Potentials and limitations of Integra® flowable wound matrix seeded with adipose tissue-derived microvascular fragments.

Adipose tissue-derived microvascular fragments (ad-MVF) represent promising vascularisation units for bioengineered Integra® matrix wound dressing (MWD). However, due to the sheet-like structure with small pore sizes, the seeding of this matrix with ad-MVF is mainly limited to its surface. Integra® flowable wound matrix (FWM) may be suitable to achieve a more homogeneous distribution and, thus, improved vascularisation, because this gel-like matrix allows for the direct admixture of ad-MVF during sample preparation. To test this hypothesis, we seeded MWD and FWM with an identical number of ad-MVF and assessed their distribution and inter-fragment distance within both matrices. Moreover, ad-MVF-seeded MWD and FWM were implanted into full-thickness skin defects within mouse dorsal skinfold chambers to analyse their vascularisation, epithelialisation and tissue incorporation using intravital fluorescence microscopy, histology and immunohistochemistry. Seeded FWM exhibited a more homogeneous ad-MVF distribution, when compared to MWD. This resulted in a significantly increased inter-fragment distance, preventing the reassembly of ad-MVF into new microvascular networks. Accordingly, the vascularisation of FWM was diminished after implantation, as indicated by a reduced functional microvessel density and blood perfusion. This was associated with a decreased tissue incorporation and epithelialisation of the matrix, when compared to ad-MVF-seeded MWD. Hence, the use of FWM as a carrier system may require a tremendous amount of ad-MVF to shorten their inter-fragment distance and, thus, to maintain their vascularisation capacity for tissue engineering applications.