The potential of stem cells in orthopaedic surgery

Bone Marrow Aspirate Concentrate for Treatment of Primary Knee Osteoarthritis: A Prospective, Single-Center, Non-randomized Study with 2-Year Follow-Up

Introduction

Knee osteoarthritis (OA) is a widespread, disabling condition with no intervention to fully restore cartilage or halt progression. Bone marrow aspirate concentrate (BMAC), an autologous product from bone marrow aspiration, has shown promise as a regenerative therapy due to its cell composition and chondrogenic effects. Our study aims to assess the functional outcomes, including pain, function, satisfaction, and complications post-BMAC injection in knee OA patients.

Materials and Methods

In this prospective, single-center study, 63 patients with grade II-III knee OA (Kellgren-Lawrence (K-L) scale) unresponsive to conservative management underwent BMAC injection. The procedure involved bone marrow aspiration from the anterior iliac crest, processing to obtain a concentrate, followed by intra-articular injection. Patients were followed for 24 months, assessing outcomes using the Visual Analog Scale (VAS), International Knee Documentation Committee (IKDC) score, and MOCART 2.0 score.

Results

The cohort, with a slight female predominance and predominantly aged 41-50 years, majorly comprised K-L grade III OA patients. BMAC treatment resulted in significant improvements in VAS pain scores, IKDC functional scores, and MOCART 2.0 scores over the 24-month follow-up.

Conclusion

BMAC injection provides significant improvement in both pain and functional outcomes at mid-term follow-up in patients with mild-to-moderate OA of the knee. Further high-quality, adequately powered, multi-center, prospective, double-blinded, randomized controlled trials with longer follow-up are necessary to justify the routine clinical use of BMAC for treatment of patients suffering with knee OA.

Graphical Abstract

BMP-2 Enhances Osteogenic Differentiation of Human Adipose-Derived and Dental Pulp Stem Cells in 2D and 3D In Vitro Models

Bone tissue provides support and protection to different organs and tissues. Aging and different diseases can cause a decrease in the rate of bone regeneration or incomplete healing; thus, tissue-engineered substitutes can be an acceptable alternative to traditional therapies. In the present work, we have developed an in vitro osteogenic differentiation model based on mesenchymal stem cells (MSCs), to first analyse the influence of the culture media and the origin of the cells on the efficiency of this process and secondly to extrapolate it to a 3D environment to evaluate its possible application in bone regeneration therapies. Two osteogenic culture media were used (one commercial from Stemcell Technologies and a second supplemented with dexamethasone, ascorbic acid, glycerol-2-phosphate, and BMP-2), with human cells of a mesenchymal phenotype from two different origins: adipose tissue (hADSCs) and dental pulp (hDPSCs). The expression of osteogenic markers in 2D cultures was evaluated in several culture periods by means of the immunofluorescence technique and real-time gene expression analysis, taking as reference MG-63 cells of osteogenic origin. The same strategy was extrapolated to a 3D environment of polylactic acid (PLA), with a 3% alginate hydrogel. The expression of osteogenic markers was detected in both hADSCs and hDPSCs, cultured in either 2D or 3D environments. However, the osteogenic differentiation of MSCs was obtained based on the culture medium and the cell origin used, since higher osteogenic marker levels were found when hADSCs were cultured with medium supplemented with BMP-2. Furthermore, the 3D culture used was suitable for cell survival and osteogenic induction.

Osteochondral Lesions of the Ankle Treated with Bone Marrow Concentrate with Hyaluronan and Fibrin: A Single-Centre Study

Osteochondral defects of the ankle (OCD) are being increasingly identified as a clinically significant consequence of injury to the ankle, with the potential to lead to osteoarthritis if left untreated. The aim of this retrospective cohort study was to evaluate a single-stage treatment of OCD, based on bone marrow aspirate (BMA) centrifuged to produce bone marrow concentrate (BMC). In a dual syringe, the concentrate was mixed with thrombin in one syringe, whereas hyaluronan and fibrinogen were mixed in a second syringe. The two mixtures were then injected and combined into the prepared defect. Clinical outcome and quality of life scores (MOXFQ and EQ-5D) were collected at baseline and yearly thereafter. Multilevel models were used to analyse the pattern of scores over time. Ninety-four patients were treated between 2015 and 2020. The means of each of the three components of the MOXFQ significantly improved between baseline and 1 year (p < 0.001 for each component), with no further change from year 1 to year 3. The EQ-5D index also improved significantly from baseline to 1 year, with no evidence for further change. Our results strongly indicate that this BMC treatment is safe for, and well tolerated by, patients with OCD of the ankle as both primary treatment and those who have failed primary treatment. This technique provides a safe, efficacious alternative to currently employed cartilage repair techniques, with favourable outcomes and a low complication rate at 36 months.

Effect of Biomedical Materials in the Implementation of a Long and Healthy Life Policy

This paper is divided into seven main parts. Its purpose is to review the literature to demonstrate the importance of developing bioengineering and global production of biomaterials to care for the level of healthcare in the world. First, the general description of health as a universal human value and assumptions of a long and healthy life policy is presented. The ethical aspects of the mission of medical doctors and dentists were emphasized. The coronavirus, COVID-19, pandemic has had a significant impact on health issues, determining the world’s health situation. The scope of the diseases is given, and specific methods of their prevention are discussed. The next part focuses on bioengineering issues, mainly medical engineering and dental engineering, and the need for doctors to use technical solutions supporting medicine and dentistry, taking into account the current stage Industry 4.0 of the industrial revolution. The concept of Dentistry 4.0 was generally presented, and a general Bioengineering 4.0 approach was suggested. The basics of production management and the quality loop of the product life cycle were analyzed. The general classification of medical devices and biomedical materials necessary for their production was presented. The paper contains an analysis of the synthesis and characterization of biomedical materials supporting medicine and dentistry, emphasizing additive manufacturing methods. Numerous examples of clinical applications supported considerations regarding biomedical materials. The economic conditions for implementing various biomedical materials groups were supported by forecasts for developing global markets for biomaterials, regenerative medicine, and tissue engineering. In the seventh part, recapitulation and final remarks against the background of historical retrospection, it was emphasized that the technological processes of production and processing of biomedical materials and the systematic increase in their global production are a determinant of the implementation of a long and healthy policy.

Induction of notochordal differentiation of bone marrow mesenchymal‑derived stem cells via the stimulation of notochordal cell‑rich nucleus pulposus tissue

The degeneration of intervertebral disc (IVD) tissue, initiated following the disappearance of notochordal cells (NCs), is characterized by the decreased number of nucleus pulposus (NP) cells (NPCs) and extracellular matrix. Transplanting proper cells into the IVD may sustain cell numbers, resulting in the synthesis of new matrix; this represents a minimally invasive regenerative therapy. However, the lack of cells with a correct phenotype severely hampers the development of regenerative therapy. The present study aimed to investigate whether porcine NC‑rich NP tissue stimulates bone marrow‑derived mesenchymal stem cell (BM‑MSC) differentiation toward NC‑like cells, which possess promising regenerative ability, for the treatment of disc degeneration diseases. BM‑MSCs were successfully isolated from porcine femurs and tibiae, which expressed CD90 and CD105 markers and did not express CD45. Differentiation induction experiments revealed that the isolated cells had osteogenic and adipogenic differentiation potential. When co‑cultured with NC‑rich NP tissue, the BM‑MSCs successfully differentiated into NC‑like cells. Cell morphological analysis revealed that the cells exhibited an altered morphology, from a shuttle‑like to a circular one, and the expression of NC marker genes, including brachyury, keratin‑8, and keratin‑18, was enhanced, and the cells exhibited the ability to generate aggrecan and collagen II. Taken together, the findings of the present study demonstrated that the primarily isolated and cultured BM‑MSCs may be stimulated to differentiate into NC‑like cells by porcine NC‑rich NP explants, potentially providing an ideal cell source for regenerative therapies for disc degeneration diseases.

