The German version of the KOOS-Child questionnaire (Knee injury and Osteoarthritis Outcome Score for children) shows a good to excellent internal consistency and a high test-retest reliability in children with knee problems.

PURPOSE: The Knee Injury Osteoarthritis Outcome Score for children (KOOS-Child) is a self-administered, valid and reliable questionnaire for children and adolescents with knee disorders such as Osgood Schlatter disease, anterior knee pain, and patella dislocation. This study aimed to cross-culturally adapt the German version of the KOOS-Child questionnaire and test the reliability in two groups of children, one treated conservatively and the other surgically. METHODS: A forward-backward translation of the original questionnaire into the German language was conducted. Children and adolescents between 10 and 18 years of age with knee disorders were included. Two groups were compared: sample one consisted of 24 participants with knee pain [20.8% boys; mean age = 13.4 (1.8) years treated conservatively. These participants completed the KOOS-Child questionnaire twice within two weeks to assess test-retest reliability. The second sample included 23 subjects (21.7% boys; mean age = 15.3 (1.9) years] treated surgically due to a knee disorder. They completed the questionnaire before surgery and six months postoperatively. Test-retest reliability and internal consistency were assessed using Spearman's rank correlation and Cronbach's alpha. RESULTS: All subscales showed a good to excellent internal consistency at both measurement points in both groups (conservatively treated group: a = 0.88-0.95; surgery group a = 0.80-0.91), with the exception of the subscale knee problems (conservatively treated: a = 0.60 and 0.52; surgery: α = 0.77 and 0.66). Test-retest reliability was between r = 0.85 and 0.94. CONCLUSION: The predominantly good to excellent internal consistency and the high test-retest reliability justifies the use of the German adaptation of the KOOS-Child questionnaire as a reliable multidimensional instrument for measuring health status and therapeutic effects in adolescents' knee disorders.

In Vitro and Ectopic In Vivo Studies toward the Utilization of Rapidly Isolated Human Nasal Chondrocytes for Single-Stage Arthroscopic Cartilage Regeneration Therapy.

Nasal chondrocytes (NCs) have a higher and more reproducible chondrogenic capacity than articular chondrocytes, and the engineered cartilage tissue they generate in vitro has been demonstrated to be safe in clinical applications. Here, we aimed at determining the feasibility for a single-stage application of NCs for cartilage regeneration under minimally invasive settings. In particular, we assessed whether NCs isolated using a short collagenase digestion protocol retain their potential to proliferate and chondro-differentiate within an injectable, swiftly cross-linked and matrix-metalloproteinase (MMP)-degradable polyethylene glycol (PEG) gel enriched with human platelet lysate (hPL). NC-hPL-PEG gels were additionally tested for their capacity to generate cartilage tissue in vivo and to integrate into cartilage/bone compartments of human osteochondral plugs upon ectopic subcutaneous implantation into nude mice. NCs isolated with a rapid protocol and embedded in PEG gels with hPL at low cell density were capable of efficiently proliferating and of generating tissue rich in glycosaminoglycans and collagen II. NC-hPL-PEG gels developed into hyaline-like cartilage tissues upon ectopic in vivo implantation and integrated with surrounding native cartilage and bone tissues. The delivery of NCs in PEG gels containing hPL is a feasible strategy for cartilage repair and now requires further validation in orthotopic in vivo models.

Nonoperative and Operative Soft-Tissue and Cartilage Regeneration and Orthopaedic Biologics of the Knee: An Orthoregeneration Network (ON) Foundation Review.

