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Article by Julie Leonard-Duke & Margaretha Morsink
It’s About the Journey not the Destination: How Focusing on the Biomanufacturing Process Improved Tissue Engineered Muscle Recovery After Volumetric Muscle Loss
Source Publication:
Optimized Biomanufacturing for Treatment of Volumetric Muscle Loss Enables Physiomimetic Recovery, Tissue Engineering Part A, 2024
Rachel Bour et al., George Christ Lab
Volumetric muscle loss (VML) occurs when a large portion of muscle is destroyed from injuries like car crashes or combat blasts, and the body can't repair the damage. Current treatments involve transplanting healthy muscle, but with limited success. Tissue-engineered muscle repair (TEMR) has shown promise in repairing VML by creating muscle tissue that integrates with the body. However, some subjects in past studies didn’t respond well, likely due to manufacturing issues. This study uses automated biomanufacturing to improve the quality and consistency of TEMR constructs, reducing potential damage during production.
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What did these researchers do?
This study proposes improving the biomanufacturing process to make TEMR constructs more effective in healing VML injuries. Previous studies showed that TEMR helped some animals recover, but others didn’t respond, likely due to inconsistencies in the manufacturing process. To address this, the authors introduced two key techniques: 1) using a bioprinter to precisely place muscle cells on a scaffold, and 2) using a fully enclosed bioreactor to support cell growth. These methods reduce the risk of damage and improve consistency. The use of bioprinting removes the need for a researcher to manually pipette the cells onto the scaffold minimizing the risk of damage from handling the construct such as by dropping it or touching the surface after cells are placed there. Bioprinting also improves the reproducibility of TEMR constructs as the same parameters for printing can be repeated. The use of a fully enclosed bioreactor environment also minimizing manual handling of the constructs that could cause damage and improves reproducibility. The authors showed that by implementing these techniques in the biomanufacturing process they eliminated the presence of “TEMR nonresponders”, saw earlier functional recovery of the muscle by week 4 as opposed to week 12 with the manually seeded constructs, and promoted muscle fiber growth as measured by fiber cross sectional area.
Why is this important?
Volumetric muscle loss is often the result of a traumatic injury resulting in sever mobility impairments and difficult cosmetic side effects. In addition to traumatic injury causes such as those in combat or car accidents, volumetric muscle loss can also occur as part of genetic conditions leading to the destruction of large volumes of muscle tissue. The current clinical standard of care treatment is to move healthy muscle from another region of the patient’s body to the VML injury sight which has limited functional success, often has cosmetic challenges, and may not be feasible for all patients depending on the extent of muscle damage. Therefore there is a large clinical need for reproducible effective muscle repair treatments, such as TEMR, that can a reproducibility manufactured at a large scale and maintained for implantation as needed. This study represents a big step towards a reproducible, off the shelf muscle repair solution by optimizing the biomanufacturing process.
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How did the researchers do this?
To create TEMR constructs, the researchers first removed the cells from pig bladders, isolating a specific layer called the lamina propria and cutting it into small rectangles. These pieces were placed in a chamber, and muscle cells were added to one side using either a pipette or a bioprinter. The construct was left in a solution for 24 hours, and the process was repeated on the other side. After another 48 hours, the constructs were moved to a fully enclosed bioreactor, where they were stretched every hour for five days to help the muscle cells mature. After this, the TEMR constructs were ready to be tested. To mimic a VML injury, a portion of a rat's back leg muscle (tibialis anterior) was removed, and the TEMR construct was placed in the injury site and stitched in. In control rats, the skin was closed with no repair. At 4, 6, and 12 weeks, the researchers measured the muscle's ability to generate force by stimulating it with an electrical shock. At the end of the study, the muscles were examined for collagen buildup and muscle fiber size.
Fully enclosed bioreactor environment.
What comes next?
This study is an important step toward creating reliable and large-scale tissue-engineered muscle for treating VML injuries. However, a key challenge still remains: scaling up the biomanufacturing process. The TEMRs made in this study are much smaller than what would be needed for human treatments, so testing this technology in larger animal models is crucial to perfect the process for bigger muscle repairs.