Repair of large osteochondral defects with allogeneic cartilaginous aggregates formed from bone marrow-derived cells using RWV bioreactor.

Our objective was to examine the technique of regenerating cartilage tissue from bone marrow-derived cells by three-dimensional (3D) culture using the rotating wall vessel (RWV) bioreactor. Three-dimensional and cylindrical aggregates of allogeneic cartilage with dimensions of 10 x 5 mm (height x diameter) formed by the RWV bioreactor were transplanted into osteochondral defects of Japanese white rabbits (Group T, n = 15). For the control, some osteochondral defects were left empty (Group C, n = 18). At 4, 8, and 12 weeks postimplantation, the reparative tissues were evaluated macroscopically, histologically, and biochemically. In Group T at as early as 4 weeks, histological observation, especially via safranin-O staining, suggested that the reparative tissues resembled hyaline cartilage. And we observed no fibrous tissues between reparative tissue and adjacent normal tissues. In the deeper portion of the bony compartment, the osseous tissues were well remodeled. At 4 and 8 weeks postimplantation, the mean histological score of Group T was significantly better than that of Group C (p < 0.05). The glycosaminoglycans (GAG)/DNA ratio in both groups increased gradually from 4 to 8 weeks and then decreased from 8 to 12 weeks. We herein report the first successful regeneration of cartilage in osteochondral defects in vivo using allogeneic cartilaginous aggregates derived from bone marrow-derived cells by 3D culture using the RWV bioreactor.     

Recombinant human bone morphogenetic protein‐7 enhances fracture healing in an ischemic environment

Ischemia predisposes orthopedic trauma patients to delayed fracture healing or nonunion. The goal of this study was to test the ability of bone morphogenetic protein 7 (BMP7) to stimulate fracture repair in an ischemic environment. Ischemic fractures were generated in male adult mice by resecting the femoral artery prior to the creation of a nonstabilized tibia fracture. Recombinant human BMP7 (rhBMP7, 50 µg) was injected into the fracture site immediately after surgery. At 7 days after injury, more tissue vascularization was observed in rhBMP7 treated fractures. Histomorphometric analyses revealed that rhBMP7 induced more cartilage at day 7, more callus and bone at days 14 and 28, and more adipose tissue and fibrous tissue at days 7, 14, and 28 compared to controls (n = 5/group/time). At day 28, all fractures treated with rhBMP7 (50 µg, n = 5) healed, whereas only three of five control fractures exhibited slight bony bridging. In addition, we found that rhBMP7 (both 10 and 50 µg) significantly increased the amount of cartilage compared to controls in stabilized fractures, confirming its chondrogenic effect. Lastly, using bone marrow transplantation, we determined that no donor‐derived osteocytes or chondrocytes were present in rhBMP7‐treated fractures, suggesting rhBMP7 did not recruit mesenchymal stem cells from the bone marrow to the fracture site. In conclusion, our results indicate that rhBMP7 is a promising treatment for fractures with severely disrupted blood supply. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:687–696, 2010     

Bioengineered Cartilage in a Scaffold‐Free Method by Human Cartilage‐Derived Progenitor Cells: A Comparison With Human Adipose‐Derived Mesenchymal Stromal Cells

The objective of our study was to investigate chondrogenesis potential of human adipose‐derived mesenchymal stromal cells (MSCs), using as a positive control a human source of cartilage‐derived progenitor cells (PCs). This source of PCs was recently described by our group and dwells on the surface of nasoseptal cartilage. Histological analysis using Safranin O staining and immunofluorescence for actin filaments and collagen type II was performed on three‐dimensional (3D) pellet cultures. Cartilage PCs and adipose MSCs showed similarities in monolayer culture related to cell morphology and proliferation. Our 3D pellet cultures substantially reduced the actin stress and after 21 days under chondrogenic medium, we observed an increase in the pellet diameter for cartilage PCs (7.4%) and adipose MSCs (21.2%). Adipose‐derived MSCs responded to chondrogenic stimulus, as seen by positive areas for collagen type II, but they were not able to recreate a mature extracellular matrix. Using semi‐quantitative analysis, we observed a majority of Safranin O areas rising from blue (no stain) to orange (moderate staining) and no changes in fibroblastic morphology (P < 0.0001). For cartilage PCs, chondrogenic induction is responsible for morphological changes and a high percentage of matrix area/number of cells (P ≤ 0.0001), evaluated by computerized histomorphometry. Morphological analyses reveal that adipose‐derived MSCs were not able to recreate a bioengineered cartilage. The cost of culture was reduced, as the cartilage PCs under growth‐factor free medium exhibit a high score for cartilage formation compared with the induced adipose mesenchymal stromal cells (P = 0.0021). Using a pellet 3D culture, our cartilage PCs were able to produce a cartilage tissue in vitro, leading to the future development of bioengineered products.     

