Survival and Integration of Transplanted Olfactory Ensheathing Cells are Crucial for Spinal Cord Injury Repair: Insights from the Last 10 Years of Animal Model Studies

Cell Transplantation, 2019 · DOI: 10.1177/0963689719883823 · Published: September 27, 2019

Spinal Cord Injury Regenerative Medicine Neurology

Simple Explanation

Olfactory ensheathing cells (OECs) are special glial cells that support nerve regeneration in the olfactory system, offering potential for treating spinal cord injuries. However, the success of OEC transplantation varies, necessitating improvements and standardization. This review focuses on factors influencing the survival and integration of transplanted OECs in rodent models of spinal cord injury over the past 10 years. Identifying these factors is crucial for enhancing spinal cord regeneration. Two key issues hamper the optimization of OEC transplantation: unreliable methods for identifying transplanted cells and a lack of effective three-dimensional systems for OEC delivery to the injury site.

Study Duration

From 1 week to 1 year

Participants

66 rodent animal studies

Evidence Level

Review of animal model studies

Key Findings

1
OEC survival is influenced by injury type, cell source, co-transplantation with other cells, cell number/concentration, delivery method, and the time between injury and transplantation.
2
The best survival percentage reported following a crush injury was 6.5 + 2.5% out of the 80,000 transplanted cells at 4 weeks post transplantation.
3
Studies comparing olfactory bulb-derived and olfactory mucosa-derived OECs are required, as one study concluded that mucosa-derived OECs exhibit better survival and integration in the transection injury site.

Research Summary

This review highlights that the survival of transplanted cells is crucial for successful outcomes following OEC transplantation into the injured spinal cord and identifies key factors influencing OEC survival after transplantation. Tracking and quantification methods must be improved, including determining differences in protein expression between OECs and SCs and using new innovative methods for labeling transplanted cells such as nuclear probes. New methodologies in which cells are transplanted in three-dimensional constructs which protect the transplanted cells and/or provide stable cell–cell contracts are likely to enhance the therapeutic potential of OEC transplantation.

Practical Implications

Improved Tracking Methods

Develop more reliable methods for tracking transplanted OECs, including identifying protein expression differences between OECs and Schwann cells.

Optimized Transplantation Parameters

Carefully consider factors like injury type, cell source, cell number, and timing of transplantation to maximize OEC survival.

Three-Dimensional Constructs

Explore the use of three-dimensional constructs for OEC delivery to enhance cell survival and integration at the injury site.

Study Limitations

1
The review is limited to rodent spinal cord injury models.
2
Quantification of OEC survival at the injury site is complicated because of the lack of specific OEC markers needed to track the transplanted cells.
3
Most studies did not analyze the inflammatory status of the injury site in relation to OEC survival.

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