# Establishment and characterization of a rat model of scalp-cranial composite defect for multilayered tissue engineering

## TL;DR

This paper introduces a rat model for studying scalp-cranial composite defects, enabling long-term research on tissue engineering and healing.

## Contribution

A novel rat model with a 3D-printed wound obturator to maintain chronic composite defects for tissue engineering studies.

## Key findings

- The wound obturator prevents scalp healing for over 6 weeks while preserving the cranial defect.
- The model shows minimal biotoxicity and avoids endocranium-granulation adhesion.
- An autologous reconstruction model was developed as a positive control with reproducible healing.

## Abstract

Composite cranial defects have individual functional and aesthetic ramifications, as well as societal burden, while posing significant challenges for reconstructive surgeons. Single-stage composite reconstruction of these deformities entail complex surgeries that bear many short- and long-term risks and complications. Current research on composite scalp-cranial defects is sparse and one-dimensional, often focusing solely on bone or skin. Thus, there is an unmet need for a simple, clinically relevant composite defect model in rodents, where there is a challenge in averting healing of the skin component via secondary intention. By utilizing a customizable (3D-printed) wound obturator, the scalp wound can be rendered non-healing for a long period (more than 6 weeks), with the cranial defect patent. The wound obturator shows minimal biotoxicity and will not cause severe endocranium-granulation adhesion. This composite defect model effectively slowed the scalp healing process and preserved the cranial defect, embodying the characteristics of a “chronic composite defect”. In parallel, an autologous reconstruction model was established as the positive control. This positive control exhibited reproducible healing of the skin within 3 weeks with variable degrees of osseointegration, consistent with clinical practice. Both models provide a stable platform for subsequent research not only for composite tissue engineering and scaffold design but also for mechanistic studies of composite tissue healing.