Bone marrow-derived mesenchymal stem cells promote healing of rabbit tibial fractures via JAK-STAT signaling pathway

Influence of bone marrow-derived mesenchymal stem cells (BMMSCs) on the healing of rabbit tibial fractures and the role of the Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway in fracture healing were explored. Rabbit BMMSCs were isolated and cultured in vitro, and their purity was determined using flow cytometry. Rabbit fracture models were established, and injected with BMMSCs, BMMSCs + TG101348 or TG101348, with those injected with an equal volume of normal saline as control group, and the repair of fracture ends was evaluated via X-ray examination 3 weeks later. The BMMSCs isolated in vitro grew well, and flow cytometry assay results showed that the positive expression rates of cluster of differentiation (CD)90 and CD105 in cells were 99.21 and 99.56%, respectively, with no CD45 expressed. According to the results of CCK-8 assay, TG101348 lowered the proliferation level of BMMSCs, and the wound healing assay revealed that the migration ability of BMMSCs at 24 and 48 h was substantially weaker than that in control group (P<0.05). After induction of osteogenic differentiation for 3 weeks, alizarin red staining results manifested that osteogenic induction group had notably more calcium nodules than TG101348 group (P<0.05). Compared with those in control group, the protein expression levels of p-JAK2 and p-STAT3 were remarkably raised by osteogenic induction (P<0.05), but the protein expression levels of JAK2, p-JAK2 and p-STAT3 were considerably decreased by TG101348 (P<0.05). It was found through the X-ray examination that the rabbits in control group and those injected with BMMSCs recovered well, and the latter had larger external calluses at fracture ends than the former, while the fracture ends of those injected with TG101348 and BMMSCs + TG101348 were not healed completely. BMMSCs promote healing of rabbit tibial fractures through the JAK-STAT signaling pathway.

Arthroscopic Harvesting of Autologous Bone Graft for Use as a Mesenchymal Stem Cell Carrier in Anterior Cruciate Ligament Reconstruction

Anterior cruciate ligament (ACL) tears are detrimental to knee stability and normal function. Although the standard of treatment is an ACL reconstruction, technical improvements are sought to enhance clinical outcomes due to the appreciable failure rate. The use of autologous biologic substances as carriers of stem cells are desirable because of their multipotent properties. Traditionally, the collection of autologous bone grafts is through an open incision of the iliac crest, which causes substantial morbidity to the patient. This Technical Note describes an arthroscopic, minimally invasive collection method of autologous tibial and femoral bone graft to use in backfilling the tunnels during an ACL reconstruction to improve graft incorporation and clinical outcomes.

A prospective evaluation of bone marrow aspirate concentrate and microfracture in the treatment of osteochondral lesions of the talus

BACKGROUND

The term osteochondral lesion (OCL) refers to a defect involving the chondral surface and or subchondral bone. These lesions are associated with ankle injuries with bony and soft tissue and cause pain, decreased range of motion, swelling and impact adversely on quality of life. To date the standard treatment has been isolated microfracture (BMS). The aim of this study was to compare the outcomes of BMS alone to BMS augmented with bone marrow aspirate concentrate (BMAC) in the treatment of ankle OCLs.

METHODS

This study was a prospective cohort study carried out from 2010-2015 in a single surgeon's practice. Patients from 2010-2012 were treated with microfracture alone while patients from 2013-2015 were treated with micro fracture augmented with bone marrow aspirate concentrate and fibrin glue. Self-reported patient outcome measures were measured. Complications, revision rates, and visual analogue pain scores were compared.

RESULTS

101 patients were included in the study. 52 patients were in the microfracture group while 49 patients were in the microfracture/BMAC group. The minimum follow-up for both groups was 36 months. Both groups had a statistically significant improvement in pain scores, quality of life scores, participation in sport and activities of daily living. The revision rate was 28.8% in the microfracture group versus 12.2% in the microfracture/BMAC group, which was statistically significant, p=0.0145. The majority of the lesions were less than 1.5cm² in diameter in both cohorts.

CONCLUSIONS

Microfracture and bone marrow aspirate concentrate appears to be a safe and effective treatment option for osteochondral lesions of the talus. The addition of bone marrow aspirate concentrate does not result in any increase in ankle or donor site morbidity. It is a well-tolerated therapy which decreases revision rates for treatment of the osteochondral lesions when compared to microfracture alone.

LEVEL OF EVIDENCE

Level III.

Current Status of Stem Cell Therapies in Tissue Repair and Regeneration

Tissue engineering is a multi-disciplinary field such as material science, life science, and bioengineering that are necessary to make artificial tissue or rejuvenate damaged tissue. Numerous tissue repair techniques and substitute now exist even though it has several shortcomings; these shortcomings give a good reason for the continuous research for more acceptable tissue-engineered substitutes. The search for and use of a suitable stem cell in tissue engineering is a promising concept. Stem cells have a distinctive capability to differentiate and self-renew that make more suitable for cell-based therapies in tissue repair and regeneration. This review article focuses on stem cell for tissue engineering and their methods of manufacture with their application in nerve, bone, skin, cartilage, bladder, cardiac, liver tissue repair and regeneration.

Effectiveness of a single intra-articular bone marrow aspirate concentrate (BMAC) injection in patients with grade 3 and 4 knee osteoarthritis

Aim

To evaluate the clinical efficacy and safety of an intra-articular injection of bone marrow aspirate concentrate (BMAC) as a treatment option for osteoarthritis (OA) of the knee.

Materials and methods

Between June 2014 and February 2017, data from 233 patients with knee osteoarthritis treated with BMAC injection at a single center, were retrospectively evaluated. Only patients with idiopathic osteoarthritis were included. Exclusion criteria were post-traumatic osteoarthritis, previous knee surgery, age less than 50 years old or more than 85 years old, active infection, uncontrolled diabetes mellitus, rheumatological or other systemic disease, malignancy, or treatment with immunosuppressive drugs. Bone marrow from the iliac crest was aspirated/concentrated with a standardized technique using a single-spin manual method. Patients were evaluated before and after the procedure, using the numeric pain scale (NPS) and Oxford knee score (OKS). Mean follow-up period was 11 months, range (6–30 months).

Results

A total of 121 of 233 patients had completed data as previously defined and were included in the statistical analysis. There were 85 females and 36 males, with mean age 70 years (range 50–85). Compared to baseline, the mean NPS decreased from 8.33 to 4.49 (p < 0.001) and the mean OKS increased from 20.20 to 32.29 (P < 0.001) at final follow-up. There were no complications.

Conclusion

A single intra-articular injection of BMAC is a safe and reliable procedure that results in clinical improvement of knee OA.

