Objective:Human adipose-derived stem cells (hASCs)are a highly attractive source in bone tissue engineering.To generate a luciferase reporter system that could be used to quantitatively and rapidly examine osteogenic differentiation potential of human adipose-derived stem cells (hASCs ) in vitro,and eventually make it possible to monitor the osteogenic differentiation of transplanted cells in vi-vo.Methods:The genomic DNA harboring promotor regions of osteocalcin and DNA sequences encoding luciferase genes were amplified by PCR and cloned into the pLVX-pTRE-puro vector to generate the OCpro-Luc-Puro construct.Then,the OCpro-Luc-Puro construct together with three assistant vectors:pM-DLg/pRRE,pRSV-REV,and pVSVG,were transiently transfected into HEK293T cells followed by viral supernatants collection,filtration and concentration.Next,the hASCs stably expressing luciferase repor-ter gene driven by osteocalcin promotor were created with the lentivirus carrying OCpro-Luc-Puro cassette under puromycin selection.The OCpro-Luc-hASCs were then cultured in the absence or presence of osteo-genic differentiation medium.On the 7th and 1 4th days,after osteogenic induction,cellular extracts were collected and analyzed by luciferase reporter assay.Meanwhile,alizarin red staining and quantification as well as quantitative reverse transcription PCR (qRT-PCR)analysis of osteogenic associated genes osteo-calcin (OC),runt-related transcription factor 2 (Runx2)and alkaline phosphatase (ALP)were used to assess the osteogenic differentiation ability of OCpro-Luc-hASCs.Results:OCpro-Luc-Puro plasmid and OCpro-Luc-hASCs were successfully generated.On the 7th and 1 4th days after osteogenic induction,the luciferase activity of the cellular extracts from OCpro-Luc-hASCs was dramatically increased.Consistently, the extracellular matrix mineralization,as shown by Alizarin red S (ARS)staining and quantification was also markedly intensified and a marked increase of the mRNA expression levels of OC,Runx2 and ALP, although to variable extent,was observed upon osteogenic differentiation.These results indicated that the observations from traditional experiments examining hASCs osteogenic differentiation were largely in agreement with that of our luciferase reporter assay in OCpro-Luc-hASCs.Conclusion:We established a luciferase reporter system that could be used to rapidly,quantitatively and specifically determine osteo-genic differentiation ability of hASCs.Comparing with the traditional time-consuming methods,the system we generated here was highly effective.This system not only can be used to examine ostogenic differentia-tion of hASCs in a high throughput manner,but also provides a way to monitor ostogenic differentiation of cells in vivo.

Objective:To explore the effect of ubiquitin-specific protease 42(USP42)on osteogenic differentiation of human adipose-derived stem cells(hASCs)in vivo and in vitro.Methods:A combina-tion of experiments was carried out with genetic depletion of USP42 using a lentiviral strategy.Alkaline phosphatase(ALP)staining and quantification,alizarin red S(ARS)staining and quantification were used to determine the osteogenic differentiation ability of hASCs under osteogenic induction between the experimental group(knockdown group and overexpression group)and the control group.Quantitative re-verse transcription PCR(qRT-PCR)was used to detect the expression levels of osteogenesis related genes in the experimental group and control group,and Western blotting was used to detect the expression levels of osteogenesis related proteins in the experimental group and control group.Nude mice ectopic im-plantation experiment was used to evaluate the effect of USP42 on the osteogenic differentiation of hASCs in vivo.Results:The mRNA and protein expressions of USP42 in knockdown group were significantly lower than those in control group,and those in overexpression group were significantly higher than those in control group.After 7 days of osteogenic induction,the ALP activity in the knockdown group was sig-nificantly higher than that in the control group,and ALP activity in overexpression group was significantly lower than that in control group.After 14 days of osteogenic induction,ARS staining was significantly deeper in the knockdown group than in the control group,and significantly lighter in overexpression group than in the control group.The results of qRT-PCR showed that the mRNA expression levels of ALP,os-terix(OSX)and collagen type Ⅰ(COL Ⅰ)in the knockdown group were significantly higher than those in the control group after 14 days of osteogenic induction,and those in overexpression group were signifi-cantly lower than those in control group.The results of Western blotting showed that the expression levels of runt-related transcription factor 2(RUNX2),OSX and COL Ⅰ in the knockout group were significant-ly higher than those in the control group at 14 days after osteogenic induction,while the expression levels of RUNX2,OSX and COL Ⅰ in the overexpression group were significantly lower than those in the control group.Hematoxylin-eosin staining of subcutaneous grafts in nude mice showed that the percentage of osteoid area in the knockdown group was significantly higher than that in the control group.Conclusion:Knockdown of USP42 can significantly promote the osteogenic differentiation of hASCs in vitro and in vi-vo,and overexpression of USP42 significantly inhibits in vivo osteogenic differentiation of hASCs,and USP42 can provide a potential therapeutic target for bone tissue engineering.