Heparin‐Conjugated Poly(Lactic‐Co‐Glycolic Acid) Nanospheres Enhance Large‐Wound Healing by Delivering Growth Factors in Platelet‐Rich Plasma

Platelet‐rich plasma (PRP) contains many growth factors that are involved in tissue regeneration processes. For successful tissue regeneration, protein growth factors require a delivery vehicle for long‐term and sustained release to a defect site in order to maintain their bioactivity. Previously, we showed that heparin‐conjugated poly(lactic‐co‐glycolic acid) nanospheres (HCPNs) can provide long‐term delivery of growth factors with affinity for heparin. In this study, we hypothesize that treatment of a skin wound with a mixture of PRP and HCPNs would provide long‐term delivery of several growth factors contained in PRP to promote the skin wound healing process with preservation of bioactivity. The release of platelet‐derived growth factor‐BB (PDGF‐BB), contained in PRP, from HCPN with fibrin gel (FG) showed a prolonged release period versus a PRP mixture with FG alone (FG‐PRP). Also, growth factors released from PRP with HCPN and FG showed sustained human dermal fibroblast growth for 12 days. Full‐thickness skin wound treatment in mice with FG‐HCPN‐PRP resulted in much faster wound closure as well as dermal and epidermal regeneration at day 9 compared with treatment with FG‐HCPN or FG‐PRP. The enhanced wound healing using FG‐HCPN‐PRP may be due to the prolonged release not only of PDGF‐BB but also of other growth factors in the PRP. The delivered growth factors accelerated angiogenesis at the wound site.     

Wound management: Investigating the interprofessional decision‐making process

Our aim is to develop a robust socio‐geographical transferable theory outlining the basic social process used by members of an interprofessional health care team when making decisions around wound care management. Using a qualitative multigrounded theory approach, three focus groups were held at the Royal Victoria Regional Health Centre in Barrie, Ontario, Canada, comprised of 13 clinicians who participate in wound care decision‐making. Data were analysed using an approach developed for multigrounded theory. A Critical Realist theoretical lens was applied to data analysis in the development of conclusions. Ten categories were identified before thematic saturation. Category interactions developed a perceived basic social process outlining how interprofessional clinicians determine how they approach wound care decisions: patient factors, scope of practice, equipment and supplies, internal clinician factors, knowledge and education, interprofessional team, assessment, wound care specialist consultation, and care plan, as well as documentation and communication. Understanding how wound care decision‐making is determined by interprofessional health care providers will assist clinical leaders and policy makers in creating a foundation for determining resource allocation, allowing clinicians to use evidence‐based practice to improve patient and clinician satisfaction, wound healing time, decrease costs, and prevent wound recurrence.     

Effects of Liposome‐Encapsulated Hemoglobin on Gastric Wound Healing in the Rat

Liposome‐encapsulated hemoglobin (LEH) may improve microcirculation and oxygen (O₂) metabolism at a surgical wound to accelerate its healing. Ten mL/kg of LEH with high (h‐LEH) or low O₂‐affinity (l‐LEH), homologous red blood cells (RBC), empty liposome or saline as a control was infused before a 10‐mm incision and interrupted suture closure of the gastric wall in a total of 110 rats. Two and 4 days later, the stomach was excised for bursting pressure determination and histological sampling. The dose–response relationship was examined in 70 additional rats receiving progressively reduced doses of h‐LEH. Hypoxia‐inducible factor‐1α (HIF‐1α) was stained immunohistochemically in 54 other rats to examine its accumulation at the anastomotic sites. Bursting pressure of the surgical wound was significantly higher 2 days after surgery only in the h‐LEH‐treated rats (P < 0.05), but not at 4 days after surgery, when other rats showed increased bursting pressure to a nonsignificant level. Histological examination revealed less granulocyte infiltration, better granulation, and more macrophage infiltration in h‐LEH‐treated rats at 2 days, but no longer at 4 days postsurgery. Dose–response study revealed that 0.4 mL/kg of h‐LEH (hemoglobin 24 mg/kg) was effective for elevating bursting pressure at 2 days. h‐LEH‐treated rats had significantly suppressed HIF‐1α accumulation in the wound 6, 24, and 48 h after surgery as compared with control animals treated with homologous RBC or saline. In conclusion, the results suggest that h‐LEH, but not l‐LEH or homologous transfusion, may accelerate wound healing early after gastric incision and anastomosis in the rat. The mechanism(s) appears to be related to improved O₂ supply, aerobic metabolism, and suppressed inflammation in the wound.     