Orthoregeneration is defined as a solution for orthopedic conditions that harnesses the benefits of biology to improve healing, reduce pain, improve function, and optimally, provide an environment for tissue regeneration. Options include: drugs, surgical intervention, scaffolds, biologics as a product of cells, and physical and electro-magnetic stimuli. The goal of regenerative medicine is to enhance the healing of tissue after musculoskeletal injuries as both isolated treatment and adjunct to surgical management, using novel therapies to improve recovery and outcomes. Various orthopaedic biologics (orthobiologics) have been investigated for the treatment of pathology involving the knee, including symptomatic osteoarthritis and chondral injuries, as well as injuries to tendon, meniscus, and ligament, including the anterior cruciate ligament. Promising and established treatment modalities include hyaluronic acid (HA) in liquid or scaffold form; platelet-rich plasma (PRP); bone marrow aspirate (BMA) comprising mesenchymal stromal cells (MSCs), hematopoietic stem cells, endothelial progenitor cells, and growth factors; connective tissue progenitor cells (CTPs) including adipose-derived mesenchymal stem cells (AD-MSCs) and tendon-derived stem cells (TDSCs); matrix cell-based therapy including autologous chondrocytes or allograft; vitamin D; and fibrin clot. Future investigations should standardize solution preparations, because inconsistent results reported may be due to heterogeneity of HA, PRP, BMAC, or MSC preparations and regimens, which may inhibit meaningful comparison between studies to determine the true efficacy and safety for each treatment.

Does patella alta lead to worse clinical outcome in patients who undergo isolated medial patellofemoral ligament reconstruction? A systematic review.

INTRODUCTION: The aim of this systematic review is to determine the effect of patella height on clinical outcomes after isolated MPFL reconstruction for patella instability. Our primary hypothesis is that patients with patella alta report similar outcomes after isolated MPFL reconstruction compared to patients with normal patella height. METHODS: A review of the literature was performed according to the PRISMA guidelines. PubMed, EMBASE, and the Cochrane Library were searched from inception to January 10th 2018. Studies were identified using synonyms for "medial patellofemoral ligament", "reconstruction" and "patella alta". RESULTS: The search resulted in 467 reports on PubMed, 175 on EMBASE and 3 on the Cochrane Library. We included and analyzed in detail six studies describing outcomes after isolated medial patellofemoral ligament reconstruction with regard to patellar height. We found that both patients with patella alta and normal patella height reported satisfactory outcomes after isolated medial patellofemoral ligament reconstruction. However, because of applied exclusion criteria in the included studies the total number of patients with severe patella alta was small (13/74 patients with patella alta, 18%). CONCLUSIONS: Based on the current literature we suggest that additional tibial tubercle distalisation is not mandatory in patients with mild patella alta (Caton-Deschamps Index 1.2-1.4). To assess the best indications for different surgical procedures for patients with patella instability future research is needed to develop a clear and uniform definition of relevant patella alta. LEVEL OF EVIDENCE: III.

Nasal chondrocyte-based engineered autologous cartilage tissue for repair of articular cartilage defects: an observational first-in-human trial.

BACKGROUND: Articular cartilage injuries have poor repair capacity, leading to progressive joint damage, and cannot be restored predictably by either conventional treatments or advanced therapies based on implantation of articular chondrocytes. Compared with articular chondrocytes, chondrocytes derived from the nasal septum have superior and more reproducible capacity to generate hyaline-like cartilage tissues, with the plasticity to adapt to a joint environment. We aimed to assess whether engineered autologous nasal chondrocyte-based cartilage grafts allow safe and functional restoration of knee cartilage defects. METHODS: In a first-in-human trial, ten patients with symptomatic, post-traumatic, full-thickness cartilage lesions (2-6 cm2) on the femoral condyle or trochlea were treated at University Hospital Basel in Switzerland. Chondrocytes isolated from a 6 mm nasal septum biopsy specimen were expanded and cultured onto collagen membranes to engineer cartilage grafts (30 × 40 × 2 mm). The engineered tissues were implanted into the femoral defects via mini-arthrotomy and assessed up to 24 months after surgery. Primary outcomes were feasibility and safety of the procedure. Secondary outcomes included self-assessed clinical scores and MRI-based estimation of morphological and compositional quality of the repair tissue. This study is registered with ClinicalTrials.gov, number NCT01605201. The study is ongoing, with an approved extension to 25 patients. FINDINGS: For every patient, it was feasible to manufacture cartilaginous grafts with nasal chondrocytes embedded in an extracellular matrix rich in glycosaminoglycan and type II collagen. Engineered tissues were stable through handling with forceps and could be secured in the injured joints. No adverse reactions were recorded and self-assessed clinical scores for pain, knee function, and quality of life were improved significantly from before surgery to 24 months after surgery. Radiological assessments indicated variable degrees of defect filling and development of repair tissue approaching the composition of native cartilage. INTERPRETATION: Hyaline-like cartilage tissues, engineered from autologous nasal chondrocytes, can be used clinically for repair of articular cartilage defects in the knee. Future studies are warranted to assess efficacy in large controlled trials and to investigate an extension of indications to early degenerative states or to other joints. FUNDING: Deutsche Arthrose-Hilfe.

