Korpershoek, Jasmijn V.

ABSTRACT In cartilage tissue engineering, there is a growing interest in dynamic hydrogels that promote spheroid fusion and cartilaginous matrix deposition, while maintaining sufficient stability for long‐term construct maturation. In this study, Diels‐Alder click chemistry is employed as a dynamic‐covalent crosslinking method to create hydrogels composed of hyaluronic acid, gelatin, and PEG. By adjusting the pH during crosslinking, the tuneability of hydrogel stiffness and stability at pH values around the physiological pH of native cartilage is demonstrated. This pH modulation does not compromise hydrogel functionality, as encapsulated equine articular cartilage progenitor cell spheroids remain viable and functional for a culture period of 28 days. The hydrogel environment supports the deposition of cartilaginous extracellular matrix components, including collagens and sulphated glycosaminoglycans. Enhanced chondrogenesis and deposition of collagen type II are observed at higher spheroid concentrations, corresponding to inter‐spheroid distances of 100–150 µm following hydrogel swelling, compared to lower concentrations at a distance of >500 µm. To further improve construct robustness, the hydrogel constructs can be reinforced on day 1 with a melt electrowritten scaffold, increasing the compressive modulus 100‐fold by day 28 compared to non‐reinforced constructs, highlighting the potential of this system for engineering cartilage implants.

ABSTRACT Premature physeal closure occurs following trauma, cancer, or infection. Current treatments have poor success rates. With recent pediatric donor tissue availability, physeal allograft transfer (PAT) can now be considered. The purpose of this study was to study the safety and feasibility of PAT in a large animal model. The aim of this study is to gather foundational data to inform future studies into the efficacy of PAT. Physeal defects were created in the distal femur of nine female domestic swine and treated with PAT from two male donor pigs, cementation, or bone autograft. Viability was assessed. After 3 months, physes were visualized using CT and MRI. Integration, tissue composition, donor DNA presence, and microscopic appearance were evaluated. Physeal allografts demonstrated 93% viability after procurement and preservation. All animals reached the 3‐months study endpoint without gross deformations. No physeal bars formed in any group. Cystic changes were seen in experimental and control femurs. All groups showed disorganized tissue architecture without growth plate recapitulation. High allografts viability and structural integrity after procurement support the potential of this treatment. Although no gross deformities were found, transferred physes demonstrate poor integration and incomplete repair. The lack of physeal bar formation in the control group limits the reliability of the animal model for studying physeal allograft transfer. Lastly, this study was designed as a feasibility study and lacks power to compare treatment effects statistically. The efficacy of PAT for preventing growth arrest remains undetermined.

Objectives Damaged articular cartilage cannot regenerate spontaneously. Chondrocyte therapy, the current treatment of choice, requires laboratory expansion, necessitating two surgical procedures. Adding a second cell type to intraoperatively isolated chondrocytes enables single-stage chondrocyte-based repair strategies and has shown promise in vitro . The benefit of this strategy in vivo and in the clinic has not yet been comprehensively assessed. This systematic review assesses the efficacy of cartilage repair by co-implantations of chondrocytes with other cell types over all available in vivo studies. Design Medline, Embase and Cochrane databases were searched for studies on co-implantations of chondrocytes with other cell types for hyaline cartilage repair. For each study, extracted data were tabulated and reporting quality and risk of bias were assessed. Studies were categorized based on their control groups for qualitative synthesis. Results The search yielded 48 studies across 46 publications: 44 animal studies (26 ectopic and 18 orthotopic) and four clinical trials. Ectopic studies scored poorly on reporting quality and bias, while orthotopic studies were only moderately better. Twenty-seven of 27 experiments with chondrocyte-only controls demonstrated synergistic cartilage formation through co-implantation. Cartilage formation by co-implantations was also found in 15 of 17 experiments without such control and in four clinical trials. Conclusion Cartilage repair by articular chondrocytes is improved by adding a second cell type, like mesenchymal stromal cells. This is likely caused by the second cell types’ stimulatory support. Other second cell types and chondrocyte sources have shown promising results too. This is encouraging for further clinical exploration of single-stage co-implantation strategies.

Background: Autologous conditioned plasma (ACP) is a commercially available platelet concentrate with promising results from clinical trials. Purpose: To evaluate the clinical outcome after 3 consecutive injections of ACP in patients with knee osteoarthritis (OA) and study the influence of ACP composition and different patient factors as predictors of treatment effect. Study Design: Case series; Level of evidence, 4. Methods: This prospective case series included 260 patients (307 knees) who received ACP treatment for knee OA. The mean patient age was 51 ± 10 years. Improvement up to 12 months’ follow-up was measured using the Knee injury and Osteoarthritis Outcome Score (KOOS). ACP composition was analyzed in 100 patients. The predictive value of age, sex, history of knee trauma, Kellgren-Lawrence OA grade, body mass index, and ACP composition was evaluated using generalized estimating equations. Results: The mean overall KOOS improved from 38 ± 14 at baseline to 45 ± 18 at 3 months, 45 ± 18 at 6 months, and 43 ± 18 at 12 months (all P < .05); 40% of patients achieved an improvement above the minimal clinically important difference (MCID) of 8 after 6 months and 33% after 12 months. The variation in ACP composition did not correlate with KOOS ( P > .05). Older age led to a greater clinical benefit (β = 0.27; P = .05), whereas bilateral treatment predicted worse outcomes (β = –5.6; P < .05). Conclusion: The improvement in KOOS after treatment with ACP did not reach the MCID in most study patients. Older age was a predictor for better outcomes. The composition of ACP varied between patients but did not predict outcomes within the evaluated range. The study findings show the limited benefit of ACP treatment for knee OA and call for caution with routine use in clinical practice.

