James Chang - Academia.edu (original) (raw)

Papers by James Chang

Plastic and Reconstructive Surgery, 1997

Purpose: We previously reported the gene expression of epidermal growth factor (EGF) in the proce... more Purpose: We previously reported the gene expression of epidermal growth factor (EGF) in the process of decidualization in the human endometrium. This study was undertaken to investigate the biological significance of transforming growth factor-et (TGF-tx), which shares a significant sequence homology with EGF, in the regulation of decidualization. Methods: The gene encoding TGF-et was analyzed by Northern blot hybridization in nonpregnant human endometria and decidua from 6 to 8 weeks of gestation as well as in cultured stromal cells with or without medroxyprogesterone acetate. Results: No transcript was detected in proliferative and secretory endometrium, whereas a transcript of 4.8 kb, which was in agreement with the size of human prepro-TGF,-et mRNA previously reported, was clearly detected in decidua.

Journal of Hand Surgery-american Volume, 2002

Flexor tendon healing is complicated by adhesions to the surrounding sheath. Transforming growth ... more Flexor tendon healing is complicated by adhesions to the surrounding sheath. Transforming growth factor beta (TGF-beta) is a cytokine with numerous activities related to wound healing. We examined the effects of TGF-beta-1, -2 and -3 on tendon cell proliferation and collagen production. Three separate cell lines--sheath fibroblasts, epitenon and endotenon tenocytes--were isolated from rabbit flexor tendons and cultured separately. Cell culture media was supplemented with 1 or 5 ng/mL of TGF-beta-1, -2, or -3. Cell number and collagen I and III production were measured and compared with unsupplemented control cultures. The addition of TGF-beta to cell culture media resulted in a decrease in cell number in all 3 lines that did not reach statistical significance. There was a significant increase (p <.05) in collagen I and III production with the addition of all 3 TGF-beta isoforms. Modulation of TGF-beta production may provide a mechanism to modulate adhesion formation clinically.

Journal of Hand Surgery-american Volume, 1998

Basic fibroblast growth factor (bFGF) is a cytokine that plays a fundamental role in angiogenesis... more Basic fibroblast growth factor (bFGF) is a cytokine that plays a fundamental role in angiogenesis. This study examines bFGF messenger RNA (mRNA) expression in a rabbit flexor tendon wound healing model. Thirty-four New Zealand white rabbit forepaws underwent ...

Plastic and Reconstructive Surgery, 1999

Hemangiomas are benign vascular tumors of childhood that can lead to disfigurement and/or life-th... more Hemangiomas are benign vascular tumors of childhood that can lead to disfigurement and/or life-threatening consequences. The pathogenesis of hemangioma formation is likely to involve increased angiogenesis. Basic fibroblast growth factor and vascular endothelial growth factor are cytokines that stimulate angiogenesis in multiple in vivo and in vitro models. Proliferative hemangiomas have been found to have elevated levels of basic fibroblast growth factor and vascular endothelial growth factor protein, but the gene expression of these cytokines in human specimens has not been previously studied. We examined the gene expression and spatial distribution of basic fibroblast growth factor and vascular endothelial growth factor messenger RNA in proliferative versus involuted human hemangioma specimens using nonisotopic in situ hybridization techniques. Thirteen hemangioma specimens were harvested during initial surgical excision. In situ hybridization was performed on frozen sections of both proliferative and involuted hemangioma specimens using genetically engineered antisense probes specific for basic fibroblast growth factor and vascular endothelial growth factor messenger RNA. Controls were an interleukin-6 sense sequence and a transforming growth factor-beta 1 antisense sequence. A large number of cells within the specimens of proliferative hemangiomas revealed localized gene expression of basic fibroblast growth factor and vascular endothelial growth factor messenger RNA (626 +/- 129 and 1660 +/- 371 cells/mm2, respectively). The majority of the cells were endothelial in origin. In contrast, involuted hemangioma specimens revealed significantly lower numbers of cells staining positive for basic fibroblast growth factor and vascular endothelial growth factor messenger RNA (44 +/- 11 and 431 +/- 76 cells/mm2, respectively; p < 0.05). Transforming growth factor-beta 1 messenger RNA was slightly more expressed by involuted hemangiomas (117 +/- 30 cells/mm2). There were very low levels of transforming growth factor-beta 1 gene expression from proliferative hemangiomas (37 +/- 24 cells/mm2; p < 0.02). These data demonstrate that (1) in situ hybridization allows identification and relative quantitation of cells expressing messenger RNA for specific growth factors in human hemangioma specimens; (2) basic fibroblast growth factor and vascular endothelial growth factor messenger RNA are up-regulated in proliferative hemangiomas; and (3) transforming growth factor-beta 1 messenger RNA remains low in both proliferative and involuted hemangiomas. Because basic fibroblast growth factor and vascular endothelial growth factor messenger RNA have been implicated in the pathobiology of human hemangioma formation, biochemical modulation of these angiogenic cytokines may eventually help inhibit proliferation and promote regression of hemangiomas.

