loitrriril of lrrterrrul Medicirie 1992 : 232 : 397-404
Association between high levels of growth factors in plasma and progression of coronary atherosclerosis J. NILSSON*. S. VOLK-JOVINGE*, J. SVENSSON§, C. L A N D O U t , U. D E FAIKE' & A. HAMSTEN* Frorri tlie *Ilcpnrtrrierit of Medicine orrd tlie tDepnrtrrient of Tliorocic Hodiology. Kirrg Gustcc/ V Rrsrurclr Iristiticte. Krrroliriskn Hospitul. arid tlie EjDepartrfreritO/ Cliriical Clicirrisfrq, Ilnridergd Hospitnl. Kuroliriskn Iristitrrte. Stockholirr. Sweden
Abstract. Nilsson J , Volk-Jovinge S. Svensson J. Landou C. de Faire U. Hamsten A (Department of Medicine and Department of Thoracic Radiology, King Gustaf V Kesearch Institute. Karolinska Hospital, and Department of Clinical Chemistry, Danderyd Hospital. Karolinska Institute. Stockholm, Sweden). Association between high levels of growth factors in plasma and progression of coronary atherosclerosis. loiirnul of Internul Medicine 1 9 9 2 : 232: 397-404. Although intimal proliferation of smooth muscle cells (SMC) is recognized as one of the key mechanisms in the development of atherosclerosis, our knowledge of the role of circulating growth factors for SMC in this process is limited. I n the present study the plasma levels of platelet-derived growth factor (PDCF), P-thromboglobulin (P-TG). platelet factor 4 (PF 4) and total growth factor activity were determined in a group of 3 0 young postinfarction patients who had participated in an angiographic study of mechanisms associated with progression of coronary atherosclerosis. Significant correlations were found between the total growth factor activity in plasma and progression ( r = 0.42. I-' llL
H1L2 ~
‘I’G
Chol
‘I’G
Chol
TG
Chol
0.25 -0.21
0.04 0.24
-0.20 -0.46**
-0.14 0.11
-0.2 I -0.25
0.52*
0.04
0.01
0.3 1
0.3h
0.33
Chol = cholesterol, ‘IT = triglycerides. I’artial correlation cocfficients with coronary scores at reangiography used as dependcnt variables and the age of thc patients lirst entered in the regression modcl as ti forced variable. * P < 0.01, **p < 0.05.
402
J . N I L S S O N et a/.
between the growth factor activity in plasma and established risk factors such as LDI, cholesterol concentration, a diagnosis of hypertension or tobacco consumption (data not shown).
Discussion Intimal proliferation of SMC is regarded as one of the key processes in the development of atherosclerosis. Considerable attention has been focused on the possible role of the two growth factors PDGF and FGF in this process. It was initially proposed that proliferation of SMC in the intimal layer of the arterial wall occurred in response to PDGF released from aggregating platelets at sites of endothelial injury [29]. However, recent data from animal experiments indicate that PDGF and FGF released from cells in the vascular wall may be of greater importance [2]. The aim of the present investigation was to determine whether there is any association between the plasma levels of growth factors for SMC and the development of coronary lesions in patients with premature coronary heart disease. The growth factor activity of platelet-poor plasma was assessed by analysing its ability to stimulate DNA synthesis in cultured human arterial SMC. This method provides an estimate of the net effects of growth factors and growth inhibitors present in plasma. but does not allow identification of the nature of the growth-promoting activity. The use of platelet-poor plasma is critical in this analysis, since serum contains large amounts of PDGF released from platelets which under normal conditions do not reach the cells in the vessel wall. Simultaneous analysis of P-TG and PF-4 makes it possible to exclude artefactual release of PDGF from platelets during blood sampling. The results suggest that there is a significant association between the growth factor activity for SMC in plasma and the global severity and rate of progression of coronary atherosclerosis, which is independent of established metabolic and clinical risk factors. This finding is in agreement with the observation of increased levels of plasma growth factors in young survivors of myocardial infarction [24], and supports the view that growth factors may play a role in the development of coronary atherosclerosis. As discussed above, the growth factor activity assay does not allow identification of the nature of the growth-promoting activity. In a n attempt to resolve this problem, the presence of PDGF
