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Biomedical subjects

T A Mustoe

Publications and source records attributed to T A Mustoe.

At least 73 records · Page 4Linked to original sources

Continuous versus conventional tissue expansion: experimental verification of a new technique.

Historically, tissue expansion is a prolonged process, typically requiring at least 6 weeks to complete. Recently, interest has increased in shortening this time period. In the current study, a continuous infusion device maintaining constant expander pressure less than capillary filling pressure was used in a canine model in seven dogs to minimize the time period needed to achieve significant expansion. There were no complications, except one device malfunction, corrected by changes in design. The process was shown to be a safe and effective means of producing amounts of expansion similar to traditional methods in approximately 72 hours, with expansion of 28 percent (n = 6) for continuous tissue expansion (CTE) versus 34 percent (n = 6) for a 2-week rapid expansion protocol. This expansion was derived from either stretch of preexisting tissue (46 percent for CTE, 35 percent for 2-week expansion) or recruitment of adjacent tissue. The clinical application of continuous tissue expansion could permit the advantages of tissue expansion to be obtained in many more situations than are currently available to traditional tissue expansion techniques.

Animals↗

Growth factors and wound healing: platelet-derived growth factor as a model cytokine.

Cytokines such as the platelet-derived growth factor (PDGF) have the potential to initiate and mediate many if not all of the complex biological responses associated with inflammation and wound healing. PDGF is a potent cytokine that may be used to illustrate the diverse activities initiated by the interactions of PDGF with its receptor relevant to the inflammatory response and subsequent wound repair. Because PDGF can chemotactically attract, activate, and initiate new expression of quiescent genes (e.g. the small inducible gene, SIG, family), it fulfills the predictions anticipated of a candidate wound hormone. PDGF added directly to experimental wounds in animals enhances wound healing, which suggests that cytokines will become increasingly important as therapeutic agents in the treatment of wounds in humans.

Animals↗

Growth factor-induced acceleration of tissue repair through direct and inductive activities in a rabbit dermal ulcer model.

The roles of polypeptide growth factors in promoting wound healing and in directing the specificity and sequence of responses of different tissues in wounds are little understood. We investigated the influence of four growth factors on the rates of healing of a novel full thickness dermal ulcer placed on an avascular base in the rabbit ear. The wound model precludes significant wound contraction and requires new granulation tissue and epithelial cells for healing to originate centripetally. 5 micrograms (7-31 pmol/mm2) of platelet-derived growth factor-B chain (PDGF-BB), basic fibroblast growth factor (bFGF), and epidermal growth factor (EGF) applied locally at the time of wounding resulted in a twofold increase in complete reepithelialization of treated wounds (PDGF-BB, P = 0.02 chi square analysis; bFGF, P = 0.04; EGF, P = 0.05); transforming growth factor (TGF)-beta 1 significantly inhibited reepithelialization (P = 0.05). Both PDGF-BB and TGF-beta 1 uniquely increased the depth and area of new granulation tissue (P less than 0.005), the influx of fibroblasts, and the deposition of new matrix into wounds. Explants from 7-d old PDGF-BB-treated wounds remained metabolically far more active than controls, incorporating 473% more [3H]thymidine into DNA (P = 0.05) and significantly more [3H]leucine and [3H]proline into collagenase-sensitive protein (P = 0.04). The results establish that polypeptide growth factors have significant and selective positive influences on healing of full thickness ulcers in the rabbit.

Animals↗

Collagenase production at the border of granulation tissue in a healing wound: macrophage and mesenchymal collagenase production in vivo.

