Is the cortical capillary renamed as the transcortical vessel in diaphyseal vascularity?

A recent article published in Nature Metabolism, "A network of trans-cortical capillaries as a mainstay for blood circulation in long bones," explained the long bone vascularity. In the mouse model, the authors demonstrated hundreds of transcortical vessels (TCVs) commencing from the bone marrow and traversing the whole cortical thickness. They realized that TCVs were the same as bleeding vessels of periosteal bed observed in the human tibia and femoral epiphysis during surgery. TCVs expressed arterial or venous markers and were proposed to be the backbone of bone vascularity as 80% of arterial and 59% of venous blood distributed through them. This new evidence challenged the existence of the "cortical capillaries" stated in previous literature. We conducted a review of the existing literature to compare this model with those in earlier research. The bone vascularity model was explained by many researchers who did their work in animal models like pig, dog, rabbit, and mouse. The TCVs were identified in these animal model studies as cortical capillaries or vessels of cortical canals. Studies are scarce, showing the presence of TCVs in humans. The role of TCVs in human cortical vascularity remains ambiguous until the substantial evidence is collected in future studies.

Bone-specific kinetic model to quantify periosteal and endosteal blood flow using indocyanine green in fluorescence guided orthopedic surgery.

This letter describes a hybrid plug/compartment (HyPC) kinetic model to fit dynamic indocyanine green fluorescence data acquired in a porcine model of long bone traumatic fracture. Parametric images of periosteal blood flow, endosteal blood flow, total bone blood flow and fraction of endosteal-to-periosteal flow were obtained by applying the HyPC model on a pixel-by-pixel basis. Intraoperative discrimination between healthy and damaged bone could facilitate debridement reducing post-operative complications from non-union and infection. The ability to quantify periosteal and endosteal blood flow could inform nail vs. plate-and-screw decisions to avoid further compromising cortical blood supply.

Microcirculatory consequences of limb ischemia/reperfusion in ovariectomized rats treated with zoledronic acid.

BACKGROUND: Nitrogen-containing bisphosphonates (BIS) are potent therapeutics in osteoporosis, but their use may result in osteonecrotic side-effects in the maxillofacial region. Periosteal microcirculatory reactions may contribute to the development of bone-healing complications, particularly in osteoporotic bones, where ischemia-reperfusion (IR) events often develop during orthopaedic/trauma interventions. The effect of BIS on the inflammatory reactions of appendicular long bones has not yet been evaluated; thus, we aimed to examine the influence of chronic zoledronate (ZOL) administration on the periosteal microcirculatory consequences of hindlimb IR in osteopenic rats. MATERIALS AND METHODS: Twelve-week-old female Sprague-Dawley rats were ovariectomized (OVX) or sham-operated, and ZOL (80 µg/kg iv, weekly) or a vehicle was administered for 8 weeks, 4 weeks after the operation. At the end of the pre-treatment protocols, 60-min limb ischemia was induced, followed by 180-min reperfusion. Leukocyte-endothelial interactions were quantitated in tibial periosteal postcapillary venules by intravital fluorescence videomicroscopy. CD11b expression of circulating polymorphonuclear leukocytes (PMN, flow cytometry) and plasma TNF-alpha levels (ELISA) were also determined. Two-way RM ANOVA followed by the Holm-Sidak and Dunn tests was used to assess differences within and between groups, respectively. RESULTS: Limb IR induced significant increases in PMN rolling and firm adhesion in sham-operated and OVX rats, which were exacerbated temporarily in the first 60 min of reperfusion by a ZOL treatment regimen. Postischemic TNF-alpha values showed a similar level of postischemic elevations in all groups, whereas CD11b expression only increased in rats not treated with ZOL. CONCLUSIONS: The present data do not show substantial postischemic periosteal microcirculatory complications after chronic ZOL treatment either in sham-operated or OVX rats. The unaltered extent of limb IR-induced local periosteal microcirculatory reactions in the presence of reduced CD11b adhesion molecule expression on circulating PMNs, however, may be attributable to local endothelial injury/activation caused by ZOL.