in plasma was analysed by radioimmunoassay. Although there was a significant correlation between the levels of PDGF and growth factor activity in plasma, the analysis indicated that less than 2 0 % of the growth factor activity was accounted for by PDGF. In an earlier study 1241, addition of PDGF antibodies inhibited up to 40% of the growth factor activity in plasma of patients with cardiovascular disease. The reason for this discrepancy has yet to be determined. Furthermore, there was no association between the PDGF concentration in plasma and the global severity or rate of progression of coronary atherosclerosis. Assuming that the growth-promoting activity of plasma is due to factors other than PDGF, FGF is one possible candidate. FGF is synthesized in endothelial cells and SMC. but is not normally secreted from these cells. It has been suggested that release of FGF takes place as a result of cell injury 1161. Thus it is possible that FGF is released from perturbed endothelial cells covering atherosclerotic plaques, which would result in an increase in growth factor activity in plasma. Interestingly, earlier studies have demonstrated ii relationship between the plasma concentration of the von Willebrand factor (which has been suggested to be a marker of endothelial injury) and the plasma growth factor activity 1301. IGF-1 is another growth factor normally present in human plasma 121 I. IGF1 is in itself a weak mitogen for SMC, but it may potentiate the mitogenic effect of other growth factors. such as PDGF and FGF [31. 321. The IFG-I gene is expressed in cultured SMC. and its expression is enhanced by exogenous IGF-1, a finding compatible with the existence of an endogenous growth stimulatory loop 1331. Plasma levels of PDGF, P-TG and PF 4 did not correlate with the atherosclerosis scores. In contrast, the level of PDCF was significantly related to the number and severity of distinct stenoses. This association may be due to release of PDGF from mechanically injured platelets. Indeed, several investigators have reported that coronary artery disease is associated with an increase in platelet consumption [34-3 61. The important question remains as to whether the increased plasma level of growth factor for SMC observed in the present investigation is the cause or the result of the disease. The retrospective design of the study makes it impossible to answer this question. Clearly, prospective studies arc needed to resolve this issue. Furthermore. the mechanisms regulating
GKOW‘I’H FACTORS AND CORONARY ATHEROSCLEROSIS
401
‘l’:ible 3. Kelations of plasma growth factor activity and serum lipoprotein lipid concentrations to progression of coronary atherosclerosis ~
~
~
~
~~
lmJ
VISIL
HDL
HIII,,
Growth factor activity Chol
’I’G
Chol
‘I’G
Chol
‘I’G
Chol
0.42*
0.08
0.11
0.02
-0,li
-0.14
0.17
~
Progression of coronary atherosclerosis
0.03
~
Cho = cholesterol. ‘I’G = triglyccrides. I’ertial correlation coefficients with difference in coronary atherosclerosis scores between the first and second angjograms used as dependent variables and tinic between the angiograms first entered in the regression model as a forced variable. * P < 0.05.
W
$
0
.I 4 -E
8
z 5 -m
3-
f
I -
.** a.
2-
*.
n m
f
.
0
5-
Table 4. Relations of the plasma levels of the threc plateletderived proteins 0-TG. I’F 4 and P I X F to global severity of coronary lesions and progression of diffuse atherosclerosis
P-TG I’F 4 PDGF
*.
*.
=*
.*.
(b’
0
10
Stenoses score
Progression of diffuse athcromatosis
-0 08 0 11 -0 10
0 20 0 41 0 40*
-0 26 - 0 04 -0 0 1
Partial correlation coefficients with coronary scores of reangiography and difference in coronary atherosclerosis scores between the first and second angiograms used as dependent variables and the age of the patients and the time between the angiograms. respectively, used as forced variables. * P < 0.05. j- PDGF was determined in 26 patients, and P-TG and PI74 were determined in 24 patients.
