Effect of Delayed Oncoplastic Reduction Mammoplasty on Radiation Treatment Delay Following Breast-Conserving Surgery for Breast Cancer.

BACKGROUND: The purpose of this study was to evaluate the delay in initiating adjuvant radiation therapy (RT) after breast-conserving surgery (BCS) in patients with early-stage breast cancer who underwent oncoplastic reduction mammoplasty (ORM) following BCS compared with a matched cohort of patients who did not undergo ORM between BCS and RT. METHODS: Medical records of 112 women (56 ORMs and 56 matched non-ORMs) with carcinoma in situ or early-stage breast cancer treated with BCS were reviewed. ORM was performed in a delayed manner following BCS, allowing confirmation of negative surgical margins. Time to RT was defined as time from last oncologic surgery to start of RT. RESULTS: The median follow-up time was 6.8 years for the ORM cohort and 6.7 years for the control non-ORM cohort. Patients who underwent ORM following BCS experienced a significant delay in initiating RT (>8 weeks) than matched patients not undergoing ORM (66% vs. 34%; p < 0.001). Wound complications occurred in 44.6% (n = 25) of patients in the ORM cohort, which were mostly minor, including delayed wound healing and/or infection (39%). There was no significant difference in local recurrence between patients in the non-ORM and ORM cohorts (p = 0.32). CONCLUSIONS: This study demonstrates that ORM following BCS has the potential to delay RT >8 weeks, largely as a result of increased risk of wound complications; however, this delay did not impact local control. ORM can be safely considered for appropriately selected patients with breast cancer.

Anatomic Location of Tissue Expander Placement Is Not Associated With Delay in Adjuvant Therapy in Women With Breast Cancer.

BACKGROUND: Tissue expanders in breast reconstruction are traditionally placed retropectoral. Increasingly, patients are undergoing prepectoral placement. The impact of this placement on the initiation of adjuvant treatment is unknown. METHODS: A retrospective review was conducted to identify women diagnosed with breast cancer who underwent mastectomy followed by radiation and/or chemotherapy. Women were divided into 3 groups: prepectoral tissue expander placement, retropectoral tissue expander placement, and no immediate reconstruction. A treatment delay was defined as greater than 8 weeks between tissue expander placement and adjuvant therapy. RESULTS: Of 634 women, 205 (32%) underwent tissue expander placement, and 429 (68%) did not have immediate reconstruction. Of those with tissue expanders placed, 84 (41%) had prepectoral placement, and 121 (59%) had retropectoral placement. The median time to adjuvant therapy was 49 days for the entire cohort: no reconstruction, 47 days; prepectoral, 57 days; and retropectoral, 55 days. Treatment delays were observed in 34% of women: no reconstruction, 28%; prepectoral, 51%; and retropectoral, 46% ( P < 0.001). Tissue expander placement was associated with a delay to adjuvant therapy when compared with no reconstruction ( P < 0.001). The location of the tissue expander did not impact the odds of having a delay. On multivariable analysis, having reconstruction, having postoperative infection, not undergoing chemotherapy treatment, and being a current smoker were associated with a delay to adjuvant therapy. A delay to treatment was not associated with worse survival. CONCLUSIONS: Placement of a tissue expander delayed adjuvant therapy. The location of tissue expander placement, retropectoral versus prepectoral, did not impact the time to adjuvant treatment.

Reducing Postoperative Abdominal Bulge Following Deep Inferior Epigastric Perforator Flap Breast Reconstruction with Onlay Monofilament Poly-4-Hydroxybutyrate Biosynthetic Mesh.