Vascularized Thumb Metacarpal Periosteal Flap for Scaphoid Nonunion in Adolescents: A Prospective Cohort Study of 12 Patients.

PURPOSE: To evaluate clinical and radiological outcomes after surgical treatment of scaphoid nonunion in adolescents with a vascularized thumb metacarpal periosteal pedicled flap (VTMPF). METHODS: Twelve patients younger than 18 years with scaphoid nonunion, who underwent a VTMPF procedure without bone grafting, were included for this prospective cohort study, at a mean follow-up of 10.2 months. Patients were operated on by 3 different hand surgeons at 3 hand surgery institutions. All patients received a VTMPF, but with different scaphoid internal fixation modalities, in 10 cases using 1 or 2 retrograde 2-mm headless compression screws and in 2 cases without internal fixation. RESULTS: In 11 boys and 1 girl, the mean age was 15.6 years. There were 1 type D1 nonunions (Herbert classification), 6 type D2, 2 type D3, and 2 type D4. Six patients had previously undergone an unsuccessful surgical attempt to treat their nonunion. The mean anterior bone defect was 3.5 mm in length. The patients experienced no postoperative complications. Successful consolidation was achieved in all cases, with 79% cross-sectional trabecular bridging at 12 weeks. Pain subsided after surgery and patients experienced improvements in both their Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) and Modified Mayo Wrist Score (MMWS) results. Overall, 34% and 40% gains in strength and wrist motion, relative to the contralateral normal side, were observed. CONCLUSIONS: In this study, the use of VTMPF for scaphoid nonunion in children and adolescents is associated with generally good outcomes. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Estrogen-dependent efficacy of limb ischemic preconditioning in female rats.

Our aim was to examine the effects of ischemic preconditioning (IPC) on the local periosteal and systemic inflammatory consequences of hindlimb ischemia-reperfusion (IR) in Sprague-Dawley rats with chronic estrogen deficiency (13 weeks after ovariectomy, OVX) in the presence and absence of chronic 17beta-estradiol supplementation (E2, 20 µg kg-1 , 5 days/week for 5 weeks); sham-operated (non-OVX) animals served as controls. As assessed by intravital fluorescence microscopy, rolling and the firm adhesion of polymorphonuclear neutrophil leukocytes (PMNs) gave similar results in the Sham + IR and OVX + IR groups in the tibial periosteal microcirculation during the 3-h reperfusion period after a 60-min tourniquet ischemia. Postischemic increases in periosteal PMN adhesion and PMN-derived adhesion molecule CD11b expressions, however, were significantly reduced by IPC (two cycles of 10'/10') in Sham animals, but not in OVX animals; neither plasma free radical levels (as measured by chemiluminescence), nor TNF-alpha release was affected by IPC. E2 supplementation in OVX animals restored the IPC-related microcirculatory integrity and PMN-derived CD11b levels, and TNF-alpha and free radical levels were reduced by IPC only with E2. An enhanced estrogen receptor beta expression could also be demonstrated after E2 in the periosteum. Overall, the beneficial periosteal microcirculatory effects of limb IPC are lost in chronic estrogen deficiency, but they can be restored by E2 supplementation. This suggests that the presence of endogenous estrogen is a necessary facilitating factor of the anti-inflammatory protection provided by limb IPC in females. The IPC-independent effects of E2 on inflammatory reactions should also be taken into account in this model. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:97-105, 2018.

Histological Changes in the Periosteum Following Subperiosteal Expansion in Rabbit Scalp.

