Effective mosquito and arbovirus surveillance using metabarcoding

Effective vector and arbovirus surveillance requires timely and accurate screening techniques that can be easily upscaled. Next-generation sequencing (NGS) is a high-throughput technology that has the potential to modernize vector surveillance. When combined with DNA barcoding, it is termed 'metabarcoding.' The aim of our study was to establish a metabarcoding protocol to characterize pools of mosquitoes and screen them for virus. Pools contained 100 morphologically identified individuals, including one Ross River virus (RRV) infected mosquito, with three species present at different proportions: 1, 5, 94%. Nucleic acid extracted from both crude homogenate and supernatant was used to amplify a 269-bp section of the mitochondrial cytochrome c oxidase subunit I (COI) locus. Additionally, a 67-bp region of the RRV E2 gene was amplified from synthesized cDNA to screen for RRV. Amplicon sequencing was performed using an Illumina MiSeq, and bioinformatic analysis was performed using a DNA barcode database of Victorian mosquitoes. Metabarcoding successfully detected all mosquito species and RRV in every positive sample tested. The limits of species detection were also examined by screening a pool of 1000 individuals, successfully identifying the species and RRV from a single mosquito. The primers used for amplification, number of PCR cycles and total number of individuals present all have effects on the quantification of species in mixed bulk samples. Based on the results, a number of recommendations for future metabarcoding studies are presented. Overall, metabarcoding shows great promise for providing a new alternative approach to screening large insect surveillance trap catches.

Infection-interactions in Ethiopian village chickens

Chickens raised under village production systems are exposed to a wide variety of pathogens, and current or previous infections may affect their susceptibility to further infections with another parasite, and/or can alter the manifestation of each infection. It is possible that co-infections may be as important as environmental risk factors. However, in cross-sectional studies, where the timing of infection is unknown, apparent associations between infections may be observed due to parasites sharing common risk factors. This study measured antibody titres to 3 viral (Newcastle disease, Marek's disease and infectious bursal disease) and 2 bacterial (Pasteurella multocida and Salmonella) diseases, and the infection prevalence of 3 families of endo- and ecto-parasites (Ascaridida, Eimeria and lice) in 1056 village chickens from two geographically distinct populations in Ethiopia. Samples were collected during 4 cross-sectional surveys, each approximately 6 months apart. Constrained ordination, a technique for analysis of ecological community data, was used to explore this complex dataset and enabled potential relationships to be uncovered and tested despite the different measurements used for the different parasites. It was found that only a small proportion of variation in the data could be explained by the risk factors measured. Very few birds (9/1280) were found to be seropositive to Newcastle disease. Positive relationships were identified between Pasteurella and Salmonella titres; and between Marek's disease and parasitic infections, and these two groups of diseases were correlated with females and males, respectively. This may suggest differences in the way that the immune systems of male and female chickens interact with these parasites. In conclusion, we find that a number of infectious pathogens and their interactions are likely to impact village chicken health and production. Control of these infections is likely to be of importance in future development planning.

A review of the effects of insulin-like growth factor and platelet derived growth factor on in vivo cartilage healing and repair

Growth factors may enhance current cartilage repair techniques via multiple mechanisms including recruitment of chondrogenic cells (chemotaxis), stimulation of chondrogenic cell proliferation (mitogenesis) and enhancement of cartilage matrix synthesis. Two growth factors that have been studied in cartilage repair are insulin-like growth factor (IGF) and platelet derived growth factor (PDGF). IGF plays a key role in cartilage homeostasis, balancing proteoglycan synthesis and breakdown. Incorporating IGF into a fibrin clot placed in an equine cartilage defect improved the quality and quantity of repair tissue and reduced synovial inflammation. PDGF is a potent mitogenic and chemotactic factor for all cells of mesenchymal origin, including chondrocytes and mesenchymal stem cells. Resting zone chondrocytes cultured with PDGF demonstrated increased cell proliferation and proteoglycan production, while maturation of these cells along the endochondral pathway was inhibited. Pretreating chondrocytes with PDGF promotes heterotopic cartilage formation in the absence of any mechanical stimulus. PDGF has also been shown to be a potent stimulator of meniscal cell proliferation and migration. These studies and others suggest a potential role for these potent biological regulators of chondrocytes in cartilage repair. More work needs to be performed to define their appropriate dosing and the optimum delivery method. Combining tissue growth factors with a biological matrix can provide a physical scaffold for cell adhesion and growth as well as a means to control the release of these potent molecules. This could result in biological devices that enhance the predictability and quality of current cartilage repair techniques.

Periodontal regeneration with an autogenous bone-Bio-Oss composite graft and a Bio-Gide membrane

This study evaluated the clinical, radiographic, and histologic response to the composite use of Bio-Oss porous bone mineral and autogenous bone in combination with a Bio-Gide bilayer collagen membrane to achieve regeneration when treating human periodontal bone defects. Preoperative recordings for four treatment areas included radiographs, clinical probing depths, and attachment levels; these recordings were repeated at 9 months. Histologic evaluation revealed new cementum with inserting collagen fibers and new bone formation on the surface of both types of graft materials. This grafting combination not only compared favorably with the previous use of Bio-Oss and Bio-Gide, but exceeded that result with almost complete periodontal regeneration. This human histologic study demonstrates that autogenous bone in combination with porous bone mineral matrix, together with the Bio-Gide collagen membrane, has the capacity to stimulate substantial new bone and cementum formation with Sharpey's fiber attachment.

Platelet-derived growth factor enhancement of a mineral-collagen bone substitute

BACKGROUND

Anorganic bovine bone-collagen matrix is commercially available for bone regeneration procedures. Platelet-derived growth factor-BB (PDGF-BB) has been demonstrated to stimulate bone formation in vivo and in vitro. It was the aim of these studies to examine 1) the interaction of this mineral-collagen matrix with PDGF-BB and 2) determine if the adsorption of PDGF-BB to the mineral-collagen matrix stimulates osteoblastic cell proliferation above that of the untreated matrix.

