A pilot study of poly(N-isopropylacrylamide)-g-polyethylene glycol and poly(N-isopropylacrylamide)-g-methylcellulose branched copolymers as injectable scaffolds for local delivery of neurotrophins and cellular transplants into the injured spinal cord: Laboratory investigation

J Neurosurg Spine, 2011 · DOI: 10.3171/2011.7.SPINE11194 · Published: December 1, 2011

Simple Explanation

The study explores using injectable hydrogels made from poly(N-isopropylacrylamide) (PNIPAAm) combined with polyethylene glycol (PEG) or methylcellulose (MC) as scaffolds to deliver neurotrophins and cells to damaged spinal cords. The primary goals were to see if these scaffolds were biocompatible, meaning they wouldn't harm the host tissue, and if they could encourage axon growth, which is crucial for spinal cord repair. The hydrogels were injected as liquids and formed space-filling gels at the injury site. The scientists then examined the immune response and the survival of grafted cells.

Study Duration

2 Weeks

Participants

Adult female Sprague-Dawley rats (weighing approximately 225–250 g)

Evidence Level

Not specified

Key Findings

1
The scaffolds did not worsen inflammation related to the injury.
2
PNIPAAm-g-PEG was an effective way to deliver cell transplants and supported the survival of the transplanted cells.
3
Both PNIPAAm-g-PEG and PNIPAAm-g-MC allowed axon growth and could be used as scaffolds for delivering brain-derived neurotrophic factor (BDNF).

Research Summary

The authors investigated the feasibility of using injectable hydrogels, based on poly(N-isopropylacrylamide) (PNIPAAm), lightly crosslinked with polyethylene glycol (PEG) or methylcellulose (MC), to serve as injectable scaffolds for local delivery of neurotrophins and cellular transplants into the injured spinal cord. Experiments showed that the scaffolds did not contribute to an injury-related inflammatory response. PNIPAAm-g-PEG was also shown to be an effective vehicle for delivery of cellular transplants and supported graft survival. Based on the results, the authors suggest that these copolymers are feasible injectable scaffolds for cell grafting into the injured spinal cord and for delivery of therapeutic factors.

Practical Implications

Potential for SCI Treatment

The hydrogels offer a promising method for delivering cells and growth factors to spinal cord injuries, potentially improving recovery.

Improved Delivery Method

The injectable nature of the hydrogels allows for easier implantation into irregularly shaped injury sites compared to preformed scaffolds.

Biocompatible Scaffold

The materials do not appear to worsen inflammation or glial scar formation, suggesting they are well-tolerated by the body.

Study Limitations

1
Small sample sizes (3 rats per group) limited the statistical power of the study.
2
Hydrogels were washed away during perfusion with cold PFA in Groups 2–5, making examination of degradation difficult.
3
Quantification of axonal growth was not performed.

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