Excellent Clinical Outcomes From a National Donation‐After‐Determination‐of‐Cardiac‐Death Lung Transplant Collaborative

Donation‐after‐Determination‐of‐Cardiac‐Death (DDCD) donor lungs can potentially increase the pool of lungs available for Lung Transplantation (LTx). This paper presents the 5‐year results for Maastricht category III DDCD LTx undertaken by the multicenter Australian National DDCD LTx Collaborative. The Collaborative was developed to facilitate interaction with the Australian Organ Donation Authority, standardization of definitions, guidelines, education and audit processes. Between 2006 and 2011 there were 174 actual DDCD category III donors (with an additional 37 potentially suitable donors who did not arrest in the mandated 90 min postwithdrawal window), of whom 71 donated lungs for 70 bilateral LTx and two single LTx. In 2010 this equated to an “extra” 28% of donors utilized for LTx. Withdrawal to pulmonary arterial flush was a mean of 35.2 ± 4.0 min (range 18–89). At 24 h, the incidence of grade 3 primary graft dysfunction was 8.5%[median PaO₂/FiO₂ ratio 315 (range 50–507)]. Overall the incidence of grade 3 chronic rejections was 5%. One‐ and 5‐year actuarial survival was 97% and 90%, versus 90% and 61%, respectively, for 503 contemporaneous brain‐dead donor lung transplants. Category III DDCD LTx therefore provides a significant, practical, additional quality source of transplantable lungs.     

Wound healing in Mac‐1 deficient mice

Mac‐1 (CD11b/CD18) is a macrophage receptor that plays several critical roles in macrophage recruitment and activation. Because macrophages are essential for proper wound healing, the impact of Mac‐1 deficiency on wound healing is of significant interest. Prior studies have shown that Mac‐1^?/? mice exhibit deficits in healing, including delayed wound closure in scalp and ear wounds. This study examined whether Mac‐1 deficiency influences wound healing in small excisional and incisional skin wounds. Three millimeter diameter full thickness excisional wounds and incisional wounds were prepared on the dorsal skin of Mac‐1 deficient (Mac‐1^?/?) and wild type (WT) mice, and wound healing outcomes were examined. Mac‐1 deficient mice exhibited a normal rate of wound closure, generally normal levels of total collagen, and nearly normal synthesis and distribution of collagens I and III. In incisional wounds, wound breaking strength was similar for Mac‐1^?/? and WT mice. Wounds of Mac‐1 deficient mice displayed normal total macrophage content, although macrophage phenotype markers were skewed as compared to WT. Interestingly, amounts of TGF‐β1 and its downstream signaling molecules, SMAD2 and SMAD3, were significantly decreased in the wounds of Mac‐1 deficient mice compared to WT. The results suggest that Mac‐1 deficiency has little impact on the healing of small excisional and incisional wounds. Moreover, the findings demonstrate that the effect of single genetic deficiencies on wound healing may markedly differ among wound models. These conclusions have implications for the interpretation of the many prior studies that utilize a single model system to examine wound healing outcomes in genetically deficient mice.     