METHODS

Measurement of PDGF-BB adsorption and release was accomplished using 125I radiolabeled growth factor. The PDGF-BB was incubated with the anorganic bovine bone-collagen matrix and the amount which adsorbed was determined. In the release studies, radiolabeled PDGF-BB was adsorbed to the matrix material, then the samples were incubated in buffer for various time periods. The amount of PDGF-BB retained on the matrix was measured and the percent of growth factor released calculated. The biological activity was tested in an in vitro assay with primary culture neonatal rat osteoblastic cells. Osteoblastic cells were cultured on bone mineral-collagen matrix with known amounts of adsorbed PDGF-BB. Proliferation of the cells was assessed by 3H-thymidine incorporation and cell attachment measured by prelabeling cells with 3H-leucine.

RESULTS

PDGF-BB adsorbed to the mineralized-collagen matrix material in a rapid, concentration-dependent fashion. The growth factor was slowly released from the matrix such that approximately 30% of the adsorbed protein was liberated over 10 days. PDGF-BB treated mineralized-collagen matrix displayed significantly (P < 0.05, ANOVA) enhanced proliferation of cultured osteoblastic cells compared to the mineralized-collagen matrix alone.

CONCLUSIONS

These results suggest that PDGF-BB is rapidly adsorbed then slowly released from the anorganic bovine bone-collagen matrix. PDGF-BB adsorbed to this material is able to stimulate proliferation of the attached osteoblastic cells. These data suggest that it may be clinically feasible to adsorb PDGF to this bone-collagen matrix and that this combination of bone growth factor and mineral-collagen matrix has the potential for clinical applications.

Modification of an osteoconductive anorganic bovine bone mineral matrix with growth factors

BACKGROUND

Osteoconductive anorganic bovine bone mineral matrix material has been used clinically in bone regeneration procedures. Platelet-derived growth factor-BB (PDGF-BB) and insulin-like growth factor (IGF-I) are important anabolic growth factors for bone. It was the aim of these studies to 1) examine the interaction of this bone graft material with PDGF-BB and IGF-I and 2) determine if the combination of growth factors with the matrix could stimulate osteoblastic cell proliferation.

METHODS

Adsorption of PDGF-BB and IGF-I was done using 125I radio-labeled growth factors. The PDGF-BB or IGF-I was incubated with the anorganic bovine bone matrix, and the amount of adsorbed growth factor was measured. In the desorption studies, radiolabeled growth factors were adsorbed to the matrix material. The samples were incubated in buffer for various time periods, and the amount remaining on the matrix was measured to calculate the percentage of released growth factor. The biological activity was tested in an in vitro assay with primary culture neonatal rat osteoblastic cells. Porous bone matrix with known amounts of adsorbed PDGF-BB or IGF-I was produced. The osteoblastic cells were cultured on the bone mineral matrix, with and without adsorbed growth factor, and proliferation was assessed by 3H-thymidine incorporation.

RESULTS

Both PDGF-BB and IGF-I adsorbed to bone mineral matrix in a concentration-dependent fashion. The affinity of IGF-I for the material was 10-fold greater than PDGF-BB. In the experiments that measured the release of the initially adsorbed growth factors, approximately 50% of the PDGF-BB and 10% of the IGF-I were released after 10 days. PDGF-BB adsorbed to the matrix material significantly (P <0.05, ANOVA) enhanced the proliferation of cultured osteoblastic cells compared to the mineralized matrix alone. However, IGF-I adsorbed to the matrix material did not significantly enhance cell proliferation.

CONCLUSIONS

These results suggest that PDGF-BB can be adsorbed to the anorganic bovine bone mineral matrix and that this growth factor subsequently enhances the osteogenic properties of this bone graft material. IGF-I also adsorbed to the graft material; however, it was not readily released and it did not produce significant effects in the biologic assay. It appears that it may be clinically feasible to adsorb PDGF to anorganic bovine bone and that this combination of bone growth factor and mineral matrix has the potential for clinical applications.

Eighteen-month radiographic and histologic evaluation of sinus grafting with anorganic bovine bone in the chimpanzee

Maxillary sinus grafting procedures are currently the treatment of choice when the alveolar crest of the posterior maxilla is in close approximation to the maxillary sinus. The short-term histologic and radiographic healing following sinus grafting with natural bone mineral (Bio-Oss) in the chimpanzee has been evaluated. We have previously shown by histomorphometric and radiographic analysis that the percentage of vital bone area, the vertical height, and the density of new bone in the maxillary sinus was significantly greater with anorganic bovine bone compared to bovine Type I collagen matrix. The purpose of this in vivo study was to determine the bone mineral density (BMD) of the sinus grafts, the vertical height stability, the vital bone area, and the extent of anorganic bovine bone replacement 18 months postoperatively in 4 maxillary sinuses from 4 different animals. Radiographic analysis of computed tomographic scans taken at 1.5 years revealed an average BMD of 658 mg/mL, which was not significantly different from the values found at 6.5 months. The radiographic vertical height was maintained between the 6.5- and 18-month time points. On average, the grafts were found to have a height of 14 mm. Lateral wall biopsy specimens at 7.5 months were compared to those at 18 months. With the anorganic bovine bone treatment, the percentage of vital bone area increased from 62 +/- 3% to 70 +/- 7% and the percentage of natural bone mineral area decreased from 19 +/- 14% to 6 +/- 3%. The bovine Type I collagen matrix vital bone percentage at 7.5 months was 34 +/- 21%. These results demonstrate that sinus grafting with anorganic bovine bone maintains radiographic evidence of density and height stability of 1.5 years. In addition, histologic evidence supports the hypothesis that anorganic bovine bone is replaced by vital bone.

