Biofabrication of engineered blood vessels for biomedical applications.

To successfully engineer large-sized tissues, establishing vascular structures is essential for providing oxygen, nutrients, growth factors and cells to prevent necrosis at the core of the tissue. The diameter scale of the biofabricated vasculatures should range from 100 to 1,000 µm to support the mm-size tissue while being controllably aligned and spaced within the diffusion limit of oxygen. In this review, insights regarding biofabrication considerations and techniques for engineered blood vessels will be presented. Initially, polymers of natural and synthetic origins can be selected, modified, and combined with each other to support maturation of vascular tissue while also being biocompatible. After they are shaped into scaffold structures by different fabrication techniques, surface properties such as physical topography, stiffness, and surface chemistry play a major role in the endothelialization process after transplantation. Furthermore, biological cues such as growth factors (GFs) and endothelial cells (ECs) can be incorporated into the fabricated structures. As variously reported, fabrication techniques, especially 3D printing by extrusion and 3D printing by photopolymerization, allow the construction of vessels at a high resolution with diameters in the desired range. Strategies to fabricate of stable tubular structures with defined channels will also be discussed. This paper provides an overview of the many advances in blood vessel engineering and combinations of different fabrication techniques up to the present time.

This review covers several aspects and advancements of engineered blood vessel biofabrication, which are essential for establishment of large-sized tissues in different areas of biomedical applications.

The Effect of Iontophoresis with and without Electroporation on the Penetration of High Molecular Compounds into the Stratum Corneum.

Both iontophoresis (IP) and electroporation (EP) can be utilized to increase the penetration of relatively high molecular pharmaceutical and/or cosmeceutical compounds into the stratum corneum (SC), the uppermost layer of the skin. However, few reports exist on which molecular weights are capable of penetrating the SC, although low molecular compounds of less than 500 Da have been found to readily permeate the skin barrier. In our investigation, we applied fluorescein amine-labeled sodium hyaluronate to porcine aural skin after treatment by IP alone or EP + IP. Each layer of the SC was then tape stripped several times. The stripped SC sheets were observed using a confocal laser scanning microscope to determine the relative amounts of sodium hyaluronate present. The results confirmed that the molecular weight of sodium hyaluronate that penetrated the SC was higher with EP + IP than with IP alone. A high correlation was also established between the quantity of sodium hyaluronate that penetrated and its molecular weight following combined EP + IP treatment.

Effects of radiofrequency and ultrasound on the turnover rate of skin aging components (skin extracellular matrix and epidermis) via HSP47-induced stimulation.

Skin aging cannot be escaped, being due to both intrinsic and extrinsic stimuli. They lead to a reduced extracellular collagen matrix in the dermis, along with a higher degradation by metalloproteases (MMPs) activity, as well as a lower differentiation and function of epidermis keratinocytes, characterized by wrinkling and loss of skin elasticity. One of the recent technology to overcome this skin aging process is the use of radiofrequency (RF) and ultrasound (US) technologies which use thermal stimulation to induce neocollagenesis in the skin. But no explanations exist on the involved pathways. Our hypothesis is that RF-US generated heat increases the collagen formation via the heat shock protein 47 (HSP47) induction, a heat sensitive protein related to the collagen expression. To confirm this hypothesis, normal human skin substitutes were subjected to RF-US treatment and results were monitored after 24 and 44 h. RNA sequencing showed a significant induction for the genes related to the epidermis differentiation processes. Almost all keratin genes were thus found upregulated from 2 to 15 times, while collagen type XVII and collagen type IV were increased 12 and 5 times respectively. In parallel, most of MMP genes were observed downregulated. RF-US treatment significantly increased levels of HSP47 proteins, while collagen XVII proteins showed a tendency to be increased and glycosaminoglycans were found 1.4 times significantly enhanced. Finally, histology assessment showed a higher expression of cytokeratins 10 and 14 which can testify a possible reactivation of the skin proliferative state as a rejuvenation strategy.