Liposome‐Encapsulated Hemoglobin Accelerates Skin Wound Healing in Diabetic dB/dB Mice

Since liposome‐encapsulated hemoglobin with high O₂ affinity (h‐LEH, P₅₀O₂ = 10 mm Hg) has been reported to accelerate skin wound healing in normal mice, it was tested in dB/dB mice with retarded wound healing, as seen in human diabetics. Two full‐thickness dorsal wounds 6 mm in diameter encompassed by silicone stents were created in dB/dB mice. Two days later (day 2), the animals were randomly assigned to receive intravenous h‐LEH (2 mL/kg, n = 7) or saline (2 mL/kg, n = 7). The same treatment was repeated 4 days after wounding (day 4), and the size of the skin lesions was analyzed by photography, surface perfusion was detected by Laser‐Doppler imager, and plasma cytokines and chemokines were determined on days 0, 2, 4, and 7, when all animals were euthanized for morphological studies. The size of the ulcer compared to the skin defect or silicone stent became significantly reduced on days 4 and 7 in mice treated with h‐LEH (47 ± 8% of original size), similar to the level in wild‐type mice, compared to saline‐treated dB/dB mice (68 ± 18%, P < 0.01). Mice treated with h‐LEH had significantly attenuated inflammatory cytokines, increased surface perfusion, and increased Ki67 expression on day 7 in accordance with the ulcer size reduction, while there was no significant difference in chemokines, histological granulation, epithelial thickness, and granulocyte infiltration detected by immunohistochemical staining in the ulcer between the treatment groups. The results suggest that h‐LEH (2 mL/kg) early after wounding may accelerate skin wound healing in dB/dB mice to levels equivalent to wild‐type mice probably via mechanism(s) involving reduced hypoxia, increased surface perfusion, suppressed inflammation, accelerated in situ cell proliferation and protein synthesis.     

Neurosurgical Post‐Operative Wound Infections: A retrospective study on surgical site infections for quality improvement

Despite efforts to maintain a meticulous aseptic environment, wound infection is one of the most common complications following surgery and may be related to dehiscence, haemorrhage, infection, and/or poor surgical technique. With the appearance of new wound closure techniques and suture materials, we felt compelled to perform a retrospective study on our institution's neurosurgical population to determine how our institution compared to others in terms of incidence of surgical site infection (SSI). A retrospective analysis was performed at our single institution for all patients that had cranial or spine surgery by a neurosurgeon for the past 15 years. The data were extracted via Crimson Continuum of Care software program and analysed using χ² and relative risk. The data retrieval software program collected a total of 1184 cranial and spinal surgeries. Of these 1184 cases, 12 resulted in post‐operative wound infections. Using these collected values, we compared the results with published values in the literature. Prior studies have shown that up to 33% of surgical cases have post‐operative infections. Using this reported value in comparison with our data, χ² testing equals 547.893 with 1 df, P = .0001 (confidence interval = 0.05), which demonstrated statistical significance when compared with surgical literature. The results from this retrospective analysis demonstrated that the rate of neurosurgical post‐operative SSI falls within the range consistent with the literature, which has shown rates of infection from <1% up to 15% depending on the type of surgery, surgical technique, and patient characteristics. SSIs can be an unfortunate and costly post‐operative complication. Risks factors in the past have been studied, but introspection by each institution is an important metric to ensure accountability and provide optimal patient care in comparison with established data and guidelines. No deviation from current techniques is deemed necessary at our institution based on the results.     

Evaluation of Hyphecan (1‐4,2‐acetamide‐deoxy‐B‐D‐glucan polymer) on wound healing in a rodent model

