CARGEL Bioscaffold improves cartilage repair tissue after bone marrow stimulation in a minipig model

Injectable hydrogels: An emerging therapeutic strategy for cartilage regeneration

The impairment of articular cartilage due to traumatic incidents or osteoarthritis has posed significant challenges for healthcare practitioners, researchers, and individuals suffering from these conditions. Due to the absence of an approved treatment strategy for the complete restoration of cartilage defects to their native state, the tissue condition often deteriorates over time, leading to osteoarthritic (OA). However, recent advancements in the field of regenerative medicine have unveiled promising prospects through the utilization of injectable hydrogels. This versatile class of biomaterials, characterized by their ability to emulate the characteristics of native articular cartilage, offers the distinct advantage of minimally invasive administration directly to the site of damage. These hydrogels can also serve as ideal delivery vehicles for a diverse range of bioactive agents, including growth factors, anti-inflammatory drugs, steroids, and cells. The controlled release of such biologically active molecules from hydrogel scaffolds can accelerate cartilage healing, stimulate chondrogenesis, and modulate the inflammatory microenvironment to halt osteoarthritic progression. The present review aims to describe the methods used to design injectable hydrogels, expound upon their applications as delivery vehicles of biologically active molecules, and provide an update on recent advances in leveraging these delivery systems to foster articular cartilage regeneration.

The Effect of Bone Marrow Stimulation for Cartilage Repair on the Subchondral Bone Plate

PURPOSE

To investigate the effect of bone-marrow stimulation (BMS) on subchondral bone plate morphology and remodeling compared to untreated subchondral bone in a validated minipig model.

METHODS

Three Göttingen minipigs received BMS with drilling as treatment for two chondral defects in each knee. The animals were euthanized after six months. Follow-up consisted of a histological semiquantitative evaluation using a novel subchondral bone scoring system and micro computed tomography (µCT) of the BMS subchondral bone. The histological and microstructural properties of the BMS-treated subchondral bone were compared to that of the adjacent healthy subchondral bone.

RESULTS

The µCT analysis showed that subchondral bone treated with BMS had significantly higher connectivity density compared to adjacent untreated subchondral bone (26 1/mm³ vs. 21 1/mm³, P = 0.048). This was the only microstructural parameter showing a significant difference. The histological semiquantitative score differed significantly between the subchondral bone treated with BMS and the adjacent untreated subchondral (8.0 vs. 10 P = < 0.001). Surface irregularities were seen in 43% and bone overgrowth in 27% of the histological sections. Only sparse formation of bone cysts was detected (1%).

CONCLUSIONS

BMS with drilling does not cause extensive changes to the subchondral bone microarchitecture. Furthermore, the morphology of BMS subchondral bone resembled that of untreated subchondral bone with almost no formation of bone cyst, but some surface irregularities and bone overgrowth.

Biological Augments for Acetabular Chondral Defects in Hip Arthroscopy-A Scoping Review of the Current Clinical Evidence

PURPOSE OF REVIEW

A wide array of joint-preserving surgical techniques exists in the management of acetabular chondral defects (ACDs). The purpose of this review is to summarize the clinical outcomes of the recent biologics used to treat ACDs during hip arthroscopy.

RECENT FINDINGS

Increasing evidence is available for different biological solutions used in the hip. Studies have shown promising outcomes with minimal complications when using biologics as augmentation to microfracture (MF), including different scaffolds or stem cells, or to enhance autologous chondrocyte implantation (ACI). However, data so far is scarce, and more trials and longer follow-ups are needed to better delineate the appropriate indications and benefits for each technique. Presently, the level of evidence is low, but in general, biologics appear safe and trend toward beneficial compared to standard surgical techniques. Augmented MF is recommended for small to medium ACDs, and matrix-assisted ACI or three-dimensional ACI is recommended for medium to large defects.

Mesenchymal Stem Cell Extracellular Vesicles as Adjuvant to Bone Marrow Stimulation in Chondral Defect Repair in a Minipig Model

OBJECTIVE

This study evaluated the effects of mesenchymal stem cell-extracellular vesicles (MSC-EVs) on chondrocyte proliferation in vitro and on cartilage repair in vivo following bone marrow stimulation (BMS) of focal chondral defects of the knee.