Bone Marrow Aspirate Concentrate and Microfracture Technique for Talar Osteochondral Lesions of the Ankle

Osteochondral lesions of the talus refer to a chondral or subchondral defect of the articular cartilage and potentially the underlying bone. Ankle sprains are an extremely common injury; approximately 27,000 ankle sprains occur per day in America. Fifty percent of these can lead to a cartilage injury to the ankle. There has been a high quoted rate of failure with conservative measures of up to 45% in some series. Surgical options are largely broken down into 2 groups, namely, reparative or regenerative treatments. The reparative techniques include debridement and bone marrow stimulation techniques such as microdrilling and microfracture. Regenerative techniques include autologous osteochondral transplants. However, there are disadvantages in terms of donor site morbidity and the development of subchondral bone cysts over time. The aim of this video is to demonstrate a technique for microfracture and augmentation with bone marrow aspirate concentration and Tisseel fibrin glue. This video details the indications for performing microfracture, the indications for using bone marrow stimulation techniques, and the contraindications. Patient positioning, setup, preparation of the lesion, harvesting of the bone marrow aspirate concentrate, and application of the bone marrow aspirate are detailed.

Amniotic Mesenchymal Stromal Cells Exhibit Preferential Osteogenic and Chondrogenic Differentiation and Enhanced Matrix Production Compared With Adipose Mesenchymal Stromal Cells

BACKGROUND

Therapeutic efficacy of various mesenchymal stromal cell (MSC) types for orthopaedic applications is currently being investigated. While the concept of MSC therapy is well grounded in the basic science of healing and regeneration, little is known about individual MSC populations in terms of their propensity to promote the repair and/or regeneration of specific musculoskeletal tissues. Two promising MSC sources, adipose and amnion, have each demonstrated differentiation and extracellular matrix (ECM) production in the setting of musculoskeletal tissue regeneration. However, no study to date has directly compared the differentiation potential of these 2 MSC populations.

PURPOSE

To compare the ability of human adipose- and amnion-derived MSCs to undergo osteogenic and chondrogenic differentiation.

STUDY DESIGN

Controlled laboratory study.

METHODS

MSC populations from the human term amnion were quantified and characterized via cell counting, histologic assessment, and flow cytometry. Differentiation of these cells in comparison to commercially purchased human adipose-derived mesenchymal stromal cells (hADSCs) in the presence and absence of differentiation media was evaluated via reverse transcription polymerase chain reaction (PCR) for bone and cartilage gene transcript markers and histology/immunohistochemistry to examine ECM production. Analysis of variance and paired t tests were performed to compare results across all cell groups investigated.

RESULTS

The authors confirmed that the human term amnion contains 2 primary cell types demonstrating MSC characteristics-(1) human amniotic epithelial cells (hAECs) and (2) human amniotic mesenchymal stromal cells (hAMSCs)-and each exhibited more than 90% staining for MSC surface markers (CD90, CD105, CD73). Average viable hAEC and hAMSC yields at harvest were 2.3 × 10⁶ ± 3.7 × 10⁵ and 1.6 × 10⁶ ± 4.7 × 10⁵ per milliliter of amnion, respectively. As well, hAECs and hAMSCs demonstrated significantly greater osteocalcin ( P = .025), aggrecan ( P < .0001), and collagen type 2 ( P = .044) gene expression compared with hADSCs, respectively, after culture in differentiation medium. Moreover, both hAECs and hAMSCs produced significantly greater quantities of mineralized ( P < .0001) and cartilaginous ( P = .0004) matrix at earlier time points compared with hADSCs when cultured under identical osteogenic and chondrogenic differentiation conditions, respectively.

CONCLUSION

Amnion-derived MSCs demonstrate a greater differentiation potential toward bone and cartilage compared with hADSCs.

CLINICAL RELEVANCE

Amniotic MSCs may be the source of choice in the regenerative treatment of bone or osteochondral musculoskeletal disease. They show significantly higher yields and better differentiation toward these tissues than MSCs derived from adipose.

Does an Injection of Adipose-Derived Mesenchymal Stem Cells Loaded in Fibrin Glue Influence Rotator Cuff Repair Outcomes? A Clinical and Magnetic Resonance Imaging Study

BACKGROUND

The mesenchymal stem cell (MSC)-based tissue engineering approach has been developed to improve the treatment of rotator cuff tears. Hypothesis/Purpose: The purpose was to determine the effect of an injection of adipose-derived MSCs loaded in fibrin glue during arthroscopic rotator cuff repair on clinical outcomes and to evaluate its effect on structural integrity using magnetic resonance imaging (MRI). The hypothesis was that the application of adipose-derived MSCs would improve outcomes after the surgical repair of a rotator cuff tear.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Among 182 patients treated with arthroscopic surgery for a rotator cuff tear, 35 patients treated with arthroscopic rotator cuff repair alone (conventional group) were matched with 35 patients who underwent arthroscopic rotator cuff repair with an injection of adipose-derived MSCs loaded in fibrin glue (injection group) based on sex, age, and lesion size. Outcomes were assessed with respect to the visual analog scale (VAS) for pain, range of motion (ROM) (including forward flexion, external rotation at the side, and internal rotation at the back), and functional measures of the Constant score and University of California, Los Angeles (UCLA) shoulder rating scale. Repaired tendon structural integrity was assessed by using MRI at a minimum of 12 months after surgery, and the mean clinical follow-up was 28.8 ± 4.2 months in the conventional group and 28.3 ± 3.8 months in the injection group.

RESULTS

The mean VAS score at rest and during motion improved significantly in both groups after surgery. However, there were no significant differences between the groups at the final follow-up ( P = .256 and .776, respectively). Compared with preoperative measurements, forward flexion and external rotation at the side significantly improved at the final follow-up in both groups (all P < .05). However, no significant improvements in internal rotation at the back were observed in either group ( P = .625 and .834 for the conventional and injection groups, respectively). There were also no significant differences between the groups at the final follow-up for any of the 3 ROM positions (all P > .05). The mean Constant score and UCLA score improved significantly in both groups after surgery, but there were no significant differences between the groups at the final follow-up ( P = .634 and .302, respectively). MRI indicated a retear rate of 28.5% in the conventional group and 14.3% in the injection group ( P < .001).

CONCLUSION

This study revealed that an injection of adipose-derived MSCs loaded in fibrin glue during rotator cuff repair could significantly improve structural outcomes in terms of the retear rate. There were, however, no clinical differences in the 28-month period of follow-up. Although still in the early stages of application, MSC augmentation of surgical rotator cuff repair appears useful for providing an adequate biological environment around the repair site.

The Holy Grail of Orthopedic Surgery: Mesenchymal Stem Cells-Their Current Uses and Potential Applications

Only select tissues and organs are able to spontaneously regenerate after disease or trauma, and this regenerative capacity diminishes over time. Human stem cell research explores therapeutic regenerative approaches to treat various conditions. Mesenchymal stem cells (MSCs) are derived from adult stem cells; they are multipotent and exert anti-inflammatory and immunomodulatory effects. They can differentiate into multiple cell types of the mesenchyme, for example, endothelial cells, osteoblasts, chondrocytes, fibroblasts, tenocytes, vascular smooth muscle cells, and sarcomere muscular cells. MSCs are easily obtained and can be cultivated and expanded in vitro; thus, they represent a promising and encouraging treatment approach in orthopedic surgery. Here, we review the application of MSCs to various orthopedic conditions, namely, orthopedic trauma; muscle injury; articular cartilage defects and osteoarthritis; meniscal injuries; bone disease; nerve, tendon, and ligament injuries; spinal cord injuries; intervertebral disc problems; pediatrics; and rotator cuff repair. The use of MSCs in orthopedics may transition the practice in the field from predominately surgical replacement and reconstruction to bioregeneration and prevention. However, additional research is necessary to explore the safety and effectiveness of MSC treatment in orthopedics, as well as applications in other medical specialties.