We demonstrated the cells producing collagenase and the time course of collagenase-production at early stages of wound healing, using histology and two immunohistochemical procedures on cross sections of rat skin harvested 0, 3, 5, 7 and 12 days after full-thickness incisions. A monospecific rabbit polyclonal antibody to neutral collagenase purified from rat myometrial cells was used to demonstrate collagenase production. Specificity of this reaction was confirmed by blocking the reaction with excess homogeneously purified antigen. Macrophages were simultaneously labelled using a mouse anti-rat monoclonal antibody recognizing exclusively mature macrophages. Intracellular collagenase was not reliably detectable at day 0, but was prominent at days 3 and 5 and thereafter declined. Double labeling technique showed occasional macrophages producing collagenase in the developing granulation tissue, but most cells labeled as macrophages were negative for collagenase. Most activity was found in fibroblasts adjacent to granulation tissue elements. Since the granulation tissue parallels revascularization in a dendritic pattern, a cross section at three days typically shows an annulus of collagenase-positive cells surrounding a branch of the active granulation tissue. At days 5, 7 and 12 after wounding the pattern of collagenase expression became indistinct as more tissue was involved in the granulation process. However, double-labelling for macrophages and collagenase showed the dichotomy between collagenase expression and presence of macrophages to persist. The finding that collagenase is produced in connective tissue adjacent to granulation tissue suggests an inductive process, possibly due to diffusion of cytokines produced by granulation tissue elements.

Animals↗

Platelet-derived growth factor-BB and transforming growth factor beta 1 selectively modulate glycosaminoglycans, collagen, and myofibroblasts in excisional wounds.

Recombinant platelet-derived growth factor (PDGF) and transforming growth factor beta 1 (TGF-beta 1) influence the rate of extracellular matrix formed in treated incisional wounds. Because incisional healing processes are difficult to quantify, a full-thickness excisional wound model in the rabbit ear was developed to permit detailed analyses of growth-factor-mediated tissue repair. In the present studies, quantitative and qualitative differences in acute inflammatory cell influx, glycosaminoglycan (GAG) deposition, collagen formation, and myofibroblast generation in PDGF-BB (BB homodimer)- and TGF-beta 1-treated wounds were detected when analyzed histochemically and ultrastructurally. Although both growth factors significantly augmented extracellular matrix formation and healing in 10-day wounds compared with controls (P less than 0.002). PDGF-BB markedly increased macrophage influx and GAG deposition, whereas TGF-beta 1 selectively induced significantly more mature collagen bundles at the leading edge of new granulation tissue (P = 0.007). Transforming growth factor-beta 1-treated wound fibroblasts demonstrated active collagen fibrillogenesis and accretion of subfibrils at the ultrastructural level. Myofibroblasts, phenotypically modified fibroblasts considered responsible for wound contraction, were observed in control, but were absent in early growth-factor-treated granulating wounds. These results provide important insights into the mechanisms of soft tissue repair and indicate that 1) PDGF-BB induces an inflammatory response and provisional matrix synthesis within wounds that is qualitatively similar but quantitatively increased compared with normal wounds; 2) TGF-beta 1 preferentially triggers synthesis and more rapid maturation of collagen within early wounds; and 3) both growth factors inhibit the differentiation of fibroblasts into myofibroblasts, perhaps because wound contraction is not required, due to increased extracellular matrix synthesis.

Animals↗

Quantitative analysis of inflammatory cell influx, procollagen type I synthesis, and collagen cross-linking in incisional wounds: influence of PDGF-BB and TGF-beta 1 therapy.

Platelet-derived growth factor (PDGF-BB homodimer) and transforming growth factor-beta 1 (TGF-beta 1) are potent wound-healing hormones that accelerate incisional repair. To identify more precisely and quantitatively the stage(s) of wound healing influenced by growth-factor therapy, we investigated the three sequential tissue repair processes--inflammatory cell influx, intracellular procollagen type I (PC-I) synthesis, and collagen cross-linking--in recombinant growth factor--treated wounds. Using newly developed automated, quantitative image-analysis techniques, we observed that PDGF-BB markedly augmented the directed migration of macrophages into wounds during the first week after wounding and triggered and earlier and more sustained influx of PC-I--containing fibroblasts into the wound when compared with results in TGF-beta 1-treated or control wounds (p = 0.015 at day 2; p = 0.007 at day 21). In contrast, automated image analysis revealed TGF-beta 1-treated wound fibroblasts had a nearly twofold increase in intracellular levels of PC-I protein when compared with PDGF-BB-treated or control wound fibroblasts (p = 0.004 at day 4). However, the influence of TGF-beta 1 was transient, and the longer duration of PDGF-BB activity suggested a later influence, perhaps on the collagen remodeling phase, which is ultimately required for increased wound strength. To address this possibility, collagen cross-linking in growth factor-treated wounds was inhibited by beta-aminoproprionitrile (BAPN) treatment, and wound breaking strength was analyzed. Both PDGF-BB and TGF-beta 1 continued to enhance repair in BAPN-treated rats, indicating that they do not function primarily at the level of collagen cross-linking. Thus, PDGF-BB appears to enhance the inflammatory phase of wound healing to indirectly trigger PC-I synthesis, whereas TGF-beta 1 quantitatively enhances PC-I synthesis directly, accounting for their differing duration of activities within healing wounds.