FGF2 induces RANKL gene expression as well as IL1ß regulated MHC class II in human bone marrow-derived mesenchymal progenitor stromal cells.

OBJECTIVE: Human bone marrow mesenchymal stromal cells (hBM-MSC) are being applied in tissue regeneration and treatment of autoimmune diseases (AD). Their cellular and immunophenotype depend on isolation and culture conditions which may influence their therapeutic application and reflect their in vivo biological functions. We have further characterised the phenotype induced by fibroblast growth factor 2 (FGF2) on healthy donor hBM-MSC focusing on the osteoimmunological markers osteoprotegerin (OPG), receptor activator of nuclear factor kB (RANK), RANK ligand (RANKL) and HLA-DR and their regulation of expression by the inflammatory cytokines IL1ß and IFNγ. METHODS: RANK, RANKL, OPG and HLA-DR expression in hBM-MSC expanded under specific culture conditions, were measured by RT-PCR and flow cytometry. MAPKs induction by FGF2, IL1ß and IFNγ in hBM-MSC was analysed by immunoblotting and RT-PCR. RESULTS: In hBM-MSC, OPG expression is constitutive and FGF2 independent. RANKL expression depends on FGF2 and ERK1/2 activation. IL1ß and IFNγ activate ERK1/2 but fail to induce RANKL. Only IL1ß induces P38MAPK. The previously described HLA-DR induced by FGF2 through ERK1/2 on hBM-MSC, is suppressed by IL1ß through inhibition of CIITA transcription. HLA-DR induced by IFNγ is not affected by IL1ß in hBM-MSC, but is suppressed in articular chondrocytes and lung fibroblasts. CONCLUSIONS: RANKL expression and IL1ß regulated MHC-class II, both induced via activation of the ERK1/2 signalling pathway, are specific for progenitor hBM-MSC expanded in the presence of FGF2. HLA-DR regulated by IL1ß and ERK1/2 is observed on hBM-MSC during early expansion without FGF2 suggesting previous in vivo acquisition. Stromal progenitor cells with this phenotype could have an osteoimmunological role during bone regeneration.

Bone microarchitecture of the talus changes with aging.

BACKGROUND: Fractures of the talus in the elderly are rare and usually result from high-impact injuries, suggesting only minor age-related bone structure changes. However, total ankle replacement failures with age often result from talar subsidence, suggesting age-related bone loss in the talus. Despite a number of histological analyses of talar microarchitecture, the effects of age and sex on talar microarchitecture changes remain poorly defined. QUESTIONS/PURPOSES: The aim of this study was to analyze changes or differences in the trabecular microarchitecture of the talus with regard to (1) age and (2) sex. METHODS: Sixty human tali were harvested from 30 patients at autopsy of three different age groups (20-40, 41-60, 61-80 years). The specimens were analyzed by radiography, micro-CT, and histological analysis. Given that there was no difference between the left and right talus, static histomorphometric parameters were assessed in three regions of interest of the right talus only (body, neck, head; n = 30). RESULTS: The talar body, neck, and head were affected differently by age-related changes. The greatest loss of bone volume with age was seen in the talar body (estimate: -0.239; 95% confidence interval [CI], -0.365 to -0.114; p < 0.001). In the talar neck (estimate: -0.165; 95% CI, -0.307 to -0.023; p = 0.025), bone loss was only moderate and primarily was the result of reduction in trabecular thickness (estimate: -1.288; 95% CI, -2.449 to -0.127; p = 0.031) instead of number (estimate: -0.001; 95% CI, -0.005 to -0.003; p = 0.593). Bone structure changes were independent of sex. CONCLUSIONS: Age-related bone structure changes predominantly occur in the talar body, which poses a potential risk factor for total ankle replacement loosening. The moderate changes in the talar neck might explain the persistent low incidence of talar neck fractures with age. CLINICAL RELEVANCE: Our findings suggest that before total ankle replacement implantation, careful patient selection with dual-energy xray absorptiometry evaluation may be necessary to reduce the risk of talar implant subsidence.