PURPOSE: In intraoral bone grafting, tension-free coverage of the recipient site with periosteal flap results in optimal wound closure. Tissue expansion could be a suitable modality to obtain soft tissue in the oral cavity. The aim of this study was to assess the histology of the periosteum after subperiosteal expansion in the rabbit scalp. MATERIALS AND METHODS: In this animal study, 6 rectangular tissue expanders were placed in the skulls of 6 male white New Zealand rabbits; in 6 control rabbits, an incision was made to the periosteum but no expansion was performed. Three months after the surgeries, the rabbits were sacrificed and tissue samples were stained with hematoxylin and eosin and Masson trichrome. RESULTS: The number of osteoblasts, fibroblasts, and blood vessels and the density of collagen fibers were significantly increased in the experimental group compared with the control group (P < .001). CONCLUSIONS: Subperiosteal tissue expansion in the rabbit scalp markedly increased the histologic components of the periosteum involved in bone regeneration.

Examination of Local Periosteal Microcirculation After Application of Absorbable and Nonabsorbable Membranes.

The use of different membranes is common in dentoalveolar surgery. Absorbable and nonabsorbable membranes are used, often beneath the periosteum, to fulfil different functions (as barriers, patches, or spacers). It is still unclear to what extent such membranes affect the biology of the periosteum and what role is played by piezoelectric devices during preparation of the periosteum. We placed two different membranes (absorbable and nonabsorbable) underneath the periosteum of rat calvaria. We prepared the periosteum using different methods (piezoelectric device vs mechanical device). We then examined and analyzed periosteal microcirculation over a period of 28 days. A clear difference was observed between the two methods when used with absorbable membranes: The piezoelectric device offered advantages. Absorbable membranes maintain considerably more local periosteal microcirculation and should be given preference. In addition, we observed an advantage to using a piezoelectric device for periosteal dissection. Therefore, this method should also be used more widely.

Risk factors leading to mucoperiosteal flap necrosis after primary palatoplasty in patents with cleft palate.

BACKGROUND: Few studies have been published reporting risk factors for flap necrosis after primary palatoplasty in patients with cleft palate. This complication is rare, and the event is a disaster for both the patient and the surgeon. This study was performed to explore the associations between different risk factors and the development of flap necrosis after primary palatoplasty in patients with cleft palate. METHODS: This is a case-control study. A 20 years retrospective analysis (1994-2015) of patients with nonsyndromic cleft palate was identified from medical records and screening day registries). Demographical and risk factor data were collected using a patient´s report, including information about age at surgery, gender, cleft palate type, and degree of severity. Odds ratios and 95% confident intervals were derived from logistic regression analysis. RESULTS: All cases with diagnoses of flap necrosis after primary palatoplasty were included in the study (48 patients) and 156 controls were considered. In multivariate analysis, female sex, age (older than 15 years), cleft type (bilateral and incomplete), and severe cleft palate index were associated with significantly increased risk for flap necrosis. CONCLUSIONS: The findings suggest that female sex, older age, cleft type (bilateral and incomplete), and severe cleft palatal index may be associated with the development of flap necrosis after primary palatoplasty in patients with cleft palate.

The periosteal microcirculation in health and disease: An update on clinical significance.

Apart from its nutritive functions, the periosteum critically affects bone regeneration via its stem/osteoprogenitor cell content. Normal healing after bone fractures, trauma-orthopedic interventions and invasive dental procedures is critically linked to the reestablishment of the periosteal microcirculation, but the reconstruction, replacement or repair of lost tissues may also be performed with autologous periosteum. Besides the initiation of cell differentiation during bone repair and remodeling processes, the periosteum together with the endosteum plays significant roles in the pathogenesis of both hormone-related and trauma-induced osteoporotic alterations in the bone metabolism. Nevertheless, the axial bones, and in particular the jawbones, and the appendicular bones display differences not only in their blood supply and fracture healing characteristics, but also in respect of the development of osteoporosis and their reactions to treatment modalities (i.e. bisphosphonates). These reactions may also be linked to the differences in periosteal microcirculatory reactions. The present overview summarizes the relevant data of microcirculatory studies focusing on the periosteal reactions in different anatomical locations together with the optimal background methodologies, study models and the most significant observations.

Vascularized fibular grafts extended with vascularized periosteum in children.