Aminopropionitrile↗

Effects of ischemia on ulcer wound healing: a new model in the rabbit ear.

To study the effects of alteration of blood flow on wound healing in rabbit ear ulcers, two models were designed that produced maximum ischemia and maximum congestion, respectively, with complete survival of the ear by selective division of one or more of three arteries or veins and circumferential incisions. After selection of the best models from six variations, tissue perfusion was measured indirectly by venous oxygen tension, dermofluorometry, pulse oximetry, and skin temperature. Wound healing was measured seven days after creating 6-mm surgical ulcers. The tissue oxygen tension calculated from the venous oxygen tension fell to 30 mm Hg through days 1, 3, and 7 in the ischemic ears, and skin temperature and blood flow measured by dermofluorometry were similarly affected. However, there was no evidence of significant change in tissue perfusion except increased skin temperature in the congested ears. None of the ischemic wounds were epithelialized completely, but half of the control and congested wounds were. The granulation tissue formation was decreased (39% of the area versus 63% of the area) and the infection rate was increased (20% versus 2%) significantly in the ischemic wounds compared with the control wounds but not in the congested wounds. The ischemic ulcer model is reproducible and quantifiable and is potentially a useful model for examining agents to improve ulcer healing where blood flow is decreased. The congestion model showed no significant changes in blood flow or wound healing.

Animals↗

Refinements of nasalis myocutaneous flap.

During the last 3 years, we have applied the nasalis myocutaneous island flap for reconstruction of nasal defects following excision of skin basal cell carcinoma and melanoma in 19 patients. By refinements with Z plasty, early dermabrasion, and placement of a bolster, we could minimize the trapdoor deformity, obvious scars, and blunting of the alar groove. No patients required revisional surgery, and flap survival was 100%. On the basis of our experience, the nasalis myocutaneous island flap is the solution for reconstruction of moderate-sized distal nasal defects in terms of reliability, aesthetics, and simplicity.

Adult↗

Current concepts in wound healing: growth factor and macrophage interaction.

Growth factors are potent wound healing promoters which accelerate incisional wound repair by distinct mechanisms. Transforming growth factor-beta (TGF-beta), a chemotactic factor, increases synthesis of extracellular matrix and stimulates granulation tissue. We demonstrated that a single topical dose of TGF-beta increased the wound breaking strength in normal models of tissue repair as well as in models of impaired wound repair, characterized by severe monocytopenia. PDGF, a chemotactic agent for inflammatory cells, with mitogenic activity, activates monocytes and stimulates collagen production, significantly increased the wound breaking strength with effects that lasted for up to 47 days. In contrast to TGF-beta, PDGF was only active in normal models of wound healing and its effects were dependent upon the presence of macrophages. PAF is a glycerophospholipid which chemotaxes and activates macrophages, but differs from growth factors in lacking mitogenic activity. A single topical dose of PAF significantly increased the wound breaking strength and promoted macrophage migration.

Animals↗

Transforming growth factor-beta. Effect on soft tissue repair.

Previous studies have demonstrated that TGF-beta possesses many of the biologic properties necessary for acceleration of the normal wound healing process. We report that recombinant human TGF-beta 2 (rhuTGF-beta 1) increases wound strength and accelerates wound closure when applied topically to experimental wounds. Doses of 5 to 1,000 ng/wound increased wound strength in a dose-response manner and wound strength increase as high as 161% above control in the rat incisional wound model. Increased wound strength was observed as early as 3 days following rhuTGF-beta 1 application and continued to Day 28. In the rabbit ear ulcer model, acceleration of wound closure was observed following doses of 5 to 100 ng/wound applied a single topical application. No adverse effects of rhuTGF-beta 1 were observed. The amount of fibrous tissue, scar formation, and mitotic figures were not significantly greater than control. Epithelialization of rhuTGF-beta 1-treated wounds was not impeded. rhuTGF-beta 1 induced bone formation in the rabbit ear ulcer model but not in the rat incisional model, suggesting that precursor cells, such as perichondrial cells, are required for the bone forming activities of TGF-beta 1.

