Mature Cartilage Research Articles

Influence of Periosteum Location on the Bone and Cartilage in Tissue-Engineered Phalanx

This study investigated the influence of periosteal tissue of different origins on the calcification at the diaphysis and chondrocyte maturation at the epiphysis in an engineered phalanx. We hypothesized that the periosteum from long bones would better provide donor cells for bone formation and signals for maturation of the joint cartilage. Periosteum was harvested from 4 locations (cranium, mandible, radius, and ilium) of calf bones. A human phalangeal bone-shaped, biodegradable, 3-dimensional scaffold hydroxyapatite-poly L-lactic-ɛ-caprolactone (HA-P[LA/CL]) was prepared using a human phalangeal bone-shaped template. A bioengineered human phalanx was fabricated by combining periosteal grafts with biodegradable copolymers. The joint cartilage region (chondrocyte/polyglycolic acid [PGA] composite) was subsequently sutured to the phalangeal bone region (periosteum/HA-P[LA/CL] composite) with absorbable sutures to make a human phalangeal bone model. These were then implanted in nude mice for maturation of the constructs. Macroscopic, radiographic, histological, and immune-histochemical evaluations were carried out to determine the relative influence of the periosteal graft source on bone and cartilage formation at 10 and 20 weeks after implantation. Calcification localized under the periosteum was noted in the cranium, radius, and ilium groups after 10 weeks, which markedly expanded at the modelled diaphysis after 20 weeks. The width in the minor axis direction tended to increase with time after grafting in the cranium group, whereas the longitudinal length increased in the radius and ilium groups. The joint cartilage thickness changed with time depending on the type of periosteum, and periosteum collected from the radius and ilium was associated with the greatest cartilage thickness in the joint cartilage maturation process. These results suggest that periosteum collected from radius of calves demonstrated superior bone formation and chondrocyte maturation in the engineered phalanx compared with other sources of periosteum. The osteogenic capacity depends on the periosteal source regardless of intramembranous or endochondral ossification. The appropriate periosteal choice is essential in the phalangeal bone and cartilage tissue engineering. The results are important for broadening tissue engineering possibilities for clinical application.

Stable Tracheal Regeneration Using Organotypically Cultured Tissue Composed of Autologous Chondrocytes and Epithelial Cells in Beagles.

In tracheal regeneration, the slow process of epithelialization is often a barrier to the stability and safety of the transplanted trachea. The aim of this study was to examine a new tracheal regeneration technique using organotypically cultured tissue composed of autologous cells. Nine beagles were prepared. Chondrocytes from auricular cartilage and epithelial cells from buccal mucosa were isolated and cultured. Tissue-engineered cartilages were fabricated with chondrocytes at a density of 1 × 107 cells/mL (high-density group) and 1 × 106 cells/mL (low-density group). A fabricated epithelial cell sheet was laid on a poly(lactic-co-glycolic acid) block in atelocollagen gel containing the chondrocytes, and the organotypically cultured tissues were transplanted into a partially resected trachea. The control group had only the block transplanted. The tissue-engineered cartilages in the high-density group contained many viable chondrocytes and many cartilage matrices. The low-density group had abundant collagen fibers and no chondrocytes. Tracheal endoscopy revealed no deformation or atrophy at the transplant site in the high-density group. Histologically, partially hyaline cartilages covered with epithelium and lamina propria were found in the high-density group but not in the low-density and control groups. Stable tracheal regeneration was achieved using organotypically cultured tissue fabricated with autologous high-density chondrocytes and epithelial cells.

