Glued periosteal grafts in the knee

Strategies to Convert Cells into Hyaline Cartilage: Magic Spells for Adult Stem Cells

Damaged hyaline cartilage gradually decreases joint function and growing pain significantly reduces the quality of a patient’s life. The clinically approved procedure of autologous chondrocyte implantation (ACI) for treating knee cartilage lesions has several limits, including the absence of healthy articular cartilage tissues for cell isolation and difficulties related to the chondrocyte expansion in vitro. Today, various ACI modifications are being developed using autologous chondrocytes from alternative sources, such as the auricles, nose and ribs. Adult stem cells from different tissues are also of great interest due to their less traumatic material extraction and their innate abilities of active proliferation and chondrogenic differentiation. According to the different adult stem cell types and their origin, various strategies have been proposed for stem cell expansion and initiation of their chondrogenic differentiation. The current review presents the diversity in developing applied techniques based on autologous adult stem cell differentiation to hyaline cartilage tissue and targeted to articular cartilage damage therapy.

Regenerative Potential of Perichondrium: A Tissue Engineering Perspective

The clinical relevance of perichondrium was recognized more than a century ago. In children and adolescents, perichondrium is essential for the formation and growth of the cartilaginous part of craniofacial features and must be considered during reconstructive surgery in the head and neck area. Also in adults, perichondrium must be preserved during surgical intervention for adequate postoperative healing and cartilage maintenance. Furthermore, the regenerative function of perichondrium in the ribs enables the harvesting of the rib cartilage tissue for reconstruction of craniofacial features. With the advancement of tissue engineering, renewed attention has been focused on the perichondrium, because without this crucial tissue, the function of cartilage engineered for craniofacial reconstruction is incomplete and may not be suitable for long-term reconstructive goals. Furthermore, interest in the perichondrium was revived owing to its possible role as a microenvironment containing stem and progenitor cells. Here we will revisit seminal studies on the perichondrium and review the current literature to provide a holistic perspective on the importance of this tissue in the context of regenerative medicine. We will also highlight the functional significance of perichondrium for cartilage tissue engineering.

Ex Vivo Systems to Study Chondrogenic Differentiation and Cartilage Integration

Articular cartilage injury and repair is an issue of growing importance. Although common, defects of articular cartilage present a unique clinical challenge due to its poor self-healing capacity, which is largely due to its avascular nature. There is a critical need to better study and understand cellular healing mechanisms to achieve more effective therapies for cartilage regeneration. This article aims to describe the key features of cartilage which is being modelled using tissue engineered cartilage constructs and ex vivo systems. These models have been used to investigate chondrogenic differentiation and to study the mechanisms of cartilage integration into the surrounding tissue. The review highlights the key regeneration principles of articular cartilage repair in healthy and diseased joints. Using co-culture models and novel bioreactor designs, the basis of regeneration is aligned with recent efforts for optimal therapeutic interventions.

Culturing Periosteum in Vitro: The Influence of Different Sizes of Explants

Periosteal transplantation is being used clinically to repair articular defects. Isolated cells and very small periosteal explants can be grown in tissue culture, but it will be necessary to test larger sizes for tissue engineering to be applied to clinical transplantation of periosteum. This study was conducted to assess the chondrogenic potential of different sizes of periosteal explants in agarose culture. Ninety-six rabbit tibial periosteal explants in three different sizes (small 1.5 × 2, medium 3 × 2, and large 4 × 6 mm, 32 pieces per size) were cultured in agarose suspension for 6 wk and given TGF-β1 (10 ng/mL) for the first 2 wk. Tissue growth, as indicated by normalized final wet weights of the explants after 6 wk in culture, was inversely proportional to explant size. Cartilage formation was observed in all explante. Histomorphometry revealed that cartilage formation was significantly better for the smaller explants (80% cartilage), but similar in the medium and larger explants (60% cartilage). Similar proportions of type II collagen were present in the different-sized explants. This study demonstrates that various sizes of periosteal explants can be grown in culture. Abundant cartilage was produced even by the large explants. © 1998 Elsevier Science Inc.

Enhanced articular cartilage by human mesenchymal stem cells in enzymatically mediated transiently RGDS-functionalized collagen-mimetic hydrogels

Recapitulation of the articular cartilage microenvironment for regenerative medicine applications faces significant challenges due to the complex and dynamic biochemical and biomechanical nature of native tissue. Towards the goal of biomaterial designs that enable the temporal presentation of bioactive sequences, recombinant bacterial collagens such as Streptococcal collagen-like 2 (Scl2) proteins can be employed to incorporate multiple specific bioactive and biodegradable peptide motifs into a single construct. Here, we first modified the backbone of Scl2 with glycosaminoglycan-binding peptides and cross-linked the modified Scl2 into hydrogels via matrix metalloproteinase 7 (MMP7)-cleavable or non-cleavable scrambled peptides. The cross-linkers were further functionalized with a tethered RGDS peptide creating a system whereby the release from an MMP7-cleavable hydrogel could be compared to a system where release is not possible. The release of the RGDS peptide from the degradable hydrogels led to significantly enhanced expression of collagen type II (3.9-fold increase), aggrecan (7.6-fold increase), and SOX9 (5.2-fold increase) by human mesenchymal stem cells (hMSCs) undergoing chondrogenesis, as well as greater extracellular matrix accumulation compared to non-degradable hydrogels (collagen type II; 3.2-fold increase, aggrecan; 4-fold increase, SOX9; 2.8-fold increase). Hydrogels containing a low concentration of the RGDS peptide displayed significantly decreased collagen type I and X gene expression profiles, suggesting a major advantage over either hydrogels functionalized with a higher RGDS peptide concentration, or non-degradable hydrogels, in promoting an articular cartilage phenotype. These highly versatile Scl2 hydrogels can be further manipulated to improve specific elements of the chondrogenic response by hMSCs, through the introduction of additional bioactive and/or biodegradable motifs. As such, these hydrogels have the possibility to be used for other applications in tissue engineering.

Statement of Significance

Recapitulating aspects of the native tissue biochemical microenvironment faces significant challenges in regenerative medicine and tissue engineering due to the complex and dynamic nature of the tissue. The ability to take advantage of, mimic, and modulate cell-mediated processes within novel naturally-derived hydrogels is of great interest in the field of biomaterials to generate constructs that more closely resemble the biochemical microenvironment and functions of native biological tissues such as articular cartilage. Towards this goal, the temporal presentation of bioactive sequences such as RGDS on the chondrogenic differentiation of human mesenchymal stem cells is considered important as it has been shown to influence the chondrogenic phenotype. Here, a novel and versatile platform to recreate a high degree of biological complexity is proposed, which could also be applicable to other tissue engineering and regenerative medicine applications.