Animals↗

Differential acceleration of healing of surgical incisions in the rabbit gastrointestinal tract by platelet-derived growth factor and transforming growth factor, type beta.

Anastomotic dehiscence is a major cause of morbidity and mortality in gastrointestinal surgery. A unique model system of a gastric incision was developed to test the potential of polypeptide growth factors to enhance wound healing. Paired, deep partial-thickness incisions to but not including the gastric mucosa were made. A single topical application of transforming growth factor, type beta 1 (TGF-beta), platelet-derived growth factor, or control vehicle at the time of wounding was given. Wound breaking strength and detailed histologic analyses of wounds were evaluated as a function of time after wounding. TGF-beta (0.1 to 2.0 micrograms/wound) demonstrated a bimodal, dose-dependent acceleration of wound breaking strength 7 days after gastric wounding. An approximate 4-day acceleration of gastric wound breaking strength by TGF-beta (2 micrograms/wound) was seen at 7 and 11 days. Wounds treated with platelet-derived growth factor (10 micrograms/wound) displayed an increased cellular response but no enhancement of breaking strength at 7 and 11 days. These results demonstrate the ability of TGF-beta to accelerate gastrointestinal tissue repair by topical application and suggest significant potential for the use of growth factors in enhancing repair of surgical wounds of the gastrointestinal tract.

Animals↗

Reversal of impaired wound healing in irradiated rats by platelet-derived growth factor-BB.

This study examined the potential influence of platelet-derived growth factor-BB homodimers (PDGF-BB) on surgical incisions in irradiated animals with depressed wound healing. Rats were irradiated with either 800 rads total body or 2,500 rads surface irradiation. Parallel dorsal skin incisions were made 2 days later, and PDGF-BB was applied topically a single time to one of two incisions. In total body-irradiated rats, bone marrow-derived elements were severely depressed, wound macrophages were virtually eliminated, and PDGF-BB treatment was ineffective. However, in surface-irradiated rats, PDGF-BB treatment recruited macrophages into wounds and partially reversed impaired healing on day 7 (p less than 0.005) and day 12 (p less than 0.001). PDGF-BB-treated wounds were 50 percent stronger than the paired control wounds. The results suggest PDGF requires bone marrow-derived cells, likely wound macrophages, for activity and that it may be useful as a topical agent in postirradiation surgical incisions.

Animals↗

Primary intraosseous carcinoma of the mandible with probable origin in an odontogenic cyst.

Primary intraosseous carcinoma of the jaws (PIOC) is an uncommon lesion, but may not be as rare as commonly believed. Since the putative source of the epithelium giving rise to an intraosseous carcinoma is the epithelium involved in odontogenesis, these lesions are often designated as odontogenic carcinomas. These tumors may theoretically arise (1) from the lining of odontogenic cysts, (2) from other epithelial odontogenic tumors, or (3) de novo from presumed odontogenic rests. While not included in most classifications of PIOC, it appears logical to also include intraosseous mucoepidermoid carcinomas as a fourth type of PIOC. A case of primary intraosseous squamous cell carcinoma of the mandible, with evidence of origin in an odontogenic cyst, is presented. The recent literature on carcinomas arising in jaw cysts is reviewed.

Carcinoma, Squamous Cell↗

Transforming growth factor beta reverses the glucocorticoid-induced wound-healing deficit in rats: possible regulation in macrophages by platelet-derived growth factor.