0
5
Athcrosclerosis score
15
20
25
30
Growth factor activity (% labelled nuclei) Fig. 1. I’lasniii growth factor activity in relation to (a) global atherosclerosis score and (b) atherosclerosis progression score. The plasma growth ftictor activity is expressed as percentage atrtor;itliographicaily labclled nuclei after exposure of cultured human SMC to medium containing 2 % patient plasma and 2 pCi nil-’ of “H-thymidine for 2 4 h.
quantify platelet release. P-TG and PF 4 are stored together with PDGF in the a-granules of platelets, and their plasma levels reflect the amount of PDGF released from platelets into plasma. The plasma of 14 patients contained no detectable I’DGF (this assay detects PDGP concentrations above 0.5 ng ml-I). The IWGF level in the plasma of the remaining patients varied between 0.7 and 10.2 ng ml-’. There were no associations between the plasma levels of PDGF, p‘I’G and PF 4 and the rate of progression of global athcrosclerosis (Table 4). nor did the plasma levels of
Table 5. Spearman rank correlation coefficicnts between plasma growth factor activity and plasma concentrations of plateletspecific proteinst
Plasma growth factor activity PIIGF
PDGF
P-TG
PF4
0.40*
-0.41
-0.1 3
0.27
0.32
* P < 0.05.
t PDGF was determincd in 26 patients and P-TG and PF4 were determined in 24 patients. the three platelet-derived proteins differ between patients with or without progression or appearance of new stenotic lesions (data not shown). However, the plasma level of PDGP was significantly associated with the number and severity of coronary stenoses at reangiography (Table 4). The growth factor activity in plasma correlated positively with the plasma level of PDGF ( r = 0.40, P < 0.05), and tended to be inversely correlated with the plasma level of P-TG (Table 5). There were no statistically significant associations between the levels of PDGF and P-TG and 1’F 4 (Table 5). No associations were found
GROWTH FACTORS AND CORONARY ATHEROSCLEROSIS
plasma levels of growth factors have to be clarified. However, assuming that the release of growth factors into plasma occurred as a result of existing atherosclerotic lesions, it is still possible that this release per se may contribute to disease progression. Some evidence in support of this possibility has come from studies performed in rats which showed that systemic infusion of FGF markedly increases the replication of intimal SMC following balloon injury of the aorta 13 71. The relationship between plasma growth factor activity and global severity as well as progression of coronary atherosclerosis found in the present study obviously requires confirmation. It is also unknown whether it is present in other age groups, in women and in subjects with premature coronary artery disease but no previous myocardial infarction. Although our observation could have major scientific and clinical implications, much more research is needed before expectations of therapeutic consequences can be raised. At the present time, associations and causations should be clearly distinguished when interpreting the existing data.
Acknowledgements This study was supported by the Swedish Heart-Lung Foundation, the Swedish Medical Research Council (8311. 8691). the Knut and Alice Wallenberg Foundation, King Gustaf V 80th Birthday Fund and thc Nanna Svartz Fund. Dr Hamsten is a career invcstigator of the Swedish Heart-Lung Foundation.
References Koss K. Glomset JA. Atherosclerosis and the arterial smooth muscle cell. Sciericc! 1973: 180: 1332-9. Koss K. The pathogenesis of atherosclerosis--an update. N I h g l / Med 1986: 314: 488-97. Nilsson J. Growth factors and the pathogenesis of atherosclerosis. Atlrerosclerosis 1986: 6 2 : 185-99. Koss K. Kaines EW. Rowen-Pope Ill7. The biology of platelet derived growth factor. Cell 1986: 4 6 : 155-69. Gersuk GM. Carnie1 K. Pattengale PK. Platelet derived growth fiictor concentrations in platelet poor plasma and urine from patients from inyeloproliferative disorders. Blood 1989 : 74: 2 3 30-4. Heniniendinger S. Neuniann M-K. 13eretx A et rtl. Mitogenic activity on human arterial smooth muscle cells is increased in the plasma of patients undergoing hemodialysis with cuprophane membranes. Neplirori 1989: 53: 147-51. DiCorleto PE. Bowen-Pope I F . Cultured endothelial cells produce ir platelet-derived growth factor-like protein. Proc Nntl AcndSci USA 1983: 80: 1919-23.
