During adipogenic differentiation human mesenchymal stem cells (hMSC) produce collagen type IV. In immunofluorescence staining differentiating hMSCs started to express collagen type IV when Oil Red O-positive fat droplets appeared intracellularly. Quantitative real time-polymerase chain reaction confirmed progressive increase of collagen type IV α1 and α2 mRNA levels over time, 18.6- and 12.2-fold by day 28, respectively, whereas the copy numbers of α3–α6 mRNAs remained rather stable and low. Type IV collagen was in confocal laser scanning microscopy seen around adipocytes, where also laminins and nidogen were found, suggesting pericellular deposition of all key components of the fully developed basement membrane. Immunofluorescence staining of matrix metalloproteinase-2 (MMP-2, 72 kD type IV collagenase, gelatinase A) and MMP-9 (92 kD type IV collagenase, gelatinase B) disclosed only faint staining of MSCs, but MMP-9 was strongly induced during adipogenesis, whereas MSC supernatants disclosed in zymography pro-MMP-2 and faint pro-MMP-9 bands, which increased over time, with partial conversion of pro-MMP-2 to its active 62 kD form. Differentiation was associated with increasing membrane type 1-MMP/MMP-14 and tissue inhibitor of metalloproteinase-2 (TIMP-2) staining, which may enable participation of type IV collagenases in basement membrane remodelling via ternary MT1-MMP/TIMP-2/MMP-2 or −9 complexes, focalizing the fully active enzyme to the cell surface. MMP-9, which increased more in immunofluorescence staining, was perhaps preferentially bound to cell surface and/or remodelling adipocyte basement membrane. These results suggest that upon MSC-adipocyte differentiation collagen type IV synthesis and remodelling become necessary when intracellular accumulation of fat necessitates a dynamically supporting and instructive, partly denatured adipogenic pericellular type IV collagen scaffold.

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Background The development of modern medicine has resulted in changes in the predisposing conditions, clinical picture, treatment and results of treatment of intracranial abscesses. This study sought to evaluate these changes in a hospital district. Methods A retrospective analysis of the clinical data of all patients treated due to intracranial abscesses at a tertiary referral centre, between 1970-2012. Results The total number of intracranial abscesses was 166. The incidence of intracranial abscesses was 0.33/100 000/year (2000-2012). The most common predisposing conditions were infection of the ear-, nose- and throat region (22%), odontogenic infection (15%) and cardiac anomaly (13%). Lately (2000-2012), infections of the ear-, nose- and throat region (15%) and cardiac anomalies (5%) have become less common, whereas odontogenic infections (32%) have become more common. The most common pathogens belong to Streptococcus spp (42%), Fusobacteriae (14%), Actinomycetales (8%) and Staphylococcus spp (8%). Most patients (66%) experienced a favourable recovery; the proportion of patients with favourable outcome enabling return to prior occupation rose over time, from 12% in 1970-1989 to 24% in 1990-2012. Conclusions The predisposing conditions for intracranial abscesses have changed markedly within the study period. Odontogenic infections have become a common predisposing condition, whereas infections of the ear-, nose- and throat region and cardiac malformations are nowadays less common as predisposing conditions compared to at the beginning of the study period. The proportion of patients with favourable outcome enabling return to prior occupation seems to have increased with time.