Ligament/Tendon Culture under Hypoxic Conditions: A Systematic Review

Hypoxia-Inducible Factor and Oxidative Stress in Tendon Degeneration: A Molecular Perspective

Tendinopathy is a debilitating condition marked by degenerative changes in the tendons. Its complex pathophysiology involves intrinsic, extrinsic, and physiological factors. While its intrinsic and extrinsic factors have been extensively studied, the role of physiological factors, such as hypoxia and oxidative stress, remains largely unexplored. This review article delves into the contribution of hypoxia-associated genes and oxidative-stress-related factors to tendon degeneration, offering insights into potential therapeutic strategies. The unique aspect of this study lies in its pathway-based evidence, which sheds light on how these factors can be targeted to enhance overall tendon health.

Critical appraisal tools used in systematic reviews of in vitro cell culture studies: A methodological study

Systematic reviews (SRs) of preclinical studies are marked with poor methodological quality. In vitro studies lack assessment tools to improve the quality of preclinical research. This methodological study aimed to identify, collect, and analyze SRs based on cell culture studies to highlight the current appraisal tools utilized to support the development of a validated critical appraisal tool for cell culture in vitro research. SRs, scoping reviews, and meta-analyses that included cell culture studies and used any type of critical appraisal tool were included. Electronic search, study selection, data collection and methodological quality (MQ) assessment tool were realized. Further, statistical analyses regarding possible associations and correlations between MQ and collected data were performed. After the screening process, 82 studies remained for subsequent analysis. A total of 32 different appraisal tools were identified. Approximately 60% of studies adopted pre-structured tools not designed for cell culture studies. The most frequent instruments were SYRCLE (n = 14), OHAT (n = 9), Cochrane Collaboration's tool (n = 7), GRADE (n = 6), CONSORT (n = 5), and ToxRTool (n = 5). The studies were divided into subgroups to perform statistical analyses. A significant association (OR = 5.00, 95% CI = 1.54-16.20, p = 0.008) was found between low MQ and chronic degenerative disorders as topic of SR. Several challenges in collecting information from the included studies led to some modifications related to the previously registered protocol. These results may serve as a basis for further development of a critical appraisal tool for cell culture studies capable of capturing all the essential factors related to preclinical research, therefore enhancing the practice of evidence-based.

Tendon cell and tissue culture: Perspectives and recommendations

The wide variety of cell and tissue culture systems used to study and engineer tendons can make it difficult to choose the best approach and "optimal" culture conditions to test a given hypothesis. Therefore, a breakout session was organized at the 2022 ORS Tendon Section Meeting that focused on establishing a set of guidelines for conducting cell and tissue culture studies of tendon. This paper summarizes the outcomes of that discussion and presents recommendations for future studies. In the case of studying tendon cell behavior, cell and tissue culture systems are reductionist models in which the culture conditions should be strictly defined to approximate the in vivo condition as closely as possible. In contrast, for tissue engineering tendon replacements, the culture conditions do not need to replicate native tendon, but the outcome measures for success should be narrowly defined for the specific clinical application. Common recommendations for both applications are that researchers should perform a baseline phenotypic characterization of the cells that are ultimately used for experimentation. For models of tendon cell behavior, culture conditions should be well justified by existing literature and meticulously reported, tissue explant viability should be assessed, and comparisons to in vivo conditions should be made to determine baseline physiological relevance. For tissue engineering applications, the functional/structural/compositional outcome targets should be defined by the specific tendons they seek to replace, with key biologic and material properties prioritized for construct assessment. Lastly, when engineering tendon replacements, researchers should utilize clinically approved cGMP materials to facilitate clinical translation.

Drug Delivery Approaches to Improve Tendon Healing

Tendon injuries disrupt the transmission of forces from muscle to bone, leading to chronic pain, disability, and a large socioeconomic burden. Tendon injuries are prevalent; there are over 300,000 tendon repair procedures a year in the United States to address acute trauma or chronic tendinopathy. Successful restoration of function after tendon injury remains challenging clinically. Despite improvements in surgical and physical therapy techniques, the high complication rate of tendon repair procedures motivates the use of therapeutic interventions to augment healing. While many biological and tissue engineering approaches have attempted to promote scarless tendon healing, there is currently no standard clinical treatment to improve tendon healing. Moreover, the limited efficacy of systemic delivery of several promising therapeutic candidates highlights the need for tendon-specific drug delivery approaches to facilitate translation. This review article will synthesize the current state-of-the-art methods that have been used for tendon-targeted delivery through both systemic and local treatments, highlight emerging technologies used for tissue-specific drug delivery in other tissue systems, and outline future challenges and opportunities to enhance tendon healing through targeted drug delivery.