Background The purpose of this study was to evaluate the use of a biosynthetic mesh onlay on reducing postoperative abdominal bulge following deep inferior epigastric perforator (DIEP) flap breast reconstruction. Methods All patients undergoing DIEP reconstructions from January, 2010 to January, 2014 at a tertiary center were reviewed. Patients were divided into two groups for comparison based on whether a biosynthetic mesh onlay (Phasix [monofilament poly-4-hydroxybutyrate], Bard Inc., Warwick, RI) was used for reinforcement of the anterior rectus fascia. Rates of postoperative abdominal bulge were compared between the groups utilizing standard statistical methods. Results During the study period, 319 patients underwent 553 DIEP reconstructions, 160 (50.2%) used mesh and 159 (49.8%) did not (nonmesh). The mean follow-up was 16.4 ± 11.1 months. There was no difference in age (49 ± 9.3 years), current tobacco use, diabetes, or mean body mass index (BMI, 29.4 ± 4.4) between the mesh and nonmesh groups (p > 0.05); however, there was a higher proportion of obese patients (BMI > 30) in the mesh group (45.0 vs. 33.3%; p = 0.03). Abdominal bulge rate following DIEP with mesh was lower than the nonmesh group (0 vs. 5.0%; p = 0.004). In the entire sample, 234 (73.4%) underwent bilateral DIEP and 85 (26.6%) underwent unilateral DIEP. In unilateral DIEP patients, the bulge rate was similar between the mesh and nonmesh groups (0 vs. 4.4%; p > 0.05); however, in bilateral DIEP patients, the bulge rate was lower in the mesh group compared with a nonmesh group (0 vs. 5.5%; p = 0.008). Conclusion Reinforcement of the anterior rectus with an onlay monofilament poly-4-hydroxybutyrate biosynthetic mesh may reduce the risk of postoperative bulge rate in patients undergoing DIEP reconstruction.

Novel Approaches to Breast Reconstruction.

As breast oncologic surgical procedures and approaches have evolved in recent years, so have breast reconstruction techniques. Newer advances focus on expanding the options of reconstructive approaches and patient selection, optimizing quality of life, and helping improve postsurgical survivorship. These advances span from techniques to expand criteria for nipple-sparing mastectomies, optimizing and enhancing oncoplastic surgery, evolving autologous reconstruction options, and preserving and restoring sensation after mastectomy.

Bridging autologous reconstruction with pre-pectoral tissue expanders.

Pre-pectoral reconstruction is steadily becoming more mainstream with recent publications showing equivalent results with traditional sub-pectoral published literature. Multiple authors have demonstrated short-term acceptable rates of infection, expander failure, success in radiated patients, and overall patient satisfaction. Some data has even shown improved outcomes in prepectoral reconstruction when compared to published subpectoral literature. For the past 4 years, our practices have utilized a "piggy-back" method of immediate pre-pectoral expander reconstruction before performing delayed immediate microsurgical free tissue transfers. This method has many advantages and has in many cases become our standard for patients wanting deep inferior epigastric perforator flaps (DIEPs) for definitive reconstruction.

Does the use of biopatch devices at drain sites reduce perioperative infectious complications in patients undergoing immediate tissue expander breast reconstruction?

BACKGROUND: To decrease the rate of infectious complications, surgeons have begun to use Biopatch (Ethicon, Somerville, N.J.) disks at drain exit sites. The authors investigated whether use of a Biopatch disk could convey a reduction in perioperative infections in patients undergoing immediate tissue expander breast reconstruction. METHODS: A retrospective review was conducted of all patients undergoing tissue expander/implant breast reconstruction from November of 2010 to November of 2012 at a single institution. Breasts were divided into two cohorts: controls with traditional adhesive dressings and those with Biopatch disks at drain sites. Breasts were compared based on demographics, complications, drain duration, and antibiotic type. RESULTS: A total of 1211 breasts met inclusion criteria. The control group (November of 2010 to October of 2011) included 606 breasts. The Biopatch cohort (November of 2011 to October of 2012) included 605 breasts. When comparing breasts with disks to controls, there were no statistical differences in overall infection (6.2 versus 7.4 percent; p = 0.4235), major infection (4.0 versus 4.3 percent; p = 0.8853), need for explantation (2.2 versus 1.8 percent; p = 0.5372), and mastectomy skin flap necrosis (12.6 versus 14.6 percent; p = 0.3148). However, age greater than 50 years, diabetes mellitus, hypertension, hypercholesterolemia, obesity, history of prior breast irradiation, and mastectomy skin flap necrosis were independent predictors of infectious complications. CONCLUSIONS: Biopatch disks do not reduce the rate infectious complications in patients undergoing immediate tissue expander breast reconstruction. Other conventional risks, including medical comorbidities, obesity, and mastectomy skin flap necrosis, remain significantly associated with infectious complications. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Vascular endothelial growth factor inhibits bone morphogenetic protein 2 expression in rat mesenchymal stem cells.

