Vascular Establishment Research Articles

3D printed GelMA/carboxymethyl chitosan composite scaffolds for vasculogenesis

The establishment of vascularization is the basic prerequisite for the survival and functionalization of three-dimensional (3 D) tissue-engineered constructs. The application of hydrogel to tissue regeneration has promoted the research and development of regenerative medicine. In this study, we fabricated the composite scaffold composed of gelatin methacryloyl (GelMA) and carboxymethyl chitosan (CMCS) and proved the potential of the scaffold to promote angiogenesis. To characterize the physical properties of the composite scaffold, the mechanical strength, swelling ratio and internal microstructure were tested. The biocompatibility of the GelMA/CMCS scaffold was evaluated by live/dead test and CCK-8. To evaluate the cell distribution, CD31 expression and endothelial differentiation of seeded rat bone marrow mesenchymal stem cells (BMSCs) on the scaffolds, the cytoskeletal staining, immunofluorescence staining and real-time PCR were performed. The composite GelMA/CMCS scaffolds seeded with BMSCs showed excellent mechanical properties, CD31 expression and vasculogenesis genes expression, compared with the pure GelMA scaffold. Furthermore, the activity of BMSCs in 3 D printed GelMA/CMCS scaffolds proved the feasibility of the bioprinting of cells-laden GelMA/CMCS composite scaffolds. In conclusion, our study demonstrated the potential of GelMA/CMCS composite scaffolds for vascular tissue engineering.

Effects and diagnostic value of G protein-coupled receptor 4 on the establishment of neovascularization of human papillomavirus infection in cervical cancer tissues

Objective To explore the effect and diagnostic value of G protein coupled receptor 4 (LGR4) on the establishment of neovascularization of HPV infected cervical cancer tissue. Methods From March 2016 to December 2017, thirty cases of HPV infected cervical cancer, cervical precancerous lesion and cervical health in Lan County Maternal and Child Health and Family Planning Service Center were selected as subjects.After the consent of the subjects, specimens were collected.Immunohistochemical method was used to observe the positive rate of LGR4 in three kinds of tissue specimens.The diagnostic value of LGR4 in differentiation, staging and typing of cervical cancer was observed by screening test, and the expression of related pro-angiogenic factors in LGR4-positive tissues was observed. Results The difference in the expression of LGR4 in healthy tissue, precancerous lesions and cervical cancer tissues was statistically significant(χ2=24.104, P=0.000). The positive rate of LGR4 expression in cervical cancer tissue was 80% (24/30), which was significantly higher than that in healthy group 16.7% (5/30) and precancerous lesion tissue 50% (15/30), the differences were statistically significant (P<0.05). The sensitivity of LGR4 was 80.00%, the specificity was 83.33%, the positive predictive value was 82.76%, the negative predictive value was 80.65%, the diagnostic accuracy was 81.67% and the Kappa value was 0.63, which has good consistency.The differences of LGR4 positive rate in different age, different degree of differentiation and different clinical stages were statistically significant (P<0.05). Laboratory results showed that CRP, PCT, VEGF and TGF-β in LGR4-positive tissues of cervical precancerous lesions and cervical cancer were significantly higher than those in LGR4-negative tissues, the differences were statistically significant (t=9.247, 2.925, 39.669, 15.348, P<0.05). Conclusion LGR4 can promote the establishment of neovascularization in cervical cancer and has certain diagnostic value for cervical cancer and cervical precancerous lesions. Key words: G-protein coupled receptor 4; HPV infection; Cervical cancer; Vascular establishment; Diagnostic value

Oxygen generating scaffolds for enhancing engineered tissue survival

One of the continued challenges in engineering clinically applicable tissues is the establishment of vascularization upon implantation in vivo. Although the effectiveness of an enhanced angiogenic response using various growth factors has been demonstrated in many tissue systems, the rate of angiogenesis could not be accelerated. In this study we investigated whether incorporating oxygen generating biomaterials into tissue engineered constructs would provide a sustained oxygen release over an extended period of time. We examined whether oxygen generating biomaterials are able to maintain cell viability while also maintaining structural integrity of a 3-D construct. Calcium peroxide-based oxygen generating particles were incorporated into 3-D scaffolds of Poly(d,l-lactide– co–glycolide) (PLGA). The scaffolds were designed to generate oxygen over the course of 10 days and simultaneously maintain sufficient mechanical integrity. Scaffolds containing oxygen generating materials maintained elevated levels of oxygen when incubated under hypoxic conditions. Further, these biomaterials were able to extend cell viability growth under hypoxic conditions. These findings indicate that the use of oxygen generating biomaterials may allow for increased cell survivability while neovascularization is being established after implantation. Such scaffolds may play an important role in tissue engineering where currently oxygen diffusion limits the engineering of large tissue implants.

