Background:
Tissue plasminogen activator (t-PA) is the only treatment approved in the US for acute ischemic stroke. Cell-based therapies are being studied as a new investigational treatment approach for stroke but few studies have assessed the interaction of cell therapies with IV t-PA in an embolic model. Our laboratory has been investigating the therapeutic potential of bone marrow mononuclear cells (MNCs), which have been shown to enhance recovery after acute ischemic stroke and are currently being studied in safety clinical trials.
Methods:
An embolic ischemic stroke model was established by deposition of an autologous blood clot into the internal carotid artery in adult Long Evans rats. IV t-PA (10 mg/kg) was administered at 1 hour after occlusion. Two hours later, 10 million allogeneic MNCs per kilogram or saline were given intravenously (N=12 per group). Hemorrhagic transformation (HT) and blood-brain barrier permeability using Evans Blue were quantified at 3 days after stroke. In an
in vitro
study, astrocytes were isolated from postnatal P1 rats, pre-conditioned by oxygen-glucose deprivation (OGD) for 45 min, and then cultured with MNCs derived from the mother’s bone marrow. MMP-3 was assayed in the media.
Results:
Over 40% (42%) of animals treated with t-PA had HT at 3 days after stroke. The incidence of HT did not differ in the MNC and saline treated groups. However, the ICH scores were significantly reduced in the MNC group (2±1.2) compared to saline controls (3.8±0.8) (
Fig
A,
p
=0.027). BBB permeability was also reduced in the MNC group (0.28±0.07) compared to saline controls (0.6±0.12) (
Fig
B,
p
=0.033). In the
in vitro
study, MMP-3 levels in the medium of cultured pre-conditioned astrocytes (30.6±3.7 ng/ml) were reduced when co-cultured directly with MNCs (23.1±2.0 ng/ml,
p
=0.047) but MMP-3 levels were unchanged when astrocytes and MNCs were co-cultured in transwell (32.8±3.2 ng/ml) (
Fig
C&D).
Conclusion:
We have found for the first time that bone marrow derived MNCs reduce hemorrhagic transformation and blood brain barrier permeability after treatment with IV t-PA for acute ischemic stroke. Our results suggest a novel mechanism in which MNCs may attenuate hemorrhagic risk from t-PA by reducing the release of MMP-3 from astrocytes.
Relation between stroke severity, patient characteristics and CT-perfusion derived blood-brain barrier permeability measurements in acute ischemic stroke