Bone Marrow Aspirate Concentrate for the Treatment of Avascular Meniscus Tears in a One-Step Procedure-Evaluation of an In Vivo Model

Current practice of biologic augmentation techniques to enhance the healing of meniscal repairs: A collaborative survey within the Meniscus International Network (MenIN) Study Group

PURPOSE

To evaluate practices and preferences among expert sports knee surgeons regarding biologic augmentation techniques in meniscal repair.

METHODS

A 12-question multiple-choice survey was distributed to the Meniscus International Network (MenIN) Study Group. It covered biologic augmentation techniques for various meniscal tear types, both in isolation and with anterior cruciate ligament reconstruction (ACLR). Eight options were assessed: no augmentation, trephination, rasping, marrow venting, fibrin clot, platelet-rich plasma (PRP), bone marrow aspirate concentrate (BMAC) and meniscal wrapping. Surgeons could select multiple techniques per scenario.

RESULTS

Forty-two surgeons participated: 42% from Europe, 18% from North America, 10% from Latin America, 21% from Asia and 9% from Africa/Oceania. For isolated meniscal tears (excluding meniscal root tears), 90% of surgeons used at least one biologic augmentation technique. For meniscal tears associated with ACLR, 66% of surgeons used at least one biologic augmentation technique. The most utilized techniques were rasping (19%-69%), trephination (7%-43%), and marrow venting (0%-74%). PRP (2%-19%), BMAC (0%-14%) and meniscal wrapping (0%-10%) were least used. Biologic augmentation was most frequent for isolated radial (93%), isolated bucket-handle (86%), isolated vertical (86%) and isolated horizontal tears (98% for younger patients, 86% for degenerative tears). ACLR-associated repairs had lower augmentation rates, and meniscal root tears showed the highest percentage of non-augmented repairs. Over 50% of surgeons use a single augmentation technique, while 20% use two techniques depending on tear type. Overall, 33.3% (n = 14) of surgeons reported utilizing PRP and/or BMAC for meniscal repair augmentation, with the highest use observed in South America (12%) based on geographic usage.

CONCLUSIONS

This survey provides insights into current meniscal repair practices among expert orthopaedic sports medicine surgeons. The findings reveal variability in approaches based on tear patterns and associated procedures, with a general preference for simpler mechanical augmentation techniques over more advanced biologics. For isolated meniscal tears (excluding meniscal root tears), 90% of surgeons in this cohort report using one or more biological augmentation techniques.

LEVEL OF EVIDENCE

Level V expert opinion.

Research Progress of Bone Grafting: A Comprehensive Review

Bone tissue, the second most transplanted tissue after blood, is utilized in over 2.2 million bone grafts annually to address various bone-related conditions including fractures, tumors, bone infections, scoliosis, congenital defects, osteoporosis, osteoarthritis, and osteogenesis imperfecta. According to incomplete statistics, $4.3 billion was spent on bone graft materials in 2015 alone, with projections suggesting this figure may reach $66 billion by 2026. The limited availability of autogenous bone graft considered the gold standard due to their three critical biological properties: osteoconduction, osteoinduction, and osteogenesis-alongside the increasing global aging population, may be contributing to this rising expenditure. Furthermore, advancements in biomaterials and engineering technologies have created opportunities for the exploration of new bone graft substitutes. In this review, we will examine the fundamental structure of natural bone and the characteristics of ideal bone graft, highlighting common bone graft materials currently available, such as true bone ceramics, decalcified bone matrix, freeze-dried bone and demineralized freeze-dried bone, bioactive glasses, bone marrow aspirate concentrate, polymer nanocomposites, which have different characteristics in osteogenic, osteoconductivity, osteoinductivity, biocompatibility, mechanical properties, and resorption. How to utilize its advantages to maximize the osteogenic effect will be the focus of this review, and some of the current challenges in the field of bone grafting will be identified, outlining potential directions for future development. In conclusion, the choice of bone graft is critical to bone repair and regeneration, and a comprehensive understanding of the advantages and disadvantages of bone graft materials can improve the effectiveness of related surgical interventions.

Current advances in animal model of meniscal injury: From meniscal injury to osteoarthritis

Meniscal injury is a prevalent orthopedic practice that causes articular cartilage wear and degeneration due to tissue damage or loss, and may eventually result in the occurrence of knee osteoarthritis (KOA). Hence, investigating the structural regeneration and mechanical function restoration of the meniscus after injury is pivotal research topic for preventing KOA. Animal models are essential for investigating therapeutic strategies for meniscal injuries and their clinical translation, yet no current model can fully recapitulate the complexity of human meniscal injuries. This review aims to categorize the prevalent animal models of meniscal injury by their establishment methods, elucidate their principles and procedures, and discuss the suitability and limitations of each model. We delineate the pros and cons of different models in simulating the pathology and biomechanics of human meniscal injury. We also analyze different animal species regarding their meniscal structure, function, and repair potential, and their implications for model selection. We conclude that selecting an appropriate animal model requires a comprehensive consideration of various factors, such as research aims, anticipated outcomes, and feasibility. Furthermore, to translate novel therapeutic approaches to clinical applications more safely and effectively, future model development should emphasize aspects such as choosing animals of suitable age. The Translational Potential of this Article: This review aims to categorize and discuss current animal models of meniscal injury by establishment methods and provides a comprehensive overview of the routinely employed experimental animals in each model to facilitate the clinical translation of OA-related research.