Plastic and Reconstructive Surgery, 1998

The mechanisms involved in normal cranial suture development and fusion as well as in the pathoph... more The mechanisms involved in normal cranial suture development and fusion as well as in the pathophysiology of craniosyostosis are not well understood. The purpose of this study was to investigate the expression of several cytokines--transforming growth factor-beta-1 (TGF-beta1), basic fibroblast growth factor (bFGF), and interleukin-6 (IL-6)--during cranial suture fusion. TGF-beta exists in three mammalian isoforms that are abundant in bone and stimulate calvarial bone formation when delivered locally. Other bone growth factors including basic fibroblast growth factor and the interleukins regulate bone growth and are mitogenic for bone marrow cells and osteoblasts. The involvement of growth factors in the pathophysiology of craniosynostosis is supported by recent genetics data linking fibroblast growth factor receptor mutations to syndromal craniosynostoses. In this experimental study, in situ hybridization was used to localize and quantify the gene expression of TGF-beta1, bFGF, and IL-6 during cranial suture fusion. In the Sprague-Dawley rat, the posterior frontal cranial suture normally undergoes fusion between 12 and 22 days of age, whereas all other cranial sutures remain patent. All in situ analyses of fusing posterior frontal sutures were compared with the patent, control, sagittal sutures. Posterior frontal and sagittal sutures, together with underlying dura, were harvested from rats at 8, 12, 16, and 35 days of postnatal life to analyze posterior frontal suture activity before, during, and after fusion. In situ hybridization was performed on frozen sections of these specimens using DNA probes specific for TGF-beta1, bFGF, and IL-6 mRNA. A negative control probe to IL-6 in the sense orientation was also used to validate the procedure. Cells expressing cytokine-specific mRNA were quantified (in cells positive per 10(-1) mm2) and analyzed using the unpaired Student's t test. Areas encompassing the fibrous suture and the surrounding bone plates were analyzed for cellular mRNA activity. IL-6 mRNA expression showed a minimal rise in the posterior frontal suture at days 12 and 16, with an average count of 10 and 6 cells per 10(-1) mm2, respectively. The sagittal suture remained negative for IL-6 mRNA at all time points. TGF-beta1 and bFGF analyses were most interesting, showing marked increases specifically in the posterior frontal suture during the time of active suture fusion. On postnatal day 8, a 1.5-fold increase in posterior frontal suture TGF-beta1 mRNA was found compared with sagittal sutures (p = 0.1890, unpaired Student's t test). This difference was increased 26-fold on day 12 in posterior frontal suture TGF-beta1 expression (p = 0.0005). By day 35, posterior frontal suture TGF-beta1 mRNA had nearly returned to prefusion levels, whereas TGF-beta1 mRNA levels in the sagittal suture remained low. A similar upregulation of bFGF mRNA, peaking at day 12, was observed in posterior frontal but not sagittal sutures (p = 0.0003). Furthermore, both TGF-beta1 and bFGF mRNA samples with intact dura showed an intense dural mRNA expression in the time preceding and during active posterior frontal suture fusion but not in sagittal tissues. Our data demonstrate that TGF-beta1 and bFGF mRNA are up-regulated in cranial suture fusion, possibly signaling in a paracrine fashion from dura to suture. TGF-beta1 and bFGF gene expression were dramatically increased both in and surrounding the actively fusing suture and followed the direction of fusion from endocranial to epicranial. These experimental data on bone growth factors support the recent human genetics data linking growth factor/fibroblast growth factor receptor deletions to syndromal craniosynostoses. The ultimate aim of these studies is to understand the underlying mechanisms regulating suture growth, development, and fusion so surgeons may one day manipulate the biology of premature cranial suture fusion.

