oa Subcutaneous Testing of E-spun PCL Patches Suitable for in Situ Heart Valve Tissue Engineering

In situ tissue engineered heart valves yields a new generation of cardiovascular substitutes. The body is used as a bioreactor where it relies on the natural regenerative potential of the body. The shift from the classical way of tissue engineering to in-situ tissue engineering emphasizes the role of the scaffold. The scaffold should be able to capture and preserve cells for tissue formation and it has to maintain valve functionality while tissue is developing. The use of synthetic biomaterials is very attractive. Poly(ε-caprolactone) (PCL) is an important polymer due to its mechanical properties and miscibility with a large range of other polymers. Electrospinning attracted great interest as a production method of biomaterials for in situ tissue engineering. The electrospinning process of PCL offers a nice technique for thin fiber formation to eventually create three dimensional scaffolds with the characteristic three layers, typical for heart valves. The fibers produced with electrospinning provide a similar physical structure as the extra cellular matrix. The space between fibers needs to be large enough for cells to adhere and migrate into the scaffold. Sufficient cellular in growth is needed for tissue formation. In this study cellular in growth was measured in subcutaneously implanted electrospun PCL patches. Furthermore tissue formation and degradation of the polymer is investigated. Thirty healthy male F344 Rats are used. The implants with surrounding tissue were explanted after 2, 5, 10, 21 or 84 days and embedded in paraffin. The explanted tissues were examined using immunohistochemistry (HE,MPO, ED1, α-SMA, and PSR). The electrospun fibers had a diameter of 10 μm. SEM pictures showed controlled void spaces. In the electrospun PCL samples we found a very high cellular infiltration rate after 84 days, mean of 396.819 cells per high power field. First infiltration of mainly neutrophil granulocytes was seen, followed by macrophages. Cells infiltrate throughout the whole sample. After 84 days fibroblast were seen, which were able to produce collagen. Furthermore after 84 days, macrophage giant cells and neo-vessel formation was observed. PCL was degraded in the cytoplasm of the macrophages. Electrospun PCL scaffolds with a fiber diameter of 10 μm, are suitable for cellular in growth and tissue formation. This research forms part of the Project P1.01 iValve of the research program of the BioMedical Materials institute, co-funded by the Dutch Ministry of Economic Affairs, Agriculture and Innovation. The financial contribution of the Nederlandse Hartstichting is gratefully acknowledged.