Leukemic cell-surface CD13/aminopeptidase N and resistance to apoptosis mediated by endothelial cells.

BACKGROUND: Attachment of leukemic cells to vascular endothelial cells induces the vascular endothelial cells to release endothelial cell-derived interleukin 8 (endothelial IL-8), which then induces leukemic cells to undergo apoptosis. NB4, a human promyelocytic leukemic cell line that expresses high levels of cell-surface CD13/aminopeptidase N, does not undergo endothelial IL-8-induced apoptosis. Consequently, we investigated the relationship between cell-surface aminopeptidase activity and endothelial IL-8 induction of apoptosis in various leukemic cell lines. METHODS: CD13/aminopeptidase N activity and IL-8-induced apoptosis were examined in leukemic cell lines. Endothelial IL-8-induced apoptosis was examined further in NB4 cells, K562 cells (human chronic myelogenous leukemic cells expressing low levels of CD13/aminopeptidase N), CD13/aminopeptidase N-transfected K562 (K562/CD13) cells that overexpress aminopeptidase, and mock-transfected K562 cells (vector only). These cells were also cocultured with a vascular endothelial cell layer to investigate the association between aminopeptidase activity and apoptosis in this system. All statistical tests were two-sided. RESULTS: Endothelial IL-8 induced apoptosis in K562 cells but not in K562/CD13 cells. A combination of an aminopeptidase inhibitor (such as bestatin) and endothelial IL-8 induced apoptosis in NB4 cells and K562/CD13 cells (2.88-fold difference [95% confidence interval [CI] = 1.82-fold to 3.94-fold], P =.004 for bestatin-treated NB4 cells and 4.31-fold difference [95% CI = 3.52-fold to 5.10-fold], P<.001 for bestatin-treated K562/CD13 cells). When aminopeptidase activity in NB4 cells was modulated by aminopeptidase inhibitors, a statistically significant correlation was found between aminopeptidase activity and the proportion of apoptotic cells induced by endothelial IL-8 (r = -.837, P<.001 by Pearson's correlation coefficient; r = -.697, P =.013 by Spearman's correlation analysis by ranks). K562/CD13 cells cocultured with vascular endothelial cells did not undergo apoptosis, but the addition of bestatin resulted in the induction of apoptosis in K562/CD13 cells (2.70-fold difference [95% CI = 1.77-fold to 3.63-fold], P<.001). Bestatin treatment increased the level of IL-8 mRNA in and the amount of IL-8 secreted by vascular endothelial cells. CONCLUSIONS: High levels of cell-surface CD13/aminopeptidase N appear to allow leukemic cells to resist endothelial IL-8-induced apoptosis. The combination of endothelial IL-8 and bestatin induce leukemic cells expressing high levels of CD13/aminopeptidase N to undergo apoptosis. Bestatin may be useful for treating patients with leukemia.

New human myelodysplastic cell line, TER-3: G-CSF specific downregulation of Ca2+/calmodulin-dependent protein kinase IV.

We have established a new hematopoietic cell line from a patient with myelodysplastic syndrome (MDS), which was refractory anemia with excess blasts (RAEB). This cell line, designated TER-3, depends on several cytokines for long-term survival and growth, and requires interleukin-3 (IL-3) for continuous growth. Cytochemical analysis revealed that TER-3 cells are weakly dianisidine positive and nonspecific esterase positive, but peroxidase negative. The surface marker profile shows that the TER-3 cells are strongly positive for myeloid, lymphoid, and megakaryocytic antigens such as CD15, CD19, and CD61, and negative for some common multilineage antigens such as CD13, CD33, and CD34. Thus, this cell line has a multilineage phenotype, suggesting that the transformation event occurred in multipotent stem cells. Dianisidine- and nonspecific esterase-positive TER-3 cells increase with granulocyte-colony stimulating factor (G-CSF) rather than with IL-3. These results suggest that the cell line is useful for understanding the mechanism underlying G-CSF-associated hematopoietic cell differentiation and activation in the patient with MDS.