Defining the baseline transcriptional fingerprint of rabbit hamstring autograft

Autophagy Is Involved in Mesenchymal Stem Cell Death in Coculture with Chondrocytes

OBJECTIVE

Cartilage formation is stimulated in mixtures of chondrocytes and human adipose-derived mesenchymal stromal cells (MSCs) both in vitro and in vivo. During coculture, human MSCs perish. The goal of this study is to elucidate the mechanism by which adipose tissue-derived MSC cell death occurs in the presence of chondrocytes.

METHODS

Human primary chondrocytes were cocultured with human MSCs derived from 3 donors. The cells were cultured in monoculture or coculture (20% chondrocytes and 80% MSCs) in pellets (200,000 cells/pellet) for 7 days in chondrocyte proliferation media in hypoxia (2% O₂). RNA sequencing was performed to assess for differences in gene expression between monocultures or coculture. Immune fluorescence assays were performed to determine the presence of caspase-3, LC3B, and P62.

RESULTS

RNA sequencing revealed significant upregulation of >90 genes in the 3 cocultures when compared with monocultures. STRING analysis showed interconnections between >50 of these genes. Remarkably, 75% of these genes play a role in cell death pathways such as apoptosis and autophagy. Immunofluorescence shows a clear upregulation of the autophagic machinery with no substantial activation of the apoptotic pathway.

CONCLUSION

In cocultures of human MSCs with primary chondrocytes, autophagy is involved in the disappearance of MSCs. We propose that this sacrificial cell death may contribute to the trophic effects of MSCs on cartilage formation.

A Versatile Protocol for Studying Anterior Cruciate Ligament Reconstruction in a Rabbit Model

Anterior cruciate ligament (ACL) injuries are frequent, as >200,000 injuries occur in the United States alone each year. Owing to the risks for associated meniscus and cartilage damage, ACL injuries are a significant source of both orthopedic care and research. Given the extended recovery course after ACL injury, which often lasts 1-2 years, and is associated with limited participation in sports and activities of daily living for patients, there is a critical need for the evolution of new and improved methods for ACL repair. Subsequently, animal models of ACL reconstruction (ACLR) play a key role in the development and initial trialing of novel ACL interventions. This article provides a clear operative description and associated illustrations for a validated, institutional animal care and use committee, and veterinarian approved and facile model of ACLR to serve researchers investigating ACLR.

Stem Cell Treatment for Ligament Repair and Reconstruction

PURPOSE OF REVIEW

With the rapid and ongoing evolution of regenerative and sports medicine, the use of stem/stromal cells in ligament repair and reconstruction continues to be investigated and grow. The purpose of this review was to assess available methods and formulations for stem/stromal cell augmentation as well as review early pre-clinical and clinical outcomes for these recently emerging techniques.

RECENT FINDINGS

Recent literature demonstrates promising outcomes of stem/stromal cell augmentation for ligament repair and reconstruction. Multiple groups have published animal models suggesting improved healing for partially transected ligaments as well as histologic re-approximation of native bone-tendon interfaces with the use of mesenchymal stem/stromal cells in reconstructive models. Human studies also suggest improved outcomes spanning from higher patient-reported outcome scores to magnetic resonance imaging evidence of ligament healing in the setting of anterior cruciate ligament tears. However, clinical studies are only recently available, relatively few in number, and not necessarily accompanied by standard-of-care controls. There is increasing availability and growing animal and clinical evidence demonstrating potential benefit of stem/stromal cell augmentation for tendon healing. However, to date, there is a relative paucity of high-level human evidence for the routine use of stem/stromal cells for ligament repair and reconstruction in the clinical practice. This field contains substantial promise and merits further, ongoing investigation.