403
8 Shimokado K. Raines EW. Madtes DK. Barrett TR. Benditt El’, Koss K. A significant part of the macrophage-derived growth factor consists of at least two forms of PDGF. Cell 1985 : 4 3 : 277-86. 9 Nilsson J. Sjolund M. Palmberg M. Thyberg J. Heldin C-H. Arterial smooth muscle cells in primary culture produce a platelet derived growth factor-like protein. Proc Natl Acad Sci USA 1985: 82: 4418-22. 1 0 Wilcox JN, Smith KM, Williams LT. Schwartx SM. Gordon I). Platelet derived growth factor nKNA detection in human atherosclerotic plaques by in-situ hybridization. / C h i Invest 1988: 8 2 : 1 1 3 4 4 3 . 1 1 Ross K. Masuda J, Raines EW et rtl. Localization of PI>CF-B protein in macrophages in all phases of atherogenesis. Science 1990: 248: 1009-1 2. 12 Winkles JA. Friesel K. Burgess WH. Howk K. Mehlman T. Human vascular smooth muscle cells both express and respond to heparin-binding growth factor I . Proc Nut1 Acad Sci U S A 1987: 8 4 : 7124-8. 13 Cospadorowicz D. Ferrara N. Haaparanta 7’. Ncufeld C. Basic libroblast growth factor: expression in cultured bovine vascular smooth muscle cells. Eur / Cell Biol 1988 : 4 6 : 144-5 I . 14 Burgess WH. Maciag T. The heparin-binding family of growth factors. Aririu Rev Bioclierii 1989: 58: 575-606. 15 Klagsbrun M. Edelman EK. Biological and biochemical properties of fibroblast growth factors. Implications for the pathogenesis of atherosclerosis. Arteriosclerosis 1989 : 9 : 269-78. 16 McNeil PL. Muthukrishnan L. Warder E. Il‘Amore P. Growth factors are released by mechanically wounded endothelial cells. / Cell Biol 1989: 109: 811-22. 17 Grosenbaugh DA, Amoss MS. Hood DM, Morgan SJ. Williams ID. Epidermal growth factor-mediated effects on aquine vascular smooth muscle cells. Arn / I’ligsiol 1988: 255: C447-5 1 . 18 Clemmons DK. Van Wyk JJ. Evidence for a functional role of endogenously produced somatomedin-like peptides in the regulation of DNA synthesis in cultured human fibroblasts and porcine smooth muscle cells. / Cliri Invest 1985: 7 5 : 1 91 4-8. 19 Nilsson J. von Euler AM. Dalsgaard C-J. Stimulation of connective tissue cell growth by substance P and substance K. Nature 1985: 315: 61-3. 2 0 Lev-Ran A. Hwang DL. Ahmad B, Bixby H. Immunoreactive epidermal growth factor in serum, plasma platelets and urine in patients on chronic dialysis. Neplrron 1991 : 5 7 : 164-6. 21 Ilaughaday WH. Kotwein P. Insulin-like growth factors I and II. Peptide. messenger ribonucleic acid and gene structures, serum and tissue concentrations. Eiidocr Rev 1989: 10: 68-90. 22 Reynolds WJ, Chiu B. lnman RI). Plasma substance P levels in fibrositis. / Hlieumntol 1988 : 1 5 : 1802-3. 23 Theodorsson-Norheim I?, Norheirn I. Oberg K et nl. Neuropeptide K : a major tackykinin in plasma and tumor tissues from carcinoid patients. Bioclrern Biophys Kes Corrrrnurr 1985: 131: 77-83. 2 4 Nilsson J. Svensson J. Hamsten A. de Faire U. Increased platelet-derived mitogenic activity in plasma of young patients with coronary atherosclerosis. Atlwosclerosis 1986: 61 : 237-43. 25 Carlson K. Lipoprotein fractionation. / Chi Patliol 1973: 5 : 32-7. 26 Noble KP. Electrophoretic separation of plasma lipoproteins in agarose gel. / Lipid Hes 1968: 9 : 693-700.