INTRODUCTION: While several studies report that bone morphogenetic proteins (BMPs) and vascular endothelial growth factor (VEGF) can act synergistically to improve bone tissue engineering, others suggest that VEGF inhibits osteogenesis. The purpose of these experiments was therefore to evaluate the effect of dual transfection of these growth factors and potential mechanisms of interaction on gene expression and osteogenesis in vitro and in vivo. METHODS: Marrow-derived mesenchymal stem cells (MSCs) were exposed to recombinant VEGF protein or transfected with adenoviruses encoding BMP2, VEGF, or LacZ in a variety of ratios. Alterations in gene and protein expression in vitro as well as bone formation in vivo were assessed. RESULTS: MSC exposure to AdV-VEGF or recombinant VEGF inhibited BMP2 mRNA expression, protein production, and MSC differentiation. Coculture experiments revealed that BMP2 suppression occurs through both an autocrine and a paracrine mechanism, occurring at the transcriptional level. Compared to controls, cotransfection of VEGF and BMP2 transgenes prevented ectopic bone formation in vivo. CONCLUSION: VEGF is a potent inhibitor of BMP2 expression in MSCs, and supplementation or overexpression of VEGF inhibits osteogenesis in vitro and ectopic bone formation in vivo. Strategies to utilize MSCs in bone tissue engineering therefore require careful optimization and precise delivery of growth factors for maximal bone formation.

Synthesis of a tissue-engineered periosteum with acellular dermal matrix and cultured mesenchymal stem cells.

Periosteal grafts can aid in bone repair by providing bone progenitor cells and acting as a barrier to scar tissue. Unfortunately, these grafts have many of the same disadvantages as bone grafts (donor site morbidity and limited donor sites). In this article, we describe a method of synthesizing a periosteum-like material using acellular human dermis and osteoblasts or mesenchymal stem cells (MSC). We show that osteoblasts readily attach to and proliferate on the acellular human dermis in vitro. In addition, osteoblasts retained the potential for differentiation in response to bone morphogenetic protein stimulation. Cells grown on the acellular human dermis were efficiently transfected with adenoviruses with no evidence of cellular toxicity. To assess for in vivo cell delivery and bone-forming potential, the acellular human dermis was seeded with green fluorescent protein (GFP)-positive MSCs, transfected with bone morphogenetic protein 2, wrapped around the adductor muscle in syngeneic mice, and used to treat critical-sized mandibular defects in nude rats. After 3 weeks, GFP-positive cells were still present, and bone had replaced the interface between the muscle and the constructs. After 6 weeks, critical-sized bone defects had been successfully healed. In conclusion, we show that an acellular human dermis can be used to synthesize a tissue-engineered periosteum capable of delivering cells and osteoinductive proteins.

Fibrosis is a key inhibitor of lymphatic regeneration.

