Osteogenic progenitors in bone marrow aspirates from smokers and nonsmokers

Early efficacy evaluation of mesenchymal stromal cells (MSC) combined to biomaterials to treat long bone non-unions

BACKGROUND AND STUDY AIM

Advanced therapy medicinal products (ATMP) frequently lack of clinical data on efficacy to substantiate a future clinical use. This study aims to evaluate the efficacy to heal long bone delayed unions and non-unions, as secondary objective of the EudraCT 2011-005441-13 clinical trial, through clinical and radiological bone consolidation at 3, 6 and 12 months of follow-up, with subgroup analysis of affected bone, gender, tobacco use, and time since the original fracture.

PATIENTS AND METHODS

Twenty-eight patients were recruited and surgically treated with autologous bone marrow derived mesenchymal stromal cells expanded under Good Manufacturing Practices, combined to bioceramics in the surgical room before implantation. Mean age was 39 ± 13 years, 57% were males, and mean Body Mass Index 27 ± 7. Thirteen (46%) were active smokers. There were 11 femoral, 4 humeral, and 13 tibial non-unions. Initial fracture occurred at a mean ± SD of 27.9 ± 31.2 months before recruitment. Efficacy results were expressed by clinical consolidation (no or mild pain if values under 30 in VAS scale), and by radiological consolidation with a REBORNE score over 11/16 points (value of or above 0.6875). Means were statistically compared and mixed models for repeated measurements estimated the mean and confidence intervals (95%) of the REBORNE Bone Healing scale. Clinical and radiological consolidation were analyzed in the subgroups with Spearman correlation tests (adjusted by Bonferroni).

RESULTS

Clinical consolidation was earlier confirmed, while radiological consolidation at 3 months was 25.0% (7/28 cases), at 6 months 67.8% (19/28 cases), and at 12 months, 92.8% (26/28 cases including the drop-out extrapolation of two failures). Bone biopsies confirmed bone formation surrounding the bioceramic granules. All locations showed similar consolidation, although this was delayed in tibial non-unions. No significant gender difference was found in 12-month consolidation (95% confidence). Higher consolidation scale values were seen in non-smoking patients at 6 (p = 0.012, t-test) and 12 months (p = 0.011, t-test). Longer time elapsed after the initial fracture did not preclude the occurrence of consolidation.

CONCLUSION

Bone consolidation was efficaciously obtained with the studied expanded hBM-MSCs combined to biomaterials, by clinical and radiological evaluation, and confirmed by bone biopsies, with lower consolidation scores in smokers.

How stem cell composition in bone marrow aspirate relates to clinical outcomes when used for cervical spine fusion

Anterior cervical discectomy and fusion (ACDF) is performed to relieve pain caused by degenerative disk disease and nerve obstruction. As an alternative to bone graft, autologous concentrated bone marrow aspirate (CBMA) is used to achieve vertebral fusion with a satisfactory success rate. This has been attributed in part to bone marrow-resident mesenchymal stromal cells (MSCs) with the capacity to differentiate into osteoblasts and generate bone tissue. To date, there has been no study comparing cellular yields, MSC frequencies and their osteogenic potential with ACDF outcome. Patients (n = 24) received ACDF with CBMA and allograft bone matrix. Colony forming unit fibroblast (CFU-F) and CFU-osteoblasts (CFU-O) assays were performed on CBMA samples to enumerate MSCs (CFU-F) and osteogenic MSCs (CFU-O). CFUs were normalized to CBMA volume to define yield and also to mononuclear cells (MNC) to define frequency. After 1-year, fusion rates were good (86.7%) with pain and disability improved. There was a negative relationship between MNC and CFU-F measurements with age of patient and CFU-Os negatively correlated with age in females but not males. Tobacco use did not affect CBMA but was associated with poorer clinical outcome. Surprisingly, we found that while high-grade fusion was not associated with CFU-O, it correlated strongly (p<0.0067) with CBMA containing the lowest frequencies of CFU-F (3.0x10^-6–5.83x10^-5 CFU-F/MNC). MNC levels alone were not responsible for the results. These observations suggest that osteogenesis by human bone marrow is controlled by homeostatic ratio of MSCs to other cellular bone marrow components rather than absolute level of osteogenic MSCs, and that a lower ratio of MSCs to other cellular components in marrow tends to predict effective osteogenesis during ACDF. The results presented herein challenge the current dogma surrounding the proposed mechanism of MSCs in bone healing.