404
J . NII,SSON et a/.
2 7 Beaumont JL. Carlson LA. Cooper GK. Feifar %. Fredrickson 1)s. Strasscr ‘l. Classilication of hyperlipidaemias and hyperlipoproteinaemias. N i t / / WHO 1970: 43: 891-91 5. 28 Hamsten A. Walldius G . Siramosi A. Dahlen G. de Faire U. Kelationship of angiographically defined coronary artery disease to serum lipoproteins and apolipoproteins in young survivors of myocardial infarction. Circrrlotiori 1986: 73 : 1097-1 1 0 . 29 Koss K. Gloniset 1. The pathogenesis of atherosclerosis. N Err{// / A k r l 1976: 295: 369-77. 3 0 Nilsson J. IIlgue G . Wallin M. Hamsten A. Blombgck M. Correlation between plasma levels of growth factors and von Willebrand factor. Tlrronrb HES 1989: 54: 125-32. 3 1 Clernmons. IIK. Interaction of circulating cell-derived and plasma growth factors in stimulating cultured smooth muscle cell replication. / Cell Ph!piol 1 9 8 4 : 121 : 425-30. 32 Allen KE. l3oxhorn LK. Regulation of skeletal muscle satellite cell proliferation and differentiation by transforming growth factor-beta. insulin-like growth factor- 1, and libroblast growth factor. / Cell IYrgsiol 1989: 138: 31 1-5.
33 Bornfeldt KB. Arnquist HI, Norstedt G. Kegulation of insulinlike growth lictor gene expression in cultured vascular smooth muscle cells. / Eridocririol 1990: 1 2 5 : 381-6. 34 Najean Y . Dassin I:, Vigneron N. Wacquet M. I’latclet survival studies in patients with vascular disease. h r / Cliii / m e s t 1979: 9: 4 6 - 4 . 35 ‘rurpie AG. de Boer AC. Genton E. I’latelct consumption in cardiovascular disease. S‘mi-T/iroriifi Hemost 1982 : 8 : 161-85. 36 Hainsten A. Svensson. J. Walldius G. Sxaniosi A. de Faire U. Shortened niegakaryocyte-platelet regeneration time in young survivors of myocardial infarction. A r r i HerirI / 1985: 110: 1 154-60. 37 Lindncr V. Lappi D. Baird A. Majack K. Keidy M. Kole of basic libroblast growth fiictor in vascular lesion formation. Circ Kes 1991: 6 8 : 106-13, Keceived 21 November 1991. accepted 3 July 1992 Carresporrrlerice: ]an Nilsson. Ikpartnicnt of Medicine. Karolinska Hospital, 13ox 60500. 104 01 Stockholm. Sweden.