Meniscus injury and meniscectomy are strongly related to osteoarthritis, thus there is a clinical need for meniscus replacement. The purpose of this study is to create a meniscus scaffold with micro-scale circumferential and radial fibres suitable for a one-stage cell-based treatment. Poly-caprolactone-based scaffolds with three different architectures were made using melt electrowriting (MEW) technology and their in vitro performance was compared with scaffolds made using fused-deposition modelling (FDM) and with the clinically used Collagen Meniscus Implants® (CMI®). The scaffolds were seeded with meniscus and mesenchymal stromal cells (MSCs) in fibrin gel and cultured for 28 d. A basal level of proteoglycan production was demonstrated in MEW scaffolds, the CMI®, and fibrin gel control, yet within the FDM scaffolds less proteoglycan production was observed. Compressive properties were assessed under uniaxial confined compression after 1 and 28 d of culture. The MEW scaffolds showed a higher Young’s modulus when compared to the CMI® scaffolds and a higher yield point compared to FDM scaffolds. This study demonstrates the feasibility of creating a wedge-shaped meniscus scaffold with MEW using medical-grade materials and seeding the scaffold with a clinically-feasible cell number and -type for potential translation as a one-stage treatment.

Meniscus injuries can be highly debilitating and lead to knee osteoarthritis. Progenitor cells from the meniscus could be a superior cell type for meniscus repair and tissue-engineering. The purpose of this study is to characterize meniscus progenitor cells isolated by differential adhesion to fibronectin (FN-prog). Human osteoarthritic menisci were digested, and FN-prog were selected by differential adhesion to fibronectin. Multilineage differentiation, population doubling time, colony formation, and MSC surface markers were assessed in the FN-prog and the total meniscus population (Men). Colony formation was compared between outer and inner zone meniscus digest. Chondrogenic pellet cultures were performed for redifferentiation. FN-prog demonstrated multipotency. The outer zone FN-prog formed more colonies than the inner zone FN-prog. FN-prog displayed more colony formation and a higher proliferation rate than Men. FN-prog redifferentiated in pellet culture and mostly adhered to the MSC surface marker profile, except for HLA-DR receptor expression. This is the first study that demonstrates differential adhesion to fibronectin for the isolation of a progenitor-like population from the meniscus. The high proliferation rates and ability to form meniscus extracellular matrix upon redifferentiation, together with the broad availability of osteoarthritis meniscus tissue, make FN-prog a promising cell type for clinical translation in meniscus tissue-engineering.

Background: Anterior cruciate ligament (ACL) tear and meniscal injury often co-occur. The protective effect of early ACL reconstruction (ACLR) on meniscal injury and its repair is not clear. Critical literature review can support or change clinical strategies and identify gaps in the available evidence. Purpose: To assess the protective effect of ACLR on the meniscus and provide clinical guidelines for managing ACL tears and subsequent meniscal injury. We aimed to answer the following questions: (1) Does ACLR protect the meniscus from subsequent injury? (2) Does early ACLR reduce secondary meniscal injury compared with delayed ACLR? (3) Does ACLR protect the repaired meniscus? Study Design: Systematic review; Level of evidence, 4. Methods: A systematic review was performed through use of MEDLINE and Embase electronic databases according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Search terms included ACL, reconstruction, and meniscus. Studies describing primary ACLR and nonoperative treatment in adult patients were included, as well as studies indicating timing of ACLR. The included articles were assessed individually for risk of bias through use of the modified Cochrane Risk of Bias and MINORS (Methodological Index for Nonrandomized Studies) tools. Results: One level 2 randomized controlled trial and several level 3 and 4 studies indicated a protective effect of ACLR on meniscal injury compared with nonoperative treatment. There was weak (level 3) evidence of the protective effect of early ACLR on the meniscus. Meniscal repair failure was less frequent in patients with ACL reconstruction than in patients with ACL deficiency (level 4). Conclusion: The evidence collected in this review suggests a protective effect of ACLR for subsequent meniscal injury (level 2 evidence). ACLR should be performed within 3 months of injury (level 3 evidence). Meniscal injury requiring surgical repair in the ACL-deficient knee should be treated with repair accompanied by ACLR (level 3 evidence). The paucity of level 2 studies prevents the formation of guidelines based on level 1 evidence. There is a strong clinical need for randomized or prospective trials to provide guidelines on timing of ACLR and meniscal repair.