WP06 – Long-term pre-clinical in vivo evaluation

Objectives

The objective of work package 06 includes the long-term testing of the 3 favorite materials developed in WP1 that have been produced by the devices constructed in WP02 and evaluated in vitro (WP03) and in vivo (WP05), to set new standards of pre-clinical testing in mini pigs and in the biomechanically challenging equine model. Therefore, we will develop improved methods for scaffold fixation and durable integration in mini pigs and horses. Further, we will decide which the best layered cell-containing HydroZONES constructs are. Finally, we will determine the in vivo performance of 4 improved, second generation layered HydroZONES constructs.

Workpackage Description

Subsequently to previous in vitro testing, the goal of work package 6 comprises the long-term pre-clinical evaluation of hydrogel scaffolds in large animal models. It is generally accepted that animal testing is essential for biological products that are meant to be implanted in human patients. Biocompatibility needs to be tested in a joint environment since the microenvironment and the host immune system might compromise the integration and durability of the developed materials. Currently, no convincing in vitro models that mimic nutrition and oxygen supply as well as the mechanical load in a native joint are available. Thus, it is essential to assess outcome of biomaterial transplantation in joints that resemble human knees in size and cartilage thickness. Together with human and veterinary surgeons we will implant the novel, layered cell-laden and cell-free tissue-engineered hydrogel scaffolds into articular cartilage defects in the joints of mini pigs and horses to assess their potential for successful cartilage regeneration. In close collaboration between the Heidelberg University Hospital, Utrecht University and the University Medical Center Utrecht we will improve the surgical technique to enhance scaffold integration. The involved partners in Germany will work with articular defects in the mini pig model and the researchers from the Netherlands will perform studies in a horse model. Full-thickness cartilage defects will be generated in animal knees (Figure 1) and subsequently filled with the different hydrogel constructs. After integration periods of 6 and 12 months the quality of regeneration will be assessed (Figure 2). Besides the qualitative assessment of various histological, mechanical and biochemical outcome parameters, the quality of regeneration will be assessed by trained personnel by means of a scoring system (modified O’Driscoll score). In this way, these final experiments will reveal the efficacy of cartilage regeneration that can be achieved by the second generation constructs.

Cartilage defects are created on the femur condyles of a mini pig with the help of a curette
Fig. 1: Cartilage defects are created on the femur condyles of a mini pig with the help of a curette. The defects are ready for the implantation of a hydrogel scaffold.
Different qualities of implant integration
Fig. 2: Different qualities of implant integration. Glycosaminoglycans which are a typical feature of cartilage are coloured red by the Safranin O staining used here. The left picture shows lack of integration of an implant to subchondral bone throughout the defect area (no red colouring, marked by asterisk). On the right side a cell-rich and well-regenerating implant can be seen. The arrow indicates the border between native cartilage and the defect area.

WP Leader

Heidelberg University Hospital

Prof. Dr. Wiltrud Richter