CD271-selected mesenchymal stem cells from adipose tissue enhance cartilage repair and are less angiogenic than plastic adherent mesenchymal stem cells

CD271 is a marker of bone marrow MSCs with enhanced differentiation capacity for bone or cartilage repair. However, the nature of CD271+ MSCs from adipose tissue (AT) is less well understood. Here, we investigated the differentiation, wound healing and angiogenic capacity of plastic adherent MSCs (PA MSCs) versus CD271+ MSCs from AT. There was no difference in the extent to which PA MSCs and CD271+ MSCs formed osteoblasts, adipocytes or chondrocytes in vitro. In contrast, CD271+ MSCs transplanted into athymic rats significantly enhanced osteochondral wound healing with reduced vascularisation in the repair tissue compared to PA MSCs and control animals; there was little histological evidence of mature articular cartilage formation in all animals. Conditioned medium from CD271+ MSC cultures was less angiogenic than PA MSC conditioned medium, and had little effect on endothelial cell migration or endothelial tubule formation in vitro. The low angiogenic activity of CD271+ MSCs and improved early stage tissue repair of osteochondral lesions when transplanted, along with a comparable differentiation capacity along mesenchymal lineages when induced, suggests that these selected cells are a better candidate than PA MSCs for the repair of cartilaginous tissue.

Chondroid Tumors as Incidental Findings and Differential Diagnosis between Enchondromas and Low-grade Chondrosarcomas.

Chondroid tumors are a heterogeneous group of neoplasms that all share the production of chondroid matrix. This ranges from a fetal type to mature hyaline cartilage and mirrors its imaging characteristics.The benign chondroid tumors represent some of the most encountered incidental bone lesions, with osteochondroma the most frequent benign bone tumor. Enchondroma is mostly asymptomatic, and yet it is probably the second most common primary bone tumor. Similarly, its malignant counterpart, chondrosarcoma, is the second most common malignant primary bone tumor.The 2013 World Health Organization (WHO) updated this group of tumors, and grade 1 chondrosarcoma was renamed "atypical cartilage tumor" and classified as an intermediate type of tumor, not a malignancy, which better describes its clinical behavior.In this article we summarize changes made in the updated 2013 WHO classification and highlight the diagnostic features differentiating an enchondroma from a low-grade chondrosarcoma. We also describe practical imaging aspects of the remaining chondroid tumors.

Implant-type tissue-engineered cartilage derived from human auricular chondrocyte may maintain cartilaginous property even under osteoinductive condition.

Introduction: There is a growing need for chondrocyte implantation for reconstructing cartilage defect. However, ossification of the implanted cartilage is a challenging problem. Implant-type tissue-engineered cartilage from human auricular chondrocytes is a three-dimensional implant type cartilage using PLLA as a scaffold for chondrocytes. Although there is a study which evaluated the ossification of this cartilage in subcutaneous area, there is no study which clarify the possibility of ossification in osteoinductive surroundings. The purpose of this study was to elucidate the possibility of the ossification of implant-type tissue-engineered cartilage using human auricular chondrocyte in an osteoinductive environment. Methods: Human chondrocytes were harvested from ear cartilage. After dispersion by enzyme digestion, they were put into either a poly-L-lactic acid (PLLA) or poly lactic-co-glycolic acid (PLGA) scaffold, with collagen gel. Implant-type tissue-engineered cartilage was interposed between pieces of human iliac bone harvested from the same donor and implanted subcutaneously in nude rats. Scaffold without chondrocytes was used as a control. After 1, 3, and 6 months, ossification and cartilage formation were evaluated by X-ray, hematoxylin-eosin (HE) stain and toluidine blue (TB) stain. Results: There was no ossification of implant-type cartilage using human chondrocytes, even under osteoinductive conditions. HE staining showed that perichondrium formed around the constructs and chondrocytes were observed 6months after the implantation. TB staining showed metachromasia in every sample, with the area of metachromasia increasing over time, suggesting maturation of the cartilage. Conclusions: In conclusion, adjacent iliac bone had no apparent effect on the maturation of cartilage in implant-type tissue-engineered cartilage. Cartilage retention and maturation even in the presence of iliac bone could have been due to a scarcity of mesenchymal stem cells in the bone and surrounding area.

