Degenerative joint disease induced by repeated intra-articular injections of monosodium urate crystals in rats as investigated by translational imaging

The objective of this work was to assess the consequences of repeated intra-articular injection of monosodium urate (MSU) crystals with inflammasome priming by lipopolysaccharide (LPS) in order to simulate recurrent bouts of gout in rats. Translational imaging was applied to simultaneously detect and quantify injury in different areas of the knee joint. MSU/LPS induced joint swelling, synovial membrane thickening, fibrosis of the infrapatellar fat pad, tidemark breaching, and cartilage invasion by inflammatory cells. A higher sensitivity to mechanical stimulus was detected in paws of limbs receiving MSU/LPS compared to saline-injected limbs. In MSU/LPS-challenged joints, magnetic resonance imaging (MRI) revealed increased synovial fluid volume in the posterior region of the joint, alterations in the infrapatellar fat pad reflecting a progressive decrease of fat volume and fibrosis formation, and a significant increase in the relaxation time T2 in femoral cartilage, consistent with a reduction of proteoglycan content. MRI also showed cyst formation in the tibia, femur remodeling, and T2 reductions in extensor muscles consistent with fibrosis development. Repeated intra-articular MSU/LPS injections in the rat knee joint induced pathology in multiple tissues and may be a useful means to investigate the relationship between urate crystal deposition and the development of degenerative joint disease.

Arthroscopic Patellar Tendon Debridement and Distal Pole Osteoplasty for Recalcitrant Patellar Tendinopathy

Background: Chronic patellar tendinosis is an overuse injury of the patellar tendon that commonly afflicts jumping athletes. Indications: For patients with refractory symptoms that do not respond to extensive physical therapy and rest, surgical management may be considered. Although both open and arthroscopic treatments have been described, arthroscopic treatment allows for more direct access to the diseased dorsal portion of the tendon and allows for faster return to activities and sport. Technique Description: Arthroscopic treatment involves debridement of the diseased portion of the patella tendon and osteoplasty of the distal pole of the patella. The infrapatellar fat pad is first debrided using an arthroscopic shaver and radiofrequency ablation device to the level of the dorsal surface of the patellar tendon. Under direct arthroscopic visualization and corresponding to the location of edema noted on the magnetic resonance image, the diseased portion of the patellar tendon is gently debrided with an arthroscopic shaver. Next, an osteoplasty of the distal pole of the patella is performed to facilitate bleeding and healing of the diseased tendon as well as eliminate any mechanical impingement. Any calcifications within the enthesis can be removed using an arthroscopic biter and resector. An arthroscopic resector is then used to decorticate and smoothen the distal pole of the patella to the level of healthy, bleeding cancellous bone. Results: Significant improvements in pain and function have been reported with arthroscopic treatment for chronic patellar tendinosis. Patients can expect a 90% return to sport rate following the procedure, with return to preinjury function as soon as 3 to 5 months. This procedure is well tolerated with minimal complications reported. Discussion: Arthroscopic patellar tendon debridement and distal pole osteoplasty can be used to treat chronic patellar tendinosis refractory to nonoperative treatment. Improvements in pain and function have been reported with this technique, along with a faster return to sport compared with traditional open techniques.

LC-MS-Based Metabolomics Analysis Revealed Deleterious Effect of Infrapatellar Fat Pad on Articular Chondrocytes of Osteoarthritis

Objective: To investigate the interaction of infrapatellar fat pad/cartilage and related mechanisms in knee osteoarthritis (OA) using the metabolomics method.Method: Fat-conditioned media (FCM) of the infrapatellar fat pad from patients with OA were used to treat human OA chondrocytes. The extracellular metabolites of human OA chondrocytes were detected by nontargeted metabolic footprint analysis based on liquid chromatography and mass spectrometry (LC-MS). Then, the different metabolites were found, and the main metabolic pathways were explored, combined with bioinformatics methods.Results: After treatment with FCM for 48 h, the proliferation of human OA chondrocytes was slowed down, indicating that FCM had a certain inhibitory effect on the proliferation of human OA chondrocytes (P = 0.023). On the pattern diagram of principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA), after FCM treatment, the data sample areas were obviously separated, indicating that FCM can significantly affect the metabolic footprint of human OA chondrocytes. Through metabonomic identification, 131 different metabolites were screened after FCM treatment compared with before treatment. For 4 pathways in total, significantly different activity levels were discovered in pairwise comparisons: alanine, aspartate, and glutamate metabolism; citrate cycle (TCA cycle); arginine and proline metabolism; and phenylalanine metabolism.Conclusion: The infrapatellar fat pad aggravates OA chondrocyte injury and is involved in OA by disturbing the chondrocyte TCA cycle, amino acid metabolism, and glutamine metabolism, among others.