Clinical, radiographic, and histologic evaluation of human periodontal defects treated with Bio-Oss and Bio-Gide

This study evaluated the clinical, radiographic, and histologic response to Bio-Oss porous bone mineral when used alone or in combination with Bio-Gide bilayer collagen membrane in human periodontal defects. Four intrabony periodontal defects were treated: two received Bio-Oss alone and two were treated with a combination of Bio-Oss and Bio-Gide. Radiographs, clinical probing depths and attachment levels were obtained preoperatively and 6 to 9 months postoperative, and teeth and surrounding tissues were biopsied. Both treatments significantly improved clinical probing depths and attachment levels, and the radiographic appearance suggested osseous fill. Histologic evaluation revealed that both treatments produced new cementum with inserting collagen fibers and new bone formation on the surface of the graft particles; this regenerative effect was more pronounced using the Bio-Oss/Bio-Gide combination, which resulted in 7 mm of new cementum and periodontal ligament and extensive new bone incorporating the graft. The membrane was intact at 7 months and partially degraded by 9 months after treatment. This human histologic study demonstrates that the porous bone mineral matrix used has the capacity to stimulate substantial new bone and cementum formation and that this capacity is further increased when the graft is used with a slowly resorbing collagen membrane.

A phase I/II clinical trial to evaluate a combination of recombinant human platelet-derived growth factor-BB and recombinant human insulin-like growth factor-I in patients with periodontal disease

The primary objective of this study was to assess the safety of recombinant human (rh) platelet-derived growth factor-BB (PDGF-BB) and (rh) insulin-like growth factor-I (IGF-I) when applied to periodontal osseous defects in humans; a secondary objective was to begin to accrue data on the therapeutic dose of these growth factors (GFs) required to stimulate periodontal regeneration. Thirty-eight human subjects possessing bilateral osseous periodontal lesions were assigned to one of two treatment groups in a split-mouth design. Following full-thickness flap reflection, test sites received local application of the therapeutic drug delivered in coded syringes by a "masked" investigator. Two dose levels were tested, 50 micrograms/ml each of rhPDGF-BB and rhIGF-I in a gel vehicle (LD-PDGF/IGF-I) and 150 micrograms/ml each of rhPDGF-BB and rhIGF-I plus vehicle (HD-PDGF/IGF-I). Control treatment consisted of either conventional periodontal flap surgery or surgery plus vehicle. Safety analyses included physical examination, hematology, serum chemistry, urinalysis, antibody titers, and radiographic evaluation of bony changes. The primary therapeutic assessment was bone fill measured at re-entry 6 to 9 months after treatment. No local or systemic safety issues were found as a result of GF administration. No patients developed antibodies to the rhGF proteins. In subjects treated with LD-PDGF/IGF-I, there were no enhancements in periodontal regeneration compared to controls. However, in patients treated with HD-PDGF/IGF-I, statistically significant increases in alveolar bone formation were noted as measured by surgical re-entry 9 months following drug delivery (P < 0.05). This corresponded to an increase of 2.08 mm of new vertical bone height and 42.3% osseous defect fill in the HD-PDGF/IGF-I subjects versus only 0.75 mm and 18.5% gains in new bone height and osseous fill, respectively, in the controls. Furcation lesions, although limited in number, responded most favorably to treatment, with 2.8 mm horizontal osseous fill. The results from this study suggest that the local application of rhPDGF-BB and rhIGF-I to periodontal lesions is safe at the dose levels studied. LD-PDGF/IGF-I did not elicit increased defect fill compared to the control; however, HD-PDGF/IGF-I resulted in a significant promotion in bone regeneration. Additional studies are warranted to more fully characterize the effects of PDGF/IGF-I on periodontal regeneration in humans.

Comparison of porous bone mineral and biologically active glass in critical-sized defects

Several materials have been proposed as therapies to augment alveolar bone and to promote periodontal regeneration. However, there are an insufficient number of studies that effectively evaluated these therapies. Consequently, the purpose of this study was to compare bone regeneration promoted by porous bone mineral and biologically active glass. Unilateral critical-sized defects (CSDs) were prepared in the radii of 24 rabbits, divided evenly between 2 time periods (4 and 8 weeks) and between 2 treatment groups (porous bone mineral and biologically active glass). Evaluations consisted of clinical examinations, standardized radiography at baseline and every 2 weeks thereafter, as well as histology and histomorphometry. Data were analyzed by an unpaired Student t-test with significance established at P < or = 0.05. We determined that CSDs treated with porous bone mineral were significantly more radiopaque than biologically active glass-treated sites at both 4 and 8 weeks. Moreover, the amount of new bone was significantly greater at both 4 and 8 weeks in the porous bone mineral groups than in the biologically active glass groups. We concluded that in the rabbit radius CSD wound model, porous bone mineral appears to be more effective than biologically active glass in regenerating bone.

Non-coordinate control of bone formation displayed by growth factor combinations with IGF-I

Polypeptide growth factors (GFs) promote osteogenesis by enhancing the mitogenesis, migration, and matrix synthesis of osteoblasts. Most previous investigators have evaluated only the effects of single GFs on these parameters. Studies on single GFs might overlook large biological responses comparable with those documented in the cell cycle literature when GFs are used in combinations that interact synergistically. In this study, we screened for synergistic interactions between IGF-I and three additional GFs (PDGF-BB, TGF-beta 1, and bFGF) on the regulation of bone growth and differentiation. Fetal bovine osteoblasts were assessed for osteoblast mitogenesis, collagenous and non-collagenous protein synthesis, and alkaline phosphatase activity (ALP). Our results show synergistic interactions between IGF-I and the other GFs on osteoblast mitogenic activity and protein synthesis. In contrast to synergistic mitogenic and protein synthesis. In contrast to synergistic mitogenic and protein synthesis effects, IGF-I failed to increase ALP activity when combined with TGF-beta 1, PDGF-BB, and bFGF in bovine osteoblast-like cells.