Osteocartilaginous choristoma of tonsil: A report of two cases

Osteocartilaginous choristoma of the tonsil is a rare entity with very few cases reported in the literature. We report two cases presenting with tonsillar enlargement. Histopathological examination revealed the presence of mature cartilage and bone within the tonsillar tissue.

Sequential Zonal Chondrogenic Differentiation of Mesenchymal Stem Cells in Cartilage Matrices.

The higher regenerative capacity of fetal articular cartilage compared with the adult is rooted in differences in cell density and matrix composition. We hypothesized that the zonal organization of articular cartilage can be engineered by encapsulation of mesenchymal stem cells in a single superficial zone-like matrix followed by sequential addition of zone-specific growth factors within the matrix, similar to the process of fetal cartilage development. The results demonstrate that the zonal organization of articular cartilage can potentially be regenerated using an injectable, monolayer cell-laden hydrogel with sequential release of growth factors.

Coexistence of giant cell tumor of tendon sheath and enchondroma in the middle phalanx of the little finger mimicking a malignant tumor: A case report.

Giant cell tumor of the tendon sheath is a type of slow-growing benign soft tissue tumor that typically arises from the synovium of the tendon sheath. Enchondroma is a benign bone tumor comprising of mature hyaline cartilage that centrally develops within the tubular bone. While giant cell tumor of the tendon sheath or enchondroma are common benign soft tissue and bone tumors, respectively the simultaneous occurrence of these tumors in the same region of the hand is exceedingly rare, and it can mimic a malignant tumor, thereby making the diagnosis more challenging. Herein, we report an unusual imaging presentation of the coexistence of these tumors in the middle phalanx of the little finger, which to the best of our knowledge has not been previously reported, and this initially present as a single intrinsic osseous lesion mimicking malignancy. The coexistence of these tumor types must be considered in the differential diagnosis of an intramedullary lytic lesion with a poor margin associated with a soft tissue mass of the fingers, and a meticulous preoperative magnetic resonance imaging investigation was required.

Clinically Meaningful Improvement After Treatment of Cartilage Defects of the Knee With Osteochondral Grafts

Background: Mosaicplasty and fresh osteochondral allograft transplantation (OCA) are popular cartilage restoration techniques that involve the single-stage implantation of viable, mature hyaline cartilage–bone dowels into chondral lesions of the knee. Recently, there has been greater focus on what represents a clinically relevant change in outcomes reporting, and commonly applied metrics for measuring clinical significance include the minimal clinically important difference (MCID) and substantial clinical benefit (SCB). Purpose: To define the MCID and SCB after mosaicplasty or OCA for the International Knee Documentation Committee (IKDC) subjective form and Knee Outcome Survey–Activities of Daily Living (KOS-ADL) and to determine patient factors that are predictive of achieving the MCID and SCB after mosaicplasty or OCA. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: An institutional cartilage registry was reviewed to identify patients who underwent mosaicplasty or OCA. The decision to perform either mosaicplasty or OCA was generally based on chondral defect size. The IKDC and KOS-ADL were administered preoperatively and at a minimum of 2 years postoperatively. Patient responses to the outcome measures were aggregated, and the MCID and SCB of these outcome scores were calculated with anchor-based methods. Multivariate analysis adjusted for age and sex was performed to identify patient factors predictive of achieving the MCID and SCB. Results: Of the 372 eligible patients, 151 (41%) were lost to follow-up, 46 (12%) had incomplete preoperative outcome scores and 2 were treated with OCA of the tibia and therefore excluded. In total, 173 knees were analyzed (n = 173 patients; mean age, 33.0 years; 37% female). Seventy-five (43%) and 98 (57%) knees were treated with mosaicplasty and OCA, respectively. The mean ± SD MCIDs for the IKDC and KOS-ADL were 17 ± 3.9 and 10 ± 3.7, respectively. The SCBs for the IKDC and KOS-ADL were 30 ± 6.9 and 17 ± 3.9, respectively. Univariate analysis demonstrated no association between procedure (mosaicplasty or OCA) and likelihood of achieving the MCID or SCB. In the multivariate analysis, lower preoperative IKDC and KOS-ADL scores, higher preoperative Marx Activity Rating Scale scores, lower preoperative 36-Item Short Form Health Survey pain scores, and a history of ≤1 prior ipsilateral knee surgical procedure were predictive of achieving the MCID and/or SCB. Conclusion: These values can be used to define a clinically meaningful improvement for future outcome studies. For surgeons considering mosaicplasty or OCA for their patients, these results can help guide clinical decision making and manage patient expectations before surgery.