Enhanced chondrocyte proliferation and mesenchymal stromal cells chondrogenesis in coculture pellets mediate improved cartilage formation.

In this study, we aimed at investigating the interactions between primary chondrocytes and mesenchymal stem/stromal cells (MSC) accounting for improved chondrogenesis in coculture systems. Expanded MSC from human bone marrow (BM-MSC) or adipose tissue (AT-MSC) were cultured in pellets alone (monoculture) or with primary human chondrocytes from articular (AC) or nasal (NC) cartilage (coculture). In order to determine the reached cell number and phenotype, selected pellets were generated by combining: (i) human BM-MSC with bovine AC, (ii) BM-MSC from HLA-A2+ with AC from HLA-A2- donors, or (iii) human green fluorescent protein transduced BM-MSC with AC. Human BM-MSC and AC were also cultured separately in transwells. Resulting tissues and/or isolated cells were assessed immunohistologically, biochemically, cytofluorimetrically, and by RT-PCR. Coculture of NC or AC (25%) with BM-MSC or AT-MSC (75%) in pellets resulted in up to 1.6-fold higher glycosaminoglycan content than what would be expected based on the relative percentages of the different cell types. This effect was not observed in the transwell model. BM-MSC decreased in number (about fivefold) over time and, if cocultured with chondrocytes, increased type II collagen and decreased type X collagen expression. Instead, AC increased in number (4.2-fold) if cocultured with BM-MSC and maintained a differentiated phenotype. Chondro-induction in MSC-chondrocyte coculture is a robust process mediated by two concomitant effects: MSC-induced chondrocyte proliferation and chondrocyte-enhanced MSC chondrogenesis. The identified interactions between progenitor and mature cell populations may lead to the efficient use of freshly harvested chondrocytes for ex vivo cartilage engineering or in situ cartilage repair.

Interleukin-1ß modulates endochondral ossification by human adult bone marrow stromal cells.

Inflammatory cytokines present in the milieu of the fracture site are important modulators of bone healing. Here we investigated the effects of interleukin-1ß (IL-1ß) on the main events of endochondral bone formation by human bone marrow mesenchymal stromal cells (BM-MSC), namely cell proliferation, differentiation and maturation/remodelling of the resulting hypertrophic cartilage. Low doses of IL-1ß (50 pg/mL) enhanced colony-forming units-fibroblastic (CFU-f) and -osteoblastic (CFU-o) number (up to 1.5-fold) and size (1.2-fold) in the absence of further supplements and glycosaminoglycan accumulation (1.4-fold) upon BM-MSC chondrogenic induction. In osteogenically cultured BM-MSC, IL-1ß enhanced calcium deposition (62.2-fold) and BMP-2 mRNA expression by differential activation of NF-κB and ERK signalling. IL-1ß-treatment of BM-MSC generated cartilage resulted in higher production of MMP-13 (14.0-fold) in vitro, mirrored by an increased accumulation of the cryptic cleaved fragment of aggrecan, and more efficient cartilage remodelling/resorption after 5 weeks in vivo (i.e., more TRAP positive cells and bone marrow, less cartilaginous areas), resulting in the formation of mature bone and bone marrow after 12 weeks. In conclusion, IL-1ß finely modulates early and late events of the endochondral bone formation by BM-MSC. Controlling the inflammatory environment could enhance the success of therapeutic approaches for the treatment of fractures by resident MSC and as well as improve the engineering of implantable tissues.

