ObjectiveThis study aims to evaluate the applicability of the ultrasound roughnessindex (URI) for quantitative assessment of cartilage quality exvivo (post-mortem), after 6 months of in vivoarticulation with a Focal Knee Resurfacing Implant (FKRI).DesignGoats received a metal FKRI (n = 8) or sham surgery(n = 8) in the medial femoral condyles. After 6 monthsanimals were sacrificed, tibial plateaus were stained with Indian ink, andmacroscopic scoring of the plateaus was performed based on the ink staining.The URI was calculated from high-frequency ultrasound images at severalsections, covering both areas that articulated with the implant andnon-articulating areas. Cartilage quality at the most damaged mediallocation was evaluated with a Modified Mankin Score (MMS).ResultsThe URI was significantly higher in the FKRI-articulating than in the shamplateaus at medial articulating sections, but not at sections that were notin direct contact with the implant, for example, under the meniscus. Themean macroscopic score and MMS were significantly higher in theFKRI-articulating group than in the sham group (, , respectively). Correlation coefficients between URI andmacroscopic score were significant in medial areas that articulated with theimplant. A significant correlation between URI and MMS was found at the mostdamaged medial location ().ConclusionsThis study demonstrates the potential of URI to evaluate cartilage roughnessand altered surface morphology after in vivo articulationwith a metal FKRI, rendering it a promising future tool for quantitativefollow-up assessment of cartilage quality.

ObjectiveTo analyze and compare cartilage samples from 3 groups of patients utilizinglow-input RNA-sequencing.DesignCartilage biopsies were collected from patients in 3 groups(n = 48): Cartilage lesion (CL) patients had at leastICRS grade 2, osteoarthritis (OA) samples were taken from patientsundergoing knee replacement, and healthy cartilage (HC) was taken fromACL-reconstruction patients without CLs. RNA was isolated using an optimizedprotocol. RNA samples were assessed for quality and sequenced with alow-input SmartSeq2 protocol.ResultsRNA isolation yielded 48 samples with sufficient quality for sequencing.After quality control, 13 samples in the OA group, 9 in the HC group, and 9in the CL group were included in the analysis. There was a high degree ofco-clustering between the HC and CL groups with only 6 genes significantlyup- or downregulated. OA and the combined HC/CL group clusteredsignificantly separate from each other, yielding 659 significantlyupregulated and 1,369 downregulated genes. GO-term analysis revealed thatgenes matched to cartilage and connective tissue development terms.ConclusionThe gene expression profiles from the 3 groups suggest that there are nomajor differences in gene expression between cartilage from knees with acartilage injury and knees without an apparent cartilage injury. OAcartilage, as expected, showed markedly different gene expression from theother 2 groups. The gene expression profiles resulting from this low-inputRNA-sequencing study offer opportunities to discover new pathways notpreviously recognized that may be explored in future studies.

ObjectiveCartilage is avascular and numerous studies have identified the presence of single anti- and pro-angiogenic factors in cartilage. To better understand the maintenance hyaline cartilage, we assessed the angiogenic potential of complete cartilage releasate with functional assays in vitro and in vivo.DesignWe evaluated the gene expression profile of angiogenesis-related factors in healthy adult human articular cartilage with a transcriptome-wide analysis generated by next-generation RNAseq. The effect on angiogenesis of the releasate of cartilage tissue was assessed with a chick chorioallantoic membrane (CAM) assay as well as human umbilical vein endothelial cell (HUVEC) migration and proliferation assays using conditioned media generated from tissue-engineered cartilage derived from human articular and nasal septum chondrocytes as well as explants from bovine articular cartilage and human nasal septum. Experiments were done with triplicate samples of cartilage from 3 different donors.ResultsRNAseq data of 3 healthy human articular cartilage donors revealed that the majority of known angiogenesis-related factors expressed in healthy adult articular cartilage are pro-angiogenic. The releasate from generated cartilage as well as from tissue explants, demonstrated at least a 3.1-fold increase in HUVEC proliferation and migration indicating a pro-angiogenic effect of cartilage. Finally, the CAM assay demonstrated that cartilage explants can indeed attract vessels; however, their ingrowth was not observed.ConclusionUsing multiple approaches, we show that cartilage releasate has an inherent pro-angiogenic capacity. It remains vessel free due to anti-invasive properties associated with the tissue itself.