Cellular therapies for the treatment of non-union: the past, present and future

Non-union fracture is a pathological condition having some impairment of the cellular part of the repair: a reduction of MSC and of the osteoblastic activation. Non union is therefore a good indication for cell-based therapies using stem cells. We described the rational of this treatment and described the technique of autologous bone marrow concentrate implantation that was until now used. With the development of stem cell research and regenerative medicine, we believed that therapy based on cytotherapy has great potential. In this review, clinical applications of cytotherapy are summarized and analyzed. Current problems and future challenges are discussed.

Slowing the Onset of Hypoxia Increases Colony Forming Efficiency of Connective Tissue Progenitor Cells In Vitro

BACKGROUND

Survival and colony formation by transplanted tissue derived connective tissue progenitor cells (CTPs) are thought to be important factors in the success of clinical tissue engineering strategies for bone regeneration. Transplantation of cells into defects larger than a few millimeters expose cells to a profoundly hypoxic environment. This study tested the hypothesis that delaying the onset of hypoxia will improve the survival and performance of CTPs in vitro.

METHODS

To mimic declines seen in an avascular in vivo bone defect, colony forming efficiency by marrow derived nucleated cells was assessed under osteogenic conditions. Variation in the rate of oxygen decline from an oxygen tension of 21% to 0.1% oxygen was explored using an incubator with programmable active control of gas concentrations. The effect of doping cultures with defined concentrations of RBCs was also used to evaluate the potential for RBCs to serve as a natural buffer in the setting of declining oxygen levels.

RESULTS

A delay in onset of hypoxia over 96 hours resulted in a 3-fold increase in the relative colony forming efficiency (rCFE) of CTPs as compared to an immediate onset of hypoxia. The presence of RBCs in vitro inhibited the rCFE of CTPs. Given the negative effects of RBCs, methods of RBC removal were evaluated and compared for their effectiveness of RBC removal and retention of colony forming efficiency.

CONCLUSIONS

These data suggest that conditions of hypoxia compromise colony forming efficiency in marrow derived CTPs. However, slowing the rate of decline of oxygen preserved colony forming efficiency at levels achieved in a stable normoxic (3% O₂) environment. These data also suggest that RBCs are detrimental to the rCFE of CTPs and that buffy coat is an effective and preferred method for removing RBCs from marrow aspirates while preserving CTPs. These findings may inform clinical strategies for CTP transplantation.

Risk factors for nonunion in 337 displaced midshaft clavicular fractures treated with Knowles pin fixation

BACKGROUND

Clavicular fractures account for nearly 10 % of all fractures, and the majority of those fractures involve the midshaft. Historically, these fractures were treated nonoperatively; however, recent data suggest an increased risk of nonunion and symptomatic malunion for displaced, comminuted midshaft clavicular fractures treated conservatively. Surgical intervention via plate osteosynthesis or intramedullary fixation with pins, nails, or screws has been shown to reduce, but not eliminate, this risk. Identification of risk factors predictive of nonunion would improve the overall management of displaced, comminuted midshaft clavicular fractures.

METHODS

The medical records of 337 consecutive patients who underwent Knowles pin fixation and supplemental cerclage for the treatment of displaced, comminuted midshaft clavicular fractures between April 2007 and March 2009 were retrospectively reviewed. The records of the mechanism of injury, side of injury, Robinson fracture classification, presence of associated injuries, cerclage material, and patient-related variables, including diabetes mellitus, hypertension and smoking, were analyzed. Variables were assessed by univariate and multivariate analysis to identify those factors significantly associated with the development of fracture nonunion.

RESULTS

A total of 19 nonunions occurred. Increasing age and use of wire for supplemental cerclage fixation were significantly associated with an increased risk for fracture nonunion (p < 0.001). Although suggested as predictors of nonunion in other studies, female gender and fracture severity were not significantly associated with nonunion.