Articular cartilage repair using an intra‐articular magnet and synovium‐derived cells

The purpose of this study was to investigate the chondrogenic potential of magnetically labeled synovium‐derived cells (M‐SDCs) and examine whether M‐SDCs could repair the articular cartilage using an intra‐articular magnet after delivery to the lesion. Synovium‐derived cells (SDCs) were cultured from the synovium of a rat knee, and were magnetically labeled with ferumoxides. M‐SDCs were examined with a transmission electron microscope. A pellet culture system was used to evaluate the chondrogenic potential of M‐SDCs in a magnetic field. In a rat model, allogeneic M‐SDCs were injected into the knee after we made an osteochondral defect on the patellar groove and implanted an intra‐articular magnet at the bottom of the defect. We histologically examined the defects at 48 h, 4 weeks, 8 weeks, and 12 weeks after treatment. Electron microscopy showed the transfection of ferumoxides into SDCs. The pellet cultures revealed the chondrogenic potential of M‐SDCs in a magnetic field. M‐SDCs accumulated in the osteochondral defect at 48 h after treatment, and we confirmed the regeneration of the articular cartilage at 4 weeks, 8 weeks, and 12 weeks after treatment using an intra‐articular magnet. We demonstrated that articular cartilage defects could be repaired using an intra‐articular magnet and M‐SDCs. We believe that this system will be useful to repair human articular cartilage defects. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:531–538, 2011     

Self‐Assembled Infrapatellar Fat‐Pad Progenitor Cells on a Poly‐ε‐Caprolactone Film For Cartilage Regeneration

Cartilage defects resulting from osteoarthritis (OA) or physical injury can severely reduce the quality of life for sufferers. Current treatment options are costly and not always effective in producing stable hyaline cartilage. Here we investigated a new treatment option that could potentially repair and regenerate damaged cartilage tissue. This novel approach involves the application of infrapatellar fat‐pad derived chondroprogenitor cells onto a mechanically stable biodegradable polymer film that can be easily implanted into a defect site. Poly‐ε‐caprolactone (PCL) films were fabricated via solvent casting in either acetone or chloroform. The hydrophobicity, mechanical properties, and surface morphology of the films were examined. Progenitor cells from infrapatellar fat‐pad were isolated, expanded, and then seeded onto the films. The cells were allowed to self‐assemble on films, and these were then cultured in a chemically defined chondrogenic media for 28 days. The self‐assembled tissue was characterized via histological staining, gene expression analysis, immunohistochemistry, and biochemical analysis. Chondrogenic differentiation was induced to generate a cartilaginous matrix upon the films. Despite differences between in the appearance, surface morphology, and mechanical properties of the films cast in chloroform or acetone, both methods produced tissues rich in sulfated glycosaminoglycan and collagen, although the extracellular matrix produced on chloroform‐cast films appeared to contain more collagen type II and less collagen type I than acetone‐cast films. These self‐assembled constructs have the potential to be implanted into defect sites as a potential treatment for cartilage defect regeneration.     

Human platelet-rich plasma stimulates migration and chondrogenic differentiation of human subchondral progenitor cells

In cartilage repair, platelet‐rich plasma (PRP) is used in one‐step approaches utilizing microfracture and matrix‐induced chondrogenesis procedures, bone marrow‐derived cell transplantation, or intra‐articular injection. The aim of our study was to evaluate the effect of human PRP on the migration and chondrogenic differentiation of human subchondral progenitors. Human progenitors were derived from subchondral cortico‐spongious bone (CSP), were analyzed for their migration capacity upon PRP treatment in 96‐well chemotaxis assays and cultured in high‐density pellet cultures under serum‐free conditions in the presence of 5% PRP. Chemotaxis assays showed that 0.1–100% PRP significantly (p < 0.05) stimulate the migration of CSP compared to untreated controls. Histological staining of proteoglycan and immuno‐staining of type II collagen indicated that progenitors stimulated with PRP show significantly increased cartilage matrix formation compared to untreated progenitors. Real‐time gene expression analysis of typical chondrocyte marker genes as well as osteogenic and adipogenic markers like osteocalcin and fatty acid binding protein showed that PRP induces the chondrogenic differentiation sequence of human progenitors in high‐density pellet cultures, while osteogenic or adipogenic differentiation was not evident. These results suggest that human PRP may enhance the migration and stimulate the chondrogenic differentiation of human subchondral progenitor cells known from microfracture. © 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:845–852, 2012     