Possible reparative effect of low-intensity pulsed ultrasound (LIPUS) on injured meniscus.

Menisci are a pair of crescent-shaped fibrocartilages, particularly of which their inner region of meniscus is an avascular tissue. It has characteristics similar to those of articular cartilage, and hence is inferior in healing. We previously reported that low-intensity pulsed ultrasound (LIPUS) treatment stimulates the production of CCN2/CTGF, a protein involved in repairing articular cartilage, and the gene expression of major cartilage matrices such as type II collagen and aggrecan in cultured chondrocytes. Therefore, in this present study, we investigated whether LIPUS has also favorable effect on meniscus cells and tissues. LIPUS applied with a 60mW/cm2 intensity for 20min stimulated the gene expression and protein production of CCN2 via ERK and p38 signaling pathways, as well as gene expression of SOX9, aggrecan, and collagen type II in human inner meniscus cells in culture, and slightly stimulated the gene expression of CCN2 and promoted the migration in human outer meniscus cells in culture. LIPUS also induced the expression of Ccn2, Sox9, Col2a1, and Vegf in rat intact meniscus. Furthermore, histological evaluations showed that LIPUS treatment for 1 to 4weeks promoted healing of rat injured lateral meniscus, as evidenced by better and earlier angiogenesis and extracellular matrix synthesis. The data presented indicate that LIPUS treatment might prevent meniscus from degenerative change and exert a reparative effect on injured meniscus via up-regulation of repairing factors such as CCN2 and that it might thus be useful for treatment of an injured meniscus as a non-invasive therapy.

Dickkopf-1 reduces hypertrophic changes in human chondrocytes derived from bone marrow stem cells

The in vitro process of chondrogenic differentiation of mesenchymal stem cells (MSCs) induces a pre-apoptotic hypertrophic phenotype, guided by the active status of the WNT/β‑catenin pathway. To achieve a stable chondrocyte phenotype for cartilage tissue engineering, it is necessary to gain a better understanding of specific genes that regulate the cartilage tissue phenotype. RNA sequencing (RNA-seq) analysis of tissue samples from bone, cartilage, growth plate and muscle show that Dickkopf-1 (DKK1), a natural WNT canonical signaling inhibitor, is expressed in cartilage tissue. This observation reinforces the concept that inhibition of the WNT/β‑catenin pathway is critical for preventing avoid chondrocyte hypertrophy in vitro. We used two doses of DKK1 in a pellet cell culture system to inhibit the terminal differentiation of chondrocytes derived from bone marrow mesenchymal stem cells (MSCs). Bone marrow MSCs were cultured in chondrogenic induction medium with 50 and 200 ng/ml of DKK1 for 21 days. The highest doses of DKK1 reduce β‑catenin expression and nuclear localization at day 21, concomitant with reduced expression and activity of hypertrophy markers collagen type X (COL10A1) and alkaline phosphatase (ALPL), thus decreasing the pre-hypertrophic chondrocyte population. Furthermore, DKK1 stimulated expression of collagen type II (COL2A1) and glycosaminoglycans (GAGs), which represent healthy articular cartilage markers. We conclude that exogenous DKK1 impedes chondrocyte progression into a prehypertrophic stage and stimulates expression of healthy articular cartilage markers by blocking the WNT/β‑catenin pathway. Hence, DKK1 may promote a mature healthy articular cartilage phenotype and facilitate cartilage tissue engineering for joint repair.