Live Tissue Imaging to Elucidate Mechanical Modulation of Stem Cell Niche Quiescence

The periosteum, a composite cellular connective tissue, bounds all nonarticular bone surfaces. Like Velcro, collagenous Sharpey's fibers anchor the periosteum in a prestressed state to the underlying bone. The periosteum provides a niche for mesenchymal stem cells. Periosteal lifting, as well as injury, causes cells residing in the periosteum (PDCs) to change from an immobile, quiescent state to a mobile, active state. The physical cues that activate PDCs to home to and heal injured areas remain a conundrum. An understanding of these cues is key to unlocking periosteum's remarkable regenerative power. We hypothesized that changes in periosteum's baseline stress state modulate the quiescence of its stem cell niche. We report, for the first time, a three-dimensional, high-resolution live tissue imaging protocol to observe and characterize ovine PDCs and their niche before and after release of the tissue's endogenous prestress. Loss of prestress results in abrupt shrinkage of the periosteal tissue. At the microscopic scale, loss of prestress results in significantly increased crimping of collagen of periosteum's fibrous layer and a threefold increase in the number of rounded nuclei in the cambium layer. Given the body of published data describing the relationships between stem cell and nucleus shape, structure and function, these observations are consistent with a role for mechanics in the modulation of periosteal niche quiescence. The quantitative characterization of periosteum as a stem cell niche represents a critical step for clinical translation of the periosteum and periosteum substitute-based implants for tissue defect healing. Stem Cells Translational Medicine 2017;6:285-292.

Harnessing the Versatility of Bacterial Collagen to Improve the Chondrogenic Potential of Porous Collagen Scaffolds

Collagen I foams are used in the clinic as scaffolds to promote articular cartilage repair as they provide a bioactive environment for cells with chondrogenic potential. However, collagen I as a base material does not allow for precise control over bioactivity. Alternatively, recombinant bacterial collagens can be used as "blank slate" collagen molecules to offer a versatile platform for incorporation of selected bioactive sequences and fabrication into 3D scaffolds. Here, we show the potential of Streptococcal collagen-like 2 (Scl2) protein foams modified with peptides designed to specifically and noncovalently bind hyaluronic acid and chondroitin sulfate to improve chondrogenesis of human mesenchymal stem cells (hMSCs) compared to collagen I foams. Specific compositions of functionalized Scl2 foams lead to improved chondrogenesis compared to both nonfunctionalized Scl2 and collagen I foams, as indicated by gene expression, extracellular matrix accumulation, and compression moduli. hMSCs cultured in functionalized Scl2 foams exhibit decreased collagens I and X gene and protein expression, suggesting an advantage over collagen I foams in promoting a chondrocytic phenotype. These highly modular foams can be further modified to improve specific aspects chondrogenesis. As such, these scaffolds also have the potential to be tailored for other regenerative medicine applications.

The rigid curette technique for the application of fibrin bioadhesive during hip arthroscopy for articular cartilage lesions

Encouraging midterm results have recently been reported for the arthroscopic treatment of delaminating articular cartilage lesions at the capsulolabral junction of the hip joint using fibrin bioadhesive. The needle used to introduce the bioadhesive is long, flexible, and often difficult to position. We describe a novel technique for introducing the needle that allows accurate placement behind the delaminated articular cartilage pocket during hip arthroscopy.

Cell-laden biphasic scaffolds with anisotropic structure for the regeneration of osteochondral tissue

Sufficient treatment of chondral and osteochondral defects to restore function of the respective tissue remains challenging in regenerative medicine. Biphasic scaffolds that mimic properties of bone and cartilage are appropriate to regenerate both tissues at the same time. The present study describes the development of biphasic, but monolithic scaffolds based on alginate, which are suitable for embedding of living cells in the chondral part. Scaffolds are fabricated under sterile and cell-compatible conditions according to the principle of diffusion-controlled, directed ionotropic gelation, which leads to the formation of channel-like, parallel aligned pores, running through the whole length of the biphasic constructs. The synthesis process leads to an anisotropic structure, as it is found in many natural tissues. The two different layers of the scaffolds are characterized by different microstructure and mechanical properties which provide a suitable environment for cells to form the respective tissue. Human chondrocytes and human mesenchymal stem cells were embedded within the chondral layer of the biphasic scaffolds during hydrogel formation and their chondrogenic (re)differentiation was successfully induced. Whereas viability of non-induced human mesenchymal stem cells decreased during culture, cell viability of human chondrocytes and chondrogenically induced human mesenchymal stem cells remained high within the scaffolds over the whole culture period of 3 weeks, demonstrating successful fabrication of cell-laden centimetre-scaled constructs for potential application in regenerative treatment of osteochondral defects. Copyright © 2014 John Wiley & Sons, Ltd.

MACI - a new era?

Full thickness articular cartilage defects have limited regenerative potential and are a significant source of pain and loss of knee function. Numerous treatment options exist, each with their own advantages and drawbacks. The goal of this review is to provide an overview of the problem of cartilage injury, a brief description of current treatment options and outcomes, and a discussion of the current principles and technique of Matrix-induced Autologous Chondrocyte Implantation (MACI). While early results of MACI have been promising, there is currently insufficient comparative and long-term outcome data to demonstrate superiority of this technique over other methods for cartilage repair.

Pretreatment of periosteum with TGF-beta1 in situ enhances the quality of osteochondral tissue regenerated from transplanted periosteal grafts in adult rabbits

OBJECTIVE

To compare the efficacy of in situ transforming growth factor-beta1 (TGF-beta1)-pretreated periosteum to untreated periosteum for regeneration of osteochondral tissue in rabbits.

METHODS

In the pretreatment group, 12 month-old New Zealand white rabbits received subperiosteal injections of 200 ng of TGF-beta1 percutaneously in the medial side of the proximal tibia, 7 days prior to surgery. Control rabbits received no treatment prior surgery. Osteochondral transverse defects measuring 5mm proximal to distal and spanning the entire width of the patellar groove were created and repaired with untreated or TGF-beta1-pretreated periosteal grafts. Post-operatively the rabbits resumed normal cage activity for 6 weeks.

RESULTS

Complete filling of the defects with regenerated tissue was observed in both the TGF-beta1-pretreated and control groups with reformation of the original contours of the patellar groove. The total histological score (modified O'Driscoll) in the TGF-beta1-pretreated group, 20 (95% Confidence Interval (CI), 19-21), was significantly higher (P=0.0001) than the control group, 18 (16-19). The most notable improvements were in structural integrity and subchondral bone regeneration. No significant differences in glycosaminoglycan or type II collagen content, or equilibrium modulus were found between the surgical groups. The cambium of the periosteum regenerated at the graft harvest site was significantly thicker (P=0.0065) in the TGF-beta1-pretreated rabbits, 121 microm (94-149), compared to controls, 74 microm (52-96), after 6 weeks.

CONCLUSIONS

This study demonstrates that in situ pretreatment of periosteum with TGF-beta1 improves osteochondral tissue regeneration at 6-weeks post-op compared to untreated periosteum in 12 month-old rabbits.

Rejuvenation of periosteal chondrogenesis using local growth factor injection

OBJECTIVE

To examine the potential for rejuvenation of aged periosteum by local injection of transforming growth factor-beta1 (TGF-beta1) and insulin-like growth factor-1 (IGF-1) alone or in combination to induce cambium cell proliferation and enhance in vitro periosteal cartilage formation.