PURPOSE: The purpose of this report is to evaluate the results of extending vascularized fibular grafts (VFG) with vascularized periosteum (VPG) in bone defect reconstruction in children. METHODS: Retrospective study of 10 children, mean age at surgery was 9.8 years (range, 4-16 years). Origin of one defect was oncological (n = 5), septical (n = 2), traumatic (n = 2), or congenital (n = 1). In five cases the flap consisted of a VFG and a vascularized epiphyseal transfer (VFET) in five. Mean bone defect was 8.5 cm .Mean length of the vascularized periosteal extension was 5.5 cm (range 3.5-8) for VFET, 4.8 cm for VFG (range 3-8). Bone union was assessed with monthly radiographs. RESULTS: Radiographs showed a periosteal callus at 4 weeks in all cases. Bone union was achieved at a mean of 8.4 weeks (range 4-12). Donor site complications included two cases of flexor hallucis longus contracture, and one case of surgical wound marginal necrosis following FVG. One transient tibialis anterior weakness and one tibialis anterior contracture occurred following VFET harvest. None required surgical treatment. Mean follow-up was 28.7 months (range 7-72). CONCLUSIONS: The association of a vascularized periosteal extension with fibular flaps seems to accelerate flap to recipient bone union. © 2016 Wiley Periodicals, Inc. Microsurgery 37:410-415, 2017.

Induction of granulation tissue for the secretion of growth factors and the promotion of bone defect repair.

BACKGROUND: The use of the Masquelet technique in the repair of large bone defects has gained increased acceptance in recent years. The core of this technique is the induction of granulation tissue membrane formation and the implantation of an autologous cancellous bone to reconstruct bone defects in the membrane. In this study, we purpose to explore the structure of induced membrane and the content of growth factors as well to compare between the structure and the effects on osteogenesis of induced membranes and the periosteum in animal models. METHODS: Bilateral radial bone defects were generated in 32 healthy adult rabbits. The defects were implanted with bone cement. The induced membranes and periosteum were removed after 2, 4, 6, and 8 weeks. Thereafter, hematoxylin-eosin staining (HE) and an enzyme-linked immunosorbent assay (ELISA) were performed to detect vascular endothelial growth factor (VEGF), angiotensin II (ANG-II), bone morphogenetic protein 2 (BMP2), fibroblast growth factor 2 (FGF2), and prostaglandin E2 (PGE2). Proteins isolated from total cell lysates were cultured with mesenchymal stem cells to test the cell proliferation and alkaline phosphatase activity using epimysium as a control. RESULTS: The induced membrane and periosteum exhibited similar structures and growth factor levels after 4 and 6 weeks. The highest concentration of BMP-2 and VEGF in the induced membranes occurred in week 6, and FGF-2 and ANG-II concentrations peaked in week 4. The thickness and vascular density of induced membranes gradually decreased with time. CONCLUSION: Induced membrane matured between the 4th and the 6th week and secreted growth factors to promote osteogenesis. The matured induced membrane and periosteum had similar structures and abilities to promote the osteogenesis of mesenchymal stem cells. However, the induced membrane was thicker than the periosteum.

Effect of soft-tissue attachment on tibial fracture healing in rats.

PURPOSE: To compare tibial fracture healing in rats with or without soft-tissue attachment. METHODS: The left tibias of 30 Wistar rats were osteotomised and equally randomised into 3 groups. In the avascular segmental fracture group, an 8-mm bone segment were first removed and then immediately put back. In the vascular segmental fracture group, the 8-mm bone segment was not displaced, with periosteal and muscular attachments. In the simple fracture group, a simple fracture in the middle tibia was made. All tibias were then stabilised with an intramedullary nail through the patellar tendon, and the wound was closed with sutures. After 8 weeks, all left tibias and 9 of the intact right tibias were harvested. Bone mineral content and density of the calluses were assessed using dual energy X-ray absorptiometry scanning. The maximum torsional strength, rigidity, and energy to failure of the tibias were measured. RESULTS: All tibias healed (callus formation), without mal-union or pin migration. The 3 groups did not differ significantly in terms of torsional strength, rigidity, energy to failure, bone mineral content, and bone mineral density. The mean torsional strength of the 9 intact tibias was significantly higher than the healed tibias (14.9 vs. 10.6 Nmm, p=0.021). CONCLUSION: Soft-tissue detachment from bone segments did not impair bone healing in rats.

