Ligament-Derived Stem Cells: Identification, Characterisation, and Therapeutic Application

Regulatory Mechanism between Ferritin and Mitochondrial Reactive Oxygen Species in Spinal Ligament-Derived Cells from Ossification of Posterior Longitudinal Ligament Patient

Primary spinal ligament-derived cells (SLDCs) from cervical herniated nucleus pulposus tissue (control, Ctrl) and ossification of the posterior longitudinal ligament (OPLL) tissue of surgical patients were analyzed for pathogenesis elucidation. Here, we found that decreased levels of ferritin and increased levels of alkaline phosphatase (ALP), a bone formation marker, provoked osteogenesis in SLDCs in OPLL. SLDCs from the Ctrl and OPLL groups satisfied the definition of mesenchymal stem/stromal cells. RNA sequencing revealed that oxidative phosphorylation and the citric acid cycle pathway were upregulated in the OPLL group. SLDCs in the OPLL group showed increased mitochondrial mass, increased mitochondrial reactive oxygen species (ROS) production, decreased levels of ROS scavengers including ferritin. ROS and ferritin levels were upregulated and downregulated in a time-dependent manner, and both types of molecules repressed ALP. Osteogenesis was mitigated by apoferritin addition. We propose that enhancing ferritin levels might alleviate osteogenesis in OPLL.

Intraligamentous synovial osteochondroma of the ligamentum teres: a series of 14 cases

BACKGROUND

The ligamentum teres (LT) is covered by synovium. It acts as a stabilizer of the hip and as such it has been compared to the ACL of the knee joint. Pathologic changes occur in the LT with aging and osteoarthritis (OA), including degeneration, occasional chondroid metaplasia, and synovial chondromatosis are well-recognized in the literature. However, there are no reports of intraligamentous synovial osteochondroma occuring in the LT.

METHODS

We reviewed the pathology reports of 542 osteoarthritic femoral arthroplasty specimens between January 2016 and December 2018. The LT was examined histologically in 55 cases because it was abnormal on gross examination.

RESULTS

A single synovial osteochondroma, ranging in size from 0.4-1.7 cm in diameter, was present in the body of the LT in 14 cases (9 males; 5 females, aged 34 to 81 years), representing 2.6% of 542 arthroplasty cases. Ten of the osteochondromas had bone marrow fat without hematopoietic elements, 1 had hematopoietic elements, and 3 had no marrow among the bony trabeculae. Radiographically, all cases had moderate to severe osteoarthritis with no mention of an abnormality of LT.

CONCLUSION

To our knowledge, this is the first report of intraligamentous synovial osteochondroma in the LT in osteoarthritis patients undergoing hip arthroplasty. It provides further support for microscopic examination of arthroplasty specimens for histologic abnormalities. Further prospective study is needed to determine if this lesion contributes adversely to the development or progression of osteoarthritis and if it is a reactive or neoplastic process.

The impact of cryopreservation in signature markers and immunomodulatory profile of tendon and ligament derived cells

Tendon and ligament (T/L) engineering strategies towards clinical practice have been challenged by a paucity of understanding in the identification and still poorly described characterization of cellular niches. Prospecting how resident cell populations behave in vitro, and how cryopreservation may influence T/ L-promoting factors, can provide insights into T/ L-cellular profiles for novel regenerative solutions. Therefore, we studied human T/ L-derived cells isolated from patellar tendons and cruciate ligaments as suitable cellular models to anticipate tendon and ligament niches responses for advanced strategies with predictive tenogenic and ligamentogenic value. Our results show that the crude populations isolated from tendon and ligament tissues hold a stem cell subset and share a similar behavior in terms of tenogenic/ligamentogenic commitment. Both T/ L-derived cells successfully undergo cryopreservation/thawing maintaining the tenogenic/ligamentogenic profiles. The major differences between cryopreserved and fresh populations were observed at the gene expression of MKX, SCX, and TNMD as well as at the protein levels of collagen type I and III, in which cells from tendon origin (hTDCs) evidence increased values in comparison to the ones from ligament (hLDCs, p < 0.05). In addition, low-temperature storage was shown to potentiate an immunomodulatory profile of cells, especially in hTDCs leading to an increase in the gene expression of the anti-inflammatory factors IL-4 and IL-10 (p < 0.05), as well as in the protein secretion of IL-10 (p < 0.01) and IL-4 (p < 0.001). Overall, the outcomes highlight the relevance of the cryopreserved T/ L-derived cells and their promising immunomodulatory cues as in vitro models for investigating cell-mediated mechanisms driving tissue healing and regeneration.