METHODS

A total of 367 New Zealand white rabbits (6, 12, and 24+ month-old) received subperiosteal injections of TGF-beta1 and/or IGF-1 percutaneously. After 1, 3, 5, or 7 days, the rabbits were sacrificed and cambium cellularity or in vitro cartilage forming capacity was determined.

RESULTS

A significant increase in cambium cellularity and thickness, and in vitro cartilage formation was observed after injection of TGF-beta1 alone or in combination with IGF-1. In 12 month-old rabbits, mean cambium cellularity increased 5-fold from 49 to 237 cells/mm and in vitro cartilage production increased 12-fold from 0.8 to 9.7 mg 7 days after TGF-beta1 (200 ng) injection compared to vehicle controls (P<0.0001). A correlation was observed between cambium cellularity and in vitro cartilage production (R2=0.98). An added benefit of IGF-1 plus TGF-beta1 on in vitro cartilage production compared to TGF-beta1 alone was observed in the 2 year-old rabbits. IGF-1 alone generally had no effect on either cambium cellularity or in vitro cartilage production in any of the age groups.

CONCLUSIONS

These results clearly demonstrate that it is possible to increase cambium cellularity and in vitro cartilage production in aged rabbit periosteum, to levels comparable to younger rabbits, using local injection of TGF-beta1 alone or in combination with IGF-1, thereby rejuvenating aged periosteum.

The cellular origin of cartilage-like tissue after periosteal transplantation of full-thickness articular cartilage defects: an experimental study using transgenic rats expressing green fluorescent protein

BACKGROUND

Periosteal transplantation is commonly used for the treatment of articular cartilage defects. However, the cellular origin of the regenerated tissue after periosteal transplantation has not been well defined. The objective of this study was to investigate the cellular origin of the regenerated tissue after periosteal transplantation.

METHOD

Free periosteum was harvested from the tibia of 10-week-old adolescent enhanced green fluorescent protein (GFP-) expressing transgenic Sprague Dawley (SD) rats and was transplanted to full-thickness articular cartilage defects of the patellar groove in normal 10-week-old adolescent SD rats. The periosteum was sutured to the defect with the cambium layer facing the joint cavity. 8 SD rats were killed at 4 weeks and 8 SD rats were killed at 8 weeks after surgery. The repaired tissue was assessed histologically and histochemically. GFP-positive cells derived from the donor periosteum could easily be detected in the repaired tissue by use of a fluorescent microscope.

RESULTS

At both 4 and 8 weeks after transplantation, the entire area of the defects had been repaired, with the regenerated tissue being well stained histologically with safranin-O. Most cells in the whole area of the regenerated tissue were GFP-positive, indicating that very few of the cells were GFP-negative cells originating from the recipient rats.

INTERPRETATION

This experiment demonstrates that most cells in regenerated tissue after periosteal transplantation using adolescent animals do not originate from recipient cells but from the periosteal cells of the donor.

The healing potential of the periosteum molecular aspects

The presence of pluripotential mesenchymal cells in the under surface of the periosteum in combination with growth factors regularly produced or released after injury, provide this unique tissue with an important role in the healing of bone and cartilage. The periosteum contributes in the secondary callus formation with cells and growth factors and should always be preserved and protected when surgery is performed for the management of a fracture. The current evidence about the cellular interactions, the stimulants and the signalling pathways related to osteogenesis and chondrogenesis is described. An essential knowledge of the basics related to the contribution of the periosteum in the healing of fractures, osteotomies, during the process of distraction osteogenesis and in some degree in the repair of cartilagenous defects, provides the surgeons with a better insight to understand the upcoming "biological" interventions in the management of skeletal injuries.

Clonal growth of human articular cartilage and the functional role of the periosteum in chondrogenesis

OBJECTIVE

Clinical cartilage repair with transplantation of cultured chondrocytes, the first described technique introduced in 1994, includes a periosteal membrane but today cells are also implanted without the periosteal combination. The aim of this study was to see if the periosteum had more than a biomechanical function and if the periosteum had a biological effect on the seeded cells tested in an agarose system in which the clonal growth in agarose and the external growth stimulation could be analysed.

METHODS

Four different experiments were used to study the growth of human chondrocytes in agarose and the periosteal influence. Human chondrocytes were isolated and transferred to either primary or secondary agarose culture. After 4 weeks, the total number of clones >50 microm was counted. Cocultures of chondrocytes and periosteal tissue, cultures of chondrocytes with conditioned medium from chondrocytes, periosteal cells and fibroblast were used to study a potential stimulatory effect on growth and different cytokines and growth factors were analysed.

RESULTS

It was found that the human chondrocytes had different growth properties in agarose with the formation of four different types of clones: a homogenous clone without matrix production, a homogenous clone with matrix production, a differentiated clone with matrix production and finally a differentiated clone without matrix production. The periosteum exerted a paracrine effect on cultured chondrocytes in agarose resulting in a higher degree of cloning. The chondrocytes produced significant amounts of interleukin (IL)-6, IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF) and transforming growth factor (TGF)-beta. The periosteum produced significant amounts of IL-6, IL-8 and TGF-beta. Cocultures of chondrocytes and periosteum demonstrated a potentiation of IL-6 and IL-8 release but not of TGF-beta and GM-CSF.

CONCLUSION

Articular chondrocytes are able to form clones of different properties in agarose and the periosteum has a capacity of stimulating chondrocyte clonal growth and differentiation and secretes significant amounts of IL-6, IL-8, GM-CSF and TGF-beta. It may be that the repair of cartilage defects with seeded chondrocytes could benefit from the combination with a periosteal graft. The production of TGF-beta by implanted chondrocytes could influence the chondrogenic cells in the periosteum to start a periosteal chondrogenesis and together with the matrix from implanted chondrocyte production, a repair of cartilaginous appearance may develop; a dual chondrogenic response is possible.

Osteochondral defects in the human knee: influence of defect size on cartilage rim stress and load redistribution to surrounding cartilage

PURPOSE

To determine the influence of osteochondral defect size on defect rim stress concentration, peak rim stress, and load redistribution to adjacent cartilage over the weightbearing area of the medial and lateral femoral condyles in the human knee.

METHODS

Eight fresh-frozen cadaveric knees were mounted at 30 degrees of flexion in a materials testing machine. Digital electronic pressure sensors were placed in the medial and lateral compartments of the knee. Each intact knee was first loaded to 700 N and held for 5 seconds. Dynamic pressure readings were recorded throughout the loading and holding phases. Loading was repeated over circular osteochondral defects (5, 8, 10, 12, 14, 16, 18, and 20 mm) in the 30 degrees weightbearing area of the medial and lateral femoral condyles.

RESULTS

Stress concentration around the rims of defects 8 mm and smaller was not demonstrated, and pressure distribution in this size range was dominated by the menisci. For defects 10 mm and greater, distribution of peak pressures followed the rim of the defect with a mean distance from the rim of 2.2 mm on the medial condyle and 3.2 mm on the lateral condyle. An analysis of variance with Bonferroni correction revealed a statistically significant trend of increasing radius of peak pressure as defect size increased for defects from 10 to 20 mm (P = .0011). Peak rim pressure values did not increase significantly as defects were enlarged from 10 to 20 mm. Load redistribution during the holding phase was also observed.

