel mandrels and frozen to -80°C overnight. Frozen vessels were then loaded into a 10'' CNC bench lathe (MicroKinetics, Kennesaw, GA), and cut to a wall thickness of 750 mm at a rotational speed of 2800 RPM with an axial cutting rate of 5 mm/s.…”

“…To accomplish this, human smooth muscle cells (SMCs) were seeded onto the ablumenal surface of a model vascular scaffold derived from the human umbilical vein (HUV), 21 and 3 independent gas environments were assessed: (1) ablumen and lumen circuits maintained at 11% oxygen, (2) ablumen and lumen circuits maintained at 21% oxygen, and (3) an applied gradient generated by maintaining the ablumen at 11% oxygen and lumen at 21% (11%:21% oxygen gradient). After 3 weeks of culture, analysis included histology, cellular proliferation and metabolism, and mechanical analysis.…”