Chondrogenic differentiation and lubricin expression of caprine infraspinatus tendon cells

Reparative strategies for the treatment of injuries to tendons, including those of the rotator cuff of the shoulder, need to address the formation of the cartilage which serves as the attachment apparatus to bone and which forms at regions undergoing compressive loading. Moreover, recent work indicates that cells employed for rotator cuff repair may need to synthesize a lubricating glycoprotein, lubricin, which has recently been found to play a role in tendon tribology. The objective of the present study was to investigate the chondrogenic differentiation and lubricin expression of caprine infraspinatus tendon cells in monolayer and three‐dimensional culture, and to compare the behavior with bone marrow‐derived mesenchymal stem cells (MSCs). The results demonstrated that while tendon cells in various media, including chondrogenic medium, expressed lubricin, virtually none of the MSCs synthesized this important lubricating molecule. Also of interest was that the cartilage formation capacity of the tendon cells grown in pellet culture in chondrogenic medium was comparable with MSCs. These data inform the use of tendon cells for rotator cuff repair, including for fibrocartilaginous zones. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:716–725, 2010     

Tissue neogenesis and STRO‐1 expression in immature and mature articular cartilage

This study determined the potential for neotissue formation and the role of STRO‐1+ cells in immature versus mature articular cartilage. Cartilage explants from immature and mature bovine knee joints were cultured for up to 12 weeks and stained with safranin‐O, for type II collagen and STRO‐1. Bovine chondrocyte pellet cultures and murine knee joints at the age of 2 weeks and 3 months, and surgically injured cartilage, were analyzed for changes in STRO‐1 expression patterns. Results show that immature explants contained more STRO‐1+ cells than mature explants. After 8 weeks in culture, immature explants showed STRO‐1+ cell proliferation and newly formed tissue, which contained glycosaminoglycan and type II collagen. Mature cartilage explants showed only minimal cell expansion and neotissue formation. Pellet cultures with chondrocytes from immature cartilage showed increased glycosaminoglycan synthesis and STRO‐1+ staining, as compared to pellets with mature chondrocytes. The frequency of STRO‐1+ cells in murine knee joints significantly declined with joint maturation. Following surgical injury, immature explants had higher potential for tissue repair than mature explants. In conclusion, these findings suggest that the high percentage of STRO‐1+ cells in immature cartilage changes with joint maturation. STRO‐1+ cells have the potential to form new cartilage spontaneously and after tissue injury. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:96–102, 2010     

Mechanical Stimulation by Ultrasound Enhances Chondrogenic Differentiation of Mesenchymal Stem Cells in a Fibrin‐Hyaluronic Acid Hydrogel

Chondrogenic differentiation and cartilage tissue formation derived from stem cells are highly dependent on both biological and mechanical factors. This study investigated whether or not fibrin‐hyaluronic acid (HA) coupled with low‐intensity ultrasound (LIUS), a mechanical stimulation, produces an additive or synergistic effect on the chondrogenesis of rabbit mesenchymal stem cells (MSCs) derived from bone marrow. For the purpose of comparison, rabbit MSCs were first cultured in fibrin‐HA or alginate hydrogels, and then subjected to chondrogenic differentiation in chondrogenic‐defined medium for 4 weeks in the presence of either transforming growth factor‐beta3 (TGF‐β3) (10 ng/mL) or LIUS treatment (1.0 MHz and 200 mW/cm²). The resulting samples were evaluated at 1 and 4 weeks by histological observation, chemical assays, and mechanical analysis. The fibrin‐HA hydrogel was found to be more efficient than alginate in promoting chondrogenesis of the MSCs by producing a larger amount of sulfated glycosaminoglycans (GAGs) and collagen, and engineered constructs made with the hydrogel demonstrated higher mechanical strength. At 4 weeks of tissue culture, the chondrogenesis of the MSCs in fibrin‐HA were shown to be further enhanced by treatment with LIUS, as observed by analyses for the amounts of GAGs and collagen, and mechanical strength testing. In contrast, TGF‐β3, a well‐known chondrogenic inducer, showed a marginal additive effect in the amount of collagen only. These results revealed that LIUS further enhanced chondrogenesis of the MSCs cultured in fibrin‐HA, in vitro, and suggested that the combination of fibrin‐HA and LIUS is a useful tool in constructing high‐quality cartilage tissues from MSCs.     