A Prospective, Randomized, Double-Blind Clinical Trial to Investigate the Efficacy of Autologous Bone Marrow Aspirate Concentrate During Arthroscopic Meniscectomy in Patients With Early Knee Osteoarthritis

BACKGROUND

Despite being recognized as a safe procedure with minimal reported complications, injecting autologous bone marrow aspirate concentrate (BMAC) as an adjuvant to arthroscopic partial meniscectomy (APM) for symptomatic patients with meniscal tears and concomitant knee osteoarthritis (OA) has not been studied in randomized controlled trials.

PURPOSE

To compare patient-reported outcome measure (PROM) scores and radiographic outcomes in symptomatic patients with meniscal tears and concomitant mild knee OA who underwent APM with and without an autologous BMAC injection administered at the time of surgery.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

Enrolled patients aged ≥18 years determined to have a symptomatic meniscal tear with concomitant mild knee OA suitable for APM and meeting inclusion and exclusion criteria were randomized into 2 groups: BMAC and control (no BMAC). The primary endpoint of the study was the International Knee Documentation Committee (IKDC) score at 1 year postoperatively. Secondary endpoints included radiographic outcomes (Kellgren-Lawrence grade) at 1 year postoperatively and various PROM scores, including those for the IKDC, Knee injury and Osteoarthritis Outcome Score (KOOS), visual analog scale, and Veterans RAND 12-Item Health Survey, at 3 months, 6 months, 1 year, and 2 years after meniscectomy.

RESULTS

Of the 95 enrolled patients, 83 (87.4%) were included for final analysis. No significant differences were found between the groups with regard to patient characteristics, intraoperative variables, concomitant procedures, preoperative PROM scores, or preoperative radiographic findings. At 1 year postoperatively, the BMAC group failed to demonstrate significantly better IKDC scores (P = .687) or radiographic outcomes (P > .05 for all radiographic measures) compared with the control group. Secondary PROM scores also did not significantly differ between the groups (P > .05 for all PROMs). However, there were higher achievement rates of the minimal clinically important difference for the KOOS Sport (100.0% vs 80.0%, respectively; P = .023) and KOOS Symptoms (92.3% vs 68.0%, respectively; P = .038) at 1 year postoperatively in the BMAC group than in the control group. All PROMs, excluding the VR-12 mental score, showed significant improvements compared with baseline at all postoperative time points for both the BMAC and control groups.

CONCLUSION

The addition of an autologous BMAC injection during APM did not result in significant changes in IKDC scores or radiographic outcomes at the 1-year postoperative mark. Secondary PROM scores were generally comparable between the 2 groups, but there was higher minimal clinically important difference achievement for the KOOS Sport and KOOS Symptoms at 1 year postoperatively in the BMAC group. In patients with symptoms consistent with a meniscal tear who had concomitant mild OA, the addition of BMAC to arthroscopic debridement did not affect the outcome.

REGISTRATION

NCT02582489 (ClinicalTrials.gov).

Development of a novel approach for restoration of the meniscus using silk-elastin in a rabbit meniscus injury model

BACKGROUND

Limited healing potential of the meniscus remains a burden for the successful repair of meniscus injuries in the orthopaedic fields. Silk-elastin (SE) is a novel recombinant protein with favorable properties for wound healing. This proof-of-concept study aimed to investigate the therapeutic effect of silk-elastin in a rabbit meniscal defect model.

METHODS

A migration assay using rabbit meniscus and synovial cells with various concentrations of SE in a culture medium was conducted to investigate the mechanism of meniscal healing by SE. Additionally, cylindrical defects with a 1.5 mm diameter were created at the anterior horn of the medial meniscus of rabbits. The animals were divided into three groups: 1) the Blank group; defect only, 2) the Col I group; implantation of type I atelocollagen sponge, and 3) the SE group; implantation of SE (150 mg/ml) sponge. Whole medial menisci were harvested at 4, 8, 12, and 24 weeks after surgery. Histological analyses including immunohistochemical staining were performed to assess meniscal healing.

RESULTS

In vitro study, Migration assay demonstrated a significantly higher number of migrated cells only in synovial cells. Especially, the SE concentration of 10 µg/mL demonstrated the highest number of migrated cells compared with other concentrations. In vivo study, the SE group exhibited significantly higher Ishida scores than other groups at all time points. Furthermore, the SE group showed higher synovial coverage scores than the Col I group at 4 and 8 weeks. Immunohistochemical staining demonstrated higher type II collagen staining in the SE group compared to other groups at 12 weeks. Implanted SE was efficiently replaced by safranin-O staining positive tissue within 8 weeks.

CONCLUSIONS

SE could effectively repair a meniscal defect by inducing coverage of synovial cells. SE has the potential to be a useful material for meniscal repair.

