Cryopreservation with dimethyl sulfoxide sustains partially the biological function of osteochondral tissue

Cryopreservation of tissues and organs: present, bottlenecks, and future

Tissue and organ transplantation continues to be an effective measure for saving the lives of certain critically ill patients. The organ preservation methods that are commonly utilized in clinical practice are presently only capable of achieving short-term storage, which is insufficient for meeting the demand for organ transplantation. Ultra-low temperature storage techniques have garnered significant attention due to their capacity for achieving long-term, high-quality preservation of tissues and organs. However, the experience of cryopreserving cells cannot be readily extrapolated to the cryopreservation of complex tissues and organs, and the latter still confronts numerous challenges in its clinical application. This article summarizes the current research progress in the cryogenic preservation of tissues and organs, discusses the limitations of existing studies and the main obstacles facing the cryopreservation of complex tissues and organs, and finally introduces potential directions for future research efforts.

Ciliary Neurotrophic Factor (CNTF) and Its Receptors Signal Regulate Cementoblasts Apoptosis through a Mechanism of ERK1/2 and Caspases Signaling

Ciliary neurotrophic factor (CNTF) was identified as a survival factor in various types of peripheral and central neurons, glia and non-neural cells. At present, there is no available data on the expression and localization of CNTF-receptors in cementoblasts as well as on the role of exogenous CNTF on this cell line. The purpose of this study was to determine if cementoblasts express CNTF-receptors and analyze the mechanism of its apoptotic regulation effects on cementoblasts. OCCM-30 cementoblasts were cultivated and stimulated kinetically using CNTF protein (NBP2-35168, Novus Biologicals). Quantified transcriptional (RT-qPCR) and translational (WB) products of CNTFRα, IL-6Rα (CD126), LIFR, p-GP130, GP130, p-ERK1/2, ERK1/2, Caspase-8, -9, -3 and cleaved-caspase-3 were evaluated. Immunofluorescence (IF) staining was applied to visualize the localization of the CNTF-receptors within cells. The apoptosis ratio was measured with an Annexin-V FITC/PI kit. The ERK1/2 antagonist (FR180204, Calbiochem) was added for further investigation by flow cytometry analysis. The CNTF-receptor complex (CNTFRα, LIFR, GP130) was functionally up-regulated in cementoblasts while cultivated with exogenous CNTF. CNTF significantly attenuated cell viability and proliferation for long-term stimulation. Flow cytometry analysis shows that CNTF enhanced the apoptosis after prolonged duration. However, after only a short-term period, CNTF halts the apoptosis of cementoblasts. Further studies revealed that CNTF activated phosphorylated GP130 and the anti-apoptotic molecule ERK1/2 signaling to participate in the regulation of the apoptosis ratio of cementoblasts. In conclusion, CNTF elicited the cellular functions through a notable induction of its receptor complex in cementoblasts. CNTF has an inhibitory effect on the cementoblast homeostasis. These data also elucidate a cellular mechanism for an exogenous CNTF-triggered apoptosis regulation in a mechanism of ERK1/2 and caspase signaling and provides insight into the complex cellular responses induced by CNTF in cementoblasts.

Clinical Application Status of Articular Cartilage Regeneration Techniques: Tissue-Engineered Cartilage Brings New Hope

Hyaline articular cartilage lacks blood vessels, lymphatics, and nerves and is characterised by limited self-repair ability following injury. Traditional techniques of articular cartilage repair and regeneration all have certain limitations. The development of tissue engineering technology has brought hope to the regeneration of articular cartilage. The strategies of tissue-engineered articular cartilage can be divided into three types: “cell-scaffold construct,” cell-free, and scaffold-free. In “cell-scaffold construct” strategies, seed cells can be autologous chondrocytes or stem. Among them, some commercial products with autologous chondrocytes as seed cells, such as BioSeed®-C and CaReS®, have been put on the market and some products are undergoing clinical trials, such as NOVOCART® 3D. The stem cells are mainly pluripotent stem cells and mesenchymal stem cells from different sources. Cell-free strategies that indirectly utilize the repair and regeneration potential of stem cells have also been used in clinical settings, such as TruFit and MaioRegen. Finally, the scaffold-free strategy is also a new development direction, and the short-term repair results of related products, such as NOVOCART® 3D, are encouraging. In this paper, the commonly used techniques of articular cartilage regeneration in surgery are reviewed. By studying different strategies and different seed cells, the clinical application status of tissue-engineered articular cartilage is described in detail.