Factors Affecting the Aluminum, Arsenic, Cadmium and Lead Concentrations in the Knee Joint Structures

Background: Toxic elements, such as aluminum (Al), arsenic (As), cadmium (Cd), and lead (Pb), are persistent environmental pollutants that can cause adverse effects on the health of exposed individuals. Bone is one of the primary target organs of accumulation and potential damage from toxic elements.Objectives: This study was performed to determine the Al, As, Cd, and Pb concentrations in the femoral cancellous bone, femoral cartilage, anterior cruciate ligament, meniscus, tibial cartilage, tibial cancellous bone and infrapatellar fat pad. Furthermore, the aim of this study was to explore the relationships between toxic element concentrations and related factors such as gender, age, place of residence, hypertension and diabetes, and to determine the correlations among these toxic elements in knee joint structures.Methods: The samples used this study were collected from 51 patients following total knee arthroplasty. The Al, As, Cd, and Pb concentrations were determined using inductively coupled plasma optic emission spectrometry.Results: Significant differences were found in the Al, As, Cd, and Pb concentrations among the knee joint structures. Cd concentration in the tibial cancellous bone in women was significantly higher than in men. Pb concentration in the infrapatellar fat pad of urban patients was significantly higher as compared to rural patients. Al concentrations in the femoral cancellous bone, femoral cartilage, anterior cruciate ligament, meniscus and tibial cartilage were significantly higher in patients living in urban areas than in rural areas. As concentration in the tibial cancellous bone of diabetic patients was significantly higher compared to non-diabetic patients. In addition, significant Spearman's positive correlations were found between Al and Pb in the knee joint structures.Conclusion: The obtained results of the investigated toxic elements may serve as a basis for establishing the reference values of Al, As, Cd, and Pb in the knee joint structures. The results reported in the study provides novel data regarding the relationships between the toxic element concentrations and gender, age, place of residence, hypertension and diabetes in the studied structures of knee joint. Furthermore, new interactions among these toxic elements were noted.

Human Infrapatellar Fat Pad Mesenchymal Stem Cells Show Immunomodulatory Exosomal Signatures

Within the human knee infrapatellar fat pad (IFP) and synovium, resident synoviocytes and macrophages contribute to the onset and progression of inflammatory joint diseases. Our hypothesis is that IFP-derived mesenchymal stem cells (IFP-MSC) robust immunomodulatory therapeutic effects are largely exerted via their exosomal (IFP-MSC EXOs) secretome by attenuating synoviocyte and macrophage pro-inflammatory activation. IFP-MSC EXOs showed distinct miRNA and protein immunomodulatory profiles. Reactome analysis of 24 miRNAs highly present in exosomes showed their involvement in the regulation of six gene groups, including immune system. Exosomes were enriched for immunomodulatory and reparative proteins that are involved in positive regulation of cell proliferation, response to stimulus, signal transduction, signal receptor activity, and protein phosphorylation. Stimulated synoviocytes or macrophages exposed to IFP-MSC EXOs demonstrated significantly reduced proliferation, altered inflammation-related molecular profiles, and reduced secretion of pro-inflammatory molecules compared to stimulated alone. In an acute synovial/IFP inflammation rat model, IFP-MSC EXOs therapeutic treatment resulted in robust macrophage polarization towards an anti-inflammatory therapeutic M2 phenotype within the synovium/IFP tissues. Based on these findings, we propose a viable cell-free alternative to MSC-based therapeutics as an alternative approach to treating synovitis and IFP fibrosis.