The distal radius, the most frequent fracture localization in humans: a histomorphometric analysis of the microarchitecture of 60 human distal radii and its changes in aging.

BACKGROUND: The distal radius is the most frequent fracture localization in humans. Although younger patients receive a distal radius fracture after an adequate trauma, elderly patients suffer fractures through low-energy mechanisms. Low-energy fractures are hallmarks of osteoporosis. Osteoporotic changes of the distal radius are well described by DXA and peripheral quantitative computed tomography measurements. However, to date, the effects of aging on the microarchitecture of the distal radius have not been investigated. METHODS: To investigate whether the microarchitecture of the human distal radius shows osteoporotic changes in bone mass and structure during aging, we dissected out 60 complete human distal radii from 30 age- and gender-matched patients at autopsy. Each of the three different age groups (group I: 20-40 years, group II: 41-60 years, group III: 61-80 years) was represented by 10 autopsy cases and 20 specimens (double-sided extraction), respectively. The specimens were analyzed by peripheral quantitative computed tomography, contact-radiography, and histomorphometry. RESULTS: We observed a significant age-related decrease in bone mass, bone mineral density and an increase in typical osteoporotic changes of the bone microarchitecture in female distal radius specimens. Comparable observations of age-related changes have not been made in male specimens. CONCLUSIONS: The distal radius is a location of osteoporosis-specific bone changes. Our data provide evidence for the occurrence of typical osteoporotic changes, especially postmenopausal osteoporotic changes, in the distal radius during aging.

Nasal Chondrocyte-Based Engineered Grafts for the Repair of Articular Cartilage "Kissing" Lesions: A Pilot Large-Animal Study.

BACKGROUND: Bipolar or "kissing" cartilage lesions formed on 2 opposite articular surfaces of the knee joint are commonly listed as exclusion criteria for advanced cartilage therapies. PURPOSE: To test, in a pilot large-animal study, whether autologous nasal chondrocyte (NC)-based tissue engineering, recently introduced for the treatment of focal cartilage injuries, could provide a solution for challenging kissing lesions. STUDY DESIGN: Controlled laboratory study. METHODS: Osteochondral kissing lesions were freshly introduced into the knee joints of 26 sheep and covered with NC-based grafts with a low or high hyaline-like extracellular matrix; a control group was treated with a cell-free scaffold collagen membrane (SCA). The cartilage repair site was assessed at 6 weeks and 6 months after implantation by histology, immunohistochemistry, and magnetic resonance imaging evaluation. RESULTS: NC-based grafts, independently of their composition, induced partial hyaline cartilage repair with stable integrity in surrounding healthy tissue at 6 months after treatment. The SCA repaired cartilage to a similar degree to that of NC-based grafts. CONCLUSION: Kissing lesion repair, as evidenced in this sheep study, demonstrated the feasibility of the treatment of complex cartilage injuries with advanced biological methods. However, the potential advantages of an NC-based approach over a cell-free approach warrant further investigations in a more relevant preclinical model. CLINICAL RELEVANCE: NC-based grafts currently undergoing phase II clinical trials have a high potential to replace existing cartilage therapies that show significant limitations in the quality and reproducibility of the repair method. We have brought this innovative concept to the next level by addressing a new clinical indication.

Engineered nasal cartilage for the repair of osteoarthritic knee cartilage defects.