Effects of a new piezoelectric device on periosteal microcirculation after subperiosteal preparation.

INTRODUCTION: Subperiosteal preparation using a periosteal elevator leads to disturbances of local periosteal microcirculation. Soft-tissue damage can usually be considerably reduced using piezoelectric technology. For this reason, we investigated the effects of a novel piezoelectric device on local periosteal microcirculation and compared this approach with the conventional preparation of the periosteum using a periosteal elevator. MATERIAL AND METHODS: A total of 20 Lewis rats were randomly assigned to one of two groups. Subperiosteal preparation was performed using either a piezoelectric device or a periosteal elevator. Intravital microscopy was performed immediately after the procedure as well as three and eight days postoperatively. Statistical analysis of microcirculatory parameters was performed offline using analysis of variance (ANOVA) on ranks (p<0.05). RESULTS: At all time points investigated, intravital microscopy demonstrated significantly higher levels of periosteal perfusion in the group of rats that underwent piezosurgery than in the group of rats that underwent treatment with a periosteal elevator. CONCLUSION: The use of a piezoelectric device for subperiosteal preparation is associated with better periosteal microcirculation than the use of a conventional periosteal elevator. As a result, piezoelectric devices can be expected to have a positive effect on bone metabolism.

Island osteoperiosteal flap vitality when isolated from basal bone by silicone interposition: an experimental study in rabbit tibia.

PURPOSE: This study sought to confirm, through histologic evaluation, the vitality and viability of the island osteoperiosteal flap (i-flap) in a rabbit tibia model. MATERIALS AND METHODS: In four rabbits, an osteotomy was performed on the tibial aspect of the right leg. A bone flap was raised, but the periosteal attachment was kept intact. The free-floating i-flap was separated from the rest of the bone by a silicone sheet. The rabbits were to be sacrificed after 1, 2, 4, and 8 weeks and histologic samples examined. RESULTS: All surgeries were accomplished successfully; however, three animals showed fractured tibiae within a few days after surgery and were sacrificed immediately after the fractures were discovered. The fourth rabbit was sacrificed at 4 weeks. Histologic specimens showed vital new bone in the i-flap area and signs of remodeling in the transition zone and the original basal bone. CONCLUSION: The i-flap remained vital. This suggests potential for use in bone augmentation strategies, particularly for the alveolar split procedure.

Free fibular flap with periosteal excess for mandibular reconstruction.

BACKGROUND: In microvascular transfer of fibular osteocutaneous flap for mandible reconstruction after cancer ablation, good bone union is necessary to allow timely radiation therapy after surgery. As the area of bone contact between fibula and the original mandible at the edge of the mandibular defect is small, a periosteal excess at both ends of the fibula covering the bone junction can be used to increase the chance of bone union. The purpose of this study is to investigate whether a periosteal excess surrounding both ends of the fibula flap can provide better blood supply and, therefore, ensure bone union and wound healing at 6 weeks after surgery and before radiation therapy initiation. PATIENTS AND METHODS: The transfer of fibular osteocutaneous flap with periosteal excess was only applied to reconstruct segmental mandibular defects. As a consequence, only cases in which osteotomy of fibula was not performed were included in this study. A total of 34 fibular flaps without osteotomies were performed between 2000 and 2008; 17 with and 17 without the periosteal excess. The bone union was evaluated in terms of osseous callus formation using X-rays and CT three-dimensional images at 6 weeks after surgery, and results were assessed by three independent radiologists. RESULTS: There was a significant difference between reconstructions with and without the periosteal excess in terms of bone union (P = 0.022). With reference to postoperative complications, the group reconstructed without periosteal excess presented a higher number of complications, mainly consisting of partial and total flap necrosis, respectively six (35.29%) and two (11.76%) cases. In the group reconstructed with periosteal excess, no loss of the skin island has occurred. A significant difference was observed in terms of partial flap necrosis (P = 0.024), while the other complications did not reveal a statistically significant difference (P > 0.05). CONCLUSIONS: The use of a periosteal excess at both ends of the fibula flap provides better blood supply and is, therefore, able to ensure good bone healing and skin paddle survival regardless of the radiotherapy.