Solitary Lung Nodule

A man with thyroid cancer had a lesion identified in the left lower lobe of the lung on computed tomography. The gross photograph of the bisected wedge resection specimen shows a relatively well-circumscribed glistening mass (arrow) in the lung parenchyma.What is the best diagnosis for the lesion?a.Pulmonary adenocarcinomab.Pulmonary hamartomac.Metastasis to the lungd.Granuloma arising in the lung Answer: b. Pulmonary hamartoma. Pulmonary hamartoma is often incidentally discovered radiographically as a single well-circumscribed nodule with smooth margins and occasional calcifications, the so-called popcorn appearance (arrow, image A).1Gjevre J.A. Myers J.L. Prakash U.B.S. Pulmonary hamartomas.Mayo Clin Proc. 1996; 71: 14-20Abstract Full Text Full Text PDF PubMed Scopus (177) Google Scholar, 2Ost D.E. Gould M.K. Decision making in patients with pulmonary nodules.Am J Respir Crit Care Med. 2012; 185: 363-372Crossref PubMed Scopus (176) Google Scholar On histopathologic examination, mature cartilage is identified in fibromyxoid stroma with interwoven adipose tissue (image B, arrow marks adipose). Various tissues have been identified in pulmonary hamartomas, including smooth muscle, fat, and bone.1Gjevre J.A. Myers J.L. Prakash U.B.S. Pulmonary hamartomas.Mayo Clin Proc. 1996; 71: 14-20Abstract Full Text Full Text PDF PubMed Scopus (177) Google Scholar, 2Ost D.E. Gould M.K. Decision making in patients with pulmonary nodules.Am J Respir Crit Care Med. 2012; 185: 363-372Crossref PubMed Scopus (176) Google Scholar

Age, but not short-term intensive swimming, affects chondrocyte turnover in zebrafish vertebral cartilage.

Both age and intensive exercise are generally considered critical risk factors for osteoarthritis. In this work, we intend to establish zebrafish models to assess the role of these two factors on cartilage homeostasis. We designed a swimming device for zebrafish intensive exercise. The body measurements, bone mineral density (BMD) and the histology of spinal cartilages of 4- and 12-month-old zebrafish, as well the 12-month-old zebrafish before and after a 2-week exercise were compared. Our results indicate that both age and exercise affect the body length and body weight, and the micro-computed tomography reveals that both age and exercise affect the spinal BMD. However, quantitative analysis of immunohistochemistry and histochemistry indicate that short-term intensive exercise does not affect the extracellular matrix (ECM) of spinal cartilage. On the other hand, the cartilage ECM significantly grew from 4 to 12 months of age with an increase in total chondrocytes. dUTP nick end labeling staining shows that the percentages of apoptotic cells significantly increase as the zebrafish grows, whereas the BrdU labeling shows that proliferative cells dramatically decrease from 4 to 12 months of age. A 30-day chase of BrdU labeling shows some retention of labeling in cells in 4-month-old spinal cartilage but not in cartilage from 12-month-old zebrafish. Taken together, our results suggest that zebrafish chondrocytes are actively turned over, and indicate that aging is a critical factor that alters cartilage homeostasis. Zebrafish vertebral cartilage may serve as a good model to study the maturation and homeostasis of articular cartilage.

Lyophilized Scaffolds Fabricated from 3D-Printed Photocurable Natural Hydrogel for Cartilage Regeneration.