Petaloid recombinant peptide enhances in vitro cartilage formation by synovial mesenchymal stem cells

In vitro chondrogenesis of mesenchymal stem cells (MSCs) mimics in vivo chondrogenesis of MSCs. However, the size of the cartilage pellets that can be attained in vitro is limited by current methods; therefore, some modifications are required to obtain larger pellets. Petaloid pieces of recombinant peptide (petaloid RCP) have the advantage of creating spaces between cells in culture. The RCP used here is based on the alpha‐1 sequence of human collagen type I and contains 12 Arg‐Gly‐Asp motifs. We examined the effect and mechanisms of adding petaloid RCP on the in vitro chondrogenesis of human synovial MSCs by culturing 125k cells with or without 0.125 mg petaloid RCP in chondrogenic medium for 21 days. The cartilage pellets were sequentially analyzed by weight, sulfated glycosaminoglycan content, DNA retention, and histology. Petaloid RCP significantly increased the weight of the cartilage pellets: The petaloid RCP group weighed 7.7 ± 1.2 mg (n = 108), whereas the control group weighed 5.3 ± 1.6 mg. Sulfated glycosaminoglycan and DNA contents were significantly higher in the petaloid RCP group than in the control group. Light and transmission electron microscopy images showed that the petaloid RCP formed the framework of the pellet at day 1, the framework was broken by production of cartilage matrix by the synovial MSCs at day 7, and the cartilage pellet grew larger, with diffuse petaloid RCP remaining, at day 21. Therefore, petaloid RCP formed a framework for the pellet, maintained a higher cell number, and promoted in vitro cartilage formation of synovial MSCs. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. J Orthop Res 37:1350–1357, 2019.     

Repair of large osteochondral defects in rabbits using porous hydroxyapatite/collagen (HAp/Col) and fibroblast growth factor‐2 (FGF‐2)

Articular cartilage has a limited capacity for self‐renewal. This article reports the development of a porous hydroxyapatite/collagen (HAp/Col) scaffold as a bone void filler and a vehicle for drug administration. The scaffold consists of HAp nanocrystals and type I atelocollagen. The purpose of this study was to investigate the efficacy of porous HAp/Col impregnated with FGF‐2 to repair large osteochondral defects in a rabbit model. Ninety‐six cylindrical osteochondral defects 5 mm in diameter and 5 mm in depth were created in the femoral trochlear groove of the right knee. Animals were assigned to one of four treatment groups: porous HAp/Col impregnated with 50 µl of FGF‐2 at a concentration of 10 or 100 µg/ml (FGF10 or FGF100 group); porous HAp/Col with 50 µl of PBS (HAp/Col group); and no implantation (defect group). The defect areas were examined grossly and histologically. Subchondral bone regeneration was quantified 3, 6, 12, and 24 weeks after surgery. Abundant bone formation was observed in the HAp/Col implanted groups as compared to the defect group. The FGF10 group displayed not only the most abundant bone regeneration but also the most satisfactory cartilage regeneration, with cartilage presenting a hyaline‐like appearance. These findings suggest that porous HAp/Col with FGF‐2 augments the cartilage repair process. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:677–686, 2010     

Transplantation of human skeletal muscle‐derived progenitor cells ameliorates knee osteoarthritis in streptozotocin‐induced diabetic mice