Association between high levels of growth factors in plasma and progression of coronary atherosclerosis J. NILSSON*. S. VOLK-JOVINGE*, J. SVENSSON§, C. L A N D O U t , U. D E FAIKE' & A. HAMSTEN* Frorri tlie *Ilcpnrtrrierit of Medicine orrd tlie tDepnrtrrient of Tliorocic Hodiology. Kirrg Gustcc/ V Rrsrurclr Iristiticte. Krrroliriskn Hospitul. arid tlie EjDepartrfreritO/ Cliriical Clicirrisfrq, Ilnridergd Hospitnl. Kuroliriskn Iristitrrte. Stockholirr. Sweden
Abstract. Nilsson J , Volk-Jovinge S. Svensson J. Landou C. de Faire U. Hamsten A (Department of Medicine and Department of Thoracic Radiology, King Gustaf V Kesearch Institute. Karolinska Hospital, and Department of Clinical Chemistry, Danderyd Hospital. Karolinska Institute. Stockholm, Sweden). Association between high levels of growth factors in plasma and progression of coronary atherosclerosis. loiirnul of Internul Medicine 1 9 9 2 : 232: 397-404. Although intimal proliferation of smooth muscle cells (SMC) is recognized as one of the key mechanisms in the development of atherosclerosis, our knowledge of the role of circulating growth factors for SMC in this process is limited. I n the present study the plasma levels of platelet-derived growth factor (PDCF), P-thromboglobulin (P-TG). platelet factor 4 (PF 4) and total growth factor activity were determined in a group of 3 0 young postinfarction patients who had participated in an angiographic study of mechanisms associated with progression of coronary atherosclerosis. Significant correlations were found between the total growth factor activity in plasma and progression ( r = 0.42. I-' llL
H1L2 ~
‘I’G
Chol
‘I’G
Chol
TG
Chol
0.25 -0.21
0.04 0.24
-0.20 -0.46**
-0.14 0.11
-0.2 I -0.25
0.52*
0.04
0.01
0.3 1
0.3h
0.33
Chol = cholesterol, ‘IT = triglycerides. I’artial correlation cocfficients with coronary scores at reangiography used as dependcnt variables and the age of thc patients lirst entered in the regression modcl as ti forced variable. * P < 0.01, **p < 0.05.
402
J . N I L S S O N et a/.
between the growth factor activity in plasma and established risk factors such as LDI, cholesterol concentration, a diagnosis of hypertension or tobacco consumption (data not shown).
Discussion Intimal proliferation of SMC is regarded as one of the key processes in the development of atherosclerosis. Considerable attention has been focused on the possible role of the two growth factors PDGF and FGF in this process. It was initially proposed that proliferation of SMC in the intimal layer of the arterial wall occurred in response to PDGF released from aggregating platelets at sites of endothelial injury [29]. However, recent data from animal experiments indicate that PDGF and FGF released from cells in the vascular wall may be of greater importance [2]. The aim of the present investigation was to determine whether there is any association between the plasma levels of growth factors for SMC and the development of coronary lesions in patients with premature coronary heart disease. The growth factor activity of platelet-poor plasma was assessed by analysing its ability to stimulate DNA synthesis in cultured human arterial SMC. This method provides an estimate of the net effects of growth factors and growth inhibitors present in plasma. but does not allow identification of the nature of the growth-promoting activity. The use of platelet-poor plasma is critical in this analysis, since serum contains large amounts of PDGF released from platelets which under normal conditions do not reach the cells in the vessel wall. Simultaneous analysis of P-TG and PF-4 makes it possible to exclude artefactual release of PDGF from platelets during blood sampling. The results suggest that there is a significant association between the growth factor activity for SMC in plasma and the global severity and rate of progression of coronary atherosclerosis, which is independent of established metabolic and clinical risk factors. This finding is in agreement with the observation of increased levels of plasma growth factors in young survivors of myocardial infarction [24], and supports the view that growth factors may play a role in the development of coronary atherosclerosis. As discussed above, the growth factor activity assay does not allow identification of the nature of the growth-promoting activity. In a n attempt to resolve this problem, the presence of PDGF