Repair of cartilage defects is highly challenging in clinical treatment. Tissue engineering provides a promising approach for cartilage regeneration and repair. As a core component of tissue engineering, scaffolds have a crucial influence on cartilage regeneration, especially in immunocompetent large animal and human. Native polymers, such as gelatin and hyaluronic acid, have known as ideal biomimetic scaffold sources for cartilage regeneration. However, how to precisely control their structure, degradation rate, and mechanical properties suitable for cartilage regeneration remains a great challenge. To address these issues, a series of strategies were introduced in the current study to optimize the scaffold fabrication. First, gelatin and hyaluronic acid were prepared into a hydrogel and 3D printing was adopted to ensure precise control in both the outer 3D shape and internal pore structure. Second, methacrylic anhydride and a photoinitiator were introduced into the hydrogel system to make the material photocurable during 3D printing. Finally, lyophilization was used to further enhance mechanical properties and prolong degradation time. According to the current results, by integrating photocuring 3D printing and lyophilization techniques, gelatin and hyaluronic acid were successfully fabricated into human ear- and nose-shaped scaffolds, and both scaffolds achieved shape similarity levels over 90% compared with the original digital models. The scaffolds with 50% infill density achieved proper internal pore structure suitable for cell distribution, adhesion, and proliferation. Besides, lyophilization further enhanced mechanical strength of the 3D-printed hydrogel and slowed its degradation rate matching to cartilage regeneration. Most importantly, the scaffolds combined with chondrocytes successfully regenerated mature cartilage with typical lacunae structure and cartilage-specific extracellular matrixes both in vitro and in the autologous goat model. The current study established novel scaffold-fabricated strategies for native polymers and provided a novel natural 3D scaffold with satisfactory outer shape, pore structure, mechanical strength, degradation rate, and weak immunogenicity for cartilage regeneration.

Regeneration of Trachea Graft with Cartilage Support, Vascularization, and Epithelization

The repair and functional reconstruction of long-segment tracheal defects is always a great challenge in the clinic. Finding an ideal substitute for tracheal transplantation is the only way to solve this problem. To address these problems, the current study proposed a series of novel strategies. For large-volume cartilage regeneration, a cartilage sheet technique (without any extra materials) was adopted to avoid the inflammatory reaction triggered by the materials and form homogeneous, mature cartilage in autologous goat model. For vascularization, the flat trapezius fascia flap with double blood supply was separated by microsurgical techniques to achieve stable pre-vascularization of the regenerated cartilage and grafted epithelium simultaneously. Finally, transplantation of the oral mucosal epithelium was used to realize epithelialization. By integrating the above strategies, a vascularized and epithelialized tracheal tissue with tubular cartilage support was successfully constructed in a goat model, which provides an ideal tracheal substitute for the repair and permanent functional reconstruction of long-segment tracheal defects. Funding: This research was supported by The National Key Research and Development Program of China (2017YFC1103900), The Key Research and Development Program of Shandong (2016GGB14002), National Natural Science Foundation of China (31400830, 31700837 and 81571823), Shanghai Science and Technology Committee (16QB1400600), and Program for Shanghai Outstanding Medical Academic Leader, Graduate Student Innovation Fund of Shanghai Jiao Tong University School of Medicine (BXJ201831, to Zongqi Yin.), and PUMC Youth Fund and the Fundamental Research Funds for the Central Universities (3332014047). Declaration of Interest: We declare that we have no conflicts of interest. Ethical Approval: Animal experiments were approved by the Shanghai Jiao Tong University Committee on Animal Care and were conducted by the Key Laboratory of Tissue Engineering at Shanghai Ninth People’s Hospital, affiliated with Shanghai Jiao Tong University in China. All experiments involving animals were performed in accordance with the approved guidelines.

Cartilage regeneration using a novel autologous growth factors-based matrix for full-thickness defects in sheep.

