Md. Menger et al., ORIENTATION OF MICROVASCULAR BLOOD-FLOW IN PANCREATIC-ISLET ISOGRAFTS, The Journal of clinical investigation, 93(5), 1994, pp. 2280-2285
There is evidence that intraislet cellular communication and hormone d
elivery within the islets of Langerhans is controlled via capillary pe
rfusion directed from the B cell core to the A/D cell mantle (intraisl
et portal system). To determine whether vascularization of freely tran
splanted islets repeats this ''coreto-mantle'' capillary perfusion, ha
mster islets were isolated by collagenase digestion and transplanted i
nto a skinfold chamber of syngeneic animals (n = 12). 14 d after trans
plantation, the microvasculature of the islet grafts was analyzed by i
n vivo fluorescence microscopy. The capillary glomerulum-like network
of the islet grafts (n = 109) was found supplied by individual arterio
les, which regularly pierced the islet and broke into capillaries with
in the graft (96/109 [88.1%]), resulting in capillary flow directed fr
om the core to the islet's periphery. Only in 13 of 109 islets (11.9%)
arterioles broke into capillaries at the outside margin of the islet
and capillary flow was directed simultaneously to vessels located with
in the core, as well as the periphery of the graft. The islet's capill
ary network was drained by individual venules and intercapillary anast
omoses between the newly formed islet capillaries and the preexisting
capillaries of the host muscle tissue. Immunohistochemical staining re
vealed B cells located within the core, and A and D cells scattered in
the periphery of the islets, indicating reestablishment of sequential
B --> A/D cellular perfusion of the grafts. Thus, freely transplanted
islets develop an intra-islet portal system, similarly to that of pan
creatic islets in situ.