Bone Marrow Aspirate Concentrate Combined with Ultra-Purified Alginate Bioresorbable Gel Enhances Intervertebral Disc Repair in a Canine Model: A Preclinical Proof-of-Concept Study

Although discectomy is commonly performed for lumbar intervertebral disc (IVD) herniation, the capacity for tissue repair after surgery is limited, resulting in residual lower back pain, recurrence of IVD herniation, and progression of IVD degeneration. Cell-based therapies, as one-step procedures, are desirable for enhancing IVD repair. This study aimed to investigate the therapeutic efficacy of a combination of newly developed ultra-purified alginate (UPAL) gel and bone marrow aspirate concentrate (BMAC) implantation for IVD repair after discectomy. Prior to an in vivo study, the cell concentration abilities of three commercially available preparation kits for creating the BMAC were compared by measuring the number of bone marrow mesenchymal stem cells harvested from the bone marrow of rabbits. Subsequently, canine-derived BMAC was tested in a canine model using a kit which had the highest concentration rate. At 24 weeks after implantation, we evaluated the changes in the magnetic resonance imaging (MRI) signals as well as histological degeneration grade and immunohistochemical analysis results for type II and type I collagen-positive cells in the treated IVDs. In all quantitative evaluations, such as MRI and histological and immunohistochemical analyses of IVD degeneration, BMAC-UPAL implantation significantly suppressed the progression of IVD degeneration compared to discectomy and UPAL alone. This preclinical proof-of-concept study demonstrated the potential efficacy of BMAC-UPAL gel as a therapeutic strategy for implementation after discectomy, which was superior to UPAL and discectomy alone in terms of tissue repair and regenerative potential.

Current advances in engineering meniscal tissues: insights into 3D printing, injectable hydrogels and physical stimulation based strategies

The knee meniscus is the cushioning fibro-cartilage tissue present in between the femoral condyles and tibial plateau of the knee joint. It is largely avascular in nature and suffers from a wide range of tears and injuries caused by accidents, trauma, active lifestyle of the populace and old age of individuals. Healing of the meniscus is especially difficult due to its avascularity and hence requires invasive arthroscopic approaches such as surgical resection, suturing or implantation. Though various tissue engineering approaches are proposed for the treatment of meniscus tears, three-dimensional (3D) printing/bioprinting, injectable hydrogels and physical stimulation involving modalities are gaining forefront in the past decade. A plethora of new printing approaches such as direct light photopolymerization and volumetric printing, injectable biomaterials loaded with growth factors and physical stimulation such as low-intensity ultrasound approaches are being added to the treatment portfolio along with the contemporary tear mitigation measures. This review discusses on the necessary design considerations, approaches for 3D modeling and design practices for meniscal tear treatments within the scope of tissue engineering and regeneration. Also, the suitable materials, cell sources, growth factors, fixation and lubrication strategies, mechanical stimulation approaches, 3D printing strategies and injectable hydrogels for meniscal tear management have been elaborated. We have also summarized potential technologies and the potential framework that could be the herald of the future of meniscus tissue engineering and repair approaches.

Single-Dose Radial Extracorporeal Shock Wave Therapy Modulates Inflammation During Meniscal Tear Healing in the Avascular Zone

BACKGROUND

Extracorporeal shock wave therapy (ESWT) promotes tissue healing by modulating inflammation, which has implications for meniscal tear healing in the avascular zone.

PURPOSE

To evaluate the effects of a single dose of radial ESWT on the healing process and inflammation of the meniscus and knee joints after meniscal tears in the avascular zone.

STUDY DESIGN

Controlled laboratory study.

METHODS

Avascular tears were induced in the medial meniscus (MM) of 72 Sprague-Dawley rats. One week postoperatively, the rats received a single session of radial ESWT with a Power+ handpiece (ESWT group; n = 36) or with a fake handpiece (sham-ESWT group; n = 36). The rats were then euthanized at 2, 4, or 8 weeks postoperatively. The MMs were harvested for analysis of healing (hematoxylin-eosin, safranin O-Fast Green, and collagen type 2 staining) and inflammation (interleukin [IL]-1β and IL-6 staining). Lateral menisci and synovia were obtained to evaluate knee joint inflammation (enzyme-linked immunosorbent assay of IL-1β and IL-6). Cartilage degeneration was assessed in the femurs and tibial plateaus using safranin O-Fast Green staining.

RESULTS

The ESWT group showed significantly better meniscal healing scores than the sham-ESWT group at 4 (P = .0066) and 8 (P = .0050) weeks postoperatively. The IL-1β level was significantly higher in the sham-ESWT group than in the ESWT group at 2 (MM: P = .0009; knee joint: P = .0160) and 8 (MM: P = .0399; knee joint: P = .0001) weeks. The IL-6 level was significantly lower in the sham-ESWT group than in the ESWT group at 2 (knee joint: P = .0184) and 4 (knee joint: P = .0247) weeks but higher at 8 weeks (MM: P = .0169; knee joint: P = .0038). The sham group had significantly higher osteoarthritis scores than the ESWT group at 4 (tibial plateau: P = .0157) and 8 (femur: P = .0048; tibial plateau: P = .0359) weeks.

CONCLUSION

A single dose of radial ESWT promoted meniscal tear healing in the avascular zone, modulated inflammatory factors in the menisci and knee joints in rats, and alleviated cartilage degeneration.

CLINICAL RELEVANCE

Radial ESWT can be considered a potential option for improving meniscal tear healing in the avascular zone because of its ability to modulate inflammation.