The epidemiological and experimental evidence suggests that diabetes can be an independent risk factor for osteoarthritis. The osteoarthritis‐like cartilage damage has been shown in streptozotocin‐induced diabetic mice. The therapeutic effects of human skeletal muscle‐derived progenitor cells (HSMPCs) on diabetic osteoarthritis still remain unclear. Here, we investigated the therapeutic potential of HSMPCs on diabetic knee osteoarthritis. The in vitro chondrogenic ability of HSMPCs was determined by pellet culture assay. Male mice were used to develop the model of streptozotocin‐induced type 1 diabetes and its related osteoarthritis. HSMPCs were injected intra‐articularly to rescue osteoarthritis. Protein expressions of advanced glycation end‐products, cyclooxygenase‐2, and type‐2 collagen in tissues were determined by immunohistochemistry. The pellet culture assay showed that HSMPCs cultured in differentiation medium for chondrogenesis significantly produced larger pellets with an overproduction of extracellular matrix than in growth medium. In in vivo experiments, intra‐articular injection of HSMPCs for 4 weeks significantly prevented the progression of degenerative changes in the cartilage of streptozotocin‐induced diabetic mice, including an obvious increase of total articular cartilage thickness and a decrease of fibrous cartilage thickness. HSMPCs transplantation also exerted the decline in advanced glycation end‐products and cyclooxygenase‐2 protein expression, but increased the type‐2 collagen protein expression in streptozotocin‐induced osteoarthritic cartilages. Moreover, HSMPCs transplantation also inhibited the increased serum interleukin‐6 and matrix metalloproteinase‐3 levels in diabetic mice. These results demonstrated for the first time that HSMPCs transplantation ameliorates cartilage degeneration in diabetes‐related osteoarthritis mice. These findings suggest that HSMPCs transplantation may apply as a potential therapeutic use of diabetes‐related osteoarthritis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1886–1893, 2017.

     

Skeletal tissue growth, differentiation and mineralization in the NASA rotating wall vessel

The NASA Rotating Wall Vessel (RWV) is a device that creates a unique environment that supports three-dimensional tissue growth, a heightened level of cell differentiation and randomizes the position of the downward gravitational force on cells. Embryonic bone formation encompasses a cascade of chondrogenic and osteogenic events, which can be altered by changes in gravitational loading. These studies were conducted to determine if the chondrogenic cascade in bone formation would be enhanced or hindered in the unique culture environment of the RWV. Embryonic mouse pre-bone tissues were placed in the RWV at one of four different stages of chondrogenesis, ranging from undifferentiated mesenchyme cells to chondrocytes on the verge of undergoing terminal chondrocyte differentiation. After culture, tissues were analyzed for their size, the amount of alkaline phosphatase (ALP) activity and their ability to form a mineralized matrix. Tissue consisting of cells at the early phase of chondrogenesis grew very little and did not differentiate or mineralize when cultured in the RWV. Some tissues were cultured for short periods in the RWV then cultured in standard culture dishes (SCD). Following this culture regime, the cartilage grew only a small amount, but alkaline phosphatase activity increased, and some mineralized regions formed. The pattern of mineralization was abnormal, with two mineralized zones at each end of the cartilage instead of a single central zone. Tissues that were at the three more advanced stages of chondrogenesis when placed in the RWV showed substantial growth, differentiation and mineralization. Mineralization patterns in these older tissues was normal. Tissues at the oldest stage of chondrogenesis showed more growth and as much or more mineralization as tissue cultured only in SCD. These data suggest that exposure to the RWV at early stages of chondrogenesis severely limits the ability for cartilage growth and yields abnormal downstream morphogenesis. However, at later stages of chondrogenesis, the RWV environment may be beneficial and enhance growth and development. Future studies to characterize intercellular signaling molecules and gene expression activities of chondrocytes in the RWV will be valuable for understanding the mechanism of skeletogenesis.     

Influence of bone‐derived matrices on generation of bone in an ectopic rat model

Most bone regeneration experimental models that test bone‐derived matrices take place in conjunction with the native bone. Here, we compared the relative effectiveness of bone matrix components on bone‐marrow‐directed osteogenesis in an ectopic model. Cortical bone cylinders consisted of diaphysis of DA rat femurs. They were either demineralized (DBM), deproteinized (HABM), or nontreated (MBM). Fresh bone marrow was placed into cylinders and implanted at subcutaneous thoracic sites of 2‐month‐old DA rats. At designated times the cylinders were surgically removed from the animals. Microradiographs of DBM and histology of DBM and MBM cylinders demonstrated progressive increase in mineralized bone volume and its trabecular configuration. Bone filled the inner volume of DBM and MBM cylinders within 4 weeks, while in HABM cylinders mostly granulation tissue developed. In the DBM cylinders cartilage deposited within 10 days, while in the MBM cylinders bone was directly deposited. As early as day 3 after marrow transplantation, marrow cells interacting with DBM increased significantly the genes that express the cartilage and the bone phenotype. In conclusion, organic components of bone are needed for marrow‐directed osteogenesis. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:664–670, 2010     

MT1‐MMP and Type II Collagen Specify Skeletal Stem Cells and Their Bone and Cartilage Progeny