CONCLUSIONS

Nonunion remains a significant complication in the treatment of displaced, comminuted midshaft clavicular fractures even with intramedullary fixation. Use of absorbable suture in place of wire for cerclage fixation and careful selection of treatment strategy in the elderly may reduce the risk for nonunion.

Exploring the application of stem cells in tendon repair and regeneration

PURPOSE

To conduct a systematic review of the current evidence for the effects of stem cells on tendon healing in preclinical studies and human studies.

METHODS

A systematic search of the PubMed, CINAHL (Cumulative Index to Nursing and Allied Health Literature), Cochrane, and Embase databases was performed for stem cells and tendons with their associated terminology. Data validity was assessed, and data were collected on the outcomes of trials.

RESULTS

A total of 27 preclinical studies and 5 clinical studies met the inclusion criteria. Preclinical studies have shown that stem cells are able to survive and differentiate into tendon cells when placed into a new tendon environment, leading to regeneration and biomechanical benefit to the tendon. Studies have been reported showing that stem cell therapy can be enhanced by molecular signaling adjunct, mechanical stimulation of cells, and the use of augmentation delivery devices. Studies have also shown alternatives to the standard method of bone marrow-derived mesenchymal stem cell therapy. Of the 5 human studies, only 1 was a randomized controlled trial, which showed that skin-derived tendon cells had a greater clinical benefit than autologous plasma. One cohort study showed the benefit of stem cells in rotator cuff tears and another in lateral epicondylitis. Two of the human studies showed how stem cells were successfully extracted from the humerus and, when tagged with insulin, became tendon cells.

CONCLUSIONS

The current evidence shows that stem cells can have a positive effect on tendon healing. This is most likely because stem cells have regeneration potential, producing tissue that is similar to the preinjury state, but the results can be variable. The use of adjuncts such as molecular signaling, mechanical stimulation, and augmentation devices can potentially enhance stem cell therapy. Initial clinical trials are promising, with adjuncts for stem cell therapy in development.

The use of bone-graft substitutes in large bone defects: any specific needs?

INTRODUCTION

The gold standard for restoring bone defects is still considered to be autologous bone grafting. However, clinical benefits are not guaranteed and donor-site complications and morbidity is not infrequent. Research is on-going for the development of alternative bone substitutes of both biological and synthetic origin. The purpose of this study was to evaluate the type of materials used and their efficacy for the treatment of large bone defects in traumatology and orthopaedic surgery.

MATERIALS AND METHOD

A literature review was carried out of Embase and PubMed databases. Inclusion criteria were articles in English language focusing on the use of bone substitutes in trauma and orthopaedic surgery for the treatment of bone defects and included details on the structural, biological or biomechanical properties of the pure product. Furthermore, based on two clinical challenges, fracture non-union and impaction grafting we elaborated on the use of polytherapy for large bone defects as guided by the diamond concept.

RESULTS

All the products indicated in this manuscript possess osteoconductive activities but have different resorption times and biomechanical properties. Bone graft substitute materials are used for a wide range of clinical applications even when the level of clinical evidence is low. The size and location of the defect and the local biological and mechanical environment as well as the biomechanical characteristics of the material determine the type of device that can be implanted in a bone defect.

CONCLUSION

Proper assessment of the biological and mechanical environment and accurate patient selection are necessary to judge the extent of therapy the injury warrants. A sound understanding of various aspects of biomaterial properties and their relation and influence towards bone healing is of utmost importance. We suggest the application of polytherapy for the treatment of large bone defects and advocate the use of the diamond concept as a guideline.

Use of solid and cancellous autologous bone graft for fractures and nonunions

Bone is the second most commonly implanted material in the human body, after blood transfusion, with an estimated 600,000 grafts performed annually. Although the market for bone graft substitutes is more than $1 billion, that of bone graft itself is still more than half that amount. Reports of autologous bone grafting date back to the ancient Egyptians, yet the modern scientific study of grafting began in the early 19th century. Since then, the indications, methodology, and science of bone grafts in nonunion and bone loss have been established and refined, and new methods of harvesting and treatment are being developed and implemented. This article describes the use of solid and cancellous bone graft in the treatment of acute bone loss and nonunion.