Cryopreservation of tendon tissue using dimethyl sulfoxide combines conserved cell vitality with maintained biomechanical features

Biomechanical research on tendon tissue evaluating new treatment strategies to frequently occurring clinical problems regarding tendon degeneration or trauma is of expanding scientific interest. In this context, storing tendon tissue deep-frozen is common practice to collect tissue and analyze it under equal conditions. The commonly used freezing medium, phosphate buffered saline, is known to damage cells and extracellular matrix in frozen state. Dimethyl sulfoxide, however, which is used for deep-frozen storage of cells in cell culture preserves cell vitality and reduces damage to the extracellular matrix during freezing. In our study, Achilles tendons of 26 male C57/Bl6 mice were randomized in five groups. Tendons were deep frozen in dimethyl sulfoxide or saline undergoing one or four freeze-thaw-cycles and compared to an unfrozen control group analyzing biomechanical properties, cell viability and collagenous structure. In electron microscopy, collagen fibrils of tendons frozen in saline appeared more irregular in shape, while dimethyl sulfoxide preserved the collagenous structure during freezing. In addition, treatment with dimethyl sulfoxide preserved cell viability visualized with an MTT-Assay, while tendons frozen in saline showed no remaining metabolic activity, indicating total destruction of cells during freezing. The biomechanical results revealed no differences between tendons frozen once in saline or dimethyl sulfoxide. However, tendons frozen four times in saline showed a significantly higher Young’s modulus over all strain rates compared to unfrozen tendons. In conclusion, dimethyl sulfoxide preserves the vitality of tendon resident cells and protects the collagenous superstructure during the freezing process resulting in maintained biomechanical properties of the tendon.

Effect of Bisphosphonate Pretreatment on Fresh Osteochondral Allografts: Analysis of In Vitro Graft Structure and In Vivo Osseous Incorporation

Fresh allograft transplantation of osteochondral defects restores functional articular cartilage and subchondral bone; however, rapid loss of chondrocyte viability during storage and osteoclast-mediated bone resorption at the graft-host interface after transplantation negatively impact outcomes. The authors present a pilot study evaluating the in vitro and in vivo impact of augmenting storage media with bisphosphonates. Forty cylindrical osteochondral cores were harvested from femoral condyles of human cadaveric specimens and immersed in either standard storage media or storage media supplemented with nitrogenated or non-nitrogenated bisphosphonates. Maintenance of graft structure and chondrocyte viability were assessed at 3 time points. A miniature swine trochlear defect model was used to evaluate the influence of bisphosphonate-augmented storage media on in vivo incorporation of fresh osteochondral tissue, which was quantified via μCT and decalcified histology. In the in vitro study, Safranin-O/Fast Green staining showed that both low- and high-dose nitrogenated-treated grafts retained chondrocyte viability and cartilage matrix for up to 43 days of storage. Allografts stored in nitrogenated-augmented storage media showed both μCT and histologic evidence of enhanced in vivo bony and cartilaginous incorporation in the miniature swine trochlear defect model. Several preclinical studies have shown the potential for enhanced storage of fresh osteochondral allografts via additions of relatively common drugs and biomolecules. This study showed that supplementing standard storage media with nitrogenated bisphosphonates may improve maintenance of chondrocyte viability and graft structure during cold storage as well as enhance in vivo osseous and cartilaginous incorporation of the graft. [Orthopedics: 2018; 41(3):e376-e382.].

Cryopreservation of Autologous Cranial Bone Flaps for Cranioplasty: A Large Sample Retrospective Study

OBJECTIVE

To clarify the clinical outcomes of cranioplasty with cryopreserved bone flaps and identify risk factors related to bone flap infection and resorption after cranioplasty with cryopreserved bone flaps.

METHODS

A total of 946 patients (989 bone flaps) underwent decompressive craniectomy and delayed cranioplasty via the use of cryopreserved autogenous cranial bone flaps. Cranial bone flaps were removed during the initial craniectomy and reserved in liquid nitrogen (-196°C) with dimethyl sulfoxide as a cryoprotectant. Cranioplasty subsequently was performed once the brain injury had healed. Data regarding complications and clinical outcomes were recorded and the potential risk factors were analyzed.