Gel matrix vehicles for growth factor application in nerve gap injuries repaired with tubes: a comparison of biomatrix, collagen, and methylcellulose

The repair of nerve gap injuries with tubular nerve guides has been used extensively as an in vivo test model in identifying substances which may enhance nerve regeneration. The model has also been used clinical nerve repair. The objective of this study was to compare three different gel matrix-forming materials as potential vehicles for growth factors in this system. The vehicles included a laminin containing extracellular matrix preparation (Biomatrix), collagen, and a 2% methylcellulose gel. The growth factor test substance consisted of a combination of platelet-derived growth factor BB (PDGF-BB) and insulin-like growth factor I (IGF-I). An 8-mm gap in rat sciatic nerve was repaired with a silicone tube containing each of the vehicles alone or with a combination of each vehicle plus PDGF-BB and IGF-I. At 4 weeks after injury, the application of the growth factor combination significantly stimulated axonal regeneration when applied in methylcellulose or collagen, but not in Biomatrix. A similar trend was present between the vehicle control groups. By 8 weeks after injury, nerves repaired with methylcellulose as a vehicle had significantly greater conduction velocity than either collagen or Biomatrix. It was concluded that a 2% methylcellulose gel was the best of the three matrices tested, both in its effects on nerve regeneration and flexibility of formulation.

Guided bone regeneration: integration of a resorbable membrane and a bone graft material

Guided bone regeneration relies primarily on four principles--exclusion of unwanted tissues and cells, space creation and maintenance, protection of the underlying blood clot, and wound stabilization. For successful bone regeneration to occur, large bony defects require an underlying grafting material and a cell-occlusive membrane. The learning objective of this article is to review the history and principles of guided bone regeneration and describe the characteristics of a slowly resorbing bilayer collagen membrane, well suited for bone regeneration procedures. An osteoconductive bone grafting material and its ability to support the overlying collagen membrane and serve as a matrix for the ingrowth of vascular and bone-forming cells are discussed.

Comparative effects of platelet-derived growth factor-BB and insulin-like growth factor-I, individually and in combination, on periodontal regeneration in Macaca fascicularis

Platelet-derived growth factor (PDGF) and insulin-like growth factor I (IGF-I) in combination have previously been shown to enhance periodontal regeneration. The objective of this study was to further characterize the biological effects of this combination of growth factors in non-human primates and compare the effects to those of each growth factor individually. Ligature-induced periodontitis was initiated in 10 cynomolgus monkeys. After periodontal lesions were established, surgery was performed, and either a methylcellulose gel vehicle or vehicle containing 10 micrograms each of either PDGF-BB, IGF-I or both PDGF-BB and IGF-I was applied to exposed root surfaces. Biopsies were taken 4 and 12 wk after treatment and the extent of periodontal regeneration was assessed by histomorphometry. At both 4 and 12 wk vehicle-treated lesions generally revealed minimal osseous defect fill (ODF) (8.5 +/- 2.1% and 14.5 +/- 5.7%, respectively) and new attachment (NA) (34.1 +/- 5.2% and 26.6 +/- 10.5%, respectively). IGF-I treatment did not significantly alter healing compared to vehicle in any parameter at both 4 and 12 wk. PDGF-BB-treated sites exhibited significant (p < 0.05) regeneration of NA (69.6 + 12.0%) at 12 wk; trends for PDGF-BB treatment effect were also observed in other parameters at 4 and 12 wk, although these increases were not statistically significant. Treatment with PDGF-BB/IGF-I resulted in 21.6 +/- 5.1% and 42.5 +/- 8.3% ODF at 4 and 12 wk, respectively, and 64.1 +/- 7.7% and 74.6 +/- 7.4% NA at 4 and 12 wk, respectively (all significantly greater than vehicle, p < 0.05). The results from this study demonstrated that: 1) IGF-I alone at the dose tested did not significantly alter periodontal wound healing; 2) PDGF-BB alone significantly stimulated NA, with trends of effect on other parameters; and 3) the PDGF-BB/IGF-I combination resulted in significant increases in NA and ODF above vehicle at both 4 and 12 wk.

The effect of systemically administered PDGF-BB on the rodent skeleton

Platelet-derived growth factor (PDGF), an osteoblast mitogen, has been demonstrated to accelerate fracture healing and periodontal bone repair when applied locally in vivo. To explore whether PDGF could stimulate bone formation in intact bone, we administered it systemically to rats rendered acutely estrogen-deficient. Because PDGF may stimulate bone resorption in vitro, PDGF was administered with and without an antiresorptive agent (alendronate). All treatments were given by intravenous injection 3 times a week for 6 weeks. Spinal bone mineral density (BMD) decreased by 5% in the vehicle-treated ovariectomized (OVX) rats by the end of the study as determined by DXA. Treatment with PDGF prevented this bone loss and significantly (p < 0.05) increased the bone density in the spine (9%) and whole skeleton (5.8%). Combined treatment with PDGF and alendronate resulted in a greater increase at the spine (18%) and whole skeleton (12.8%) than either agent alone. Histomorphometric analysis demonstrated that treatment with PDGF increased the osteoblast number and osteoblast perimeter without consistent changes in osteoclast estimates. Biomechanical testing demonstrated that PDGF administration increased the vertebral body compressive strength and femoral shaft torsional stiffness and resulted in a trend for enhanced femoral head shearing strength. Coadministration of alendronate further increased these indices of bone strength. PDGF administration also caused premature closure of the growth plate, decreased body fat, and resulted in extraskeletal collagen deposition. We therefore demonstrate, for the first time, that systemic administration of PDGF can increase bone density and strength throughout the skeleton.

Crevicular fluid osteocalcin and pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) as markers of rapid bone turnover in periodontitis. A pilot study in beagle dogs

