Speaker
Description
For almost a century, in vitro 3D tissue models of skin are known. However, these 3D skin models are mainly used for basic cosmetic testing rather than for clinical application. This is because of a lack of reproducible methodology, physiological structures and tissue architecture. An essential step in the development of a physiologically relevant in-vitro skin model is the incorporation of functional blood vessels (BVs) and high longevity. The advent of current tissue engineering strategies has now facilitated the fabrication of vascularized human skin equivalents (vHSEs). However, the challenge of maintaining the stability and durability of the developed vHSEs for a long duration persists. Unfortunately, the cause and the solution for the instability of both vascularized and non-vascularized HSEs are seldom reported in the literature. An important aspect that is overlooked during the construction of vHSE is the role of keratinocytes (KCs), the cells forming the epidermis. It is known that KCs modulate the balance between the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) as well as secrete angiogenic growth factors such as vascular endothelial growth factor (VEGF). BVs in turn respond to such factors and undergo rapid branching or regression depending on the signal. Therefore, the cross-talk between KCs and the vascularized dermis in-vitro results in a vicious cycle of vascular regression and matrix degradation. In the context of the skin model, this has never been investigated. Can a flow culture ameliorate this?
Previous reports have mostly elucidated the role of dynamic cultures on the improvement of the barrier properties of skin model or in a few cases vasculature but they fail to show in entirety why a dynamic flow environment can sustain a long-term vessel architecture, dermal integrity and thereby maintaining vHSEs homeostasis.
In this work, we report the fabrication of scaffold-free vHSEs cultivated within a 3-D printed flow bioreactor to mitigate the uncontrolled formation of BVs in the vHSEs. This was achieved by the modulation of VEGF and hypoxia inducible factor 1A (HIF1A) gene expression and by maintaining the balance of MMPs/TIMPs gene expression, thereby, improving the vHSEs stability. Apart from the enhancement of barrier properties, optimal epidermal differentiation and improved dermal stability, flow culture also resulted in the formation of perfusable vascular openings, which could be attributed to the oscillatory flow patterns and growth factor gradient. As an example of the application of flow culture, we conducted a 3D wound healing assay to show the effect of flow in comparison to the static culture. Together, this work deliberates the response of lab-grown vHSEs to a perfusable flow environment and emphasizes the requisite of dynamic tissue-engineered strategies for improved vascularized skin constructs.
20941861677