RESULTS

Data from 960 flaps were available for analysis. The overall complication rate was 15.83% (152 of 960). Bone resorption occurred in 42 flaps in 37 patients (4.38%). The bone flaps resorption rate was greater in patients ≤18 years than in patients >18 years (9.38% vs. 3.61%, P < 0.05). Cryopreservation for more than 365 days tended to result in a greater bone resorption rate (6.88% vs. 2.92%, P < 0.01). Skull bone grafts infection occurred in 39 flaps in 34 patients (4.06%). The bone graft infection rate was greater in emergency craniectomy cases (8.81% vs. 2.59%, P < 0.01) and in patients with diabetes (10.53% vs. 3.07%, P < 0.01).

CONCLUSIONS

Cryopreservation of autologous cranial bone flaps is safe and effective for cranioplasty. Cranioplasty with cryopreserved autologous cranial bone flaps should be performed no more than 1 year after craniectomy. Emergency craniectomy and patients with diabetes require special attention.

Biologic and clinical aspects of integration of different bone substitutes in oral surgery: a literature review

Many bone substitutes have been proposed for bone regeneration, and researchers have focused on the interactions occurring between grafts and host tissue, as the biologic response of host tissue is related to the origin of the biomaterial. Bone substitutes used in oral and maxillofacial surgery could be categorized according to their biologic origin and source as autologous bone graft when obtained from the same individual receiving the graft; homologous bone graft, or allograft, when harvested from an individual other than the one receiving the graft; animal-derived heterologous bone graft, or xenograft, when derived from a species other than human; and alloplastic graft, made of bone substitute of synthetic origin. The aim of this review is to describe the most commonly used bone substitutes, according to their origin, and to focus on the biologic events that ultimately lead to the integration of a biomaterial with the host tissue.

Histological evaluation of fresh frozen bone integration at different experimental times

The aim of this work was to investigate, through histological evaluation, the in vivo behavior of fresh frozen bone (FFB) used as particulate bone substitute in intraoral regenerative procedures. A total of 10 patients (group 1) received particulate FFB graft for bone regeneration in postextractive sockets, and 10 (group 2) underwent maxillary sinus augmentation by using the same bone substitute as filling. Fresh frozen bone was supplied from the Tissue Bank of the Veneto Region, Treviso Section.Healing was uneventful for all the patients and was monitored by periodical radiographs. Patients were scheduled for implant insertion according to the radiographic aspect. However, the mean healing time for group 1 was 45 days, whereas for group 2 patients, it was 100 days. At the moment of implant insertion, bone specimens were collected at the site of implant placement, from both groups and processed for histological analysis.Histological analysis after hematoxylin-eosin staining obtained from group 1 patients showed the presence of newly formed bone tissue, still well distinguishable from the grafted bone substitute. In samples from group 2 patients, a better integration could be recognized associated with active bone remodeling phenomena.These results showed a good integration of the considered FFB graft within the host tissue both at 45 and 100 days after grafting, displaying this biomaterial as suitable for preimplant regenerative procedures.

Chondrocytes within osteochondral grafts are more resistant than osteoblasts to tissue culture at 37°C

It is proposed that an ideal osteochondral allograft for cartilage repair consists of a devitalized bone but functional cartilage. The different modes of nutrient supply in vivo for bone (vascular support) and cartilage (diffusion) suggest that a modulation of storage conditions could differentially affect the respective cells, resulting in the proposed allograft. For this purpose, osteochondral tissues from porcine humeral heads were either cultured at 37°C for up to 24 hr or stored at 4°C for 24 hr, the temperature at which osteochondral allografts are routinely stored. Functionality of the cells was assessed by in situ hybridization for transcripts encoding collagen types I and II. At 37°C, a time-dependent significant reduction of the bone surface covered with functional cells was observed with only 5% ± 5% coverage left at 24 hr compared with 41% ± 10% at 0 hr. Similarly, cartilage area containing functional cells was significantly reduced from 84% ± 7% at 0 hr to 70% ± 3% after 24 hr. After 24 hr at 4°C, a significantly reduced amount of functional cells covering bone surfaces was observed (27% ± 5%) but not of cells within the cartilage (79% ± 8%). In the applied experimental setup, bone cells were more affected by tissue culture at 37°C than cartilage cells. Even though chondrocytes appear to be more sensitive to 37°C than to 4°C, the substantially reduced amount of functional bone cells at 37°C warrants further investigation of whether a preincubation of osteochondral allografts at 37°C--prior to regular storage at 4°C--might result in an optimized osteochondral allograft with devitalized bone but viable cartilage.