Extracellular Matrix of Current Biological Scaffolds Promotes the Differentiation Potential of Mesenchymal Stem Cells

PURPOSE

The purpose of this study was to quantitatively assess the ability of bone marrow-derived mesenchymal stem cells (bMSC) to differentiate toward bone, fat, cartilage, and tendon lineages when grown on commercially available scaffolds compared with control and native tendon tissue.

METHODS

BMSCs were cultured and analyzed by fluorescent automated cells sorting for surface markers CD73, -90, and -105. BMSCs were grown on rotator cuff tendon (RCT), decellularized human dermis patch (DDP), bilayer collagen matrix, and fibrin matrix (FM) to test their differentiation potential using quantitative polymerase chain reaction and establish markers for osteogenic, adipogenic, chondrogenic, and tenogenic lineages. Immunocytochemical testing was used to determine the specific proteins present on the scaffolds.

RESULTS

Alkaline phosphatase and osteocalcin gene expression was significantly higher on RCT (P < .001) and collagen scaffold (CS) (P < .001) compared with DDP and FM scaffolds (P < .001, P < .001). When differentiated toward a cartilage lineage, bMSCs grown on CS had significantly more type II collagen and aggrecan compared with DDP (P < .001, P < .001), FM (P < .001, P < .001), and RCT (P < .001, P < .001). Differentiated bMSCs grown on the CS had a significant increase in PPARγ and FABP4 gene expression compared with bMSCs grown on all other scaffolds (all P < .001). The differentiation of bMSCs into tendon on CSs had significantly more tenacin C, decorin, and type III collagen gene expression when compared with RCT, DDP, and FM (all P < .001). Decorin gene expression in the control undifferentiated CS was also significantly increased, suggesting that the matrix alone may promote a tenogenic lineage (P = .637).

CONCLUSIONS

Differences in the extracellular matrix composition of scaffolds significantly impact their potential to promote differentiation of bMSCs. Comparing the native RCT to the tested scaffolds showed that a high content of type I and III collagen significantly increased the potential of bMSCs to differentiate toward bone, tendon, fat, and cartilage lineages.

CLINICAL RELEVANCE

This in vitro study shows the differences between commercially available scaffolds for rotator cuff repairs. Therefore, these results support clinical use depending on the surgical intention and the potential of bMSCs to differentiate into bone, tendon, cartilage, and fat tissue.

Mesenchymal Stem Cells Subpopulations: Application for Orthopedic Regenerative Medicine

Research on mesenchymal stem cells (MSCs) continues to progress rapidly. Nevertheless, the field faces several challenges, such as inherent cell heterogeneity and the absence of unique MSCs markers. Due to MSCs' ability to differentiate into multiple tissues, these cells represent a promising tool for new cell-based therapies. However, for tissue engineering applications, it is critical to start with a well-defined cell population. Additionally, evidence that MSCs subpopulations may also feature distinct characteristics and regeneration potential has arisen. In this report, we present an overview of the identification of MSCs based on the expression of several surface markers and their current tissue sources. We review the use of MSCs subpopulations in recent years and the main methodologies that have addressed their isolation, and we emphasize the most-used surface markers for selection, isolation, and characterization. Next, we discuss the osteogenic and chondrogenic differentiation from MSCs subpopulations. We conclude that MSCs subpopulation selection is not a minor concern because each subpopulation has particular potential for promoting the differentiation into osteoblasts and chondrocytes. The accurate selection of the subpopulation advances possibilities suitable for preclinical and clinical studies and determines the safest and most efficacious regeneration process.

Mesenchymal Stromal Cells Implantation in Combination with Platelet Lysate Product Is Safe for Reconstruction of Human Long Bone Nonunion

Objective

Nonunion is defined as a minimum of 9 months since injury without any visible progressive signs of healing for 3 months. Recent literature has shown that the application of mesenchymal stromal cells is safe, in vitro and in vivo, for treating long bone nonunion. The present study was performed to investigate the safety of mesenchymal stromal cell (MSC) implantation in combination with platelet lysate (PL) product for treating human long bone nonunion.

Materials and Methods

In this case series clinical trial, orthopedic surgeons visited eighteen patients with long bone nonunion, of whom 7 complied with the eligibility criteria. These patients received mesenchymal stromal cells (20 million cells implanted once into the nonunion site using a fluoroscopic guide) in combination with PL product. For evaluation of the effects of this intervention all the patients were followed up by taking anterior-posterior and lateral X-rays of the affected limb before and 1, 3, 6, and 12 months after the implantation. All side effects (local or systemic, serious or non-serious, related or unrelated) were observed during this time period.

Results

From a safety perspective the MSC implantation in combination with PL was very well tolerated during the 12 months of the trial. Four patients were healed; based on the control Xray evidence, bony union had occurred.

Conclusion

Results from the present study suggest that the implantation of bone marrow-derived MSCs in combination with PL is safe for the treatment of nonunion. A double blind, controlled clinical trial is required to assess the efficacy of this treatment (Registration Number: NCT01206179).

Bone Marrow Aspirate in the Treatment of Chondral Injuries

The ability of mesenchymal stem cells (MSCs) to transdifferentiate into a desired cell lineage has captured the imagination of scientists and clinicians alike. The limited ability for chondrocytes to regenerate in chondral injuries has raised the concept of using MSCs to help regenerate and repair damaged tissue. The expansion of cells in a laboratory setting to be delivered back to the patient is too costly for clinical use in the present tough economic climate. This process is slow with due to the complexity of trying to imitate the natural environment and biological stimulation of chondral cell replication and proliferation. Bone marrow aspirate concentrate (BMAC) has the potential to provide an easily accessible and readily available source of MSCs with key growth factors that can be used in treating chondral injuries. This review summarizes the underlying basic science of MSCs and the therapeutic potential of BMAC.

Impact of the source and serial passaging of goat mesenchymal stem cells on osteogenic differentiation potential: implications for bone tissue engineering

BACKGROUND

Adult mesenchymal stem cells (MSCs) can be conveniently sampled from bone marrow, peripheral blood, muscle, adipose and connective tissue, harvested from various species, including, rodents, dogs, cats, horses, sheep, goats and human beings. The MSCs isolated from adult tissues vary in their morphological and functional properties. These variations are further complicated when cells are expanded by passaging in culture. These differences and changes in MSCs must be considered prior to their application in the clinic or in a basic research study. Goats are commonly used as animal models for bone tissue engineering to test the potential of stem cells for bone regeneration. As a result, goat MSCs isolated from bone marrow or adipose tissue should be evaluated using in vitro assays, prior to their application in a tissue engineering project.

RESULTS

In this study, we compared the stem cell properties of MSCs isolated from goat bone marrow and adipose tissue. We used quantitative and qualitative assays with a focus on osteogenesis, including, colony forming unit, rate of cell proliferation, tri-lineage differentiation and expression profiling of key signal transduction proteins to compare MSCs from low and high passages. Primary cultures generated from each source displayed the stem cell characteristics, with variations in their osteogenic potentials. Most importantly, low passaged bone marrow MSCs displayed a significantly higher and superior osteogenic potential, and hence, will be the preferred choice for bone tissue engineering in future in vivo experiments. In the bone marrow MSCs, this process is potentially mediated by the p38 MAPK pathway. On the other hand, osteogenic differentiation in the adipose tissue MSCs may involve the p44/42 MAPK pathway.

