Nicholas Bastidas

Progenitor cell trafficking is regulated by hypoxic gradients through HIF-1 induction of SDF-1

The trafficking of circulating stem and progenitor cells to areas of tissue damage is poorly understood. The chemokine stromal cell–derived factor-1 (SDF-1 or CXCL12) mediates homing of stem cells to bone marrow by binding to CXCR4 on circulating cells. SDF-1 and CXCR4 are expressed in complementary patterns during embryonic organogenesis and guide primordial stem cells to sites of rapid vascular expansion. However, the regulation of SDF-1 and its physiological role in peripheral tissue repair remain incompletely understood. Here we show that SDF-1 gene expression is regulated by the transcription factor hypoxia-inducible factor-1 (HIF-1) in endothelial cells, resulting in selective in vivo expression of SDF-1 in ischemic tissue in direct proportion to reduced oxygen tension. HIF-1-induced SDF-1 expression increases the adhesion, migration and homing of circulating CXCR4-positive progenitor cells to ischemic tissue. Blockade of SDF-1 in ischemic tissue or CXCR4 on circulating cells prevents progenitor cell recruitment to sites of injury. Discrete regions of hypoxia in the bone marrow compartment also show increased SDF-1 expression and progenitor cell tropism. These data show that the recruitment of CXCR4-positive progenitor cells to regenerating tissues is mediated by hypoxic gradients via HIF-1-induced expression of SDF-1.

Topical Vascular Endothelial Growth Factor Accelerates Diabetic Wound Healing through Increased Angiogenesis and by Mobilizing and Recruiting Bone Marrow-Derived Cells

Diminished production of vascular endothelial growth factor (VEGF) and decreased angiogenesis are thought to contribute to impaired tissue repair in diabetic patients. We examined whether recombinant human VEGF(165) protein would reverse the impaired wound healing phenotype in genetically diabetic mice. Paired full-thickness skin wounds on the dorsum of db/db mice received 20 microg of VEGF every other day for five doses to one wound and vehicle (phosphate-buffered saline) to the other. We demonstrate significantly accelerated repair in VEGF-treated wounds with an average time to resurfacing of 12 days versus 25 days in untreated mice. VEGF-treated wounds were characterized by an early leaky, malformed vasculature followed by abundant granulation tissue deposition. The VEGF-treated wounds demonstrated increased epithelialization, increased matrix deposition, and enhanced cellular proliferation, as assessed by uptake of 5-bromodeoxyuridine. Analysis of gene expression by real-time reverse transcriptase-polymerase chain reaction demonstrates a significant up-regulation of platelet-derived growth factor-B and fibroblast growth factor-2 in VEGF-treated wounds, which corresponds with the increased granulation tissue in these wounds. These experiments also demonstrated an increase in the rate of repair of the contralateral phosphate-buffered saline-treated wound when compared to wounds in diabetic mice never exposed to VEGF (18 days versus 25 days), suggesting that topical VEGF had a systemic effect. We observed increased numbers of circulating VEGFR2(+)/CD11b(-) cells in the VEGF-treated mice by fluorescence-activated cell sorting analysis, which likely represent an endothelial precursor population. In diabetic mice with bone marrow replaced by that of tie2/lacZ mice we demonstrate that the local recruitment of bone marrow-derived endothelial lineage lacZ+ cells was augmented by topical VEGF. We conclude that topical VEGF is able to improve wound healing by locally up-regulating growth factors important for tissue repair and by systemically mobilizing bone marrow-derived cells, including a population that contributes to blood vessel formation, and recruiting these cells to the local wound environment where they are able to accelerate repair. Thus, VEGF therapy may be useful in the treatment of diabetic complications characterized by impaired neovascularization.

Mechanical strain alters gene expression in an in vitro model of hypertrophic scarring

Fibroblasts represent a highly mechanoresponsive cell type known to play key roles in normal and pathologic processes such as wound healing, joint contracture, and hypertrophic scarring. In this study, we used a novel fibroblast-populated collagen lattice (FPCL) isometric tension model, allowing us to apply graded biaxial loads to dermal fibroblasts in a 3-dimensional matrix. Cell morphology demonstrated dose-dependent transition from round cells lacking stress fibers in nonloaded lattices to a broad, elongated morphology with prominent actin stress fibers in 800-mg-loaded lattices. Using quantitative real-time RT-PCR, a dose dependent induction of both collagen-1 and collagen-3 mRNA up to 2.8- and 3-fold, respectively, as well as a 2.5-fold induction of MMP-1 (collagenase) over unloaded FPCLs was observed. Quantitative expression of the proapoptotic gene Bax was down-regulated over 4-fold in mechanically strained FPCLs. These results suggest that mechanical strain up-regulates matrix remodeling genes and down-regulates normal cellular apoptosis, resulting in more cells, each of which produces more matrix. This “double burden” may underlie the pathophysiology of hypertrophic scars and other fibrotic processes in vivo.

Posterior cranial vault expansion using distraction osteogenesis

PurposePosterior vault expansion using distraction osteogenesis has become a vital instrument in our institution, particularly as a first-line treatment in syndromic craniosynostosis. In this review, we highlight the several advantages, diverse utility, and technicalities of the operative procedure.MethodsA review of the literature and explanation of the technical details of the procedures were described in this manuscript.Results/conclusionPosterior cranial vault distraction offers several benefits over traditional expansion procedures.