Maintenance of phenotype and function of cryopreserved bone-derived cells

The emerging fields of tissue engineering and regenerative medicine require large numbers of cells for therapy. Although the properties of cells obtained from a variety of fresh tissues have been delineated, the knowledge regarding cryopreserved grafts-derived cells remains elusive. Previous studies have shown that living cells could be isolated from cryopreserved bone grafts. However, whether cryopreserved bone-derived cells can be applied in regenerative medicine is largely unknown. The present study was to evaluate the potential application of cryopreserved grafts-derived cells for tissue regeneration. We showed that cells derived from cryopreserved bone grafts could maintain good proliferation activity and osteogenic phenotype. The biological phenotype of these cells could be well preserved. The transplantation of cryopreserved bone-derived cells on scaffold could promote new bone formation in nude mice and enhance the osteointegration for dental implants in canine, which confirmed their osteogenic capacity, and showed that cells derived from cryopreserved bone were comparable to that of fresh bone in terms of the ability to promote osteogenesis in vivo. This work demonstrates that cryopreserved bone grafts may represent a novel, accessible source of cells for tissue regeneration therapy, and the results of our study may also stimulate the development of other cryopreservation techniques in basic and clinical studies.

DMSO regulates osteoclast development in vitro

Dimethyl sulfoxide (DMSO) is routinely used in the laboratory as a solvent and vehicle for organic molecules. Although it has been used in previous studies involving myeloid cells and macrophages, we are unaware of data demonstrating the effects of DMSO alone on osteoclast development. Recently, we were using DMSO as a vehicle and included a non-vehicle control. Surprisingly, we observed a marked change in osteoclast development, and therefore designed this study to examine the effects of DMSO on osteoclast development. Osteoclasts were generated from two sources: bone marrow macrophages and an osteoclast progenitor cell line. Cells were cultured with DMSO for various durations and at differing concentrations and mature, multinucleated (>3 nuclei) TRAP(+) cells were assessed in terms of cell number, cell surface area, and number of nuclei/cell. Osteoclast surface area increased in 5 μM DMSO to a mean of 156,422 pixels from a mean of 38,510 pixels in control culture, and subsequently decreased in 10 μM DMSO to a mean of 18,994 pixels. With serial addition of DMSO over 5 d, a significant increase in mean surface area, and number of nuclei/cell was also observed, while the opposite was true when DMSO was serially removed from culture. These findings show that DMSO exerts a marked effect on osteoclast differentiation. Since many investigators use DMSO to solubilize compounds for treatment of osteoclasts, caution is warranted as altering DMSO concentrations may have a profound effect on the final data, especially if osteoclast differentiation is being assessed.

Surgical hip dislocation for osteochondral transplantation as a salvage procedure for a femoral head impaction fracture

Obturator anterior hip dislocation is very rare. Poor results are described in patients with additional large transchondral fractures and treatment of these injuries remains challenging. Appropriate treatment recommendations are missing in the literature. This case report introduces surgical hip dislocation for osteochondral autograft transplantation with graft harvest from the nonweightbearing area of the head-neck junction as a salvage procedure in a large femoral head defect. We report the treatment and outcome of a 48-year-old man who sustained an anterior dislocation of the left hip after a motorcycle accident. After initial closed reduction in the emergency room, imaging analysis revealed a large osteochondral defect of the femoral head within the weightbearing area (10 × 20 mm, depth: 5 mm). The hip was exposed with a surgical hip dislocation using a trochanteric osteotomy. An osteochondral autograft was harvested from a nonweightbearing area of the femoral head and transferred into the defect. The patient was prospectively examined clinically and radiologically. Two years postoperatively, the patient was free of pain and complaints. The function of the injured hip was comparable to that of the contralateral, healthy hip and showed satisfying radiologic results. Surgical hip dislocation with a trochanteric flip osteotomy is a simple, one-step technique that allows full inspection of the hip to treat osteochondral femoral defects by osteochondral transplantation. The presented technique, used as a salvage procedure in a large femoral head defect, yielded good clinical and satisfying radiologic outcomes at the midterm.