Ontogeny and tissue distribution of leukocyte-common antigen bearing cells during early development of Xenopus laevis

To analyze the ontogenic emergence of leukocytes during early development, a mouse monoclonal antibody (IgG1), designated as XL-1, was produced against the peritoneal macrophages of adult Xenopus laevis. The XL-1 determinant was expressed on all types of leukocytes, including lymphocytes, granulocytes, thrombocytes and macrophages, but not on erythrocytes of either larvae or adults. Immunohistochemical observations of the hemopoietic organs revealed that the XL-1+ cells with granulocyte and/or macrophage morphology appeared at st.36-37 in the liver, at st.44-45 in the mesonephric and the thymus rudiments, and at st.47 in the spleen. The XL-1 determinant was expressed on the precursor cells of T lymphocytes in the thymus rudiments at st.46-47, on the pre-B cells in the liver rudiments at st.47, and on lymphocytes in the spleen at st.48-49. A few XL-1+ cells were present in the ventral blood island of the st.35/36 embryos, where differentiating erythrocytes had predominated since st.28. XL-1+ cells with a macrophage-like morphology were found in several locations of the mesenchyme in the st.32 embryos, before the establishment of vascularization at st.33/34 and far earlier than the emergence of lymphocytes.

Vascularization of fetal cell suspension grafts in the excitotoxically lesioned adult rat thalamus

Several studies have considered the establishment of vascularization in intracerebral solid transplants of neural tissue. The widely supported interpretation of the results is that the vascular network of the solid grafts is already present before implantation into the host brain. The situation is different when dissociated fetal tissue is transplanted as a cell suspension because in these conditions the fetal vascular network is disrupted. The present study has, therefore, been undertaken to follow the angiogenesis in a transplant of dissociated fetal cells implanted into the excitotoxically neuron-depleted thalamus. The vascular network is compared to that observed in the intact and in the lesioned thalamus both in terms of morphology of the capillaries and of the function of the blood-brain barrier (BBB). In the transplant, capillaries, stained by Indian ink, are very few in number and have very fine calibers during the first 20 days after grafting. Some structures can be identified as immature blood vessels at the electron microscopic level. The blood vessels are progressively more numerous in the graft and they demonstrate mature ultrastructural features 2 months after grafting. Last, there is no leakage of the BBB for peroxidase. The vascularization seems to follow a pattern of maturation comparable to that described during development in the literature. In contrast, in the lesioned area, there is a reactive angiogenesis: 10 days after the excitotoxic injection (shortest time studied), there are many wide caliber vessels with expanded perivascular spaces engorged with mesodermal cells. A microvascularization also develops transiently during the first two months. Capillaries are abnormal from the functional point of view, since there is a leakage of the BBB to macromolecules. The use of an experimental model in which transplant had to grow in a lesioned area permits to determine two types of vascularization: an apparently normal developmental timetable, normal morphological and functional characteristics, in the transplant; a reactive angiogenesis, in the lesioned area.

On the origin of haemopoietic stem cells in the avian embryo: an experimental approach

It is currently accepted that stem cells of the definitive blood cell lines originate from the yolk-sac blood islands. Experiments were devised to examine the validity of this theory in the avian embryo. These involved grafting two-day-old quail embryos on to chick yolk-sacs of comparable developmental stages, i.e. before or shortly after the establishment of vascularization. The conclusions of the experiments are based on the possibility of distinguishing chick cell nuclei from those of the quail. In the developing haemopoietic organs (spleen and thymus) of quail embryos grafted on to the chick and subsequently incubated for 6-11 days, all cells, whether belonging to the granulopoietic, erythropoietic or lymphopoietic series, are of quail type. Thus these organs have not been colonized by chick stem cells. On the other hand, coelomic graft experiments show that the development of these organs is indeed dependent on an extrinsic colonization by haemopoietic cells; quail spleen or thymus rudiment, developing in the coelom of a chick is populated by chick cells. Thus no incompatibility which would prevent heterospecific colonization exists in this system. It is concluded that haemopoietic stem cells of the definitive blood cell series originate from some source other than the yolk-sac, and that this source must be intra-embryonic.