Objective: To evaluate the effect of an artificial skin Hyphecan (1‐4,2‐acetamide‐deoxy‐B ‐D ‐glucan polymer) on wound healing in a rodent model. Materials and Method: The prospective study was conducted at a basic science laboratory at a tertiary teaching hospital. Two 4 cm × 4 cm full‐thickness wounds were created on the dorsal surface of 10 Spraque–Dawley rats and covered with Hyphecan and Kaltostat, respectively. Wounds were examined and measured on days 4, 10, 21 and 28, and would continue after day 28 until healed up completely. Punch biopsies (3 mm) were taken on days 4, 10 and 28 for histological examination of the response of healing and repair. Results: Despite the fact that the wound healing rate was similar for both groups on days 4, 10, 21 and 28, the average healing time for the Hyphecan group (29.1 ± 1.7 days) was significantly shorter statistically (P = 0.03) than the Kaltostat group (30.7 ± 2.8 days). Conversely, the marked healing response elicited by Hyphecan on day 4 persisted on days 10 and 28 in contrast to Kaltostat, which had only a mild degree of healing response on days 10 and 28. The study suggests that wounds treated by Hyphecan heal faster than Kaltostat. Conclusion: The findings provide basic scientific evidence supporting the clinical use of Hyphecan in different wounds and might also reduce the cost of wound management as Hyphecan is cheaper than Kaltostat and requires a shorter treatment time.      

Serum ion levels after ceramic‐on‐ceramic and metal‐on‐metal total hip arthroplasty: 8‐year minimum follow‐up

Alternative bearing surfaces for total hip arthroplasty, such as metal‐on‐metal and ceramic‐on‐ceramic, offer the potential to reduce mechanical wear and osteolysis. In the short and medium term, the second generation of metal‐on‐metal bearings demonstrated high systemic metal ion levels, whereas ceramic‐on‐ceramic bearings showed the lowest ones. We aimed to verify whether the long‐term ion release in metal‐on‐metal subjects was still relevant at a median 10‐year follow‐up, and whether a fretting process at the modular junctions occurred in ceramic‐on‐ceramic patients and induced an ion dissemination. Serum levels were measured in 32 patients with alumina‐on‐alumina implants (group A), in 16 subjects with metal‐on‐metal implants (group B), and in 47 healthy subjects (group C). Group B results were compared with medium‐term findings. Cobalt and chromium levels were significantly higher in metal‐on‐metal implants than in ceramic‐on‐ceramic ones and controls. Nevertheless, ion levels showed a tendency to decrease in comparison with medium‐term content. In ceramic‐on‐ceramic implants, ion values were not significantly different from controls. Both in groups A and B, aluminum and titanium release were not significantly different from controls. In conclusion, negligible serum metal ion content was revealed in ceramic‐on‐ceramic patients. On the contrary, due to the higher ion release, metal‐on‐metal coupling must be prudently considered, especially in young patients, in order to obtain definitive conclusions. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res     

Investigation of High‐Speed Erythrocyte Flow and Erythrocyte‐Wall Impact in a Lab‐on‐a‐Chip

To better understand erythrocyte high‐speed motion, collision characteristics, and collision‐induced hemolysis probability in rotary blood pumps, a visual experimental investigation of high‐speed erythrocyte flow and erythrocyte‐wall collision in a lab‐on‐a‐chip was performed. The erythrocyte suspension was driven by a microsyringe pump connected to the microchip, and the erythrocyte flow and erythrocyte‐wall impact process were observed and imaged by an optical microscope and a high‐speed camera. Two types of microchips with different impact surfaces (flat and curved) were employed. The motion and deformation features before and after collision were studied in detail. The results show that erythrocytes not only move along the flow direction in the flow plane but also rotate and roll in three‐dimensional space. Erythrocytes keep discoid shape during the movement in the straight channel, but their deformations during collision are mainly classified into two types: erythrocyte structure is still stable and the erythrocyte performance can be ensured to a certain extent in the TypeA deformation, while the TypeB deformation makes the membrane more likely to fracture on the stretched side, increasing the probability of hemolysis. Furthermore, the movements and deformations of the erythrocytes after collision are analyzed and classified into two types: bouncing and slipping. Moreover, a simulation method for the flow in microchip was performed and validated through a comparison of the streamlines and experimental erythrocytes tracks, which can be further employed to predict the high‐speed blood flow, associated with collision process in mechanical blood pump.     