CONCLUSIONS

Rim stress concentration was demonstrated for osteochondral defects 10 mm and greater in size. This altered load distribution has important implications relating to the long-term integrity of cartilage adjacent to osteochondral defects in the human knee. Although the decision to treat osteochondral lesions is certainly multifactorial, a size threshold of 10 mm, based on biomechanical data, may be a useful adjunct to guide clinical decision making.

Repair of full-thickness cartilage defects in rabbit knees with free periosteal graft preincubated with transforming growth factor

This study compared different concentrations of transforming growth factor-beta 1 (TGF-beta1) used for short-term preincubation in vitro of large periosteal explants to determine the effect of chondrogenesis and the fate of repair cartilage over time. Eighty-two rabbits were divided into four groups: group A, non-grafted; group B, non-incubated grafted; group C, 100 ng/mL recombinant human (rh) TGF-beta1 preincubated grafted; and group D, 20 ng/mL rhTGF-beta1 preincubated grafted. Rabbits from each group were sacrificed at intervals between 2 and 24 weeks. Histologic slides were stained with safranin O and were scored based on a subjective scoring system. Group A healed with non-cartilaginous material. Group B healed with hyaline cartilage-like material with progressive thinning of this regenerated layer; at 24 weeks, this layer was fibrous tissue. Group C enhanced repair with hyaline cartilage-like material but accelerated early degeneration and osteophyte formation; the cartilage became fibrous tissue at 24 weeks. Group D did not enhance cartilaginous repair. At 24 weeks, all groups had the same result. The 100 ng/mL rhTGF-beta1 preincubation in vitro with periosteum enhanced early osteochondral repair but did not show prolonged durability. Clinical application of this growth factor necessitates further study.

Induction of CD-RAP mRNA during periosteal chondrogenesis

Induction of chondrogenesis and maintenance of the chondrocyte phenotype are critical events for autologous periosteal transplantation, which is a viable approach for cartilage repair. Cartilage-derived retinoic acid-sensitive protein (CD-RAP) is a recently discovered protein that is mainly produced in cartilage. During development, CD-RAP expression starts at the beginning of chondrogenesis and continues throughout cartilage maturation. In order to investigate the involvement of CD-RAP during periosteal chondrogenesis we have determined the nucleotide sequence of the rabbit CD-RAP mRNA and utilized this information to evaluate the temporal and spatial expression pattern of CD-RAP at the mRNA level during chondrogenesis. When the periosteal explants were cultured under chondrogenic conditions, the expression of CD-RAP was induced, as shown by a 40-fold increase in CD-RAP mRNA between days 7 and 10. The temporal expression pattern of CD-RAP closely mimicked that of collagen type IIB mRNA. Also, the CD-RAP mRNA was localized to the matrix forming chondrocytes in the cambium layer of the periosteum by in situ hybridization as indicated by colocalization with collagen type II mRNA and positive safranin O staining. These data suggest a regulatory role of CD-RAP in periosteal chondrogenesis, which is potentially important for both cartilage repair and fracture healing via callus formation.

Combined effects of insulin-like growth factor-1 and transforming growth factor-beta1 on periosteal mesenchymal cells during chondrogenesis in vitro

OBJECTIVE

Periosteum contains undifferentiated mesenchymal stem cells that have both chondrogenic and osteogenic potential, and has been used to repair articular cartilage defects. During this process, the role of growth factors that stimulate the periosteal mesenchymal cells toward chondrogenesis to regenerate articular cartilage and maintain its phenotype is not yet fully understood. In this study, we examined the effects of insulin-like growth factor-1 (IGF-1) and transforming growth factor-beta1 (TGF-beta1), alone and in combination, on periosteal chondrogenesis using an in vitro organ culture model.

METHODS

Periosteal explants from the medial proximal tibia of 2-month-old rabbits were cultured in agarose under serum free conditions for up to 6 weeks. After culture the explants were weighed, assayed for cartilage production via Safranin O staining and histomorphometry, assessed for proliferation via proliferative cell nuclear antigen (PCNA) immunostaining, and assessed for type II collagen mRNA expression via in situ hybridization.

RESULTS

IGF-1 significantly increased chondrogenesis in a dose-dependent manner when administered continuously throughout the culture period. Continuous IGF-1, in combination with TGF-beta1 for the first 2 days, further enhanced overall total cartilage growth. Immunohistochemistry for PCNA revealed that combining IGF-1 with TGF-beta1 gave the strongest proliferative stimulus early during chondrogenesis. In situ hybridization for type II collagen showed that continuous IGF-1 maintained type II collagen mRNA expression throughout the cambium layer from 2 to 6 weeks.

CONCLUSION

The results of this study demonstrate that IGF-1 and TGF-beta1 can act in combination to regulate proliferation and differentiation of periosteal mesenchymal cells during chondrogenesis.

Iliac bone graft for steroid-associated osteonecrosis of the femoral condyle

The use of steroid medication may predispose to osteonecrosis of the femoral condyle. However, there is a controversy regarding treatment of this disease, especially for lesions in advanced stages. Since 1987, the authors have treated such lesions by autologous osteoperiosteal graft obtained from the iliac bone. When limb alignment was affected by the disease, proximal tibial valgus or varus osteotomy was done concomitantly. The rationale for this method is to replace the necrotic bone and damaged cartilage by autogenous bone and periosteum, anticipating the chondrogenic potential of the latter. In this study, 10 knees in eight patients were reviewed to learn the outcome of this procedure with a mean followup of 79 months (range, 32-158 months). The grafts were incorporated successfully in nine joints, and satisfactory results were achieved in all patients. Therefore autologous iliac bone graft is a promising alternative for treatment of osteonecrosis, especially when patients are young and physically active.

Brief exposure to high-dose transforming growth factor-beta1 enhances periosteal chondrogenesis in vitro: a preliminary report

BACKGROUND

Articular cartilage has limited potential for repair. There have been various attempts aimed at improving the repair process in articular cartilage. Transforming growth factor-beta1 (TGF-beta1) has a stimulatory effect on chondrogenesis in periosteal explants. The purpose of the present study was to determine the effect of brief exposures (i.e., thirty and sixty minutes) of high concentrations of TGF-beta1 on periosteal chondrogenesis.

METHODS

Five hundred and seventy-three periosteal explants were harvested from forty-six two-month-old male New Zealand White rabbits. Explants were exposed to 50 or 100 ng/mL of TGF-beta1 for thirty or sixty minutes. The amount of cartilage formed was then determined with use of a standardized six-week agarose culture assay.

RESULTS

There was a significant increase in the amount of cartilage formation (p < 0.01), Type-II collagen content (p < 0.05), and sulfate incorporation (p < 0.0001) in explants treated with TGF-beta1. Maximal stimulation occurred following exposure to 100 ng/mL of TGF-beta1 for thirty minutes. There was also an increase in chondrocyte proliferation as measured by [ (3) H-] thymidine incorporation on day 5 of culture (p < 0.049).