[Experimental studies of microcirculatory changes in the bone]. / A csont mikrokeringési változásainak kísérletes vizsgálati lehetoségei.

INTRODUCTION/AIMS: Our aim was to characterize the periosteal microvascular reaction induced by the destruction of endosteal vasculature by reaming, and to monitor the time sequence of the events. We have also compared the microcirculatory effects of different implant materials that are most frequently employed in human endoprosthetics. MATERIALS AND METHODS: The right tibia of male Wistar rats was reamed by microsurgical means and implanted with titanium, steel-alloy or polyethylene nails. Intravital videomicroscopic examinations of the anteromedial and anterolateral surfaces of the tibial periosteum were performed to evaluate the changes in the overall vascular and capillary densities. Microscopic mechanical tests were used to assess the stability of the implants. In control groups, reaming without nailing was performed and the microvascular changes were examined 6 and 12 weeks after surgery. RESULTS: Reaming alone caused a significant increase in the vascular density of the anteromedial periosteum and a bilateral increase in capillary density. Vascular density at the anteromedial side was increased after all of the implant materials applied, while only polyethylene induced remarkable increases in the capillary and vascular densities at the anterolateral side. Furthermore, polyethylene did not bring about osseointegration. CONCLUSIONS: Enhanced periosteal angiogenesis could be demonstrated after 12 weeks following tibial reaming. The compensatory microvascular reactions evoked by destruction of endosteal microcirculation of long bones are not influenced by osseo-integrative implant materials, but materials of poor osseointegration properties induce considerable compensatory increases in the microvascular density of the periosteum.

Differences in the structure and osteogenesis capacity of the periosteum from different parts of minipig mandibles.

PURPOSE: To compare the structural and cellular differences of the periosteum from different parts of the mandible in minipigs by use of histologic and immunohistochemical methods to confirm the areas in which periosteal osteogenesis in situ can be used to treat mandible defects. MATERIALS AND METHODS: Three minipigs were killed, and the left mandible of each was retrieved with the periosteum remaining and then fixed, decalcified, and embedded. The specimens were cut from the buccal and lingual sides of the ramus, angle, and body of the mandible and the mentum. Sections were stained with hematoxylin-eosin and antibodies for Stro-1 (stem cell marker) and vWF (endothelial cell marker). For each periosteal area, the thickness and number of positive cells for each antibody were measured and analyzed. RESULTS: The mentum and mandibular angle periostea were thicker than those of the body and ramus. In addition, there were more blood vessels in the periostea of the mentum and mandibular body than the angle and ramus. There were more Stro-1-positive cells in the ramus periosteum than the mentum, body, and angle of the mandibles. CONCLUSIONS: The structure and cell populations of the periosteum appear to be site specific. Therefore we suggest periosteal osteogenesis in situ to treat mentum and mandibular body defects. The periosteum should be preserved as much as possible to guarantee a good healing process.

Vascularized periosteal transfer from the medial femoral condyle: is it compulsory to include the cortical bone?

