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Sizes and Sufficient Quantities of MSC Microspheres for Intrathecal Injection to Modulate Inflammation in Spinal Cord
Suneel Kumar1, Joanne Babiarz1, Sayantani Basak1
1Department of Cell Biology & Neuroscience, Rutgers University, 604 Allison Rd., Piscataway, NJ 08854 USA.
Abstract:
Microencapsulation of mesenchymal stem cells (MSC) in alginate facilitates cell delivery, localization and survival, and modulates inflammation in vivo. However, we found that delivery of the widely used ~0.5 mm diameter encapsulated MSC (eMSC) by intrathecal injection into spinal cord injury (SCI) rats was highly variable. Injections of smaller (~0.2 mm) diameter eMSC into the lumbar spine were much more reproducible and they increased the anti-inflammatory macrophage response around the SCI site. We now report that injection of small eMSC >2 cm caudal from the rat SCI improved locomotion and myelin preservation 8 weeks after rat SCI versus control injections. Because preparation of sufficient quantities of small eMSC for larger studies was not feasible and injection of the large eMSC is problematic, we have developed a procedure to prepare medium-sized eMSC (~0.35 mm diameter) that can be delivered more reproducibly into the lumbar rat spine. The number of MSC incorporated/capsule in the medium sized capsules was ~5-fold greater than that in small capsules and the total yield of eMSC was ~20-fold higher than that for the small capsules. Assays with all three sizes of eMSC capsules showed that they inhibited TNF-α secretion from activated macrophages in co-cultures, suggesting no major difference in their anti-inflammatory activity in vitro. The in vivo activity of the medium-sized eMSC was tested after injecting them into the lumbar spine 1 day after SCI. Histological analyses 1 week later showed that eMSC reduced levels of activated macrophages measured by IB4 staining and increased white matter sparing in similar regions adjacent to the SCI site. The combined results indicate that ~0.35 mm diameter eMSC reduced macrophage inflammation in regions where white matter was preserved during critical early phases after SCI. These techniques enable preparation of eMSC in sufficient quantities to perform pre-clinical SCI studies with much larger numbers of subjects that will provide functional analyses of several critical parameters in rodent models for CNS inflammatory injury.
Insights
Optimizing mesenchymal stem cell (MSC) delivery for spinal cord injury (SCI) involves using medium-sized microcapsules (~0.35 mm) for reproducible injection and enhanced therapeutic effects in rats.
Area of Science:
- Regenerative Medicine
- Neuroscience
- Biomaterials Science
Background:
- Alginate microencapsulation of mesenchymal stem cells (MSC) aids delivery and survival but faces challenges with large capsule sizes (~0.5 mm) for spinal cord injury (SCI) treatment.
- Smaller microencapsulated MSC (~0.2 mm) show reproducible delivery and anti-inflammatory effects in SCI models, but their preparation is not scalable.
Purpose of the Study:
- To develop a scalable method for preparing medium-sized microencapsulated MSC (~0.35 mm) for reproducible delivery and therapeutic efficacy in a rat spinal cord injury model.
- To evaluate the in vitro anti-inflammatory capacity and in vivo therapeutic potential of medium-sized microencapsulated MSC in a rat SCI model.
Main Methods:
- Developed a procedure for preparing medium-sized (~0.35 mm) alginate microencapsulated MSC (eMSC), achieving a ~20-fold higher yield compared to small eMSC.
- Assessed in vitro anti-inflammatory activity by co-culturing eMSC of various sizes with activated macrophages to measure TNF-α secretion.
- Administered medium-sized eMSC intrathecally into the lumbar spine of SCI rats and evaluated locomotion, myelin preservation, macrophage activation (IB4 staining), and white matter sparing at 8 weeks post-injury.
Main Results:
- Medium-sized eMSC capsules yielded ~5-fold more MSC per capsule than small capsules, enabling scalable preparation.
- All tested eMSC sizes demonstrated in vitro inhibition of TNF-α secretion from activated macrophages.
- In vivo, medium-sized eMSC injections reduced activated macrophage levels and increased white matter sparing adjacent to the SCI site, improving locomotion and myelin preservation.
Conclusions:
- Medium-sized (~0.35 mm) microencapsulated MSC offer a reproducible and scalable delivery method for SCI treatment.
- These eMSC effectively reduce inflammation and promote tissue preservation in the critical early phases following spinal cord injury.
- The developed technique facilitates pre-clinical SCI studies with larger cohorts, enabling comprehensive functional and histological analyses in rodent models of CNS inflammatory injury.
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