CONCLUSIONS

Based on these data, we can conclude that bone marrow and fat-derived MSCs undergo osteogenesis via two distinct signaling pathways. Even though the bone marrow MSCs are the preferred source for bone tissue engineering, the adipose tissue MSCs are an attractive alternative source and undergo osteo-differentiation differently from the bone marrow MSCs and hence, might require a cell-based enhancer/inducer to improve their osteogenic regenerative capacity.

Engineering Stem Cells for Biomedical Applications

Stem cells are characterized by a number of useful properties, including their ability to migrate, differentiate, and secrete a variety of therapeutic molecules such as immunomodulatory factors. As such, numerous pre-clinical and clinical studies have utilized stem cell-based therapies and demonstrated their tremendous potential for the treatment of various human diseases and disorders. Recently, efforts have focused on engineering stem cells in order to further enhance their innate abilities as well as to confer them with new functionalities, which can then be used in various biomedical applications. These engineered stem cells can take on a number of forms. For instance, engineered stem cells encompass the genetic modification of stem cells as well as the use of stem cells for gene delivery, nanoparticle loading and delivery, and even small molecule drug delivery. The present Review gives an in-depth account of the current status of engineered stem cells, including potential cell sources, the most common methods used to engineer stem cells, and the utilization of engineered stem cells in various biomedical applications, with a particular focus on tissue regeneration, the treatment of immunodeficiency diseases, and cancer.

Application of Green Tea Catechin for Inducing the Osteogenic Differentiation of Human Dedifferentiated Fat Cells in Vitro

Despite advances in stem cell biology, there are few effective techniques to promote the osteogenic differentiation of human primary dedifferentiated fat (DFAT) cells. We attempted to investigate whether epigallocatechin-3-gallate (EGCG), the main component of green tea catechin, facilitates early osteogenic differentiation and mineralization on DFAT cells in vitro. DFAT cells were treated with EGCG (1.25-10 μM) in osteogenic medium (OM) with or without 100 nM dexamethasone (Dex) for 12 days (hereafter two osteogenic media were designated as OM(Dex) and OM). Supplementation of 1.25 μM EGCG to both the media effectively increased the mRNA expression of collagen 1 (COL1A1) and runt-related transcription factor 2 (RUNX2) and also increased proliferation and mineralization. Compared to OM(Dex) with EGCG, OM with EGCG induced earlier expression for COL1A1 and RUNX2 at day 1 and higher mineralization level at day 12. OM(Dex) with 10 μM EGCG remarkably hampered the proliferation of the DFAT cells. These results suggest that OM(without Dex) with EGCG might be a preferable medium to promote proliferation and to induce osteoblast differentiation of DFAT cells. Our findings provide an insight for the combinatory use of EGCG and DFAT cells for bone regeneration and stem cell-based therapy.

Adipose-derived stem cells: selecting for translational success

We have witnessed a rapid expansion of in vitro characterization and differentiation of adipose-derived stem cells, with increasing translation to both in vivo models and a breadth of clinical specialties. However, an appreciation of the truly heterogeneous nature of this unique stem cell group has identified a need to more accurately delineate subpopulations by any of a host of methods, to include functional properties or surface marker expression. Cells selected for improved proliferative, differentiative, angiogenic or ischemia-resistant properties are but a few attributes that could prove beneficial for targeted treatments or therapies. Optimizing cell culture conditions to permit re-introduction to patients is critical for clinical translation.

Advances of human bone marrow-derived mesenchymal stem cells in the treatment of cartilage defects: a systematic review

Mesenchymal stem cell (MSC)-based therapies represent a new option for treating damaged cartilage. However, the outcomes following its clinical application have seldom been previously compared. The present paper presents the systematic review of current literatures on MSC-based therapy for cartilage repair in clinical applications. Ovid, Scopus, PubMed, ISI Web of Knowledge and Google Scholar online databases were searched using several keywords, which include "cartilage" and "stem cells". Only studies using bone marrow-derived MSC (BM-MSC) to treat cartilage defects clinically were included in this review. The clinical outcomes were compared, and the quality of the tissue repair was analysed where possible. Of the 996 articles, only six (n = 6) clinical studies have described the use of BM-MSC in clinical applications. Two studies were cohort observational trials, three were case series, and one was a case report. In the two comparative trials, BM-MSCs produced superior repair to cartilage treatment without cells and have comparable outcomes to autologous chondrocyte implantation. The case series and case-control studies have demonstrated that use of BM-MSCs resulted in better short- to long-term clinical outcomes with minimal complications. In addition, histological analyses in two studies have resulted in good repair tissue formation at the damaged site, composed mainly of hyaline-like cartilage. Although results of the respective studies are highly indicative that BM-MSC-based therapy is superior, due to the differences in methods and selection criteria used, it was not possible to make direct comparison between the studies. In conclusion, published studies do suggest that BM-MSCs could provide superior cartilage repair. However, due to limited number of reports, more robust studies might be required before a definitive conclusion can be drawn.

The proliferation and tenogenic differentiation potential of bone marrow-derived mesenchymal stromal cell are influenced by specific uniaxial cyclic tensile loading conditions

It has been previously demonstrated that mechanical stimuli are important for multipotent human bone marrow-derived mesenchymal stromal cells (hMSCs) to maintain good tissue homeostasis and even to enhance tissue repair processes. In tendons, this is achieved by promoting the cellular proliferation and tenogenic expression/differentiation. The present study was conducted to determine the optimal loading conditions needed to achieve the best proliferation rates and tenogenic differentiation potential. The effects of mechanical uniaxial stretching using different rates and strains were performed on hMSCs cultured in vitro. hMSCs were subjected to cyclical uniaxial stretching of 4, 8 or 12 % strain at 0.5 or 1 Hz for 6, 24, 48 or 72 h. Cell proliferation was analyzed using alamarBlue[Formula: see text] assay, while hMSCs differentiation was analyzed using total collagen assay and specific tenogenic gene expression markers (type I collagen, type III collagen, decorin, tenascin-C, scleraxis and tenomodulin). Our results demonstrate that the highest cell proliferation is observed when 4 % strain [Formula: see text] 1 Hz was applied. However, at 8 % strain [Formula: see text] 1 Hz loading, collagen production and the tenogenic gene expression were highest. Increasing strain or rates thereafter did not demonstrate any significant increase in both cell proliferation and tenogenic differentiation. In conclusion, our results suggest that 4 % [Formula: see text] 1 Hz cyclic uniaxial loading increases cell proliferation, but higher strains are required for superior tenogenic expressions. This study suggests that selected loading regimes will stimulate tenogenesis of hMSCs.

Tissue-engineered cartilage: the crossroads of biomaterials, cells and stimulating factors

Damage to cartilage represents one of the most challenging tasks of musculoskeletal therapeutics due to its limited propensity for healing and regenerative capabilities. Lack of current treatments to restore cartilage tissue function has prompted research in this rapidly emerging field of tissue regeneration of functional cartilage tissue substitutes. The development of cartilaginous tissue largely depends on the combination of appropriate biomaterials, cell source, and stimulating factors. Over the years, various biomaterials have been utilized for cartilage repair, but outcomes are far from achieving native cartilage architecture and function. This highlights the need for exploration of suitable biomaterials and stimulating factors for cartilage regeneration. With these perspectives, we aim to present an overview of cartilage tissue engineering with recent progress, development, and major steps taken toward the generation of functional cartilage tissue. In this review, we have discussed the advances and problems in tissue engineering of cartilage with strong emphasis on the utilization of natural polymeric biomaterials, various cell sources, and stimulating factors such as biophysical stimuli, mechanical stimuli, dynamic culture, and growth factors used so far in cartilage regeneration. Finally, we have focused on clinical trials, recent innovations, and future prospects related to cartilage engineering.

