Tissue specific characteristics of cells isolated from human and rat tendons and ligaments

Cytoprotective Effect of Growth Factors Derived From Platelets on Corticosteroid-Treated Primary Anterior Cruciate Ligament-Derived Stromal Cells and Chondrocytes

Background The use of corticosteroids, such as methylprednisolone, for pain management is a common clinical practice. However, it is well known that corticosteroids induce toxicity in anterior cruciate ligament (ACL)-derived stromal cells and chondrocytes. Growth factors from platelets have anti-inflammatory effects that can potentially limit the cytotoxic effects of corticosteroids. In this study, we explored the role of growth factors obtained from the OssinextTM kit (commercially available Wockhardt growth factor concentrate (GFC) kit) in recovering methylprednisolone-induced cell damage. Methodology Primary ACL-derived stromal cells and chondrocytes were isolated from human ligament tissue and articular cartilage, respectively, and characterized by immunophenotyping, gene expression analysis, and immunostaining. GFC obtained from OssinextTM kit was used for the experiments. The ACL-derived stromal cells and chondrocytes were treated with methylprednisolone, alone or in combination with GFC. Cell viability was measured by the neutral red uptake assay. Changes in cell morphology and collagen pattern were observed microscopically by H&E staining and immunostaining, respectively. Cell proliferation was assessed by cell migration assay, and the cell ultra-structure was analyzed using transmission electron microscopy. Results Methylprednisolone was found to induce cytotoxicity, altered cell morphology, reduced cell proliferation, and organelle damage in both ACL-derived stromal cells and chondrocytes. GFC obtained from the OssinextTM kit was able to restore cell viability and reverse the cell structure damages induced by methylprednisolone. GFC was found to recover and protect the cells, both when used in combination with steroids and when used after the steroid treatment. Conclusions The results indicate that GFC may be clinically beneficial when used in combination with steroids to mitigate their adverse effects.

Coding Cell Identity of Human Skeletal Muscle Progenitor Cells Using Cell Surface Markers: Current Status and Remaining Challenges for Characterization and Isolation

Skeletal muscle progenitor cells (SMPCs), also called myogenic progenitors, have been studied extensively in recent years because of their promising therapeutic potential to preserve and recover skeletal muscle mass and function in patients with cachexia, sarcopenia, and neuromuscular diseases. SMPCs can be utilized to investigate the mechanisms of natural and pathological myogenesis via in vitro modeling and in vivo experimentation. While various types of SMPCs are currently available from several sources, human pluripotent stem cells (PSCs) offer an efficient and cost-effective method to derive SMPCs. As human PSC-derived cells often display varying heterogeneity in cell types, cell enrichment using cell surface markers remains a critical step in current procedures to establish a pure population of SMPCs. Here we summarize the cell surface markers currently being used to detect human SMPCs, describing their potential application for characterizing, identifying and isolating human PSC-derived SMPCs. To date, several positive and negative markers have been used to enrich human SMPCs from differentiated PSCs by cell sorting. A careful analysis of current findings can broaden our understanding and reveal potential uses for these surface markers with SMPCs.

Equine suspensory ligament and tendon explants cultured with platelet-rich gel supernatants release different anti-inflammatory and anabolic mediators

