CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 1, January/February 2013
290
AFRICA
into the function of this protein. However, myosin-binding protein H
(MyBPH) is another member of the myosin-binding protein family,
located within this region, of which very little is known. Given the
sequence homology and similarity in structure between MyBPC and
MyBPH, we proposed that MyBPH may play critical roles in the
cardiac sarcomere and possibly in HCM pathogenesis.
Methods:
The present study reports the identification and verifica-
tion of interacting partners of MyBPH with the aim of identifying the
role of this protein in the sarcomere using yeast two-hybrid (Y2H)
analysis.
Results:
Twelve interacting partners were identified, of which three
[SUMO-conjugating enzyme UBC9, alpha cardiac actin (ACTC),
and myosin 7 (Myh7)] were considered putative physiological
interactors based on the plausibility of the interactions as assessed
in silico
. Putative interactors UBC9, ACTC and Myh7 proved to
co-localise with MYBPH in differentiated rat cardiomyocyte cells.
Furthermore, co-immunoprecipitation confirmed the interaction
between MYBPH and UBC9, ACTC1 and MYH7.
Conclusion:
The results of this study provide important clues to the
function of MyBPH and, in so doing, improve our knowledge and
understanding of this protein’s role in the cardiac sarcomere.
1627: GLUCOCORTICOID-INDUCED CARDIOPROTEC-
TION: A NOVEL ROLE FOR AUTOPHAGY?
Anna-Mart Engelbrecht
1
, Ben Loos
2
1
Department of Physiological Sciences, Stellenbosch University,
South Africa
2
Dept of Physiological Sciences, Stellenbosch University, South
Africa
Ischaemic heart disease is a leading cause of death worldwide,
therefore better treatment or prevention of ischaemia–reperfusion
(I/R)-induced stress in the heart necessitates a better understanding
of the molecular pathways and mechanisms of cell death. The well-
established anti-inflammatory and immunosuppressive properties of
glucocorticoids have led to their investigation as possible therapeutic
agents to reduce ischaemia–reperfusion-induced stress in the heart.
However, influences of glucocorticoids on cardiovascular disease and
cell death are complex and often contradictory. I/R-induced stress
leads to three types of cell death, which include apoptosis, autophagy
and necrosis. Although autophagy is foremost a survival mechanism
activated during cellular stress, it can also lead to cell death under
certain conditions. Many signalling pathways interlink with the
autophagic machinery and are activated during I/R-induced stress in
the heart, such as the mitogen-activated protein kinase family, which
include p38-MAPK. These kinases are subsequently dephosphoryl-
ated by appropriate phosphatases. MAPK phosphatase-1 (MKP-1), a
dual specificity phosphatase, inactivates the MAPKs by dephospho-
rylating specific Thr/Tyr residues. Up-regulation of MKP-1 during
I/R-induced stress in the heart has been shown to be cardioprotective,
however, little information exists regarding the role of autophagy in
GC-induced protection in the heart. Therefore, the aim of this study
is to describe some of the major signalling pathways activated during
I/R-induced stress and the potential role of autophagy in GC-induced
cardioprotection. By dissecting out the roles of autophagy and gluco-
corticoids with regard to shared metabolic effects and signalling
pathways in cardiac injury, it is hoped to provide a framework for
improved treatment of cardiovascular disease.
1704: DIFFERENTIATING TRANSMURAL FROM TRANS-
ANASTOMOTIC
GRAFT
ENDOTHELIALISATION
THROUGH AN ISOLATION LOOP-GRAFT MODEL
Tim Pennel
1,2
, Peter Zilla
1,2
, Deon Bezuidenhout
2
1
Christian Barnard Department of Cardiothoracic Surgery, University
of Cape Town, South Africa
2
Cardiovascular Research Unit, University of Cape Town, South
Africa
Background:
The absence of a physiological intima is the primary
reason for low patency in small to medium-sized synthetic vascular
conduits. Despite incomplete endothelial surface coverage by trans-
anastomotic outgrowth, vascular graft models have yet to distinguish
this form of healing from trans-mural capillary sprouting. We have
developed an isolation loop-graft model that clearly separates these
distinctly different events.
Methods:
Trans-anastomotic outgrowth was measured by implanting
expanded polytetrafluoroethylene (ePTFE; ID 1.7 mm, IND 15–25
μ
m) for 2.4 and six weeks (
n
=
6 per time point) in the abdominal
aorta of Wistar rats. High-porosity polyurethane (PU; ID 1.7 mm,
150-
μ
m pore) grafts were then interposed between the ePTFE for
two, four, six and eight weeks (
n
=
6 per time point). Looping the
interposition grafts increased their length to 8 cm and they were
implanted for six, eight, 12 and 24 weeks (
n
=
8 per time point).
Grafts were analysed by light, immunefluorescence (CD31) and
scanning electron microscopy. Endothelialisation was expressed as
maximal outgrowth (I
max
) and segment graft coverage (GSE).
Results:
Six-week proximal and distal trans-anastomotic growth
rate did not differ (I
max
=
0.3
±
0.3 vs 0.3
±
0.2 mm/week, NS). The
composite straight-graft ePTFE zones were too short to isolate trans-
mural ingrowth; only 8% of the grafts had mid-graft endothelial
coverage without trans-anastomotic breach. All six- and eight-week
straight composite grafts had trans-anastomotic encroachment. This
outgrowth edge never traversed the endothelium-free isolation zone
in the loop grafts (23.6
±
10.1 mm at 6 weeks and 10.5
±
45.7
mm at 24 weeks), which separated it from trans-mural mid-graft
endothelium. Trans-mural mid-graft endothelialisation reached pre-
confluence by six weeks (GSE
=
55
±
45%) and confluence between
week 12 and 24 (GSE
=
95.0
±
10.0% and 84.0
±
30.13%). The
sub-intimal thickness stayed constant with a non-significant trend
towards regression (91.8
±
93.9 mm vs 71.4
±
59.4 mm at six and 24
weeks, respectively; NS).
Conclusion:
Trans-mural endothelialisation can be clearly distin-
guished from trans-anastomotic outgrowth in a high-throughput rat
model. A looped interposition-graft model provides sufficient isola-
tion length to separate the two events for up to half a year, and does
not result in an increase in intimal hyperplasia.