in plasma was analysed by radioimmunoassay. Although there was a significant correlation between the levels of PDGF and growth factor activity in plasma, the analysis indicated that less than 2 0 % of the growth factor activity was accounted for by PDGF. In an earlier study 1241, addition of PDGF antibodies inhibited up to 40% of the growth factor activity in plasma of patients with cardiovascular disease. The reason for this discrepancy has yet to be determined. Furthermore, there was no association between the PDGF concentration in plasma and the global severity or rate of progression of coronary atherosclerosis. Assuming that the growth-promoting activity of plasma is due to factors other than PDGF, FGF is one possible candidate. FGF is synthesized in endothelial cells and SMC. but is not normally secreted from these cells. It has been suggested that release of FGF takes place as a result of cell injury 1161. Thus it is possible that FGF is released from perturbed endothelial cells covering atherosclerotic plaques, which would result in an increase in growth factor activity in plasma. Interestingly, earlier studies have demonstrated ii relationship between the plasma concentration of the von Willebrand factor (which has been suggested to be a marker of endothelial injury) and the plasma growth factor activity 1301. IGF-1 is another growth factor normally present in human plasma 121 I. IGF1 is in itself a weak mitogen for SMC, but it may potentiate the mitogenic effect of other growth factors. such as PDGF and FGF [31. 321. The IFG-I gene is expressed in cultured SMC. and its expression is enhanced by exogenous IGF-1, a finding compatible with the existence of an endogenous growth stimulatory loop 1331. Plasma levels of PDGF, P-TG and PF 4 did not correlate with the atherosclerosis scores. In contrast, the level of PDCF was significantly related to the number and severity of distinct stenoses. This association may be due to release of PDGF from mechanically injured platelets. Indeed, several investigators have reported that coronary artery disease is associated with an increase in platelet consumption [34-3 61. The important question remains as to whether the increased plasma level of growth factor for SMC observed in the present investigation is the cause or the result of the disease. The retrospective design of the study makes it impossible to answer this question. Clearly, prospective studies arc needed to resolve this issue. Furthermore. the mechanisms regulating
GKOW‘I’H FACTORS AND CORONARY ATHEROSCLEROSIS
401
‘l’:ible 3. Kelations of plasma growth factor activity and serum lipoprotein lipid concentrations to progression of coronary atherosclerosis ~
~
~
~
~~
lmJ
VISIL
HDL
HIII,,
Growth factor activity Chol
’I’G
Chol
‘I’G
Chol
‘I’G
Chol
0.42*
0.08
0.11
0.02
-0,li
-0.14
0.17
~
Progression of coronary atherosclerosis
0.03
~
Cho = cholesterol. ‘I’G = triglyccrides. I’ertial correlation coefficients with difference in coronary atherosclerosis scores between the first and second angjograms used as dependent variables and tinic between the angiograms first entered in the regression model as a forced variable. * P < 0.05.
W
$
0
.I 4 -E
8
z 5 -m
3-
f
I -
.** a.
2-
*.
n m
f
.
0
5-
Table 4. Relations of the plasma levels of the threc plateletderived proteins 0-TG. I’F 4 and P I X F to global severity of coronary lesions and progression of diffuse atherosclerosis
P-TG I’F 4 PDGF
*.
*.
=*
.*.
(b’
0
10
Stenoses score
Progression of diffuse athcromatosis
-0 08 0 11 -0 10
0 20 0 41 0 40*
-0 26 - 0 04 -0 0 1
Partial correlation coefficients with coronary scores of reangiography and difference in coronary atherosclerosis scores between the first and second angiograms used as dependent variables and the age of the patients and the time between the angiograms. respectively, used as forced variables. * P < 0.05. j- PDGF was determined in 26 patients, and P-TG and PI74 were determined in 24 patients.