The aim of this study was to evaluate the release of pro- and anti-inflammatory as well as anabolic mediators stimulated by a leukocyte-reduced platelet-rich gel supernatant (Lr-PRGS) and a leukocyte-reduced plasma supernatant (Lr-PL) at two concentrations (25 and 50%) on normal equine suspensory ligament explants (SLEs) and tendon explants (TEs). SLEs and TEs from six horses were independently incubated for 48 h with Lr-PRGS and Lr-PL at concentrations of 25 and 50%, respectively. Samples were collected from the incubated tissues at 1 h and 48 h, which were employed for ELISA determination of interleukin 1 beta (IL-1β), tumor necrosis factor alpha (TNF-α),  IL-4, IL-1 receptor antagonist (IL-1ra), platelet-derived growth factor isoform BB (PDGF-BB), transforming growth factor beta-1 (TGF-β₁, and hyaluronic acid (HA). Overall, 50% Lr-PRGS induced significantly less IL-1β release than the other hemoderivatives in both tissues. At 48 h, both Lr-PRGS and 25% Lr-PL induced significantly higher TNF-α concentrations in SLEs when compared to TEs, whereas both Lr-PRGS concentrations induced significantly higher IL-4 concentrations in SLEs in comparison to TEs. IL-1ra release was not different between tissues. However, this cytokine was significantly higher in tissue explants cultured with both Lr-PRGS concentrations. HA concentration was lower in tissue explants cultured with all hemoderivatives at two concentrations when compared to the control group. The positive effects observed for ligaments and tendons treated with Lr-PRGS may be mediated by the inhibition of IL-1β release of and increased release of IL-4 and IL-1ra. Furthermore, PDGF-BB could be a polypeptide responsible for mediating the release of anti-inflammatory cytokines in SLEs and TEs incubated with Lr-PRGS.

Duré G, P. Klein C, F. Bampi V, V. Padoin A, D. Silva V, Braga-Silva J. Platelet-Rich Fibrin Promotes an Accelerated Healing of Achilles Tendon When Compared to Platelet-Rich Plasma in Rat

BACKGROUND

Autologous platelet concentrate has been used to improve the function and regeneration of injured tissues. Tendinopathies are common in clinical practice, although long-term treatment is required. On the basis of lead time, we compared the effect of using platelet-rich plasma (PRP) and platelet-rich fibrin (PRF) in repairing rat Achilles tendon.

METHODS

The effectiveness of using PRP and PRF was evaluated after 14 and 28 postoperative days by histological analysis. The quantification of collagen types I and III was performed by Sirius red staining. Qualitatively, the data were verified with hematoxylin-eosin (H&E) staining.

RESULTS

In Sirius red staining, no significant treatment differences were found between groups. Statistical difference was observed only between PRP (37.2% collagen) and the control group (16.2%) 14 days after treatment. Intra-groups compared twice showed a difference for collagen I (27.8% and 47.7%) and III (66.9% and 46.0%) in the PRF group. The control group showed differences only in collagen I (14.2% and 40.9%) and no other finding was observed in the PRP group. In H&E staining, PRF showed a better cellular organization when compared to the other groups at 28 days.

CONCLUSION

Our study suggests that PRF promotes accelerated regeneration of the Achilles tendon in rats, offering promising prospects for future clinical use.

Progress in cell-based therapies for tendon repair

The last decade has seen significant developments in cell therapies, based on permanently differentiated, reprogrammed or engineered stem cells, for tendon injuries and degenerative conditions. In vitro studies assess the influence of biophysical, biochemical and biological signals on tenogenic phenotype maintenance and/or differentiation towards tenogenic lineage. However, the ideal culture environment has yet to be identified due to the lack of standardised experimental setup and readout system. Bone marrow mesenchymal stem cells and tenocytes/dermal fibroblasts appear to be the cell populations of choice for clinical translation in equine and human patients respectively based on circumstantial, rather than on hard evidence. Collaborative, inter- and multi-disciplinary efforts are expected to provide clinically relevant and commercially viable cell-based therapies for tendon repair and regeneration in the years to come.

Pulsed electromagnetic fields after rotator cuff repair: a randomized, controlled study