Transforming growth factor beta (TGF-beta) and the platelet-derived growth factor (PDGF) are potent mitogenic polypeptides which enhance rates of wound healing in experimental animals; in contrast, glucocorticoids inhibit wound repair. The potential of TGF-beta and PDGF to reverse this inhibition in healing was tested in methylprednisolone-treated rats with deficits in skin wound strength of 50%. Single applications of TGF-beta (10-40 pmol per wound, 0.25-1 micrograms) applied locally at the time of wounding fully reversed this deficit in a concentration-dependent and highly reproducible manner. Wounds in glucocorticoid-treated animals were characterized by a near total absence of neutrophils and macrophages and by a delayed influx and reduced density of fibroblasts; however, such wounds treated with TGF-beta showed significant increases in wound fibroblasts and in intracellular procollagen type I. PDGF did not reverse the deficit in wound breaking strength in glucocorticoid-treated rats; there were more fibroblasts in the PDGF-treated wounds, but these fibroblasts lacked the enhanced expression of procollagen type I found in TGF-beta-treated wounds. The wound macrophages, required for normal tissue repair, remained absent from both PDGF- and TGF-beta-treated wounds in glucocorticoid-treated animals. This result suggested that macrophages might normally act as an intermediate in the induction of procollagen synthesis in fibroblasts of PDGF-treated wounds and that TGF-beta might bypass the macrophage through its capacity to stimulate directly new synthesis of procollagen type I in fibroblasts. Whereas PDGF does not stimulate procollagen synthesis, in a rodent macrophage cell line, PDGF induced a highly significant, time-dependent enhancement of expression of TGF-beta.

Animals↗

Platelet-derived growth factor and transforming growth factor-beta enhance tissue repair activities by unique mechanisms.

Platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) markedly potentiate tissue repair in vivo. In the present experiments, both in vitro and in vivo responses to PDGF and TGF-beta were tested to identify mechanisms whereby these growth factors might each enhance the wound-healing response. Recombinant human PDGF B-chain homodimers (PDGF-BB) and TGF-beta 1 had identical dose-response curves in chemotactic assays with monocytes and fibroblasts as the natural proteins from platelets. Single applications of PDGF-BB (2 micrograms, 80 pmol) and TGF-beta 1 (20 micrograms, 600 pmol) were next applied to linear incisions in rats and each enhanced the strength required to disrupt the wounds at 5 d up to 212% of paired control wounds. Histological analysis of treated wounds demonstrated an in vivo chemotactic response of macrophages and fibroblasts to both PDGF-BB and to TGF-beta 1 but the response to TGF-beta 1 was significantly less than that observed with PDGF-BB. Marked increases of procollagen type I were observed by immunohistochemical staining in fibroblasts in treated wounds during the first week. The augmented breaking strength of TGF-beta 1 was not observed 2 and 3 wk after wounding. However, the positive influence of PDGF-BB on wound breaking strength persisted through the 7 wk of testing. Furthermore, PDGF-BB-treated wounds had persistently increased numbers of fibroblasts and granulation tissue through day 21, whereas the enhanced cellular influx in TGF-beta 1-treated wounds was not detectable beyond day 7. Wound macrophages and fibroblasts from PDGF-BB-treated wounds contained sharply increased levels of immunohistochemically detectable intracellular TGF-beta. Furthermore, PDGF-BB in vitro induced a marked, time-dependent stimulation of TGF-beta mRNA levels in cultured normal rat kidney fibroblasts. The results suggest that TGF-beta transiently attracts fibroblasts into the wound and may stimulate collagen synthesis directly. In contrast, PDGF is a more potent chemoattractant for wound macrophages and fibroblasts and may stimulate these cells to express endogenous growth factors, including TGF-beta, which, in turn, directly stimulate new collagen synthesis and sustained enhancement of wound healing over a more prolonged period of time.

Animals↗

Management of synovial sarcoma of the median nerve at the elbow.

Synovial sarcoma is a high-grade malignancy with a marked propensity for local recurrence and a moderate rate of regional lymph node involvement. It usually causes death from massive pulmonary metastases. Despite its aggressive biologic behavior, en bloc wide local resection of small extremity tumors rather than amputation may be indicated if removal of all gross disease is possible. Extremity morbidity from resection of vessels, nerves, and soft-tissue bulk can be minimized by the use of composite reconstruction techniques currently available. A case report is presented to illustrate aggressive limb-sparing surgical therapy of a small, favorably located synovial sarcoma with immediate neurovascular and soft-tissue reconstruction. The literature is reviewed to aid subsequent surgeons faced with management of this uncommon tumor.

Abdominal Muscles↗