0
5
Athcrosclerosis score
15
20
25
30
Growth factor activity (% labelled nuclei) Fig. 1. I’lasniii growth factor activity in relation to (a) global atherosclerosis score and (b) atherosclerosis progression score. The plasma growth ftictor activity is expressed as percentage atrtor;itliographicaily labclled nuclei after exposure of cultured human SMC to medium containing 2 % patient plasma and 2 pCi nil-’ of “H-thymidine for 2 4 h.
quantify platelet release. P-TG and PF 4 are stored together with PDGF in the a-granules of platelets, and their plasma levels reflect the amount of PDGF released from platelets into plasma. The plasma of 14 patients contained no detectable I’DGF (this assay detects PDGP concentrations above 0.5 ng ml-I). The IWGF level in the plasma of the remaining patients varied between 0.7 and 10.2 ng ml-’. There were no associations between the plasma levels of PDGF, p‘I’G and PF 4 and the rate of progression of global athcrosclerosis (Table 4). nor did the plasma levels of
Table 5. Spearman rank correlation coefficicnts between plasma growth factor activity and plasma concentrations of plateletspecific proteinst
Plasma growth factor activity PIIGF
PDGF
P-TG
PF4
0.40*
-0.41
-0.1 3
0.27
0.32
* P < 0.05.
t PDGF was determincd in 26 patients and P-TG and PF4 were determined in 24 patients. the three platelet-derived proteins differ between patients with or without progression or appearance of new stenotic lesions (data not shown). However, the plasma level of PDGP was significantly associated with the number and severity of coronary stenoses at reangiography (Table 4). The growth factor activity in plasma correlated positively with the plasma level of PDGF ( r = 0.40, P < 0.05), and tended to be inversely correlated with the plasma level of P-TG (Table 5). There were no statistically significant associations between the levels of PDGF and P-TG and 1’F 4 (Table 5). No associations were found
GROWTH FACTORS AND CORONARY ATHEROSCLEROSIS
plasma levels of growth factors have to be clarified. However, assuming that the release of growth factors into plasma occurred as a result of existing atherosclerotic lesions, it is still possible that this release per se may contribute to disease progression. Some evidence in support of this possibility has come from studies performed in rats which showed that systemic infusion of FGF markedly increases the replication of intimal SMC following balloon injury of the aorta 13 71. The relationship between plasma growth factor activity and global severity as well as progression of coronary atherosclerosis found in the present study obviously requires confirmation. It is also unknown whether it is present in other age groups, in women and in subjects with premature coronary artery disease but no previous myocardial infarction. Although our observation could have major scientific and clinical implications, much more research is needed before expectations of therapeutic consequences can be raised. At the present time, associations and causations should be clearly distinguished when interpreting the existing data.
Acknowledgements This study was supported by the Swedish Heart-Lung Foundation, the Swedish Medical Research Council (8311. 8691). the Knut and Alice Wallenberg Foundation, King Gustaf V 80th Birthday Fund and thc Nanna Svartz Fund. Dr Hamsten is a career invcstigator of the Swedish Heart-Lung Foundation.
References Koss K. Glomset JA. Atherosclerosis and the arterial smooth muscle cell. Sciericc! 1973: 180: 1332-9. Koss K. The pathogenesis of atherosclerosis--an update. N I h g l / Med 1986: 314: 488-97. Nilsson J. Growth factors and the pathogenesis of atherosclerosis. Atlrerosclerosis 1986: 6 2 : 185-99. Koss K. Kaines EW. Rowen-Pope Ill7. The biology of platelet derived growth factor. Cell 1986: 4 6 : 155-69. Gersuk GM. Carnie1 K. Pattengale PK. Platelet derived growth fiictor concentrations in platelet poor plasma and urine from patients from inyeloproliferative disorders. Blood 1989 : 74: 2 3 30-4. Heniniendinger S. Neuniann M-K. 13eretx A et rtl. Mitogenic activity on human arterial smooth muscle cells is increased in the plasma of patients undergoing hemodialysis with cuprophane membranes. Neplirori 1989: 53: 147-51. DiCorleto PE. Bowen-Pope I F . Cultured endothelial cells produce ir platelet-derived growth factor-like protein. Proc Nntl AcndSci USA 1983: 80: 1919-23.
403
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