CONCLUSIONS

The findings of this study indicate that exposure to TGF-beta1 has a stimulatory effect on periosteal chondrogenesis. This stimulatory effect is observed even with a very brief exposure time of thirty minutes.

CLINICAL RELEVANCE

A possible clinical application of these findings is exposure of periosteal grafts that are currently utilized clinically to resurface articular defects to TGF-beta1 during the short time between graft procurement and implantation into the joint. This may obviate the need for intra-articular administration of TGF-beta1 and may enhance the ultimate graft incorporation and quality of cartilage repair.

The spatiotemporal expression of TGF-beta1 and its receptors during periosteal chondrogenesis in vitro

Transforming growth factor-beta1 (TGF-beta1) has been shown to stimulate chondrogenesis in periosteal explants cultured in agarose suspension. TGF-betas exert their cellular effects through a heteromeric cell membrane receptor complex consisting of TGF-beta type I and type II receptors. In this study, the spatial and temporal expressions of the type I receptor (TbetaR-I), type II receptor (TbetaR-II) and endogenous TGF-beta1 in periosteal explants cultured in vitro were examined using reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry. The temporal changes in the expression of the TbetaR-I and TbetaR-II mRNAs correlated with that of TGF-beta1. Exogenous administration of TGF-beta1 upregulated the expression of both receptors and of the TGF-beta1 ligand in a biphasic pattern. The earlier peak of upregulation was observed at 7 days in culture. A later peak of upregulation was seen at 42 days, at which time cartilage formation reached a maximum. Immunohistochemical studies demonstrated co-localization of TbetaR-I and TbetaR-II simultaneously among the same cells expressing TGF-beta1. TGF-beta1 treatment increased the expression of TGF-beta1, TbetaR-I and TbetaR-II in mesenchymal cells in the cambium layer at 7 days in culture. Small round chondrocytes showed widely distributed immunoreactivity of TGF-beta1, TbetaR-I and TbetaR-II in the 42-day explants treated with TGF-beta1. These observations support the hypothesis that TGF-beta1 regulates the initiation and formation of cartilage during periosteal chondrogenesis.

Expression of beta1 integrins during periosteal chondrogenesis

OBJECTIVE

The interactions between integrins and extracellular matrix proteins are known to modulate cell behavior, and may be involved in regulating cartilage formation and repair. The purpose of this study was to determine the patterns and localization of expression of the beta1 integrins during cartilage formation by periosteum, which is used to repair articular cartilage.

DESIGN

Periosteal explants from 2-month-old rabbit medial proximal tibiae were cultured in agarose suspension for 0 to 6 weeks, with 10 ng/ml transforming growth factor-beta1 added for the first 2 days of culture. Integrin expressions were measured by reverse transcriptase-polymerase chain reaction (RT-PCR) and localized by immunohistochemistry.

RESULTS

Normal periosteum expressed the alpha1, alpha3, alpha5, beta1 subunits at low levels, and the proteins for all but the alpha3 subunits were identified by immunohistochemistry in the periosteum. Significant two- to five-fold up-regulation of the mRNA expression of the alpha1, alpha3, alpha5 and beta1 integrin subunits during the early proliferative stage of chondrogenesis was observed. The initial change was a five-fold increase in alpha5 expression on day 2 and a two-fold increase in alpha3 expression. On day 5, alpha1 expression was up-regulated (four-fold). beta1 expression was broadly up-regulated (three to four-fold) from day 5 to 14. In the early stage of chondrocyte differentiation, after day 14, alpha1 expression was down-regulated, while there was upregulation of alpha3 (three-fold), alpha5 (three-fold) and beta1 (four-fold) expressions. Thereafter, alpha1 expression was down-regulated, while alpha3, alpha5 and beta1 expressions were up-regulated again during matrix synthesis. Immunohistochemistry confirmed this late decrease in alpha1 levels and increase in alpha3, alpha5 and beta1 levels in chondrocytes.

CONCLUSIONS

These observations indicate that the beta1 integrins play an important role in the process of chondrogenesis in periosteum.

The role of periosteum in cartilage repair

Periosteum, which can be grown in cell and whole tissue cultures, may meet one or more of the three prerequisites for tissue engineered cartilage repair. Periosteum contains pluripotential mesenchymal stem cells with the potential to form either cartilage or bone. Because it can be transplanted as a whole tissue, it can serve as its own scaffold or a matrix onto which other cells and/or growth factors can be adhered. Finally, it produces bioactive factors that are known to be chondrogenic. The chondrocyte precursor cells reside in the cambium layer. These vary in total density and volume with age and in different donor sites. The advantages of whole tissue periosteal transplants for cartilage repair include the fact that this tissue meets the three primary requirements for tissue engineering: a source of cells, a scaffold for delivering and retaining them, and a source of local growth factors. Many growth factors that regulate chondrocytes and cartilage development are synthesized by periosteum in conditions conducive to chondrogenesis. These include transforming growth factor-beta 1, insulinlike growth factor-1, growth and differentiation factor-5, bone morphogenetic protein-2, integrins, and the receptors for these molecules. By additional study of the molecular events in periosteal chondrogenesis, it may be possible to optimize its capacity for articular cartilage repair.

Tissue-engineered fabrication of an osteochondral composite graft using rat bone marrow-derived mesenchymal stem cells

This study tested the tissue engineering hypothesis that construction of an osteochondral composite graft could be accomplished using multipotent progenitor cells and phenotype-specific biomaterials. Rat bone marrow-derived mesenchymal stem cells (MSCs) were culture-expanded and separately stimulated with transforming growth factor-beta1 (TGF-beta1) for chondrogenic differentiation or with an osteogenic supplement (OS). MSCs exposed to TGF-beta1 were loaded into a sponge composed of a hyaluronan derivative (HYAF-11) for the construction of the cartilage component of the composite graft, and MSCs exposed to OS were loaded into a porous calcium phosphate ceramic component for bone formation. Cell-loaded HYAFF-11 sponge and ceramic were joined together with fibrin sealant, Tisseel, to form a composite osteochondral graft, which was then implanted into a subcutaneous pocket in syngeneic rats. Specimens were harvested at 3 and 6 weeks after implantation, examined with histology for morphologic features, and stained immunohistochemically for type I, II, and X collagen. The two-component composite graft remained as an integrated unit after in vivo implantation and histologic processing. Fibrocartilage was observed in the sponge, and bone was detected in the ceramic component. Observations with polarized light indicated continuity of collagen fibers between the ceramic and HYAFF-11 components in the 6-week specimens. Type I collagen was identified in the neo-tissue in both sponge and ceramic, and type II collagen in the fibrocartilage, especially the pericellular matrix of cells in the sponge. These data suggest that the construction of a tissue-engineered composite osteochondral graft is possible with MSCs and different biomaterials and bioactive factors that support either chondrogenic or osteogenic differentiation.

