Sizes and Sufficient Quantities of MSC Microspheres for Intrathecal Injection to Modulate Inflammation in Spinal Cord...

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.