Molecular Biology of Meniscal Healing: A Narrative Review

This review provides insights at the molecular level into the current and old methods for treating meniscal injuries. Meniscal injuries have been found to have a substantial impact on the progression of osteoarthritis. In line with the "save the meniscus" approach, meniscectomy is considered a last-resort treatment. Nevertheless, it is important to note that mechanical repair alone may not achieve the complete restoration of the meniscus. A deep understanding of the healing pathways could lead to future improvements in meniscal healing. The inclusion of cytokines and chemokines has the potential to facilitate the process of tear repair or impede the inflammatory catabolic cascade. MicroRNA (miRNA) could serve as a potential biomarker for meniscal degeneration, and RNA injections might promote collagen and growth factor production. The critical aspect of the healing process is angiogenesis within the inner zone of the meniscus. The use of collagen scaffolds and the implantation of autologous meniscus fragments have been successfully integrated into clinical settings. These findings are encouraging and underscore the need for well-designed clinical trials to explore the most effective factors that can enhance the process of meniscal repair.

Meniscus Allograft Transplantation Augmented With Autologous Bone Marrow Aspirate Concentrate

Meniscus allograft transplantation (MAT) has been shown to be a feasible surgical option for younger patients, below 50 years of age who have meniscal insufficiency and have failed conservative treatment measures. In this technical note, we describe a procedure of harvesting and injecting bone marrow aspirate concentrate in a meniscus allograft during a MAT procedure, which may allow for longer lasting transplants and improve patient outcomes. In this technical note, bone marrow aspirate concentrate is harvested arthroscopically from the intercondylar notch at the surgical site, which prevents additional donor site morbidity, as seen with harvesting from other locations, such as the iliac crest. This also reduces operating time, since harvesting from the iliac crest requires different patient positioning and usually additional anesthesia. The authors of this surgical technique believe that biological augmentation during MATs will assist surgeons in maximizing graft survivorship and, ultimately, lead to better patient outcomes.

Bone Marrow-Derived Fibrin Clots Stimulate Healing of a Meniscal Defect in a Rabbit Model

PURPOSE

To determine the in vivo effectiveness of bone marrow aspirate-derived (BMA) fibrin clots for avascular meniscal defect healing in a rabbit model.

METHODS

In 42 Japanese white rabbits, a 2.0-mm cylindrical defect was introduced into the avascular zone of the anterior part of the medial meniscus in the bilateral knees. The rabbits were grouped according to implantation of a BMA fibrin clot (BMA group) or a peripheral blood (PB)-derived clot (PB group) into the defect and nonimplantation (control group). Macroscopic and histological assessments were performed using a scoring system at 4 and 12 weeks after surgery. At 12 weeks after surgery, compressive stress was analyzed biomechanically.

RESULTS

The meniscal score in the BMA group (12.1) was greater than that in the PB group (5.5; P = .031) and control group (4.4; P = .013) at 4 weeks. The meniscal score in the BMA group (13.1) was greater than that in the control group (6.4; BMA = 13.1; P = .0046) at 12 weeks. In the biomechanical analysis, the BMA group demonstrated significantly higher compressive strength than the PB group (6.6 MPa) (BMA = 15.4 MPa; P = .0201) and control group (3.6 MPa; BMA = 15.4 MPa; P = .007).

CONCLUSIONS

Implantation of BMA fibrin clots into the meniscal defect of the avascular zone in a rabbit model improved the meniscal score at 4 weeks and strengthened the reparative meniscal tissue at 12 weeks compared with the implantation of PB fibrin clots.

CLINICAL RELEVANCE

Healing in the avascular zone of the meniscus can be problematic. Approaches to improving this healing response have had variable results. This study provides additional information that may help improve the outcomes in patients with these injuries.

The Current Role of Biologics for Meniscus Injury and Treatment

PURPOSE OF REVIEW

There is little doubt that the consensus has changed to favor preservation of meniscal function where possible. Accordingly, the indications for meniscal repair strategies have been refocused on the long-term interest of knee joint health. The development and refinements in surgical technique have been complemented by biological augmentation strategies to address intrinsic challenges in healing capacity of meniscal tissue, with variable effects.

RECENT FINDINGS

A contemporary approach to meniscal healing includes adequate surgical fixation, meniscal and synovial tissue stimulation, and management of the intraarticular milieu. Overall, evidence supporting the use of autogenous or allogeneic cell sources remains limited. The use of FDA-approved medications to effect biologically favorable mechanisms during meniscal healing holds promise. Development and characterization of biologics continue to advance with translational research focused on specific growth factors, cell and tissue behaviors in meniscal healing, and joint homeostasis. Although significant strides have been made in laboratory and pre-clinical studies, translation to clinical application remains challenging. Finally, expert consensus and standardization of nomenclature related to orthobiologics for meniscal preservation will be important for the advancement of this field.

Regeneration of meniscal avascular zone using autogenous meniscal fragments in a rabbit model

Background

To investigate the effects of autologous meniscus fragment (AMF) implantation on injury in the meniscal avascular zone in mature rabbits.