Histomorphological and proliferative characterization of developing periosteal neochondrocytes in vitro

Periosteal chondrogenesis is relevant to cartilage repair and fracture healing. Cell proliferation is a limiting factor of cartilage production. We used an in vitro organ culture model to test the hypothesis that proliferative activity correlates with cell morphology. One hundred and four periosteal explants from 26 two-month old New Zealand rabbits were cultured for up to 42 days. They were analyzed histomorphologically, and immunohistochemically with proliferative cell nuclear antigen (PCNA). The periosteal neocartilage displayed a consistent zonal pattern of chondrocyte cell shapes. The flat cell zone from day 7 to 21, consisted of uniform-sized small spindle-shaped cells. The round cell zone, which appeared on day 14, consisted of variable-sized round cells averaging 510 +/- 250 microm2 in area. They were subdivided into small round (<510 microm2) and large round cells (>510 microm2). The proliferative index was highest in the small round cell group (32 +/- 6%), intermediate in the flat cell group (27 +/- 6%), and lowest in the large round cell group (20 +/- 7%) (P < 0.001). Furthermore, the proliferative indices in the round cell group were inversely proportional to cell size. Therefore, (1) there is a sequential progression of cell morphology during periosteal chondrogenesis, (2) cell differentiation is arrested prior to terminal differentiation for some cells and not for others, and (3) proliferative activity is strongly related to cell morphology. This organ culture model provides us with opportunities to study the regulation of terminal chondrocyte differentiation and the control of cell proliferation. This will contribute to our understanding of cartilage repair, fracture healing and growth plate physiology.

Effects of cartilage-derived morphogenetic proteins and osteogenic protein-1 on osteochondrogenic differentiation of periosteum-derived cells

Localization studies and genetic evidence have implicated cartilage-derived morphogenetic proteins-1, -2 (CDMP-1 and CDMP-2), and osteogenic protein-1 (OP-1) in the osteochondrogenic differentiation of mesenchymal progenitor cells during embryonic development and in postnatal life. Based on their expression pattern and the evidence that periosteum contains mesenchymal cells in the cambium layer that can undergo bone and cartilage formation, we hypothesized that CDMPs and OP-1 may be involved in long bone development and fracture healing. To test this hypothesis, periosteum-derived cells from young calves were cultured as monolayers under serum-free conditions with and without the addition of recombinant CDMP-1, CDMP-2 and OP-1. Phenotypic analysis indicate that periosteum-derived cell populations prepared, expanded, and cultured under the conditions described below, constitutively express messenger RNAs for the bone markers osteocalcin, osteopontin and collagen type I, and the chondrogenic markers collagen type II and aggrecan as determined by RT-PCR. Moreover, histologic examinations showed positive staining for alcian blue and alkaline phosphatase (AP). Treatment of periosteum-derived cells with CDMPs and OP-1 resulted in a dose-dependent increase of cell proliferation; CDMP-2 was less active in this regard. Furthermore, all growth factors enhanced osteogenic differentiation as assessed by a time- and dose-dependent stimulation of AP activity and OP-1 increased messenger RNA expression for osteocalcin and collagen type I. We further examined the effects of CDMPs and OP-1 on chondrogenic differentiation of periosteum-derived cells. Both CDMPs and OP-1 stimulated (35)S-sulfate incorporation into newly synthesized macromolecules with OP-1 having a more pronounced stimulatory effect when compared with CDMP-1 and CDMP-2. Our results indicate that distinct members of the BMP-family increase the mitotic and metabolic activity of periosteum-derived cells. The enhancement of both the chondrogenic and osteogenic differentiation suggests that these growth factors might contribute to the local regulation of bone formation and fracture repair.

Technical considerations in periosteal grafting for osteochondral injuries

Periosteum has been used clinically for biologic resurfacing arthroplasty in small series of patients for almost two decades. The author's own experience with this technique in multiple joints, including the knee, has been similar to that already reported in the literature. Observations and considerations are discussed that might help avoid failure in future applications of this technique. Indications and surgical technique, including graft procurement and fixation, and postoperative treatment and possible complications are also described. The rationale for using periosteum as a chondrogenic tissue and the factors affecting its cartilage production are also outlined.

Localization of chondrocyte precursors in periosteum

OBJECTIVE

Periosteal chondrogenesis is relevant to cartilage repair and fracture healing. Periosteum contains two distinct layers: a thick, outer fibrous layer and a thin, inner cambium layer which is adjacent to the bone. Specific chondrocyte precursors are known to exist in periosteum but have not yet been identified. In this study, the location of the chondrocyte precursors in periosteum was determined.

METHOD

One hundred and twenty periosteal explants from 30 2-month-old NZ rabbits were cultured for up to 42 days. Histomorphological changes and spatio-temporal localization of Col. II mRNA and protein were analysed.

RESULTS

On day 7, chondrocyte differentiation appeared in the most juxtaosseous region in the cambium layer. Col. II mRNA and protein were also evident in the same region. By day 14, chondrocyte differentiation progressed further into the juxtaosseous cambium layer, as did Col. II mRNA and protein. With growth of the neocartilage, the cambium layer gradually diminished to the extent that by 21-28 days it was no longer evident. Cartilage growth was significant and followed an appositional pattern, growing away from the fibrous layer. The fibrous layer remained essentially unchanged from 0-42 days, without evidence of hypertrophy or atrophy. Col. II mRNA expression was never seen in the fibrous layer.

CONCLUSION

From these data, three conclusions can be drawn concerning chondrogenesis from periosteum: (1) the chondrocyte precursors are located in the cambium layer of periosteum; (2) chondrogenesis commences in the juxtaosseous area in the cambium layer and progresses from the juxtaosseous region to the juxtafibrous region of the cambium layer; (3) neocartilage growth is appositional, which displaces the fibrous layer away from the cartilage already formed, as new cartilage is formed between these two layers. These findings suggest that the least differentiated (stem or reserve) cells are located in the cambium layer furthest from the bone.

CLINICAL RELEVANCE

These findings show that the chondrocyte precursors are located in the cambium layer of periosteum. Preservation of this layer is essential for chondrogenesis. As neocartilage growth is appositional, away from the fibrous layer, it can be expected that the new cartilage deposited in and adjacent to a periosteal graft would be expected to be located on the side of the cambium layer, rather than on the side of the fibrous layer of the graft.

The importance of procedure specific training in harvesting periosteum for chondrogenesis

This study was performed to determine the influence of procedure specific and nonspecific training on the chondrogenic potential of explanted periosteum. Seven operators, with varying degrees of orthopaedic surgical experience and procedure specific training in periosteal harvesting, harvested 10 to 16 periosteal explants each from the proximal medial tibiae of 42 New Zealand White rabbits that were 2 months of age. The chondrogenic index assay involved culturing the explants in agarose suspension for 6 weeks, followed by computerized histomorphometric analysis. Chondrogenic indices (the average percent area of cartilage grown in the cultured explants) ranged from 12% to 81% and were influenced strongly by each operator's experience with the technique of periosteal harvesting. Average cartilage yields before practice were in the range of 12% +/- 4% for a technician and 44% +/- 6% for a surgeon, compared with 54% +/- 7% and 79% +/- 2%, respectively, after practice involving more than 300 explants each. Procedure specific experience (with the technique of periosteal harvesting) was more important than the academic qualifications or years of surgical experience in general. These data must be considered when planning or interpreting the results of studies involving periosteal explantation or grafting, or when periosteum serves as a source of mesenchymal stem cells.

