Platelet autologous growth factors decrease the osteochondral regeneration capability of a collagen-hydroxyapatite scaffold in a sheep model

Background: Current research aims to develop innovative approaches to improve chondral and osteochondral regeneration. The objective of this study was to investigate the regenerative potential of platelet-rich plasma (PRP) to enhance the repair process of a collagen-hydroxyapatite scaffold in osteochondral defects in a sheep model. Methods: PRP was added to a new, multi-layer gradient, nanocomposite scaffold that was obtained by nucleating collagen fibrils with hydroxyapatite nanoparticles. Twenty-four osteochondral lesions were created in sheep femoral condyles. The animals were randomised to three treatment groups: scaffold, scaffold loaded with autologous PRP, and empty defect (control). The animals were sacrificed and evaluated six months after surgery. Results: Gross evaluation and histology of the specimens showed good integration of the chondral surface in both treatment groups. Significantly better bone regeneration and cartilage surface reconstruction were observed in the group treated with the scaffold alone. Incomplete bone regeneration and irregular cartilage surface integration were observed in the group treated with the scaffold where PRP was added. In the control group, no bone and cartilage defect healing occurred; defects were filled with fibrous tissue. Quantitative macroscopic and histological score evaluations confirmed the qualitative trends observed. Conclusions: The hydroxyapatite-collagen scaffold enhanced osteochondral lesion repair, but the combination with platelet growth factors did not have an additive effect; on the contrary, PRP administration had a negative effect on the results obtained by disturbing the regenerative process. In the scaffold + PRP group, highly amorphous cartilaginous repair tissue and poorly spatially organised underlying bone tissue were found

Somatic mutation of immunoglobulin VH6 genes in human infants

Infants respond to antigen by making antibody that is generally of low affinity for antigen. Somatic hypermutation of immunoglobulin genes, and selection of cells expressing mutations with improved affinity for antigen, are the molecular and cellular processes underlying the maturation of antibody affinity. We have reported previously that neonates and infants up to 2 months of age, including individuals undergoing strong immunological challenge, show very few mutated VH6 sequences, with low mutation frequencies in mutated sequences, and little evidence of selection. We have now examined immunoglobulin genes from healthy infants between 2 and 10 months old for mutation and evidence of selection. In this age group, the proportion of VH6 sequences which are mutated and the mutation frequency in mutated sequences increase with age. There is evidence of selection from 6 months old. These results indicate that the process of affinity maturation, which depends on cognate T–B cell interaction and functional germinal centres, is approaching maturity from 6 months old

The use of platelet gel in postero-lateral fusion: preliminary results in a series of 14 cases