Sirtuin-1 (SIRT1) is required for promoting chondrogenic differentiation of mesenchymal stem cells

Sirtuin-1 (SIRT1), NAD(+)-dependent deacetylase, has been linked to anabolic effects in cartilage, although the mechanisms of SIRT1 signaling during differentiation of mesenchymal stem cells (MSCs) to chondrocytes are poorly understood. Therefore, we investigated the role of SIRT1-mediated signaling during chondrogenic differentiation of MSCs in vitro. High density and alginate cultures of MSCs were treated with chondrogenic induction medium with/without the SIRT1 inhibitor nicotinamide, antisense oligonucleotides against SIRT1 (SIRT1-ASO), IL-1β, and/or resveratrol. Transient transfection of MSCs with SIRT1-antisense oligonucleotides, nicotinamide, and IL-1β inhibited chondrogenesis-induced down-regulation of cartilage-specific proteins, cartilage-specific transcription factor Sox9, and enhanced NF-κB-regulated gene products involved in the inflammatory and degradative processes in cartilage (MMP-9, COX-2, and caspase-3), and NF-κB phosphorylation, acetylation, and activation of IκBα kinase. In contrast, the SIRT1 activator resveratrol or BMS-345541 (inhibitor of IKK) inhibited IL-1β- and NAM-induced suppression of cartilage-specific proteins, Sox9, and up-regulation of NF-κB-regulated gene products. Moreover, SIRT1 was found to interact directly with NF-κB and resveratrol-suppressed IL-1β and NAM but not SIRT1-ASO-induced NF-κB phosphorylation, acetylation, and activation of IκBα kinase. Knockdown of SIRT1 by mRNA abolished the inhibitory effects of resveratrol on inflammatory and apoptotic signaling and Sox9 expression, suggesting the essential role of this enzyme. Finally, the modulatory effects of resveratrol were found to be mediated at least in part by the association between SIRT1 and Sox9. These results indicate for the first time that SIRT1 supports chondrogenic development of MSCs at least in part through inhibition/deacetylation of NF-κB and activation of Sox9.

The future role of mesenchymal stem cells in the management of shoulder disorders

PURPOSE

Biologics may help to optimize the healing environment after rotator cuff repair. Mesenchymal stem cells (MSCs) may have the potential to regenerate a physiological enthesis, thereby improving healing at the repair site after rotator cuff repair.

METHODS

The PubMed database was searched in May 2013. Only in vivo and in vitro studies reporting on stem cell use in the rotator cuff of humans or animals were included. Exclusion criteria consisted of the following: Level V evidence, systematic reviews, and studies reporting preliminary results.

RESULTS

This query resulted in 141 citations. Of these, 90 were excluded based on the title of the study. A final group of 17 studies was included in this review (9 in vivo animal studies, 5 in vitro human studies, 1 in vitro animal study, 1 study reporting in vitro human and in vivo animal results, and 1 study reporting on clinical outcomes of human patients).

CONCLUSIONS

The current literature regarding therapeutic use of MSCs in shoulder surgery is limited. Although in vivo animal studies have shown some promising approaches to enhance tendon-to-bone healing, the use of MSCs for shoulder surgery should still be regarded as an experimental technique. Further basic and clinical research is needed until a procedure can be defined for the routine use of these cells in shoulder surgery.

New insights into osteogenic and chondrogenic differentiation of human bone marrow mesenchymal stem cells and their potential clinical applications for bone regeneration in pediatric orthopaedics

Human mesenchymal stem cells (hMSCs) are pluripotent adult stem cells capable of being differentiated into osteoblasts, adipocytes, and chondrocytes. The osteogenic differentiation of hMSCs is regulated either by systemic hormones or by local growth factors able to induce specific intracellular signal pathways that modify the expression and activity of several transcription factors. Runt-related transcription factor 2 (Runx2) and Wnt signaling-related molecules are the major factors critically involved in the osteogenic differentiation process by hMSCs, and SRY-related high-mobility-group (HMG) box transcription factor 9 (SOX9) is involved in the chondrogenic one. hMSCs have generated a great interest in the field of regenerative medicine, particularly in bone regeneration. In this paper, we focused our attention on the molecular mechanisms involved in osteogenic and chondrogenic differentiation of hMSC, and the potential clinical use of hMSCs in osteoarticular pediatric disease characterized by fracture nonunion and pseudarthrosis.

Treatment of femoral head osteonecrosis with advanced cell therapy in sheep

BACKGROUND

The purpose of this study was to evaluate the efficacy of core decompression associated with advanced cell therapy for the treatment of femoral head osteonecrosis in an established sheep model.

METHODS

Early stage osteonecrosis of the right hip was induced cryogenically in 15 mature sheep. At 6 weeks, the sheep were divided into three groups, Group A: core decompression only; Group B: core decompression followed by implantation of an acellular bone matrix scaffold; Group C: core decompression followed by implantation of a cultured BMSC loaded bone matrix scaffold. At 12 weeks, MRI hip studies were performed and then the proximal femur was harvested for histological analysis.

RESULTS

In the group of advanced cell therapy, Group C, there was a tendency to higher values of the relative surface of newly formed bone with a mean of 20.3 versus 11.27 % in Group A and 13.04 % in Group B but it was not statistically significant. However, the mean relative volume of immature osteoid was 8.6 % in Group A, 14.97 in Group B, and 53.49 % in Group C (p < 0.05), revealing a greater capacity of osteoid production in the sheep treated with BMSCs. MRI findings were not conclusive due to constant bone edema artifact in all cases.

CONCLUSIONS

Our findings indicate that a BMCSs loaded bone matrix scaffold is capable of stimulating bone regeneration more effectively than isolated core decompression or in association with an acellular scaffold in a preclinical femoral head osteonecrosis model in sheep.

Effects of mechanical strain on human mesenchymal stem cells and ligament fibroblasts in a textured poly(L-lactide) scaffold for ligament tissue engineering

The purpose of this study was to prove the effect of cyclic uniaxial intermittent strain on the mRNA expression of ligament-specific marker genes in human mesenchymal stem cells (MSC) and anterior cruciate ligament-derived fibroblasts (ACL-fibroblasts) seeded onto a novel textured poly(L-lactide) scaffold (PLA scaffold). Cell-seeded scaffolds were mechanically stimulated by cyclic uniaxial stretching. The expression of ligament matrix gene markers: collagen types I and III, fibronectin, tenascin C and decorin, as well as the proteolytic enzymes matrix metalloproteinase MMP-1 and MMP-2 and their tissue specific inhibitors TIMP-1 and TIMP-2 was investigated by analysing the mRNA expression using reverse transcriptase polymerase chain reaction and related to the static control. In ACL-fibroblasts seeded on PLA, mechanical load induced up-regulation of collagen types I and III, fibronectin and tenascin C. No effect of mechanical stimulation on the expression of ligament marker genes was found in undifferentiated MSC seeded on PLA. The results indicated that the new textured PLA scaffold could transfer the mechanical load to the ACL-fibroblasts and improved their ligament phenotype. This scaffold might be suitable as a cell-carrying component of ACL prostheses.