Restoring Osteochondral Defects through the Differentiation Potential of Cartilage Stem/Progenitor Cells Cultivated on Porous Scaffolds

Cartilage stem/progenitor cells (CSPCs) are cartilage-specific, multipotent progenitor cells residing in articular cartilage. In this study, we investigated the characteristics and potential of human CSPCs combined with poly(lactic-co-glycolic acid) (PLGA) scaffolds to induce osteochondral regeneration in rabbit knees. We isolated CSPCs from human adult articular cartilage undergoing total knee replacement (TKR) surgery. We characterized CSPCs and compared them with infrapatellar fat pad-derived stem cells (IFPs) in a colony formation assay and by multilineage differentiation analysis in vitro. We further evaluated the osteochondral regeneration of the CSPC-loaded PLGA scaffold during osteochondral defect repair in rabbits. The characteristics of CSPCs were similar to those of mesenchymal stem cells (MSCs) and exhibited chondrogenic and osteogenic phenotypes without chemical induction. For in vivo analysis, CSPC-loaded PLGA scaffolds produced a hyaline-like cartilaginous tissue, which showed good integration with the host tissue and subchondral bone. Furthermore, CSPCs migrated in response to injury to promote subchondral bone regeneration. Overall, we demonstrated that CSPCs can promote osteochondral regeneration. A monophasic approach of using diseased CSPCs combined with a PLGA scaffold may be beneficial for repairing complex tissues, such as osteochondral tissue.

A 3D Bioprinted Human Meniscus Shape Enriched with Mesenchymal Cells

Background and objectives: Regenerative medicine, with its massive development over the years, has the potential to solve some of the most problematic medical issues, such as functional organ transplantation. The aim of this study was to create a human meniscal shape 3D-printed enriched with human adipose-derived mesenchymal cells. Materials and Methods: Human infrapatellar fat pad was harvested, and mesenchymal cells were isolated. The mesenchymal stem cells were differentiated to the chondrocite lineage and a hydrogel (a nanofibrillar cellulose, sodium alginate, D-mannitol, and Hepes buffer solution combination) cell mixture was bioprinted to create three human-size meniscus structures. The obtained structures were evaluated regarding the cell viability, appropriate size in relation to a native meniscus, and some mechanical characteristics. Results: The human meniscal shape created respected the anatomic characteristic of a native structure. Cell viability of approximately 97% and extracellular matrix formation after the printing process were observed. The mean maximum force for the meniscus with mesenchymal cells was 6.5 N (+/−0.5 N) compared to the mean maximum force for the native meniscus of 10.32 N (+/−0.7 N), which is statistically relevant (p < 0.01). Conclusion: This paper presents the potential of bioprinting viable cell structures that could in the future present enough mechanical strength to replace a human organ, such as a meniscus. There are still limitations regarding the ink and the printing process, but we are confident that these problems will soon be solvable.

Characterization and differentiation potential of mesenchymal stem cells isolated from multiple canine adipose tissue sources

Background Mesenchymal stem cells (MSCs) are undifferentiated cells that can give rise to a mesoderm lineage. Adipose-derived MSCs are an easy and accessible source for MSCs isolation, although each source of MSC has its own advantages and disadvantages. Our study identifies a promising source for the isolation and differentiation of canines MSCs. For this purpose, adipose tissue from inguinal subcutaneous (SC), perirenal (PR), omental (OM), and infrapatellar fat pad (IPFP) was isolated and processed for MSCs isolation. In the third passage, MSCs proliferation/metabolism, surface markers expression, in vitro differentiation potential and quantitative reverse transcription PCR (CD73, CD90, CD105, PPARγ, FabP4, FAS, SP7, Osteopontin, and Osteocalcin) were evaluated. Results Our results showed that MSCs derived from IPFP have a higher proliferation rate, while OM-derived MSCs have higher cell metabolism. In addition, MSCs from all adipose tissue sources showed positive expression of CD73 (NT5E), CD90 (THY1), CD105 (ENDOGLIN), and very low expression of CD45. The isolated canine MSCs were successfully differentiated into adipogenic and osteogenic lineages. The oil-red-O quantification and adipogenic gene expression (FAS, FabP4, and PPARγ) were higher in OM-derived cells, followed by IPFP-MSCs. Similarly, in osteogenic differentiation, alkaline phosphatase activity and osteogenic gene (SP7 and Osteocalcin) expression were higher in OM-derived MSCs, while osteopontin expression was higher in PR-derived MSCs. Conclusion In summary, among all four adipose tissue sources, OM-derived MSCs have better differentiation potential toward adipo- and osteogenic lineages, followed by IPFP-MSCs. Interestingly, among all adipose tissue sources, MSCs derived from IPFP have the maximum proliferation potential. The characterization and differentiation potential of canine MSCs isolated from four different adipose tissue sources are useful to assess their potential for application in regenerative medicine.