The current study tested the hypothesis that the use of pulsed electromagnetic fields after rotator cuff repair is effective in the short term as an adjuvant treatment to reduce local inflammation, postoperative joint swelling, and recovery time, as well as to induce pain relief. Sixty-six patients who underwent shoulder arthroscopy for repair of small to medium rotator cuff tears were randomly divided into 2 groups with a block randomization procedure. Thirty-two patients underwent arthroscopic rotator cuff repair and application of pulsed electromagnetic fields postoperatively; 34 patients underwent rotator cuff repair and placebo treatment (placebo group). All patients had the same postoperative rehabilitation protocol. At 3 months from the index procedure, visual analog scale, range of motion, and University of California at Los Angeles and Constant scores were significantly better in the pulsed electromagnetic fields group than in the placebo group (P<.05). Three patients in the pulsed electromagnetic fields group and 7 patients in the placebo group had mild to moderate capsulitis (P=.2). Severe capsulitis occurred in 1 patient in the pulsed electromagnetic fields group and 2 patients in the placebo group (P=.6). At the last follow-up (minimum, 2 years), clinical and functional outcomes were further improved in both groups, with no significant intergroup differences. Application of pulsed electromagnetic fields after rotator cuff repair is safe and reduces postoperative pain, analgesic use, and stiffness in the short term. At 2 years, no difference was seen in outcomes in patients who did or did not undergo treatment with pulsed electromagnetic fields.

The future of carbon-based scaffolds in foot and ankle surgery

Carbon may represent an alternative material suitable for future development as a soft-tissue substitute that potentially optimizes the biological and mechanical properties required for a graft product used in surgery. In addition, other modes of characterization such as 3-dimensional computational modeling may offer an insight into material performance in a biological environment. Further investigation is required to characterize and model the relationships between biological, mechanical, and design properties of this material to maximize its potential as a biomechanical scaffold and vehicle for delivering biologics that promote tissue repair and regeneration.

The time course of in vivo recovery of transverse strain in high-stress tendons following exercise

OBJECTIVE

To evaluate the time course of the recovery of transverse strain in the Achilles and patellar tendon following a bout of resistance exercise.

METHODS

Seventeen healthy adults underwent sonographic examination of the right patellar (n=9) and Achilles (n=8) tendons immediately prior to and following 90 repetitions of weight-bearing quadriceps and gastrocnemius-resistance exercise performed against an effective resistance of 175% and 250% body weight, respectively. Sagittal tendon thickness was determined 20 mm from the enthesis and transverse strain, as defined by the stretch ratio, was repeatedly monitored over a 24 h recovery period.

RESULTS

Resistance exercise resulted in an immediate decrease in Achilles (t7=10.6, p<0.01) and patellar (t8=8.9, p<0.01) tendon thickness, resulting in an average transverse stretch ratio of 0.86±0.04 and 0.82±0.05, which was not significantly different between tendons. The magnitude of the immediate transverse strain response, however, was reduced with advancing age (r=0.63, p<0.01). Recovery in transverse strain was prolonged compared with the duration of loading and exponential in nature. The average primary recovery time was not significantly different between the Achilles (6.5±3.2 h) and patellar (7.1±3.2 h) tendons. Body weight accounted for 62% and 64% of the variation in recovery time, respectively.

CONCLUSIONS

Despite structural and biochemical differences between the Achilles and patellar tendon, the mechanisms underlying transverse creep recovery in vivo appear similar and are highly time dependent. These novel findings have important implications concerning the time required for the mechanical recovery of high-stress tendons following an acute bout of exercise.

Canine intra-articular multipotent stromal cells (MSC) from adipose tissue have the highest in vitro expansion rates, multipotentiality, and MSC immunophenotypes

OBJECTIVE

To identify the optimum intra-articular multipotent stromal cell (MSC) tissue source in the canine stifle.

STUDY DESIGN

Experimental.

SAMPLE POPULATION

Infrapatellar adipose tissue, synovium lining the joint capsule, and synovium surrounding the cranial cruciate ligament (CrCL) from normal stifles of 6 dogs.

METHODS

Nucleated cell density for each tissue was determined, and cell doublings (CD) and doubling times (DT) were quantified for expansion rates. Adipogenic, osteogenic, and chondrogenic differentiation was confirmed with light microscopy. Fibroblastic, adipogenic, and osteogenic colony forming unit frequencies were determined for multipotentiality. Tissue-specific target gene expression was assessed, and percentages of CD29(+) , CD34(+) , CD44(+) , CD45(+) , and CD90(+) cells quantified.

