Transpedicular aspiration of osteoprogenitor cells from the vertebral body: progenitor cell concentrations affected by serial aspiration

Vertebral body versus iliac crest bone marrow as a source of multipotential stromal cells: Comparison of processing techniques, tri-lineage differentiation and application on a scaffold for spine fusion

The potential use of bone progenitors, multipotential stromal cells (MSCs) helping spine fusion is increasing, but convenient MSC sources and effective processing methods are critical factors yet to be optimised. The aim of this study was to test the effect of bone marrow processing on the MSC abundance and to compare the differentiation capabilities of vertebral body-bone marrow (VB-BM) MSCs versus iliac crest-bone marrow (IC-BM) MSCs. We assessed the effect of the red blood cell lysis (ammonium chloride, AC) and density-gradient centrifugation (Lymphoprep™, LMP), on the extracted VB-BM and IC-BM MSC numbers. The MSC abundance (indicated by colony counts and CD45lowCD271high cell numbers), phenotype, proliferation and tri-lineage differentiation of VB-BM MSCs were compared with donor-matched IC-BM MSCs. Importantly, the MSC attachment and osteogenesis were examined when VB-BM and IC-BM samples were loaded on a beta-tricalcium phosphate scaffold. In contrast to LMP, using AC yielded more colonies from IC-BM and VB-BM aspirates (p = 0.0019 & p = 0.0201 respectively). For IC-BM and VB-BM, the colony counts and CD45lowCD271high cell numbers were comparable (p = 0.5186, p = 0.2640 respectively). Furthermore, cultured VB-BM MSCs exhibited the same phenotype, proliferative and adipogenic potential, but a higher osteogenic and chondrogenic capabilities than IC-BM MSCs (p = 0.0010 and p = 0.0005 for calcium and glycosaminoglycan (GAG) levels, respectively). The gene expression data confirmed higher chondrogenesis for VB-BM MSCs than IC-BM MSCs, but osteogenic gene expression levels were comparable. When loaded on Vitoss™, both MSCs showed a similar degree of attachment and survival, but a better osteogenic ability was detected for VB-BM MSCs as measured by alkaline phosphatase activity (p = 0.0386). Collectively, the BM processing using AC had more MSC yield than using LMP. VB-BM MSCs have a comparable phenotype and proliferative capacity, but higher chondrogenesis and osteogenesis with or without using scaffold than donor-matched IC-BM MSCs. Given better accessibility, VB-BM could be an ideal MSC source for spinal bone fusion.

Cell-based approaches for augmentation of tendon repair

Cell-based approaches are among the principal interventions in orthobiologics to improve tendon and ligament healing and to combat degenerative processes. The number of options available for investigation are expanding rapidly and investigators have an increasing number of cell types to choose from for research purposes. However, in part due to the current regulatory environment, the list of available cells at clinicians' disposal for therapeutic purposes is still rather limited. In this review, we present an overview of the main cellular categories in current use. Notable recent developments in cell-based approaches include the introduction of diverse sources of mesenchymal stem cells, pluripotent cells of extra-embryonic origin, and the emerging popularity of fully differentiated cells such as tenocytes and endothelial cells. Delivery strategies are discussed and a succinct discussion of the current regulatory environment in the United States is presented.

Mesenchymal stromal cells in spinal fusion: Current and future applications

Mesenchymal stromal cells (MSCs) have been a promising area of study for regenerative medicine. These cells can be harvested from bone marrow, adipose tissue, and other areas allowing for autologous transplantation of these cells into the area of degeneration or injury. With the proper signals, these cells may be able to regenerate healthy tissue. Recent studies have yielded promising evidence supporting translational mesenchymal stromal cell applications particularly in spinal fusion surgery.

Bone marrow mesenchymal stem cell aspirates from alternative sources: is the knee as good as the iliac crest?

INTRODUCTION

The most common method to obtain human mesenchymal stem cells (MSCs) is bone marrow aspiration from the iliac crest, but MSCs have also been isolated from different bones. The main purpose of this study was to compare bone marrow MSCs aspirated from the metaphysis of the distal femur and the proximal tibia with those obtained from the iliac crest, and to determine whether these locations represent potential alternative sources of MSCs for research and clinical application.