The objective of this study was to correlate the levels of 2 putative markers of bone metabolism, namely osteocalcin and pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP), to the progression of experimental alveolar bone loss in the beagle dog. 36 control sites and 36 experimental sites in 2 beagle dogs were assessed longitudinally at 2-week intervals for gingival crevicular fluid (GCF) osteocalcin and ICTP levels during a 6-month observation period. Analysis of osteocalcin and ICTP in GCF was performed by RIA. During the study, bone-seeking radiopharmaceutical uptake (BSRU) of 99mTc-MDP was assessed monthly; standardized radiographs were taken at 2-week intervals. The results showed osteocalcin and ICTP levels in GCF increased significantly (p < 0.05) by 2 weeks following initiation of disease. This increase preceded significant increases in BSRU by 2 weeks and radiographic evidence of bone loss by 4 weeks. BSRU was significantly elevated (p < 0.05) at experimental sites as compared to controls at 4 and 8 weeks post-disease initiation. Osteocalcin in GCF peaked 8 and 10 weeks after ligature placement in experimental sites at levels nearly 10-fold greater than contralateral paired control sites. ICTP levels in GCF remained elevated throughout the entire disease progression phase. Following the removal of ligatures, both GCF osteocalcin and ICTP levels dropped precipitously approaching control values. Osteocalcin revealed overall a positive predictive value (PPV) and negative predictive value (NPV) for future bone loss during disease progression of 0.87 and 0.34, respectively, while ICTP showed both high PPV and NPV of 0.87 and 0.91 respectively. Results from this study in the dog model indicate that osteocalcin and especially ICTP relate to indices of active periodontal bony destruction and suggest that these molecules may serve as predictive markers for future alveolar bone loss.

Combination of platelet-derived growth factor-BB and insulin-like growth factor-I is more effective than platelet-derived growth factor-BB alone in stimulating complete healing of full-thickness wounds in "older" diabetic mice

Platelet-derived growth factor and insulin-like growth factor-I have been shown to interact synergistically to enhance repair of skin wounds in normal healing swine. Platelet-derived growth factor alone has shown promise in treating human chronic ulcers. The objective of this study was to compare the wound healing effects of platelet-derived growth factor-BB alone with those of a combination of platelet-derived growth factor-BB and insulin-like growth factor-I in an improved model with the use of "older" animals with diabetes. Older diabetic (db/db) mice (>15 weeks of age) have less elevated insulin levels compared with young db/db mice. The serum insulin levels in the older animals is 1.0 to 2.5 times that of the nondiabetic animals, a similar increase to that which occurs in human patients with type II diabetes. Healing was evaluated in two studies involving a total of 104 animals. Treatment groups included the following: 4.0 microg/cm(2) of platelet-derived growth factor-BB, 40.0 microg/cm(2) of platelet-derived growth factor-BB, 4.0 microg/cm(2) of both platelet-derived growth factor-BB and insulin-like growth factor-I or vehicle. All growth factors were applied topically in a methylcellulose vehicle to full-thickness wounds every other day for 24 days. Efficacy end points were median and mean time to complete healing and rate of wound closure. The median time to complete healing for animals receiving the platelet-derived growth factor-BB/insulin-like growth factor-I combination was 38% and 33% faster (p < 0.001) than animals receiving 4.0 microg/cm(2) and 40.0 microg/cm(2) of platelet-derived growth factor-BB, respectively. The mean time to complete healing for platelet-derived growth factor/insulin-like growth factor-I treated animals was 31% and 29% faster (p < 0.001) than 4.0 microg/cm(2) and 40.0 microg/cm(2) platelet-derived growth factor-BB treated animals, respectively. Wounds treated with 4.0 microg/cm(2) platelet-derived growth factor-BB/insulin-like growth factor-I healed, on average, in 22 days compared with 31 days for 40.0 microg/cm(2) platelet-derived growth factor-BB alone and 38 days for vehicle. Also, platelet-derived growth factor-BB/insulin-like growth factor-I significantly improved the rate of wound closure throughout the duration of the studies compared with either dose of platelet-derived growth factor-BB alone (p < 0.005) or vehicle (p < 0.001). In conclusion, the data show that the combination of platelet-derived growth factor-BB and insulin-like growth factor-I is more effective than platelet-derived growth factor-BB alone at the doses tested or vehicle treatment in stimulating cutaneous wound healing in older, diabetic mice.

Comparison of canine and non-human primate animal models for periodontal regenerative therapy: results following a single administration of PDGF/IGF-I

Two commonly used animal models for evaluating putative periodontal regenerative therapies are the beagle dog model with natural periodontal disease and the non-human primate with ligature-induced attachment loss. The host response, microbiology, and skeletal rates of remodeling of these two models are summarized. In addition, the results of experiments comparing the healing response to periodontal surgery with and without concurrent use of the combination of platelet-derived growth factor (PDGF) and insulin-like growth factor-I (IGF-I) in these models are presented. At 1 month, PDGF/IGF-I administration resulted in a 64.1% and 51.4% increase in new attachment formation in the non-human primate and canine, respectively, while controls (surgery plus placebo) demonstrated 34.1% and 8.6% increases in new attachment formation in the non-human primate and canine models, respectively. Further, application of PDGF/IGF-I stimulated 21.6% and 65% osseous defect fill in the non-human primate and canine, respectively, while controls demonstrated 8.5% and 14.5% osseous defect fill in the non-human primate and canine, respectively. The osseous response in the canine appears greater than that of the non-human primate, and the new attachment formation was more substantial in the non-human primate than the canine. However, in general these data demonstrate a high degree of consistency in the effects of PDGF/IGF-I in promoting periodontal regeneration. Positive results in these two models--the dog with natural periodontal disease and the non-human primate with ligature-induced attachment loss--justify human clinical trial testing of a putative regenerative therapy.

The combination of platelet-derived growth factor-BB and insulin-like growth factor-I stimulates bone repair in adult Yucatan miniature pigs

The combination of insulin-like growth factor-I and platelet-derived growth factor-BB has previously been shown to stimulate healing of soft tissue wounds and the formation of bone and ligament around teeth. The purpose of the present study was to evaluate the effects of platelet-derived growth factor-BB and insulin-like growth factor-I individually and in combination on the healing of osseous wounds. Four standardized cortical wounds were created in each tibia of 11 adult Yucatan miniature pigs. The wounds in one tibia per animal were treated with either purified recombinant human insulin-like growth factor-I, platelet-derived growth factor-BB, or both in a methylcellulose gel. The wounds in each contralateral tibia received placebo gel alone. Coded serial sections of each wound were evaluated by computer-aided histomorphometry 21 days after surgery. The area and perimeter of the newly formed mineralized callus, the thickness of the total callus, and the percentage of mineralized tissue within the callus were significantly increased compared with the values of matched controls only in wounds treated with a combination of insulin-like growth factor-I and platelet-derived growth factor-BB. No significant differences in the measured parameters of callus formation were found in wounds treated with either insulin-like growth factor-I or platelet-derived growth factor-BB alone. Cartilage was present only in sites treated with insulin-like growth factor-I alone. These results suggest that the combination of platelet-derived growth factor-BB and insulin-like growth factor-I stimulates bone formation in wounds in long bones of adult animals and that these growth factors act via different pathways during the repair process.