Massive intraosseous ganglion of the talus: reconstruction of the articular surface of the ankle joint

We report on the outcome after autologous chondrocyte and spongiosal bone transplantation in a case of a massive intraosseous ganglion of the talus in a young patient. A 24-year-old man suffered from decreased ankle joint motion, recurrent swelling, and pain. Diagnostic evaluation by plain radiographs, computed tomography, and magnetic resonance imaging revealed cystic lesions in the head and the body of the talus with additional involvement of the cartilage surface. Operative treatment consisted primarily of an initial diagnostic arthroscopy, which established grade VI articular damage according to the arthroscopic classification of Bauer and Jackson. Pathological examination of intralesional biopsy tissue revealed the existence of an intraosseous ganglion. Additionally, healthy cartilage biopsy specimens were obtained and sent for chondrocyte extraction and cultivation with 60 mL of autologous serum. To retain the function of the ankle joint and to minimize the number of necessary operative interventions, 3 weeks after the initial arthroscopic operation, we performed a simultaneous curettage of the cystic lesion followed by autologous spongiosal bone and cultivated chondrocytes transplantation of the talus. Continuous passive motion was applied postoperatively and full weight bearing was allowed after 8 weeks. There were no complications. The clinical result after 18 months was excellent, with a fully functional, pain-free, and weight-bearing ankle joint. The postoperative evaluation score of Finsen (modified Weber score) of 2/6 = 0.3 showed an improvement comparison with the preoperative value of of 21/6 = 3.5 (0 = normal, 4 = pathologic). We encountered no complications postoperatively. Clinical success was achieved by this method of treatment on a patient too young to be treated through arthrodesis.

Neochondrogenesis in repair of full-thickness articular cartilage defects using free autogenous periosteal grafts in the rabbit. A follow-up in six months

OBJECTIVE

To analyse the repair of lesions of articular cartilage with periosteum-free implants and follow-up at 6 months.

DESIGN

Thirty-six New Zealand rabbits, 4-6 weeks old, were used. Full-thickness articular cartilage defects in the medial femoral condyle were created. Spontaneous evolution occurred in 18 animals; the other 18 animals were treated with a free autogenous periosteal tibial implant fixed with Tissucol. Animals were killed in groups of six at 8, 12 and 24 weeks. Macroscopic, histologic and histochemical results were evaluated and analysed statistically using the Mann-Whitney U-test.

RESULTS

The spontaneous evolution of the lesion did not lead to complete repair in any case. The periosteum-free implant provided complete repair of the lesion and statistically significant restoration of the articular surface.

CONCLUSIONS

In the rabbit, this study confirms the incomplete spontaneous repair of articular cartilage and the chondrogenic potential of tibial periosteum-free implants, with long-term maintenance of the macroscopic, histologic and histochemical characteristics of neo-cartilage. This raises the possibility of its use as an alternative method in the repair of circumscribed osteochondral lesions in young patients.

Human chondrocyte proliferation and matrix synthesis cultured in Atelocollagen gel

To evaluate the potential of Atelocollagen gel as a carrier for chondrocyte transplantation, histological and biochemical characteristics of the chondrocytes in gel culture were compared with those in conventional monolayer cultures. Articular chondrocytes from 20 patients were isolated by enzyme digestion, embedded in Atelocollagen gel, and cultured for up to 4 weeks. The effects on proliferation, morphological changes, and synthesis of proteoglycans were analyzed by cell counts, light and electron microscopy, and measurement of isomers of chondroitin sulfates. Chondrocytes embedded in the Atelocollagen gel gradually proliferated and produced chondroitin 6-sulfate, maintaining the chondrocyte phenotype for up to 4 weeks. In contrast, although monolayer chondrocytes increased in number, most could be characterized as being fibroblast-like cells with a reduced capability of producing chondroitin 6-sulfate. The results suggest that Atelocollagen gel permitted a gradual proliferation and matrix synthesis of chondrocytes and maintaining its phenotype. Atelocollagen gel represents an important carrier for the clinical application of cultured chondrocyte transplantation for repair of cartilage defects.

Two- to 9-year outcome after autologous chondrocyte transplantation of the knee

Autologous cultured chondrocyte transplantation was introduced in Sweden in 1987 for the treatment of large (1.5-12.0 cm2) full thickness chondral defects of the knee. The clinical, arthroscopic, and histologic results from the first 101 patients treated using this technique are reported in this study. Patients were assessed retrospectively using three types of endpoints: patient and physician derived clinical rating scales (five validated and two new); arthroscopic assessment of cartilage fill, integration, and surface hardness; and standard histochemical techniques. Ninety-four patients with 2- to 9-years followup were evaluable. Good to excellent clinical results were seen in individual groups as follows: isolated femoral condyle (92%), multiple lesions (67%), osteochondritis dissecans (89%), patella (65%), and femoral condyle with anterior cruciate ligament repair (75%). Arthroscopic findings in 53 evaluated patients showed good repair tissue fill, good adherence to underlying bone, seamless integration with adjacent cartilage, and hardness close to that of the adjacent tissue. Hypertrophic response of the periosteum or graft or both was identified in 26 arthroscopies; seven were symptomatic and resolved after arthroscopic trimming. Graft failure occurred in seven (four of the first 23 and three of the next 78) patients. Histologic analysis of 37 biopsy specimens showed a correlation between hyalinelike tissue (hyaline matrix staining positive for Type II collagen and lacking a fibrous component) and good to excellent clinical results. The good clinical outcomes of autologous chondrocyte transplantation in this study are encouraging, and clinical trials are being done to assess the outcomes versus traditional fibrocartilage repair techniques.

Long-term results of periosteal transplantation in osteochondritis dissecans of the knee

Between 1986 and 1991, a total of 18 patients (11 men and 7 women) with osteochondritis dissecans of the knee were treated with periosteal transplantation. Median patient age was 19 years (range: 16-45 years). Eight patients were reoperated up to 8 years postoperatively, due to reduced range of motion, synovitis, or formation of an exostosis in the transplanted area. Of 14 patients who were available for follow-up after 8 years (range: 5-10), 2 were completely pain free. Six patients had reduced range of motion, knee instability, or quadriceps muscle atrophy. The number of reoperations and the presence of continued knee pain in most patients does not justify the extensive procedure of periosteal transplantation.