Power-assisted Suction Lipectomy of Fasciocutaneous Flaps in the Extremities

Background:A bulky appearance is one of the major patient complaints after extremity reconstruction after fasciocutaneous flaps. Serial debulking procedures with staged excision are required to improve aesthetic and functional outcome, but these methods risk injury to the vascular pedicle and often require multiple procedures for adequate thinning of the flap. We suggest the use of power-assisted suction lipectomy for the debulking of fasciocutaneous flaps in the upper and lower extremities as a safe, effective, and efficient procedure. Methods:From 2006 to 2009, we performed power-assisted suction lipectomy on the upper and lower extremities of 16 flaps in 15 patients who had previously undergone reconstruction with fasciocutaneous flaps after a traumatic injury. Results:There was 100% flap survival without any complications. Only 2 of the 16 (12.5%) flaps required a secondary revision for further contouring. Conclusions:In our experience power-assisted suction lipectomy is a safe and excellent adjunct in fasciocutaneous flap debulking and reduces the number of secondary revision procedures necessary. We recommend its use as an adjunct in debulking and contouring flaps used in extremity reconstruction.

Closed mallet thumb injury: a review of the literature and case study of the use of magnetic resonance imaging in deciding treatment.

At present, the literature dedicated to closed mallet thumb injury offers conflicting evidence between conservative and operative approaches. Although conservative treatment is often successful, retraction of the extensor pollicis tendon may lead to improper reattachment and continued deformity. This discussion and case report serve to highlight the use of magnetic resonance imaging as an adjunct in selecting the proper treatment strategy for this injury at initial presentation.

Successful replantation of an amputated nose after dog bite injury

A54-year-old man was brought to the Bellevue Hospital Emergency Room 30 minutes after a complete left nose amputation secondary to a dog bite injury (Fig 1). The amputated segment was appropriately transported, wrapped in moistened gauze and placed on ice. The patient did not smoke and was otherwise healthy. Tetanus immune-globulin and Unasyn were given in the emergency room. Gross inspection of the nose revealed a full-thickness avulsion/ amputation traversing several aesthetic subunits, including one half of the left dorsum, sidewall, ala, and one half of the nasal tip. After discussing risks, benefits, and alternatives of an attempted replantation surgery, he was brought to the operating room for an attempt at microvascular restoration of the avulsed left nose. In the operating room he was given 325 mg of rectal aspirin. The avulsed segment was examined under the microscope, upon which an artery was identified and marked with 10-0 nylon suture. Under loupe magnification, the facial wound was carefully debrided of all grossly damaged and nonviable tissue. A small branch of the dorsal nasal artery and two candidate recipient veins were identified. The amputated part was then aligned with the patient’s nasal defect and the mucosa repaired using 5-0 catgut sutures. The artery was anastomosed with four 10-0 nylon sutures using standard microsurgical techniques, with immediate restoration of blood flow to the replanted part. The cartilaginous segments were then repaired using 5-0 PDS. Attention was then brought to venous repair. Donor and recipient veins were mobilized but sufficient length for tension-free anastomosis was not possible; given the small caliber of the veins, a vein graft was not attempted. Venous anastomosis was not performed and the skin was closed with interrupted 6-0 nylon

Melanoma Extirpation with Immediate Reconstruction: The Oncologic Safety and Cost Savings of Single-Stage Treatment.

BACKGROUND The timing of reconstruction following melanoma extirpation remains controversial, with some advocating definitive reconstruction only when the results of permanent pathologic evaluation are available. The authors evaluated oncologic safety and cost benefit of single-stage neoplasm extirpation with immediate reconstruction. METHODS The authors reviewed all patients treated with biopsy-proven melanoma followed by immediate reconstruction during a 3-year period (January of 2011 to December of 2013). Patient demographic data, preoperative biopsies, operative details, and postoperative pathology reports were evaluated. Cost analysis was performed using hospital charges for single-stage surgery versus theoretical two-stage surgery. RESULTS During the study period, 534 consecutive patients were treated with wide excision and immediate reconstruction, including primary closure in 285 patients (55 percent), local tissue rearrangement in 155 patients (30 percent), and skin grafting in 78 patients (15 percent). The mean patient age was 67 years (range, 19 to 98 years), and the median follow-up time was 1.2 years. Shave biopsy was the most common diagnostic modality, resulting in tumor depth underestimation in 30 patients (6.0 percent). Nine patients (2.7 percent) had positive margins on permanent pathologic evaluation. The only variables associated with positive margins were desmoplastic melanoma (p = 0.004) and tumor location on the cheek (p = 0.0001). The mean hospital charge for immediate reconstruction was

A Novel Approach to Keloid Reconstruction with Bilaminar Dermal Substitute and Epidermal Skin Grafting.

22,528 compared with the theoretical mean charge of

Acellular Dermal Matrix for Temporary Coverage of Exposed Critical Neurovascular Structures in Extremity Wounds

35,641 for delayed reconstruction, leading to mean savings of 38.5 percent (SD, 7.9 percent). CONCLUSION This large series demonstrates that immediate reconstruction can be safely performed in melanoma patients with an acceptable rate of residual tumor requiring reoperation and significant health care cost savings. CLINICAL QUESTION/LEVEL OF EVIDENCE Therapeutic, IV.