Methods

Adult New Zealand white rabbits were randomly divided into two groups. Massive one-piece meniscus tissue was implanted in situ as control. In the experimental group, AMF was used to repair the meniscal injury in the avascular zone. Meniscal damage was assessed by gross observation of the degree of healing and histological semi-quantitative evaluation within 12 weeks postoperatively. The healing of meniscus interface was assessed by gross observation semiquantitative scoring and microscopic examination hematoxylin and eosin (H&E) staining at 2, 4, 8, and 12 weeks after surgery. The expressions of proliferating cell nuclear antigen (PCNA), collagen type I (COL1A1), and collagen type II (COL2) were detected by immunohistochemical staining.

Results

The degree of healing in the AMF group showed a significant increase over time (P < 0.05); the AMF group showed higher gross scores than the control group at 4, 8, and 12 weeks after surgery (P < 0.05). The histological scores in the AMF group were significantly higher than those in the control group at 4, 8, and 12 weeks after surgery (P < 0.05). The protein expression of PCNA in the AMF group was greater than that in the control group at 2, 4, and 8 weeks after surgery (P < 0.05). In addition, compared with the control group, the protein levels of COL1A1 and COL2 were significantly upregulated at each time-point. At 2 and 4 weeks after surgery, the expression level of COL1A1 increased in both groups followed by a gradual decrease after 8 weeks (P < 0.05). At 2, 4, 8, and 12 weeks after surgery, the expression levels of COL2 showed a gradual decrease in both groups (P < 0.05).

Conclusions

Our study demonstrated that the AMF method can promote the repair of rabbit meniscal injury in the avascular zone, and this method may potentially be used for clinical application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12893-022-01663-3.

Meniscus repair: up-to-date advances in stem cell-based therapy

The meniscus is a semilunar fibrocartilage between the tibia and femur that is essential for the structural and functional integrity of the keen joint. In addition to pain and knee joint dysfunction, meniscus injuries can also lead to degenerative changes of the knee joint such as osteoarthritis, which further affect patient productivity and quality of life. However, with intrinsic avascular property, the tearing meniscus tends to be nonunion and the augmentation of post-injury meniscus repair has long time been a challenge. Stem cell-based therapy with potent regenerative properties has recently attracted much attention in repairing meniscus injuries, among which mesenchymal stem cells were most explored for their easy availability, trilineage differentiation potential, and immunomodulatory properties. Here, we summarize the advances and achievements in stem cell-based therapy for meniscus repair in the last 5 years. We also highlight the obstacles before their successful clinical translation and propose some perspectives for stem cell-based therapy in meniscus repair.

Lateral Meniscus Allograft Transplantation in Combination with BMAC (Bone Marrow Aspirate Concentrate) Injection: Biologic Augmentation of the Allograft

Meniscal allograft transplantation (MAT) has proven successful in relieving joint pain and providing functional improvement in patients who have undergone subtotal or total meniscectomy. Bone marrow aspirate concentrate (BMAC) is a biological adjuvant that was shown in the literature to be effective in treating cartilage damage and muscle-tendon tissue problems. The aim of the study is the concomitant use of MAT and BMAC, which are both considered biological treatments and would be beneficial in clinical practice.

Regenerative Potential of Solid Bone Marrow Aspirate Concentrate Compared to Platelet-Rich Fibrin

Platelet-rich fibrin (PRF) prepared from venous blood is used in the clinic to improve soft tissue wound healing. Nevertheless, arterial blood or bone marrow aspirate might also be a candidate for the source of PRF-like concentrates. The purpose of the present study was to investigate blood/bone marrow aspirate concentrates obtained from arterial blood, venous blood, and bone marrow aspirate to determine its respective regenerative potential in vitro. Arterial blood-derived PRF (Ar-PRF), venous blood-derived PRF (Ve-PRF), and solid bone marrow aspirate concentrate (sBMAC) were prepared from New Zealand white rabbits. Each clot was evaluated for its cytocompatibility and regenerative potential on primary rabbit gingival fibroblasts and osteoblasts. Both gingival fibroblasts and osteoblasts treated with each concentrate showed excellent viability. Interestingly, the sBMAC-treated cells demonstrated significantly greater migratory potential than the other treatment groups. Furthermore, higher mRNA levels of transforming growth factor-β (TGF-β), vascular endothelial growth factor (VEGF) and collagen I (COL1) in gingival fibroblasts were observed in sBMAC group compared with Ar-PRF and Ve-PRF groups. Greater osteoblast differentiation potential, including higher osteocalcin (OCN) expression and mineralization potential, was found in osteoblasts treated with sBMAC. However, minor differences between the behaviors of cells treated with Ar-PRF and Ve-PRF were observed. In conclusion, sBMAC might be a new candidate for promoting wound healing and bone regeneration. Further preclinical and clinical experiments are necessary to prove the regenerative potential of sBMAC in the body.