MATERIALS AND METHODS

Bone marrow was aspirated from the iliac crest and the metaphysis of the distal femur and the proximal tibia during total knee arthroplasty in 20 patients. The aspirates were centrifuged by density gradient, then mononucleated cell (MNC) concentration in the different aspirates was determined using a Coulter counter. MSCs were isolated, cultivated and characterised by their immunophenotype and by their in vitro potential for differentiation into osteoblasts, chondroblasts and adipocytes in specific media. Expansion and cell viability were quantified using trypan blue staining and cell counting with a haemocytometer (Neubauer chamber). The three sources were compared in terms of MNC concentration, viability of the cultures and presence of MSC using the Wilcoxon test.

RESULTS

MNC concentration was significantly higher in the iliac crest (10.05 Millions/ml) compared with the femur (0.67 Millions/ml) and tibia (1.7 Millions/ml). Culture success rates were 90%, 71% and 47% for MSCs from the iliac crest, femur and tibia, respectively. Flow cytometry analysis showed the presence of CD90+, CD105+, CD73+, VEGF+, CD71+, HLA-DR-, CD45-, CD34-, CD19-, and CD14- cells. The immunophenotype pattern of MSCs was similar for the three locations. Trilineage differentiation was achieved with all samples.

CONCLUSIONS

MSCs can be found in bone marrow from the metaphysis of both the distal femur and the proximal tibia. The phenotype and differentiation potential of these cells are similar to those of bone marrow MSCs from the iliac crest. Bone marrow aspiration from these locations is a relatively easy and safe alternative to that from the iliac crest for obtaining MSCs. Further study is required to assess whether the concentrations of MSCs obtained from these sources are sufficient for one-step therapeutic purposes.

Optimal aspiration volume of vertebral bone marrow for use in spinal fusion

BACKGROUND CONTEXT

Bone marrow aspirate (BMA) has shown promise as a bone graft option in spinal fusion. The vertebral body is a convenient source for marrow aspirate as it is accessed in routine course of pedicle screw instrumentation. Studies have relied on data from the iliac crest to determine optimal aspiration volume from the vertebral body.

PURPOSE

This study is designed to determine the optimal aspiration volume for BMA taken from the vertebral body.

STUDY DESIGN

Prospective clinical study.

PATIENT SAMPLE

Data are drawn from 18 pedicles and 180 aspirations. The average age of the subjects was 50.3 years, and the subject pool comprised five men and seven women.

OUTCOME MEASURES

Nucleated cell count and alkaline phosphatase staining colony forming units.

METHODS

Ten 1 mL aliquots of BMA were incrementally aspirated through a cannulated pedicle tap for each instrumented vertebral body. The numbers of nucleated cells per mL of BMA were analyzed with a hemocytometer, and the percentage of osteoprogenitor cells per mL aspirate were estimated by an alk phos production assay. The study was funded through departmental funds, and none of the authors have any conflicts of interest to report related to the study.

RESULTS

Nucleated cell count decreased with increasing aspirate number (p<.001). The average cell count for the first mL was 45.8 million cells. Cell counts did not differ by age or sex (p=.943 and p=.685, respectively). Likewise, osteoprogenitor cell percentage decreased with increasing aspirate number (p<.001).

CONCLUSIONS

The 2 mL aspirate volume has been defined as ideal for the iliac crest, but there has been no analogous assessment of the effect of aspiration volume for other sources such as the vertebral body. This information is important for the clinical implementation of vertebral body aspirations if volume, cells, and presumably performance, of this potential bone graft option are to be optimized for spine cases. Our data show a direct relationship between increasing aspiration number and decreasing osteoprogenitor cellular concentration, with a drop to 50% of the original aspirate cell count by the 4th mL aspirate. The vertebral body is a potentially exciting source of osteoprogenitor cells that can be implemented for a variety of spinal uses.

Tissue engineering strategies in spinal arthrodesis: the clinical imperative and challenges to clinical translation

Skeletal disorders requiring the regeneration or de novo production of bone present considerable reconstructive challenges and are one of the main driving forces for the development of skeletal tissue engineering strategies. The skeletal or mesenchymal stem cell is a fundamental requirement for osteogenesis and plays a pivotal role in the design and application of these strategies. Research activity has focused on incorporating the biological role of the mesenchymal stem cell with the developing fields of material science and gene therapy in order to create a construct that is not only capable of inducing host osteoblasts to produce bone, but is also osteogenic in its own right. This review explores the clinical need for reparative approaches in spinal arthrodesis, identifying recent tissue engineering strategies employed to promote spinal fusion, and considers the ongoing challenges to successful clinical translation.