RESULTS

Adipose tissue had the highest MSC density (ASC). The CD decreased with increasing passages for all cell types, and ASC values tended to be higher. Multipotentiality decreased with passage, but remained highest in ASC. Tissue-specific target gene expression was higher in induced versus noninduced cells, and ASCs had the highest upregulation across passages. Most cells were CD29(+) , CD44(+) , CD90(+) , and percentages decreased with passage. Within cell types, there were more CD29(+) ASC in early passages and more CD44(+) and CD90(+) ASC in later passages.

CONCLUSIONS

ASC had the highest in vitro expansion rates, CFU frequencies, tissue-specific target gene expression, and percentages of MSC immunophenotypes.

Responses of equine tendon- and bone marrow-derived cells to monolayer expansion with fibroblast growth factor-2 and sequential culture with pulverized tendon and insulin-like growth factor-I

OBJECTIVE

To compare in vitro expansion of equine tendon- and bone marrow-derived cells with fibroblast growth factor-2 (FGF-2) supplementation and sequential matrix synthesis with pulverized tendon and insulin-like growth factor-I (IGF-I).

SAMPLE

Cells from 6 young adult horses.

PROCEDURES

Progenitor cells were expanded in monolayers with FGF-2, followed by culture with autogenous acellular pulverized tendon and IGF-I for 7 days. Initial cell isolation and subsequent monolayer proliferation were assessed. In pulverized tendon cultures, cell viability and expression of collagen types I and III and cartilage oligomeric matrix protein (COMP) mRNAs were assessed. Collagen and glycosaminoglycan syntheses were quantified over a 24-hour period.

RESULTS

Monolayer expansion with FGF-2 significantly increased the mean ± SE number of tendon-derived cells (15.3 ± 2.6 × 10(6)), compared with bone marrow-derived cells (5.8 ± 1.8 × 10(6)). Overall, increases in collagen type III and COMP mRNAs were seen in tendon-derived cells, compared with results for bone marrow-derived cells. After IGF-I supplementation, increases in collagen type I and type III mRNA expression were seen in bone marrow-derived cells, compared with results for unsupplemented control cells. Insulin-like growth factor-I significantly increased collagen synthesis of bone marrow-derived cells. Monolayer expansion with FGF-2 followed by IGF-I supplementation significantly increased glycosaminoglycan synthesis in tendon-derived cells.

CONCLUSIONS AND CLINICAL RELEVANCE

Tendon-derived cells had increased cell numbers and matrix synthesis after monolayer expansion with FGF-2, compared with results for bone marrow-derived cells. In vivo experiments with FGF-2-expanded tendon-derived cells are warranted to evaluate effects on tendon healing.

Hybrid carbon-based scaffolds for applications in soft tissue reconstruction

Current biomedical scaffolds utilized in surgery to repair soft tissues commonly fail to meet the optimal combination of biomechanical and tissue regenerative properties. Carbon is a scaffold alternative that potentially optimizes the balance between mechanical strength, durability, and function as a cell and biologics delivery vehicle that is necessary to restore tissue function while promoting tissue repair. The goals of this study were to investigate the feasibility of fabricating hybrid fibrous carbon scaffolds modified with biopolymer, polycaprolactone and to analyze their mechanical properties and ability to support cell growth and proliferation. Environmental scanning electron microscopy, micro-computed tomography, and cell adhesion and cell proliferation studies were utilized to test scaffold suitability as a cell delivery vehicle. Mechanical properties were tested to examine load failure and elastic modulus. Results were compared to an acellular dermal matrix scaffold control (GraftJacket(®) [GJ] Matrix), selected for its common use in surgery for the repair of soft tissues. Results indicated that carbon scaffolds exhibited similar mechanical maximums and capacity to support fibroblast adhesion and proliferation in comparison with GJ. Fibroblast adhesion and proliferation was collinear with carbon fiber orientation in regions of sparsely distributed fibers and occurred in clusters in regions of higher fiber density and low porosity. Overall, fibroblast adhesion and proliferation was greatest in lower porosity carbon scaffolds with highly aligned fibers. Stepwise multivariate regression showed that the variability in maximum load of carbon scaffolds and controls were dependent on unique and separate sets of parameters. These finding suggested that there were significant differences in the functional implications of scaffold design and material properties between carbon and dermis derived scaffolds that affect scaffold utility as a tissue replacement construct.