Plastic and Reconstructive Surgery, 2000

The postoperative outcome of hand flexor tendon repair remains limited by tendon adhesions that p... more The postoperative outcome of hand flexor tendon repair remains limited by tendon adhesions that prevent normal range of motion. Recent studies using in situ hybridization techniques have implicated transforming growth factor beta-1 (TGF-beta1) in both intrinsic and extrinsic mechanisms of repair. TGF-beta1 is a growth factor that plays multiple roles in wound healing and has also been implicated in the pathogenesis of excessive scar formation. The purpose of this study was to examine the effect of neutralizing antibody to TGF-beta1 in a rabbit zone II flexor tendon wound-healing model. Twenty-two adult New Zealand White rabbits underwent complete transection of the middle digit flexor digitorum profundus tendon in zone II. The tendons were immediately repaired and received intraoperative infiltration of one of the following substances: (1) control phosphate-buffered saline; (2) 50 microg neutralizing antibody to TGF-beta1; (3) 50 microg each of neutralizing antibody to TGF-beta1 and to TGF-beta2. Eight rabbits that had not been operated on underwent analysis for determination of normal flexion range of motion at their proximal and distal interphalangeal joints, using a 1.2-N axial load applied to the flexor digitorum profundus tendon. All rabbits that had been operated on were placed in casts for 8 weeks to allow maximal tendon adhesion and were then killed to determine their flexion range of motion. Statistical analysis was performed using the Student's unpaired t test. When a 1.2-N load was used on rabbit forepaws that had not been operated on, normal combined flexion range of motion at the proximal and distal interphalangeal joints was 93+/-6 degrees. Previous immobilization in casts did not reduce the range of motion in these forepaws (93+/-4 degrees). In the experimental groups, complete transection and repair of the flexor digitorum profundus tendon with infiltration of control phosphate-buffered saline solution resulted in significantly decreased range of motion between the proximal and distal phalanges [15+/-6 degrees (n = 8)]. However, in the tendon repairs infiltrated with neutralizing antibody to TGF-beta1, flexion range of motion increased to 32+/-9 degrees (n = 7; p = 0.002). Interestingly, a combination of neutralizing antibody to TGF-beta1 and that to TGF-beta2 did not improve postoperative range of motion [18+/-4 degrees (n = 7; p = 0.234)]. These data demonstrate that (1) the rabbit flexor tendon repair model is useful for quantifying tendon scar formation on the basis of degrees of flexion between proximal and distal phalanges; (2) intraoperative infiltration of neutralizing antibody to TGF-beta1 improves flexor tendon excursion; and (3) simultaneous infiltration of neutralizing antibody to TGF-beta2 nullifies this effect. Because TGF-beta1 is thought to contribute to the pathogenesis of excessive scar formation, the findings presented here suggest that intraoperative biochemical modulation of TGF-beta1 levels limits flexor tendon adhesion formation.

Plastic and Reconstructive Surgery, 1997

Purpose: We previously reported the gene expression of epidermal growth factor (EGF) in the proce... more Purpose: We previously reported the gene expression of epidermal growth factor (EGF) in the process of decidualization in the human endometrium. This study was undertaken to investigate the biological significance of transforming growth factor-et (TGF-tx), which shares a significant sequence homology with EGF, in the regulation of decidualization. Methods: The gene encoding TGF-et was analyzed by Northern blot hybridization in nonpregnant human endometria and decidua from 6 to 8 weeks of gestation as well as in cultured stromal cells with or without medroxyprogesterone acetate. Results: No transcript was detected in proliferative and secretory endometrium, whereas a transcript of 4.8 kb, which was in agreement with the size of human prepro-TGF,-et mRNA previously reported, was clearly detected in decidua.

Journal of Hand Surgery-american Volume, 2002

Flexor tendon healing is complicated by adhesions to the surrounding sheath. Transforming growth ... more Flexor tendon healing is complicated by adhesions to the surrounding sheath. Transforming growth factor beta (TGF-beta) is a cytokine with numerous activities related to wound healing. We examined the effects of TGF-beta-1, -2 and -3 on tendon cell proliferation and collagen production. Three separate cell lines--sheath fibroblasts, epitenon and endotenon tenocytes--were isolated from rabbit flexor tendons and cultured separately. Cell culture media was supplemented with 1 or 5 ng/mL of TGF-beta-1, -2, or -3. Cell number and collagen I and III production were measured and compared with unsupplemented control cultures. The addition of TGF-beta to cell culture media resulted in a decrease in cell number in all 3 lines that did not reach statistical significance. There was a significant increase (p <.05) in collagen I and III production with the addition of all 3 TGF-beta isoforms. Modulation of TGF-beta production may provide a mechanism to modulate adhesion formation clinically.

Journal of Hand Surgery-american Volume, 1998

Basic fibroblast growth factor (bFGF) is a cytokine that plays a fundamental role in angiogenesis... more Basic fibroblast growth factor (bFGF) is a cytokine that plays a fundamental role in angiogenesis. This study examines bFGF messenger RNA (mRNA) expression in a rabbit flexor tendon wound healing model. Thirty-four New Zealand white rabbit forepaws underwent ...

