Brain tissue damage and regeneration monitored by ?-amyloid precursor protein in experimental laser-induced interstitial thermotherapy

Neuropathology and biochemistry of Aβ and its aggregates in Alzheimer's disease

Alzheimer's disease (AD) is characterized by β-amyloid plaques and intraneuronal τ aggregation usually associated with cerebral amyloid angiopathy (CAA). Both β-amyloid plaques and CAA deposits contain fibrillar aggregates of the amyloid β-peptide (Aβ). Aβ plaques and CAA develop first in neocortical areas of preclinical AD patients and, then, expand in a characteristic sequence into further brain regions with end-stage pathology in symptomatic AD patients. Aβ aggregates are not restricted to amyloid plaques and CAA. Soluble and several types of insoluble non-plaque- and non-CAA-associated Aβ aggregates have been described. Amyloid fibrils are products of a complex self-assembly process that involves different types of transient intermediates. Amongst these intermediate species are protofibrils and oligomers. Different variants of Aβ peptides may result from alternative processing or from mutations that lead to rare forms of familial AD. These variants can exhibit different self-assembly and aggregation properties. In addition, several post-translational modifications of Aβ have been described that result, for example, in the production of N-terminal truncated Aβ with pyroglutamate modification at position 3 (AβN3pE) or of Aβ phosphorylated at serine 8 (pSer8Aβ). Both AβN3pE and pSer8Aβ show enhanced aggregation into oligomers and fibrils. However, the earliest detectable soluble and insoluble Aβ aggregates in the human brain exhibit non-modified Aβ, whereas AβN3pE and pSer8Aβ are detected in later stages. This finding indicates the existence of different biochemical stages of Aβ aggregate maturation with pSer8Aβ being related mainly to cases with symptomatic AD. The conversion from preclinical to symptomatic AD could thereby be related to combined effects of increased Aβ concentration, maturation of aggregates and spread of deposits into additional brain regions. Thus, the inhibition of Aβ aggregation and maturation before entering the symptomatic stage of the disease as indicated by the accumulation of pSer8Aβ may represent an attractive treatment strategy for preventing disease progression.

Effects of laser-induced thermotherapy (LITT) on proliferation and apoptosis of glioma cells in rat brain transplantation tumors

BACKGROUND AND OBJECTIVES

Laser-induced thermotherapy (LITT) is an approach to the treatment of brain tumors especially in poorly accessible regions. Its clinical applicability with tumor cell destruction has been shown in several studies. However, no data are known about specific effects on tumors cells due to LITT in the time course of the lesion.

STUDY DESIGN/MATERIALS AND METHODS

LITT was performed in adult Lewis rats with implanted glioma cells in the brain using a standard exposure of 3 W for 30 seconds. Before and following LITT, neoplastic lesions were monitored by MRI. Proliferation of implanted cells and gliosis were assessed by several histological techniques and immunohistochemistry. Apoptosis was detected by TUNEL staining.

RESULTS

Our experiments show a destruction of neoplastic cells by LITT but surviving tumor cells at the margin of the lesion. Apoptosis was detected following LITT restricted to residual neoplastic cells. Marginal survival of tumor cells lead to a secondary outgrowth into the necrotic lesion adjacent to sprouting capillaries.

CONCLUSIONS

LITT is a suitable technique for the treatment of brain neoplasms. However, further investigations are necessary to prevent tumor recurrences after LITT.