p53 expression during normal tissue regeneration in response to acute cutaneous injury in swine

The present studies investigated the in vivo expression of the p53 suppressor gene and protein product in response to acute cutaneous injury in swine, along with the parallel expression of the c-sis/PDGF-B mitogen and its receptor beta (PDGF-R beta). p53 expression was shown to be suppressed during the period of active cellular proliferation in the injured tissue and to reemerge during the stages of healing. In contrast, c-sis/PDGF-B and PDGF-R beta were expressed during the early phase of active cellular proliferation and they were suppressed upon healing. This inverse relationship between mitogenic growth factors and p53 suggests the presence of well-controlled physiologic mechanisms that regulate in vivo the processes of normal tissue repair in response to injury. At the stages of tissue regeneration, these mechanisms include both the expression of growth factors that promote cell proliferation and the suppression of p53 that downregulates proliferation. At the stages of healing, the expression of the mitogenic growth factors is suppressed and that of p53 reemerges, reaching its peak at the time of complete epithelialization and healing of the injured tissue. These studies are the first to link the response of p53 protein to physiologic processes of tissue regeneration in vivo.

Role of growth factors in cutaneous wound healing: a review

The well-orchestrated, complex series of events resulting in the repair of cutaneous wounds are, at least in part, regulated by polypeptide growth factors. This review provides a detailed overview of the known functions, interactions, and mechanisms of action of growth factors in the context of the overall repair process in cutaneous wounds. An overview of the cellular and molecular events involved in soft tissue repair is initially presented, followed by a review of widely studied growth factors and a discussion of commonly utilized preclinical animal models. The article concludes with a summary of the preliminary results from human clinical trials evaluating the effects of growth factors in the healing of chronic skin ulcers. Throughout, the interactions among the growth factors in the wound-healing process are emphasized.

Expression of growth factor and receptor mRNAs in skin epithelial cells following acute cutaneous injury

We report that acute injury induces the expression of selective growth factor and growth factor receptors in the epithelial cells of the wounded tissue. In situ hybridization analysis of skin biopsy specimens obtained after cutaneous injury in swine demonstrated the induction of the expression of transforming growth factor-alpha, its receptor, epidermal growth factor-R, acidic fibroblast growth factor, and basic fibroblast growth factor messenger RNAs in the skin epithelial cells of the wounded tissue. There was no significant expression in the epithelial cells of control, uninjured tissues. The expression levels were maximal during the period of active tissue repair (1 to 5 days after injury) and were totally suppressed upon the healing of the wounded tissues. In contrast, insulinlike growth factor-I, (IGF-I), IGF-I receptor, and IGF-II receptor messenger RNAs were expressed in the epithelial cells of both the control, uninjured tissues and in tissue specimens obtained after injury. There was no significant expression of IGF-II messenger RNA in the epithelial cells before or after injury. It seems that injury induces the coordinated expression of selective growth factor and growth factor receptor genes whose products contribute to the regulation of the complex processes involved in tissue repair and remodeling.

Effects of platelet-derived growth factor isoforms on calcium release from neonatal mouse calvariae

Platelet-derived growth factor (PDGF) is the major growth factor in serum for cells of mesenchymal origin and induces many different activities, including bone resorption. Since the initial report that PDGF stimulated calcium release from bone organ cultures, it has been shown that PDGF is a dimeric protein consisting of two disulfide bonded polypeptides encoded by different genes. Three isoforms of the two gene products have been isolated. We compared the capacity of each isoform to stimulate calcium release from radiolabeled mouse calvariae. PDGF-AB from human platelets and recombinant PDGF-BB isoforms significantly stimulated calcium release at 5 ng/ml, but not in lower doses. Recombinant PDGF-AA did not induce calcium release. Indomethacin blocked the stimulated bone resorption, suggesting a prostaglandin-mediated mechanism of action. PDGF-induced calcium release was compared to TGF-beta 1 in the organ culture system. Approximately a 10-fold greater concentration of PDGF-AB and PDGF-BB was required to achieve a similar degree of calcium release as found in TGF-beta 1 treated calvariae. Thus, TGF-beta 1, PDGF-AB, and PDGF-BB significantly stimulated calcium release from mouse calvariae. This response is specific in that PDGF-AA did not stimulate calcium release.

Methods for evaluation of regenerative procedures

A multitude of new procedures and materials are being tested for their ability to promote periodontal wound healing. This review provides an overview of the most well-accepted methods for evaluating periodontal wound healing procedures/materials. Topics discussed include appropriate patient selection, general principles in non-surgical and surgical therapy as they relate to wound healing trials, clinical soft and hard tissue measurements which are generally obtained, an overview of radiographic assessments, and a discussion of the methods and role of histological evaluations in clinical trials. The advantages and disadvantages of the various methodologies are presented. The review concludes with the potential endpoints which can be used in periodontal wound healing studies.