To investigate the chondrogenic-regenerative properties of a novel autologous-made matrix composed of hyaline cartilage chips combined with a growth factors-based clot for full-thickness defects in sheep. A full-thickness, 8-mm diameter cartilage defect was created in the weight-bearing area of the medial femoral condyle in 6 sheep. Treatment consisted of surgical implantation of an autologous-based matrix of hyaline cartilage chips combined with a clot of plasma poor in platelets and intraarticular injection of plasma rich in growth factors. Outcome measures at 1, 3 and 6months included macroscopic International Cartilage Repair Society (ICRS) score, histological and immunohistochemical analysis for collagen expression, and transmission electron microscopy study. The 6-month macroscopic evaluation showed nearly normal (11.1 ± 0.7) cartilage repair assessment. The ICRS score was significantly higher at 6months compared to 3months (5.5 ± 1.3; p < 0.0001) and 1 (1.1 ± 0.4; p < 0.0001) month. At 6months, hyaline cartilage tissue filling the defect was observed with adequate integration of the regenerated cartilage at the surrounding healthy cartilage margin. At 6months, mature chondrons and cartilage matrix contained collagen fibers with masked fibrillary structure, and the expression of collagen in the newly formed cartilage was similar in intensity and distribution pattern compared to the healthy adjacent cartilage. This novel treatment enhanced chondrogenesis and regenerated hyaline cartilage at 6 months with nearly normal macroscopic ICRS assessment. Histological analysis showed equivalent structure to mature cartilage tissue in the defect and a collagen expression pattern in the newly formed cartilage similar to that found in adjacent healthy articular cartilage. The present technique may have clinical application for chondral injuries in humans because this procedure is cheap (no need for allograft, or expensive instrumentation/biomaterials/techniques), easy and fast-performing through a small arthrotomy, and safe (no rejection possibility because the patients' own tissue, cells, and plasma are used).

Sprifermin treatment enhances cartilage integration in an in vitro repair model.

Cartilage integration remains a clinical challenge for treatment of focal articular defects. Cartilage exhibits limited healing capacity that declines with tissue maturation. Many approaches have been investigated for their ability to stimulate healing of mature cartilage or integration of repair tissue or tissue-engineered constructs with native cartilage. Growth factors present in immature tissue may enhance chondrogenesis and promote integrative repair of cartilage defects. In this study, we assessed the role of one such factor, fibroblast growth factor 18 (FGF18). Studies using FGF18 have shown a variety of positive effects on cartilage, including stimulation of chondrocyte proliferation, matrix biosynthesis, and suppression of proteinase activity. To explore the role of FGF18 on cartilage defect repair, we hypothesized that treatment with recombinant human FGF18 (sprifermin) would increase matrix synthesis in a defect model, thus improving integration strength. To test this hypothesis, 6 mm cartilage cylinders were harvested from juvenile bovine knees. A central 3 mm defect was created in each explant, and this core was removed and replaced. Resulting constructs were cultured in control or sprifermin-containing medium (weekly 24-h exposure of 100 ng/ml sprifermin) for 4 weeks. Mechanical testing, biochemical analysis, micro-CT, scanning electron microscopy, and histology were used to assess matrix production, adhesive strength, and structural properties of the cartilage-cartilage interface. Results showed greater adhesive strength, increased collagen content, and larger contact areas between core and annular cartilage in the sprifermin-treated group. These findings present a novel treatment for cartilage injuries that have potential to enhance defect healing and lateral cartilage-cartilage integration. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2648-2656, 2018.

Periostin contributes to the maturation and shape retention of tissue-engineered cartilage

Traditional tissue-engineered cartilage applied in clinical practice consists of cell suspensions or gel-form materials for which it is difficult to maintain their shapes. Although biodegradable polymer scaffolds are used for shape retention, deformation after transplantation can occur. Here, we showed that periostin (PN), which is abundantly expressed in fibrous tissues, contributes to the maturation and shape retention of tissue-engineered cartilage through conformational changes in collagen molecules. The tissue-engineered cartilage transplanted in an environment lacking PN exhibited irregular shapes, while transplants originating from chondrocytes lacking PN showed limited regeneration. In the in vitro assay, PN added to the culture medium of chondrocytes failed to show any effects, while the 3D culture embedded within the collagen gel premixed with PN (10 μg/mL) enhanced chondrogenesis. The PN-mediated collagen structure enhanced the mechanical strength of the surrounding fibrous tissues and activated chondrocyte extracellular signaling by interstitial fibrous tissues.

