Research perspectives—Pipelines to human tendon transcriptomics

Abstract

Tendon transcriptomics is a rapidly growing field in musculoskeletal biology. The ultimate aim of many current tendon transcriptomic studies is characterization of in vitro, ex vivo, or in vivo, healthy, and diseased tendon microenvironments to identify the underlying pathways driving human tendon pathology. The transcriptome interfaces between genomic, proteomic, and metabolomic signatures of the tendon cellular niche and the response of this niche to stimuli. Some of the greatest bottlenecks in tendon transcriptomics relate to the availability and quality of human tendon tissue, hence animal tissues are frequently used even though human tissue is most translationally relevant. Here, we review the variability associated with human donor and procurement factors, such as whether the tendon is cadaveric or a clinical remnant, and how these variables affect the quality and relevance of the transcriptomes obtained. Moreover, age, sex, and health demographic variables impact the human tendon transcriptome. Tendons present tissue‐specific challenges for cell, nuclei, and RNA extraction that include a dense extracellular matrix, low cellularity, and therefore low RNA yield of variable quality. Consideration of these factors is particularly important for single‐cell and single‐nuclei resolution transcriptomics due to the necessity for unbiased and representative cell or nuclei populations. Different cell, nuclei, and RNA extraction methods, library preparation, and quality control methods are used by the tendon research community and attention should be paid to these when designing and reporting studies. We discuss the different components and challenges of human tendon transcriptomics, and propose pipelines, quality control, and reporting guidelines for future work in the field.

Single nucleus and spatial transcriptomic profiling of healthy human hamstring tendon

“…14 Technical challenges in working with ECM-rich tissues alongside limited access to healthy comparative tissue from humans continues to impede progress in the field of tendon biology. 6,7 This has made it difficult to obtain a detailed cellular profile of healthy tendons. To better understand the cellular states, functions, and interactions that underlie hamstring tendon health, a broader and spatially resolved dataset is needed.…”

“…Other published single cell or single nucleus transcriptomics studies on tendon have either used a different microanatomical region of the hamstring tendon, 10 different type of tendon, 11,12 or passaged cells, 12,13 which are known to be vulnerable to phenotypic drift in culture 14 . Technical challenges in working with ECM‐rich tissues alongside limited access to healthy comparative tissue from humans continues to impede progress in the field of tendon biology 6,7 . This has made it difficult to obtain a detailed cellular profile of healthy tendons.…”

“…Although the diverse cellular environment of tendons has been well documented, the interactions and relationships between these cell types have not yet been fully characterized. Understanding the cellular composition of healthy human tendon is crucial for identifying the pathways and relationships that are disrupted in disease, enabling development of new pharmaceutical targets and biomaterials 6,7 …”

Single nucleus and spatial transcriptomic profiling of human healthy hamstring tendon

“…Currently, progress in the field of tendon biology is hindered by accessibility of healthy comparative tissue and the technical challenges posed by ECM-rich tissues [6,7].…”

“…Insight into the cellular composition of healthy tendon is vital to unravel pathways and relationships dysregulated in disease, enabling the identification of new pharmaceutical targets and better design of biomaterials. Currently, progress in the field of tendon biology is hindered by accessibility of healthy comparative tissue and the technical challenges posed by ECM-rich tissues[6, 7].…”