Comparison of mesenchymal stem cells (osteoprogenitors) harvested from proximal humerus and distal femur during arthroscopic surgery

PURPOSE

The aim of this study was to examine the relations between age, gender, and number of viable mesenchymal stem cells (MSCs) in concentrated bone marrow (BM) obtained from the proximal humerus and distal femur during arthroscopic surgery.

METHODS

BM was aspirated from either the proximal humerus (n = 55) or distal femur (n = 29) during arthroscopic surgery in 84 patients (51.3 ± 11.6 years). MSCs were obtained from fractionated bone marrow after a 5-minute spin at 1,500 rpm. Volume of BM and number of nucleated cells (NCs) were calculated, and samples were cultured for 6 days, after which point colony-forming units (CFUs) were quantified and fluorescence-activated cell sorting (FACS) analysis was performed. Simple linear regression was used to explore relations between age, gender, volume of aspirated BM, and MSCs per milliliter.

RESULTS

BM aspirations yielded a mean quantity of 22.6 ± 12.3 mL. After centrifugation, 30.0 ± 16.7 × 10(6) nucleated cells/mL of concentrated BM were harvested. The proximal humerus provided 38.7 ± 52.6 × 10(6), and the distal femur, 25.9 ± 14.3 × 10(6), for an overall 766.3 ± 545.3 MSCs/mL of concentrated BM (proximal humerus: 883.9 ± 577.6, distal femur: 551.3 ± 408.1). Values did not significantly differ by age, gender, or donor site.

CONCLUSIONS

Arthroscopic aspiration of bone marrow from the proximal humerus and distal femur is a reproducible technique and yields reliable concentrations of MSCs. The use of an intraoperative concentration method resulted in consistent amounts of MSCs in all clinically relevant age groups without a significant drop of the number of isolated MSCs.

CLINICAL RELEVANCE

Human MSCs derived from concentrated bone marrow aspirate are a promising biological addition that may have practical use in the future of soft tissue augmentation. Arthroscopic techniques for bone marrow aspiration that do not require an additional surgical site for aspiration (e.g., iliac crest) or a second operative procedure may facilitate future use of MSCs in arthroscopic surgery.

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.

Equine bone marrow-derived mesenchymal stromal cells (BMDMSCs) from the ilium and sternum: are there differences?

REASONS FOR PERFORMING STUDY

The 2 sites of bone marrow harvest for isolation of mesenchymal stromal cells (MSC) in the horse are the sternum and ilium. The technical procedure is based on practitioner preference, but no studies have compared MSC concentrations and growth rates between the sites in horses aged 2-5 years.

OBJECTIVES

The objective of this study was to compare nucleated cell counts and growth rates between the sternum and ilium and between consecutive 5 ml bone marrow aspirates. We hypothesised that there would be a higher concentration of MSCs in the sternum than the ilium, and that the first sequential aspirate from either site would yield the greatest concentration of MSCs. We hypothesised that growth rates of cells from each site would not differ.

METHODS

Seven horses, aged 2 to 5 years, had 2 sequential 5 ml marrow aspirates taken from the sternum and ilium. Nucleated cell counts (NCCs) were obtained before and after marrow processing. Cells were expanded in culture for 3 passages and growth rate characteristics compared for all aspirates.

RESULTS

The NCCs of the first 5 ml aspirate were higher than those of the second 5 ml aspirate for both sites (P<0.05). There was no difference between growth rates for any of the groups (P>0.05).

CONCLUSIONS

The NCCs and growth rates of progenitor cells in the ilium and sternum are similar for horses in the 2-5 year age category. The first 5 ml bone marrow aspirate has a higher concentration of NCCs and resulting bone marrow-derived MSC population than subsequent aspirates.

POTENTIAL RELEVANCE

The first 5 ml aspirates from the sternum and ilium offer a rich supply of bone marrow-derived MSCs with similar growth rate characteristics. The harvesting procedure of only a 5 ml draw from either the sternum or ilium should result in adequate numbers of MSCs.