Mesenchymal stem cell therapy in the sports knee: where are we in 2011?

Background:

The relationship between biological tissue healing following knee injury or surgery and long-term clinical outcome has come to the forefront of sports medicine practice. This has led many knee surgeons to incorporate biologically mediated healing factors into the management of knee injuries. In particular, the clinical use of mesenchymal stem cells has opened new horizons.

Evidence Acquisition:

Relevant studies were identified through a search of PubMed from January 2000 to April 2011, combining the term mesenchymal stem cells with articular cartilage, anterior cruciate ligament, and meniscus. Relevant citations from the reference lists of selected studies were also reviewed.

Results:

Knee injury treatment with mesenchymal stem cells shows potential. Most reports represent animal model studies; few advances have been translated to human clinical applications.

Conclusion:

Mesenchymal stem cell use to promote healing following knee injury is likely to increase. There are scientific methodological concerns and ethical and legal issues regarding mesenchymal stem cell use for treating knee injuries.

Effect of growth differentiation factor 5 on the proliferation and tenogenic differentiation potential of human mesenchymal stem cells in vitro

The use of growth differentiation factor 5 (GDF-5) in damaged tendons has been shown to improve tendon repair. It has been hypothesized that further improvements may be achieved when GDF-5 is used to promote cell proliferation and induce tenogenic differentiation in human bone marrow-derived mesenchymal stem cells (hMSCs). However, the optimal conditions required to produce these effects on hMSCs have not been demonstrated in previous studies. A study to determine cell proliferation and tenogenic differentiation in hMSCs exposed to different concentrations of GDF-5 (0, 5, 25, 50, 100 and 500 ng/ml) was thus conducted. No significant changes were observed in the cell proliferation rate in hMSCs treated at different concentrations of GDF-5. GDF-5 appeared to induce tenogenic differentiation at 100 ng/ml, as reflected by (1) a significant increase in total collagen expression, similar to that of the primary native human tenocyte culture; (2) a significant upregulation in candidate tenogenic marker gene expression, i.e. scleraxis, tenascin-C and type-I collagen; (3) the ratio of type-I collagen to type-III collagen expression was elevated to levels similar to that of human tenocyte cultures, and (4) a significant downregulation of the non-tenogenic marker genes runt-related transcription factor 2 and sex determining region Y (SRY)-box 9 at day 7 of GDF-5 induction, further excluding hMSC differentiation into other lineages. In conclusion, GDF-5 does not alter the proliferation rates of hMSCs, but, instead, induces an optimal tenogenic differentiation response at 100 ng/ml.

Tissue engineering interventions for esophageal disorders--promises and challenges

The diseases of the esophagus include congenital defects like atresia, tracheoesophageal fistula as well as others such as gastro-esophageal reflux disease (GERD), Barrett's esophagus, carcinoma and strictures. All esophageal disorders require surgical intervention and reconstruction with appropriate substitutes. Primary anastomosis is used to treat most cases but treatment of long gap atresia still remains a clinical challenge. Autologous graft therapies using tissues from colon, and small and large intestine or gastric transplantations have been attempted but have constraints like leakage, infection and stenosis at the implanted site, which leads to severe morbidity and mortality. An alternative for autologous grafts are allogenic and xenogenic grafts, which have better availability but disease transmission and immunogenicity limit their applications. Use of biodegradable and biocompatible scaffolds to engineer the esophagus promises to be an effective regenerative strategy for treatment of esophageal disorders. Nanotopography of the fibrous scaffolds mimics the natural extracellular matrix (ECM) of the tissue and incorporation of chemical cues and tailoring mechanical properties provide the right microenvironment for co-culture of different cell types. Scaffolds cultured with esophageal cells (epithelial cells, fibroblast and smooth muscle cells) might show enhancement of the biofunctionality in vivo. This review attempts to address the various strategies and challenges involved in successful tissue engineering of the esophagus.

Effect of a CCR1 receptor antagonist on systemic trafficking of MSCs and polyethylene particle-associated bone loss

Particle-associated periprosthetic osteolysis remains a major issue in joint replacement. Ongoing bone loss resulting from wear particle-induced inflammation is accompanied by continued attempts at bone repair. Previously we showed that mesenchymal stem cells (MSCs) are recruited systemically to bone exposed to continuous infusion of ultra high molecular weight polyethylene (UHMWPE) particles. The chemokine-receptor axis that mediates this process is unknown. We tested two hypotheses: (1) the CCR1 receptor mediates the systemic recruitment of MSCs to UHMWPE particles and (2) recruited MSCs are able to differentiate into functional mature osteoblasts and decrease particle-associated bone loss. Nude mice were allocated randomly to four groups. UHMWPE particles were continuously infused into the femoral shaft using a micro-pump. Genetically modified murine wild type reporter MSCs were injected systemically via the left ventricle. Non-invasive imaging was used to assay MSC migration and bone mineral density. Bioluminescence and immunohistochemistry confirmed the chemotaxis of reporter cells and their differentiation into mature osteoblasts in the presence of infused particles. Injection of a CCR1 antagonist decreased reporter cell recruitment to the UHMWPE particle infusion site and increased osteolysis. CCR1 appears to be a critical receptor for chemotaxis of MSCs in the presence of UHMWPE particles. Interference with CCR1 exacerbates particle-induced bone loss.

Physiological cartilage tissue engineering effect of oxygen and biomechanics

In vitro engineering of cartilaginous tissues has been studied for many years, and tissue-engineered constructs are sought to be used clinically for treating articular cartilage defects. Even though there is a plethora of studies and data available, no breakthroughs have been achieved yet that allow for implanting in vivo cultured articular cartilaginous tissues in patients. A review of contributions to cartilage tissue engineering over the past decades emphasizes that most of the studies were performed under environmental conditions neglecting the physiological situation. This is specifically pronounced in the use of bioreactor systems which neither allow for application of near physiomechanical stimulations nor for controlling a hypoxic environment as it is experienced in synovial joints. It is suspected that the negligence of these important parameters has slowed down progress and prevented major breakthroughs in the field. This review focuses on the main aspects of cartilage tissue engineering with emphasis on the relation and understanding of employing physiological conditions.

High abundance of CD271(+) multipotential stromal cells (MSCs) in intramedullary cavities of long bones

Aspiration of iliac crest bone marrow (ICBM) remains the most frequent technique used in harvesting multipotential stromal cells (MSCs) for bone regeneration. Although this tissue type is easily accessed by a surgeon, it has a low frequency of MSCs, which is significant given the high cell numbers required for bone regeneration strategies. Lipoaspirates possess higher MSC frequencies, albeit cells with a differentiation profile less suited to orthopaedic interventions. Intra-medullary cavities of long bones have previously been shown to harbour MSCs in animals, however evaluation of their frequency, differentiation capacity and phenotype in humans had not previously been performed. Long bone fatty bone marrow (LBFBM) was collected prior to harvesting bone graft. Basic cellular compositions of donor-matched LBFBM and ICBM aspirates, including the numbers of CD34(+) hematopoietic stem cells and CD31(+) endothelial cells, were similar. MSCs were enumerated using colony-forming-unit-fibroblast assays and flow cytometry for the presence of a resident LBFBM CD45(-/low) CD271(+) MSC population and revealed a trend for higher MSC numbers (average 5 fold, n=6) per millilitre of LBFBM compared to donor-matched ICBM. Functional characteristics of resident MSCs, including their growth rates, differentiation potentials and surface phenotypes (CD73(+)CD105(+)CD90(+)) before and after culture-amplification, were similar. Enhanced numbers of MSCs could be recovered following brief enzymatic treatment of solid fragments of LBFBM. Our findings therefore reveal that the intramedullary cavity of the human femur is a depot of MSCs, which, although closely associated with fat, have a differentiation profile equivalent to ICBM. This anatomical site is frequently accessed by the orthopaedic/trauma surgeon and aspiration of the intramedullary cavity represents a 'low-tech' method of harvesting potentially large numbers of MSCs for regenerative therapies and research.