Ligament tissue engineering and its potential role in anterior cruciate ligament reconstruction

Tissue engineering is an emerging discipline that combines the principle of science and engineering. It offers an unlimited source of natural tissue substitutes and by using appropriate cells, biomimetic scaffolds, and advanced bioreactors, it is possible that tissue engineering could be implemented in the repair and regeneration of tissue such as bone, cartilage, tendon, and ligament. Whilst repair and regeneration of ligament tissue has been demonstrated in animal studies, further research is needed to improve the biomechanical properties of the engineered ligament if it is to play an important part in the future of human ligament reconstruction surgery. We evaluate the current literature on ligament tissue engineering and its role in anterior cruciate ligament reconstruction.

Repeated freeze-thaw cycles reduce the survival rate of osteocytes in bone-tendon constructs without affecting the mechanical properties of tendons

Frozen bone-patellar tendon bone allografts are useful in anterior cruciate ligament reconstruction as the freezing procedure kills tissue cells, thereby reducing immunogenicity of the grafts. However, a small portion of cells in human femoral heads treated by standard bone-bank freezing procedures survive, thus limiting the effectiveness of allografts. Here, we characterized the survival rates and mechanisms of cells isolated from rat bones and tendons that were subjected to freeze–thaw treatments, and evaluated the influence of these treatments on the mechanical properties of tendons. After a single freeze–thaw cycle, most cells isolated from frozen bone appeared morphologically as osteocytes and expressed both osteoblast- and osteocyte-related genes. Transmission electron microscopic observation of frozen cells using freeze-substitution revealed that a small number of osteocytes maintained large nuclei with intact double membranes, indicating that these osteocytes in bone matrix were resistant to ice crystal formation. We found that tendon cells were completely killed by a single freeze–thaw cycle, whereas bone cells exhibited a relatively high survival rate, although survival was significantly reduced after three freeze–thaw cycles. In patella tendons, the ultimate stress, Young’s modulus, and strain at failure showed no significant differences between untreated tendons and those subjected to five freeze–thaw cycles. In conclusion, we identified that cells surviving after freeze–thaw treatment of rat bones were predominantly osteocytes. We propose that repeated freeze–thaw cycles could be applied for processing bone-tendon constructs prior to grafting as the treatment did not affect the mechanical property of tendons and drastically reduced surviving osteocytes, thereby potentially decreasing allograft immunogenecity.

Passage and concentration-dependent effects of Indomethacin on tendon derived cells

Background

Non-steroidal anti-inflammatory drugs (NSAID) are commonly used in the treatment of tendinopathies such as tendonitis and tendinosis. Despite this, little is known of their direct actions on tendon-derived cells. As NSAIDs have been shown to delay healing in a number of mesenchymal tissues we have investigated the direct effects of indomethacin on the proliferation of tendon-derived cells.

Results and Discussion

The results obtained were dependent on both the type of cells used and the method of measurement. When measured using the Alamar blue assay, a common method for the measurement of cell proliferation and viability, no effect of indomethacin was seen regardless of cell source. It is likely that this lack of effect was due to a paucity of mitochondrial enzymes in tendon cells.

However, when cell number was assessed using the methylene blue assay, which is a simple nuclear staining technique, an Indomethacin-induced inhibition of proliferation was seen in primary cells but not in secondary subcultures.

Conclusion

These results suggest that firstly, care must be taken when deciding on methodology used to investigate tendon-derived cells as these cells have a quite different metabolism to other mesenchymal derive cells. Secondly, Indomethacin can inhibit the proliferation of primary tendon derived cells and that secondary subculture selects for a population of cells that is unresponsive to this drug.