improving-2d-and-3d-skin-in-vitro-models-using-macromolecular-crowding

Improving 2D and 3D Skin <em>In Vitro</em> Models Using Macromolecular Crowding

The glycoprotein family of collagens represents the main structural proteins in the human body, and are key components of biomaterials used in modern ...

National University of Singapore

Institute of Medical Biology, A*STAR

The excluded volume effect (EVE) rules all life processes. It is created by macromolecules that occupy a given volume thereby confining other molecules to the remaining space with large consequences on reaction kinetics and molecular assembly. Implementing EVE in fibroblast culture accelerated conversion of procollagen to collagen by procollagen C-proteinase (PCP/BMP-1) and proteolytic modification of its allosteric regulator, PCOLCE1. This led to a 20-30- and 3-6-fold increased collagen deposition in two- and three-dimensional cultures, respectively, and creation of crosslinked collagen footprints beneath cells. Important parameters correlating with accelerated deposition were hydrodynamic radius of macromolecules and their negative charge density.

Collagen matrix deposition is dramatically enhanced in vitro when crowded with charged macromolecules: the biological relevance of the excluded volume effect.

Skin is one of the most accessible tissues for experimental biomedical sciences, and cultured skin cells represent one of the longest-running clinical applications of stem cell therapy. However, culture-generated skin mimetic multicellular structures are still limited in their application by the time taken to develop these constructs in vitro and by their incomplete differentiation. The development of a functional dermal-epidermal junction (DEJ) is one of the most sought after aspects of cultured skin, and one of the hardest to recreate in vitro. At the DEJ, dermal fibroblasts and epidermal keratinocytes interact to form an interlinked basement membrane of extracellular matrix (ECM), which forms as a concerted action of both keratinocytes and fibroblasts. Successful formation of this basement membrane is essential for take and stability of cultured skin autografts. We studied interactive matrix production by monocultures and cocultures of primary human keratinocytes and fibroblasts in an attempt to improve the efficiency of basement membrane production in culture using mixed macromolecular crowding (mMMC); resulting ECM were enriched with the deposition of collagens I, IV, fibronectin, and laminin 332 (laminin 5) and also in collagen VII, the anchoring fibril component. Our in vitro data point to fibroblasts, rather than keratinocytes, as the major cellular contributors of the DEJ. Not only did we find more collagen VII production and deposition by fibroblasts in comparison to keratinocytes, but also observed that decellularized fibroblast ECM stimulated the production and deposition of collagen VII by keratinocytes, over and above that of keratinocyte monocultures. In confrontation cultures, keratinocytes and fibroblasts showed spontaneous segregation and demarcation of cell boundaries by DEJ protein deposition. Finally, mMMC was used in a classical organotypic coculture protocol with keratinocytes seeded over fibroblast-containing collagen gels. Applied during the submerged phase, mMMC was sufficient to accelerate the emergence of collagen VII along the de novo DEJ, together with stronger transglutaminase activity in the neoepidermis. Our findings corroborate the role of fibroblasts as important players in producing collagen VII and inducing collagen VII deposition in the DEJ, and that macromolecular crowding leads to organotypic epidermal differentiation in tissue culture in a significantly condensed time frame.

Making more matrix: enhancing the deposition of dermal-epidermal junction components in vitro and accelerating organotypic skin culture development, using macromolecular crowding.

Article	Year
Collagen matrix deposition is dramatically enhanced in vitro when crowded with charged macromolecules: the biological relevance of the excluded volume effect. FEBS letters\| PubMed ID: 17531987	2007
Making more matrix: enhancing the deposition of dermal-epidermal junction components in vitro and accelerating organotypic skin culture development, using macromolecular crowding. Tissue engineering. Part A\| PubMed ID: 25058150	2015

Paula Benny

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