New Frontiers for Cartilage Repair and Protection

OBJECTIVE

Articular cartilage injury is common after athletic injury and remains a difficult treatment conundrum both for the surgeon and athlete. Although recent treatments for damage to articular cartilage have been successful in alleviating symptoms, more durable and complete, long-term articular surface restoration remains the unattained goal. In this article, we look at both new ways to prevent damage to articular surfaces as well as new techniques to recreate biomechanically sound and biochemically true articular surfaces once an athlete injures this surface. This goal should include reproducing hyaline cartilage with a well-integrated and flexible subchondral base and the normal zonal variability in the articular matrix.

RESULTS

A number of nonoperative interventions have shown early promise in mitigating cartilage symptoms and in preclinical studies have shown evidence of chondroprotection. These include the use of glucosamine, chondroitin, and other neutraceuticals, viscosupplementation with hyaluronic acid, platelet-rich plasma, and pulsed electromagnetic fields. Newer surgical techniques, some already in clinical study, and others on the horizon offer opportunities to improve the surgical restoration of the hyaline matrix often disrupted in athletic injury. These include new scaffolds, single-stage cell techniques, the use of mesenchymal stem cells, and gene therapy.

CONCLUSION

Although many of these treatments are in the preclinical and early clinical study phase, they offer the promise of better options to mitigate the sequelae of athletically induced cartilage.

The potential of stem cells in the treatment of skeletal muscle injury and disease

Tissue engineering is a pioneering field with huge advances in recent times. These advances are not only in the understanding of how cells can be manipulated but also in potential clinical applications. Thus, tissue engineering, when applied to skeletal muscle cells, is an area of huge prospective benefit to patients with muscle disease/damage. This could include damage to muscle from trauma and include genetic abnormalities, for example, muscular dystrophies. Much of this research thus far has been focused on satellite cells, however, mesenchymal stem cells have more recently come to the fore. In particular, results of trials and further research into their use in heart failure, stress incontinence, and muscular dystrophies are eagerly awaited. Although no doubt, stem cells will have much to offer in the future, the results of further research still limit their use.

The effect of the addition of adipose-derived mesenchymal stem cells to a meniscal repair in the avascular zone: an experimental study in rabbits

PURPOSE

To determine whether adipose-derived mesenchymal stem cells (ASCs) affect the healing rate of meniscal lesions sutured in the avascular zone in rabbits.

METHODS

Four groups were used. In group A (n = 12) a short, 5-mm-long longitudinal lesion in the avascular zone of the anterior horn of the medial meniscus was created and immediately sutured. In group B (n = 8) the same short lesion was created but suture was delayed 3 weeks. In group C (n = 12) a larger, 15-mm-long lesion that spanned the whole meniscus was created and sutured immediately. In group D (n = 8) the same large lesion was sutured 3 weeks later. Both knees in each rabbit were used: 1 served as the control, and in the other, 1 × 10(5) allogeneic ASCs marked with bromodeoxyuridine were placed in the lesion immediately before suturing. The animals were killed at 12 weeks.

RESULTS

In group A (short lesion, acute repair) 6 of 12 ASC-treated menisci and 0 of 12 controls had some healing (P = .014). In group B (short lesion, delayed repair) 2 of 8 ASC-treated menisci and 1 of 8 controls had some healing (P = .5). In group C (long lesion, acute repair) 6 of 12 ASC-treated menisci and 0 of 12 controls had some healing (P = .014). In group D (long lesion, delayed repair) 4 of 8 ASC-treated menisci and 0 of 8 controls had some healing (P = .07). The addition of ASCs increased the healing rate (odds ratio, 32 [range, 3.69 to 277]; P = .002). The histologic analysis of the healed zones identified well-formed meniscal fibrocartilage with persistence of cells derived from the ASCs (immunolocated with anti-bromodeoxyuridine antibodies).

CONCLUSIONS

Adding ASCs to a repair in the avascular zone of rabbit menisci increases the chances of healing. Healing is improved in small and larger lesions. When suture is delayed, the effect is not as evident.

CLINICAL RELEVANCE

In the future, ASCs might help in meniscal repair in the avascular zone.

Potential of human embryonic stem cells in cartilage tissue engineering and regenerative medicine

The current surgical intervention of using autologous chondrocyte implantation (ACI) for cartilage repair is associated with several problems such as donor site morbidity, de-differentiation upon expansion and fibrocartilage repair following transplantation. This has led to exploration of the use of stem cells as a model for chondrogenic differentiation as well as a potential source of chondrogenic cells for cartilage tissue engineering and repair. Embryonic stem cells (ESCs) are advantageous, due to their unlimited self-renewal and pluripotency, thus representing an immortal cell source that could potentially provide an unlimited supply of chondrogenic cells for both cell and tissue-based therapies and replacements. This review aims to present an overview of emerging trends of using ESCs in cartilage tissue engineering and regenerative medicine. In particular, we will be focusing on ESCs as a promising cell source for cartilage regeneration, the various strategies and approaches employed in chondrogenic differentiation and tissue engineering, the associated outcomes from animal studies, and the challenges that need to be overcome before clinical application is possible.

The use of the reamer-irrigator-aspirator to harvest mesenchymal stem cells

The scarcity of mesenchymal stem cells (MSCs) in iliac crest bone marrow aspirate (ICBMA), and the expense and time in culturing cells, has led to the search for alternative harvest sites. The reamer-irrigation-aspirator (RIA) provides continuous irrigation and suction during reaming of long bones. The aspirated contents pass via a filter, trapping bony fragments, before moving into a 'waste' bag from which MSCs have been previously isolated. We examined the liquid and solid phases, performed a novel digestion of the solid phase, and made a comparative assessment in terms of number, phenotype and differentiation capacity with matched ICBMA. The solid fraction from the filtrate was digested for 60 minutes at 37° C with collagenase. Enumeration was performed via the colony-forming unit fibroblast (CFU-F) assay. Passage (P2) cells were differentiated towards osteogenic, adipogenic and chondrogenic lineages, and their phenotypes assessed using flow cytometry (CD33, CD34, CD45, CD73, CD90, and CD105). MSCs from the RIA phases were able to differentiate at least as well as those from ICBMA, and all fractions had phenotypes consistent with other established sources. The median number of colonies for the three groups was: ICBMA = 8.5 (2 to 86), RIA-liquid = 19.5 (4 to 90), RIA-solid = 109 (67 to 200) per 200 μl. The mean total yield of cells for the three groups was: ICBMA = 920 (0 to 4275), RIA-liquid = 114,983 (16,500 to 477,750), RIA-solid = 12,785 (7210 to 28 475). The RIA filtrate contains large numbers of MSCs that could potentially be extracted without enzymatic digestion and used for bone repair without prior cell expansion.