BACKGROUND: The corticoperiosteal flap from the medial femoral condyle has become the workhorse in the management of recalcitrant nonunions with vascularized periosteum. Inclusion of the outer condylar cortex has been advocated to avoid damaging the osteogenic capacity of the periosteum and is at present an ordinary technical step in the procedure. PATIENTS: A clinical prospective study was undertaken to evaluate the effectiveness of periosteal-only microvascular transfers from the medial femoral condyle associated with bone grafts in the treatment of recalcitrant nonunions. A group of 8 patients with periosteal-only flaps (study group) is compared with a corticoperiosteal control group (13 patients). A statistical analysis is made of the results. RESULTS: We had 100% union rate in both the study and control groups. Evaluation of early signs of bone healing by two independent evaluators did not found differences between the groups (4.5 months in the study and 4.9 months in the control group). CONCLUSIONS: Although not statistically significant because of the small sample size, our study might support the idea that both periosteal and corticoperiosteal flaps from the medial femoral condyle are effective, when associated with a bone graft, in the treatment of recalcitrant nonunions with small gaps. A further analysis of the results suggests, albeit no statistical significant, that structural and nonstructural bone grafts are both effective when associated with a vascularized periosteal or corticoperiosteal transfer from the medial femoral condyle.

Transplantation of Cbfa1-overexpressing adipose stem cells together with vascularized periosteal flaps repair segmental bone defects.

BACKGROUND: Segmental bone defect is still a challenge to orthopedic surgeons. Currently available therapies for segmental bone defects have some drawbacks. Tissue engineering using pluripotent stem cells is a new, promising method for bone repair. The present study aims to promote the effect of bone defect repair using the tissue engineered bone in combination with vascularized periosteal flaps. METHODS: The adenoviral vector carrying Cbfa1 transduced rabbit adipose-derived mesenchymal stem cells and gene modified tissue engineering bone (GMB) were constructed. Rabbits with radial defects were implanted with the GMB together with vascularized periosteum (group A); or GMB with free periosteum (group B); or GMB (group C), and scaffold (group D). The bone repair effect was evaluated at 4, 8, or 12 wk, respectively, after the operations. RESULTS: Cbfa1 proteins were strongly expressed in adipose stem cells (ADSCs) that formed a stratified network on the inner surface of the polylactic acid/ polycaprolacton (PLA/PCL) pores. Bone repair was well achieved in the rabbits treated with the Cbfa1-expressing ADSCs and vascularized flap that was markedly better than those treated with either Cbfa1-expressing ADSCs alone or with vascularized flap alone. CONCLUSIONS: Combination with implanting the Cbfa1 gene-modified tissue-engineered bone and vascularized periosteum can better repair the segmental bone defects by stimulating osteogenesis, osteoinduction, and osteoconduction than using either one of the approaches.

Local delivery of FTY720 accelerates cranial allograft incorporation and bone formation.

Endogenous stem cell recruitment to the site of skeletal injury is key to enhanced osseous remodeling and neovascularization. To this end, this study utilized a novel bone allograft coating of poly(lactic-co-glycolic acid) (PLAGA) to sustain the release of FTY720, a selective agonist for sphingosine 1-phosphate (S1P) receptors, from calvarial allografts. Uncoated allografts, vehicle-coated, low dose FTY720 in PLAGA (1:200 w:w) and high dose FTY720 in PLAGA (1:40) were implanted into critical size calvarial bone defects. The ability of local FTY720 delivery to promote angiogenesis, maximize osteoinductivity and improve allograft incorporation by recruitment of bone progenitor cells from surrounding soft tissues and microcirculation was evaluated. FTY720 bioactivity after encapsulation and release was confirmed with sphingosine kinase 2 assays. HPLC-MS quantified about 50% loaded FTY720 release of the total encapsulated drug (4.5 µg) after 5 days. Following 2 weeks of defect healing, FTY720 delivery led to statistically significant increases in bone volumes compared to controls, with total bone volume increases for uncoated, coated, low FTY720 and high FTY720 of 5.98, 3.38, 7.2 and 8.9 mm(3), respectively. The rate and extent of enhanced bone growth persisted through week 4 but, by week 8, increases in bone formation in FTY720 groups were no longer statistically significant. However, micro-computed tomography (microCT) of contrast enhanced vascular ingrowth (MICROFIL®) and histological analysis showed enhanced integration as well as directed bone growth in both high and low dose FTY720 groups compared to controls.