Osteoarthritis (OA) is the most prevalent joint disorder, causing pain and disability predominantly in the aging population but also affecting young individuals. Current treatments are limited to use of anti-inflammatory drugs to alleviate symptoms or degenerated joint replacement by a prosthetic implant at the end stage of the disease. We hypothesized that degenerative cartilage defects can be treated using nasal chondrocyte­based tissue-engineered cartilage (N-TEC). We demonstrate that N-TEC maintained cartilaginous properties when exposed in vitro to inflammatory stimuli found in osteoarthritic joints and favorably altered the inflammatory profile of cells from osteoarthritic joints. These effects were at least partially mediated by down-regulation of the WNT (wingless/integrated) signaling pathway through sFRP1 (secreted frizzled-related protein-1). We further report that N-TEC survive and engraft in vivo in ectopic mouse models reproducing a human osteochondral OA tissue environment, as well as in sheep articular cartilage defects that mimic degenerative settings. Last, we tested the safety of autologous N-TEC for the treatment of osteoarthritic cartilage defects in the knees of two patients with advanced OA (Kellgren and Lawrence grades 3 and 4) who were otherwise considered for unicondylar knee arthroplasty. No adverse reactions were recorded, and patients reported reduced pain as well as improved joint function and life quality 14 months after surgery. Together, our findings indicate that N-TEC can directly contribute to cartilage repair in osteoarthritic joints. A suitably powered clinical trial is now required to assess its efficacy in the treatment of patients with OA.

Microarchitecture of the radial head and its changes in aging.

Fractures of the radial head are common; however, it remains to be determined whether the radial head has to be considered as a typical location for fractures associated with osteoporosis. To investigate whether the human radial head shows structural changes during aging, we analyzed 30 left and 30 right human radial heads taken from 30 individuals. The specimens taken from the left side were analyzed by peripheral quantitative computed tomography (pQCT) and micro-CT. The specimens taken from the right elbow joint were analyzed by radiography and histomorphometry. In these specimens pQCT revealed a significant decrease of total and cortical bone mineral density (BMD(to) BMD(co)) with aging, regardless of sex. Histomorphometry revealed a significant reduction of cortical thickness (Ct.Th), bone volume per tissue volume (BV/TV), and trabecular thickness (Tb.Th) in male and female specimens. In this context, mean BV/TV and mean trabecular number (Tb.N) values were significantly lower and, accordingly, mean trabecular separation (Tb.Sp) was significantly higher in female samples. The presented study demonstrates that the radial head is a skeletal site where different age- and sex-related changes of the bone structure become manifest. These microarchitectural changes might contribute to the pathogenesis of radial head fractures, especially in aged female patients where trabecular parameters (BMD(tr) and Tb.Sp) change significantly for the worse compared to male patients.

Intra-individual comparison of human nasal chondrocytes and debrided knee chondrocytes: Relevance for engineering autologous cartilage grafts.

OBJECTIVE: Implantation of autologous chondrocytes for cartilage repair requires harvesting of undamaged cartilage, implying an additional joint arthroscopy surgery and further damage to the articular surface. As alternative possible cell sources, in this study we assessed the proliferation and chondrogenic capacity of debrided Knee Chondrocytes (dKC) and Nasal Chondrocytes (NC) collected from the same patients. METHODS: Matched NC and dKC pairs from 13 patients enrolled in two clinical studies (NCT01605201 and NCT026739059) were expanded in monolayer and then chondro-differentiated in 3D collagenous scaffolds in medium with or without Transforming Growth Factor beta 1 (TGFß1). Cell proliferation and amount of cartilage matrix production by these two cell types were assessed. RESULTS: dKC exhibited an inferior proliferation rate than NC, and a lower capacity to chondro-differentiate. Resulting dKC-grafts contained lower amounts of cartilage specific matrix components glycosaminoglycans and type II collagen. The cartilage forming capacity of dKC did not significantly correlate with specific clinical parameters and was only partially improved by medium supplemention with TGFß1. CONCLUSIONS: dKC exhibit a reproducibly poor capacity to engineer cartilage grafts. Our in vitro data suggest that NC would be a better suitable cell source for the generation of autologous cartilage grafts.