Histopathology of Cryopreserved Bone Allo- and Isografts: Pretreatment with Dimethyl Sulfoxide

Partial graft cell survival and enhanced graft revascularization have suggested fast freezing using the cryoprotective substance dimethyl sulfoxide (DMSO) as a promising means to improve the biologic function and immune tolerance of allograft bone. This study determines the presence of osteoblasts (cola(1)(I) mRNA), osteoclasts (TRAP), and cytotoxic T cells (CTLs; GrA mRNA) within pretreated bone grafts 12 days after transplantation. The grafts were transplanted either as isografts, allografts, or allografts in presensitized recipients. In fresh isografts, serving as control, well-formed blood vessels and the highest numbers of viable osteoblasts and osteoclasts were found. In fresh allografts, blood vessels were observed within the marrow cavity and the bone was partially covered by osteoblasts and osteoclasts accompanied by CTLs. In DMSO-pretreated frozen allografts, blood vessels together with osteoblasts were observed in three of five, but in none of five grafts frozen without DMSO. However, infiltration with CTLs was higher in DMSO-pretreated frozen allografts when compared to grafts frozen without DMSO. In presensitized allograft recipients, independent of the pretreatment, in none of the grafts were either blood vessels or osteoblasts found. Thus, fast cryopreservation of bone using DMSO improves vascularization and expression of cola(1)(I) mRNA (osteoblasts) after allografting when compared to cryopreservation alone, potentially improving graft incorporation. As these grafts were still invaded by CTLs, the long-term effect of DMSO pretreatment needs to be defined.

Differential response of porcine osteoblasts and chondrocytes in cell or tissue culture after 5-aminolevulinic acid-based photodynamic therapy

OBJECTIVE

Outcome in osteochondral allografting is limited by the immunological incompatibility of the grafted tissue. Based on a resistance of chondrocytes to photodynamic therapy in cell culture it is proposed that 5-aminolevulinic acid-based photodynamic therapy (5-ALA-PDT) might be used to inactivate bone while maintaining viability of chondrocytes and thus immunomodulate bone selectively.

METHODS

Chondrocytes and osteoblasts from porcine humeral heads were either isolated (cell culture) or treated in situ (tissue culture). To quantify cytotoxic effects of 5-ALA-PDT (0-20 J/cm(2), 100 mW/cm(2)) an (3-(4,5-dimethylthiazol-2-yl)-2,5-di-phenyltetrazolium bromide) (MTT)-assay was used in cell culture and in situ hybridization in tissue culture to assess metabolic active cells (functional osteoblasts: col alpha(1)(I) mRNA, functional chondrocytes: col alpha(1)(II) mRNA).

RESULTS

In cell culture, survival after 5-ALA-PDT was significantly higher for chondrocytes (5 J/cm(2): 87+/-12% compared to untreated cells) than for osteoblasts (5J/cm(2): 12+/-11%). In tissue culture, the percentage of functional chondrocytes in cartilage showed a decrease after 5-ALA-PDT (direct fixation: 92+/-2%, 20 J/cm(2): 35+/-15%; P<0.0001). A significant decrease in the percentage of bone surfaces covered by functional osteoblasts was observed in freshly harvested (31+/-3%) compared to untreated tissues maintained in culture (11+/-4%, P<0.0001), with no further decrease after 5-ALA-PDT.

CONCLUSION

Chondrocytes were more resistant to 5-ALA-PDT than osteoblasts in cell culture, while in tissue culture a loss of functional chondrocytes was observed after 5-ALA-PDT. Since osteoblasts - but not chondrocytes - were sensitive to the tissue culture conditions, devitalized bone with functional cartilage might already be achieved by applying specific tissue culture conditions even without 5-ALA-PDT.

Clinical, histologic, and histomorphometric analyses of regenerated bone in maxillary sinus augmentation using fresh frozen human bone allografts

BACKGROUND

The purpose of the present study was the clinical and the histologic evaluation of fresh frozen human bone (FFB) allografts used for maxillary sinus-augmentation procedures.

METHODS

Ten subjects were treated with maxillary sinus augmentations using FFB. Radiologic measurements were recorded on computed tomography scans preoperatively and 5 months after the sinus surgeries. At 5 months, during implant placement, 10 core biopsies were retrieved and processed for histomorphometric evaluation under light microscopy (LM). Clinical and histomorphometric measurements are presented as mean +/- SD.