Implementation of Endogenous and Exogenous Mesenchymal Progenitor Cells for Skeletal Tissue Regeneration and Repair

Harnessing adult mesenchymal stem/progenitor cells to stimulate skeletal tissue repair is a strategy that is being actively investigated. While scientists continue to develop creative and thoughtful ways to utilize these cells for tissue repair, the vast majority of these methodologies can ultimately be categorized into two main approaches: (1) Facilitating the recruitment of endogenous host cells to the injury site; and (2) physically administering into the injury site cells themselves, exogenously, either by autologous or allogeneic implantation. The aim of this paper is to comprehensively review recent key literature on the use of these two approaches in stimulating healing and repair of different skeletal tissues. As expected, each of the two strategies have their own advantages and limitations (which we describe), especially when considering the diverse microenvironments of different skeletal tissues like bone, tendon/ligament, and cartilage/fibrocartilage. This paper also discusses stem/progenitor cells commonly used for repairing different skeletal tissues, and it lists ongoing clinical trials that have risen from the implementation of these cells and strategies. Lastly, we discuss our own thoughts on where the field is headed in the near future.

Cell Therapy-a Basic Science Primer for the Sports Medicine Clinician

PURPOSE OF REVIEW

The emergence of cell-based therapies has brought much excitement to the field of orthopedic sports medicine. However, the significant inconsistency of reporting has led to the poor understanding, misinformation, and false expectations for patients and clinicians alike. In this paper, we aim to clarify the available cell-therapy treatments and summarize some of the latest research.

RECENT FINDINGS

Although this technology is in early development, our understanding of cell biology has grown significantly over the last decade. Furthermore, it is becoming evident that tissue specificity may play a significant role in determining the effectiveness and overall clinical benefit attributed to cell therapy. Cell therapy is an emerging field with tremendous potential for clinically significant benefit. However, in its current state, clinical application of these treatments is limited by federal regulations, variability in formulation, and limited understanding of the biologic activity of various cell formulations.

Proteomic analysis of synovial fluid identifies periostin as a biomarker for anterior cruciate ligament injury

OBJECTIVE

Emerging evidence suggests that injury to the anterior cruciate ligament (ACL) typically initiates biological changes that contribute to the development of osteoarthritis (OA). The molecular biomarkers or mediators of these biological events remain unknown. The goal of this exploratory study was to identify novel synovial fluid biomarkers associated with early biological changes following ACL injury distinct from findings in end-stage OA.

METHODS

Synovial fluid was aspirated from patients with acute (≤30 days) and subacute (31-90 days) ACL tears and from patients with advanced OA and probed via tandem mass spectrometry for biomarkers to distinguish OA from ACL injury. Periostin (POSTN) was identified as a potential candidate. Further analyses of POSTN were performed in synovial fluid, OA cartilage, torn ACL remnants, and cultured cells and media by Western blot, PCR, immunostaining and ELISA.

RESULTS

Synovial fluid analysis revealed that POSTN exhibited higher expression in subacute ACL injury than OA. POSTN expression was relatively low in cartilage/chondrocytes suggesting it is also produced by other intra-articular tissues. Conversely, high and time-dependent expression of POSTN in ACL tear remnants and isolated cells was consistent with the synovial fluid results.

CONCLUSIONS

Elevated POSTN may provide a synovial fluid biomarker of subacute ACL injury setting separate from OA. Increased expression of POSTN in ACL suggests that the injured ACL may play a pivotal role in POSTN production, which is sensitive to time from injury. Previous studies have shown potential catabolic effects of POSTN, raising the possibility that POSTN contributes to the initiation of joint degeneration and may offer a window of opportunity to intervene in the early stages of post-traumatic OA.

Migrating Myofibroblastic Iliotibial Band-Derived Fibroblasts Represent a Promising Cell Source for Ligament Reconstruction

The iliotibial band (ITB) is a suitable scaffold for anterior cruciate ligament (ACL) reconstruction, providing a sufficient mechanical resistance to loading. Hence, ITB-derived fibroblasts attract interest for ligament tissue engineering but have so far not been characterized. This present study aimed at characterizing ITB fibroblasts before, during, and after emigration from cadaveric ITB explants to decipher the emigration behavior and to utilize their migratory capacity for seeding biomaterials. ITB and, for comparison, ACL tissues were assessed for the content of alpha smooth muscle actin (αSMA) expressing fibroblasts and degeneration. The cell survival and αSMA expression were monitored in explants used for cell isolation, monolayer, self-assembled ITB spheroids, and spheroids seeded in polyglycolic acid (PGA) scaffolds. The protein expression profile of targets typically expressed by ligamentocytes (collagen types I-III, elastin, lubricin, decorin, aggrecan, fibronectin, tenascin C, CD44, β1-integrins, vimentin, F-actin, αSMA, and vascular endothelial growth factor A [VEGFA]) was compared between ITB and ACL fibroblasts. A donor- and age-dependent differing percentage of αSMA positive cells could be detected, which was similar in ITB and ACL tissues despite the grade of degeneration being significantly higher in the ACL due to harvesting them from OA knees. ITB fibroblasts survived for several months in an explant culture, continuously forming monolayers with VEGFA and an increased αSMA expression. They shared their expression profile with ACL fibroblasts. αSMA decreased during the monolayer to spheroid/scaffold transition. Using self-assembled spheroids, the migratory capacity of reversible myofibroblastic ITB cells can be utilized for colonizing biomaterials for ACL tissue engineering and to support ligament healing.