Background and Purpose The chronological development and natural history of cerebral aneurysms (CA) remains incompletely understood. We used 14C birth dating of a main constituent of CAs, i.e. collagen type I, as an indicator for biosynthesis and turnover of collagen in CAs in relation to human cerebral arteries to further investigate this. Methods Forty-six ruptured and unruptured CA samples from 43 patients as well 10 cadaveric human cerebral arteries were obtained. The age of collagen, extracted and purified from excised CAs, was estimated using 14C birth dating and correlated with CA and patient characteristics, including the history of risk factors associated with atherosclerosis and potentially aneurysm growth and rupture. Results Nearly all CA samples contained collagen type I which was less than 5 years old, irrespective of patient age, aneurysm size, morphology, or rupture status. However, CAs from patients with a history of risk factors (smoking or hypertension), contained significantly younger collagen than CAs from patients with no risk factors (mean 1.6±1.2 years versus 3.9±3.3 years, respectively, p= 0.012). CAs and cerebral arteries did not share one dominant structural protein, such as collagen type I, which would allow comparison of their collagen turnover. Conclusions The abundant amount of relatively young collagen type I in CAs suggests that there is on-going collagen remodeling in aneurysms, which is significantly more rapid in patients with risk factors. These findings challenge the concept that cerebral aneurysms are present for decades and that they undergo only sporadic episodes of structural change.

Age estimation based on aspartic acid racemization (AAR) has been applied successfully to various tissues. For routine uses, AAR is analyzed in dentine. For cases in which teeth are unavailable, analyzing AAR in purified elastin has been shown to be an alternative method. The suitability of elastic cartilage from the epiglottis as an elastin source for age estimation based on AAR was tested. A total of 65 tissue samples (cartilage) of epiglottis and 45 samples of elastin purified from the elastic cartilage of epiglottis samples were analyzed. While the D-aspartic acid content of total tissue samples increased with age only slowly, its increase with age in purified elastin samples was similar to that in purified elastin from other tissues. The relationship between the D-aspartic acid content and age was shown to be close enough for age estimation based on AAR in purified elastin from the elastic cartilage of the epiglottis, provided a sufficient quality of elastin purification. Age estimation based on AAR in purified elastin from the epiglottis might serve as a valuable alternative in cases in which other tissues (e.g., teeth) are unavailable.

Age estimation based on racemization of aspartic acid residues (AAR) in permanent proteins has been established in forensic medicine for years. While dentine is the tissue of choice for this molecular method of age estimation, teeth are not always available which leads to the need to identify other suitable tissues. We examined the suitability of total tissue samples of human sclera for the estimation of age at death. Sixty-five samples of scleral tissue were analyzed. The samples were hydrolyzed and after derivatization, the extent of aspartic acid racemization was determined by gas chromatography. The degree of AAR increased with age. In samples from younger individuals, the correlation of age and D-aspartic acid content was closer than in samples from older individuals. The age-dependent racemization in total tissue samples proves that permanent or at least long-living proteins are present in scleral tissue. The correlation of AAR in human sclera and age at death is close enough to serve as basis for age estimation. However, the precision of age estimation by this method is lower than that of age estimation based on the analysis of dentine which is due to molecular inhomogeneities of total tissue samples of sclera. Nevertheless, the approach may serve as a valuable alternative or addition in exceptional cases.