RESULTS

At baseline, the height of the alveolar ridge measured 4.3 +/- 1.3 mm (mean); after augmentation procedures, at implant positioning, it had a mean height of 16.0 +/- 1.8 mm. All 22 dental implants were clinically healthy after 5 months. LM showed that most of the specimens presented newly formed bone that was completely integrated with preexisting bone. The interface areas between new and old bone were not discernible. Woven bone was present in some areas of the biopsies; however, in the majority of the examined regions, there was mature osseous tissue presenting features of trabecular bone. There was no evidence of an acute inflammatory infiltrate. Histomorphometry revealed that the percentage of bone was 48.15% +/- 14.32%, whereas marrow spaces occupied the rest of the area.

CONCLUSION

FFB is a biocompatible material that can be successfully used for maxillary sinus augmentations without interfering with normal reparative bone processes.

The effects of prolonged deep freezing on the biomechanical properties of osteochondral allografts

Musculo-skeletal allografts sterilized and deep frozen are among the most common human tissue to be preserved and utilized in modern medicine. The effects of a long deep freezing period on cortical bone has already been evaluated and found to be insignificant. However, there are no reports about the influences of a protracted deep freezing period on osteochondral allografts. One hundred osteochondral cylinders were taken from a fresh specimen and humeral heads of 1 year, 2 years, 3 years and 4 year old bones. Twenty chips from each period, with a minimum of 3 chips per humeral head. Each was mechanically tested by 3 point compression. The fresh osteochondral allografts were significantly mechanically better than the deep frozen osteochondral allografts. There was no statistical significant time dependent difference between the deep frozen groups in relation to the freezing period. Therefore, we conclude that, from the mechanical point of view deep freezing of osteochondral allografts over a period of 4 years, is safe without further deterioration of the biomechanical properties of the osteochondral allografts.

Hypoxic expansion promotes the chondrogenic potential of articular chondrocytes

For cell-based cartilage repair strategies, an ex vivo expansion phase is required to obtain sufficient numbers of cells needed for therapy. Although recent reports demonstrated the central role of oxygen for the function and differentiation of chondrocytes, a beneficial effect of low oxygen concentrations during the expansion of the cells to further improve their chondrogenic capacity has not been investigated.Therefore, freshly harvested bovine articular chondrocytes were grown in two-dimensional monolayer cultures at 1.5% and 21% O2 and redifferentiation was subsequently induced in three-dimensional micromass cultures at 1.5%, 5%, and 21% O2. Cells expanded at 1.5% O2 were characterized by low citrate synthase (aerobic energy metabolism)--and high LDH (anaerobic energy metabolism-activities,suggesting an anaerobic energy metabolism. Collagen type II mRNA was twofold higher in cells expanded at 1.5% as compared to expansion at 21% O2. Micromass cultures grown at 21% O2 showed up to a twofold increase in the tissue content of glycosaminoglycans when formed with cells expanded at 1.5% instead of 21% O2. However, no differences in the levels of transcripts and in the staining for collagen type II protein were observed in these micromass cultures. Hypoxia (1.5% and 5% O2) applied during micromass cultures gave rise to tissues with low contents of glycosaminoglycans only. In vivo, the chondrocytes are adapted to a hypoxic environment. Taking this into account, by applying 1.5% O2 in the expansion phase in the course of cell-based cartilage repair strategies, may result in a repair tissue with higher quality by increasing the content of glycosaminoglycans.

Prospective evaluation of prolonged fresh osteochondral allograft transplantation of the femoral condyle: minimum 2-year follow-up

BACKGROUND

Focal articular cartilage lesions of the knee in young patients present a therapeutic challenge. Little information is available pertaining to the results after implantation of prolonged fresh grafts.

HYPOTHESIS

Prolonged fresh osteochondral allografts present a viable option for treating large full-thickness articular cartilage lesions.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

This study presents the results of 25 consecutive patients who underwent prolonged fresh osteochondral allograft transplantation for defects in the femoral condyle. The average patient age was 35 years (range, 17-49 years). The average length of follow-up was 35 months (range, 24-67 months). Prospective data were collected using several subjective scoring systems, as well as objective and radiographic assessments.

RESULTS

Statistically significant improvements (P < .05) were seen for the Lysholm (39 to 67), International Knee Documentation Committee scores (29 to 58), all 5 components of the Knee injury and Osteoarthritis Outcome Score (Pain, 43 to 73; Other Disease-Specific Symptoms, 46 to 64; Activities of Daily Living Function, 56 to 83; Sport and Recreation Function, 18 to 46; Knee-Related Quality of Life, 22 to 50), and the Short Form-12 physical component score (36 to 40). Overall, patients reported 84% (range, 25% to 100%) satisfaction with their results and believed that the knee functioned at 79% (range, 35% to 100%) of their unaffected knee. Radiographically, 22 of the grafts (88%) were incorporated into host bone.