Seno-suppressive molecules as new therapeutic perspectives in rheumatic diseases.

Over the past years, through in vitro studies and unique animal models, biologists and clinicians have demonstrated that cellular senescence is at the root of numerous age-related chronic diseases including osteoarthritis and osteoporosis. This non-proliferative cellular syndrome can modify other surrounding tissue-resident cells through the establishment of a deleterious catabolic and inflammatory microenvironment. Targeting these deleterious cells through local or systemic seno-therapeutic agent delivery in pre-clinical models improves dramatically clinical signs and extends health span. In this review, we will summarize the current knowledge on cellular senescence, list the different strategies for identifying seno-suppressive therapeutic agents and their translations to rheumatic diseases.

Mesenchymal stem cell senescence alleviates their intrinsic and seno-suppressive paracrine properties contributing to osteoarthritis development.

Tissue accumulation of p16INK4a-positive senescent cells is associated with age-related disorders, such as osteoarthritis (OA). These cell-cycle arrested cells affect tissue function through a specific secretory phenotype. The links between OA onset and senescence remain poorly described. Using experimental OA protocol and transgenic Cdkn2a+/luc and Cdkn2aluc/luc mice, we found that the senescence-driving p16INK4a is a marker of the disease, expressed by the synovial tissue, but is also an actor: its somatic deletion partially protects against cartilage degeneration. We test whether by becoming senescent, the mesenchymal stromal/stem cells (MSCs), found in the synovial tissue and sub-chondral bone marrow, can contribute to OA development. We established an in vitro p16INK4a-positive senescence model on human MSCs. Upon senescence induction, their intrinsic stem cell properties are altered. When co-cultured with OA chondrocytes, senescent MSC show also a seno-suppressive properties impairment favoring tissue degeneration. To evaluate in vivo the effects of p16INK4a-senescent MSC on healthy cartilage, we rely on the SAMP8 mouse model of accelerated senescence that develops spontaneous OA. MSCs isolated from these mice expressed p16INK4a. Intra-articular injection in 2-month-old C57BL/6JRj male mice of SAMP8-derived MSCs was sufficient to induce articular cartilage breakdown. Our findings reveal that senescent p16INK4a-positive MSCs contribute to joint alteration.

Tissue engineering for paediatric patients.

The effects of oncological treatment, congenital anomalies, traumatic injuries and post-infection damage critically require sufficient amounts of tissue for structural and functional surgical reconstructions. The patient’s own body is typically the gold standard source of transplant material, but in children autologous tissue is available only in small quantities and with severe morbidity at donor sites. Engineering of tissue grafts starting from a small amount of autologous material, combined with suitable surgical manipulation of the recipient site, is expected to enhance child and adolescent health, and to offer functional restoration for long-term wellbeing. Moreover, engineered tissues based on patient-derived cells represent invaluable models to investigate mechanisms of disease and to develop/test novel therapeutic approaches. In view of these great opportunities, here we introduce the currently limited successful implementation of tissue engineering in paediatric settings and discuss the open challenges in the field. A particular focus is on the specific needs and envisioned strategies in the areas of bone and osteochondral regeneration in children.

Nasal chondrocytes as a neural crest-derived cell source for regenerative medicine.

Cells deriving from neural crest are generally acknowledged during embryonic development for their multipotency and plasticity, accounting for their capacity to generate various cell and tissue types even across germ layers. At least partial preservation of some of these properties in adulthood makes neural crest derived cells of large interest for regenerative purposes. Chondrocytes from fully mature nasal septum cartilage in adults are also derivatives of neural crest cells and were recently demonstrated to be able not only to maintain functionality across serial cloning, as surrogate self-renewal test, but also to respond and adapt to heterotopic transplantation sites. Based on these findings, cartilage grafts engineered by nasal chondrocytes were clinically used to reconstitute the nasal alar lobule and to repair articular cartilage defects. This article discusses further perspectives of potential clinical utility for nasal chondrocytes in musculoskeletal regeneration. It then highlights the need to derive deeper understanding of their biological properties in order to inform on possible therapeutic modes of action. This acquired knowledge will help to optimise manufacturing conditions to guarantee defined functional traits associated with safety and therapeutic potency of nasal chondrocytes in regenerative medicine.