Impact of the Process Variables on the Yield of Mesenchymal Stromal Cells from Bone Marrow Aspirate Concentrate

Human bone marrow (BM) has been highlighted as a promising source of mesenchymal stromal cells (MSCs) containing various growth factors and cytokines that can be potentially utilized in regenerative procedures involving cartilage and bone. However, the proportion of MSCs in the nucleated cell population of BM is only around 0.001% to 0.01% thereby making the harvesting and processing technique crucial for obtaining optimal results upon its use in various regenerative processes. Although several studies in the literature have given encouraging results on the utility of BM aspiration concentrate (BMAC) in various regenerative procedures, there is a lack of consensus concerning the harvesting variables such as choice of anesthetic agent to be used, site of harvest, size of the syringe to be used, anticoagulant of choice, and processing variables such as centrifugation time, and speed. In this review article, we aim to discuss the variables in the harvesting and processing technique of BMAC and their impact on the yield of MSCs in the final concentrate obtained from them.

Fibronectin Adherent Cell Populations Derived From Avascular and Vascular Regions of the Meniscus Have Enhanced Clonogenicity and Differentiation Potential Under Physioxia

The meniscus is composed of an avascular inner region and vascular outer region. The vascular region has been shown to contain a progenitor population with multilineage differentiation capacity. Strategies facilitating the isolation and propagation of these progenitors can be used to develop cell-based meniscal therapies. Differential adhesion to fibronectin has been used to isolate progenitor populations from cartilage, while low oxygen or physioxia (2% oxygen) enhances the meniscal phenotype. This study aimed to isolate progenitor populations from the avascular and vascular meniscus using differential fibronectin adherence and examine their clonogenicity and differentiation potential under hyperoxia (20% oxygen) and physioxia (2% oxygen). Human vascular and avascular meniscus cells were seeded onto fibronectin-coated dishes for a short period and monitored for colony formation under either hyperoxia or physioxia. Non-fibronectin adherent meniscus cells were also expanded under both oxygen tension. Individual fibronectin adherent colonies were isolated and further expanded, until approximately ten population doublings (passage 3), whereby they underwent chondrogenic, osteogenic, and adipogenic differentiation. Physioxia enhances clonogenicity of vascular and avascular meniscus cells on plastic or fibronectin-coated plates. Combined differential fibronectin adhesion and physioxia isolated a progenitor population from both meniscus regions with trilineage differentiation potential compared to equivalent hyperoxia progenitors. Physioxia isolated progenitors had a significantly enhanced meniscus matrix content without the presence of collagen X. These results demonstrate that combined physioxia and fibronectin adherence can isolate and propagate a meniscus progenitor population that can potentially be used to treat meniscal tears or defects.

Post-Traumatic Osteoarthritis Assessment in Emerging and Advanced Pre-Clinical Meniscus Repair Strategies: A Review

Surgical repair of meniscus injury is intended to help alleviate pain, prevent further exacerbation of the injury, restore normal knee function, and inhibit the accelerated development of post-traumatic osteoarthritis (PTOA). Meniscus injuries that are treated poorly or left untreated are reported to significantly increase the risk of PTOA in patients. Current surgical approaches for the treatment of meniscus injuries do not eliminate the risk of accelerated PTOA development. Through recent efforts by scientists to develop innovative and more effective meniscus repair strategies, the use of biologics, allografts, and scaffolds have come into the forefront in pre-clinical investigations. However, gauging the extent to which these (and other) approaches inhibit the development of PTOA in the knee joint is often overlooked, yet an important consideration for determining the overall efficacy of potential treatments. In this review, we catalog recent advancements in pre-clinical therapies for meniscus injuries and discuss the assessment methodologies that are used for gauging the success of these treatments based on their effect on PTOA severity. Methodologies include histopathological evaluation of cartilage, radiographic evaluation of the knee, analysis of knee function, and quantification of OA predictive biomarkers. Lastly, we analyze the prevalence of these methodologies using a systemic PubMed® search for original scientific journal articles published in the last 3-years. We indexed 37 meniscus repair/replacement studies conducted in live animal models. Overall, our findings show that approximately 75% of these studies have performed at least one assessment for PTOA following meniscus injury repair. Out of this, 84% studies have reported an improvement in PTOA resulting from treatment.

Changes in the avascular area of the meniscus using mesenchymal stem cells and growth plate chondrocytes in a pig model

Menisci are wedge-shaped cartilage discs that are divided into two parts: the avascular and vascular regions. They are formed by fibrocartilage tissue, which contains round cartilage-like cells and extracellular matrix. Meniscus injury in animals is a common orthopedic problem, but data on the natural healing process mainly deals with the vascular zone. The healing processes in the avascular zone of the meniscus are significantly limited. Thus, this study aimed to evaluate autologous growth plate chondrocytes' impact on the healing process of a damaged meniscus in the avascular zone based on a growing animal model. The study group consisted of 10 pigs at about three months of age. From each animal, chondrocytes from the iliac growth plate and from concentrated bone marrow were taken. Knee joints were divided into right (R) and left (L). The medial meniscus of the R knee joint was treated with a hyaluronic acid based scaffold incubated with bone marrow cells from marrow aspirates (nCHON). The medial meniscus of the L knee joint was treated with a hyaluronic acid based scaffold incubated with bone marrow cells from marrow aspirates supplemented with immature chondrocytes isolated from growth plates (wCHON). The meniscus was damaged in the avascular zone in both knee joints. Followingly, the damaged part of the meniscus was filled with a scaffold with cells from the concentrated bone marrow and from growth plate chondrocytes. In the control group, a scaffold with concentrated bone marrow cells was used. After three months the animals were euthanized and preparations (microscopic slides) were made from the meniscus' damaged part. A qualitative and quantitative analysis have been prepared. The wCHON group in comparison with the nCHON group showed a statistically significantly higher number of fusiform cells on the surface of the graft as well as better healing of the graft. In addition, the degree of vascularization was higher in specimens from the wCHON group than in the nCHON group. The results of our research on immature pig knees revealed that mesenchymal stem cell and growth plate chondrocytes could be treated as the cell source for meniscus reconstruction, and growth plate chondrocytes enhance healing processes in the avascular zone of the injured meniscus.