Plastic and Reconstructive Surgery, 1999

Hemangiomas are benign vascular tumors of childhood that can lead to disfigurement and/or life-th... more Hemangiomas are benign vascular tumors of childhood that can lead to disfigurement and/or life-threatening consequences. The pathogenesis of hemangioma formation is likely to involve increased angiogenesis. Basic fibroblast growth factor and vascular endothelial growth factor are cytokines that stimulate angiogenesis in multiple in vivo and in vitro models. Proliferative hemangiomas have been found to have elevated levels of basic fibroblast growth factor and vascular endothelial growth factor protein, but the gene expression of these cytokines in human specimens has not been previously studied. We examined the gene expression and spatial distribution of basic fibroblast growth factor and vascular endothelial growth factor messenger RNA in proliferative versus involuted human hemangioma specimens using nonisotopic in situ hybridization techniques. Thirteen hemangioma specimens were harvested during initial surgical excision. In situ hybridization was performed on frozen sections of both proliferative and involuted hemangioma specimens using genetically engineered antisense probes specific for basic fibroblast growth factor and vascular endothelial growth factor messenger RNA. Controls were an interleukin-6 sense sequence and a transforming growth factor-beta 1 antisense sequence. A large number of cells within the specimens of proliferative hemangiomas revealed localized gene expression of basic fibroblast growth factor and vascular endothelial growth factor messenger RNA (626 +/- 129 and 1660 +/- 371 cells/mm2, respectively). The majority of the cells were endothelial in origin. In contrast, involuted hemangioma specimens revealed significantly lower numbers of cells staining positive for basic fibroblast growth factor and vascular endothelial growth factor messenger RNA (44 +/- 11 and 431 +/- 76 cells/mm2, respectively; p < 0.05). Transforming growth factor-beta 1 messenger RNA was slightly more expressed by involuted hemangiomas (117 +/- 30 cells/mm2). There were very low levels of transforming growth factor-beta 1 gene expression from proliferative hemangiomas (37 +/- 24 cells/mm2; p < 0.02). These data demonstrate that (1) in situ hybridization allows identification and relative quantitation of cells expressing messenger RNA for specific growth factors in human hemangioma specimens; (2) basic fibroblast growth factor and vascular endothelial growth factor messenger RNA are up-regulated in proliferative hemangiomas; and (3) transforming growth factor-beta 1 messenger RNA remains low in both proliferative and involuted hemangiomas. Because basic fibroblast growth factor and vascular endothelial growth factor messenger RNA have been implicated in the pathobiology of human hemangioma formation, biochemical modulation of these angiogenic cytokines may eventually help inhibit proliferation and promote regression of hemangiomas.

Plastic and Reconstructive Surgery, 1998

The mechanisms involved in normal cranial suture development and fusion as well as in the pathoph... more The mechanisms involved in normal cranial suture development and fusion as well as in the pathophysiology of craniosyostosis are not well understood. The purpose of this study was to investigate the expression of several cytokines--transforming growth factor-beta-1 (TGF-beta1), basic fibroblast growth factor (bFGF), and interleukin-6 (IL-6)--during cranial suture fusion. TGF-beta exists in three mammalian isoforms that are abundant in bone and stimulate calvarial bone formation when delivered locally. Other bone growth factors including basic fibroblast growth factor and the interleukins regulate bone growth and are mitogenic for bone marrow cells and osteoblasts. The involvement of growth factors in the pathophysiology of craniosynostosis is supported by recent genetics data linking fibroblast growth factor receptor mutations to syndromal craniosynostoses. In this experimental study, in situ hybridization was used to localize and quantify the gene expression of TGF-beta1, bFGF, and IL-6 during cranial suture fusion. In the Sprague-Dawley rat, the posterior frontal cranial suture normally undergoes fusion between 12 and 22 days of age, whereas all other cranial sutures remain patent. All in situ analyses of fusing posterior frontal sutures were compared with the patent, control, sagittal sutures. Posterior frontal and sagittal sutures, together with underlying dura, were harvested from rats at 8, 12, 16, and 35 days of postnatal life to analyze posterior frontal suture activity before, during, and after fusion. In situ hybridization was performed on frozen sections of these specimens using DNA probes specific for TGF-beta1, bFGF, and IL-6 mRNA. A negative control probe to IL-6 in the sense orientation was also used to validate the procedure. Cells expressing cytokine-specific mRNA were quantified (in cells positive per 10(-1) mm2) and analyzed using the unpaired Student's t test. Areas encompassing the fibrous suture and the surrounding bone plates were analyzed for cellular mRNA activity. IL-6 mRNA expression showed a minimal rise in the posterior frontal suture at days 12 and 16, with an average count of 10 and 6 cells per 10(-1) mm2, respectively. The sagittal suture remained negative for IL-6 mRNA at all time points. TGF-beta1 and bFGF analyses were most interesting, showing marked increases specifically in the posterior frontal suture during the time of active suture fusion. On postnatal day 8, a 1.5-fold increase in posterior frontal suture TGF-beta1 mRNA was found compared with sagittal sutures (p = 0.1890, unpaired Student's t test). This difference was increased 26-fold on day 12 in posterior frontal suture TGF-beta1 expression (p = 0.0005). By day 35, posterior frontal suture TGF-beta1 mRNA had nearly returned to prefusion levels, whereas TGF-beta1 mRNA levels in the sagittal suture remained low. A similar upregulation of bFGF mRNA, peaking at day 12, was observed in posterior frontal but not sagittal sutures (p = 0.0003). Furthermore, both TGF-beta1 and bFGF mRNA samples with intact dura showed an intense dural mRNA expression in the time preceding and during active posterior frontal suture fusion but not in sagittal tissues. Our data demonstrate that TGF-beta1 and bFGF mRNA are up-regulated in cranial suture fusion, possibly signaling in a paracrine fashion from dura to suture. TGF-beta1 and bFGF gene expression were dramatically increased both in and surrounding the actively fusing suture and followed the direction of fusion from endocranial to epicranial. These experimental data on bone growth factors support the recent human genetics data linking growth factor/fibroblast growth factor receptor deletions to syndromal craniosynostoses. The ultimate aim of these studies is to understand the underlying mechanisms regulating suture growth, development, and fusion so surgeons may one day manipulate the biology of premature cranial suture fusion.