Over the last few years, some hemocomponents have been used advantageously in clinical neurosurgical practice, not systemically via transfusion but topically as a sealant (fibrin glue). This has diverted the attention of many authors to the role of platelets in the healing process. The combination of hyper-concentrated platelets and fibrin glue (fibrinogen, XIII factor, fibronectin) with activated thrombin produces a platelet gel that can be easily applied to “difficult” wounds. This topical use of hemocomponents has gained an important role in regenerative medicine. The authors have considered the possibility of using a preparation with a high autologous platelet concentration applied in addition to autologous bone during vertebral postero-lateral fusion. The aim of the procedure is to induce a higher rate of vertebral fusion. Between November 2007 and November 2008, 14 patients (9 men and 5 women, mean age 58.9) underwent laminectomy, vertebral stabilization and postero-lateral fusion. The number of vertebral levels involved in stabilization was: 1 in 2 patients, 2 in 5 patients, 3 in 5 patients, 4 in 1 patient and 5 in 1 patient. Platelet gel was obtained by taking 16 ml of peripheral venous blood from the patient. For this procedure two patented test tubes were used for each patient, with a capacity of 8 m each. These make up the REGEN-THT® (Thrombocyte Harvesting Tube) system that makes it possible to obtain 8 ml of autologous platelet gel in 40–45 min. The addition of Ca gluconate and ethanol at 95% makes it possible to obtain a preparation of plasma rich in platelets and activated thrombin with a platelet concentration five times superior to the haematic one. The platelet gel is combined with fragments of autologous bone and synthetic bone during surgical operation. To allow a comparative assessment of the degree of fusion achieved with and without application of the platelet preparation in each patient, it was arbitrarily decided to use it in only one half of the operative field. All patients underwent serial CT scans 3 and 6 months after surgery as well as plain X-rays to evaluate bone fusion. The reconstructed CT images, especially in sagittal and axial planes, permitted an evaluation of the degree of vertebral fusion and “bone growth”. The fusion rate was calculated measuring the increment of bone density on CT images, by means of an evaluation of the ROI (HU) in the newly formed bone, and comparing bone density within the bone callus formed by autologous and synthetic bone alone in the one to which the platelet preparation had been added. A good rate of fusion was observed in all patients. Furthermore, a comparative analysis of ROI at 3 and 6 months after surgery demonstrated a high increase in the fusion rate during the first 3 months after surgery. After 6 months the differences in ROI between the two sides had balanced out. However, at 6-month follow-up examination, bone density in the half of the surgical field in which platelet gel had been added to autologous–heterologous bone was higher in comparison to the contralateral one. Bony neoformation after posterior-lateral arthrodesis is well-evident 3 months after surgery and usually continues gradually for the following 18–24 months. The autologous platelet preparation used seems to accelerate bony deposition and to promote tissue healing, increasing bone density at the level of posterior–lateral arthrodesis. Moreover, this preparation has low production costs and is easy to apply

Bone Marrow Concentrate Improves Early Cartilage Phase Maturation of a Scaffold Plug in the Knee

BACKGROUND Limited information exists on the clinical use of a synthetic osteochondral scaffold plug for cartilage restoration in the knee. PURPOSE/HYPOTHESIS The purpose of this study was to compare the early magnetic resonance imaging (MRI) appearance, including quantitative T2 values, between cartilage defects treated with a scaffold versus a scaffold with platelet-rich plasma (PRP) or bone marrow aspirate concentrate (BMAC). The hypothesis was that the addition of PRP or BMAC would result in an improved cartilage appearance. STUDY DESIGN Cohort study; Level of evidence, 3. METHODS Forty-six patients with full-thickness cartilage defects of the femur were surgically treated with a control scaffold (n = 11), scaffold with PRP (n = 23), or scaffold with BMAC (n = 12) and were followed prospectively. Patients underwent MRI with a qualitative assessment and quantitative T2 mapping at 12 months after surgery. An image assessment was performed retrospectively by a blinded musculoskeletal radiologist. The cartilage phase was measured by cartilage fill and quantitative T2 values on MRI. A comparison between groups after cartilage repair was performed. RESULTS The control scaffold group consisted of 8 male and 3 female patients (mean age, 38 years; mean body mass index [BMI], 25 kg/m(2)), the PRP group had 15 male and 8 female patients (mean age, 39 years; mean BMI, 26 kg/m(2)), and the BMAC group consisted of 8 male and 4 female patients (mean age, 36 years; mean BMI, 26 kg/m(2)). The PRP-treated (P = .002) and BMAC-treated (P = .03) scaffolds had superior cartilage fill compared with the control group. With quantitative methods, the PRP group demonstrated a mean T2 value (49.1 ms) that was similar to that of the control scaffold group (42.7 ms; P = .07), but the BMAC group demonstrated a mean T2 value (60.5 ms) closer to that of superficial hyaline cartilage (P = .01). The stratification of T2 values between the deep and superficial zones was not observed in any of the groups. CONCLUSION In this comparative study, patients treated with scaffold implantation augmented with BMAC had improved cartilage maturation with greater fill and mean T2 values closer to that of superficial native hyaline cartilage at 12 months. Further work will determine if this translates into improved clinical outcomes