Viability of periosteal tissue obtained postmortem

Periosteal autografts have the potential to regenerate articular cartilage defects, but this potential is limited by the patient's age. Allograft transplantation from a young donor to an older recipient might bypass this limitation. The effect of the time delay, between death and harvesting of a periosteal graft, on the chondrogenic potential of periosteum is important not only for transplantation but also for studies dealing with tissues retrieved postmortem (i.e., including the periosteal explant model). The purpose of this study was to investigate the chondrogenic potential of periosteum obtained postmortem and a possible beneficial effect of hypothermia. Thirty NZ white rabbits (2 months old) were sacrificed and stored at room temperature or 4 degrees C for 0, 4, 6, 8, 12, 16, 18, or 24 h. Periosteal explants were then obtained and a standard cartilage yield assay performed by culturing them for 6 weeks using the periosteal organ culture model as previous published. TGF-beta1 (10 ng/ml) was added for the first 14 days of culture. Histochemical analysis and quantitative collagen typing were performed. In the explants from the animals kept for 4 h at room temperature growth and chondrogenesis were dramatically reduced. Little or no chondrogenesis was seen in explants from rabbits maintained at room temperature after 4-8 h (or more) postmortem. Cooling the rabbits to 4 degrees C partially prevented this loss of viability and continued to do so for 24 h. Even storage at 4 degrees C did not eliminate the decrease in chondrogenic potential, though it did permit partial preservation of chondrogenic potential. If periosteum is to be used for allograft transplantation, or if it is used for experimental study, its viability must be assured. This is best accomplished by harvesting it immediately postmortem. Preservation techniques, cryopreservation, or hypothermia might be useful in preserving periosteal chondrogenic potential.

Articular cartilage regeneration using periosteum

Periosteum has chondrogenic potential that makes it possible to repair or regenerate cartilage in damaged joints. Whole periosteal explants also can be cultured in vitro for the purpose of studying chondrogenesis. This chondrogenic potential arises because the cambium layer of periosteum contains chondrocyte precursor cells that form cartilage during limb development and growth in utero, and does so once again during fracture healing. The advantages of whole tissue periosteal transplants for cartilage repair include the fact that this tissue meets the three primary requirements for tissue engineering: a source of cells, a scaffold for delivering and retaining them, and a source of local growth factors. Data from in vivo studies show that periosteum transplanted into osteochondral articular defects produce cartilage that can restore the articular cartilage and be replaced by bone in the subchondral region. This capacity is determined by surgical factors such as the orientation of the cambium layer, postoperative factors such as the use of continuous passive motion, and the age and maturity of the experimental animal. In vitro studies have shown that the chondrogenic potential of periosteal explants is determined by culture, donor conditions, and technical factors. Chondrogenesis is optimized by suspension of the explants in agarose under aerobic conditions, with supplementation of the media using fetal calf serum and growth factors, particularly transforming growth factor-beta 1. The role of physical factors currently is being investigated, but studies show that the mechanical environment is important. Donor factors that are important include the harvest site, the size of the periosteal explant, and most importantly the age of the donor. Periosteal chondrogenesis follows a specific time course of events, with proliferation preceding differentiation. The current challenge is to clarify the process of periosteal chondrogenesis and its regulation at the cellular and molecular levels, so that it can be controlled intelligently and optimized for the purpose of cartilage repair and regeneration.

Use of autologous grafts for reconstruction of osteochondral defects of the knee

This study reports on 13 patients (mean age: 31 years) with a femoral condyle defect >1.5 cm2 who underwent treatment with an osteochondral graft of the same size obtained from the superior aspect of the lateral condyle, preserving the patellar groove. Mean follow-up was 61.5 months (range: 13-141 months). Twelve results were rated clinically as satisfactory with patients able to resume their normal pre-injury level of activity, and 1 case was rated as poor. No patient reported any patellar problems. Radiographic and computed tomographic evaluation demonstrated good integration of the graft in the host bone. The results of this technique at relatively long-term follow-up are encouraging, with a high percentage of subjective satisfaction. This technique appears to be reliable and provides a valid solution for treatment of wide cartilage defects when other techniques are too complex or inadequate.

Reduction of hemorrhage after knee arthroplasty using cryo-based fibrin sealant

The spray application of cryo-based fibrin sealant was evaluated for reducing hemorrhage in a complex, anticoagulated canine model of knee joint arthroplasty. Nine heparinized dogs underwent bilateral knee arthroplasty under tourniquet control with each animal having 3 mL of fibrin sealant sprayed onto one joint and the other joint serving as control. The fibrin sealant significantly reduced total and incremental bleeding as compared to the control side (P < .05). In addition, the hemostatic effectiveness of the fibrin sealant increased as bleeding propensity increased (P < .05). This study suggests that fibrin sealant may reduce bleeding from orthopedic joint replacement in human patients undergoing routine operations as well as those receiving forms of anticoagulation to reduce the incidence of deep venous thrombosis and pulmonary embolus.

Effects of hyaluronan on periosteal grafts for large full-thickness defects in rabbit articular cartilage

We studied the effects of hyaluronan (HA) on chondrogenesis in periosteal grafts in rabbit knees to elucidate the effects of this agent in the repair of articular cartilage. Large full-thickness defects of the articular cartilage were created in the anteromedial part of the femoral articular surface of bilateral knee joints. Periosteal grafts were then harvested and sutured onto the defects. HA was injected in the right knee immediately after the operation and then once a week for 4 weeks (HA group). The same volume of saline was injected in the left knee in the control group. The animals were killed 2, 5, 8, and 12 weeks after the operation. Macroscopic and histological findings of the regenerated tissue were evaluated with a semiquantitative histological grading system. The total histological scores of the HA group were better than those in the control group at each time examination point. At 12 weeks, in particular, the scores for surface regularity and integration to adjacent articular cartilage were significantly better in the HA group than in the control group (P < 0.05). No significant differences were observed between the two groups in regard to the area healed (%). HA may have beneficial effects on the repair of large full-thickness defects of the articular cartilage with autologous periosteal grafts.

Osteochondritis dissecans of the femoral condyle treated with periosteal transplantation. Poor outcome in 14 patients followed for 6-9 years

We evaluated 14 consecutive periosteal transplantations to treat osteochondritis dissecans lesions of the femoral condyle. 1 year postoperatively, 9 knees were pain-free, but with 6-9 years follow-up, only 2 knees were pain-free. Formation of hyaline-like cartilage, assessed in 12 knees, was documented in 1 patients and assessed as possible in 1 more, but in 10 patients the tissue formed in the defects was not or probably not hyaline cartilage. 6 knees had developed arthrosis.

Effects of basic fibroblast growth factor on proliferation and phenotype expression of chondrocytes embedded in collagen gel

1. Whether basic fibroblast growth factor (bFGF) can stimulate proliferation and synthesis of chondroitin sulfate of chondrocytes in gel culture while maintaining the phenotype was studied. 2. At 3 weeks in culture, the cell number in 1.0 ng/ml (18.5+/-2.1 x 10(5)) and 10.0 ng/ml of the bFGF group (15.3+/-1.9 x 10(5)) was significantly larger than that in 0 ng/ml (12.3+/-2.1 x 10(5)), 0.1 ng/ ml (11.7+/-2.2 x 10(5)) and 100.0 ng/ml of the bFGF group (9.8+/-2.3 x 10(5)). 3. All doses of bFGF used in this study suppressed synthesis of chondroitin 6-sulfate. 4. Chondrocyte phenotype in gel culture was maintained for 4 weeks even with stimulation of bFGF.