Plastic and Reconstructive Surgery, 2000

The postoperative outcome of hand flexor tendon repair remains limited by tendon adhesions that p... more The postoperative outcome of hand flexor tendon repair remains limited by tendon adhesions that prevent normal range of motion. Recent studies using in situ hybridization techniques have implicated transforming growth factor beta-1 (TGF-beta1) in both intrinsic and extrinsic mechanisms of repair. TGF-beta1 is a growth factor that plays multiple roles in wound healing and has also been implicated in the pathogenesis of excessive scar formation. The purpose of this study was to examine the effect of neutralizing antibody to TGF-beta1 in a rabbit zone II flexor tendon wound-healing model. Twenty-two adult New Zealand White rabbits underwent complete transection of the middle digit flexor digitorum profundus tendon in zone II. The tendons were immediately repaired and received intraoperative infiltration of one of the following substances: (1) control phosphate-buffered saline; (2) 50 microg neutralizing antibody to TGF-beta1; (3) 50 microg each of neutralizing antibody to TGF-beta1 and to TGF-beta2. Eight rabbits that had not been operated on underwent analysis for determination of normal flexion range of motion at their proximal and distal interphalangeal joints, using a 1.2-N axial load applied to the flexor digitorum profundus tendon. All rabbits that had been operated on were placed in casts for 8 weeks to allow maximal tendon adhesion and were then killed to determine their flexion range of motion. Statistical analysis was performed using the Student's unpaired t test. When a 1.2-N load was used on rabbit forepaws that had not been operated on, normal combined flexion range of motion at the proximal and distal interphalangeal joints was 93+/-6 degrees. Previous immobilization in casts did not reduce the range of motion in these forepaws (93+/-4 degrees). In the experimental groups, complete transection and repair of the flexor digitorum profundus tendon with infiltration of control phosphate-buffered saline solution resulted in significantly decreased range of motion between the proximal and distal phalanges [15+/-6 degrees (n = 8)]. However, in the tendon repairs infiltrated with neutralizing antibody to TGF-beta1, flexion range of motion increased to 32+/-9 degrees (n = 7; p = 0.002). Interestingly, a combination of neutralizing antibody to TGF-beta1 and that to TGF-beta2 did not improve postoperative range of motion [18+/-4 degrees (n = 7; p = 0.234)]. These data demonstrate that (1) the rabbit flexor tendon repair model is useful for quantifying tendon scar formation on the basis of degrees of flexion between proximal and distal phalanges; (2) intraoperative infiltration of neutralizing antibody to TGF-beta1 improves flexor tendon excursion; and (3) simultaneous infiltration of neutralizing antibody to TGF-beta2 nullifies this effect. Because TGF-beta1 is thought to contribute to the pathogenesis of excessive scar formation, the findings presented here suggest that intraoperative biochemical modulation of TGF-beta1 levels limits flexor tendon adhesion formation.