Nonoperative and Operative Soft-Tissue and Cartilage Regeneration and Orthopaedic Biologics of the Knee: An Orthoregeneration Network (ON) Foundation Review

Orthoregeneration is defined as a solution for orthopedic conditions that harnesses the benefits of biology to improve healing, reduce pain, improve function, and optimally, provide an environment for tissue regeneration. Options include: drugs, surgical intervention, scaffolds, biologics as a product of cells, and physical and electro-magnetic stimuli. The goal of regenerative medicine is to enhance the healing of tissue after musculoskeletal injuries as both isolated treatment and adjunct to surgical management, using novel therapies to improve recovery and outcomes. Various orthopaedic biologics (orthobiologics) have been investigated for the treatment of pathology involving the knee, including symptomatic osteoarthritis and chondral injuries, as well as injuries to tendon, meniscus, and ligament, including the anterior cruciate ligament. Promising and established treatment modalities include hyaluronic acid (HA) in liquid or scaffold form; platelet-rich plasma (PRP); bone marrow aspirate (BMA) comprising mesenchymal stromal cells (MSCs), hematopoietic stem cells, endothelial progenitor cells, and growth factors; connective tissue progenitor cells (CTPs) including adipose-derived mesenchymal stem cells (AD-MSCs) and tendon-derived stem cells (TDSCs); matrix cell-based therapy including autologous chondrocytes or allograft; vitamin D; and fibrin clot. Future investigations should standardize solution preparations, because inconsistent results reported may be due to heterogeneity of HA, PRP, BMAC, or MSC preparations and regimens, which may inhibit meaningful comparison between studies to determine the true efficacy and safety for each treatment.

Blood in the joint: effects of hemarthrosis on meniscus health and repair techniques

Injury to the meniscus is common and frequently leads to the development of post-traumatic osteoarthritis (PTOA). Many times meniscus injuries occur coincident with anterior cruciate ligament (ACL) injuries and lead to a bloody joint effusion. Hemarthrosis, or bleeding into the joint, has been implicated in degeneration of joint tissues. The goal of this review paper is to understand the pathophysiology of blood-induced joint damage, the possible effects of blood on meniscus tissue, and the implications for current meniscus repair techniques that involve the introduction of blood-derived products into the joint. In this review, we illustrate the similarities in the pathophysiology of joint damage due to hemophilic arthropathy (HA) and osteoarthritis (OA). Although numerous studies have revealed the harmful effects of blood on cartilage and synovium, there is currently a gap in knowledge regarding the effects of hemarthrosis on meniscus tissue homeostasis, healing, and the development of PTOA following meniscus injury. Given that many meniscus repair techniques utilize blood-derived and marrow-derived products, it is essential to understand the effects of these factors on meniscus tissue and the whole joint organ to develop improved strategies to promote meniscus tissue repair and prevent PTOA development.

Mechanically superior matrices promote osteointegration and regeneration of anterior cruciate ligament tissue in rabbits

The gold standard treatment for anterior cruciate ligament (ACL) reconstruction is the use of tendon autografts and allografts. Limiting factors for this treatment include donor site morbidity, potential disease transmission, and variable graft quality. To address these limitations, we previously developed an off-the-shelf alternative, a poly(l-lactic) acid (PLLA) bioengineered ACL matrix, and demonstrated its feasibility to regenerate ACL tissue. This study aims to 1) accelerate the rate of regeneration using the bioengineered ACL matrix by supplementation with bone marrow aspirate concentrate (BMAC) and growth factors (BMP-2, FGF-2, and FGF-8) and 2) increase matrix strength retention. Histological evaluation showed robust tissue regeneration in all groups. The presence of cuboidal cells reminiscent of ACL fibroblasts and chondrocytes surrounded by an extracellular matrix rich in anionic macromolecules was up-regulated in the BMAC group. This was not observed in previous studies and is indicative of enhanced regeneration. Additionally, intraarticular treatment with FGF-2 and FGF-8 was found to suppress joint inflammation. To increase matrix strength retention, we incorporated nondegradable fibers, polyethylene terephthalate (PET), into the PLLA bioengineered ACL matrix to fabricate a "tiger graft." The tiger graft demonstrated the greatest peak loads among the experimental groups and the highest to date in a rabbit model. Moreover, the tiger graft showed superior osteointegration, making it an ideal bioengineered ACL matrix. The results of this study illustrate the beneficial effect bioactive factors and PET incorporation have on ACL regeneration and signal a promising step toward the clinical translation of a functional bioengineered ACL matrix.

