Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - 3DSTAR (Highly porous collagen scaffolds for building 3D vascular networks: structure and property relationships)

Teaser

In many diseases and traumas, organ function is severely compromised, and the only solution is organ transplantation. There are two major problems associated with this strategy: a shortage of organs for transplantation and an immunological mismatch between the donor and the...

Summary

In many diseases and traumas, organ function is severely compromised, and the only solution is organ transplantation. There are two major problems associated with this strategy: a shortage of organs for transplantation and an immunological mismatch between the donor and the recipient, leading to organ rejection. If we could restore organ function by growing it in the lab from patient’s own cells, we’d be able to avoid both afore-mentioned problems. To do so, cells must be grown under tissue-specific conditions in order to reproduce the right numbers and activity. In my project, I have addressed the question of finding the right spatial conditions to grow bone and microvasculature. I have produced scaffolds suitable for growing cells in a 3-dimentional (3D) microenvironment. These scaffolds are made of a biocompatible, bioactive material and have high porosity. This allows cells to get deep within the scaffolds, attach and start producing the tissue of interest. The overall objectives were to characterise the complex 3D pore structure of these scaffolds (size, shape and interconnectivity), to establish how pore architecture affects cell performance and identify the right cell culture conditions (cell density, co-culture with other cells, etc) to encourage cells to form vascular-like structures and bone. I have investigated two types of pore configurations: randomly aligned (isotropic) or unidirectionally aligned (anisotropic) and have assessed how this pore alignment affects the way cells attach and grow, and how they start producing the engineered tissue. To conclude, I have identified the optimal conditions to grow both bone and micro-vessel tissues by investigating two main parameters: what cell types to include and which pore geometry is best. I have shown that anisotropic scaffolds are preferable for the formation of bone and micro-vessels, and that growing blood vessel cells together with growth supporting cells promote better scaffold vascularisation.
Addressing these questions gives a better understanding of the optimum conditions to grow these two tissues, and thus will help to grow the whole bone and other vascularised organs in the future. This will eliminate the need for donor organs and will prevent organ rejection, thereby saving lives and improving the quality of life of many people.

Work performed

Work performed:
1. I have produced scaffolds with two types of pore orientations: isotropic and anisotropic.
2. I have studied the scaffold pore architecture using scanning electron microscopy (SEM).
3. I have produced 3D images of the scaffolds using high resolution X-ray computed tomography (micro-CT) . In collaboration with other researchers at Cambridge University, a code has been developed to characterise the complex 3D pore structure of the scaffolds (pore diameter, porosity, pore orientation, specific surface area).
4. I have measured the scaffold specific permeability (resistance to fluid flow) using a constant pressure gradient method.
5. I have assessed cell performance in two tissue engineering models: scaffold pre-vascularisation (microvessel-like formation within the scaffolds) and bone formation, investigating the following parameters:
• The migration and distribution of human umbilical cord endothelial cells (HUVECs) within the scaffolds.
• Self-assembly of HUVECs, in a mono-and a co-culture with human osteoblasts (HObs), into microvessel-like structures as a function of scaffold pore architecture.
• HOb viability, metabolic activity, proliferation and osteogenic differentiation as a function of scaffold pore architecture.
Results overview:
I have characterised the scaffold pore architecture using a customised code developed in collaboration with other colleagues at Cambridge University. I have shown that cells were able to go at higher depths and were more uniformly distributed within aligned (anisotropic) scaffolds as compared to isotropic scaffolds. Aligned scaffolds were a better platform for blood vessel cells to self-organise into vascular-like structures, especially when grown in co-culture with supporting cells. These structures, comprised of multiple blood vessel cells attached to one another, were aligned around the pores, and had features resembling native small blood vessels. Additionally, I have found that in the bone model cell activity was higher in the anisotropic scaffolds. Moreover, the premature bone cells seeded on the anisotropic scaffolds showed earlier and stronger differentiation (became more bone-like) as compared to the isotropic ones and produced mineral matrix similarly to the cells in the native bone. Overall, I was able to show that scaffolds pore structure affects the formation of bone and vessel-like structures, and thus needs to be taken into consideration when designing engineered tissues.
Results exploitation and dissemination:
A manuscript on ‘’Collagen scaffolds with tailored pore geometry for building 3-dimnsional vascular networks’’ has recently been accepted in the Materials Letters journal.
A second manuscript on scaffold characterisation (pore architecture, Young’s modulus and specific permeability) and bone formation is under preparation.

The results have been presented in 7 international conferences (e.g., Biologic Scaffolds for Regenerative Medicine International Symposium, Tissue Engineering and Regenerative Medicine International Society World Congress, International Conference on Tissue Engineering and Regenerative Medicine where I was a keynote speaker, and others), arousing great interest in the scientific community.

Final results

We have expanded the research beyond the planned state of the art. We have developed a code to characterise the complex pore structure of collagen scaffolds, a work that can potentially help many other researchers working with porous materials in a variety of applications. We have also developed an additional model for engineered bone.
We have shown the advantage of aligned scaffolds for cell growth and formation of both bone tissue and vascular-like structures. The results from this project have the potential to open new research directions that will ultimately lead to a better tissue and organ repair. Moreover, both engineered tissues would enable scientific and technological advances in the academic and the pharmaceutical communities, serving as platforms for drug testing and human disease models.

Website & more info

More info: https://www-memti.eng.cam.ac.uk/people/Sasha.