Silicate-substituted calcium phosphate as a bone graft substitute in surgery for adolescent idiopathic scoliosis

STUDY DESIGN AND OBJECTIVE

The purpose of this prospective clinical study is to evaluate the clinical and radiographic outcomes using a silicate-substituted calcium phosphate (Si-CaP) as a bone graft substitute in surgery for adolescent idiopathic scoliosis (AIS). In posterior corrective surgery for AIS, harvesting autologous bone from the iliac crest still represents the gold standard to augment the local bone graft though it is comparatively invasive and associated with donor site morbidity. Si-CaP enriched with bone marrow aspirate (BMA) might be an appropriate bone graft extender to overcome these difficulties.

METHODS

Eighteen female and three male patients with AIS who underwent corrective posterior instrumentation were observed clinically and radiographically for a minimum of 24 months. In all cases, 20-40 ml Si-CaP granules (ACTIFUSE) mixed with BMA from vertebral bodies was used to extend the local bone graft. Fusion was assessed by standardized conventional radiographs regarding loss of correction and implant failure. Clinical outcome was evaluated with use of the Scoliosis Research Society-22 patient Questionnaire (SRS-22) and a Visual Analog Scale (VAS) for back pain.

RESULTS

Cobb angle of major curves averaged 63° preoperatively, 22° after surgery, and 24° at final follow-up, with a maximum loss of correction of 7° recorded after 4 months. No adverse effects related to the study material had been observed. In all patients, there was no evidence of implant failure, and formation of an increasingly densifying 'fusion mass' was visible, as assessed by conventional radiography. VAS score for back pain averaged 1.7 before surgery, 2.3 at discharge, and 1.5 at final follow-up. Outcome assessment using the SRS-22 revealed a significantly enhanced overall health-related quality of life (84 vs. 74 % before surgery; P = 0.0005) due to a significant improvement of the domains 'self image' (77 vs. 59 %; P = 0.0002) and 'pain' (88 vs. 80 %; P = 0.02). Patients' management satisfaction averaged 93 %.

CONCLUSIONS

Si-CaP augmented with BMA from vertebral bodies seems to prove an effective, safe, and easy to handle bone graft extender in scoliosis surgery and thus a suitable alternative to bone harvesting procedures.

Rapid isolation of human stem cells (connective progenitor cells) from the distal femur during arthroscopic knee surgery

PURPOSE

(1) To safely obtain bone marrow aspirates from the distal femur during arthroscopic knee surgery, (2) to purify and efficiently concentrate connective tissue progenitor cells (CTPs) in the operating room (OR), and (3) to confirm that these are CTPs through their ability to differentiate into bone cells.

METHODS

Bone marrow aspirates were harvested from the distal femur during arthroscopic knee surgery in 26 patients. Twenty-five matched control subjects were selected to evaluate for increased incidence of complications. CTPs were isolated using a rapid method designed for use in the OR compared with 2 accepted methods. Cytochemical and molecular analysis was used to assess osteogenic potential.

RESULTS

Osteogenic potential of the CTPs was confirmed by reverse transcription polymerase chain reaction analysis and cellular staining. Bone marrow was successfully aspirated in 25 cases, with 3 incidences of stiffness in the aspirate group compared with 2 in the control group, 1 incidence of a wound irregularity in the aspirate group compared with 1 in the control group, and 3 incidences of hemarthrosis/persistent effusion in the aspirate group compared with 1 in the control group. The rate of complications for the aspirate group was 36% compared with 25% in the control group.

CONCLUSIONS

Our intention was to develop a technique for extracting and purifying bone marrow so that the orthopaedic surgeon would have a simple, safe, and efficient process by which to isolate CTPs during arthroscopic knee surgery. This method of aspiration did not lead to a significant increase in complications. Further bone marrow aspirate was successfully purified in the OR, with only a slight increase in surgery time, and resulted in a fractionated layer rich with CTPs. These cells showed osteogenic potential, as evidenced by their osteoblastic differentiation. These CTPs may have future use in enhancing the incorporation of the graft into the bone.

LEVEL OF EVIDENCE

Level III, matched case-control study.