METHODS

Six adult Göttingen minipigs received 2 chondral defects in each knee. The pigs were randomized to treatment with either BMS combined with MSC-EVs or BMS combined with phosphate-buffered saline (PBS). Intraarticular injections MSC-EVs or PBS were performed immediately after closure of the surgical incisions, and at 2 and 4 weeks postoperatively. Repair was evaluated after 6 months with gross examination, histology, histomorphometry, immunohistochemistry, and micro-computed tomography (µCT) analysis of the trabecular bone beneath the defect.

RESULTS

Defects treated with MSC-EVs had more bone in the cartilage defect area than the PBS-treated defects (7.9% vs. 1.5%, P = 0.02). Less than 1% of the repair tissue in both groups was hyaline cartilage. International Cartilage and Joint Preservation Society II histological scoring showed that defects treated with MSC-EVs scored lower on "matrix staining" (20.8 vs. 50.0, P = 0.03), "cell morphology" (35.4 vs. 53.8, P = 0.04), and "overall assessment" (30.8 vs. 52.9, P = 0.03). Consistently, defects treated with MSC-EVs had lower collagen II and higher collagen I areal deposition. Defects treated with MSC-EVs had subchondral bone with significantly higher tissue mineral densities than PBS-treated defects (860 mg HA/cm3 vs. 838 mg HA/cm3, P = 0.02).

CONCLUSION

Intraarticular injections of MSC-EVs in conjunction with BMS led to osseous ingrowth that impaired optimal cartilage repair, while enhancing subchondral bone healing.

Multi-layer cell-free scaffolds for osteochondral defects of the knee: a systematic review and meta-analysis of clinical evidence

Purpose

The aim of this study was to analyze the clinical results provided by multi-layer cell-free scaffolds for the treatment of knee osteochondral defects.

Methods

A systematic review was performed on PubMed, Web of Science, and Cochrane to identify studies evaluating the clinical efficacy of cell-free osteochondral scaffolds for knee lesions. A meta-analysis was performed on articles reporting results of the International Knee Documentation Committee (IKDC) and Tegner scores. The scores were analyzed as improvement from baseline to 1, 2, and ≥ 3 years of follow-up. The modified Coleman Methodology Score was used to assess the study methodology.

Results

A total of 34 studies (1022 patients) with a mean follow-up of 35 months was included. Only three osteochondral scaffolds have been investigated in clinical trials: while TruFit® has been withdrawn from the market for the questionable results, the analysis of MaioRegen and Agili-C™ provided clinical improvements at 1, 2, and ≥ 3 years of follow-up (all significantly higher than the baseline, p < 0.05), although with a limited recovery of the sport-activity level. A low rate of adverse events and an overall failure rate of 7.0% were observed, but the overall evidence level of the available studies is limited.

Conclusions

Multi-layer scaffolds may provide clinical benefits for the treatment of knee osteochondral lesions at short- and mid-term follow-up and with a low number of failures, although the sport-activity level obtained seems to be limited. Further research with high-level studies is needed to confirm the role of multi-layer scaffold for the treatment of knee osteochondral lesions.

Single-Stage Arthroscopic Cartilage Repair With Injectable Scaffold and BMAC

Injectable scaffold augmentation is a promising modality for single-stage cartilage repair. According to published studies, cartilage repair with scaffold augmentation has improved clinical outcomes, radiological fill, and histological repair compared with microfracture alone. Injectable scaffolds have the versatility to be used in large and irregularly shaped lesions. With correct preparation, they can be applied to lesions on the femoral condyle that may be vertical, or even inverted lesions such as those in the patella. They can be combined with bone marrow aspirate concentrate (BMAC) to provide mesenchymal stem cells (MSCs), thereby avoiding the need for microfracture. This protects the subchondral plate, preventing biomechanical alteration and potentially resulting in improved long-term outcomes. In this article, we demonstrate the utility of injectable scaffolds and their combination with BMAC.