BACKGROUND: Lymphedema is a common debilitating sequela of lymph node dissection. Although numerous clinical studies suggest that factors that lead to fibrosis are associated with the development of lymphedema, this relationship has not been proven. The purpose of these experiments was therefore to evaluate lymphatic regeneration in the setting of variable soft-tissue fibrosis. METHODS: A section of mouse tail skin including the capillary and collecting lymphatics was excised. Experimental animals (n = 20) were treated with topical collagen type I gel and a moist dressing, whereas control animals (n = 20) underwent excision followed by moist dressing alone. Fibrosis, acute lymphedema, lymphatic function, gene expression, lymphatic endothelial cell proliferation, and lymphatic fibrosis were evaluated at various time points. RESULTS: Collagen gel treatment significantly decreased fibrosis, with an attendant decrease in acute lymphedema and improved lymphatic function. Tails treated with collagen gel demonstrated greater numbers of lymphatic vessels, more normal lymphatic architecture, and more proliferating lymphatic endothelial cells. These findings appeared to be independent of vascular endothelial growth factor C expression. Decreased fibrosis was associated with a significant decrease in the expression of extracellular matrix components. Finally, decreased soft-tissue fibrosis was associated with a significant decrease in lymphatic fibrosis as evidenced by the number of lymphatic endothelial cells that coexpressed lymphatic and fibroblast markers. CONCLUSIONS: Soft-tissue fibrosis is associated with impairment in lymphatic regeneration and lymphatic function. These defects occur as a consequence of impaired lymphatic endothelial cell proliferation, abnormal lymphatic microarchitecture, and lymphatic fibrosis. Inhibition of fibrosis using a simple topical dressing can markedly accelerate lymphatic repair and promote regeneration of normal capillary lymphatics.

Accelerating stem cell proliferation by down-regulation of cell cycle regulator p21.

BACKGROUND: Tissue engineering is often limited by the time required for culture expansion of cells necessary for scaffold seeding. Cell cycle regulators control entry and exit into the cell cycle and as such regulate cellular proliferation rates. The authors hypothesized that transient alteration in cell cycle regulators can be utilized as a means to accelerate stem cell proliferation. METHODS: Mesenchymal stem cells were harvested from wild-type mice and mice deficient in the cell cycle regulator p21. Wild-type cells were treated with small interfering RNA against p21 in two- or three-dimensional cultures in vitro. Cellular proliferation and the potential for cellular differentiation into the bone or fat lineage were assessed. RESULTS: Mesenchymal stem cells treated with small interfering RNA targeting p21 demonstrated a significant decrease in p21 protein and mRNA expression 96 hours after treatment. They also proliferated significantly faster than control cells (2.5 to three times) in both two- and three-dimensional culture. Similarly, cells harvested from p21-deficient mice demonstrated a significant acceleration in cellular proliferation. Inhibition of p21 expression was not associated with significant changes in spontaneous cellular differentiation. However, transient p21 inhibition promoted both osteoblastic and adipogenic differentiation when cells were exposed to differentiation medium. CONCLUSIONS: Transient inhibition of the cell cycle regulator p21 results in significant acceleration of mesenchymal stem cell proliferation without promoting spontaneous cellular differentiation. Exposure to differentiation medium results in increased cellular differentiation toward the osteoblast and fat lineage. Manipulation of cell cycle regulators may represent a novel means by which stem cell proliferation can be accelerated, thereby decreasing the time required for scaffold synthesis in tissue engineering.

Fractionated doses of ionizing radiation confer protection to mesenchymal stem cell pluripotency.

BACKGROUND: Although it is clear that radiation therapy can cause tissue injury, the degree of injury that is observed clinically can be highly variable. It is possible that variability in the methods by which ionizing radiation is delivered can contribute to some of the observed variability. Thus, the purpose of this study was to assess the effects of various fractionation schedules on the growth and differentiation potential of isolated mesenchymal stem cells in vitro. METHODS: Isolated mesenchymal stem cells (triplicate studies) were exposed to a dose of 12 Gy of ionizing radiation as a single dose, in two doses of 6 Gy, or in six doses of 2 Gy. Cellular proliferation and the potential for differentiation along the bone and fat lineage were assessed. Potential mechanisms for injury and protection were evaluated by analyzing the expression of p21 and manganese superoxide dismutase. RESULTS: Delivery of radiation in multiple doses confers significant radioprotection to mesenchymal stem cell proliferation and potential for differentiation. In contrast, delivery of 12 Gy of radiation as a single dose or as two equal doses of 6 Gy results in marked deficiencies in cellular proliferation and potential for multilineage cellular differentiation. CONCLUSIONS: The authors have demonstrated that even minor alterations in fractionation of radiation dose can result in significant effects on the potential of mesenchymal stem cells to differentiate. These findings imply that at least some of the variability in tissue damage after radiation therapy observed clinically may be attributable to differences in the delivery of ionizing radiation.