071TGF‐ß‐Mediated Paracrine Regulation of Keratinocyte Wound Closure

The importance of stromal‐epithelial interactions in wound healing is well established. These interactions likely involve autocrine and paracrine action of multiple growth factors, including members of the TGF‐ß family. TGF‐ß1, ß2 and ß3 isoforms signal by sequentially binding to the TGF‐ß type II and type I receptors, respectively. We address the role of TGF‐ß signaling in dermal fibroblasts using a conditional fibroblastic TGF‐ß type II receptor knockout mouse model (termed FßKO). We found that the loss of TGF‐ß signaling in the dermal fibroblasts results in accelerated excision‐wound closure compared with similar wounds in wild type mice. The mechanism of the altered rate of re‐epitheliaization in the FßKO mice was examined with regard to keratiocyte motility and proliferation. The migration of keratinocytes through collagen I coated 8 μm pore filters in the presence or absence of fibroblast‐conditioned media was tested. These experiments showed increased keratinocyte migration when incubated with FßKO dermal fibroblast conditioned media compared to media conditioned in wild type fibroblasts. Immuno‐histochemical staining of paraffin embedded intact skin indicated both wild type and FßKO mice had similar low levels of keratinocyte proliferation, based on Ki67 staining. In healing wounds, only the distal wound edges of wild type mice were proliferative. In contrast, the FßKO mice exhibited elevated proliferation across the length of the wound, including the leading edge of epithelial closure. Together our results suggest TGF‐ß signaling by the dermal fibroblasts suppresses re‐epithelialization of excision wounds by regulating keratinocyte motility and proliferation through paracrine mechanisms.
Funding: DOD BC99184 and NIH CA85492.     

Enhanced healing of goat femur‐defect using BMP7 gene‐modified BMSCs and load‐bearing tissue‐engineered bone

Segmental defect regeneration is still a clinical challenge. In this study, we investigated the feasibility of bone marrow stromal cells (BMSCs) infected with adenoviral vector containing the bone morphogenetic protein 7 gene (AdBMP7) and load‐bearing to enhance bone regeneration in a critically sized femoral defect in the goat model. The defects were implanted with AdBMP7‐infected BMSCs/coral (BMP7 group) or noninfected BMSCs/coral (control group), respectively, stabilized with an internal fixation rod and interlocking nails. Bridging of the segmental defects was evaluated by radiographs monthly, and confirmed by biomechanical tests. Much callus was found in the BMP7 group, and nails were taken off after 3 months of implantation, indicating that regenerated bone in the defect can be remodeled by load‐bearing, whereas after 6 months in control group. After load‐bearing, it is about 5 months; the mechanical property of newly formed bone in the BMP7 group was restored, but 8 months in control group. Our data suggested that the BMP7 gene‐modified BMSCs and load‐bearing can promote bone regeneration in segmental defects. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:412–418, 2010     

Low‐order multi‐rate linear time‐invariant decentralized trackers using the new observer‐based sub‐optimal method for unknown sampled‐data nonlinear time‐delay system with closed‐loop decoupling

This paper presents the low‐order multi‐rate linear time‐invariant decentralized trackers using the new observer‐based sub‐optimal method for a class of unknown sampled‐data nonlinear time‐delay system with closed‐loop decoupling. For the unknown sampled‐data nonlinear time‐delay system, we assume that the inner time delay is clearly known. Under this prerequisite, the appropriate (low‐) order decentralized linear observer for the unknown sampled‐data nonlinear system is determined by the off‐line observer/Kalman filter identification (OKID) method with artificial delay input and actual delay output. Then, the above observer has been further improved based on the proposed new observer‐based sub‐optimal approach. Sequentially, the decentralized tracker with the high gain property is proposed, so that the closed‐loop system has the decoupling property. The proposed approach constructs complete mathematics method including the concept of optimal control theory and state‐matching digital redesign technique and is quite useful for the complicated interconnected large‐scale sampled‐data nonlinear time‐delay system with unknown system equation. Copyright © 2010 John Wiley & Sons, Ltd.