Optimal bone fracture repair requires 24R,25-dihydroxyvitamin D3 and its effector molecule FAM57B2.

The biological activity of 24R,25-dihydroxyvitamin D3 [24R,25(OH)2D3] remains controversial, but it has been suggested that it contributes to fracture healing. Cyp24a1-/- mice, synthesizing no 24R,25(OH)2D3, show suboptimal endochondral ossification during fracture repair, with smaller callus and reduced stiffness. These defects were corrected by 24R,25(OH)2D3 treatment, but not by 1,25-dihydroxyvitamin D3. Microarrays with Cyp24a1-/- callus mRNA identified FAM57B2 as a mediator of the 24R,25(OH)2D3 effect. FAM57B2 produced lactosylceramide (LacCer) upon specific binding of 24R,25(OH)2D3. Fam57b inactivation in chondrocytes (Col2-Cre Fam57bfl/fl) phenocopied the callus formation defect of Cyp24a1-/- mice. LacCer or 24R,25(OH)2D3 injections restored callus volume, stiffness, and mineralized cartilage area in Cyp24a1-null mice, but only LacCer rescued Col2-Cre Fam57bfl/fl mice. Gene expression in callus tissue suggested that the 24R,25(OH)2D3/FAM57B2 cascade affects cartilage maturation. We describe a previously unrecognized pathway influencing endochondral ossification during bone repair through LacCer production upon binding of 24R,25(OH)2D3 to FAM57B2. Our results identify potential new approaches to ameliorate fracture healing.

Cartilage tissue formation through assembly of microgels containing mesenchymal stem cells

Current clinical approaches to treat articular cartilage degeneration provide only a limited ability to regenerate tissue with long-term durability and functionality. In this application, injectable bulk hydrogels and microgels containing stem cells can provide a suitable environment for tissue regeneration. However insufficient cell–cell interactions, low differentiation efficiency and poor tissue adhesion hinder the formation of high-quality hyaline type cartilage. Here, we have designed a higher order tissue-like structure using injectable cell-laden microgels as the building blocks to achieve human bone marrow-derived mesenchymal stem cell (hBMSC) long-term maintenance and chondrogenesis. We have demonstrated that a 4-arm poly(ethylene glycol)-N-hydroxysuccinimide (NHS) crosslinker induces covalent bonding between the microgel building blocks as well as the surrounding tissue mimic. The crosslinking process assembles the microgels into a 3D construct and preserves the viability and cellular functions of the encapsulated hBMSCs. This assembled microgel construct encourages upregulation of chondrogenic markers in both gene and glycosaminoglycan (GAG) expression levels. In addition, the regenerated tissue in the assembled microgels stained positively with Alcian blue and Safranin O exhibiting unique hyaline-like cartilage features. Furthermore, the immunostaining showed a favourable distribution and significantly higher content of type II collagen in the assembled microgels when compared to both the bulk hydrogel and pellet cultures. Collectively, this tissue adhesive hBMSC-laden microgel construct provides potential clinical opportunities for articular cartilage repair and other applications in regenerative medicine. Statement of SignificanceA reliable approach to reconstruct durable and fully functional articular cartilage tissue is required for effective clinical therapies. Here, injectable hydrogels together with cell-based therapies offer new treatment strategies in cartilage repair. For effective cartilage regeneration, the injectable hydrogel system needs to be bonded to the surrounding tissue and at the same time needs to be sufficiently stable for prolonged chondrogenesis. In this work, we utilised injectable hBMSC-laden microgels as the building blocks to create an assembled construct via N-hydroxysuccinimide-amine coupling. This crosslinking process also allows for rapid bonding between the assembled microgels and a surrounding tissue mimic. The resultant assembled microgel-construct provides both a physically stable and biologically dynamic environment for hBMSC chondrogenesis, leading to the production of a mature hyaline type cartilage structure.