TGF-beta1 is a negative regulator of lymphatic regeneration during wound repair.

Although clinical studies have identified scarring/fibrosis as significant risk factors for lymphedema, the mechanisms by which lymphatic repair is impaired remain unknown. Transforming growth factor -beta1 (TGF-beta1) is a critical regulator of tissue fibrosis/scarring and may therefore also play a role in the regulation of lymphatic regeneration. The purpose of this study was therefore to assess the role of TGF-beta1 on scarring/fibrosis and lymphatic regeneration in a mouse tail model. Acute lymphedema was induced in mouse tails by full-thickness skin excision and lymphatic ligation. TGF-beta1 expression and scarring were modulated by repairing the wounds with or without a topical collagen gel. Lymphatic function and histological analyses were performed at various time points. Finally, the effects of TGF-beta1 on lymphatic endothelial cells (LECs) in vitro were evaluated. As a result, the wound repair with collagen gel significantly reduced the expression of TGF-beta1, decreased scarring/fibrosis, and significantly accelerated lymphatic regeneration. The addition of recombinant TGF-beta1 to the collagen gel negated these effects. The improved lymphatic regeneration secondary to TGF-beta1 inhibition was associated with increased infiltration and proliferation of LECs and macrophages. TGF-beta1 caused a dose-dependent significant decrease in cellular proliferation and tubule formation of isolated LECs without changes in the expression of VEGF-C/D. Finally, the increased expression of TGF-beta1 during wound repair resulted in lymphatic fibrosis and the coexpression of alpha-smooth muscle actin and lymphatic vessel endothelial receptor-1 in regenerated lymphatics. In conclusion, the inhibition of TGF-beta1 expression significantly accelerates lymphatic regeneration during wound healing. An increased TGF-beta1 expression inhibits LEC proliferation and function and promotes lymphatic fibrosis. These findings imply that the clinical interventions that diminish TGF-beta1 expression may be useful in promoting more rapid lymphatic regeneration.

Ionizing radiation of mesenchymal stem cells results in diminution of the precursor pool and limits potential for multilineage differentiation.

BACKGROUND: Although ionizing radiation is an important treatment modality for a number of malignancies, it can be associated with significant morbidity. The exact mechanisms by which ionizing radiation results in cellular injury remain unknown. Mesenchymal stem cells give rise to a number of tissues including bone, fat, and cartilage and provide an excellent cellular model with which to evaluate the effects of ionizing radiation on cellular survival and function. METHODS: Rat mesenchymal stem cells were irradiated with 0, 7, and 12 Gy of ionizing radiation and assessed for changes in growth, apoptosis, cell-cycle profile, senescence, differentiation, and gene expression. RESULTS: Ionizing radiation resulted in a significant decrease in cellular proliferation because of increased apoptosis, G2 cell-cycle arrest, and premature senescence. In addition, ionizing radiation caused low-level spontaneous osteoblastic differentiation. Conversely, cellular differentiation in response to lineage-specific culture conditions for bone, fat, and cartilage was markedly decreased in irradiated cells, thereby demonstrating a deficit in the ability of irradiated mesenchymal stem cells to respond to environmental stimuli. CONCLUSIONS: Although the majority of mesenchymal stem cells survive injury from ionizing radiation, this injury results in a significant decrease in cellular proliferation. Furthermore, the differentiation potential of irradiated mesenchymal stem cells in response to environmental stimuli is markedly diminished. Thus, the negative effects of ionizing radiation may result from a decreased pool of progenitor cells with limited differentiation potential. Proposed radioprotection strategies aiming to reduce tissue injury should therefore evaluate not only cellular survival but also cellular function.