Papain Injection Creates a Nucleotomy-like Cavity for Testing Gels in Intervertebral Discs

Area of Science:

• Biomaterials science
• Regenerative medicine
• Biomechanics

Background:

• Biomaterials like hydrogels are crucial for intervertebral disc regeneration.
• Preclinical testing of biomaterials in animal models is challenging due to high intradiscal pressure hindering injection.
• Papain digestion can reduce intradiscal pressure and create cavities for biomaterial injection, but requires time incompatible with short-term cadaver experiments.

Purpose of the Study:

• To develop a new organ culture approach for preclinical testing of biomaterials in intervertebral discs.
• To facilitate papain digestion for creating disc cavities and enabling biomaterial injection.
• To evaluate the biomechanical effects of papain digestion on disc properties and assess its utility as a disease model.

Main Methods:

• A novel organ culture method was established to enable papain digestion within intervertebral discs.
• The method allowed for the assessment of range of motion (ROM), neutral zone (NZ), and disc height post-papain treatment.
• Histology was performed to evaluate proteoglycan content, and hydrogel injectability was quantified.

Main Results:

• Papain treatment significantly increased ROM (up to 109.5%) and extended NZ (up to 210.9%).
• Disc height decreased by 1.96 ± 0.74 mm following papain digestion.
• A median volume of 0.73 mL hydrogel was successfully injected, and histology showed significant proteoglycan loss.

Conclusions:

• The developed organ culture approach successfully facilitates papain digestion and subsequent biomaterial injection in intervertebral discs.
• Papain digestion mimics the biomechanical effects of nucleotomy or herniation, creating a viable in vitro model for disc pathologies.
• This new model is suitable for evaluating the performance of biomaterials intended for intervertebral disc regeneration.