TITLE: Three-dimensional models of skeletal muscle under tension and methods to induce traumatic injury: systematic review search protocol
AUTHORS: Kunal Bhanot, Robert Staruch

[DESCRIPTION]
Volumetric
muscle loss (VML) is defined as the significant loss of skeletal muscle as a result of traumatic injury or surgical intervention, resulting in functional and regenerative impairment. It is a considerable form of morbidity and is implicated in blast, penetrating or blunt trauma. Current research on VML is centred around models that are not specific to the injury patterns or environments usually encountered. In order to examine the effects of traumatic injury on skeletal muscle, more representative in vitro models are required to generate a deeper cellular picture prior to preclinical validation. Whilst in vivo models are invaluable, they are expensive and have a lower throughput platform for discovery research. The aim of this systematic review is to examine the types of in vitro muscle models that are applicable to understanding VML. We have therefore designed an inclusive search protocol to incorporate all relevant muscle models under tension and endeavour to subcategorise these depending on methods of inducing injury. “Skeletal muscle” was the major inclusion criterion, followed by “three dimensional” and “model”. The Ovid interface was used to search MEDLINE, EMBASE and Web of Science Core Collection databases to yield 4,895 eligible articles after de-duplication. As of 30/05/2024 articles are in the process of being blindly screened by two independent reviewers. Major inclusion criteria are three dimensional in vitro models under tension. A sub analysis will subsequently be performed to examine how injury is induced in such muscle models. 

[STEPS]
SECTION: Methods
1. This systematic review was reported in compliance with the PRISMA 2020 checklist. The protocol was developed prospectively in collaboration with a research librarian (NT) at the Nuffield Department of Rheumatology and Musculoskeletal Sciences (NDORMS).
2. All databases were searched from inception until 13/03/2024. The Ovid interface was used to search MEDLINE (1946-present), EMBASE (1974-present) and Web of Science Core Collection (1900-present) databases. No date or language limits were applied. Synonyms were produced in line with elements of the research question. “Skeletal muscle” was the major inclusion criterion, followed by “three dimensional” and “model”. Synonyms for skeletal muscle included “myotube”, “slow-twitch muscle fibres” and “fast-twitch muscle fibres”. Synonyms for “three-dimensional” included “3D”, “organoid” and “lab on a chip”. Synonyms for “model” included “scaffold”, “architecture” and “platform”. Full search strategies can be found in the appendix. 
SECTION: Inclusion criteria
3. In vitro studies that utilised any skeletal muscle cell lines (primary or immortalised, single or multicellular) of any species cultured with an anchor system were eligible for inclusion. Models that used organic hydrogel compounds native to the human body (fibrin or collagen) were included. Where studies reported minor experimental modifications of previously reported models (with detailed methods), the most comprehensive study or studies were included.
SECTION: Exclusion criteria
4. Models that did not impose axial strain or loading, self-assembly models (spheroids etc) or tissue explant models (including slice culture) were excluded. In vitro models that cultured cells on patterned surfaces (to include orientation) were also excluded, even if they used 3D systems. In vitro monolayer systems were excluded. Ex vivo perfusion systems were also excluded. Models that synthesised hydrogels using materials that were incapable of biodegradation (breakdown of organic matter into constituent elements) within humans (or human tissue) were excluded. Studies without detailed methods, opinion pieces, reviews, letters, conference abstracts, in vivo work and book chapters were excluded.
SECTION: Appendix
5. EMBASE search:

 
 
 
SECTION: Appendix
6. MEDLINE search:

 
 
 
SECTION: Appendix
7. Web of science search strategy:

Search
Strategy                                   
#          Search Query  Database         Results
1          "myotube OR (skeletal NEAR/2
myoblast*) OR ""skeletal muscle"" OR ""fast
twitch muscle fibre*"" OR ""slow twitch muscle
fibre*"" OR (skeletal NEAR/2 myocyte*)  (Topic) AND 3d OR ""three
dimension*"" OR ""three d"" OR organoid* OR
""lab on a chip"" OR ""organ on a
chip"" OR bioengineer* OR ""tissue engineer*"" OR
""biological engineer*"" 
(Topic) AND model* OR scaffold* OR architecture* OR platform* OR system
OR systems  (Topic)                            "          
 
Web of
Science Core Collection         2811