Human chondroprogenitors in alginate-collagen hybrid scaffolds produce stable cartilage in vivo.

The goal of this study was to evaluate human epiphyseal chondroprogenitor cells (ECPs) as a potential new cell source for cartilage regeneration. ECPs were compared to human bone marrow stromal cells (MSCs) and human adult articular chondrocytes (ACs) for their chondrogenic potential and phenotypic stability in vitro and in vivo. The cells were seeded in Optimaix-3D scaffolds at 5 × 104 cells/mm3 and gene expression, matrix production and mechanical properties were analysed up to 6 weeks. In vitro, ECPs synthesized consistently high collagen 2 and low collagen 10. AC-seeded constructs exhibited high donor variability in GAG/DNA values as well as in collagen 2 staining, but showed low collagen 10 production. MSCs, on the other hand, expressed high levels of collagen 2 but also of collagens 1 and 10, and were therefore not considered further. In vivo, there was considerable loss of matrix proteins in ECPs compared to in vitro cultured samples. To overcome this, a second implantation study investigated the effect of mixing cells with alginate prior to seeding in the scaffold. ECPs in alginate maintained their cartilage matrix and resisted mineralization and vessel infiltration better 6 weeks after subcutaneous implantation, whereas ACs lost their chondrogenic matrix completely. This study shows the great potential of ECPs as an off-the-shelf, highly chondrogenic cell type that produces stable cartilage in vivo. Copyright © 2016 John Wiley & Sons, Ltd.

Bone microarchitecture of the calcaneus and its changes in aging: a histomorphometric analysis of 60 human specimens.

Bone structure and quality are an important parameter in the propensity of bone to fracture. Although the calcaneus is used as diagnostic reference site for osteoporosis by ultrasound, its structure has never been analyzed in detail. The purpose of this study was therefore to histomorphometrically analyze the trabecular microarchitecture of the calcaneus, and to determine whether the calcaneal bone structure is changing with age. Sixty complete human calcanei were harvested from thirty age- and gender-matched patients at autopsy. Each of the three different age groups (group I: 20 to 40, group II: 41 to 60, group III: 61 to 80 years of age) was represented by 20 specimens. The specimens were subjected to radiographic, microCT, and histologic analysis. Bone structure and bone mass of the calcaneus were quantified for three different regions of interest: the anterior ROI, the superior ROI (the subtalar region under the posterior facet), and the posterior ROI. An iliac crest biopsy was obtained from all patients to exclude any metabolic bone disease. Histomorphometric analysis revealed significant differences in bone volume within the calcaneus with highest values in the superior ROI: age group I: 31.3% (27.8-34.8%); II: 25.5% (22.1-28.9%); III: 18.9% (16.6-21.2%) and lowest bone volumes in the anterior ROI; age group I: 6.2% (4.8-7.6%); II: 3.6% (2.1-5.1%); III: 3.9% (2.9-4.9%). There was a significant age-related decrease in bone volume (BV/TV) in aging. Interestingly, this bone loss was most prominent in the superior ROI, with a 39% decrease in BV/TV between age group I and III (p < 0.001). Qualitative and structural analysis of trabecular number, thickness, and spacing demonstrated that the bone loss in the thalamic portion of the calcaneus was due to the transition of plate-like trabecular elements into a rod-like structure. In conclusion, our study demonstrated that the calcaneus displayed age-related changes in its microarchitecture that are known to reduce the biomechanical stability of trabecular bone, and that the age-related bone loss was most prominent in the region adjacent to the posterior facet (superior ROI). These results suggest that bone mass and structure are risk factors in respect to the occurrence and severity of calcaneal fractures, and indicate that calcaneal fractures are at least in part osteoporotic fractures.