CONCLUSION

Fresh osteochondral allograft transplantation is an acceptable intermediate procedure for treatment of localized osteochondral defects of the femur. At 2-year follow-up, it is well incorporated and offered consistent improvements in pain and function.

CLINICAL RELEVANCE

Prolonged fresh allograft transplantation is a safe and effective technique for addressing symptomatic osteoarticular lesions in the knees of young patients.

Molecular study of the diffusional process of DMSO in double lipid bilayers

As a way to quantify the diffusion process of molecular compounds through biological membranes, we investigated in this study the dynamics of DMSO through an 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine (DPPC) bilayer system. To properly account for the diffusion of DMSO due to a concentration gradient, a double DPPC bilayer was setup for our simulations. In such configuration, the aqueous phases can be explicitly associated with the extra and intracellular domains of the membrane, which is seldom the case in studies of single lipid bilayer due to the periodicity imposed by the simulations. DMSO molecules were initially contained in one of the aqueous phases (extracellular region) at a concentration of 5 wt.%. Molecular dynamics simulation was performed in this system for 95 ns at 350 K and 1 bar. The simulations showed that although many DMSO molecules penetrated the lipid bilayer, only about 10% of them crossed the bilayer to reach the other aqueous phase corresponding to the intracellular region of the membrane. The simulation time considered was insufficient to reach equilibrium of the DMSO concentration between the aqueous phases. However, the simulations provided sufficient information to estimate parameters to apply Fick's Law to model the diffusion process of the system. Using this model, we predicted that for the time considered in our simulation, the concentration of DMSO in the intracellular domain should have been about half of the actual value obtained. The model also predicted that equilibrium of the DMSO concentration in the system would be reached after about 2000 ns, approximately 20 times longer than the performed simulation.

Cryopreservation of human fetal islets by vitrification

AIM: To evaluate the efficiency of cryopre-servation of human fetal islets using vitrification as a potential feasible approach to islets bank establishment.

METHODS: Pancreatic islets of dead foetus aged 18 to 28 weeks induced by water bag were harvest by collagenase digestion. Islets were cultured and cryopreserved by computer programmed slow freezing and vitrification, respectively. The morphology and ultrastructure of thawed islets were studied in the two groups. Function of thawed islets was assessed by glucose-stimulated release of insulin, which was measured by radioimmunoassay. mRNA of insulin gene of the thawed islets was detected by using reversed-transcription polymerase chain reaction.

RESULTS: Morphologic studies of thawed islets demonstrated that both cryopreservation methods retained the integrity of islets. Secretary granule and mitochondria in beta cells were abundant. Analysis of basal insulin secretion and the stimulation release in the two groups showed no significantly difference from pro-cryopreservation (P>0.05 in both).

CONCLUSION: The integrity and function of islets can be retained by vitrification. The efficiency of vitrification in cryopreservation of human fetal islets is similar to the computer programmed slow freezing. Vitrification is a feasible and convenient approach as a substitution of the programmed slow freezing in the islets cell banking.

Osteoprogenitor viability in cell populations isolated from rat femora is not affected by 24 h storage at 4 degrees C

This study was initiated to determine whether partially dissected bones of rats could be refrigerated for 24 h in saline without losing viability of progenitor cells, specifically osteoprogenitors. This is directly applicable to studies involving bone tissue requiring overnight shipment, for example, studies involving space flown animals, grafting experiments, or transplantation. We evaluated cell populations isolated from the proximal femur of 6-week-old male Fisher 344 rats. Explants from the left femur were prepared and placed into culture immediately following dissection, while the right femur was cleaned, fragmented, and stored in saline at 4 degrees C for 24 h, after which explant cultures were initiated. After 11 days of explant culture, cells were collected from outgrowths, counted, and plated to initiate experiments. Plated cells were grown for either 15 or 21 days. To determine if storage affected the total number of colony forming progenitors, alkaline phosphatase positive colonies, or the number of osteoprogenitors, were counted. There was no significant difference in any of the types of colony forming units examined between cell populations derived from freshly prepared samples or those stored for 24 h, indicating that storage at 4 degrees C of bone tissue for 24 h in saline does not affect the osteogenic potential or the number of osteoprogenitors of the cell populations isolated.