A comparison of ePTFE membranes alone or in combination with platelet-derived growth factors and insulin-like growth factor-I or demineralized freeze-dried bone in promoting bone formation around immediate extraction socket implants

The purpose of this study was to compare bone promotion around implants which were augmented with ePTFE membranes alone or in combination with cortical demineralized freeze-dried bone (DFDB) or the combination of platelet derived growth factor-BB (PDGF) and insulin like growth factor I (PDGF/IGF-I). Membranes were placed over titanium implants which had been inserted into fresh extraction sockets with large buccal dehiscences. Twenty-four implants were placed in 4 dogs. At 18 weeks clinical bone height measurements were taken, the animals were sacrificed, and all specimens retrieved for histologic evaluation. Clinically, a significant gain in bone levels was present in both the ePTFE membrane alone group (P < 0.005) and PTFE plus PDGF/IGF-I group (P < 0.01), but not in the PTFE plus DFDB group. Results from histometric measurements revealed an approximately 2-fold increase in the percentage of implant surface in contact with bone, area of bone adjacent to the implant surface, and in the total length of the implant surface in contact with bone in the dehiscence defects treated with ePTFE plus PDGF/IGF-I compared to the defects receiving ePTFE membranes alone (each P < 0.05). The response to the DFDB was highly variable and it did not significantly improve the efficacy of the PTFE membranes for any parameter measured. The distance from the outer surface of the new bone to the implant surface was statistically significant for ePTFE membranes alone and membranes plus PDGF/IGF-I. The results demonstrated that clinically, ePTFE membranes alone or ePTFE membranes with PDGF/IGF-I were equally effective in promoting bone growth around the implants. Histologic measurements demonstrated that sites treated with ePTFE membranes plus PDGF/IGF-I had the highest bone density compared with sites which received ePTFE membranes alone or with ePTFE membranes and DFDB. The results of this study question the use of DFDB and support the use of ePTFE membranes alone or with PDG-F-BB/IGF-I as potential methods of promoting bone formation around dental implants.

Effects of the platelet-derived growth factor/insulin-like growth factor-I combination on bone regeneration around titanium dental implants. Results of a pilot study in beagle dogs

The purpose of this study was to evaluate the early wound healing events of bone around press-fit titanium implants inserted with and without the concurrent application of a combination of platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF-I). Nine months prior to implant placement all mandibular premolar teeth were extracted in 8 beagle dogs. Subsequently, 40 specially manufactured titanium implants with 2 transverse holes in the apical section were press fit into precise recipient sites in the dogs' mandibles. The dogs were sacrificed at 7 and 21 days following implant placement yielding 12 PDGF-B/IGF-I treated and 8 control (placebo gel or non-treated) implants for each observation period. Coded undecalcified sections were analyzed for: 1) percentage of implant surface in contact with new bone; 2) percentage of peri-implant space filled with new bone; and 3) percentage of implant hole filled with new bone. An analysis of variance was used to determine significant differences among the treatment groups. At 7 days, the percentage of bone fill in the peri-implant spaces and the percentage of implant surface in contact with new bone were both significantly increased in PDGF-B/IGF-I treated sites (P less than 0.01 for both groups). There was less than 1.5% fill of the implant holes in both treated and control sites (no significant differences). At 21 days the percentage of bone fill in the peri-implant spaces was significantly increased in the PDGF-B/IGF-I treated sites (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of short-term application of a combination of platelet-derived and insulin-like growth factors on periodontal wound healing

Polypeptide growth factors are a class of potent natural biologic mediators which regulate many of the activities of wound healing including cell proliferation, migration, and metabolism. Platelet-derived growth factor (PDGF) and insulin-like growth factor-I (IGF-I) have been shown to regulate DNA and protein synthesis in bone cells in vitro and to interact synergistically to enhance soft tissue wound healing in vivo. We have hypothesized that the combination of PDGF and IGF-I may, therefore, enhance regeneration of both the soft and hard tissue components of the periodontium. To test this hypothesis we performed conventional periodontal surgery on all 4 quadrants of the mouth of 13 beagle dogs with naturally occurring periodontal disease. Following flap reflection, degranulation, and root planing, all premolar teeth in 2 quadrants of each dog received a combination of 3 micrograms of recombinant PDGF-B and IGF-I in a methylcellulose gel, while the premolar teeth in the contralateral quadrants received the gel alone. Teeth in 4 additional animals also received 125I-PDGF or 125I-IGF-I in the treated sites. The clearance rate of the 125I-labeled protein, changes in local bone metabolism, and amount of new bone and cementum with inserting collagen fibers were measured. The clearance studies revealed that the half-life of the factors at the site of application was 3.0 hours for IGF-I and to 4.2 hours for PDGF-B. Greater than 96% of the radio-labeled proteins was cleared by 96 hours and no radioactivity was detected 2 weeks after application. There was a significant (P less than 0.01) 2-fold increase in uptake of the bone-seeking radiopharmaceutical Technetium 99-MDP at 2 and 4 weeks in growth factor treated sites compared to controls, indicating that there was increased metabolic activity within the bone at these sites. Computer-aided histologic analyses of biopsies obtained at 2 and 5 weeks post-operatively revealed a significant (P less than 0.01), 5 to 10 fold increase in new bone and cementum in PDGF-B/IGF-I treated sites at both time points compared to controls receiving the placebo gel. The height and total area of new bone continued to increase from 2 to 5 weeks. The new bone underwent a normal maturation process as judged by histologic appearance. A physiologic periodontal ligament space was also formed between the new bone and new cementum. There was no increase in ankylosis in the treated sites.(ABSTRACT TRUNCATED AT 400 WORDS)

Injury induces in vivo expression of platelet-derived growth factor (PDGF) and PDGF receptor mRNAs in skin epithelial cells and PDGF mRNA in connective tissue fibroblasts

Platelet-derived growth factor (PDGF) stimulates many of the processes important in tissue repair, including proliferation of fibroblasts and synthesis of extracellular matrices. In this study we have demonstrated with in situ hybridization and immunocytochemistry the reversible expression of c-sis/PDGF-2 and PDGF receptor (PDGF-R) b mRNAs and their respective protein products in epithelial cells and fibroblasts following cutaneous injury in pigs. Epithelial cells in control, unwounded skin did not express c-sis and PDGF-R mRNAs, and fibroblasts expressed only PDGF-R mRNA. The expression levels in the injured site were correlated with the stage of tissue repair, being highest during the initial stages of the repair process and declining at the time of complete re-epithelialization and tissue remodeling. It is suggested that the controlled, reversible expression of a potent mitogen and its receptor induced by injury may function in an autocrine/paracrine manner on both epithelial cells and fibroblasts to bring about their sustained proliferation during the normal healing process. These studies provide a molecular basis for understanding the mechanisms contributing to normal tissue repair. We suggest the possibility that a defect in these mechanisms may be associated with defective wound healing. It is also conceivable that "chronic" injury may induce irreversible gene expression leading to pathologic, unregulated cell growth.