Oncogenic roles of lncRNA BLACAT1 and its related mechanisms in human cancers

Long non-coding RNAs (lncRNAs) play indispensable roles in mediating regulation of epigenetics, and their dysregulation is strongly associated with the initiation and progression of human cancers. Recently, lncRNA bladder cancer-associated transcript 1 (BLACAT1) has been observed to exert oncogenic effects on cancers, including glioma, breast cancer, lung cancer, hepatocellular carcinoma, gastric cancer, colorectal cancer, ovarian cancer, cervical cancer and osteosarcoma. Additional mechanical analyses have uncovered that lncRNA BLACAT1 is positively correlated with tumor stage, lymph node metastasis and distant metastasis of primary tumors via involvement with various cellular activities, thus leading to poor overall survival and progression-free survival (PFS). In this review, we generalize the oncogenic roles of BLACAT1 in multiple human cancers through correlation with clinical implications and cellular activities. Moreover, we forecast its potential clinical application as a novel biomarker and a promising therapeutic target for cancers.

Platelet-Rich Plasma Augmentation in Meniscal Repair Surgery: A Systematic Review of Comparative Studies

PURPOSE

To systematically review the literature on meniscal repair surgery and assess functional and radiographic outcomes of platelet-rich plasma (PRP)-augmented repair compared with standard repair techniques.

METHODS

A systematic review of the literature was completed according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines using the PubMed, MEDLINE, Embase, and Cochrane databases. The inclusion criteria included all human studies testing PRP augmentation of meniscal repair written in the English language. All cadaveric, animal, and basic science studies were excluded from review. The quality of the included publications was assessed prior to data extraction through the Jadad score. Risk of bias was further determined by Methodological Index for Non-randomized Studies (MINORS) and Cochrane risk-of-bias assessments. Heterogeneity in outcomes reported across studies was evaluated using I² statistic calculations.

RESULTS

A total of 5 studies (1 with Level I evidence; 1, Level II; and 3, Level III) met the inclusion criteria for this review, all comparing PRP augmentation of meniscal repair surgery versus meniscal repair with no augmentation. Overall quality and risk of bias in the included studies varied substantially (Jadad score, 1-5; Methodological Index for Non-randomized Studies score, 7-18). Three comparative studies found no significant difference in outcome or failure, whereas the other two showed a significant improvement in PRP-augmented repairs at final follow-up. Two studies assessed healing with postoperative magnetic resonance imaging or second-look arthroscopy, with both showing significantly improved outcomes in the PRP-treated groups (P < .01 and P = .048). PRP preparation techniques and composition differed among all studies and were inconsistently reported.

CONCLUSIONS

In early and limited investigations, there is insufficient evidence to support PRP augmentation of meniscal repair surgery improving functional and radiographic outcomes and resulting in lower failure rates compared with standard repair techniques. There is considerable heterogeneity in the reporting and preparation of PRP used for augmentation.

LEVEL OF EVIDENCE

Level III, systematic review of Level I to III studies.

Early Functional Rehabilitation after Meniscus Surgery: Are Currently Used Orthopedic Rehabilitation Standards Up to Date?

Meniscus therapy is a challenging process. Besides the respective surgical procedure such as partial meniscectomy, meniscus repair, or meniscus replacement, early postoperative rehabilitation is important for meniscus regeneration and return to sport and work as well as long-term outcome. Various recommendations are available. However, the current literature lacks information concerning the actual early rehabilitation in daily routine recommended by orthopedic surgeons. Thus, the purpose of this study was to investigate currently used standard early rehabilitation protocols in the daily routine of orthopedic surgeons. This study investigated the recommendations and concepts for early rehabilitation after meniscus therapy given by German, Austrian, and Swiss orthopedic institutions. Standardized criteria such as weight bearing, range of motion, use of an orthosis, and rehabilitation training were analyzed according to the conducted surgical procedure: partial meniscectomy, meniscus repair, or meniscus replacement. The analysis of standard rehabilitation concepts for partial meniscectomy (n = 15), meniscus repair (n = 54), and meniscus replacement (n = 7) showed significantly earlier functional rehabilitation in all criteria after partial meniscectomy in contrast to meniscus repair techniques (p < 0.001). In addition, significant restrictions were found in full weight bearing, full range of motion, and the use of braces. In summary, a wide range of recommendations for weight bearing, ROM, brace therapy, and mobilization is available, particularly after meniscus repair and meniscus replacement. Most concepts are in accordance with those described in the current literature. Further research is necessary to enhance the scientific evidence on currently used early rehabilitation concepts after meniscus therapy.

Development of a Meniscal Ossicle After a Meniscal Root Repair Augmented with Bone Marrow Aspirate Concentrate: A Case Report

CASE

A 17-year-old boy had persistent knee pain 1 year after medial meniscal root repair augmented with bone marrow aspirate concentrate injection. Radiographs and magnetic resonance imaging (MRI) demonstrated an intrameniscal ossicle which was not present on MRI performed before 6 months. He underwent arthroscopic excision of the meniscal ossicle. At the 7-month follow-up, he had complete relief of his pain.

CONCLUSIONS

It is possible that the meniscal ossicle developed because of osteoinductive cells and cytokines from the injected bone marrow or the drill hole for root repair and should be considered as a possible complication of this procedure.