# A preliminary preclinical assessment of macromolecular crowding in tissue engineering

## TL;DR

This study explores how macromolecular crowding can speed up the development of tissue-engineered medicines using bone marrow cells.

## Contribution

The novel use of macromolecular crowding to enhance extracellular matrix deposition in bone marrow stromal cells for tissue engineering.

## Key findings

- Macromolecular crowding increased collagen type I and IV deposition without affecting cell viability or proliferation.
- MMC altered CD105 and HLA-DR expression in bone marrow mesenchymal stromal cells.
- In vivo preclinical results showed similar wound healing outcomes with and without macromolecular crowding.

## Abstract

Although bone marrow mesenchymal stromal cells (BMSCs) are extensively used in biomedicine, they have yet to be used in the commercial development of a tissue engineered medicine. It has been argued that the major roadblock in their commercial deployment is the lengthy in vitro culture periods required for the development of implantable tissue surrogates. Macromolecular crowding (MMC) has been shown to enhance and increase extracellular matrix deposition in eukaryotic cell culture, allowing for the accelerated development of tissue facsimiles.

With these in mind, human BMSCs were cultured under MMC conditions and the developed tissue-engineered medicine was assessed in vitro and in vivo in a humanised athymic nude mouse excisional wound splinting model.

Starting with basic cell function analysis, MMC did not significantly affect cell metabolic activity, viability and proliferation. Electrophoresis and immunofluorescence analyses revealed that MMC significantly increased collagen type I and collagen type IV deposition, without significantly affecting collagen type III deposition. Flow cytometry analysis demonstrated similar CD44, CD73, CD90, CD146, HLA-ABC, CD31, CD45, CD80 and CD86 expression between the without and the with MMC groups. Interestingly though the MMC group had higher CD105 and lower HLA-DR expression than the without MMC group. Preclinical analysis revealed similar wound closure, scar index and epidermal thickness between the without and the with MMC groups, largely attributed to issues encountered with the model.

Overall, this preliminary study demonstrates the potential of MMC in the accelerated development of functional and extracellular matrix-rich human BMSC-based tissue-engineered medicines.