Topical nonsteroidal agents and corneal wound healing

The effects on corneal wound healing of two topical nonsteroidal anti-inflammatory agents, flurbiprofen sodium (0.03%) and diclofenac sodium (0.1%), and the topical corticosteroid, prednisolone sodium phosphate (1%), were evaluated in masked, controlled rabbit studies. Healing of epithelial scrape wounds was significantly retarded in all three treatment groups for the first 3 days after wounding. There was no difference in the epithelial healing rate between the two nonsteroidal or corticosteroid treatment groups. Clinical grading of epithelial quality, conjunctival hyperemia, keratitis, stromal edema, and corneal haze were similar in all groups. There was a significant early decrease in the iritis score in the diclofenac treatment group. The strength of 2-mm central penetrating corneal trephination wounds and the collagen content of these wounds were similar in all groups. Both the topical nonsteroidal anti-inflammatory agents and the corticosteroid used in the preparations and dosages investigated in this study decreased early epithelialization of scrape wounds but had no apparent effect on corneal stromal healing. No toxic effects of the various drugs were found.

A combination of platelet-derived and insulin-like growth factors enhances periodontal regeneration

The combination of platelet-derived growth factor (PDGF) and insulin-like growth factor one (IGF-1) has previously been shown to enhance repair of soft tissue wounds. Here we report initial observations following application of PDGF and IGF-1 to periodontitis-affected teeth in beagle dogs. 1 micrograms of PDGF and IGF-1 in an aqueous gel was applied to the root surfaces of test teeth following open flap debridement. Control sites received the gel alone. Block biopsies of the teeth and surrounding bone were taken 2 weeks after treatment. Histologic analyses of control specimens revealed a long junctional epithelial attachment, and no new bone or cementum formation. In contrast, growth factor treated sites exhibited significant amounts of new bone and cementum formation. A nearly continuous layer of osteoblasts lined the newly formed bone, and there was a dense cellular "front" at the coronal extent of the new bone. These preliminary results suggest that in vivo application of the combination of PDGF and IGF-1 may enhance regeneration of the periodontal structures.

Growth factors in wound healing. Single and synergistic effects on partial thickness porcine skin wounds

Several growth factors are potential mediators of wound healing, although their actual roles, interactions, and therapeutic use are not established. Six well-characterized human growth factors were chosen for detailed investigation by topical application to standardized skin wounds in swine: epidermal growth factor (EGF), transforming growth factors alpha and beta (TGF-alpha and TGF-beta), fibroblast growth factor (FGF), insulin-like growth factor-I (IGF-I), and platelet-derived growth factor (PDGF). When applied singly in doses up to 1,500 ng, only TGF-beta produced a marked tissue response, as demonstrated by an increase in the new connective tissue volume, the collagen content and maturity, and increased angiogenesis. However, TGF-beta enhanced inflammation and caused abnormal epithelial differentiation and decreased epithelial volume, the last reversed by addition of IGF-I. Recombinant PDGF-2 homodimer, if given in combination with recombinant IGF-I, caused a similar increase in the new connective tissue volume and collagen content and maturity, but without increased inflammation. In addition, this combination stimulated increased amounts of epithelium with normal differentiation. The synergy of PDGF-2 and IGF-I was optimal at a ratio of 2:1 by weight. Of the six individual factors and nine combinations tested, the combinations of PDGF-2 and IGF-I or PDGF-2 and TGF-alpha were the most potent stimulators of healing in the absence of increased inflammation.

Role of platelet-derived growth factor in wound healing: synergistic effects with other growth factors

Platelet-derived growth factor (PDGF) in vitro stimulates DNA synthesis and chemotaxis of fibroblasts and smooth muscle cells and stimulates collagen, glycosaminoglycan, and collagenase production by fibroblasts. These in vitro properties suggest that PDGF, delivered by platelets to the site of injury in vivo, may play an important role in the initiation of the wound repair process. Studies presented here show that the addition of pure PDGF to a wound site involving the epidermis and dermis has little effect on the morphology or biochemistry of the healing wound. In contrast, the addition of partially purified PDGF resulted in significant dose-dependent increases in the width of the newly synthesized connective tissue and epidermal layers. Autoradiography using [3H]thymidine revealed increased numbers of labeled cells in the new connective tissue and epithelial layers. Furthermore, addition of partially purified PDGF resulted in significant increases in the rate of protein and DNA synthesis and the total content of these components in biopsies taken from the wound site. Similar effects were obtained when insulin-like growth factor I was added in combination with pure PDGF. This combination of factors caused a 2.4-fold increase in the width of the newly formed connective tissue layer and a 95% increase in epidermal thickness compared with controls. Insulin-like growth factor I alone caused no significant morphologic changes. Epidermal growth factor alone or in combination with PDGF resulted in a thickening only of the epidermis. These results indicate that the synergistic actions of other factors with PDGF are important in the modulation of the wound healing process.

Detection of gram-negative bacteremia by limulus amebocyte lysate assay: evaluation in a rat model of peritonitis

A spectrophotometric Limulus amebocyte lysate assay using lysis filtration and centrifugation has been developed for the detection of gram-negative bacteria in blood. The assay is directed at detection of endotoxin in viable and nonviable bacteria present in the blood-stream and not detection of free endotoxin in plasma. The assay was evaluated in a model of peritonitis in which rats were challenged with an inoculum consisting of sterilized human feces, barium sulfate, and one of eight species of bacteria. This assay was able to detect gram-negative bacteremia due to Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, Proteus mirabilis, and Klebsiella pneumoniae in the rat model when compared with sham-inoculated uninfected rats. The assay failed to detect bacteremia due to Bacteroides fragilis or Staphylococcus aureus, nor was there a significant rise in absorbance when a pellet containing sterilized feces was implanted in the rat.