Skeletal formation is dependent on timely recruitment of skeletal stem cells and their ensuing synthesis and remodeling of the major fibrillar collagens, type I collagen and type II collagen, in bone and cartilage tissues during development and postnatal growth. Loss of the major collagenolytic activity associated with the membrane‐type 1 matrix metalloproteinase (MT1‐MMP) results in disrupted skeletal development and growth in both cartilage and bone, where MT1‐MMP is required for pericellular collagen dissolution. We show here that reconstitution of MT1‐MMP activity in the type II collagen‐expressing cells of the skeleton rescues not only diminished chondrocyte proliferation, but surprisingly, also results in amelioration of the severe skeletal dysplasia associated with MT1‐MMP deficiency through enhanced bone formation. Consistent with this increased bone formation, type II collagen was identified in bone cells and skeletal stem/progenitor cells of wildtype mice. Moreover, bone marrow stromal cells isolated from mice expressing MT1‐MMP under the control of the type II collagen promoter in an MT1‐MMP‐deficient background showed enhanced bone formation in vitro and in vivo compared with cells derived from nontransgenic MT1‐MMP‐deficient littermates. These observations show that type II collagen is not stringently confined to the chondrocyte but is expressed in skeletal stem/progenitor cells (able to regenerate bone, cartilage, myelosupportive stroma, marrow adipocytes) and in the chondrogenic and osteogenic lineage progeny where collagenolytic activity is a requisite for proper cell and tissue function.     

Characterization of the chondrogenic and osteogenic potential of male and female human muscle‐derived stem cells: Implication for stem cell therapy

People of all backgrounds are susceptible to bone and cartilage damage, and these injuries can be debilitating. Current treatments for bone and cartilage injuries are less than optimal, and we are interested in developing new approaches to treat these diseases, specifically using human muscle‐derived stem cells (hMDSCs). Our lab previously demonstrated that sex differences exist between male and female murine MDSCs; thus, this paper sought to investigate whether sex differences also exist in hMDSCs. In the present study, we characterized the chondrogenic and osteogenic sex differences of hMDSCs in vitro and in vivo. We performed in vitro osteogenic and chondrogenic differentiation using hMDSC pellet cultures. As demonstrated by microCT, histology, and immunohistochemistry, male hMDSCs were more chondrogenic and osteogenic than their female counterparts in vitro. No differences were observed based on the sex of hMDSCs in osteogenic and chondrogenic gene expression and cell surface markers. For our in vivo study, we transduced hMDSCs with lenti‐BMP2/GFP and transplanted these cells into critical‐sized calvarial defects in mice. MicroCT results revealed that male hMDSCs regenerated more bone at 2 weeks and demonstrated higher bone density at 4 and 6 weeks than female hMDSCs. Histology demonstrated that both male and female hMDSCs regenerated functional bone. Clinical relevance: These studies reinforce that stem cells isolated from male and female patients differ in function, and we should disclose the sex of cells used in future studies. Considering sex differences of hMDSCs may help to improve cell‐based therapies for autologous cell treatment of bone and cartilage damage. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1339–1349, 2019.     

Repair of large full‐thickness articular cartilage defects by transplantation of autologous uncultured bone‐marrow‐derived mononuclear cells

The objective of this study was to investigate the feasibility of autologous uncultured bone marrow‐derived mononuclear cell transplantation in large full‐thickness cartilage regeneration. After fixing with a hinged external fixator, the entire surface of the left tibial plateau was resected and large full‐thickness cartilage defects were formed in 48 rabbits. Animals were divided into four groups: autologous uncultured bone marrow‐derived mononuclear cells with fibrin gel (BMC), autologous uncultured peripheral blood‐derived mononuclear cells with fibrin gel (PBC), fibrin gel alone (GEL), or nothing (CON) transplanted to the articular cavity 7 days after the operation. The rabbits were killed 8 or 12 weeks after the operation. The repair of defects was investigated histologically and scored using a histological and histochemical grading scale that was modified from the International Cartilage Repair Society Visual Histological Assessment Scale. To evaluate the regenerated cartilage, we also morphometrically measured the staining area positive for Safranin‐O or type II collagen and calculated the percentages of the positive staining areas with respect to the regenerated soft tissue area. Histological findings showed that the BMC group had superior cartilage repair compared with the other groups, and that the PBC and CON group showed better cartilage repair than did the GEL group. Histological scores and morphometrical measurements also showed the same results quantitively. The transplantation of autologous uncultured bone marrow‐derived mononuclear cells contributes to articular cartilage repair. The easy and safe method used in this study is potentially viable for clinical application. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:18–26, 2008