Requirement of direct contact between chondrocytes and macrophages for the maturation of regenerative cartilage

Single-cell RNA sequencing reveals the differentiation and regulation of endplate cells in human intervertebral disc degeneration

Low back pain (LBP) is largely attributed to intervertebral disc degeneration (IVDD), of which the endplate changes are an important component. However, the alterations in cell fate and properties within the endplates during degeneration remain unknown. Here, we firstly performed the single-cell RNA-sequencing analysis (scRNA-seq) of the cells focusing on degenerative human endplates. By unsupervised clustering of the 8,534 single-cell based on the gene expression, we identified nine distinct cell types. We employed Gene ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analysis, and the single-cell regulatory network inference and clustering (SCENIC) to determine the enriched pathways and transcriptional activities across seven chondrocyte subpopulations. Furthermore, two cell fates of chondrocyte differentiation were found by trajectory analysis, one was enriched in inflammation-related genes, and the other was related to extracellular matrix (ECM). Additionally, the intercellular interactions of macrophages (MA) and chondrocytes, T cells/natural killer cells (T/NK) and chondrocytes were examined by ligand-receptor pairs analysis, showing the important regulative function of FN1 from MA and CD74 from T/NK during endplate degeneration. Overall, our findings provide novel perspectives on the endplate degeneration at the single-cell level and a whole-transcriptome size.

High-Dose Neutrophil-Depleted Platelet-Rich Plasma Therapy for Knee Osteoarthritis: A Retrospective Study

Background/Objectives: Encouraging results have been reported for Platelet-Rich Plasma (PRP) treatment for knee osteoarthritis (KOA). This study reports the efficacy and safety of a high dose of neutrophile and red-blood-cell-depleted PRP to treat patients with KOA. Methods: A total of 212 consecutive patients diagnosed with Kellgren-Lawrence (KL) grading 1-3 KOA chronic knee pain for at least 1 year were treated with three injections at 15-day intervals with a high dose of neutrophil-depleted PRP (4 billion platelets). Clinical outcomes were retrospectively recorded as the percentage of responders at 3-, 6-, and 12-month follow-up, following the OMERACT-OARSI criteria. Pain, through the VAS score and WOMAC score, was also been recorded. Results: A total of 4 mL of PRP containing 4 × 109 platelets was obtained by single-spin centrifugation and injected intra-articularly into each patient with no preactivation. The overall responder rate of patients responding to the OMERACT-OARSI criteria at 3, 6, and 12 months was 68.9%, 72.7%, and 70.6%, respectively. A significant improvement in VAS and WOMAC scores at 3-, 6-, and 12-month follow-up compared to the pretreatment value (p < 0.01) was observed. The lowest VAS score was observed at 6 months overall and in all three KL-graded groups. The KL2 groups showed the best results regarding pain reduction and their WOMAC score at 6 months (p < 0.01). Conclusions: For KL1-3 KOA, a high dosage of neutrophil-depleted PRP is a successful treatment. It has long-lasting effects that last up to one year, relieves symptoms, and may slow the advancement of the disease.

Assessing the advantages of 3D bioprinting and 3D spheroids in deciphering the osteoarthritis healing mechanism using human chondrocytes and polarized macrophages

The molecular niche of an osteoarthritic microenvironment comprises the native chondrocytes, the circulatory immune cells, and their respective inflammatory mediators. Although M2 macrophages infiltrate the joint tissue during osteoarthritis (OA) to initiate cartilage repair, the mechanistic crosstalk that dwells underneath is still unknown. Our study established a co-culture system of human OA chondrocytes and M2 macrophages in 3D spheroids and 3D bioprinted silk-gelatin constructs. It is already well established that Silk fibroin-gelatin bioink supports chondrogenic differentiation due to upregulation of the Wnt/β-catenin pathway. Additionally, the presence of anti-inflammatory M2 macrophages significantly upregulated the expression of chondrogenic biomarkers (COL-II, ACAN) with an attenuated expression of the chondrocyte hypertrophy (COL-X), chondrocyte dedifferentiation (COL-I) and matrix catabolism (MMP-1 and MMP-13) genes even in the absence of the interleukins. Furthermore, the 3D bioprinted co-culture model displayed an upper hand in stimulating cartilage regeneration and OA inhibition than the spheroid model, underlining the role of silk fibroin-gelatin in encouraging chondrogenesis. Additionally, the 3D bioprinted silk-gelatin constructs further supported the maintenance of stable anti-inflammatory phenotype of M2 macrophage. Thus, the direct interaction between the primary OAC and M2 macrophages in the 3D context, along with the release of the soluble anti-inflammatory factors by the M2 cells, significantly contributed to a better understanding of the molecular mechanisms responsible for immune cell-mediated OA healing.